Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country, Bilbao, Spain.
Anal Bioanal Chem. 2011 Jul;401(1):339-52. doi: 10.1007/s00216-011-5074-4. Epub 2011 May 20.
The analysis of organic pollutants in environmental water samples requires a pre-concentration step. Pre-concentration techniques such as stir bar sorptive extraction (SBSE) have gained popularity since they minimise the use of toxic organic solvents and can be considered as green analytical techniques. Similar to other pre-concentration techniques, one of the problems when SBSE is used is the matrix effect, which often occurs during the analysis of environmental water samples such as estuarine or wastewater samples. The present work studied the matrix effect during SBSE coupled to in-tube derivatisation-thermal desorption (TD)-gas chromatography-mass spectrometry for the determination of several endocrine disruptor compounds, such as alkylphenols, bisphenol A, estrogens and sterols, in environmental water samples, after optimisation of the major variables affecting the determination. Variables such as the addition of methanol or an inert salt to the donor phase, the extraction temperature, the volume of the donor phase, the stirring rate and the extraction time were studied during the SBSE optimisation. In the case of the in-tube derivatisation and TD step, the volume of the derivatisation reagent (N,O-bis(trimethylsilyl)triufloroacetamide with 1% of trimethylchlorosilane (BSTFA + 1% TMCS)) and the cryo-focusing temperature were fixed (2 μL and -50 °C, respectively) according to a consensus between maximum signal and optimal operation conditions. Good apparent recovery values (78-124%) were obtained for most of the analytes in Milli-Q water, except for 4-tert-octylphenol (4-tOP), which showed apparent recovery values exceeding 100%. Precision (n = 4) was in the 2-27%, and method detection limits were in the low nanogrammes per litre level for most of the analytes studied. The matrix effect was studied using two different approaches. On the one hand, Milli-Q water samples were spiked with humic acids, and apparent recovery values were studied with and without correction with the corresponding deuterated analogue. On the other hand, estuarine water and wastewater samples were spiked with known concentrations of target analytes, and apparent recoveries were studied as explained above. In general, the matrix effect could be corrected with the use of deuterated analogues, except for 4-tOP and nonylphenols for which [(2)H(4)]-n-nonylphenol did not provide good corrections.
环境水样中有机污染物的分析需要进行预浓缩步骤。搅拌棒吸附萃取（SBSE）等预浓缩技术由于减少了有毒有机溶剂的使用，因此被认为是绿色分析技术，因此越来越受欢迎。与其他预浓缩技术一样，当使用 SBSE 时，其中一个问题是基质效应，这种效应在分析环境水样（如河口或废水样品）时经常发生。本工作研究了在 SBSE 与管内衍生-热解吸（TD）-气相色谱-质谱联用测定几种内分泌干扰化合物（如烷基酚、双酚 A、雌激素和甾醇）过程中的基质效应，对影响测定的主要变量进行优化后，在环境水样中进行测定。在 SBSE 优化过程中，研究了添加甲醇或惰性盐到供体相、萃取温度、供体相体积、搅拌速度和萃取时间等变量。对于管内衍生化和 TD 步骤，衍生化试剂（N,O-双（三甲基硅基）三氟乙酰胺与 1%三甲基氯硅烷（BSTFA+1%TMCS））的体积和冷冻聚焦温度（分别为 2μL 和-50°C）根据最大信号和最佳操作条件之间的共识固定。在 Milli-Q 水中，大多数分析物的表观回收率（78-124%）良好，除了 4-叔辛基酚（4-tOP）外，其表观回收率超过 100%。大多数研究的分析物的精密度（n=4）在 2-27%之间，方法检测限为大多数分析物的纳克/升水平。通过两种不同的方法研究了基质效应。一方面，在 Milli-Q 水中加入腐殖酸，研究了有和没有相应氘代类似物校正时的表观回收率。另一方面，向河口水和废水样品中加入已知浓度的目标分析物，如上所述研究表观回收率。一般来说，可以使用氘代类似物来校正基质效应，但 4-tOP 和壬基酚除外，其中 [(2)H(4)]-n-壬基酚不能提供良好的校正。
