Determination of polycyclic aromatic hydrocarbons in surface water using simplified liquid–liquid micro-extraction and pseudo-MRM GC/MS/MS†
A simplified liquid–liquid micro-extraction (LLME) GC/MS/MS method was developed for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in surface water. This method utilizes a pseudo multiple reaction monitoring (PMRM) mode, a technique in which the third quadrupole monitors the same m/z as for the first quadrupole precursor ion. The use of helium as the only collision gas improved the sensitivity by significantly reducing both PAH compound fragmentation and baseline noise. For PAH determination, the PMRM approach proved superior to the classical quadrupole MRM technique in terms of enhanced sensitivity. With observed improvements in sensitivity, micro-extraction using only 4 mL of a novel binary solvent became possible, with corresponding reduction in time consuming sample preparation procedures and toxic solvent usage. Quantifying and qualifying ions, in addition to retention times, were used to verify trace level PAHs. During method validation, the limit of quantitation (LOQ) in surface water was observed to be 10 ng L−1 for the target PAHs. The recovery of individual PAHs was in the range of 80 to 114% from a water matrix, with a corresponding precision between 1.4 and 4.8% RSD. The robustness and accuracy of this method was demonstrated by its success in repeated proficiency test studies. The procedure has been successful during routine use in environmental sample testing and analysis of chemically enhanced water accommodated fraction (CEWAF) samples from toxicological LC50 (50% lethal concentration) bioassays, showing its applicability to situations in which both crude oil and oil spill dispersants are present.