Ding Wang-Hsien, Tsai Pei-Chuan
Department of Chemistry, National Central University, Chung-Li, 32054, Taiwan.
Anal Chem. 2003 Apr 15;75(8):1792-7. doi: 10.1021/ac020536y.
This work describes a modified method to analyze alkyltrimethylammonium chlorides (ATMACs) in river water samples. The proposed method involves adding solid potassium iodide to water sample (pH adjusted to 10.0) as a counterion to enhance the extraction of ATMAC residues by dichloromethane liquid-liquid extraction. The iodide-ATMA+ ion pairs were demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection port. The corresponding ADMAs were then identified and quantitated by gas chromatography/ion trap mass spectrometry (GC/MS) in electron impact and low-pressure positive ion chemical ionization (PICI) modes. A relatively high abundance of ADMAs was detected at a demethylation temperature above 300 degrees C in the injection port. Experimental results indicate that the proposed method is precise and sensitive in ATMACs analysis and allows quantitation at < or = 0.01 microg/L in 500 mL of the water samples. The enhanced selectivity of quasi-molecular ion chromatograms of C12-C18-ADMA, obtained using methanol PICI-MS, enables ATMAC residues to be identified at trace levels in environmental samples. Recovery of the ATMACs in various spiked water samples ranged from 70 to 94% while RSD ranged from 3 to 12%. The concentrations of total measured ATMAC residues in river water samples ranged from nondetectable to 1.24 microg/L.
这项工作描述了一种分析河水样品中烷基三甲基氯化铵（ATMACs）的改进方法。所提出的方法包括向水样（pH值调至10.0）中加入固体碘化钾作为抗衡离子，以增强二氯甲烷液-液萃取对ATMAC残留的萃取效果。碘化物-ATMA⁺离子对在气相色谱进样口中通过热分解脱甲基，生成相应的非离子烷基二甲基胺（ADMAs）。然后通过气相色谱/离子阱质谱（GC/MS）在电子轰击和低压正离子化学电离（PICI）模式下对相应的ADMAs进行鉴定和定量。在进样口中脱甲基温度高于300℃时检测到相对较高丰度的ADMAs。实验结果表明，所提出的方法在ATMACs分析中精确且灵敏，能够在500 mL水样中对≤0.01 μg/L的浓度进行定量。使用甲醇PICI-MS获得的C12 - C18 - ADMA准分子离子色谱图具有更高的选择性，能够在环境样品中痕量鉴定ATMAC残留。各种加标水样中ATMACs的回收率在70%至94%之间，相对标准偏差（RSD）在3%至12%之间。河水样品中测得的总ATMAC残留浓度范围为未检出至1.24 μg/L。
