Simultaneous determination of three herbicides (dicamba, 2,4-D, and atrazine) has been achieved by on-line solid-phase extraction (SPE) coupled to multisyringe chromatography (MSC) with UV detection. The preconcentration conditions were optimized; a preconcentration flow rate of 0.5 mL min(-1) and elution at 0.8 mL min(-1) were the optimum conditions. A C(18) (8 mm i.d.) membrane extraction disk conditioned with 0.3 mol L(-1) HCl in 0.5% MeOH was used. A 3-mL sample was preconcentrated, then eluted with 0.43 mL 40:60 water-MeOH. A C(18) monolithic column (25 mm × 4.6 mm) was used for chromatographic separation. Separation of the three compounds was achieved in 10 min by use of 0.01% aqueous acetic acid-MeOH (60:40) as mobile phase at a flow rate of 0.8 mL min(-1). The limits of detection (LOD) were 13, 57, and 22 μg L(-1) for dicamba, 2,4-D, and atrazine, respectively. The sampling frequency was three analyses per hour, and each analysis consumed only 7.3 mL solvent. The method was applied to spiked water samples, and recovery between 85 and 112% was obtained. Recovery was significantly better than in the conventional HPLC-UV method. These results indicated the reliability and accuracy of this flow-based method. This is the first time this family of herbicides has been simultaneously analyzed by on-line SPE-MSC using a monolithic column.
An automated method for the analysis of methylparaben, propylparaben, benzophenone‐3, and benzophenone‐4 in water effluents via on‐line solid‐phase extraction coupled with high‐performance liquid chromatography/ultraviolet detection was proposed. The preconcentration parameters were studied using Plackett‐Burman and Box‐Behnken experimental designs using a C18 sorbent material. The results demonstrated that the eluent volume, composition, and sorbent amount were statistically significant. Optimal conditions for these variables were an eluent volume of 1.55 mL, eluent composition of acetonitrile 100% v/v, and sorbent amount of 100 mg. The eluted sample was analyzed on‐line using high‐performance liquid chromatography equipped with a reversed‐phase C18 column and ultraviolet detection. Separation of the analytes was achieved in 15 min using gradient elution with acetonitrile/water. A simple, sensitive, and rapid analytical method was proposed for personal care compounds without sophisticated or expensive equipment. The limits of detection were 1.20, 1.73, 2.51, and 4.67 μg/L for propylparaben, methylparaben, benzophenone‐3, and benzophenone‐4, respectively. The analysis time was 48 min, consuming only 1.59 mL of eluent acetonitrile for the solid phase extraction step, with minimal sample handling. The method was applied to the analysis of spiked swimming pool and wastewater, with recoveries between 65–107%. These results indicate the reliability of the flow‐based procedure.
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