On-column preconcentration in sequential injection chromatography: application to determination of parabens

Abstract

Solid-phase extraction is the most usual technique for analyte preconcentration prior to liquid chromatographic analysis. It involves several time-consuming steps, including cartridge conditioning, sample loading and analyte elution. This work proposes on-column preconcentration in sequential injection chromatography by exploiting analyte retention at the head of the chromatographic column. A relatively high volume of an aqueous sample was carried to the reversed-phase column by water. After preconcentration, a suitable mobile phase was inserted to perform chromatographic separation. The feasibility of the proposed approach was demonstrated by preconcentration of parabens before chromatographic separation and UV detection. A linear response was achieved from 12.0 to 100.0 ng mL À1 (r 2 > 0.998) with detection limits estimated to be 3.1, 3.3 and 4.6 ng mL À1 and enrichment factors of 435, 405 and 420 for methyl, ethyl, and propylparabens, respectively. Coefficients of variation for retention time and peak heights were below 2.2%. The proposed procedure can be applied to paraben extraction and preconcentration, presenting advantages such as minimization of analyte losses and contamination, reduction of organic solvent consumption and avoiding additional extraction cartridges.

Advances in the Hyphenation of Flow Analysis Techniques with Liquid Separations for Pharmaceutical Analysis

“…One of the main advantages of flow analysis methods is the exploitation of zone fluidics for on-line sample pretreatment. Essentially the same protocols can be adapted to hyphenated SIC and MSC systems for simple filtration and dilution [26] or more complicated operations such as solid-phase extraction using packed minicolumns [27][28][29] or the head of the separation column [30].…”

Exploitation of a short monolithic column for in‐line separation and preconcentration: Environmental friendly determination of the emerging pollutant salicylic acid in natural waters

“…The instrumentation is relatively simple and allows in‐line treatment for sample clean‐up and analyte concentration by SPE before the chromatographic separation as well as postcolumn derivatization . On‐column preconcentration in SIC was proposed to simplify the analyte enrichment by SPE . A large sample volume (e.g.…”

“…A large sample volume (e.g. up to 5.0 mL ) is injected into a carrier stream with low elution strength, aiming at accumulation of the analytes at the head of the chromatographic column (or even at the guard column), whereas species with significant differences in polarity are separated. The retained species are further eluted by a suitable mobile phase (MP), thus avoiding additional sample treatment steps.…”

Flow Analysis: Looking Back and Forward

“…75 Potentialities and applications on this subject have been revised 59 and recent innovations include on-line sample preparation before chromatographic separation 76 and on-column preconcentration of the analytes. 77 Novel strategies have been also proposed for liquid-liquid microextractions, including mechanization of dispersive liquid-liquid microextraction 78,79 and cloud point extraction. 80 In the versatile lab-in-syringe modality, 78,80 all involved processes (e.g., chemical derivatization, solvent dispersion, induction of the cloud point, phase separation, and detection) can be carried out inside a syringe.…”