Journal articles: 'Colorimetric calibration'

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Karaimer, Hakki Can, and Rang Nguyen. "A Correspondence-Free Color Chart Design for Color Calibration." London Imaging Meeting 2020, no. 1 (September 29, 2020): 100–104. http://dx.doi.org/10.2352/issn.2694-118x.2020.lim-01.

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Colorimetric calibration computes the necessary color space transformation to map a camera's device-specific color space to a device-independent perceptual color space. Color calibration is most commonly performed by imaging a color rendition chart with a fixed number of color patches with known colorimetric values (e. g., CIE XYZ values). The color space transformation is estimated based on the correspondences between the camera's image and the chart's colors. We present a new approach to colorimetric calibration that does not require explicit color correspondences. Our approach computes a color space transformation by aligning the color distributions of the captured image to the known distribution of a calibration chart containing thousands of colors. We show that a histogram-based colorimetric calibration approach provides results that are onpar with the traditional patch-based method without the need to establish correspondences.

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Hirai, Toshio, and Shinji Kobayashi. "Colorimetric calibration of Davis-Gibson's filters." JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN 70, Appendix (1986): 110. http://dx.doi.org/10.2150/jieij1980.70.appendix_110.

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Schettini, R., B. Barolo, and E. Boldrin. "Colorimetric calibration of color scanners by back-propagation." Pattern Recognition Letters 16, no. 10 (October 1995): 1051–56. http://dx.doi.org/10.1016/0167-8655(95)00037-h.

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Manoocheri, Farshid, Steven W. Brown, and Yoshi Ohno. "21.3: NIST Colorimetric Calibration Facility for Displays — Part 2." SID Symposium Digest of Technical Papers 32, no. 1 (2001): 330. http://dx.doi.org/10.1889/1.1831863.

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Danielis, Alessandro, Massimiliano Guarneri, Massimo Francucci, Mario Ferri De Collibus, Giorgio Fornetti, and Arianna Mencattini. "A Quadratic Model with Nonpolynomial Terms for Remote Colorimetric Calibration of 3D Laser Scanner Data Based on Piecewise Cubic Hermite Polynomials." Mathematical Problems in Engineering 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/606948.

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The processing of intensity data from terrestrial laser scanners has attracted considerable attention in recent years. Accurate calibrated intensity could give added value for laser scanning campaigns, for example, in producing faithful 3D colour models of real targets and classifying easier and more reliable automatic tools. In cultural heritage area, the purely geometric information provided by the vast majority of currently available scanners is not enough for most applications, where indeed accurate colorimetric data is needed. This paper presents a remote calibration method for self-registered RGB colour data provided by a 3D tristimulus laser scanner prototype. Such distinguishing colour information opens new scenarios and problems for remote colorimetry. Using piecewise cubic Hermite polynomials, a quadratic model with nonpolynomial terms for reducing inaccuracies occurring in remote colour measurement is implemented. Colorimetric data recorded by the prototype on certified diffusive targets is processed for generating a remote Lambertian model used for assessing the accuracy of the proposed algorithm. Results concerning laser scanner digitizations of artworks are reported to confirm the effectiveness of the method.

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Shimano, Noriyuki. "Colorimetric Calibration of Video Cameras Using Two Color Constancy Models." Optical Review 5, no. 5 (September 1998): 320–25. http://dx.doi.org/10.1007/s10043-998-0320-5.

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Lee, Raymond L. "Colorimetric calibration of a video digitizing system: Algorithm and applications." Color Research & Application 13, no. 3 (June 1988): 180–86. http://dx.doi.org/10.1002/col.5080130311.

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Paradkar, Rajesh P., and Ronald R. Williams. "Genetic Regression as a Calibration Technique for Solid-Phase Extraction of Dithizone-Metal Chelates." Applied Spectroscopy 50, no. 6 (June 1996): 753–58. http://dx.doi.org/10.1366/0003702963905718.

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The application of genetic regression (GR) to reflectance spectra of a solid-phase colorimetric extraction for the determination of Hg(II) is demonstrated. GR is a technique that combines wavelengths that optimize linear regression using a genetic algorithm. Solid polystyrene (PS) beads with a molecular weight distribution of 125,000–250,000 were impregnated with Hg(II)-dithizonate, filtered, allowed to dry, and packed in quartz cuvettes, and their reflectance spectra were collected. Quantitation with the use of normal calibration methods could not be achieved because of baseline fluctuations which originate in sample packing, presentation to the spectrometer, and particle size. Results indicate that GR can easily compensate for these baseline fluctuations and provide excellent calibrations.

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Pinheiro, Tomás, João Ferrão, Ana C. Marques, Maria J. Oliveira, Nitin M. Batra, Pedro M. F. J. Costa, M. Paula Macedo, Hugo Águas, Rodrigo Martins, and Elvira Fortunato. "Paper-Based In-Situ Gold Nanoparticle Synthesis for Colorimetric, Non-Enzymatic Glucose Level Determination." Nanomaterials 10, no. 10 (October 14, 2020): 2027. http://dx.doi.org/10.3390/nano10102027.

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Due to its properties, paper represents an alternative to perform point-of-care tests for colorimetric determination of glucose levels, providing simple, rapid, and inexpensive means of diagnosis. In this work, we report the development of a novel, rapid, disposable, inexpensive, enzyme-free, and colorimetric paper-based assay for glucose level determination. This sensing strategy is based on the synthesis of gold nanoparticles (AuNPs) by reduction of a gold salt precursor, in which glucose acts simultaneously as reducing and capping agent. This leads to a direct measurement of glucose without any enzymes or depending on the detection of intermediate products as in conventional enzymatic colorimetric methods. Firstly, we modelled the synthesis reaction of AuNPs to determine the optical, morphological, and kinetic properties and their manipulation for glucose sensing, by determining the influence of each of the reaction precursors towards the produced AuNPs, providing a guide for the manipulation of nucleation and growth. The adaptation of this synthesis into the developed paper platform was tested and calibrated using different standard solutions with physiological concentrations of glucose. The response of the colorimetric signals obtained with this paper-based platform showed a linear behavior until 20 mM, required for glycemic control in diabetes, using the Red × Value/Grey feature combination as a calibration metric, to describe the variations in color intensity and hue in the spot test zone. The colorimetric sensor revealed a detection limit of 0.65 mM, depending on calibration metric and sensitivity of 0.013 AU/mM for a linear sensitivity range from 1.25 to 20 mM, with high specificity for the determination of glucose in complex standards with other common reducing interferents and human serum.

