Study Of Six Valence Chromium Content In Measurement Environment And Capsules By Using On-line Preconcentration And Optical Fiber Sensing Spectrophotometry

Objective: To establish an on-line enrichment-fiber-optic spectrophotometric method for the determination of hexavalent chromium content in the environment and capsule shells.Methods: Under the alkaline condition,cerium nitrate was used as precipitant,hexavalent chromium was enriched on line with PTFE filter tube,HNO₃ was used as eluant,diphenylcarbazide as color reagent and self-made Pool and fiber optic spectrometer connected flow injection analysis system for the capsule shell hexavalent chromium content determination.The effects of precipitants,eluents,flow rate,enrichment time,concentration of reagent,reaction tube length and coexisting ions were investigated.Results: The optimum experimental conditions were as follows: the concentration of 0.50 mol·L^-1 was the concentration of 0.16 mol·L^-1 diphenylcarbazide,the precipitant was the concentration of 10×10-6mol·L^-1 cerium nitrate,the length of the reaction tube is 1.50 m,the reagent-precipitant injection rate is 2.00 ml · min-1,the time water sample is enriched for 30 minutes,the capsule shell sample is 5 minutes,the soil sample is 5 minutes,Cr?VI?standard solution was diluted to form a standard solution of0.05 to 0.50 ?g·L^-1.The absorbance was measured and the standard curve was drawn.The linear regression equation of water sample is Y = 0.0002 X + 0.0247,R2 = 0.9989 detection limit is 9.77 × 10-3?g·L^-1.The average relative deviation was 1.11%,and the recoveries were 93.50% 103.93%.The standard solution of Cr?VI?was diluted to 0.50 3.50?g·L^-1,and the absorbance was measured and the standard curve was drawn.The linear regression equation was Y = 0.0324 X + 0.0151,R2 = 0.9991,and the detection limit was 76.64×10-3?g·L^-1.The relative deviation was 1.44%,and the recoveries were 94.33% 104.97%.Cr?VI?standard solution was diluted to form a standard solution of 5.0 20.0 ?g·L^-1.The absorbance was measured and the standard curve was drawn.The linear regressionequation of soil samples was Y = 0.0101X-0.0002,R2 = 0.999,and the detection limit was0.70?g·L^-1.The relative deviation was 1.25%,and the recoveries were 95.24% 105.23%.Conclusion: The method of determination of hexavalent chromium is simple,and the sample can be used for direct determination of Cr?VI?in environmental samples and capsules by means of on-line enrichment and interference.