Determination of iodinated phenol species at parts-per-trillion concentration levels in different water samples by solid-phase microextraction/offline GC-ICP-MS

Abstract

An analytical methodology using gas chromatography (GC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was applied in order to analyze iodophenols. The new method takes advantage of the element-specific and highly-sensitive detection provided by the ICP-MS technique and is applied to the analysis of 2-iodophenol, 4-iodophenol and 2,4,6-triiodophenol. The determination of these iodophenols at low ng l−1 levels was possible by optimizing and applying solid-phase microextraction (SPME). Diverse types of SPME fibers, including the 100 µm poly(dimethylsiloxane) (100-PDMS), 7 µm poly(dimethylsiloxane) (7-PDMS), 75 µm Carboxen-poly(dimethylsiloxane) (CAR-PDMS) and 85 µm polyacrylate, were studied and the CAR-PDMS coated fiber was found to work best with the iodinated compounds of interest. Optimal conditions for the extraction and preconcentration of the iodophenols from water samples were found to be at pH = 2, an extraction time of 30 min and desorption in the GC injector at 290 °C for 2 min. Additionally, a new commercially available interface between GC and ICP-MS was used by heating the entire device at 325 °C in order to maintain peak sharpness. The introduction of oxygen as an optional gas provided an increase in sensitivity; instrument detection limits within the low ng l−1 level are demonstrated for all species examined. The precision, as relative standard deviation, did not exceed 5.4% for 10 manual injections. The method was applied to the speciation analysis of iodophenols in river, tap, and bottled water samples.