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Metheny, Norma A., Emily M. Gunn, Cynthia S. Rubbelke, Terrilynn Fox Quillen, Uthayashanker R. Ezekiel, and Kathleen L. Meert. "Effect of pH Test-Strip Characteristics on Accuracy of Readings." Critical Care Nurse 37, no. 3 (June 1, 2017): 50–58. http://dx.doi.org/10.4037/ccn2017199.

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BACKGROUND Little is known about characteristics of colorimetric pH test strips that are most likely to be associated with accurate interpretations in clinical situations. OBJECTIVES To compare the accuracy of 4 pH test strips with varying characteristics (ie, multiple vs single colorimetric squares per calibration, and differing calibration units [1.0 vs 0.5]). METHODS A convenience sample of 100 upper-level nursing students with normal color vision was recruited to evaluate the accuracy of the test strips. Six buffer solutions (pH range, 3.0 to 6.0) were used during the testing procedure. Each of the 100 participants performed 20 pH tests in random order, providing a total of 2000 readings. The sensitivity and specificity of each test strip was computed. In addition, the degree to which the test strips under- or overestimated the pH values was analyzed using descriptive statistics. RESULTS Our criterion for correct readings was an exact match with the pH buffer solution being evaluated. Although none of the test strips evaluated in our study was 100% accurate at all of the measured pH values, those with multiple squares per pH calibration were clearly superior overall to those with a single test square. CONCLUSIONS Test strips with multiple squares per calibration were associated with greater overall accuracy than test strips with a single square per calibration. However, because variable degrees of error were observed in all of the test strips, use of a pH meter is recommended when precise readings are crucial.

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Pérez-Hernández, Javier, Josep Albero, Xavier Correig, Eduard Llobet, and Emilio Palomares. "Multivariate calibration analysis of colorimetric mercury sensing using a molecular probe." Analytica Chimica Acta 633, no. 2 (February 2009): 173–80. http://dx.doi.org/10.1016/j.aca.2008.11.069.

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Jiménez, Marta, Sabine André, Hans-Joachim Gabius, and Dolores Solı́s. "Calibration of Colorimetric Protein Assays for Quantitation of Plant AB Toxins." Analytical Biochemistry 284, no. 2 (September 2000): 418–20. http://dx.doi.org/10.1006/abio.2000.4721.

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Fry, Michael M., Karl R. Snyder, Karen M. Tobias, Baye G. Williamson, and G. Ann Reed. "Protein C Activity in Dogs: Adaptation of a Commercial Human Colorimetric Assay and Evaluation of Effects of Storage Time and Temperature." Veterinary Medicine International 2011 (2011): 1–6. http://dx.doi.org/10.4061/2011/751849.

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Objectives of this study were to adapt a commercial human protein C (PC) colorimetric assay for use in dogs and to investigate effects of various storage conditions. The human assay was modified by using pooled canine plasma for calibration and by increasing the activation time. PC activity was measured in fresh canine plasma and in plasma stored under various conditions. PC activity of some stored samples was significantly different from that of fresh plasma; however, differences were small. No difference was detected in samples stored under similar conditions but analyzed in different laboratories using similar methodology. Results of this study indicate that the human colorimetric assay is suitable for canine samples if pooled canine plasma is used for calibration, that Clinical and Laboratory Standards Institute sample storage guidelines developed for testing in humans are appropriate for dogs, and that comparisons of results from laboratories using similar methodology are legitimate.

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Cugmas, Blaž, and Eva Štruc. "Accuracy of an Affordable Smartphone-Based Teledermoscopy System for Color Measurements in Canine Skin." Sensors 20, no. 21 (October 31, 2020): 6234. http://dx.doi.org/10.3390/s20216234.

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Quality smartphone cameras and affordable dermatoscopes have enabled teledermoscopy to become a popular medical and veterinary tool for analyzing skin lesions such as melanoma and erythema. However, smartphones acquire images in an unknown RGB color space, which prevents a standardized colorimetric skin analysis. In this work, we supplemented a typical veterinary teledermoscopy system with a conventional color calibration procedure, and we studied two mid-priced smartphones in evaluating native and erythematous canine skin color. In a laboratory setting with the ColorChecker, the teledermoscopy system reached CIELAB-based color differences ΔE of 1.8–6.6 (CIE76) and 1.1–4.5 (CIE94). Intra- and inter-smartphone variability resulted in the color differences (CIE76) of 0.1, and 2.0–3.9, depending on the selected color range. Preliminary clinical measurements showed that canine skin is less red and yellow (lower a* and b* for ΔE of 10.7) than standard Caucasian human skin. Estimating the severity of skin erythema with an erythema index led to errors between 0.5–3%. After constructing a color calibration model for each smartphone, we expedited clinical measurements without losing colorimetric accuracy by introducing a simple image normalization on a white standard. To conclude, the calibrated teledermoscopy system is fast and accurate enough for various colorimetric applications in veterinary dermatology.

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Al-Latteef, Bilal Majeed Abdulridha. "https://www.webology.org/issue.php?volume=1&issue=46&page=3." Webology 17, no. 2 (December 21, 2020): 296–307. http://dx.doi.org/10.14704/web/v17i2/web17032.

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The remarkable development of digital photography has been possible thanks to joint ad-vances in computer science and photography processing and retouching software. The scien-tific use of photography is now possible as long as its intrinsic limits are comprehended, par-ticularly in the very specific time-limited structure of clinical trials. We list the two main limi-tations inherent to this method: geometrical calibration and colorimetric calibration. These li-mitations are illustrated by numerous images used in our practice in Besancon during the last decade.

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Mendes, João, Luís Coelho, André Rocha, Carlos Pereira, Barna Kovacs, Pedro Jorge, and Maria Teresa Borges. "Colorimetric Fiber Optic Based Probe for Real-Time Monitoring of Dissolved CO2 in Aquaculture Systems." Proceedings 15, no. 1 (July 5, 2019): 5. http://dx.doi.org/10.3390/proceedings2019015005.

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Dissolved carbon dioxide (dCO2) evaluation is very important in many different fields. In this work, a new, integrated, colorimetric-optical fiber-based system for dCO2 monitoring in aquaculture industry was developed. The sensing chemistry is based on colorimetric changes of the used indicator—poly p-nitrophenol (pNPh)—in contact with CO2. Preliminary tests were done in a laboratory environment (calibration) and in a laboratory Recirculating Aquaculture System (RAS) with controlled CO2 injection. The results have shown the suitability of the new sensor for assessing dCO2 dynamics in RAS and its fast detection of low dCO2 concentrations in an appropriate operation range.

