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Gas chromatographic determination of parabens after in-situ derivatization and dispersive liquid-liquid microextraction

Prichodko A, Janenaite E, Smitiene V, Vickackaite V.

Acta Chromatographica

2012

Vol. 24, no. 4

589--601

Dispersive liquid-liquid microextraction in combination with an in situ derivatization is suggested for parabens sampling and preconcentration. The derivatization was carried out with acetic anhydride under alkaline conditions maintained using di-potassium hydrogen phosphate. The effects of an extraction solvent type, extraction and disperser solvents volume, extraction time, and ionic strength of the solution on the extraction efficiency were investigated. Chlorobenzene containing n-hexadecane as internal standard was used as an extracting solvent and acetone was used as a disperser solvent. The calibration graphs were linear up to 10 mg mL-1, correlation coefficients were 0.997–0.999, enrichment factors were from 70 for methylparaben to 210 for butylparaben, and detection limits were 22, 4.2, 3.3, and 2.5 µg L−1 for methylparaben, ethylparaben, propylparaben, and butylparaben, respectively. Repeatabilities of the results were acceptable with relative standard deviations up to 11%. A possibility to apply the proposed method for parabens determination in water samples was demonstrated.

Single drop microextraction of esters : comparison of headspace and direct extractions

Tankeviciute A., Bobnis R., Kazlauskas R., Vickackaite V.

Chemia Analityczna

2005

Vol. 50, No. 3

539-549

The applicability of headspace and direct microextractions to a single drop, in order to determine several esters, has been studied. A drop of p-cymene containing n-nonane as an internal standard was used for extraction. The analytes were extracted to the drop positioned at the tip of a microsyringe fixed directly above the extraction via!, so that the needle passed the septum and the needle tip appeared above (headspace microextraction) or below (direct microextraction) the surface of the solution. After the extraction was finished, the drop was retracted back into the needle and injected directly into the GC system. Experimental conditions, including sampling time, sampling temperature, stirring rate and ionic strength of the solution were optimised in respect to the extraction efficiency. The proposed method was applied to the analysis of white wine.

Zbadano przydatność mikroekstrakcji do pojedynczej kropli zanurzonej w próbce oraz z fazy nadpowierzchniowej do oznaczania estrów. Do ekstrakcji zastosowano kroplę p-cymenu zawierającą n-nonan jako wzorzec wewnętrzny. Anality ekstrahowano, po przekłuciu igłą gumowej membrany, do kropli znajdującej się nad powierzchnią roztworu lub pod po wierzchnią roztworu. Po zakończeniu ekstrakcji kroplę wciągano do igły i dozowano ją do chromatografu. Warunki doświadczenia, tj.: czas, temperaturę, szybkość mieszania i siłę jonową roztworu optymalizowano pod względem sprawności ekstrakcji. Proponowaną metodę zastosowano do analizy białego wina.