In this study, a new, simple, fast and inexpensive method as an alternative to visible spectrophotometry is developed. In this method the cells containing the sample solution were scanned with a scanner, then the color of each cell was analyzed with software written in visual basic (VB 6) media to red, green and blue values. The cells were built by creating holes in the Plexiglas sheet. The dimensions of identical cells were examined by Cr (III) solution with known concentrations. The validity of this new method was studied by determination of dopamine (DA) without using any other reagent. The parameters which affect the system were optimized. The comparison between the current and traditional UV-Vis spectrophotometry methods was studied and the results revealed similar trends in both methods. The developed method was successfully applied to the determination of dopamine in serum and urine without using any pretreatment. Finally comparing the results obtained in the developed method showed that microwave irradiation of the solution can decrease the experimental time, increase sensitivity and improve the limit of detection.
A method for determination of hydrazine is described. The sensor was constructed by immobilizing a reagent on TLC (Thin Layer Chromatography) paper. This procedure is based on chromogenic reaction of hydrazine with p-(dimethylamino)benzaldehyde (reagent) and formation of red colour product followed by scanner-based detection. Changes in RGB values of colour spots on TLC strips create a pattern. The obtained pattern was analyzed by MATLAB software. The proposed sensor is linear in concentration range of 10-300 mg mL À1 of hydrazine and has practical detection limit of 0.1 mg mL À1 . Parameters such as pH and concentration of p-(dimethylamino)benzaldehyde were optimized. The proposed sensor was successfully applied for the determination of hydrazine in bovine serum and tap water.
A method for the determination of ascorbic acid in vitamin C tablets based on a very simple paptode design on TLC strips is described. This procedure is based on the reduction of iron(III) with ascorbic acid and the formation of a colorful red complex with immobilized 2,2¢-dipyridyl (dipy) on TLC strips. The linear range of the system was 20 -200 ppm with a detection limit of 1 ppm and a relative standard deviation of 1.5% (n = 28). The parameters, such as pH, concentration of iron(III), concentration of dipy and the volume of dipy per 1 cm 2 of TLC strips, were optimized. The proposed sensor was successfully applied for the determination of ascorbic acid in vitamin C tablets.
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