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Vargas, Alejandro P., Francisco Gámez, Javier Roales, Tânia Lopes-Costa, and José M. Pedrosa. "A Paper-Based Ultrasensitive Optical Sensor for the Selective Detection of H2S Vapors." Chemosensors 9, no. 2 (February 19, 2021): 40. http://dx.doi.org/10.3390/chemosensors9020040.

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A selective and inexpensive chemical paper-based sensor for the detection of gaseous H2S is presented. The triggering of the sensing mechanism is based on an arene-derivative dye which undergoes specific reactions in the presence of H2S, allowing for colorimetric analysis. The dye is embedded into a porous cellulose matrix. We passively exposed the paper strips to H2S generated in situ, while the absorbance was monitored via an optic fiber connected to a spectrophotometer. The kinetics of the emerging absorbance at 534 nm constitute the sensor response and maintain a very stable calibration signal in both concentration and time dimensions for quantitative applications. The time and concentration dependence of the calibration function allows the extraction of unusual analytical information that expands the potential comparability with other sensors in the literature, as the limit of detection admissible within a given exposure time. The use of this specific reaction ensures a very high selectivity against saturated vapors of primary interferents and typical volatile compounds, including alkanethiols. The specific performance of the proposed sensor was explicitly compared with other colorimetric alternatives, including standard lead acetate strips. Additionally, the use of a smartphone camera to follow the color change in the sensing reaction was also tested. With this straightforward method, also affordable for miniature photodiode devices, a limit of detection below the ppm scale was reached in both colorimetric approaches.

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Hung, Po-Chieh. "Smooth colorimetric calibration technique utilizing the entire color gamut of CMYK printers." Journal of Electronic Imaging 3, no. 4 (October 1, 1994): 415. http://dx.doi.org/10.1117/12.186294.

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Pu, Pan, Miao Zhang, and Li Nan Zhang. "A Study on Temperature and Time Conditions of Colorimetric Method in Measuring Soil Available Phosphorus." Advanced Materials Research 838-841 (November 2013): 2047–51. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.2047.

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Molybdenum blue colorimetric method is one of the standard methods of detecting soil available phosphorus and is crucial to guide variable fertilization. In practice, however, we find that color-developing temperature and stable time could affect test results. To ensure precision, in this paper we conducted a comprehensive experiment under the temperature range from 10°C to 40°C and time range from 0 to 80 minutes after color reaction and compared the test results in single calibration mode with that in repetitive calibration mode. Eventually we optimized temperature and testing time conditions in the two different calibration modes respectively. Under the optimum conditions we conducted a verification test using 55 soil samples which were collected from main crop-growing regions of China. The test results had a better linear correlation with standard results (R2 = 0.97) and a small mean relative error (MRE = 0.047), which could meet the accuracy requirement of variable fertilization.

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Czarnik-Matusewicz, Henryk W., and Adolf Korniewicz. "Determination of Capsaicin in the Antirheumatical Plasters by near Infrared Reflectance Spectroscopy: A Comparison of Statistical Methods." Journal of Near Infrared Spectroscopy 6, A (January 1998): A181—A184. http://dx.doi.org/10.1255/jnirs.191.

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The evaluation of near infrared (NIR) reflectance spectroscopy as a method for the determination of capsaicin (8-methyl-N-vanillyl-6-nonenamide)—an active ingredient in the antirheumatical plasters was examined. The analytical procedure for determining the capsaicin was carried out by conventional, time-consuming colorimetric method. Spectra of the 76 plaster samples were recorded in reflectance mode at 2 nm intervals in the range 1100–2500 nm using InfraAlyzer 500 (Bran+Luebbe GmbH). A comparison is made between two regression methods, stepwise multiple linear regression (MLR) and partial least squares regression (PLS). MLR and PLS regression were used for calibrations, with the aid of the software SESAME ver. 2.10 (Bran+Luebbe GmbH). The PLS method showed consistently lower standard error of calibration and higher R values with first and second difference equations. The first difference PLS regression equation resulted in standard error of calibration of 0.018 %, with an R of 0.95. Generalizability of both methods for prediction of capsaicin contents on independent data sets is discussed. Prediction accuracy for independent data sets was increased using PLS regression, but was poor for sample sets with laboratory-measured concentration ranges beyond those of the calibration set. The results in this study indicate that NIR technique has a high applicability to quantitative analysis of capsaicin content in antirheumatical plasters.

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Wang, Wei, Wen-Ya Wu, Wei Wang, and Jun-Jie Zhu. "Tree-shaped paper strip for semiquantitative colorimetric detection of protein with self-calibration." Journal of Chromatography A 1217, no. 24 (June 2010): 3896–99. http://dx.doi.org/10.1016/j.chroma.2010.04.017.

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Chapoteau, E., B. P. Czech, W. Zazulak, and A. Kumar. "New reagent for colorimetric assay of calcium in serum." Clinical Chemistry 39, no. 9 (September 1, 1993): 1820–24. http://dx.doi.org/10.1093/clinchem/39.9.1820.

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Abstract We report a new single-reagent colorimetric assay for the determination of calcium in serum. The assay is based on a novel chromogenic tetracarboxylic acid chelating agent. The method has several advantages over the o-cresolphthalein complexone (CPC) method, including improved linearity, better accuracy, increased stability, and lower working pH (9.0). The calibration curve for the assay is linear up to 4 mmol/L. The results for 47 patients' samples correlated well with results obtained with an Instrumentation Laboratory atomic absorption spectrophotometer. The mean (+/- SD) calcium values for the new method were 2.27 +/- 0.06 mmol/L and 2.26 +/- 0.05 mmol/L for the comparison method. The on-system stability of the reagents is 1 week vs 8 h for the CPC method.

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Maekawa, Mitsuyoshi, Shinya Hashizume, Yasunori Touma, Yukiko Imai, Hiroaki Seki, and Yoshikatsu Hifumi. "Development of Portable Color Discrimination for the Visually Impaired and Color Blindness." Journal of Robotics and Mechatronics 16, no. 5 (October 20, 2004): 535–44. http://dx.doi.org/10.20965/jrm.2004.p0535.

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The inability to discriminate color is an ongoing problem for the visually impaired and those with color blindness. We propose a portable color discrimination unit that communicates color information to users in verbal messages and sound. The unit states what color the target is and, by scanning its surface, transmits a continuous musical tone corresponding to color variations in the scanned area. The targetive is to make color patterns and the target layout recognizable, requiring 1) colorimetric stability, 2) translation of colorimetric information into an appropriate color name, and 3) setting of a relationship between color and sound. We propose using automated calibration and developed a colorimetric unit with high environmental robustness. Colorimetric data consists of RGB data, which does not lend itself readily to color discrimination, so we developed a way to convert RGB data to 220 color names. To develop easy-to-remember color-sound correspondence, we propose using the Shepard Tone Method, in which Shepard tones are mapped onto color hues. These are combined so users scan a target and hear a continuous sound and, if necessary, a color name, to recognize the target’s overall color pattern, somewhat akin to how a visually impaired person recognizes a sculpture by touching its surface.

