Cold fiber solid phase microextraction in solid sample analysis
The cold fiber solid phase microextraction (SPME) system was improved by minimizing the coating temperature fluctuation range, and the performance of the system was evaluated by investigating the extraction of PAHs from spiked sand samples. The coating temperature can be made relatively constant and the relative standard division (RSD) for most compounds was smaller than 2%. A simplified cold fiber system without the solenoid valve was modified to connect CO2 delivery tubing directly to the liquid CO2 tank. The robustness of this system was evaluated with different sizes of CO2 delivery tubings. The system is stable, low cost and can be easily controlled, which provides a supplementary extraction strategy to the traditional cold fiber system. The extraction amount of the analyte in a specific system was calculated theoretically in advance. The extraction amount for the experiment agreed with that of the calculated result. By using theoretical calculations as a guide, desorption efficiency for aged spiked samples was investigated. In order to achieve better extraction efficiency for PAHs, a programmed coating temperature method was developed and optimized, which led to higher extraction efficiency for most studied analytes compared to the traditional methods. In real sample analysis, certified reference soils were analyzed using cold fiber SPME and the addition of diethylamine successfully realized the exhaustive extraction for volatile compounds and enhanced the recoveries for semi-volatile compounds. Satisfactory extraction amounts for all compounds were achieved by the proposed method after method optimization.