Authentication of fattening diet of Iberian pigs according to their volatile compounds profile from raw subcutaneous fat.

The composition of volatile components of subcutaneous fat from Iberian pig has been studied. Purge and trap gas chromatography-mass spectrometry has been used. The composition of the volatile fraction of subcutaneous fat has been used for authentication purposes of different types of Iberian pig fat. Three types of this product have been considered, montanera, extensive cebo and intensive cebo. With classification purposes, several pattern recognition techniques have been applied. In order to find out possible tendencies in the sample distribution as well as the discriminant power of the variables, principal component analysis was applied as visualisation technique. Linear discriminant analysis (LDA) and soft independent modelling by class analogy (SIMCA) were used to obtain suitable classification models. LDA and SIMCA allowed the differentiation of three fattening diets by using the contents in 2,2,4,6,6-pentamethyl-heptane, m-xylene, 2,4-dimethyl-heptane, 6-methyl-tridecane, 1-methoxy-2-propanol, isopropyl alcohol, o-xylene, 3-ethyl-2,2-dimethyl-oxirane, 2,6-dimethyl-undecane, 3-methyl-3-pentanol and limonene.

Differentiation of certified brands of origins of Spanish white wines by HS-SPME-GC and chemometrics.

A headspace solid-phase microextraction gas-chromatographic (HS-SPME-GC) procedure was used to determine the composition of the volatile fraction of white wine samples from several Spanish certified brands of origin (CBO). The compounds present were previously identified by gas chromatography-mass spectrometry (GC-MS) and quantitative determinations were carried out by GC-FID. Four CBO, Rueda, Ribeiro, Penedés, and Condado de Huelva, were studied. Rueda wines present the highest concentrations of ethyl acetate (55.86-125.27 microg mL(-1)), isoamyl acetate (0.91-6.72 microg mL(-1)), hexyl acetate (0.09-0.81 microg g mL(-1)), and 2-phenethyl acetate (0.14-0.66 microg mL(-1)). Compounds such as ethyl hexanoate (0.88-2.15 microg mL(-1)) and ethyl decanoate (0.29-0.96 microg mL(-1)) appeared in higher concentration in Ribeiro, Rueda, and Penedés samples. According to the results obtained and by applying pattern-recognition procedures differentiation of the considered CBO was attained. Principal-component analysis (PCA), linear discriminant analysis (LDA), and multilayer perceptrons neural networks (MLP-NN) were used as chemometric tools for pattern-recognition studies.

Differentiation of green, white, black, Oolong, and Pu-erh teas according to their free amino acids content.

In this paper, the differentiation of green, black, Oolong, white, and Pu-erh teas has been carried out according to their free amino acid contents. Alanine, arginine, asparagine, aspartic acid, glutamic acid, isoleucine, histidine, leucine, phenylalanine, serine, theanine, threonine, and tyrosine have been determined by liquid chromatography with derivatization with o-phthalaldehyde and fluorescence detection. The chromatographic separation was achieved with a Hypersil ODS column and gradient elution. The amino acid contents were used as chemometric descriptors for classification purposes of different tea varieties. Principal component analysis, k-nearest neighbors, linear discriminant analysis, and artificial neural networks were applied to differentiate tea varieties. Using back-propagation multilayer perceptron artificial neural networks, 100% success in the classification was obtained. The most differentiating amino acids were glutamic acid, asparagine, serine, alanine, leucine, and isoleucine.

Differentiation of tea (Camellia sinensis) varieties and their geographical origin according to their metal content.

The metal content of 46 tea samples, including green, black, and instant teas, was analyzed. Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Sr, Ti, and Zn were determined by ICP-AES. Potassium, with an average content of 15145.4 mg kg(-1) was the metal with major content. Calcium, magnesium, and aluminum had average contents of 4252.4, 1978.2, and 1074.0 mg kg(-1), respectively. The average amount of manganese was 824.8 mg kg(-1). There were no clear differences between the metal contents of green and black teas. Pattern recognition methods such as principal component analysis (PCA), linear discriminant analysis (LDA), and artificial neural networks (ANN), were applied to differentiate the tea types. LDA and ANN provided the best results in the classification of tea varieties. These chemometric procedures were also useful for distinguishing between Asian and African teas and between the geographical origin of different Asian teas.

Fluorimetric determination of gallium in a nickel alloy and aluminium with N-oxalylamine(salicylaldehyde hydrazone).

A fluorimetric determination of gallium, based on the formation of the fluorescent chelate with N-oxalylamine(salicylaldehyde hydrazone) (OSH)-Ga(III), is proposed. The complex has excitation and emission maxima at 395 and 475 nm, respectively. The detection limit is 3 ng/ml and Ga can be determined up to 277 ng/ml. The method has been applied to the determination of gallium in a nickel alloy and aluminium. Extraction with n-butyl acetate from 6M hydrochloric acid medium has been used to separate Ga from the interfering elements in the alloys.