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Kalinichev, Andrey, Maria Peshkova, Nadezhda Pokhvishcheva, and Konstantin Mikhelson. "Ion-Selective Optical Sensors: A New Look at Well-Established Techniques of Signal Acquisition." Proceedings 2, no. 13 (December 7, 2018): 825. http://dx.doi.org/10.3390/proceedings2130825.

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It is demonstrated for the first time that the registration of the optode signal under non-equilibrium conditions reduces analysis time and shifts the sensor working range. The fabrication of optode-like color standards for digital color analysis (DCA) is described, and a multi-parameter color scale for calibration-free sensor arrays is proposed. Advantages and limitations of monochrome and color camera for DCA with colorimetric optodes are discussed.

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Hung, Po-Chieh. "Colorimetric calibration in electronic imaging devices using a look-up-table model and interpolations." Journal of Electronic Imaging 2, no. 1 (January 1, 1993): 53. http://dx.doi.org/10.1117/12.132391.

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Zhu, Wen-Jie, Da-Qian Feng, Meng Chen, Zhi-Dong Chen, Rong Zhu, Hai-Lin Fang, and Wei Wang. "Bienzyme colorimetric detection of glucose with self-calibration based on tree-shaped paper strip." Sensors and Actuators B: Chemical 190 (January 2014): 414–18. http://dx.doi.org/10.1016/j.snb.2013.09.007.

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Petronijevic, Radivoj, Vesna Matekalo-Sverak, Aurelija Spiric, Ilija Vukovic, Jelena Babic, Milan Milijasevic, and Dejana Trbovic. "Chemometric approach in the development of the colorimetric method for the estimation of food colorants in meat products." Chemical Industry 68, no. 6 (2014): 781–91. http://dx.doi.org/10.2298/hemind131204004p.

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The aim of this research was to develop a novel colorimetric method based on mathematical models, by multiple linear regression (MLR), from the CIE L*a*b* measurements and data of the HPLC determination of food colorants. Calibration set of 10 production batches of finely grinded cooked sausage with food colorants added was manufactured in industrial conditions as follows: one control batch and 9 products with various quantities of added food colorants: E120 (3.4, 7.5 and 12.5 mg/kg), E 124 (5.0, 15.0, 25.0 mg/kg) and E 129 (5.0, 15.0, 25.0 mg/kg). The estimation of the added food colorants was assessed by measuring L*, a*, b* parameters of cross-section. The quantification of food colorants was achieved by HPLC-PDA. Food colorants were extracted from meat products using Accelerated Solvent Extraction (ASE). Quantification of food colorants was achieved in the range from 1 to 100 mg / kg, and recovery values were from 76.15% to 107.04%, for E 120, from 97.61% to 101.03%, for E 124 and from 99.91% to 101.67%, for E 129. Correlation of the results obtained using HPLC and colorimetric measuring data was assessed by Multiple Linear Regression (MLR). The results from colorimetric and chromatographic determinations in four experimental batches (three batches with different quantities of food colorants and one control batch) were used for calibration. Coefficients of determination (R2) for linear models in experimental batches were 0.954, for E 124, 0.987, for E 120 and 0.993, for E 129. Correlation functions of food colorant quantities and corresponding L*a*b* values were established. The obtained mathematical models were tested for the estimation of the content of dyes in 21 samples of finely grinded cooked sausages purchased in retail stores. Food colorants were confirmed in 20 samples (95.24 %), and one sample (4.76 %) did not contain any of these compounds. Out of the positive samples, sixteen samples (80.00 %) contained E 120, while four samples (20.00 %) contained E 129. Food colorant E124 was not established in any of the analyzed samples. Colorimetric CIE L*a*b* method might be used during sensory evaluation of meat products for the assessment of the added food colorants.

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Ma, Yurong, Yingyi Zhu, Benzhi Liu, Guixiang Quan, and Liqiang Cui. "Colorimetric Determination of Hypochlorite Based on the Oxidative Leaching of Gold Nanorods." Materials 11, no. 9 (September 6, 2018): 1629. http://dx.doi.org/10.3390/ma11091629.

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Hypochlorite plays a critical role in killing microorganisms in the water. However, it can also cause cardiovascular diseases, neuron degeneration, and cancer to humans. Although traditional methods feature excellent sensitivity and reliability in detecting hypochlorite, the expensive instruments and strict determination conditions have limited their application in environmental analysis to some extent. Thus, it is necessary and urgent to propose a cheap, facile, and quick analytical assay for hypochlorite. This paper proposes a colorimetric assay for hypochlorite utilizing gold nanorods (AuNRs) as the nanoreactor and color reader. The AuNRs were acquired via a reported seed-mediated method. NaClO with strong oxidation property can cause the etching of gold from the longitudinal tips of AuNRs, which could shorten the aspect ratio of AuNRs, decrease the absorption in the UV–Vis spectrum and also induce the solution color changing from red to pale yellow. Thus, according to the solution color change and the absorbance of longitudinal surface plasmon resonance of AuNRs, we established the calibration curve of NaClO within 0.08 μM to 125 μM (∆Abs = 0.0547 + 0.004 CNaClO, R2 = 0.9631). Compared to traditional method, we obtained the conversion formula between the concentration of residual-chlorine in tap water and the concentration of hypochlorite detected by the proposed colorimetric assay, which is Cresidual-chlorine = 0.24 CNaClO. Finally, the real application of the colorimetric assay in tap water was successfully performed, and the accuracy of the colorimetric method can reach from −6.78% to +8.53%.

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Kohzadi, Tayebeh, and Mahmoud Roushani. "Highly sensitive colorimetric determination of malathion using gold nanoparticles." Water Supply 16, no. 5 (March 22, 2016): 1214–20. http://dx.doi.org/10.2166/ws.2016.029.

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A highly sensitive method is presented for the colorimetric determination of malathion using gold nanoparticles (AuNPs). In this approach, the synthesized AuNPs solution was stabilized by the citrate anions as their repulsion protected the AuNPs from aggregation. The synthesized AuNPs were characterized morphologically by using transmission electron microscopy technique. Malathion caps the surface of AuNPs and induces the aggregation of AuNPs in Britton–Robinson buffer solution. The reaction was monitored spectrophotometrically by measuring the decrease in the plasmon resonance band of the AuNPs at 527 nm after 9 min. The effect of reaction variables on the reaction sensitivity was investigated and furthermore, the interference of common ions was effectively avoided. The calibration curve is linear over the concentration range 3.3 × 10−7 to 3.3 × 10−6 mol/L of malathion with good precision and accuracy and the detection limit was down to 1.5 × 10−7 mol/L. The developed approach does not use complex and expensive instruments. The high sensitivity of the proposed method allowed its successful application to wheat and water samples. Thus, the proposed strategy can serve as a powerful method for the rapid diagnosis of malathion in agriculture products.

