Exploring hand-portable nano-liquid chromatography for in place water analysis: Determination of trimethylxanthines as a use case

Analytical performance and optimization of figures of merit of a portable nano liquid chromatograph (NanoLC) with UV detection at 255 nm have been established for in place analysis. Methylxanthines: caffeine, theophylline and theobromine were selected as target analytes. A fast labmethod based on IT-SPME coupled on linewith capillary liquid chromatograph (CapLC) with diode array detection (DAD) was employed for comparative studies. ITSPME and solid phase extractionwere coupled off-line to NanoLC for improving instrumental parameters, mainly detection capacity and selectivity. IT-SPME or SPE/portable NanoLC based methods were superior in terms of chromatographic resolution and organic solvent consumption per sample, around 200 mu L vs 10 mL for IT-SPME-CapLC-DAD. Limits of detection (LODs) obtained with the SPE/portable NanoLC were 2-10 ng/mL, which can be suitable for testing the presence of the analytes in several environmental waters in the field. As predictable, the labmethod provided better LODs, between 0.1 and 0.5 ng/mL. Good linearity was achieved for both methods and precision was similar for them (<= 7%). Both systems were tested for the analysis of real water samples with suitable results. (C) 2020 Elsevier B.V. All rights reserved.