Classification of tea samples by their chemical composition using discriminant analysis.

Multivariate analysis in combination with pattern recognition procedures has been applied to samples of green and black tea. Discriminant analysis has been used for classification purposes. Aqueous extract, polyphenols, amino acids, caffeine, theobromine and theophylline were used as chemical descriptors.

Discrimination between arabica and robusta green coffee varieties according to their chemical composition.

Arabica and robusta green coffee varieties have been differentiated by using pattern recognition procedures. Chlorogenic acid, caffeine, trigonelline, aqueous extract, amino acids and polyphenols have been analysed in 41 samples of green coffee and used as chemical descriptors. Principal component and cluster analysis in addition with the K-nearest neighbours method have been applied.

Simultaneous determination of caffeine and non-steroidal anti-inflammatory drugs in pharmaceutical formulations and blood plasma by reversed-phase HPLC from linear gradient elution.

A reversed-phase HPLC procedure based on methanol-water gradient elution for determining caffeine and non-steroidal anti-inflammatory drugs with UV absorbance detection is proposed. Chromatographic operational conditions were selected by considering the peak resolution and the retention times of the first and last eluted compounds. The method was suitably validated and successfully applied to the determination of: caffeine, indoprofen, ketoprofen, naproxen, fenbufen and ibuprofen in blood plasma samples and several analgesic/antiphlogistic pharmaceutical formulations.

Evaluation of two new asymmetric derivatives of thiocarbohydrazide as spectrophotometric analytical reagents.

The synthesis and analytical properties of 1-(2-pyridylmethylideneamino)-3-(4-hydroxybenzylideneamino)thiourea PHT and 1-(2-pyridylmethylideneamino)-3-(2,4-dihydroxybenzylideneamino)-thiourea PDT have been studied. A spectrophotometric method has been used to determine the protonation constants of the reagents and a spectrophotometric survey of the reactions of various cations with PHT and PDT has been made.

Determination of the optimum working range in spectrophotometric procedures.

A brief introduction to the topics of covariance and variance is given in this paper. An abstract vectorial space, the "precision pattern space" is introduced in order to find the general expression for the law of random error propagation. A new approach to the determination of the optimum working range in spectrophotometric procedures has been developed. The method involves the use of the calibration curve and the application of the Laplacian operator to concentration. The general expression reported for the relative error in concentration tends towards the classical photometric error expression in limiting cases.

[Lemiere's syndrome. Thrombophlebitis of the internal jugular vein induced by oropharyngeal lesion. A case report]. / Síndrome de Lemierre. Tromblofebitis de la vena yugular interna de causa orofaríngea. Revisión a propósito de un caso.

Nowadays due to the use of antibiotics the occurrence of a general complication of tonsillitis is extremely rare. Lemierre in 1936 throroughly described one of these events. We introduce a case of postanginal septicaemia detected in a previous healthy young woman. We also undertake a review of Lemierre's syndrome cases published within the last seven years in the English and Spanish literature, giving special attention to diagnostical methods and therapeutical strategies.

Characterization and quantification of 4-methylsterols and 4,4-dimethylsterols from Iberian pig subcutaneous fat by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector and their use to authenticate the fattening systems.

4-Methylsterols and 4,4-dimethylsterols of 47 samples of subcutaneous fat from Iberian pigs reared on two different fattening systems, "Extensive" and "Intensive", have been analyzed by GC-MS and GC-FID. The lipids were extracted by melting the subcutaneous fat in a microwave oven. The unsaponifiable matter was fractionated by thin layer chromatography. Then, the analysis was performed on a capillary SPB-5 column (30 m × 0.25 mm i.d., 0.15 µm film thickness), with hydrogen as a carrier gas and using a flame ionization detector. n-eicosanol was used as internal standard for quantification of individual methylsterols. These compounds have been analyzed by GC-MS for their identification. The full scan of free and trimethyl silyl ethers was used as acquisition mode. Six compounds have been identified for the first time in this type of samples: (3ß,4α,5α)-4-methyl-cholesta-7-en-3-ol, (3ß,4α,5α)-4-methyl-cholesta-8(14)-en-3-ol, (3ß,5α)-4,4-dimethyl-cholesta-8(14),24-dien-3-ol, (3ß)-lanosta-8,24-dien-3-ol, (3ß, 5α)-4,4-dimethyl-cholesta-8,14-dien-3-ol and (3ß)-lanost-9(11),24-dien-3-ol. The samples were derivatized as trimethyl silyl ethers before their analysis by GC-FID. By using these compounds as chemical descriptors, pattern recognition techniques were applied to differentiate between extensive and intensive fattening systems of Iberian pig. Several pattern recognition techniques, such as principal component analysis, linear discriminant analysis, support vector machines, artificial neural networks, soft independent modeling of class analogy and k nearest neighbors, have been used in order to find out a suitable classification model. A multilayer perceptron artificial neural network based on the contents of the above mentioned compounds allowed the differentiation of the two fattening systems with an overall classification performance of 91.7%.

