LAUSR

Graphical abstract Figure. No caption available. HighlightsIn‐tube SPME‐CapLC‐DAD has been evaluated to determine meropenem in ETTs.The analytical performance has been successfully demonstrated.Meropenem was found at concentrations of ng/mL.The proposed procedure is a sustainable and operational efficient methodology. ABSTRACT Meropenem is a widely used antimicrobial for the treatment of infections associated with the use of invasive medical devices in intensive care unit patients. These treatments are not always effective, in fact, in‐vitro studies have demonstrated the difficulty of antimicrobials to penetrate into the biofilm, however in‐vivo studies of the effect of these compounds is a trend, mostly because of the complexity of pulmonary samples extracted from ETTs. Therefore, the objective of this study was to evaluate in‐tube solid phase microextraction (in‐tube SPME) coupled to capillary liquid chromatography (CapLC) with DAD to determine meropenem in ETTs in order to estimate the penetration capability into the biofilm. Firstly, different parameter affecting in‐tube SPME, such as processed sample volume, capillary length, flow and capillary coating were studied. The best analytical response was achieved by processing 500 &mgr;L of standards/samples at 9 &mgr;L/seg with a 60‐cm capillary column coated with 35%‐diphenyl 65%‐polydimethylsiloxane. Under these conditions, the analytical performance of in‐tube SPME‐CapLC‐DAD, using acetonitrile‐water in gradient mode as mobile phase, showed satisfactory results for estimation of meropenem in terms of sensitivity (LOD = 3 &mgr;g/L) and precision (RSD < 10%). Once the experimental conditions were stablished for in‐tube SPME, the extraction of meropenem from the ETTs was studied. Liquid extraction, vortex‐assisted liquid extraction (VALE) and ultrasound‐extraction (UAE) extraction were tested. The results indicated that meropenem could be quantitatively extracted (91 ± 6%) from ETTs, for its subsequent determination by in‐tube SPME‐CapLC‐DAD using water as extraction solvent and 1 min as extraction time. Finally, samples from ETTs used for critically ill patients with different antimicrobial treatments were analysed with successful results.