Evaluation of sequential injection chromatography for reversed phase separation of triazine herbicides exploiting monolithic and core–shell columns

Abstract

This paper describes the development of reversed phase sequential injection chromatography (SIC) methods for separation of simazine (SIM) and atrazine (AT), as well as their metabolites deethylatrazine (DEA), deisopropylatrazine (DIA) and hydroxyatrazine (HAT) exploiting silica based monolithic (50×4.6mm) and core–shell (30×4.6mm, 2.7µm particles) columns. The separation was made by stepwise elution with two mobile phases: MP1 composed of 15:85 (v/v) acetonitrile: 2.5mmolL−1 acetic acid/ammonium acetate buffer (pH 4.2), and MP2, composed of 35:65 (v/v) acetonitrile: 2.5mmolL−1 acetic acid/ammonium acetate buffer (pH 4.2).The less hydrophobic compounds (DIA, HAT and DEA) eluted with MP1, whereas SIM and AT eluted with MP2. The method using core–shell column exhibited better chromatographic efficiency compared with monolithic column for separation of SIM and AT, but failed to provide base line separation of DIA and HAT. The proposed composition of mobile phases enabled the monolithic column to separate all the studied compounds with resolution >2.3 at flow rate of 35µLs−1 and sampling throughput of 8 analyses per hour, whereas in the core–shell the maximum flow rate allowed in the SIC system was 8µLs−1 (sampling throughput of 3 analyses per hour). The limits of detection were between 24µgL−1 (AT) and 40µgL−1 (DEA) using the monolithic column, and between 20µgL−1 (SIM) and 38µgL−1 (DEA) with the core–shell. Ultrasound-assisted extraction (80:20v/v acetonitrile:water) of a soil sample enriched with the five triazines (250, 500 and 1000µgkg−1) resulted recoveries between 51% and 121% of the spiked concentrations.