Microwave-assisted extraction behavior of non-polar and polar pollutants in soil with analysis by high-performance liquid chromatography

Abstract

Microwave-assisted extraction (MAE) was applied for the first time to study the thermal degradation of five carbamates (propoxur, thiuram, propham, methiocarb, chlorpropham) after heating for 6 min at 95°C with different extractants. Analytes were determined by high performance liquid chromatography (HPLC) with UV detection. It was found that significant thermal degradation of the five targets occurred under the extraction conditions. The break down percentage ranged from 10% to 100%, depending on polarities of both analytes and extractants. The greater the polarity of the extractant, the less degradation the analyte underwent. Lower recoveries were found for all carbamates with less polar extractants, such as hexane-acetone (4:1, v/v) and dichloromethane. With more polar extractants (methanol, hexane-acetone 1:4 and 1:1), higher recoveries of three carbamates (propoxur, methiocarb, and chlorpropham) were obtained, whereas the recoveries of the other two remained low. Some non-polar and polar pollutants spiked in soil, such as polynuclear aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), triazines (atrazine, simazine), and carbamates (propoxur, methiocarb, chlorpropham), subjected to MAE in a closed-vessel microwave system under 80% magnetron power output (1 200 W) at 115°C, were also studied. The recoveries of such pollutants ranged between 70% and 99% with excellent reproducibility, except for carbamates. The effects of the soil matrix, the soil moisture, and aging on recoveries were also investigated.