Collision cross section (CCS) database: an additional measure to characterize steroids.

Posted on 10 May, 2018 by fqm302

Ion mobility spectrometry enhances the performance characteristics of liquid chromatography–mass spectrometry workflows intended to steroid profiling by providing a new separation dimension and a novel characterization parameter, the so-called collision cross section (CCS). This work proposes the first CCS database for 300 steroids (i.e., endogenous, including phase I and phase II metabolites, and exogenous synthetic compounds), which involves 1080 ions and covers the CCS of 127 androgens, 84 estrogens, 50 corticosteroids, and 39 progestagens. This large database provides information related to all the ionized species identified for each steroid in positive electrospray ionization mode as well as for estrogens in negative ionization mode. CCS values have been measured using nitrogen as drift gas in the ion mobility cell. Generally, direct correlation exists between mass-to-charge ratio (m/z) and CCS because both are related parameters. However, several steroids mainly steroid glucuronides and steroid esters have been characterized as more compact or elongated molecules than expected. In such cases, CCS results in additional relevant information to retention time and mass spectral data for the identification of steroids. Moreover, several isomeric steroid pairs (e.g., 5β-androstane-3,17-dione and 5α-androstane-3,17-dione) have been separated based on their CCS differences. These results indicate that adding the CCS to databases in analytical workflows increases selectivity, thus improving the confidence in steroids analysis. Consequences in terms of identification and quantification are discussed. Quality criteria and a construction of an interlaboratory reproducibility approach are also reported for the obtained CCS values. The CCS database described here is made publicly available.

Posted in Ion mobility, Steroids | Tagged | Comments Off on Collision cross section (CCS) database: an additional measure to characterize steroids.

Optimization of a modified QuEChERS method for the determination of tetracyclines in fish muscle by UHPLC–MS/MS.

Posted on 20 March, 2018 by fqm302

In this work a sample treatment based on a modified QuEChERS method combined with ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) was proposed to determine the residues of five common tetracyclines in fish muscle samples. The separation was achieved in less than 4 min and the analytes were detected in electrospray ionization in positive mode (ESI+) with multiple reaction monitoring mode. Parameters affecting the extraction step, such as the amount of sample and EDTA-McIlvaine buffer and extraction solvent volumes, were optimized by means of experimental design. In order to obtain the lowest matrix effect, parameters affecting the clean-up step by dispersive solid phase extraction (dSPE), were also studied. Under optimum conditions, matrix effect was lower than │15│% in all cases. Limits of quantification were lower than 4.4 μg kg−1 for the compounds in the selected samples, being in compliance with the current legislation. The precision, expressed as relative standard deviation, was below 18.5% and the recoveries for fortified fish samples (salmon and panga) higher than 80%. These results revealed that the proposed method is simple, rapid, cheap and environmentally friendly, being successfully applicable for the determination of these residues in fish samples.

Posted in Mass spectrometry, Panga, QuEChERS, Salmon, Tetracyclines, UHPLC | Tagged , , | Comments Off on Optimization of a modified QuEChERS method for the determination of tetracyclines in fish muscle by UHPLC–MS/MS.

Ultra-high performance liquid chromatography with fluorescence detection following salting-out assisted liquid–liquid extraction for the analysis of benzimidazole residues in farm fish samples

