| It is one of requests by green analytical chemistry that replacement of complicated instruments with simple and miniaturized ones during the experiment.It is possible that with small hand-held devices such as digital cameras, mobile phones and other tools of analysis methods to solve some of the quantitative chemical analysis. As the smart phone camera function is not only convenient, but also to quantity determination.It plays the role in the absence of UV.To some extent, the research for the development of portable test has played a positive role in promoting.Because digital imaging colorimetry equipment has the advantages of a simple, flexible operation, more and more person pay a attention to it.This year,there is a systemic review in the journal of Talanta. A typical eample is Kai Johnsson and his colleagues in Swiss Federal Institute of Technology published an application on top of the camera measuring anticancer drug content of the article, in Nature Chemical Biology, they successfully measured the methotrexate concentration 30 patients, and the method was compared with fluorescence polarization immunoassay, consistent with the results obtained show that application of small digital devices often exist broad prospects drug testing in the field.As the smartphone not only has a handy camera function,it can also provide operational environment for a lot of softwares, so the smartphone applications to the field of analytical chemistry more and more attention. In the published articles, the researchers initially analytes using color changes, namely changes in gray value of quantitative detection. Gray is the easiest color analysis mode, it is a series from black to white over color, and it is a measure of brightness of different colors. Some researchers use the RGB color model to analysis. RGB is a mixed color model, which is composed of the three primary colors of red(R), green(G), and blue(B), then the material can be analyzed by RGB values. Some researchers use CMYK, XYZ, LAB, HSV color model measuring analysis, but these measurements in addition to have a certain relationship with the analyte concentration, they will also severely affected by the shooting distance, light intensity and other experimental conditions.To solve this problem, researchers have adopted a box to make the shooting conditions rigorous, but it still can not solve the problem that measurement precision data is bad, and it undermines the convenience of portable tools detection.In order to solve the above problems, this paper draws on the chromatographic quantitative normalization method, we proposed RGB normalization method.It is desirable to make precision measurements can be improved. To verify this idea, this paper used common smartphone tools for the quantitative determination, under the auxiliary of the free software of RGB color picker on mobile, we can make the the color change occuring in special chemical environment to quantitive analysis red, green, and blue values,and these values are associated with the concentration of the compound being measured to achieve the quantitative determination of formaldehyde in the water and clothing, L-cysteine in the compound amino acid(18AA-?). This article is divided into the following four parts:Part 1: Introduction. The digital-camera-based analytical methods were summarized in this section,which involves the camera equipments, photographing conditions, softwares for reading R, G and B from recorded files, compounds analyzed, sample matrixes. This paper discusses the application of smartphones for processing, the experimental operation is simple, rapid, accurate, and finally we compared the actual experimental operation with the method to verify the accuracy of this method.Part 2: A new smart-phone-based method for the determination of formaldehyde in aqueous water was developed. In order to obtain the stable and reliable results, a portable light box was made for photographing sample solution in a glass cuvette. The color change of the sample solution in addition of chromotropic acid and concentrated sulfuric acid was recoded by smart phone, and the R, G and B values were obtained using software. The linear relationship of either individual value of R, G, B or their different algebraic combinations with formaldehyde concentration was respectively examined. A linear relationship was obtained when the concentration of formaldehyde at the range of 0.1-12.5?g/m L. This method was successfully applied to the determination of formaldehyde in lake water and water sample after soaked clothes with a satisfactory recoveries between 80.3% and 120.1%.Part 3: A new smart-phone-based method was developed for the determination of L-cystine. The color change of L-cystine solution was observed when gold nanoparticles(Au NPs) capped with Tween-20 was added. The rapid reaction between the thiol group from L-cystine and Au NPs induced the aggregation of Au NPs and color change of sample solution. Considering stabilization of Au NPs from aggregation during storage and prevention of some other non-covalent bonding with Au NPs, the Au NPs solution was capped with Tween-20 before use. The solution of Au NPs caped with Tween-20 was red, while its color was changed to be blue(or purple) when mixed with L-cystine solution. The linear relationship of either individual value of R, G, B or their different algebraic combinations with formaldehyde concentration was respectively examined. This method has been applied successfully to determine the L-cysteine in the compound amino acids(18AA-?) with recovery is between 81.2% and 127.3%. The coexisting amno acids in compound amino acids(18AA-?) had little interference with the determination of L-cystine other than methionine.Part 4: Summary and Outlook. This part of the smartphone and RGB normalization method of application of the summary and outlook. |
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