Influence of para-aminohippuric acid analysis on net portal-drained viscera flux of nutrients in pigs.

In nutrition studies, para-aminohippuric acid (PAH) is a marker frequently used to measure blood flow in pigs, which is essential for estimating portal-drained viscera (PDV) flux of nutrients. The aim of this study was to evaluate the PAH analytical method by means of qualimetric statistical procedures to estimate the matrix effect and the accuracy and limits of quantitation of the method. Net PDV flux of nutrients was determined in five multi-catheterized pigs using water, plasma or commercial serum as standard matrix. A proportional systematic error due to matrix effect was found for plasma and serum. Mean recovery was 99.4%, and intra- and inter-day precision of the method was 2.4% and 3.8% relative standard deviation, respectively. The limit of quantification was 0.22 mg PAH/l. Use of water for the PAH standard curves underestimated portal blood flow compared with PAH standards prepared with plasma or commercial serum (706, 954 and 927 ml/min; P<0.05, respectively). Consequently, PDV O2 consumption, glucose and amino acids fluxes were underestimated by 33% (P<0.001). In conclusion, our results stress the importance of using plasma from pigs not infused with PAH or alternatively commercial pig serum to prepare PAH standards to determine blood flow in pigs to avoid underestimation of blood flow.

Triacylglycerols Determination by High-temperature Gas Chromatography in the Analysis of Vegetable Oils and Foods: A Review of the Past 10 Years.

The analysis of triacylglycerols by high-temperature gas chromatography, along the last 10 years has been reviewed in this paper. The interest in this topic has grown along the last years due to the triacylglycerols are the main components of oils and fats and they are being used for the characterization and authentication of foods products. The most commonly used procedures, including the official methodologies, applying high-temperature gas chromatographic techniques are shown. Their importance in the characterization of different kind of samples, vegetable oils, seeds, dairy products, etc., is considered. This review is not intended to be a comprehensive dissertation on the field of triacylglycerols analysis since that would require sufficient space to occupy a book in its own right. Rather, it will outline selected considerations and developments, where the technique has been applied.

Application of selected ion monitoring to the analysis of triacylglycerols in olive oil by high temperature-gas chromatography/mass spectrometry.

The analysis of the triacylglycerol (TAG) composition of oils is a very challenging task, since the TAGs have very similar physico-chemical properties. In this work, a high temperature-gas chromatographic method coupled to electron ionization-mass spectrometry (HT-GC/EI-MS), in the Selected Ion Monitoring (SIM) mode, method was developed for the analysis of TAGs in the olive oil; this is a method suitable for routine analysis. This method was developed using commercially available standard TAGs. The TAGs studied were separated according to their equivalent carbon number and degree of unsaturation. The peak assignment was carried out by locating the characteristic fragment ions having the same retention time on the SIM profile such as [RCO+74](+) and [RCO+128](+) ions, due to the fatty acyl residues on sn-1, sn-2 and sn-3 positions of the TAG molecule and the [M-OCOR](+) ions corresponding to the acyl ions. The developed method was very useful to eliminate the interferences that appeared in the mass spectrum since electron ionization can prevent satisfactory interpretation of spectra.

Improvement in LC-MS calibration by addition of fragment signals.

Liquid chromatography-mass spectrometry has become a powerful analytical tool, with high selectivity and sensitivity. Usually in this technique, the calibration function is estimated from the molecular peak signal. This report describes the improvement in sensitivity when the signals from several fragments in addition to the molecular peak are used to establish the calibration function. The influence of the dwell time has also been analysed as an important instrumental parameter that influences the signal range, and consequently, the sensitivity. The calibration function obtained by adding fragment signals was used to estimate the instrumental detection limit using three different procedures, comparing and discussing the results obtained.

Use of solid-phase microextraction followed by on-column silylation for determining chlorinated bisphenol A in human plasma by gas chromatography-mass spectrometry.

In this study, a solid-phase microextraction (SPME) method based on poly(acrylate)-coated fibres has been developed for detection and quantification of chlorinated bisphenol A in human plasma due to the need for an assessment of human exposure to them. After desorption of the analytes for 7 min at 300 degrees C, they were directly derivatized in the GC injector port by injection of 2 microL of diluted bis(trimethylsilyl)trifluoroacetamide (BSTFA). The formation of trimethylsilylate derivatives improves the selectivity, sensitivity and performance of the chromatographic properties obtained when the analytes are directly separated. Quantification was carried out using single-ion monitoring (SIM). The respective chloroderivative molecular ions appear at 406, 440, 474 and 508 m/z; whereas the base peaks corresponding to a loss of a methyl group in all cases appear at 391, 425, 459 and 493 m/z for mono-, di-, tri- and tetrabisphenol A, respectively. Deuterated bisphenol A (BPA-d16) was used as an internal standard. The method was applied to the determination of Cl-BPA, Cl2-BPA, Cl3-BPA and Cl4-BPA at very low concentration levels in plasma. Recovery efficiencies were close to 100% in all cases.

