A new selective liquid membrane extraction method for the determination of basic herbicides in agro-processed fruit juices and Ethiopian honey wine (Tej) samples

Abstract

Supported liquid membrane (SLM) extraction was optimised for trace extraction and enrichment of selected triazine herbicides from a variety of agro-processed fruit juices and Ethiopian honey wine (Tej) samples. In the extraction process, a 1:1 mixture of n-undecane and di-n-hexylether was immobilised in a thin porous PTFE membrane that forms a barrier between two aqueous phases (the donor and acceptor phases) in a flow system. The extracts constitute the selectively enriched analytes collected from the acceptor phase and were analysed by transferring to a HPLC-UV system using a diode array detector at 235 nm. High enrichment factors were obtained with very good repeatability of results, and the detection limit was lower than 3.00 µg l⁻¹ for ametryn in apple juice. The optimised method showed very good linearity of over 50–500 µg l⁻¹ with a correlation coefficient of >0.990 or better for triplicate analysis. All chromatograms gave well resolved peaks with no interfering peaks at the retention times of the selected triazines, showing high selectivity of the SLM extraction method in combination with HPLC-UV for the selected matrices. The optimised method can be used as an alternative solventless extraction method for microgram-level extraction of other triazine herbicides and a variety of pesticides from liquid and semi-liquid environmental, biological and food matrices.

Keywords:

• chromatographic analysis
• herbicides
• beverages

Acknowledgements

The Swedish International Development Agency and the Department for Research Cooperation (SIDA/SAREC) are thanked for financial support made available through the pesticide project. Instrumental facilities for successfully accomplishing this project were provided by the Department of Chemistry of Addis Ababa University. The traditional Tej processing and preparation was done by W/ro Adanech Megersa whose generous assistance is also acknowledged.