Posted on 14 March, 2018 by fqm302

Ultra-high performance liquid chromatography (UHPLC) coupled with fluorescence detection (FL) has been proposed for the first time to determine thirteen benzimidazoles (BZs) in farmed fish samples. In order to optimize the chromatographic separation, parameters such as mobile phase composition and flow rate were carefully studied, establishing a gradient mode with a mobile phase consisted of water (solvent A) and acetonitrile (solvent B) at a flow rate of 0.4 mL/min. The separation was performed on a Zorbax Eclipse Plus RRHD C18 column (50 × 2.1 mm, 1.8 μm), involving a total analysis time lower than 12 min. Salting-out assisted liquid-liquid extraction (SALLE) was applied as sample treatment to different types of farmed fish (trout, sea bream and sea bass). To obtain satisfactory extraction efficiencies for the studied analytes, several parameters affecting the SALLE procedure were optimized including the amount of sample, type and volume of the extraction solvent, and the nature and amount of the salt used. Characterization of the method in terms of performance characteristics was carried out, obtaining satisfactory results for the linearity (R2 ≥ 0.997), repeatability (RSD ≤ 6.1%), reproducibility (RSD ≤ 10.8%) and recoveries (R ≥ 79%; RSD ≤ 7.8%). Detection limits between 0.04–29.9 μg kg−1 were obtained, demonstrating the applicability of this fast, simple and environmentally friendly method.

Posted in AGL2015-70708-R, Anthelmintic, Aquaculture products, Benzimidazoles, Fluorescence, P12-AGR-1647, SALLE, Sea bass, Sea bream, Trout, UHPLC | Tagged , , | Comments Off on Ultra-high performance liquid chromatography with fluorescence detection following salting-out assisted liquid–liquid extraction for the analysis of benzimidazole residues in farm fish samples

Simple and rapid determination of 5-nitroimidazoles and metabolites in fish roe samples by salting-out assisted liquid-liquid extraction and UHPLC-MS/MS.

Posted on 23 February, 2018 by fqm302

A novel multiresidue method is proposed for the determination of 12 5-nitroimidazoles and their metabolites in fish roe samples using UHPLC-MS/MS. A salting-out assisted liquid-liquid extraction procedure was performed prior to sample analysis. The separation of compounds was accomplished using a C18 Zorbax Eclipse Plus column (50 mm × 2.1 mm, 1.8 µm) at 25 °C and a mobile phase consisting of 0.025% (v/v) aqueous formic acid and pure MeOH at a flow rate of 0.5 mL/min. Parameters involved in ionization and fragmentation were also optimized. The method was characterized in terms of linearity (R2 ≥ 0.9992), extraction efficiency (≥68.9%), repeatability (RSD ≤ 9.8%), reproducibility (RSD ≤ 13.9%) and trueness (recoveries ≥81.4%). Decision limits (CCα) and detection capabilities (CCβ) were obtained in the ranges 0.1–1.0 and 0.2–1.7 µg/kg, respectively.

Posted in 5-nitroimidazoles, Fish roe, Mass spectrometry, P12-AGR-1647, SALLE, UHPLC | Tagged , , | Comments Off on Simple and rapid determination of 5-nitroimidazoles and metabolites in fish roe samples by salting-out assisted liquid-liquid extraction and UHPLC-MS/MS.

Determination of tetracyclines in human urine samples by capillary electrophoresis in combination with field amplified sample injection.

Posted on 9 November, 2017 by fqm302

A sensitive method using CZE‐UV detection has been developed for the determination of five tetracycline antibiotics in human urine samples. To improve the sensitivity of the method, an on‐line preconcentration strategy, named field‐amplified sample injection, has been developed, based on the electrokinetic injection of the sample, which requires only a 1:100 dilution with sample solvent before injection. Under optimum conditions, sensitivity enhancement factors ranged from 450 to 800 for the studied compounds. The applicability of the proposed method was demonstrated by the determination of these antibiotics in spiked urine samples. The limits of quantification were lower than 0.8 mg/L and the precision (intra‐ and inter‐day), expressed as %RSD was below 14%. Recoveries ranged from 92.1 to 96.7%. Thus, the proposed procedure is a simple, fast and efficient strategy which could be used as therapeutic drug monitoring in human urine samples.

Posted in CZE, Dilute and shoot, FASI, P12-AGR-1647, Tetracyclines, UV-vis, Urine | Tagged , | Comments Off on Determination of tetracyclines in human urine samples by capillary electrophoresis in combination with field amplified sample injection.