Setting up of recovery profiles: A tool to perform the compliance with recovery requirements for residue analysis.

The use of the recovery term has presented some confusion in Analytical Chemistry. Recent IUPAC recommendations propose to distinguish between two terms: recovery or recovery factor, Re, and apparent recovery, Re*. Apparent recovery includes recovery factor and a new recovery term proposed in this paper, named calibration recovery, Re(C), which depends of the type of systematic error due to the matrix effect (constant and/or proportional) and is related to the applied calibration methodology. This paper highlights the dependence of the calibration recovery on the sample analyte concentration and, for extension, of the apparent recovery, defines the recovery profile, and makes evident the need to determine a "fit for purpose" analyte concentration interval to comply with a regulated recovery requirements. An approach to estimate the calibration recovery and its associated uncertainty in relation to the above-mentioned dependence is presented. The usefulness of the proposed methodology has been shown in the quantification of a pesticide by GC-ECD for assessing dermal exposure.

Efectos de la deambulación durante el parto en gestantes con analgesia epidural / No disponible

Objetivo: Conocer el efecto de la de ambulación durante el parto en la duración del expulsivo, tipo de parto y satisfacción materna en gestantes con analgesia epidural frente a la posición de decúbito supino o lateral. Personas y métodos: El diseño del estudio es cuasiexperimental, con grupo control y sin asignación aleatoria. Se seleccionaron 58 mujeres que recibieron analgesia epidural efectiva y sin complicaciones, nulíparas, presentación cefálica, gestación única, a término y sin enfermedad. La técnica de muestreo fue consecutiva y se dividieron en dos grupos: grupo 1, gestantes que se levantaron (deambularon), y grupo 2, gestantes que no se levantaron (permanecieron en la cama). Se midieron las variables: tiempo de expulsivo, tipo de parto, sensación de pujo y satisfacción materna. Resultados: La mediana del tiempo de de ambulación fue de 120 minutos (mín.= 30; máx.= 360). La mediana de la duración del periodo expulsivo en las mujeres que se levantaron fue de 50 minutos (mín.= 0; máx.= 155) y en el otro grupo de 100 (mín.= 12; máx.= 250); siendo esta diferencia estadísticamente significativa. En el resto de las variables no se encontraron diferencias significativas desde el punto de vista estadístico. Conclusión: La de ambulación, con analgesia epidural durante el parto acorta el tiempo de expulsivo (AU)

Objective: The purpose of this study was to compare the effect of ambulation with epidural analgesia versus supine or lateral position during labor in terms of the duration of labor, mode of labor and maternal satisfaction. Material and methods: This nonrandomized study involved a quasi-experimental research design with a control group. We selected 58 consecutive women meeting the following criteria: effective epidural analgesia without complications, primipara, cephalic presentation, singleton fetus, full-term pregnancy and no evidence of disease. The women were divided in two groups: ambulation (group 1) and supine or lateral position (group 2). The duration of labor, mode of delivery, presence of pain during labor and maternal satisfaction were measured. Results: The median duration of ambulation was 120 minutes (range: 30 to 360 minutes). The median duration of delivery was 50 minutes in group 1 (range: 0 to 155 minutes) and 100 minutes in group 2 (range: 12 to 250 minutes), a difference that was statistically significant. No statistically significant differences were observed in the other variables. Conclusion: Ambulation with epidural analgesia during labor shortens the duration of labor (AU)

Determination of bisphenol A in water by micro liquid-liquid extraction followed by silylation and gas chromatography-mass spectrometry analysis.

A method for the determination of bisphenol A according to the European Union guideline, which establishes a limit of 0.1 ng/mL for organic pollutants in water, is proposed. The method involves a micro liquid-liquid extraction using dichloromethane followed by a silylation step. Identification and quantitation are performed with gas chromatography-mass spectrometry, using an HP-5MS column. The retention time is 7.02 min. Quantitation is carried out using single-ion monitoring (SIM) at m/z 73, 357, and 372. A clean-up is not necessary using SIM mode. Deuterated anthracene (2H10-anthracene) is used as an internal standard. The method is applied to the determination of bisphenol A at very low concentration levels (10.0-250.0 ng/L) in different types of natural water samples. The detection limit obtained is 0.4 ng/L. Recovery efficiencies are close to 100% in all cases.

On the estimate of capillary electrophoresis blanks: application to detection limits evaluation as recommended by IUPAC.

A new method to obtain the signal associated with an electrophoretic blank is presented to be included in the calibration procedures. The signal assigned to the blank is obtained by direct integration of the background noise using extrapolated values of the base-peak width at different concentrations in order to obtain the zero concentration. Detection limits that are better adjusted to a statistical evaluation are thus implemented, as recommended by the International Union of Pure and Applied Chemistry (IUPAC). The detection limit has been examined for a series of linear alkyl benzenesulfonates (C10-C13) and total linear alkyl benzenesulfonates that are widely used in many different commercial products.