In situ Self-transforming Membrane as Solid Phase Microextraction Coating Extraction of PAHs in Environmental Water Samples

BACKGROUNDPolycyclic aromatic hydrocarbons (PAHs) are one of the persistent organic pollutants which are carcinogenic and difficult to degrade, and are widespread in the environment. The direct analysis of trace PAHs in the environment is often difficult because of the low sensitivity of the detection methods. It is necessary to combine separation and enrichment methods. Conventional sample pretreatment techniques, such as Soxhlet extraction and liquid-liquid extraction, are time-consuming and use a large number of organic solvents.

OBJECTIVESTo develop a new, simple, and environmentally-friendly method for sample pretreatment.

METHODSSolid phase microextraction (SPME) is a solvent-free pretreatment technology which integrates sampling, enrichment and injection. Combined with gas chromatography-mass spectrometry (GC-MS), it can produce the rapid enrichment and detection of trace organic compounds in a complex matrix. At present, the research focus of improving SPME technology is to improve the mechanical strength and extraction performance of the coating. Using iron wire (IW) as the carrier, which also provided the iron ion source, a porous MOFs film[MIL-53(Fe)] was grown on iron wire with good mechanical stability by in-situ self-transformation. It was used as the solid phase microextraction coating[IW@MIL-53(Fe)]. Seven kinds of non-volatile condensed ring PAHs were used as the target analyte, and immersion extraction mode combined with GC-MS as detection means were used to verify its extraction performance.

RESULTSResults showed that the extraction performance of the new coating was 1-2 times higher than that of the commercial 100μm PDMS coating, and the coating can be used stably for more than 120 times. The detection limits of the methods were 0.03-2.25ng/L, the linear ranges were 250-10000ng/L, and the correlation coefficients were in the range of 0.9903-0.9991. The coating was applied successfully to the detection of PAHs in natural water, where the recoveries were from 80.1% to 108.5%.

CONCLUSIONSThis study not only provides an idea for the simple and rapid preparation of high-efficiency SPME coatings, but also has great potential to be applied to determinate trace volatile organic pollutants in water with high accurateness and efficiency.