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Polar lipids, especially glycerophospholipids, constitute the main components of cell membranes and are precursors of signaling molecules in many cellular and physiological processes. For this reason, the development of methods with high capability for detection of polar lipids in biological samples is required. In this research, the objective was to develop a method for comprehensive qualitative/quantitative determination of polar lipids in plasma by a combination of acquisition methods with a triple quadrupole mass analyzer. The strategy was optimized in two steps: (a) a first step for detection of lipids by monitoring selective fragmentation patterns representative of each lipid family and (b) a second step for confirmation of lipid species by detection and identification of product ions associated with the conjugated fatty acids. The acquisition list was divided into two multiple reaction monitoring (MRM) methods to ensure the detection of all transitions with suited instrumental sensitivity according to chromatographic retention time and relative abundance in plasma. The combination of the two MRM methods allowed the detection of 398 polar lipids in plasma in 64 min. Precision, estimated as within-day variability, was below 6.8% for all determined lipid families, while between-day variability was below 24.0%. This strategy has been applied to a cohort formed by 384 individuals in order to obtain a qualitative and quantitative distribution of polar lipids in human plasma. The most concentrated lipid families in relative terms were lysophospholipids, plasmalogens, and phosphatydilcholines, with mean relative concentration of 58.0, 17.1, and 8.3%, respectively. Then, sphingomyelins and phosphatidylethanolamines reported a relative concentration of 2.0%, followed by phosphatidylserines, with 1.1%. [ABSTRACT FROM AUTHOR]

A simple method for the simultaneous determination of glufosinate and its metabolites in plants based on liquid chromatography-ultraviolet (LC-UV) absorption detection after derivatization with fluorenylmethoxycarbonyl chloride (FMOC-Cl) of some analytes to facilitate separation is reported here. Nonavailable standard metabolites were identified by LC-TOF/mass spectrometry (MS), which also confirmed all target analytes. Ultrasound-assisted extraction was used for sample preparation (power of 70 W and duty cycle of 0.7 s/s for 10 min) with subsequent evaporation of the extractant, reconstitution and filtration as the cleanup/concentration step prior to derivatization, and chromatographic separation and detection at 270 nm for underivatized analytes and 340 nm for those that were derivatized. The chromatographic analysis was completed in 40 min using a Luna ® column (C18 phase). The analytical characteristics of the method were linear dynamic range of the calibration curves within 0.047-700 μg/mL with a regression coefficient (rc) of 0.999 for glufosinate, 0.077-700 μg/mL with a rc of 0.998 for N-acetyl-glufosinate, and 0.116-600 μg/mL with a rc of 0.998 for 3-(methylphosphinico)propanoic acid. The precision for the determination of glufosinate (studied at two levels, 0.1 and 5 μg/mL) was 2.7 and 6.0 % for repeatability and 4.7 and 7.2 % for within-laboratory reproducibility, respectively. Identification and confirmatory analysis of the presence of glufosinate and metabolites in the extracts from treated plants was carried out by LC-TOF/MS in high-resolution mode for the precursor ion. The method was validated by analyzing wheat ( Triticum aestivum) samples (resistant and susceptible biotypes) treated with 300 g of glufosinate/ha following conventional agronomical practices. [ABSTRACT FROM AUTHOR]

In this study, levels of esterified and nonesterified fatty acids (EFAs and NEFAs, respectively) were compared in obese individuals (body mass index between 30 and 47 kg m) in basal state and after intake of four different breakfasts prepared with oils heated at frying temperature. The target oils were three sunflower oils-pure, enriched with dimethylsiloxane (400 μg mL) as lipophilic oxidation inhibitor, and enriched with phenolic compounds (400 μg mL) as hydrophilic oxidation inhibitors-and virgin olive oil with a natural content of phenolic compounds of 400 μg mL. The intake of breakfasts was randomized to avoid trends associated to this variability source. EFAs and NEFAs were subjected to a sequential derivatization step for independent gas chromatography-mass spectrometry analysis of both fractions of metabolites in human serum. Derivatization was assisted by ultrasonic energy to accelerate the reaction kinetics, as required for high-throughput analysis. Statistical analysis supported on univariate (multifactor ANOVA) and multivariate approaches (principal component analysis and partial least squares-discriminant analysis) allowed identification of the main variability sources and also discriminating between individuals after intake of each breakfast. Individuals' samples after intake of breakfasts prepared with virgin olive oil were clearly separated from those who ingested the remaining breakfasts. The main compounds contributing to discrimination were omega-3 and omega-6 EFAs with special emphasis on arachidonic acid and eicosapentaenoic acid. These two polyunsaturated fatty acids are the precursors of eicosanoid metabolites, which are of vital importance as they play important roles in inflammation and in the pathogenesis of vascular and malignant diseases as cancer. [ABSTRACT FROM AUTHOR]

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection. A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the main area of application. In sample preparation ultrasound is used to assist solid-sample treatment (e.g. digestion, leaching, slurry formation) and liquid-sample preparation (e.g. liquid–liquid extraction, emulsification, homogenization) or to promote heterogeneous sample treatment (e.g. filtration, aggregation, dissolution of solids, crystallization, precipitation, defoaming, degassing). Detection techniques based on use of ultrasonic radiation, the principles on which they are based, responses, and the quantities measured are also discussed. [ABSTRACT FROM AUTHOR]

A study of the feasibility of Fourier transform medium infrared spectroscopy (FT-midIR) for analytical determination of fatty acid profiles, including trans fatty acids, is presented. The training and validation sets—75% (102 samples) and 25% (36 samples) of the samples once the spectral outliers have been removed—to develop FT-midIR general equations, were built with samples from 140 commercial and home-made bakery products. The concentration of the analytes in the samples used for this study is within the typical range found in these kinds of products. Both sets were independent; thus, the validation set was only used for testing the equations. The criterion used for the selection of the validation set was samples with the highest number of neighbours and the most separation between them (H<0.6). Partial least squares regression and cross validation were used for multivariate calibration. The FT-midIR method does not require post-extraction manipulation and gives information about the fatty acid profile in two min. The 14:0, 16:0, 18:0, 18:1 and 18:2 fatty acids can be determined with excellent precision and other fatty acids with good precision according to the Shenk criteria, R 2≥0.90, SEP=1–1.5 SEL and R 2=0.70-0.89, SEP=2–3 SEL, respectively. The results obtained with the proposed method were compared with those provided by the conventional method based on GC-MS. At 95% significance level, the differences between the values obtained for the different fatty acids were within the experimental error. [ABSTRACT FROM AUTHOR]

A method for routine analysis of essential metal elements in animal feeds using a dynamic and automated ultrasound-assisted extractor is proposed here. Owing to the different concentration of the essential metal elements in the samples, two macronutrients—namely, Ca and Mg—and three micronutrients or trace elements—namely, Fe, Cu and Zn—were selected as models for the optimisation and characterisation of the proposed method by using experimental design methodology. Moreover, the extraction kinetics and influence of the particle size on the extraction efficiency were studied. The detection and quantification limits ranged between 2.9 and 40 μg kg-1 and between 7.9 and 95.5 μg kg-1, respectively. The precision, expressed as repeatability relative standard deviation (RSD) and as within-laboratory RSD, ranged between 1.86 and 5.66% and between 5.06 and 6.15%, respectively. The proposed approach allows the extraction of these metal elements from animal feeds with extraction efficiencies similar to those provided by the AOAC Official Method 968.08, but with a drastic reduction in both the extraction time (18 min versus 4.5 h) and sample handling, and using smaller volumes of extractant (an acid aqueous solution). [ABSTRACT FROM AUTHOR]