Daniella V. Augusti

Quantitative determination of the enantiomeric composition of thalidomide solutions by electrospray ionization tandem mass spectrometry

Rapid and simple chiral analysis of thalidomide solutions is demonstrated by using electrospray ionization tandem mass spectrometry and analysis of cluster ion dissociation by the kinetic method. Average deviations of 1% between the actual and experimental enantiomeric compositions are observed.

Development and validation (according to the 2002/657/EC regulation) of a method to quantify sulfonamides in porcine liver by fast partition at very low temperature and LC-MS/MS

A novel multi-residue method for the quantification of 15 sulfonamides in porcine liver is described. It involves the application of a liquid-liquid extraction with fast partition at very low temperature (LLE-FPVLT) procedure followed by HPLC-MS/MS (high performance liquid chromatography coupled to tandem mass spectrometry) analysis. By this innovative method, acetonitrile is added to a minced porcine liver sample and the resulting suspension centrifuged and immersed in a container with liquid nitrogen for 15 s. The acetonitrile phase, which remains liquid under these conditions, is isolated, evaporated to dryness, recomposed with formic acid 0.1% v/v, and injected into the liquid chromatograph. The whole analytical procedure was validated according to the European Commission Decision 2002/657/EC and acceptable values (except for sulfanilamide) were obtained for the following parameters: linearity (0.97 < R2 < 0.99), decision limit (107.70 µg kg-1 < CCα < 128.65 µg kg-1), detection capability (115.40 µg kg-1 < CCβ < 157.29 µg kg-1), limit of detection (5.58 µg kg-1 < LOD < 16.75 µg kg-1), limit of quantification (18.41 µg kg-1 < LOQ < 55.26 µg kg-1), accuracy (recovery rates), precision (repeatability, intermediate precision, and measurement uncertainty tests), selectivity, and robustness. Recoveries higher than 70%, at three concentration levels (0.5, 1.0 and 1.5 of the maximum residue limit, MRL), were attained for the majority of the sulfonamides. These very promising results point to the inclusion of the present methodology into the National Residue Control Plan scope of the Ministry of Agriculture, Livestock and Food Supply of Brazil.

Artificially-aged cachaça samples characterised by direct infusion electrospray ionisation mass spectrometry

Direct infusion electrospray ionisation mass spectrometry in the negative ion mode [ESI(-)-MS] was employed to evaluate the authenticity of aged cachaças, a traditional and valuable Brazilian alcoholic beverage prepared from the distillation of brewed sugarcane juice and aged in barrels made of common woods. Counterfeit samples were prepared by adding dyes, sawdust or essences to a freshly-distiled, much less valuable sample (white cachaça) to simulate the 1-2years long natural ageing in wooden barrels. A simple visual inspection revealed remarkable differences between the ESI(-)-MS of the authentic samples (aged in oak or amburana casks) and the artificially-aged counterfeit samples. A set of diagnostic ions were detectable in the ESI(-)-MS of the authentic samples aged in oak (m/z 197, 241, 301 and 307) and amburana (m/z 271 and 377/379). This fast and direct methodology seems useful as a routine procedure to monitor this highly profitable and common counterfeit practice.

Development and validation of an efficient and innovative method for the quantification of multiclass veterinary drugs in milk by using LC–MS/MS analysis

An efficient analytical method for the simultaneous quantification of 27 veterinary drugs from five different classes (benzimidazoles, betalactams, quinolones, sulfonamides and tetracyclines) in bovine milk using a novel extraction procedure (liquid–liquid extraction with fast partition at very low temperature) and liquid chromatography coupled to tandem mass spectrometry is described. The full analytical method was validated according to Brazilian legislation (normative instruction SDA/MAPA 24/2009) and suitable values were achieved for all the parameters evaluated. Hence, the recoveries were within the established ranges (>70%), except for sulfathiazole (67.4% at the 0.5 × MRL level) and marbofloxacin and thiabendazole (112.5 and 114.6% respectively, at the 1.0 × MRL level). The repeatability and intermediate precision for all the analytes, expressed as relative standard deviations, were lower than 20 and 25%, respectively. The decision limits (CCα), detection capabilities (CCβ) and expanded uncertainties were also calculated and satisfactory results were obtained. Finally, the method was applied to 15 actual samples and traces of oxytetracycline and sulfamethazine were detected in three of them.

Quantitative determination of the enantiomeric composition of panthotenic acid solutions: a mass spectrometry experiment

Rapid and quantitative determinations of the enantiomeric compositions of pantothenic acid solutions were carried out by using electrospray ionization tandem mass spectrometry and applying the kinetic method to perform the data analysis. Deviations of ca. 1% between the actual and experimental enantiomeric compositions were observed.

Gas-phase halide affinity of aliphatic alcohols estimated by the kinetic method †

The chloride affinity of ethanol was determined by the kinetic method by examining the dissociation of the [EtOH—Cl—HOR]− dimers (ROH=methanol, 1-propanol, 2-propanol and tert-butanol), generated in the ion source of a triple quadrupole mass spectrometer using chloroform as the chemical ionization reagent. Dimer mass selection and collision-induced dissociation using argon furnished, as products, the two individual alcohol–chloride anionic complexes, i.e. [EtOH+Cl]− and [ROH+Cl]−. The natural logarithm of the ratio of their abundances, i.e. ln ([ROH+Cl]–/[EtOH+Cl]−), correlated linearly with the experimental ROH chloride affinity. Using this linear relationship, the chloride affinity of ethanol is determined to be 43±3 kJ mol−1, which is consistent with the literature value of 43.5±8.4 kJ mol−1. From the slope of the kinetic method plot, an effective temperature of 643 ± 25 K was calculated, suggesting the weakly-bound nature of the cluster ions. The validity of the results was confirmed using the extended version of the kinetic method which showed that there is a negligible difference (–0.06 J mol K−1) in the entropy requirements of the two fragmentation channels. It is also demonstrated that this methodology can be applied to estimate the analogous bromide and fluoride affinities of aliphatic alcohols and to estimate halide affinities not previously known. Thus, these cases constitute additional examples of the advantageous application of the kinetic method in the determination of unknown thermochemical properties. Furthermore, in the dissociation of [EtOH—Cl—HO–CH2–CH2–Y]− cluster ions (Y=F, Cl, OMe and Me), a remarkable linear relationship was observed between the natural logarithm of abundance of product ratios, i.e. ln ([Y–CH2–CH2OH+Cl]−/[EtOH+Cl]−) and the electronegativity of the Y substituent. This is ascribed to the inductive effect in stabilizing the charge on chloride in the cluster ion.

Análise quiral por espectrometria de massas através da utilização do método cinético

Novel and quantitative mass spectrometry methods for rapid and accurate enantiomeric excess determination are presented. These methodologies use electrospray ionization (ESI) and mass spectrometry (MS) to detect and analyze, via collision-induced dissociation (CID), mass-selected transition metal complexes that promote enantio especific interactions. The data from CID are conveniently treated by the kinetic method, a sensitive linear free energy method of treating mass spectrometric results. Four different variations of this methodology are described: single ratio method (SR), quotient ratio method (QR), fixed ligand method (SRfixed), and quotient ratio method with fixed ligand (QRfixed). These individual methods are compared and their main features discussed in detail.