Characterization of aniseed-flavoured spirit drinks by headspace solid-phase microextraction gas chromatography-mass spectrometry and chemometrics.

The volatile composition of aniseed-flavoured spirit drinks was studied by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The influence of the time, temperature, volume of sample and ionic strength on the extraction were considered. Several aniseed-flavoured spirit drinks, such as pastis, sambuca, anis and raki were analyzed. The major compounds found were trans-anethole (41.22-98%), cis-anethole (0.77-18.65%) and estragole (0.1-17.96%). gamma-Himachalene (0-28.07%) and alpha-himachalene (0-4.8%) were also present in anis and raki beverages. The compounds determined were used as chemical descriptors to differentiate the four types of beverages considered. Principal component analysis (PCA), linear discriminant analysis (LDA) and artificial neural networks (ANN) were used as chemometric tools for characterization purposes.

Classification of aniseed drinks by means of cluster, linear discriminant analysis and soft independent modelling of class analogy based on their Zn, B, Fe, Mg, Ca, Na and Si content.

Zinc, boron, iron, magnesium, calcium, sodium and silicon were determined in aniseed drinks by inductively coupled plasma-atomic emission spectrometry (ICP-AES). These elements were considered as chemical descriptors to characterise Spanish-certified aniseed drinks brands of origin. Different pattern recognition (PR) procedures were applied for these purposes. This chemometric study have included methods like principal component analysis (PCA), non-supervised PR techniques such as cluster analysis (CA), supervised PR methods of hard modelling like linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA).

HPLC determination of catechins and caffeine in tea. Differentiation of green, black and instant teas.

A simple and fast high performance liquid chromatographic method for five catechins and caffeine using an ODS column and a water-acetonitrile-formic acid mobile phase system was developed. The catechins (epicatechin, catechin, epigallocatechin, epigallocatechin gallate, epicatechin gallate) and caffeine were separated by an acetonitrile gradient within 20 min. The detection limit of the method was approximately 10 ng for all the compounds (by injecting 10 microL). Several green, black and instant teas were analysed using this method. By using the studied compounds as chemical descriptors, linear discriminant analysis was performed and complete differentiation of the green, black and instant teas was achieved.

Determination of Zn, B, Fe, Mg, Ca, Na and Si in anisette samples by inductively coupled plasma atomic emission spectrometry.

A comparative study of several digestion methods of anisette samples has been carried out. Two dry ashing (DA) treatments as well as four wet ashing (WA) procedures using different mixtures of acids were applied for the sample mineralisation before analysis. Once the anisette samples were mineralised, the contents of Zn, B, Fe, Mg, Ca, Na and Si were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each method has been studied statistically and also attending to their feasibility. After performing the optimisation of the different treatments tested, it was concluded that one wet ashing method employing a HNO(3):H(2)O(2) (10:1) mixture was the most suitable. This method was applied to the analysis of anisette samples. Na, Ca, Mg and Si were present in concentrations up to 215mgl(-1) for Na, 11.6 for Mg, 6.2 for Ca and 5.1 for Si. Fe and B concentrations were not higher than 0.12mgl(-1) and lower for Zn.

Fatty acid profiles as discriminant parameters for coffee varieties differentiation.

The fatty acid contents of coffee lipid extracts have been determined by capillary gas chromatography. Ten fatty acids were considered: myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), arachidic (C20:0), eicosenoic (C20:1) and behenic acid (C22:0). The analyzed coffee samples belonged to arabica and robusta varieties and were either green or roasted coffee beans. The lipids were Soxhlet extracted from ground coffee beans with hexane, and the fatty acids were determined as their corresponding methyl esters. Fatty acids contents were considered as chemical descriptors to differentiate coffee varieties. Several Pattern Recognition methods, Principal Component Analysis and Linear Discriminant Analysis allowed discrimination between green and roasted arabica and robusta coffees.

Ion chromatographic determination of some organic acids, chloride and phosphate in coffee and tea.

An ion chromatographic method for the simultaneous determination of organic acids and inorganic ions is described. Acetic, malic, ascorbic, citric, malic and succinic acids, chloride and phosphate were determined in coffee and tea samples. The separation is performed on an anion-exchange column operated at 40 degrees C within 25 min by an isocratic elution with 0.6 mM aqueous potassium hydrogenphthalate (pH 4.0) solution containing 4% (v/v) acetonitrile as eluent and determination by conductivity detection. The method does not need a special sample treatment and was successfully applied to the analysis of black, green and oolong tea samples. Also, green and roasted coffee samples from the varieties arabica and robusta were analyzed.