Mª.J del Nozal

Analysis of pesticide residues in wine by solid-phase extraction and gas chromatography with electron capture and nitrogen-phosphorus detection.

A feasible and reproducible method for multiresidue analysis of several common pesticides, of different polarities, in wine samples is proposed. The method combines a solid-phase extraction on polymeric cartridges eluted with ethyl acetate and a gas chromatographic determination using electron capture and nitrogen-phosphorus detection. To avoid the matrix effect, previous washing of the cartridges with a mixture of water-2-propanol (90:10) and further clean-up of the extract on Florisil cartridges, together with a calibration using spiked extracts, are recommended.

Solid-phase microextraction applied to the analysis of pesticide residues in honey using gas chromatography with electron-capture detection

The possibilities of using solid-phase microextraction to determine residues of pesticides in honey have been examined. For this purpose, three types of fiber have been assayed: polyacrylate of 85 microns thickness, and polydimethylsiloxane of 7 and 100 microns thickness. They have been applied to the extraction of 21 pesticides of different chemical families. The effects of the temperature, extraction time and ionic strength on the microextraction have been studied, proposing the most adequate for each fiber. Under optimized conditions, precision, intervals of linearity and detection limits were evaluated.

Determination of rotenone residues in raw honey by solid-phase extraction and high-performance liquid chromatography.

A method for determining residues of the insecticide rotenone in raw-honey by high-performance liquid chromatography (HPLC) is described. To extract the residues, organic solvents such as ethyl acetate, n-hexane/dichloromethane and solid-phase extraction with octadecylsilane cartridges or Florisil packed columns were tested. Determination was carried out by reversed-phase HPLC using acetonitrile-buffer phosphate (pH 7) (60:40, v/v) as mobile phase and detection at 210 nm. Although the data showed that the two extraction methods were able to isolate the pesticide residues, the extraction on octadecylsilane cartridges was preferred due to its simplicity and higher recovery. Recoveries depended strongly on the fortification level for the two extraction procedures. Practical determination limits of 0.015 mg/kg were obtained. In the analysis of honeys, from beehives treated with rotenone at therapeutical doses for 1 month, residual amounts below 0.2 mg/kg were found.

Gas chromatography with electron-capture and nitrogen–phosphorus detection in the analysis of pesticides in honey after elution from a Florisil column: Influence of the honey matrix on the quantitative results

A modified procedure to extract pesticides from honey samples that involves loading the honey onto a Florisil packed column and subsequently eluting it with an n-hexane-dichloromethane mixture is proposed. Anomalous high gas chromatographic responses and subsequently very high recoveries for the pesticides in the extracts were obtained by a conventional calibration with pesticide solutions in organic solvent. This effect was attributed to the honey matrix and can be circumvented by using spiked honey extracts as calibration standards.

Extraction of thymol, eucalyptol, menthol, and camphor residues from honey and beeswax. Determination by gas chromatography with flame ionization detection.

A gas chromatographic method to determine thymol, eucalyptol (cineole), menthol and camphor residues in honey and beeswax is proposed. To isolate the compounds, three methods involving liquid-liquid extraction with methylene chloride, distillation, or solid-phase extraction on octadecylsilica cartridges can be used. The GC separation is carried out on a 60 m x 0.53 mm Stabilwax DA capillary column, using a flame ionization detector. The method is applied to the analysis of natural honey and also honey and beeswax samples from beehives treated with the above compounds.

High Performance Liquid Chromatographic Determination of Organic Acids in Honeys from Different Botanical Origin

A high performance liquid chromatographic method for the determination of organic acids in honeys, is reported. The components were removed from the matrix by solid-phase extraction with anion exchange cartridges and subsequently separated using two chromatographic systems. The chromatographic separation of the acids was achieved by means of an Organic Acids column, using sulfuric acid as mobile phase. To confirm the identification of the acids two Spherisorb ODS-1 S5 columns connected in series were also used, the mobile phase was ammonium dihydrogen phosphate pH=2.2. The compounds were detected with a UV-Vis detector (210nm). The proposed procedure has been applied to determine several organic acids (pyruvic, citric, galacturonic, gluconic, citramalic, glycolic, formic, acetic, butyric, tartaric, malonic, malic, quinic, fumaric, succinic, lactic and propionic) in honey samples from different botanical origin.

Sample preparation methods to analyze fipronil in honey by gas chromatography with electron-capture and mass spectrometric detection☆

Several sample preparation methods have been assayed to analyze residues of fipronil in honey. After diluting the honey, liquid-liquid extraction (LLE) with organic solvents, and solid-phase extraction (SPE) on commercial cartridges or Florisil-packed column have been tested at three concentration levels: 0.01, 0.1 and 1 mg/kg. LLE with n-hexane or SPE on a Florisil column resulted to be the most suitable procedures to analyze fipronil at trace concentrations. Fipronil was quantified by gas chromatography (GC) with electron-capture detection (ECD) or mass spectrometric (MS) detection after conventional or matrix-matched calibration. The detection limit of fipronil in honey samples was below 1 microg/kg. The degradation of fipronil in honey has also been studied, being identified three minor degradation products in the extracts.

Quantitation of active ingredients and excipients in nasal sprays by high-performance liquid chromatography, capillary electrophoresis and UV spectroscopy

A study on the use of different analytical methodologies to determine active ingredients and excipients found in commercial nasal sprays is presented. Two of the developed methodologies consisted of separation techniques, i.e. high-performance liquid chromatography and capillary electrophoresis, and the third one involved a UV-spectroscopic multicomponent procedure. The samples studied are characterized by a high viscosity and the existence of a large number of particles in suspension; therefore, special emphasis is paid on the sample preparation required by each methodology. Advantages and drawbacks of each analytical technique are also discussed in terms of speed of analysis, sensitivity and reproducibility. From this work it is observed that although the UV method needs the most laborious sample preparation, the total time required per analysis is the shortest one. The best reproducibility in terms of analysis time and quantitation of the analyzed compounds is obtained using HPLC. CE allows the determination of more components in the same sample.

Possibilities of gas chromatography-atomic emission detection in pesticide multiresidue. Analysis application to herbicide analysis in soils

The potential of gas chromatography with atomic emission detection (GC-AED) for pesticide multiresidue analysis is explored. Retention data of 181 phytochemicals of diverse properties and considerations about the identification reliability and sensitivity are provided, making a comparison with data obtained by mass spectrometric (MS) detection. The GC-AED system is applied to the determination of 11 herbicides in laboratory-spiked soils after extraction with ethyl acetate. Complementary use of MS is required in order to resolve some peak pairs undiscerned by AED.

Use of supercritical fluid extraction and gas chromatography-mass spectrometry to obtain amino acid profiles from several genetically modified varieties of maize and soybean

A method using supercritical fluid extraction (SFE) and gas chromatography-mass spectrometry (GC/MS) for obtaining the amino acid profiles of genetically modified maize and soybean is proposed. SFE is carried out in a homemade modular system where amino acids are extracted with carbon dioxide modified with 35% of methanol, in conditions optimized by a central composite design. Once extracted, the amino acids are determined by GC/MS. The method has been applied to three samples of maize derived from MON810, other from NK 603 and a Roundup ready soybean sample. The profiles are compared with those obtained from their corresponding isogenic non-transgenic varieties. Although differences are directly observed in some cases by visual comparison of the chromatograms, the application of ANOVA shows more significant differences. In general terms, isogenic varieties seem to have higher content of several amino acids.