The parallel segmented flow column as an alternative front-end LC strategy for trace analyses

Abstract

The parallel segmented flow (PSF) chromatography column was applied for the first time to trace residue analyses with mass spectral detection. Three problematic pesticides, notorious for poor peak shape and ionization issues were selected to illustrate the advantages and disadvantages of utilizing the PSF column as an alternative front-end separation interface for LC-MS approaches. Assessment of performance for each pesticide was based on a spiked lemon matrix prepared via a QuEChERS (quick, easy, cheap, rugged and safe) sample preparation approach. Comparisons were made between assays conducted using a conventional column and a PSF column (operated with a 40% segmentation ratio), each packed with identical stationary phases and of the same column format. Both columns were connected to the MS detector using the exact same connective tubing and electrospray (ESI) conditions. The primary advantage of the PSF column was that it enabled an increase in throughput by at least 2.5 times compared to the conventional HPLC column. At the same time, the volumetric flow to the MS was exactly the same for both the PSF column and the conventional column. Effectively there was no difference in the sensitivity provided by peak areas between the PSF and conventional columns: peak area LOQ values were comparable, 4–9 μg/kg for the PSF and 4–8 μg/kg for the conventional column. This is a vital requirement for food control methods to secure absence at default maximum residue limit (MRL) of 10 μg/kg (10 ppb) level. Since the efficiency of the PSF was superior to that of the conventional column, the peak width of eluting components was reduced by as much as 70% in the former compared to the peak widths on the latter. Hence, the PSF column provides greater peak capacity and this will enable faster analysis of complex samples.