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Kerven, GL, DG Edwards, CJ Asher, PS Hallman, and S. Kokot. "Aluminum determination in soil solution. 2. Short-term colorimetric procedures for the measurement of inorganic monomeric aluminum in the presence of organic acid ligands." Soil Research 27, no. 1 (1989): 91. http://dx.doi.org/10.1071/sr9890091.

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Colorimetric procedures were developed for the determination of inorganic monomeric aluminium (Al) in the presence of organic ligands including high molecular weight fulvic acids and short chain carboxylic acids. The procedures take advantage of marked differences in reaction rate between the chromogens aluminon and pyrocatechol violet (PCV) and aluminium in either free inorganic forms or organically complexed forms. The aluminon method uses a 30 s reaction and has a working range for total Al concentrations between 20 and 250 PM. The more sensitive PCV method uses a reaction time of 60 s and provides a linear calibration line in the range 0.2-25 �M. Both methods are calibrated by using standard solutions containing known total A1 concentration prepared with varying ratios of inorganic monomeric and organically complexed Al. The determination of Al in soil solution and its fractionation into inorganic monomeric and organically complexed forms requires the measurement of total Al in filtered soil solutions by inductively coupled plasma atomic emission spectroscopy (ICPAES) and the use of one of the short reaction time colorimetric procedures. Limited testing on soil solutions from acid, Al toxic soils showed better agreement between inorganic monomeric Al concentration determined by the new procedures and relative yield data than that obtained by existing colorimetric methods.

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Maiti, Swarnali, Gadadhar Barman, and Jayasree Konar Laha. "Colorimetric Estimation of 3–Mercapto-1, 2-Propanediol by Silver Nanoparticles." Journal of Surface Science and Technology 32, no. 1-2 (July 6, 2016): 45. http://dx.doi.org/10.18311/jsst/2016/6601.

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Interaction of 3 -mercapto-1, 2- propanediol (3MPD) (C3H8O2S, 3MPD) with silver nanoparticles prepared by green method has been studied by electronic absorption spectroscopy and transmission electron microscopy. Here we report the changes in properties of AgNP in presence of biologically relevant molecule 3MPD. The assembly and the aggregation of the AgNP are established using UV-Visible spectra and transmission electron microscopy. The biosynthesized AgNP has been used as colorimetric sensor for detection of 3MPD. A new peak generated at 612 nm due to the self aggregation of silver nanoparticles occurred by the interaction of thiol group present in 3 MPD with AgNP. A calibration curve between the absorbance at 612 nm and the concentration of 3 MPD enabled us to estimate 3MPD present in water in presence of SDS.

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Ribeiro, Paulo Roberto da Silva, Helena Redigolo Pezza, Leonardo Pezza, Liliane Spazzapam Lima, and Matthieu Tubino. "Development and application of a portable instrument for drugs analysis in pharmaceutical preparations." Brazilian Journal of Pharmaceutical Sciences 51, no. 3 (September 2015): 699–708. http://dx.doi.org/10.1590/s1984-82502015000300022.

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This article describes the application and performance of an inexpensive, simple and portable device for colorimetric quantitative determination of drugs in pharmaceutical preparations. The sensor is a light detector resistor (LDR) incorporated into a black PTFE cell and coupled to a low-cost multimeter (Ohmmeter). Quantitative studies were performed with captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems. Calibration curves were obtained by plotting the electrical resistance of the LDR against the concentration of the colored species in the ranges 1.84 × 10-4 to 1.29 × 10-3mol L-1 and 5.04 × 10-4 to 2.52 × 10-3 mol L-1 for captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems, respectively, exhibiting good coefficients of determination. Statistical analysis of the results obtained showed no significant difference between the proposed methodologies and the official reported methods, as evidenced by the t-test and variance ratio at a 95% confidence level. The results of this study demonstrate the applicability of the instrument for simple, accurate, precise, fast,in situ and low-cost colorimetric analysis of drugs in pharmaceutical products.

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Ng, R. H., K. M. Sparks, and B. E. Statland. "Colorimetric Determination of Potassium in Plasma and Serum by Reflectance Photometry with a Dry-Chemistry Reagent." Clinical Chemistry 38, no. 7 (July 1, 1992): 1371–72. http://dx.doi.org/10.1093/clinchem/38.7.1371.

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Abstract We evaluated a colorimetric assay of potassium in plasma and serum with the Boehringer Mannheim Reflotron reflectance photometric analyzer, which is designed for near-patient testing in hospitals and physicians' offices. This potassium method does not require calibration or instrument maintenance by the operator. Analysis of 30 microL of plasma or serum takes approximately 140 s. Within-day imprecision (CV) was 1.0-1.2%. Total CVs over a 1-month period were 1.0-1.4%. Patients' results from the Reflotron correlated well with those from the IL 643 flame photometer and the Beckman Synchron CX3 ion-selective electrode methods. The accuracy of Reflotron values was also verified with Standard Reference Material 956 from the National Institute of Standards and Technology.

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Li, Huanhuan, Suleiman A. Haruna, Wenhui Geng, Wenya Wei, Mengxia Zhang, Qin Ouyang, and Quansheng Chen. "Fabricating a novel colorimetric-bionic sensor coupled multivariate calibration for simultaneous determination of myoglobin proportions in pork." Sensors and Actuators B: Chemical 343 (September 2021): 130181. http://dx.doi.org/10.1016/j.snb.2021.130181.

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Vizárová, Katarína, Izabela Vajová, Naďa Krivoňáková, Radko Tiňo, Zdenko Takáč, Štefan Vodný, and Svetozár Katuščák. "Regression Analysis of Orthogonal, Cylindrical and Multivariable Color Parameters for Colorimetric Surface pH Measurement of Materials." Molecules 26, no. 12 (June 16, 2021): 3682. http://dx.doi.org/10.3390/molecules26123682.

