Department of Food Analysis and Environmental Protection, Faculty of Chemical Technology and Engineering, UTP University of Science and Technology, 3 Seminaryjna Street, 85-326 Bydgoszcz, Poland.
Molecules. 2020 Sep 25;25(19):4419. doi: 10.3390/molecules25194419.
Solvent evaporation is often used in the sample preparation procedure for the determination of organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organic pesticides. Because of the loss of analyte during this step, a high-boiling solvent, i.e., a keeper, is often added to the extract before evaporation. However, there are almost no basic studies found in the literature on the selection of keepers for the appropriate type of analytes (keepers are usually selected only on the basis of information provided by various recommendations). In this work, the effect of several keepers (isooctane, toluene, nonane, octanol, dodecane) on the recovery of various analytes (PAHs, PCBs, organic pesticides) was evaluated (during evaporation in a stream of nitrogen, at 40 °C). The analysis of the results obtained for the tested compounds shows that 1-octanol is a universal keeper for compounds with low volatility, i.e., PCBs (average recovery: 97.6%), organochlorine pesticides (average recovery: 95.0%), organophosphorus pesticides (OPPs; average recovery: 99.7%) and higher mass PAHs (average recovery: 91.9%). The use of isooctane as a keeper yields high recoveries for PAHs, regardless of their volatility (average recovery: 95.5%). When using 1-octanol or dodecane as a keeper, the reversed solvent effect (during GC analysis) was noted in relation to volatile analytes causing the distortion of their peaks. Additionally, the phenomenon of loss of some analytes (e.g., OPPs) was observed during evaporation without heating the vials. However, in the case of PCBs, organochlorine pesticides (OCPs) and -hydroxybiphenyl, evaporation under such conditions yields recoveries greater than or equal to 90.0%. The results presented in this work can help in finding a suitable keeper for a specific group of analytes or an alternative to the commonly used one, especially in the case of recovery problems.
溶剂蒸发常用于有机污染物如多环芳烃（PAHs）、多氯联苯（PCBs）和有机农药的测定的样品制备过程中。由于在这一步骤中分析物会损失，因此在蒸发前通常会向提取物中添加高沸点溶剂，即保留剂。然而，在文献中几乎没有关于保留剂选择的基础研究适用于适当类型的分析物（保留剂通常仅根据各种建议提供的信息进行选择）。在这项工作中，评估了几种保留剂（异辛烷、甲苯、壬烷、辛醇、十二烷）对各种分析物（PAHs、PCBs、有机农药）回收率的影响（在氮气流中，40°C 下蒸发）。对测试化合物的结果进行分析表明，1-辛醇是低挥发性化合物（即 PCB（平均回收率：97.6%）、有机氯农药（平均回收率：95.0%）、有机磷农药（OPPs；平均回收率：99.7%）和较高质量的 PAHs（平均回收率：91.9%）的通用保留剂。使用异辛烷作为保留剂可以获得高的 PAHs 回收率，而与它们的挥发性无关（平均回收率：95.5%）。当使用 1-辛醇或十二烷作为保留剂时，在与挥发性分析物有关的 GC 分析中会出现相反的溶剂效应，导致其峰形失真。此外，在不加热小瓶的情况下蒸发时，还观察到一些分析物（例如 OPPs）的损失现象。然而，对于 PCB、有机氯农药（OCPs）和β-羟基联苯，在这种条件下蒸发的回收率大于或等于 90.0%。本工作中提出的结果有助于找到适用于特定组分析物的合适保留剂或替代常用保留剂的方法，特别是在回收率存在问题的情况下。
