Development of a QuEChERS-based extraction method for the determination of destruxins in potato plants by UHPLC-MS/MS.

Ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with electrospray ionization has been proposed for the determination of fifteen natural destruxins (A, B, C, D, E, Ed, Ed1, A2, B2, D2, E2, Cl, DesmA, DesmB, and DH-A), secondary metabolites with insecticidal and phytotoxic activities produced by Metarhizium species fungus, which are being studied as biological agents in pest control. Therefore, procedures to control them in the food chain are required, starting with crops. As a consequence, in this study, a simple QuEChERS-based destruxin (dtx) extraction procedure has been developed and validated in four different parts of potato plant (tuber, root, stem and leaves) for the first time. For dtx A, the limits of detection obtained, ranged between 0.5 and 1.3 µg/kg, and for quantification, ranged between 1.7 and 4.2 µg/kg. Precision values were below 8.5%; and in all cases, recoveries were higher than 91%. Finally, the method has been applied in potato samples inoculated by EAMa 01/58-Su strain, where dtxs A and B were detected and quantified. In all cases, dtx B concentration was higher than dtx A.

Trace determination of 10 beta-lactam antibiotics in environmental and food samples by capillary liquid chromatography.

A sensitive and reliable method using capillary HPLC with UV-diode array detection (DAD) has been developed and validated for the trace determination of residues of 10 beta-lactam antibiotics of human and veterinary use, in milk, chicken meat and environmental water samples. The analytes included ampicillin, amoxicillin, penicillin V, penicillin G, cloxacillin, oxacillin, dicloxacillin, nafcillin, piperacillin and clavulanic acid. Legal levels are regulated by the EU Council regulation 2377/90 in animal edible tissues for these compounds. For food analysis, a solid-phase extraction (SPE) procedure consisting in a tandem of Oasis HLB and Alumina N cartridges was applied for off-line preconcentration and cleanup. For water analysis, the first step was only necessary. The limits of detection for the studied compounds were between 0.04-0.06 microg l(-1) for water samples and 0.80-1.40 microg l(-1) (or microg kg(-1)) in the case of foods derived from animals. Average recoveries for fortified samples at different concentration levels ranged between 82.9% and 98.2%, with relative standard deviations (RSDs) lower than 9%. The method showed the advantages of capillary HPLC for the detection of these widely applied antibiotics in different samples at very low concentration levels.

An overview of qualimetric strategies for optimisation and calibration in pharmaceutical analysis using flow injection techniques.

Flow Injection analysis represents an attractive tool because of its great advantages, such as versatility, speed, high sampling rate and wide applicability in the field of pharmaceutical analysis. However, due to the inherent characteristics of the technique, the choice of the best set of operational and chemical conditions is complicated and the conventional univariate optimisation method present some limitations, mainly due to fact that the interdependence of variables is not considered. In relation to the calibration process, because of the transient character of the signals obtained using FIA manifolds coupled with different detection techniques, different strategies can be used in calibration to solve some problems related to the nature of the signal thereby improving the performance characteristics of the method. This paper offers an overview of different methodologies used in optimisation based on the use of statistically designed experiments and some strategies developed for calibration applied to the analysis of pharmaceuticals.

Determination of albumin in biological fluids by flow injection analysis using the peroxyoxalate chemiluminescent system in micellar medium.

A new sensitive analytical procedure for the determination of albumin is presented, based on the participation of a fluorescent derivative of the protein in the peroxyoxalate chemiluminescent system using imidazole as a catalyst. The chemiluminescent emission is detected in a flow injection analysis (FIA) system, employing micellar medium as carrier, whereas the derivatisation reaction is carried out off-line using fluorescamine as a label. The optimisation of the operational and chemical variables of the method such as concentration of reagents, flow-rates, injection volume, etc., involves the use of experimental designs, including Draper-Lin small composite design, scarcely used in analytical chemistry. The performance characteristics were established and a detection limit of about 0.1 fmol of albumin was obtained. The method has been validated and satisfactorily applied to the determination of albumin in human serum and urine.

