Spectrophotometric Determination of Hexavalent Chromium in Textiles by Optical Fiber Ultraviolet Spectrophotometry - UV-Vis Spectrophotometry

Determination of Hexavalent Chromium in Textiles by Optical Fiber Ultraviolet Spectrophotometry_Optical Fiber Ultraviolet Spectrophotometry

Keywords: optical fiber, ultraviolet spectrophotometry, hexavalent chromium, UV-1500, analysis instrument, abstract: At present, there are limited requirements for harmful substances in textiles for entry and exit at home and abroad. Hexavalent chromium has great harm to the environment and human health. Therefore, its detection methods are widely concerned, mainly atomic emission spectroscopy, atomic absorption spectroscopy, fluorescence, polarography, chemiluminescence, mass spectrometry, direct spectrophotometry and chromatography. The national standard GB/T17593.3-2006 specifies the spectrophotometric method for the determination of hexavalent chromium in textiles. It is necessary to pour the treated solution into the cuvette before it can be measured. If the cuvette is not cleaned, it will cause secondary pollution. , affecting the test results. In this paper, a new method for the determination of hexavalent chromium in textiles by using optical fibers in an ultraviolet spectrophotometer is proposed. The effects of extraction temperature, extraction time and color development time on the dissolution of hexavalent chromium are investigated. The kinetic equation provides a methodological reference for the determination of hexavalent chromium. 1. Definition of optical fiber and its light transmission principle. Different materials have different angles of refraction for the same wavelength of light, and the same material has different angles of refraction for different wavelengths of light. Using this principle, some light-conducting materials are made into round-shaped optical wires, that is, optical fibers. The refractive index of the core wire and the outer layer of the optical wire is different, and the refractive index is adjusted to allow the light to enter the light. When the wire is used, the light is continuously reflected inside the light wire, and the light is transmitted from the end of the light wire to the end of the light wire, so that the light information can be transmitted from one place to another. 2. The determination of the color development time. Refer to the national standard GB/T17593.3-2006 to determine the spectrophotometric method of hexavalent chromium in textiles, prepare standard solution and experimental reagent, transfer 20mL standard solution with mass concentration of 100μg/L, add 1mL color developer and 1mL phosphoric acid solution The absorbance of the sample solution in 90 minutes was measured by optical fiber using a real-time monitoring method. The results showed that the absorbance value increased step by step from 0 min to 35 min, and the temperature curve in the range of 0 min to 35 min was selected for linear fitting. The fitted regression equation was: A=-2.37×10-4t2 4.29×10-3t 0.0561, After 35 minutes, the absorbance value gradually decreased. Therefore, the color development time of the hexavalent chromium was 35 minutes. 3. Determination of the extraction temperature. Select appropriate textile raw materials, add 50μg / L standard solution and then dry, refer to GB/T17593.3-2006 to process samples, the oscillation temperature is set to 25 ° C, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C, The experiment was carried out at 60 ° C, 70 ° C, and 80 ° C, and the absorbance value was measured. The results showed that the absorbance of the sample liquid was the highest in the range of 35 ° C to 40 ° C. The absorbance was measured at 36 ° C, 37 ° C, 38 ° C and 39 ° C at a temperature of 35 ° C to 40 ° C. It was found that the extraction conditions were mild at 38 ° C, and the absorbance value was the highest and stable. Therefore, the preferred extraction was 38 ° C. temperature. 4. Determination of extraction time. Select appropriate textile raw materials, add 50μg / L standard solution and then dry, refer to the experimental procedure of GB/T17593.3-2006, absorb the absorbance value every 10min in the shaking time 0min ~ 70min. The results showed that the absorbance value increased gradually with the increase of extraction time in the range of 0min~30min, and the extraction gradually became complete. After 30min, the increase of absorbance was not obvious, indicating that the extraction was complete. Therefore, 30 min is chosen as the preferred extraction time. 5. Work curve and recovery experiment. 20 mL of different concentrations of chromium (VI) solution were separately removed, and the absorbance at 540 nm was tested according to the selected optimal conditions. A standard curve is drawn by plotting the absorbance value against the chromium (VI) mass concentration. The mass concentration of chromium (VI) showed a good linear relationship in the range of 10μg/L～100μg/L. The regression equation was A=8.5×10-4C, and the linear correlation coefficient was R=0.9992. Samples of polyester, cotton and chemical fiber were taken separately for sample blanking and spiked experiments. The recoveries of chromium (VI) in the three textiles ranged from 88.6% to 105.0%, and the relative standard deviation (RSD) was 1.59% to 2.68. %. Conclusion: The determination of chromium (VI) in textiles by optical fiber ultraviolet spectrophotometry has the advantages of high sensitivity, simple operation and avoiding secondary pollution. It is suitable for the determination of chromium (VI) in textiles. The study of its kinetics determined the optimal conditions for the extraction of chromium (VI) from the sample. The establishment of this method has certain guiding significance for the determination of chromium (VI) in textiles. Key words: optical fiber, ultraviolet spectrophotometry, hexavalent chromium, UV-1500, instrumentation