| BackgroundArsenic is a naturally occurring toxic element,widely distributed in people’s production and living environment.Endemic arsenism,also known as endemic arsenism,is a series of systemic chronic arsenism characterized by skin lesions and canceration caused by the intake of a large amount of inorganic arsenide through diet,drinking water or long-term exposure to arsenic contaminated air in areas where residents live for a long time.Because there are no specific clinical manifestations in the early stage of chronic arsenism,When the typical skin triad(keratosis of the patient’s palms and soles,skin pigmentation and depigmentation)occurs,it has caused great damage to the patient’s body.Therefore,the detection and analysis of arsenic forms in natural water sources and drinking water has become the primary means to prevent chronic arsenic poisoning.The analysis of arsenic forms in the urine of arsenic exposed people can not only explore the metabolic process of arsenic forms in the organism,understand the law of disease occurrence and development and treatment after exposure,but also better monitor the health of people in arsenic exposure risk areas,and systematically and comprehensively observe the disease changes and prevention effects in arsenic disease areas.Nowadays,the determination of arsenic content in samples is usually based on the detection of total arsenic content,but because the toxicity of arsenic largely depends on the existing chemical forms,for the monitoring and research of endemic arsenic poisoning,the detection of total arsenic can not accurately reflect the impact of arsenic exposure on human body,environment,disease occurrence and development,so the analysis and detection of forms become increasingly important.ObjectiveAt present,there is no national standard method for the determination of arsenic speciation in water by HPLC-ICP-MS.In the detection of total arsenic in urine,the sample pre-treatment method and experimental operation process of the national standard method WS/T474-2015 "determination of arsenic in urine by Hydride Generation Atomic Fluorescence Spectrometry" have some shortcomings,such as the large amount of mixed acid digestion reagent in the standard method,the dangerous preparation of reagent,acid mist pollution in the preparation process,unclear digestion time and temperature,and cumbersome operation procedures,In view of the above problems,this paper optimized and improved the method of atomic fluorescence determination of total arsenic in urine,and optimized and explored the national standard method of HPLC-ICP-MS determination of arsenic speciation in water and urine.MethodsStudy 1 Optimization of a method for the determination of arsenic in urine by Hydride Generation Atomic Fluorescence Spectrometry with ammonium persulfate digestion1.The lamp current,auxiliary cathode current,carrier gas flow,reading time and delay time of the detection instrument were adjusted by single factor rotation method.The experimental effect was measured by peak shape,fluorescence response value and other spectral indicators.2.The control variable method was used to optimize the pretreatment technology of atomic fluorescence determination of total arsenic in urine,including the selection of the concentration of digestion solution,the amount of digestion solution added,and the exploration of digestion temperature and time.3.The detection limit,accuracy,precision and spiked recovery of the constructed method were verified by atomic fluorescence spectrometer and high and low value urine arsenic quality control samples.Study 2 optimized the HPLC-ICP-MS method for the determination of arsenic trioxide As(III),arsenic trioxide As(V),monomethyl arsenic(MMA),dimethyl arsenic(DMA),arsenic betaine(As B)in water and urine1.Tune HPLC and inductively coupled plasma mass spectrometry to the optimal analytical state.2.The single factor rotation method was used to optimize the separation conditions of liquid chromatography,including the type,concentration,p H value and flow rate of mobile phase,and the optimal elution and separation conditions were explored.3.Under the optimized optimal experimental conditions,the mixed standard solutions of five arsenic forms were used for methodological validation,including the detection limit,precision,and spiked recovery of the method.The optimized method was applied to the detection of actual water samples and urine samples in the endemic arsenism area to verify the feasibility of the method.ResultsStudy 1 Optimization of a method for the determination of arsenic in urine by Hydride Generation Atomic Fluorescence Spectrometry with ammonium persulfate digestionA method for the determination of arsenic in urine by Hydride Generation Atomic Fluorescence Spectrometry with ammonium persulfate digestion was optimized.Urine samples were digested with 1.5 mol / L ammonium persulfate solution,and the gradient temperature rise method was used.The gradient temperature was raised to 300 ° C and maintained for 30 min.The detection limit of the optimized method was 0.03 μg/L.The average recoveries of three urine samples were 105.62%,95.76%,105.50%,and the recoveries ranged from 92.1% to 108.15%.The accuracy of this method was verified by using AN20210101 and AN20210102 quality control samples with low and high concentrations of urinary arsenic.The detection results were within the published consensus value range,and the relative standard deviations of the two quality control samples were 0.73% and 0.52%,respectively.Study 2 optimized the HPLC-ICP-MS method for the determination of arsenic trioxide As(III),arsenic trioxide As(V),monomethyl arsenic(MMA),dimethyl arsenic(DMA),arsenic betaine(As B)in water and urineAccording to the mobile phase optimization experiment,80 mmol / L ammonium carbonate solution(p H 8.6)was selected as mobile phase a,2% methanol solution as mobile phase B,the flow rate was 1.0 ml / min,and the injection volume was 25 u L,which was the best elution condition of this method.The analysis was carried out under the optimized experimental conditions,and the arsenic mass concentration was 0~50 ug/L Within the standard curve range,five arsenic species were effectively separated,and the linear relationship of five arsenic species was greater than 0.9999.The detection limits of As(III),As(V),MMA,DMA,and As B were 0.06,0.03,0.03,0.03,and 0.02 ug/L,respectively.The constructed method was applied to the detection of actual water samples and urine samples in arsenic endemic areas.The recoveries of five arsenic forms in 90 different water samples ranged from 83.55% to 115.78%,the spiked recoveries of five arsenic forms in 30 residents’ urine samples ranged from 88.20% to 115.93%,and the RSD of 120 actual samples were less than 5.0%.Conclusion1.A method for the determination of arsenic in urine by Hydride Generation Atomic Fluorescence Spectrometry with ammonium persulfate digestion was successfully optimized and constructed.The method has high precision and accuracy.Using 1.5 mol/L ammonium persulfate instead of mixed acid(nitric acid,sulfuric acid and perchloric acid 3:1:1)to digest urine samples,not only the digestion reagent preparation is simpler and safer,but also the sample processing time is greatly shortened after improving the digestion method,the number of samples digested at one time is also greatly improved,and the work efficiency is improved,which is suitable for the detection of large quantities of urine arsenic samples.2.A method for the determination of arsenic trioxide(As(III)),arsenic trioxide(AsV),monomethyl arsenic(MMA),dimethyl arsenic(DMA),and arsenic betaine(As B)in water and urine by HPLC-ICP-MS was successfully optimized and constructed.The optimized method has good accuracy and high precision,and can be effectively applied to the detection of water samples and residents’ urine samples in Endemic Arsenism Areas,providing technical basis for more scientific and perfect monitoring of Endemic Arsenism Areas,It has important practical application value to provide technical support for the formulation of national standards for the determination of arsenic speciation in water and urine by HPLC-ICP-MS in the future. |
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