Evaluation of a selective approach for the determination of 5-nitroimidazoles in aquaculture products by capillary liquid chromatography using molecularly imprinted solid-phase extraction

Posted on 6 November, 2017 by fqm302

Capillary liquid chromatography with UV detection is proposed for the determination of 5-nitroimidazole residues in aquaculture products. The separation was carried out in a C18 column at 20 °C, using a mobile phase consisting of water and acetonitrile, at 7 μL/min and 320 nm as detection wavelength. Furthermore, full loop injection mode (8 μL) was selected and water was considered as injection solvent. The optimized method was applied to the monitoring of nine 5-nitroimidazoles, including three metabolites, in crab, salmon, prawn, and velvet swimming crab. Molecularly imprinted solid-phase extraction has been evaluated for sample cleanup. The method was characterized in all the matrices in terms of linearity (R2 ≥ 0.9964), precision (repeatability, RSD ≤ 7.9%, and reproducibility, RSD ≤ 11.1%) and trueness (recoveries between 80.4 and 108.7%). Decision limits, CCα, ranging from 0.2 to 1.5 μg/kg and detection capabilities, CCβ, from 0.2 to 1.8 μg/kg, were obtained.

Posted in 5-nitroimidazoles, Aquaculture products, Capillary HPLC, Crab, MIPs, P12-AGR-1647, Prawn, Salmon, Velvet swimming crab | Tagged , , | Comments Off on Evaluation of a selective approach for the determination of 5-nitroimidazoles in aquaculture products by capillary liquid chromatography using molecularly imprinted solid-phase extraction

Determination of Fusarium toxins in functional vegetable milks applying salting-out-assisted liquid–liquid extraction combined with ultra-high-performance liquid chromatography tandem mass spectrometry

Posted on 6 November, 2017 by fqm302

Vegetable milks are considered as functional foods due to their physiological benefits. Although the consumption of these products has significantly increased, they have received little attention in legislation with regard to contaminants. However, they may contain mycotoxins resulting from the use of contaminated raw materials. In this work, ultra-high-performance liquid chromatography tandem mass spectrometry has been proposed for the determination of the most relevant Fusarium toxins (fumonisin B1 and B2, HT-2 and T-2 toxins, zearalenone, deoxynivalenol and fusarenon-X) in different functional beverages based on cereals, legumes and seeds. Sample treatment consisted of a simple salting-out-assisted liquid–liquid extraction with no further clean-up. The method provided limits of quantification between 3.2 and 57.7 µg L−1, recoveries above 80% and precision with RSD lower than 12%. The method was also applied for studying the occurrence of these mycotoxins in market samples of vegetable functional beverages and deoxynivalenol was found in three oat-based commercial drinks.

Posted in AGL2015-70708-R, Mass spectrometry, Mycotoxins, SALLE, UHPLC, Vegetable milks | Tagged , , | Comments Off on Determination of Fusarium toxins in functional vegetable milks applying salting-out-assisted liquid–liquid extraction combined with ultra-high-performance liquid chromatography tandem mass spectrometry

Simple determination of aflatoxins in rice by ultra-high performance liquid chromatography coupled to chemical post-column derivatization and fluorescence detection

Posted on 6 November, 2017 by fqm302

A fast and simple analytical method was developed and characterized for the determination of aflatoxins (B1, B2, G1 and G2) in rice. The procedure is based on a simple solid-liquid extraction without further clean-up, and analysis by ultra-high performance liquid chromatography coupled with fluorescence detection. Fluorescence emission of aflatoxins B1 and G1 was enhanced by post-column chemical derivatization using pyridinium bromide perbromide. The analytical method was satisfactorily characterized in white and brown rice. Under optimum conditions, external calibration in solvent could be used for quantification purposes and limits of quantification were below the maximum contents established by the European Union regulation for these contaminants/commodity group combination (0.07–0.14 µg/kg for white rice and 0.20–0.28 µg/kg for brown rice). Recovery studies carried out at three different concentration levels (0.5, 2 and 5 µg/kg) showed values in the range of 84.5–105.3%, and RSDs ≤ 5%.

