Li Xiaolin, Brownawell Bruce J
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000, USA.
Anal Chem. 2009 Oct 1;81(19):7926-35. doi: 10.1021/ac900900y.
A sensitive and robust method of analysis for quaternary ammonium compounds (QACs) in marine sediments is presented. Methods for extraction, sample purification, and HPLC-time-of-flight MS analysis were optimized, providing solutions to problems associated with analysis of QACs, such as dialkyldimethylammonium (DADMAC) and benzalkonium (BAC) compounds experienced previously. Recognized in this study are the exceptionally high positive mass defects characteristic of alkylammonium or protonated alkylamine ions. No alternative and chemically viable elemental formulas exist within 25.2 mDa when the number of double bond equivalents is low, effectively allowing facile discrimination of this compound class in complex mixtures. Accurate mass measurements of diagnostic collision-induced dissociation fragment ions and heavy isotope peaks were obtained and also seen to be uniquely heavy compared to other elemental formulas. The ability to resolve masses of alkylamine fragment ions is much greater than for the molecular ions of BACs and many other chemicals, opening up a range of potential applications. The power of utilizing a combination of approaches is illustrated with the identification of nontargeted DADMAC C8:C8 and C8:C10, two widely used biocides previously unreported in environmental samples. Concentrations of QACs in sewage-impacted estuarine sediments (up to 74 microg/g) were higher than concentrations of other organic contaminants measured in the same or nearby samples, suggesting that further study is needed.
本文提出了一种灵敏且稳健的分析海洋沉积物中季铵化合物（QACs）的方法。对萃取、样品净化及高效液相色谱-飞行时间质谱分析方法进行了优化，解决了与QACs分析相关的问题，如之前遇到的二烷基二甲基氯化铵（DADMAC）和苯扎氯铵（BAC）化合物的分析问题。本研究认识到烷基铵或质子化烷基胺离子具有异常高的正质量缺陷特征。当双键当量数较低时，在25.2 mDa范围内不存在其他化学上可行的元素分子式，这有效地使得在复杂混合物中能够轻松区分这类化合物。获得了诊断性碰撞诱导解离碎片离子和重同位素峰的精确质量测量结果，并且与其他元素分子式相比，这些结果也显示出独特的重质特征。分辨烷基胺碎片离子质量的能力远大于BACs和许多其他化学物质的分子离子，从而开辟了一系列潜在应用。通过鉴定非靶向的DADMAC C8:C8和C8:C10（两种以前未在环境样品中报道过的广泛使用的杀菌剂），说明了采用多种方法结合的强大功能。受污水影响的河口沉积物中QACs的浓度（高达74微克/克）高于在相同或附近样品中测得的其他有机污染物的浓度，这表明需要进一步研究。
