Ma M, Le X C
Department of Public Health Sciences, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Clin Chem. 1998 Mar;44(3):539-50.
We developed and evaluated a method for the determination of microgram/L concentrations of individual arsenic species in urine samples. We have mainly studied arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) because these are the most commonly used biomarkers of exposure by the general population to inorganic arsenic and because of concerns over these arsenic species on their toxicity and carcinogenicity. We have also detected five unidentified urinary arsenic species resulting from the metabolism of arsenosugars. We combined ion pair liquid chromatography with on-line hydride generation and subsequent atomic fluorescence detection (HPLC/HGAFS). Detection limits, determined as three times the standard deviation of the baseline noise, are 0.8, 1.2, 0.7, and 1.0 mu/L arsenic for arsenite, arsenate, MMAA, and DMAA, respectively. These correspond to 16, 24, 14, and 20 pg of arsenic, respectively, for a 20-muL sample injected for analysis. The excellent detection limit enabled us to determine trace concentrations of arsenic species in urine samples from healthy subjects who did not have excess exposure to arsenic. There was no need for any sample pretreatment step. We used Standard Reference Materials, containing both normal and increased concentrations of arsenic, to validate the method. Interlaboratory studies with independent techniques also confirmed the results obtained with the HPLC/HGAFS method. We demonstrated an application of the method to the determination of arsenic species in urine samples after the ingestion of seaweed by four volunteers. We observed substantial increases of DMAA concentrations in the samples collected from the volunteers after the consumption of seaweed. The increase of urinary DMAA concentration is due to the metabolism of arsenosugars that are present in the seaweed. Our results suggest that the commonly used biomarkers of exposure to inorganic arsenic, based on the measurement of arsenite, arsenate, MMAA, and DMAA, are not reliable when arsenosugars are ingested from the diet.
我们开发并评估了一种测定尿样中微克/升浓度的各砷形态的方法。我们主要研究了亚砷酸盐[As(III)]、砷酸盐[As(V)]、一甲基胂酸(MMAA)和二甲基胂酸(DMAA)，因为这些是普通人群接触无机砷最常用的生物标志物，且人们担心这些砷形态的毒性和致癌性。我们还检测到了由砷糖代谢产生的五种未鉴定的尿砷形态。我们将离子对液相色谱与在线氢化物发生及随后的原子荧光检测(HPLC/HGAFS)相结合。以基线噪声标准偏差的三倍确定的检测限，亚砷酸盐、砷酸盐、MMAA和DMAA的砷分别为0.8、1.2、0.7和1.0μg/L。对于进样分析的20μL样品，这些分别对应16、24、14和20pg的砷。出色的检测限使我们能够测定未过度接触砷的健康受试者尿样中痕量浓度的砷形态。无需任何样品预处理步骤。我们使用了含有正常和升高浓度砷的标准参考物质来验证该方法。与独立技术的实验室间研究也证实了用HPLC/HGAFS方法获得的结果。我们展示了该方法在四名志愿者摄入海藻后尿样中砷形态测定的应用。我们观察到志愿者食用海藻后采集的样品中DMAA浓度大幅增加。尿中DMAA浓度的增加是由于海藻中存在的砷糖的代谢。我们的结果表明，当从饮食中摄入砷糖时，基于亚砷酸盐、砷酸盐、MMAA和DMAA测量的常用无机砷接触生物标志物不可靠。
