Combining dispersive solid phase extraction using an inexpensive sorbent with dispersive liquid–liquid microextraction for the efficient extraction of some plasticisers from plastic-packed liquids

Abstract

ABSTRACT The aim of this study is the extraction and determination of di(2-ethylhexyl) adipate and three phthalate esters including di-iso-butyl phthalate, di-n-butyl-phthalate, and di-(2-ethylhexyl) phthalate in several samples which were packed in plastic packages (orange and pineapple juices, three brands of mineral water, and two injectable pharmaceutical solutions). In this work, stearic acid coated calcium carbonate is used as a sorbent in dispersive solid phase extraction followed by dispersive liquid-liquid microextraction. The procedure initiates with the adsorption of the analytes onto the adsorbent. Then, the analytes are removed from the adsorbent by employing an elution solvent. After eluting the adsorbed analytes, the elution solvent is mixed with a few microlitres of a proper extraction solvent. Then, the obtained mixture is rapidly injected into deionised water during the microextraction procedure to attain higher concentrations of the target analytes. Ultimately, an aliquot of the sedimented organic phase is isolated from the aqueous phase by centrifuging and injected into gas chromatography–flame ionisation detector. Under optimal extraction conditions, the limits of detection and quantification were in the ranges of 0.15–0.40 and 0.50–1.33 µg L−1, respectively. Relative standard deviations were less than or equal to 5% for both intra- (n = 6) and inter-day (n = 4) precisions at a concentration of 50 µg L−1 of each analyte. Additionally, sufficiently high values of extraction recoveries and enrichment factors were obtained in the ranges of 53–89% and 266–446, respectively. Abbreviations: DLLME: Dispersive liquid–liquid microextraction; DSPE: Dispersive solid-phase extraction; EF: Enrichment factor; ER: Extraction recovery; FID: Flame ionisation detector; GC: Gas chromatography; LOD: Limit of detection; LOQ: Limit of quantification; MS: Mass spectrometry; RSD: Relative standard deviation