Posted in AGL2015-70708-R, Aflatoxins, Fluorescence, Rice, Solid-liquid extraction, UHPLC | Tagged , | Comments Off on Simple determination of aflatoxins in rice by ultra-high performance liquid chromatography coupled to chemical post-column derivatization and fluorescence detection

Fully compatible and ultra-sensitive micellar electrokinetic chromatography-tandem mass spectrometry using sheathless porous-tip interfacing.

Posted on 27 October, 2017 by fqm302

The on-line coupling of micellar electrokinetic chromatography and mass spectrometry (MEKC-MS) is often hampered by incompatibility problems leading to reduced separation performance and unfavorable limits of detection (LODs). Here we propose a new selective and highly sensitive MEKC-MS/MS method employing a sheathless porous-tip interface in combination with a micellar phase comprised of semi-volatile surfactant molecules. Carbamate pesticides (CRBs) were selected as representative model compounds being neutral toxic pollutants potentially present at trace levels in environmental water samples. A background electrolyte of 75 mM perfluorooctanoic acid adjusted to pH 9.0 with ammonium hydroxide allowed efficient separation of 15 CRBs and appeared fully compatible with electrospray ionization (ESI)-MS. Interfacing parameters, such as the distance between the capillary tip and mass-spectrometer inlet, ESI voltage, and dry gas temperature and flow were optimized in order to attain good spray stability and high analyte signal-to-noise ratios. For CRBs the LODs ranged from 0.2 to 3.9 ng L−1 (13 nL injected, i.e., 2% of capillary volume), representing an improvement for certain CRBs of more than 300-fold when compared with conventional sheath-liquid interfacing. Good linearity (R2 > 0.99) and satisfactory reproducibility were obtained for all CRBs with interday RSD values for peak area and migration time of 4.0–11.3% and below 1.5%, respectively. Analysis of spiked mineral water showed that the new MEKC-MS/MS method allows selective and quantitative determination of CRB concentrations below the maximum residue limit of 100 ng L−1 without the need for sample preconcentration.

Posted in Carbamates, MEKC, Mass spectrometry, Water | Tagged , | Comments Off on Fully compatible and ultra-sensitive micellar electrokinetic chromatography-tandem mass spectrometry using sheathless porous-tip interfacing.

A high-throughput UHPLC method for the analysis of 5-nitroimidazole residues in milk based on salting-out assisted liquid–liquid extraction.

Posted on 26 October, 2017 by fqm302

A novel salting-out assisted liquid–liquid extraction (SALLE) method has been developed for the extraction of eight 5-NDZ antibiotics from milk samples prior to their analysis by UHPLC. An exhaustive study of the parameters involved in the SALLE procedure has been carried out, optimizing the extraction solvent volume, the amount of the salt agent, and the centrifugation and vortex timing by an experimental design. After sample treatment, the obtained extract was reconstituted in the mobile phase (6:94 (v/v) acetonitrile/water containing 0.1% (v/v) of formic acid) and analyzed by the proposed UHPLC-UV method. Separation was accomplished in a C18 Zorbax Eclipse Plus (50 mm × 2.1 mm, 1.8 μm) column at 45 °C within 8 min. Gradient mode was considered using a mobile phase consisting of 0.1% (v/v) formic acid aqueous solution and acetonitrile containing 0.1% (v/v) formic acid at a flow rate of 0.45 mL/min. Analytical signals were monitored at 320 nm. Matrix-matched calibration curves showed satisfactory linearity (R2 ≥ 0.996). LODs, ranging from 2 to 4 μg/L, were achieved and precision studies showed RSDs lower than 12.8% in terms of peak height. Additionally, recoveries higher than 62.8% were obtained for all studied compounds in milk samples.

Posted in 5-nitroimidazoles, Milk, P12-AGR-1647, SALLE, UHPLC, UV-vis | Tagged , , | Comments Off on A high-throughput UHPLC method for the analysis of 5-nitroimidazole residues in milk based on salting-out assisted liquid–liquid extraction.