Development of a novel UHPLC-MS/MS method for the determination of ochratoxin A in tea.

The mycotoxin Ochratoxin A (OTA) is responsible for producing many effects on human and animal health. In this work, the evaluation of the presence of OTA in tea beverage samples consisted of extraction and preconcentration through the solidification of a floating organic drop (DLLME-SFO) combined with an additional octadecyl silane clean-up step. The obtained extract was analyzed by UHPLC-MS/MS. Interferences from the matrix were effectively reduced and, consequently, recovery increased from 43.18% ± 4.1%-96.02% ± 2.54%. The validation assays were carried out by external calibration and spiked samples, with satisfactory recoveries. An adequate dynamic calibration range was obtained over a concentration interval between 0.5 and 70 µg mL-1 OTA. Capabilities of detection and quantification were 0.5 and 1.4 µg mL-1. The obtained Green Certificate was compared with other techniques to establish the greenness profile of the procedure. Quantification of ochratoxin A levels in tea samples was performed.

Analytical tools for elucidating the biological role of melatonin in plants by LC-MS/MS.

Melatonin (MT) presence in higher plants was recently discovered and the knowledge of its function in vivo is limited. Several studies have recently shown the occurrence of MT and related compounds in grapes and wines. The analysis of MT in plants and foods represents a highly challenging task due to its wide concentration range, the difficulty in the selection of the extraction solvents because of its amphipathic nature, and the fact that it reacts quickly with other matrix components. Thus, sample processing factors; preparation/cleanup procedures; and chromatographic/detection parameters, such as HILIC and reverse phase (C(8) and C(18)) chromatographic modes, ESI, and atmospheric pressure chemical ionization (APCI) in both negative and positive modes were evaluated. Taken together, we have demonstrated that optimal conditions were quite different for each of the matrices under study. A sonication-mediated extraction step was necessary for grape skin (100% v/v methanol) and plant tissues (50% v/v methanol), while wine and must required a SPE preconcentration step. HILIC-(+) APCI ionization was better for MT standards, while C(8) -(+) APCI was the best choice for grape skin and C(18) -(+ESI) was suitable for wine. On the other hand, C(8) -(+)ESI was the most appropriate for vegetal tissues of Arabidopsis thaliana. Proposed methods were validated and the LODs were in the low picogram levels range. The optimized approaches were applied to the determination of MT and its isomer in different vegetal/food samples; levels found within the range: 4.9-440 ng/g.

The use of electrothermal vaporizer coupled to the inductively coupled plasma mass spectrometry for the determination of arsenic, selenium and transition metals in biological samples treated with formic acid.

A fast method for the determination of As, Co, Cu, Fe, Mn, Ni, Se and V in biological samples by ETV-ICP-MS, after a simple sample treatment with formic acid, is proposed. Approximately 75 mg of each sample is mixed with 5 mL of formic acid, kept at 90°C for 1 h and then diluted with nitric acid aqueous solution to a 5% (v/v) formic acid and 1% (v/v) nitric acid final concentrations. A palladium solution was used as a chemical modifier. The instrumental conditions, such as carrier gas flow rate, RF power, pyrolysis and vaporization temperatures and argon internal flow rate during vaporization were optimized. The formic acid causes a slight decrease of the analytes signal intensities, but does not increase the signal of the mainly polyatomic ions ((14)N(35)Cl(+), (14)N(12)C(+), (40)Ar(12)C(+), (13)C(37)Cl(+), (40)Ar(36)Ar(+), (40)Ar(35)Cl(+), (35)Cl(16)O(+), (40)Ar(18)O(+)) that affect the analytes signals. The effect of charge transfer reactions, that could increase the ionization efficiency of some elements with high ionization potentials was not observed due to the elimination of most of the organic compounds during the pyrolysis step. External calibration with aqueous standard solutions containing 5% (v/v) formic acid allows the simultaneous determination of all analytes with high accuracy. The detection limits in the samples were between 0.01 (Co) and 850 µg kg(-1) (Fe and Se) and the precision expressed by the relative standard deviations (RSD) were between 0.1% (Mn) and 10% (Ni). Accuracy was validated by the analysis of four certified reference biological materials of animal tissues (lobster hepatopancreas, dogfish muscle, oyster tissue and bovine liver). The recommended procedure avoids plasma instability, carbon deposit on the cones and does not require sample digestion.

