ABSTRACT
Objective:To establish a hydride generation atomic fluorescence method using ammonium persulfate as the digestion reagent for determination of arsenic in urine (hereinafter referred to as this method).Methods:The collected urine samples with ammonium persulfate were heated and digested on the tubular electric heating automatic control constant temperature digester (60 holes), with 5% hydrochloric acid solution as reaction medium and current carrier and 1.5% potassium borohydride solution as reducing agent. Arsenic content was determined with a four-channel atomic fluorescence spectrometer. The arsenic standard solution of 0 - 10 μg/L was prepared to determine the standard curve of this method, and the method was evaluated from the detection limit, linear range, correlation coefficient, precision, standard addition recovery experiment, and urine arsenic quality control sample detection. The standard method "Determination of Arsenic in Urine by Hydride Generation Atomic Fluorescence Spectrometry" (WS/T 474-2015, referred to as the standard method) was used for comparison experiments.Results:When the sampling volume was 1 ml, the detection limit of this method (digest with 1 ml 1.5 mol/L ammonium persulfate) was 0.03 μg/L. In the range of arsenic content from 0 - 10 μg/L, the linear relationship between arsenic content and fluorescence intensity was good, and the correlation coefficients ( r) were all 0.999 9. The relative standard deviations( RSD) of the three replicates of urine samples with different concentrations were 1.00%, 0.89% and 0.49%, respectively. Urine arsenic quality control samples were tested, and the test results were all within the range of public values; the overall average recovery was 102.29%, and the recovery range was 92.10% - 108.15%. Compared with the standard method in the determination results of 20 urine samples, the difference was not statistically significant ( t = - 0.40, P > 0.05). Conclusions:The hydride generation atomic fluorescence spectrometry using ammonium persulfate as digestion reagent for the determination of arsenic in urine has the advantages of low detection limit, good precision, high accuracy, small amount of sampling and digestion reagent, simple operation, and less harmful gas generation in sample pretreatment. It is suitable for rapid determination of arsenic in urine in large quantities.
ABSTRACT
Objective To study the effects of sample digestion conditions on measurement results of urinary iodine determined by As(Ⅲ)-Ce4+ catalytic spectrophotometry with ammonium persulfate digestion,and to promote the application of newly revised (the 2012 edition) national standard method for determination of urinary iodine.Methods According to the newly revised national standard method,various digestion conditions,such as ammonium persulfate concentration (0.8-1.3 mol/L,group interval 0.1),digestion instruments (heating block and drying oven) and standing time after digestion(0.5,1.0,2.0,4.0 and 22.0 h),were studied.The samples included 3 standard materials,which were GWB09108k,GWB09109f and GWB09110m containing iodine of (68.2 ± 9.0),(138.0 ± 10.0) and (221.0 ± 10.0) μg/L,and 5 urine samples with iodine concentration of 100-300 μg/L.Results Measurement results among the three groups of 0.9,1.0 and 1.1 mol/L ammonium persulfate digestion fluid showed no significant difference(P ＞ 0.05).The digestive effect showed no significant difference between heating block and drying oven (P ＞ 0.05) except one standard material in low concentration (GBW09108k).After digestion,samples were placed 0.5-22.0 h,the measurement results between groups showed no significant difference (P ＞ 0.05).Conclusions Appropriate concentrations of ammonium persulfate are from 0.9 mol/L to 1.1 mol/L.Heating block is recommended for the digestion,however,when absent,drying oven can be used alternatively.The standing times from 0.5 h to 22 h after digestion have not affected the measurement results.