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The surface pH is a critical factor in the quality and longevity of materials and products. Traditional fast colorimetric pH detection-based tests such as water quality control or pregnancy tests, when results are determined by the naked eye, cannot provide quantitative values. Using standard pH papers, paper-printed comparison charts, or colorimetric microfluidic paper-based analytical devices is not suitable for such technological applications and quality management systems (QMSs) where the particular tested material should contain a suitable indicator in situ, in its structure, either before or after the process, the technology or the apparatus that are being tested. This paper describes a method based on the combination of impregnation of a tested material with a pH indicator in situ, its exposure to a process of technology whose impact on pH value is to be tested, colorimetric pH measurement, and approximation of pH value using derived pH characteristic parameters (pH-CPs) based on CIE orthogonal and cylindrical color variables. The hypotheses were experimentally verified using the methyl red pH indicator, impregnating the acid lignin-containing paper, and preparing a calibration sample set with pH in the range 4 to 12 using controlled alkalization. Based on the performed measurements and statistical evaluation, it can be concluded that the best pH-CPs with the highest regression parameters for pH are √∆E, ln (a),√∆H (ab), a/L, h/b and ln (b/a). The experimental results show that the presented method allows a good estimation of pH detection of the material surfaces.

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Keyvanfard, M., and Kh Alizad. "A Spectrophotometric Flow Injection Method for Determination of Ultratrace Amounts of Phenylhydrazine by Its Inhibition Effect on the Reaction of Thionin and Nitrite." Journal of Chemistry 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/258605.

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A simple flow injection colorimetric procedure for determining phenylhydrazine was established. It is based on the reaction of phenylhydrazine in sulfuric acid with thionin and sodium nitrite. Reaction was monitored spectrophotometrically by measuring thionin absorbance atλmax=602 nm. A standard or sample solution was injected into the sulfuric acid stream, which was then merged with sodium nitrite stream and thionin stream. Optimum conditions for determining phenylhydrazine were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 0.05–0.60 μmol L−1, and the detection limit was 0.027 μmol L−1(s/n=3). The proposed method has been satisfactorily applied to the determination of phenylhydrazine in human serum and water samples.

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Morris, H. C., P. D. Overton, J. R. Ramsay, R. S. Campbell, P. M. Hammond, T. Atkinson, and C. P. Price. "Development and validation of an automated, enzyme-mediated colorimetric assay of salicylate in serum." Clinical Chemistry 36, no. 1 (January 1, 1990): 131–35. http://dx.doi.org/10.1093/clinchem/36.1.131.

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Abstract This salicylate-specific assay can be adapted for use with most discrete analyzers, for rapid emergency or routine testing with small serum or plasma sample volumes and a single calibration. The basis of this method is as follows: salicylate monooxygenase (EC 1.14.13.1) converts salicylate to catechol in the presence of NADH; the catechol then reacts with 4-aminophenazone under alkaline conditions, catalyzed by manganese ions, to produce a red dye. Incorporation of an NADH-regenerating system, involving glucose and glucose dehydrogenase, into the enzyme reagent ensures that the working reagent is stable for more than two weeks. The standard curve is linear over the drug concentration range 0 to 5 mmol/L. The CV was less than 4% over 20 days. Results correlated well with those by the Trinder colorimetric method and an HPLC method. We saw no interference by any of 80 drugs we tested at therapeutic concentrations or by endogenous compounds in serum.

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Sutkowski, M., and Ya N. Saukova. "RESEARCH OF DIGITAL CAMERA DYNAMIC RANGE ON THE IMAGING PROCESSING BASIS." Devices and Methods of Measurements 8, no. 3 (September 27, 2017): 271–78. http://dx.doi.org/10.21122/2220-9506-2017-8-3-271-278.

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Digital images provide to determine photometric and colorimetric properties of objects subject to validation all elements of a measuring channel (digital camera, software, display) and solve the problem of their limited dynamic ranges. The aim of the study was to explore the dynamic range of a digital camera for use in photometric and colorimetric measurements.The Laboratory of Photonics at the Institute of Microelectronics and Optoelectronics (Warsaw Technical University, Poland) conducted a comparative experiment to determine the threshold of sensitivity, linearity and range of application the digital camera. Color target sets with certified brightness and chromaticity were created at the terminals and recorded with a digital camera with different exposure times. The authors propose a method to extend the dynamic range of a digital camera for red, green and blue color channel of intensities by pairing the calibration dependencies, and determine the true brightness and color of a point on the object by calculation.Calibration dependencies (triads) of digital camera for red, green and blue color channels intensities were constructed. These dependences allow determining lower and upper bounds of the dynamic range. Each triad has a form of the hysteresis loop. The experiment showed that the accuracy of this method is ± 3–5 %.

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Akrivi, Elli A., Athanasios G. Vlessidis, Dimosthenis L. Giokas, and Nikolaos Kourkoumelis. "Gold-Modified Micellar Composites as Colorimetric Probes for the Determination of Low Molecular Weight Thiols in Biological Fluids Using Consumer Electronic Devices." Applied Sciences 11, no. 6 (March 17, 2021): 2705. http://dx.doi.org/10.3390/app11062705.

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This work describes a new, low-cost and simple-to-use method for the determination of free biothiols in biological fluids. The developed method utilizes the interaction of biothiols with gold ions, previously anchored on micellar assemblies through electrostatic interactions with the hydrophilic headgroup of cationic surfactant micelles. Specifically, the reaction of AuCl4− with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) produces an intense orange coloration, due to the ligand substitution reaction of the Br− for Cl− anions, followed by the coordination of the AuBr4− anions on the micelle surface through electrostatic interactions. When biothiols are added to the solution, they complex with the gold ions and disrupt the AuBr4−–CTAB complex, quenching the initial coloration and inducing a decrease in the light absorbance of the solution. Biothiols are assessed by monitoring their color quenching in an RGB color model, using a flatbed scanner operating in transmittance mode as an inexpensive microtiter plate photometer. The method was applied to determine the biothiol content in urine and blood plasma samples, with satisfactory recoveries (i.e., >67.3–123% using external calibration and 103.8–115% using standard addition calibration) and good reproducibility (RSD < 8.4%, n = 3).

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Siani, A. M., G. R. Casale, H. Diémoz, G. Agnesod, M. G. Kimlin, C. A. Lang, and A. Colosimo. "Personal UV exposure on a ski-field at an alpine site." Atmospheric Chemistry and Physics Discussions 8, no. 1 (February 12, 2008): 2745–69. http://dx.doi.org/10.5194/acpd-8-2745-2008.

