Barr D B, Ashley D L
Division of Environmental Health Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.
J Anal Toxicol. 1998 Mar-Apr;22(2):96-104. doi: 10.1093/jat/22.2.96.
Because of increasing concern about exposure to carcinogens and other toxicants, reliable methods for biological monitoring of potentially exposed populations must be developed. For biological monitoring to be useful, appropriate biomarkers of exposures to xenobiotics must be identified, and sensitive, specific methods for quantifying the targeted biomarker must be developed. We have developed a sensitive and selective method for the analysis of N-acetyl-S-(2-hydroxyethyl)-L-cysteine (HEMA), urinary metabolite of at least three different known human carcinogens (vinyl chloride, ethylene oxide, and ethylene dibromide). The method uses strong anion-exchange solid-phase extraction and isotope-dilution high-performance liquid chromatography-tandem mass spectrometry. Our method is simple and is not labor intensive; the preparation time per sample is less than 10 min. Because urine samples vary in both their concentration and ion strength, intersample variability in HEMA recovery during the extraction is large. To overcome this inherent limitation, we use the isotope-dilution technique, which allows a complete correction for the extraction recovery for each sample. The limit of detection of the method is 0.68 microgram/L in a 1-mL urine sample with a coefficient of variation of 22% (determined by replicate analyses at both 4 and 11 micrograms/L) and an accuracy indistinguishable from 100%. Preliminary analyses of urine from a population with no known overt exposure to the parent toxicants show a frequency of detection of approximately 75%, which indicates that this method has the sensitivity to detect urinary HEMA derived from environmental exposure. We are currently using this method to establish a reference range of background exposure to these toxicants in the U.S. population.
由于人们越来越关注致癌物和其他有毒物质的暴露问题，因此必须开发出可靠的方法来对潜在暴露人群进行生物监测。为了使生物监测发挥作用，必须识别出接触外源性物质的合适生物标志物，并开发出灵敏、特异的方法来定量目标生物标志物。我们已经开发出一种灵敏且具选择性的方法，用于分析N-乙酰-S-(2-羟乙基)-L-半胱氨酸（HEMA），它是至少三种不同已知人类致癌物（氯乙烯、环氧乙烷和1,2-二溴乙烷）的尿液代谢物。该方法采用强阴离子交换固相萃取和同位素稀释高效液相色谱-串联质谱法。我们的方法简便，无需大量人力；每个样品的制备时间少于10分钟。由于尿液样品的浓度和离子强度各不相同，提取过程中HEMA回收率的样品间变异性很大。为克服这一固有局限性，我们采用同位素稀释技术，该技术能对每个样品的提取回收率进行完全校正。该方法在1 mL尿液样品中的检测限为0.68微克/升，变异系数为22%（通过在4微克/升和11微克/升水平进行重复分析确定），准确度与100%无显著差异。对未明确暴露于母体毒物的人群尿液进行的初步分析显示，检测频率约为75%，这表明该方法具有检测环境暴露来源的尿液HEMA的灵敏度。我们目前正在使用该方法来确定美国人群中这些毒物背景暴露的参考范围。
