Ultrasound-assisted Matrix Solid-phase Research Articles

Ultrasound-assisted Matrix Solid Phase Dispersion for the HPLC-DAD analysis of amphenicols in shrimps

AbstractUltrasound-assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of three amphenicol antibiotics, chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FFC) from shrimp. The target antibiotics were separated on a LiChroCART-LiChrospher® 100 RP-18 (5 μm, 250 × 4 mm) analytical column in less than 9 min, with isocratic elution using a mixture of 70% ammonium acetate (0.05 M) and 30% acetonitrile (v/v). Matrix Solid Phase Dispersion protocol was optimized in terms of extraction sorbent and elution solvent. Two polymer based (Oasis and Nexus) sorbents and one silica based (Lichrolut C18) were compared and different elution solvents such as methanol, acetone, acetonitrile and isopropanol were evaluated based on the achieved recovery rates as well as on the cleanup efficiency. The extraction procedure was performed with and without sonication to evaluate the impact of ultrasounds. TAP and FFC were monitored at 234 nm and CAP at 280 nm by a photodiode array detector. The method was validated according to the European Union Decision 2002/657/EC in terms of linearity, selectivity, stability, accuracy, precision and sensitivity. Detection capability values (CCb) were 64.6 μg/kg for TAP and 1046.8 μg/kg for FFC and 63.8 μg/ kg for CAP.

Ultrasound-assisted dispersive extraction for the high pressure liquid chromatographic determination of tetracyclines residues in milk with diode array detection

Ultrasound assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of tetracyclines (oxytetracycline, tetracycline, epi-chlorotetracycline, chlorotetracycline and doxycycline) from milk. Target analytes were determined by an accurate and sensitive chromatographic analytical method, which was validated to meet the European Legislation criteria. The separation was performed on a LiChroCART-LiChrospher® 100 RP-18 (5μm, 250×4mm) analytical column, operated at ambient temperature, followed by diode array detection.Validation included investigation of linearity, selectivity, stability, limits of detection and quantitation, decision limit, detection capability, trueness, precision and ruggedness according to the Youden’s approach. Limits of quantitation of examined tetracyclines were from 14.5 to 56.6μg/kg significantly lower than respective Maximum Residue Limits, whereas recoveries ranged from 82.0% to 108%. The applicability of the method was evaluated using milk samples purchased from local market. Accuracy of the method was additionally proved by analysis of bovine milk certified reference material (BCR®-492).

Multivariate optimisation of an ultrasound assisted-matrix solid-phase dispersion method combined with LC-fluorescence detection for simultaneous extraction and determination of aflatoxins in pistachio nut samples

This paper describes the application of ultrasound-assisted matrix solid-phase dispersion as an extraction and clean-up procedure for aflatoxins (B1, B2, G1 and G2) and subsequent determination by LC-fluorescence detection. A Box–Behnken design was used to determine the parameters influencing the extraction procedure through response surface methodology and experimental design. The influence of different variables including type of dispersing phase, sample-to-dispersing phase ratio, type and quantity of clean-up phase, ultrasonication time, ultrasonication temperature, nature and volume of the elution solvent were investigated in the optimisation study. C18, graphitic carbon black and acetonitrile were selected as dispersing phase, clean-up phase and elution solvent, respectively. The optimised values were sample-to-dispersing phase ratio of 1:1, 50 mg of graphitic carbon black, 11 min ultrasonication time, 30°C ultrasonication temperature and 3 ml acetonitrile. Under the optimal conditions the limits of detection (LODs) were ranged from 0.04–0.11 µg kg−1 and the relative standard deviations (RSDs) of the extraction method were less than 8.6%. The recoveries of the matrix solid-phase dispersion process ranged from 74% to 78% with relative standard deviation lower than 9% in all cases. Finally, the matrix solid-phase dispersion was successfully applied to extraction of trace amounts of aflatoxins in pistachio samples.