Direct injection of tissue extracts in liquid chromatography/tandem mass spectrometry for the determination of pharmaceuticals and other contaminants of emerging concern in mollusks

Abstract

In the present study, a straightforward approach was validated for the analysis of pharmaceutically active compounds and endocrine-disrupting chemicals in the mollusk tissues, with a focus on two species commonly consumed in Southeast Asia (green mussels: Perna viridis; lokan clams: Polymesoda expansa). This approach relied on a simple solvent extraction (shaker table) followed by direct injection in liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). This "cleanup-free" approach was made possible by the use of isotopically labeled surrogates (to correct for matrix effects) and a post-column switch on the LC-MS/MS system (to remove potential interfering material). Altogether, relative recoveries were satisfactory for 36 out of 44 compounds (26-163% range) and excellent for 27 out of 44 compounds (79-107% range). Method detection limits (MDLs) were usually expressed in the nanogram per gram wet weight (ww) range and below. The method was successfully applied to 16 batches of green mussel samples collected in Singapore coastal waters. Trace levels of six compounds were detected in mussel tissues: caffeine (0.22-1.55 ng g(-1) ww), carbamazepine (<MDL-0.10 ng g(-1) ww), diltiazem (<MDL-0.13 ng g(-1) ww), diphenhydramine (<MDL-1.31 ng g(-1) ww), atrazine (<MDL-0.19 ng g(-1) ww), and bisphenol A (<MDL-7.6 ng g(-1) ww). The present method offers the perspective of high sample throughput, allowing for intensive monitoring programs and detailed exposure assessments.