Integrated pervaporation/detection for the determination of fluoride in pharmaceuticals.

A selective dynamic method for the determination of fluoride in pharmaceuticals based on the integration of pervaporation and potentiometric detection in a laboratory-made module is proposed. The analyte was continuously converted into volatile trimetylfluorosilane by reaction with hexamethyldisilazane, injected into a donor stream and accepted in a basic buffer solution after pervaporation. The method thus developed has a determination range between 1.5 and 200 mg l-1, precision (expressed as R.S.D.) of 3.4%, and has been applied to the determination of fluoride in different pharmaceutical products, with yields ranging between 90.6 and 100.3%. B.V.

Continuous subcritical water extraction of medicinal plant essential oil: comparison with conventional techniques.

A subcritical extractor equipped with a three-way inlet valve and an on/off outlet valve has been used for performing subcritical water extractions (SWE) in a continuous manner for the isolation of the essential oil of fennel, a medicinal plant. The target compounds were removed from the aqueous extract by a single extraction with 5 ml hexane, determined by gas-chromatography-flame ionization (GC-FID) and identified by mass spectrometry (MS). The proposed extraction method has been compared with both hydrodistillation and dichloromethane manual extraction. Better results have been obtained with the proposed method in terms of rapidity, efficiency, cleanliness and possibility of manipulating the composition of the extract.

Determination of formaldehyde in liquid, solid and semisolid pharmaceuticals and cosmetics by flow injection-pervaporation.

A spectrophotometric method is proposed for the determination of formaldehyde in liquid, solid and semisolid cosmetic and pharmaceutical samples, employing, for the first time in this field, the coupling of a continuous flow configuration to a pervaporation unit. The method is based on the reaction of the analyte with pararosaniline in acidic medium and subsequent formation of a coloured product (alkylsulfonic acid chromophore) with sodium sulfite, which was monitored spectrophotometrically. The method was applied to samples in which the formaldehyde content is regulated by law.

Fully automated determination of vitamins A and E in milk-based products using a robotic station-HPLC arrangement.

An automated method, which includes an extraction procedure based on the AOAC official method of analysis for vitamins A and E in milk-based infant formula, was developed. The whole procedure is carried out automatically in a robotic station coupled to a liquid chromatograph with a UV detector for individual separation and quantification of the vitamins. Different commercial products (milk, infant formula and nutritional supplements) were analysed, and the data were compared with those obtained using the manual AOAC extraction method. Relative standard deviations using the automated method were 5.92 and 2.57% for vitamin A and E, respectively.

Determination of selenium in nutritional supplements and shampoos by flow injection-hydride generation-atomic fluorescence spectrometry.

A method for the determination of Se in pharmaceutical samples (nutritional supplements and shampoos) is proposed. The method involves two steps: (1) digestion of the samples and reduction of all forms of Se to Se(IV), which is complete in only 10 min by the use of a focused microwave digestor; and (2) continuous derivatisation (hydride formation) and spectrometry detection by atomic fluorescence. The method can be applied over a wide range of concentrations (0.3-1300 ng ml(-1) of Se) with good repeatability (RSD values lower than 4.6%). The method has been applied successfully to a reference material, and two different types of pharmaceuticals (namely, five different nutritional supplements-with Se present as sodium selenite and Se-methionine-and two shampoos, with selenium sulphide), in agreements with the certified and nominal values, respectively. Yields ranged between 86.5 and 104.8%, and good precision (RSD values lower than 4.2%) were obtained in all instances.

Development and validation of a flow-injection method for the determination of albumin tannate, the active component of a pharmaceutical preparation.

A flow-injection analysis method for the determination of albumin tannate in tablets is reported. After optimization of the variables involved, the method has been characterized and validated in terms of calibration using three procedures: repeatability and reproducibility; ruggedness; and selectivity. Finally, it has been applied to real samples (tablets).