Determination Of Trace Lead In Urine By Ionic Liquid Micro Extraction-Graphite Furnace Atomic Absorption Spectrometry

Objective Lead was a toxic heavy metal element which widely used in automotive batteries,alloys,dyes and arms.Nervous system,cardiovascular system,reproductive system,kidneys might be damaged by lead,inorganic lead was listed as a Class 2A carcinogen by the International Agency for Research on Cancer?IARC?.Feces and urine was the main pathway for the elimination of lead.There was a significant linear relationship between urinary lead excretion and lead content in the body,so that it was a good biomarker for lead exposure.China's GBZ 37-2015occupational chronic lead poisoning diagnostic criteria stipulate that the biological exposure limit of urine lead is 70?g/L.China has established a national standard method GBZ/T303-2018 for the determination of lead in urine,this method used matrix modifier direct dilution assay,the determination results are greatly affected by the urine sample matrix,resulting in a large error in the determination results of low concentration urine samples,it is only suitable for the determination of urine lead content in occupational exposure populations.In view of the above problems,this project aimed to establish a new method for the determination of trace lead in urine by ionic liquid microextraction-graphite furnace atomic absorption spectrometry,the urine samples was processed by ionic liquid microextraction to reduce the urine sample matrix and detection limit.which provided a sensitive method for monitoring lead in urine,and at the same time provided new ideas and technical methods for the revision of urine lead standard test methods and biological exposure limits in China.Methods 1)Ammonium pyrrolidine dithiocarbamate?APDC?and anhydrous ethanol were used as chelating agent and dispersant,respectivelythe ionic liquid1-hexyl-3-methyl-imidazolium hexafluorophosphate[Hmim][PF₆]was used as extractant for the extraction of lead in urine.The lead in urine was extracted under the condition of pH 9 and 30?of water bath.Supernatant was removed after centrifugation,and then 10%nitric acid was used to back-extract of lead,after which,the second time of centrifugation was conducted.Then the nitric acid solution was taken and vitamin C solution was added into which as matrix modifier,Fina lly,the mixture was determined by graphite furnace atomic absorption?GFAAS?.2)The amount of chelating,dispersant and extracting agent,the extraction temperature,extraction pH,eluent dosage,eluent time and graphite furnace parameters were optimized and selected by single factor rotation method and orthogonal design.3)The methodological indicators such as detection limit,linear range,precision,accuracy,sample stability were verified.4)The developed method was applied to the urine samples of volunteers,the actual urine samples of the battery manufacturer workers and the purchased lyophilized human urine lead standard materials?National Standards Institute,GBW09104?.5)Evaluate the uncertainty introduced during the experiment to determine the key aspects of the impact.Results 1)The Optimization of GFAAS working conditions:wavelength283.3nm,slit width 0.7nm,lamp current 10mA,xenon lamp background,Lanthanum nitrate impregnated graphite tube,injection volume 10?L,ashing temperature 500°C,atomization temperature 1300°C.2)Extraction conditions:the chelating agent was pyrrolidine dithiocarbamate?APDC?,the dispersing machine was anhydrous ethanol,and the extracting agent was ionic liquid 1-hexyl-3-methyl-imidazolium hexafluorophosphate?[Hmim][PF₆]?,the dosage was 50?L[Hmim][PF₆],0.15mg APDC,0.50mL absolute ethanol,extraction temperature was 30°C,pH 9,200?L 10%nitric acid back extraction for 2min back extraction.3)Under the linear range of0.45⁷5.0?g/L,the standard curve equation was Y=0.0034X+0.0037,the correlation coefficient was greater than 0.999,with a detection limit of 0.45?g/L,and the average spike recoveries were 94.20%¹06.04%,and the relative standard deviations were1.35%³.24%.4)The tested results of the real urine showed that the lead content of volunteers'urine samples were 2.15⁶.34?g/L,and the lead content of battery manufacturers'urine samples were 18.69²6.68?g/L.The average tested value of standard substance was 0.112 mg/L,and the relative standard deviation was 2.56%,within the quality control range?0.107±0.016 mg/L?.Conclusion 1)This study established a new ionic liquid microextraction-graphite furnace atomic absorption spectrometry for the determination of trace lead in urine.2)The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate?[Hmim][PF₆]?was used as extractant,which was satisfactory for the extraction and enrichment of lead in urine.3)The developed method had a range of advantagessuch as easy to operate,low in detection limit,high in sensitivity,good in accuracy,and improved the problem of matrix interference.With such advantages,the method was suitable for the detection of urinary lead in occupational and non-occupational exposed populations.It has practical value and could provide technical support for the determination of urinary lead content.