Negative Matrix Effect Research Articles

Development of a multi-class method for the quantification of veterinary drug residues in feedingstuffs by liquid chromatography-tandem mass spectrometry

A simple multi-residue method was developed for detecting and quantifying 33 analytes from 13 classes of antibiotics (tetracyclines (3), quinolones (7), penicillins (3), ionophore coccidiostats (7), macrolides (3), sulfonamides (1), quinoxalines (2), phenicols (2), lincosamides (1), diaminopyrimidines (1), polypeptides (1), streptogramins (1) and pleuromutilins (1)) in animal feeds. Extraction and clean-up procedures were optimized with spiked piglet feed. Samples were extracted by ultrasonic-assisted extraction with a mixture of methanol/acetonitrile/McIlvaine buffer at pH 4.6 (37.5/37.5/25, v/v/v) containing 0.3% of EDTA-Na 2, followed by a clean up using a dispersive solid-phase extraction (d-SPE) with PSA (primary secondary amine). Detection of antibiotics was achieved by liquid chromatography-electrospray tandem mass spectrometry (LC–ESI-MS/MS) within 28 min using both positive and negative ESI mode. Average recoveries ranged from 51% (oxytetracycline) to 116% (tilmicosin) with associated relative standard deviations of 7.3% and 9.0% and an overall mean of 87%. Limits of quantification ranged from 3.8 ng g −1 (lincomycin) to 65.0 ng g −1 (bacitracin). Following optimization, the method was further verified for bovine and lamb feedingstuffs; negative matrix effects were evaluated and overcome by a standard addition method.

Development of a solid-phase microextraction gas chromatography with microelectron-capture detection method for the determination of 5-bromo-5-nitro-1,3-dioxane in rinse-off cosmetics

5-Bromo-5-nitro-1,3-dioxane (bronidox) is a bromine-containing preservative often used in rinse-off cosmetics but also subjected to several restrictions according to the European Cosmetic Products Regulation. Thus, as a part of a quality control procedure, analytical methods for the determination of this compound in different types of cosmetics are required. In the present work, a solvent-free and simple methodology based on solid-phase microextraction (SPME) followed by gas chromatography with microelectron capture detection (GC-μECD) has been developed and validated for the determination of bronidox in cosmetic samples such as shampoos, body cleansers or facial exfoliants. As far as we know, this is the first application of SPME to this preservative. Negative matrix effects due to the complexity of the studied samples were reduced by dilution with ultrapure water. The influence of several factors on the SPME procedure such as fiber coating, extraction temperature, salt addition (NaCl) and sampling mode has been assessed by performing a 2 4-factorial design. After optimization, the recommended procedure was established as follows: direct solid-phase microextraction (DSPME), using a PDMS/DVB coating, of 10 mL of diluted cosmetic with 20% NaCl, at room temperature, under stirring for 30 min. Using these suggested extraction conditions, linear calibration could be achieved, with limits of detection (LOD) and quantification (LOQ) well below the maximum authorized concentration (0.1%) established by the European legislation. Relative standard deviations (RSD) lower than 10% were obtained for both within a day and among days precision. The method was applied to diverse types of formulations spiked with bronidox at different concentration levels (0.008–0.10%); these samples were quantified by external calibration and satisfactory recoveries (≥70%) were obtained in all cases. Finally, the SPME–GC-μECD methodology was applied to the analysis of several cosmetics labeled or not as containing bronidox. The presence of this preservative in some of these samples was confirmed by GC–MS.

Development of a solid-phase microextraction gas chromatography with microelectron-capture detection method for a multiresidue analysis of pesticides in bovine milk

