Environmentally friendly etching of stainless steel wire for plunger-in-needle liquid-phase microextraction of polycyclic aromatic hydrocarbons

An environmentally friendly method of etching a stainless steel plunger wire, to replace the conventional hydrofluoric acid approach, was developed for plunger-in-needle liquid phase-microextraction (PIN-LPME). The one-step etching procedure was performed by immersing the plunger wire in a ferric chloride-hydrochloric acid (PeC13-NCI) solution. The etched wire was then used for LPME as the organic solvent holder. After solvent coating, the wire was directly exposed to a water sample for extraction of polycyclic aromatic hydrocarbons (PAHs), which were then subjected to thermal desorption in the injector of a gas chromatograph for gas chromatography -mass spectrometric (GC-MS) analysis. The parameters affecting PIN-LPME efficiencies (i.e., extraction solvent, solvent coating mode and time, stirring rate, extraction time and salting effect) were also investigated. Under the most favourable conditions, PIN-LPME-GC-MS exhibited high enrichment factors of between 70 and 349 for the 9 PAHs, low detection limits (between 0.006 and 0.058 ng mL(-1)), and good precision (with relative standard deviations ranging from 4.4% to 9.7%). The developed method was successfully applied for the extraction and determination of PAHs in tap, river and drain water samples. Good relative recoveries of the PAHs over the range of 84.3-101.9% were obtained with spiked genuine water samples.