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Abstract. Mountain sites experience enhanced ambient UV radiation levels due to the concurrent effects of shorter radiation path-length, low aerosol load and high reflectivity of the snow surfaces. This study was encouraged by the possibility to collect data of personal UV exposure in the mountainous areas of Italy, for the first time. Personal UV exposure (expressed in terms of Exposure Ratio, ER) of two groups of volunteers (ski instructors and skiers) at the Alpine site of La Thuile (Valle d'Aosta region, Italy) was assessed using polysulphone dosimetry which was tested in a mountainous snow-covered environment. In addition measurements of biological markers of individual response to UV exposure such as skin colorimetric parameters were carried out. It was found that snow and altitude of study site affect calibration curves of polysulphone dosimeters in comparison to a situation without snow. The median ER, taking into account the whole sample, is 0.60 in winter, with a range of 0.29 to 1.46, and 1.02 in spring, ranging from 0.46 to 1.72. There are no differences in exposures across skiers and instructors in spring while in winter skiers experience lower values. UV exposures are not sensitive to the use of sunscreen across instructor/skier group by day or by seasons or by photo-type. With regard to colorimetric parameters, the main result was that both skiers and instructors had on average significantly lower values of L* and b* after exposure i.e. becoming darker but the inappropriate sunscreen use did not reveal any changes in skin colorimetric parameters except in one spring day. In conclusions UV intensities on the ski-fields are often significantly higher than those on horizontal surfaces. Given the high levels of exposure observed in the present study, dedicated public heath messages on the correct sunscreen use should be adopted.

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Amelin, V. G., Zen Alabden C. Shogah, and D. S. Bolshakov. "Microextraction-colorimetric determination of anionic surfactants in natural and waste waters." Industrial laboratory. Diagnostics of materials 86, no. 12 (December 17, 2020): 5–14. http://dx.doi.org/10.26896/1028-6861-2020-86-12-5-14.

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An eco-friendly, simple, rapid and cheap method for determining anionic surfactants in natural and waste waters by microextraction-colorimetric method has been developed. The essence of the proposed approach consisted in extraction and concentration of analytes in an acidic medium in the form of associates with organic reagents (methylene blue and acridine yellow) by dispersion liquid-liquid microextraction using a mixture of chloroform-acetonitrile as an extracting and dispersing solvent, followed by aggregation of extractant microparticles by centrifugation and subsequent measurements of color characteristics using a smartphone. The values of the basic components of the RGB colorimetric system were used as an analytical signal to calculate the final color: The selection of optimal conditions for microextraction concentration of anionic surfactants from natural waters (the nature of the extracting and dispergating solvents, the volume of the dispergating solvent) was performed for the sodium dodecyl sulfate — methylene blue system. To study the colorimetric characteristics of the prepared extracts, a smartphone «iPhone X» was used as a color-registering device equipped with a specialized software product «RGBer». To minimize the measurement error by fixing the distance to the object under study and lighting conditions, we propose an installation that increases the accuracy and sensitivity of the determination and makes the method more mobile. The total content of the most common components of detergents was determined: sodium dodecyl sulfate, sulfonol, laureth sulfate and disodium laureth-3-sulfosuccinate. The detection limits ranged within 0.01 – 0.02 and 0.05 mg/liter. The range of detectable contents for all analytes was 0.05 – 1.0 mg/liter. For the determined surfactants, the equations of the relationship between the analytical signal and the concentration were obtained. The calibration graphs are linear with coefficients of the approximation reliability ≤0.98. The correctness of the method was tested on samples of natural water using the spike test procedure. The relative standard deviation of the analysis results does not exceed 0.13. The analysis duration is 20 – 30 min.

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Ren, Hang, Tong Li, Rui Ling, Junmin Bi, Chenling Zhang, Zhenglong Wu, and Weidong Qin. "Rational Calibration Strategy for Accurate and Sensitive Colorimetric Detection of Iodide and l-Thyroxine Based on Gold Triangular Nanoplates." ACS Sustainable Chemistry & Engineering 7, no. 18 (August 18, 2019): 15230–37. http://dx.doi.org/10.1021/acssuschemeng.9b02129.

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Jia, Ming-Yan, Qiong-Shui Wu, Hui Li, Yu Zhang, Ya-Feng Guan, and Liang Feng. "The calibration of cellphone camera-based colorimetric sensor array and its application in the determination of glucose in urine." Biosensors and Bioelectronics 74 (December 2015): 1029–37. http://dx.doi.org/10.1016/j.bios.2015.07.072.

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Goedhart, Joachim, Jean-Jacques Bono, and Theodorus W. J. Gadella. "Rapid Colorimetric Quantification of Lipo-chitooligosaccharides from Mesorhizobium loti and Sinorhizobium meliloti." Molecular Plant-Microbe Interactions® 15, no. 9 (September 2002): 859–65. http://dx.doi.org/10.1094/mpmi.2002.15.9.859.

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Nod factors are lipids with a chitinlike headgroup produced by gram-negative Rhizobium bacteria. These lipo-chitooligosaccharides (LCOs) are essential signaling molecules for accomplishing symbiosis between the bacteria and roots of legume plants. Despite their important role in the Rhizobium-legume interaction, no fast and sensitive Nod factor quantification methods exist. Here, we report two different quantification methods. The first is based on the enzymatic hydrolysis of Nod factors to release N-acetylglucosamine (GlcNAc), which can subsequently be quantified. It is shown that the degrading enzyme, glusulase, releases exactly two GlcNAc units per pentameric nodulation factor from Mesorhizobium loti factor, allowing quantification of LCOs from Mesorhizobium loti. The second method is based on a specific type of Nod factors that are sulfated on the reducing GlcNAc, allowing quantification analogous to the quantification of sulfolipids. Here, a two-phase extraction method is used in the presence of methylene blue, which specifically forms an ion pair with sulfated lipids. The blue ion pair partitions into the organic phase, after which the methylene blue signal can be quantified. To enable Nod factor quantification with this method, the organic phase was modified and the partitioning was evaluated using fluorescent and radiolabeled sulfated Nod factors. It is shown that sulfated LCOs can be quantified with this method, using sodium dodecyl sulfate for calibration. Both methods allow Nod factor quantification in parallel enabling a fast and easy detection of nanomole quantities of Nod factors. Accurate Nod factor quantification will be crucial for characterization and cross-comparison of the affinity for Nod factors of newly identified Nod factor binding proteins or putative Nod factor receptors.

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Johnson, Roger N., and John R. Baker. "Accuracy of Devices Used for Self-Monitoring of Blood Glucose." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 35, no. 1 (January 1998): 68–74. http://dx.doi.org/10.1177/000456329803500108.