A novel and rapid method for determination of natamycin in wines based on ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry: validation according to the 2002/657/EC European decision.

A novel, simple, and rapid reversed-phase liquid chromatography-tandem mass spectrometric methodology was developed for the analysis of natamycin in wine samples. Natamycin was protonated to form singly charged ions in an electrospray positive ion mode. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring (MRM) of three fragment ion transitions (666.3 → 648.2, 666.3 → 503.3, and 666.3 → 485.2) to provide a high degree of sensitivity and specificity. Chromatographic separation was performed on a rapid resolution column using a mobile phase consisting of an acetonitrile/water mixture with a total run time of 5.0 min. After only filtration as pretreatment, the sample was injected into the chromatographic system. The proposed method was validated in terms of selectivity, trueness, precision, decision limit (CCα), and detection capability (CCß) according to 2002/657/EC Commission decision. The values for trueness, reported as bias (%), agreed with those established by the aforementioned document. Repeatability (intraday variability) values were 12.37% at a concentration of 1.0 µg L(-1) and 8.99-4.19% at concentrations between 2.5 and 10 µg L(-1). The overall within-laboratory (interday variability) reproducibility was 15.47% at a concentration of 1.0 µg L(-1), which was significantly lower than the indicative value reported in the EU decision. The results indicated that the proposed approach is a sensitive, fast, reproducible, and robust methodology suitable for the analysis of natamycin levels in wine samples.

On-line solid phase extraction CZE for the simultaneous determination of lanthanum and gadolinium at picogram per liter levels.

A non-specific on-line method is presented for the extraction and preconcentration of two rare earth elements using a microcartridge containing C(18)-derivatized silica particles prior to their analysis by CZE. The microcartridge, named analyte concentrator, was coupled on-line to the inlet of the separation capillary (fused-silica (FS) capillary, 75 microm id x12 cm from the inlet to the microcartidge and 37 cm from the microcartridge to the detector). The reversed-phase sorbent quantitatively retained gadolinium (Gd) and lanthanum (La) as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes in the presence of non-ionic micelles of polyethylene glycol tert-octylphenyl ether, enabling sample clean-up and concentration enhancement with minimum sample handling. The rare earth elements chelates were released from the sorbent with methanol and then analyzed by CZE with diode array detection. A background electrolyte of 20 mM sodium tetraborate containing 8% ACN, pH 9.0, was found to be optimal for the separation of metal chelates. The concentration limits of detection were lowered to picogram per liter levels (20 pg/L for La and 80 pg/L for Gd). A 1000-fold improvement in concentration sensitivity for La- and Gd-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes with respect to CZE without preconcentration was reached.

Simultaneous determination of dysprosium and iron in urine by capillary zone electrophoresis coupled to cloud point extraction.

Automated preconcentration strategies are needed when analyzing metals in real samples by capillary electrophoresis (CE) with UV detection. The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) associated with CE for simultaneously determining dysprosium and iron at ppb levels in urine is presented and evaluated for the first time. The preconcentration step is mediated by micelles of the non-ionic surfactant polyethyleneglycol-mono-p-nonylphenylether (PONPE 7.5) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 8 mlmin(-1), and the surfactant rich-phase was retained in a microcolumn packed with cotton, at pH 9.2. The surfactant-rich phase was eluted with 50 microl acetonitrile directly into the CE sample vial, allowing to reach an enrichment factor of 200-fold for a 10 ml sample urine. The type and composition of the background electrolytes (BGE) were investigated with respect to separation selectivity, reproducibility and stability. A BGE of 20mM sodium tetraborate buffer containing 13% acetonitrile, pH 9.0 was found to be optimal for the separation of metal chelates. Detection was performed at 585 nm. An enhancement factor of 200 was obtained for the preconcentration of 10 ml of sample solution. The detection limits for the preconcentration of 10 ml of urine were 0.20 microgl(-1) for Dy, and. 0.48 microgl(-1) for Fe. The calibration graphs using the preconcentration system were linear with a correlation coefficient of 0.9989 (Dy) and 0.9976 (Fe) at levels near the detection limits up to at least 500 microgl(-1). The method was successfully applied to the determination of dysprosium and iron in urine for monitoring the elimination of dysprosium-based pharmaceuticals.