A simple and rapid method based on solid-phase microextraction (SPME) technique followed by gas chromatography with microelectron-capture detection (GC-μECD) was developed for the simultaneous determination of more than 30 pesticides (pyrethroids and organochlorinated among others) in milk. To our knowledge, this is the first application of SPME for the determination of pyrethroid pesticides in milk. Negative matrix effects due to the complexity and lipophility of the studied matrix were reduced by diluting the sample with distilled water. A 2 5–1 fractional factorial design was performed to assess the influence of several factors (type of fiber coating, sampling mode, stirring, extraction temperature, and addition of sodium chloride) on the SPME procedure and to determine the optimal extraction conditions. After optimization of all the significant variables and interactions, the recommended procedure was established as follows: DSPME (using a polydimethylsiloxane (PDMS)/divinylbenzene (DVB) coating) of 1 mL of milk sample diluted with Milli-Q water (1:10 dilution ratio), at 100 °C, under stirring for 30 min. The proposed method showed good linearity and high sensitivity, with limits of detection (LOD) at the sub-ng mL −1 level. Within a day and among days precisions were also evaluated (R.S.D. < 15%). One of the most important attainments of this work was the use of external calibration with milk-matched standards to quantify the levels of the target analytes. The method was tested with liquid and powdered milk samples with different fat contents covering the whole commercial range. The efficiency of the extraction process was studied at several analyte concentration levels obtaining high recoveries (>80% in most cases) for different types of full-fat milks. The optimized procedure was validated with powdered milk certified reference material, which was quantified using external calibration and standard addition protocols. Finally, the DSPME-GC-μECD methodology was applied to the analysis of milk samples collected in farms of dairy cattle from NW Spain.

Utilização da extração em fase sólida (SPE) na determinação de hidrocarbonetos policíclicos aromáticos em matrizes aquosas ambientais

Polycyclic aromatic hydrocarbons (PAHs) are a great environmental concern mainly because of their toxic, mutagenic and carcinogenic potential. This paper reports utilization of the solid-phase extraction (SPE) technique to determine PAHs in environmental aqueous matrices. The recovery from environmental aqueous matrices fortified with PAHs varied from 63.7 to 93.1% for atmospheric liquid precipitation, from 38.3 to 95.1% for superficial river water, and from 71.0 to 95.5% for marine water. No negative matrix effect was observed for the recovery of PAHs from atmospheric liquid precipitation and marine water, but was observed for superficial river water, particularly for PAHs possessing 5 and 6 aromatic rings.

Development of a multiresidue method for analyzing herbicide and fungicide residues in bovine milk based on solid-phase extraction and liquid chromatography–tandem mass spectrometry

This report describes a liquid chromatography (LC)–tandem mass spectrometry (MS) multiresidue method for determining traces of 30 base/neutral/acid herbicides and fungicides in bovine whole milk. Four milliliters of milk was spiked with the analytes and two surrogate analytes (SAs) and then diluted with 35 mL of a water/methanol solution (50:50, v/v). This mixture was passed through a 0.5-g Carbograph 4™ cartridge. After washings, analytes were re-extracted by back-flushing the cartridge with 1.5 mL of methanol followed by 6 mL of methylene chloride/methanol (80:20, v/v), 50 mmol/L formic acid. After partial solvent removal down to about 0.1, 0.15 mL of 1 mmol/L formic acid aqueous solution and an internal standard (IS) were added. After filtration, 50 μL of the final extract was then introduced into the LC analytical column. During the chromatographic run, the MS system was operated in both positive and negative ion modes. MS data acquisition was performed in the multi-reaction monitoring mode, selecting two precursor ion > product ion transitions for each target compound, except for pentachlorophenol. On analyzing six milk samples from different sources, absolute recovery of the analytes and the two SAs ranged between 78% and 104% with RSDs not larger than 13%. The accuracy of the method at three different spike levels was assessed by adding the two SAs to analyte-containing milk samples and varied between 82% and 120% with RSDs not larger than 11%. Limits of quantification were estimated to range between 0.008 and 1.4 μg/L. Compared to the Carbograph 4 cartridge, one filled with a N-vinylpyrrolidone- m-divinylbenzene co-polymer (Oasis HLB™) sorbent was much less efficient in recovering several of the acidic herbicides considered and, in addition, its relative final extract produced a severe negative matrix effect that drastically weakened ion signal intensities of several non acidic analytes.

Aufreinigung von Fumonisinen und ihren Hydrolysaten über ein neuartiges Festphasenextraktions-Material

Tests with various clean-up materials after optimisation of different parameters showed that the use of Oasis® material resulted in matrixless chromatograms in HPLC-FLD. The selectivity and detection limit of the method was improved by using LC-MS/MS as the detection system. Mean recovery was 100%, and no negative food matrix effects could be observed.