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We measured the inaccuracy of 17 home blood glucose monitors (two visually read, eight colorimetric and seven amperometric). Using strips from a single batch, blood glucose measurements were performed by three medical laboratory technologists on at least 50 capillary blood specimens from patients attending two diabetes clinics. Additional capillary blood was deproteinized and assayed with hexokinase to give a whole blood glucose result. A dedicated glucose analyser was also studied to cross-validate the methodology. At a mean glucose concentration of about 9 mmol/L, monitor readings differed from the reference results by −5.1 to + 19.5% with three systems failing to meet the American Diabetes Association guideline for total error of less than 15%. This problem would be alleviated by manufacturers adopting a common policy on calibration and on reporting as a plasma or whole blood value.

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OKAMURA, Kei, Hideshi KIMOTO, Takuroh NOGUCHI, Mayumi HATTA, Hiroaki KAWAKAMI, and Takahiko SUZUE. "Colorimetric pH Measurement for Seawater Samples Using a Three Light-Emitting Diodes Detector and a Calibration Method for Temperature Dependence." Analytical Sciences 30, no. 12 (2014): 1135–41. http://dx.doi.org/10.2116/analsci.30.1135.

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Cedeño, E., J. Plazas-Saldaña, F. Gordillo-Delgado, A. Bedoya, and Ernesto Marin. "In-situ monitoring by thermal lens microscopy of a photocatalytic reduction process of hexavalent chromium." Revista Mexicana de Física 64, no. 5 (August 31, 2018): 507. http://dx.doi.org/10.31349/revmexfis.64.507.

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In this work, we describe the application of a micro-spatial thermal lens spectroscopy setup (thermal lens microscope, TLM) with coaxial counter-propagating pump and probe laser beams and an integrated passive optical Fabry-Perot to quantify the Cr-VI concentration in water during a photocatalytic reaction in-situ. A series of test samples was analyzed using the 1,5 diphenil carbazide colorimetric method. A calibration curve was obtained by plotting of the TLM signal as a function of the concentration of Cr(VI) in a range between 0 and 10 μg/L (1 μg/L = 1 ppb, part per billion), with a detection limit of 53 ng/L (1 ng/L = 1 ppt, part per trillion). A solution of 10 μg/L Cr(VI) in distillated water was placed into a cell in contact with an iron-incorporated titanium dioxide film, which was previously grown onto a 1 mm thick glass microscope slide by the sol-gel dip-coating technique. The TLM signal was registered as a function of the photocatalysis time measured from the beginning of the process, radiating the film with UV-violet light. The Cr(VI) concentration was determined with the calibration curve and after the first 50 minutes a reduction of 95 % of Cr(VI) was observed, being the chemical reaction kinetic described by a potential time decreasing function.

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Abbas, Ruba F., Ali A. Waheb, Howraa K. Hami, and Neda I. Mahdi. "Smartphone Digital Image Using for Determination of DCH by a Diazotization Reaction." Current Analytical Chemistry 16, no. 8 (October 26, 2020): 988–95. http://dx.doi.org/10.2174/1573411015666191202152544.

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Background: Simple, sensitive, and economic colorimetric device based on a smartphone digital image coupled with Color Grab™ application was developed for DCH drug determination. The method is based on the diazotization reaction of benzocaine with DCH drug to get an orange azo dye. Methods: Variable parameters such as volumes of reagents, the internal walls and ambient light have been analyzed and optimized. From the optimized conditions, a calibration curve was created by the effective intensity (IG) of an orange azo dye, a correlation of determination is 0.999 and limit of detection 0.808 mg/L. Results: The results of the Smartphone method were statistically compared with the reference method using a t-test and found to be a good agreement. Conclusion: This method requires neither solvent extraction and temperature control, also it has achieved an extensive linear range and low limit of detection compared with different methods reported in the literature.

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Almaquer, Francis Eric P., and Jem Valerie D. Perez. "Evaluation of the Colorimetric Performance of Unmodified Citrate-Stabilized Silver Nanoparticles for Copper (II) Sensing in Water." Key Engineering Materials 821 (September 2019): 372–78. http://dx.doi.org/10.4028/www.scientific.net/kem.821.372.

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In this study, the colorimetric performance of unmodified citrate-stabilized silver nanoparticles (cit-AgNP) for Cu2+ detection was investigated. Cit-AgNP was successfully synthesized using the modified Creighton method with sodium borohydride as reducing agent and trisodium citrate as stabilizing agent. The resulting nanoparticle was yellow in color, characteristic of AgNP. The absorbance peak was determined at 400 nm using UV Vis analysis while for morphology, the particles were spherical in shape with an average diameter of 11 nm determined by TEM analysis. In the presence of increasing Cu2+ concentration, the yellow cit-AgNP turned orange and showed decreasing absorbance at 400 nm with simultaneous emergence of additional peak at 450 nm. These changes were attributed to the nanoparticle aggregation confirmed by TEM analysis. A calibration curve generated showed that the absorbance ratio 450/400 nm is directly proportional to Cu2+ concentration from 0 to 40x10-4 M with good linear fit at R2 = 0.9749. The detection and quantification limits were determined to be 6.59x10-4 M and 21.97x10-4 M, respectively. Overall, the study demonstrated the potential of the assay for Cu2+ sensing application.

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Christians, David K., Thomas G. Aspelund, Scott V. Brayton, and Larry L. Roberts. "Sulfuric Acid/Hydrogen Peroxide Digestion and Colorimetric Determination of Phosphorus in Meat and Meat Products: Collaborative Study." Journal of AOAC INTERNATIONAL 74, no. 1 (January 1, 1991): 22–26. http://dx.doi.org/10.1093/jaoac/74.1.22.

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Abstract Seven laboratories participated In a collaborative study of a method for determination of phosphorus in meat and meat products. Samples are digested In sulfuric acid and hydrogen peroxide; digestion Is complete In approximately 10 mln. Phosphorus Is determined by colorimetric analysis of a dilute aliquot of the sample digest. The collaborators analyzed 3 sets of blind duplicate samples from each of 6 classes of meat (U.S. Department of Agriculture classifications): smoked ham, water-added ham, canned ham, pork sausage, cooked sausage, and hamburger. The calibration curve was linear over the range of standard solutions prepared (phosphorus levels from 0.05 to 1.00%); levels in the collaborative study samples ranged from 0.10 to 0.30%. Standard deviations for repeatability (sr) and reproducibility (sR) ranged from 0.004 to 0.012 and 0.007 to 0.014, respectively. Corresponding relative standard deviations (RSDr and RSDR, respectively) ranged from 1.70 to 7.28% and 3.50 to 9.87%. Six laboratories analyzed samples by both the proposed method and AOAC method 24.016 (14th Ed.). One laboratory reported results by the proposed method only. Statistical evaluations Indicated no significant difference between the 2 methods. The method has been adopted official first action by AOAC.

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Journal articles on the topic 'Colorimetric calibration'

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