Ecotoxicity evaluation of tetramethrin and analysis in agrochemical formulations using chiral electrokinetic chromatography

The separation of the four isomers of tetramethrin was performed for the first time using a cyclodextrin-micellar electrokinetic chromatography methodology. Using sodium deoxycholate and 2-hydroxypropyl-β-CD as chiral selectors, tetramethrin isomers were separated with resolution values of 1.7 and 1.1 for trans- and cis-isomers, respectively, in analysis times lower than 12.5 min. Once developed and optimized, the analytical method was applied to the analysis of an antiparasitic commercial formulation and to the evaluation of the stability and ecotoxicity of tetramethrin. Using measured concentrations, the stability was assessed at enantiomeric level and the ecotoxicological parameters on Daphnia magna were determined. Tetramethrin presents toxicity on aquatic microinvertebrates, with EC₅₀ (t = 72 h) of 1.8 mg/L. The acute toxicity of tetrametrin was attributed to the trans-1 enantiomer. The first evidence of oxidative stress-mediated mode of action for tetramethrin on Daphnia magna is reported in the present work.

Impact of the use of pressurized liquids on the extraction and functionality of proteins and bioactives from brewer's spent grain

A green methodology based on pressurized liquids (PLE) to extract proteins and obtain highly active extracts from brewer's spent grain (BSG) is proposed. Box-Behnken experimental design was employed to study the effect of extraction parameters on the protein content (PC), the total phenolic content (TPC), and the antioxidant activity of extracts. Results were compared with those obtained by conventional alkaline extraction assisted with ultrasounds (UAE). The selection of PLE conditions enabled to tailor the PC and TPC of extracts. PLE extracted 36 % more proteins than UAE. PLE extracts showed higher antioxidant, cholesterol esterase inhibition, and ACE inhibitory activities than UAE extract. HPLC-MS/MS enabled to observe that the extraction technique and experimental conditions significantly affected to the kind and amount of extracted proteins, and released peptides, and phenolic compounds. A higher ratio of hydrophobic peptides was observed in PLE extracts, which justified their higher bioactivity.

Apricot and other seed stones: amygdalin content and the potential to obtain antioxidant, angiotensin I converting enzyme inhibitor and hypocholesterolemic peptides

Stones from olives and Prunus genus fruits are cheap and sustainable sources of proteins and could be potential sources of bioactive peptides. The main limitation to the use of these seeds is the presence of amygdalin. This work proposes to determine amygdalin in olive and Prunus seeds and in protein isolates obtained from them. Moreover, antioxidant, angiotensin I converting enzyme (ACE) inhibitor, and hypocholesterolemic properties will be evaluated in hydrolysates obtained from these seeds. Despite some seeds contained amygdalin, all protein isolates were free of this substance. Two different procedures to obtain bioactive peptides from protein isolates were examined: gastrointestinal digestion and processing with Alcalase, Flavourzyme or Thermolysin. Higher antioxidant, ACE inhibitor and hypocholesterolemic activities were observed when proteins were processed with Alcalase, Flavourzyme or Thermolysin. The highest antioxidant and ACE inhibitor capacities were observed for the Prunus genus seed hydrolysates while the highest capacity to reduce micellar cholesterol solubility was observed for the apricot and olive seed hydrolysates.

A cross-platform metabolomics workflow for volume-restricted tissue samples: application to an animal model for polycystic kidney disease

Metabolic profiling provides an unbiased view of the physiological status of an organism as a “function” of the metabolic composition of a measured sample.

Determination and characterization of glycerophospholipids in olive fruit and oil by nonaqueous capillary electrophoresis with electrospray-mass spectrometric detection

A nonaqueous capillary electrophoresis method with electrospray-mass spectrometric detection was developed to study the glycerophospholipid fraction in olive fruit and olive oil samples. In olive fruits, where the information available about the phospholipid fraction was very scarce, results obtained in this work allowed us to complete and improve this knowledge. The glycerophospholipid fraction of the olive fruit samples analyzed was composed of phosphatidylcholine (PC), phosphatidylethanolamine (PE), lysophosphatidylethanolamine (lyso-PE), phosphatidylinositol (PI), phosphatidic acid (PA), lysophosphatidic acid (lyso-PA), and phosphatidylglycerol (PG). Differences in the relative abundance of the glycerophospholipid classes determined were observed as a function of the botanical and geographical origin of the olive fruits analyzed. Interestingly, the olive stone and pulp analyzed also showed different glycerophospholipid compositions. For olive oil, five glycerophospholipids (lyso-PA, PC, PE, lyso-PE, and PG) were detected. Finally, identification of the main molecular species in the different glycerophospholipid classes for the olive fruit samples analyzed was accomplished by tandem mass spectrometric experiments and information from the literature.

Spectrophotometric determination of copper(II), nickel(II) and cobalt(II) as complexes with sodium diethyldithiocarbamate in cationic micellar medium of hexadecyltrimethylammonium salts

The determination of copper(II), nickel(II) and cobalt(II) was carried out as diethyldithiocarbamate (DDTC) complexes in presence of aqueous solutions of cationic surfactants of hexadecyltrimethylammonium bromide, chloride and hydroxide (CTAB, CTAC, CTAOH). The presence of micellar systems avoids the previous step of solvent extraction necessary to the formation of the DDTC complexes in absence of micelles. The influence of the different micellar counterions on the analytical characteristics (sensitivity and detection limits) of the proposed method for spectrophotometric determination of Cu(II), Ni(II) and Co(II) was studied.

Characterization of carboxylate-terminated carbosilane dendrimers and their evaluation as nanoadditives in capillary electrophoresis for vegetable protein profiling

Protein profiles are becoming an important tool to differentiate and classify varieties of several cultivars and to obtain a specific fingerprint for them. The use of protein profiles for these purposes needs to achieve high separation efficiencies to obtain a high number of well resolved peaks. In this work, carbosilane dendrimers with interior carbon-silicon bonds and negatively charged in the dendrimer surface with carboxylic acid as functional groups were employed as nanoadditives to separate soybean and olive seeds proteins. First, these dendrimers were characterized using CE to evaluate their possible impurities. A potentiometric titration was later carried out to determine their pK(a) values. Afterwards, the characterized dendrimers were used to improve the protein profiles obtained by EKC for vegetable proteins. Different dendrimer generations (G1, G2, and G3) and concentrations (0.01-1% m/v) were tested. The highest dendrimer generation G3 at 0.1% (m/v) allowed observing the best protein profiles for soybean and olive seeds. These results demonstrate that carboxylate-terminated carbosilane dendrimers are attractive nanoadditives in EKC for the effective separation of vegetable proteins.

Analysis of olive allergens

Olive pollen is one of the most important causes of seasonal respiratory allergy in Mediterranean countries, where this tree is intensely cultivated. Besides this, some cases of contact dermatitis and food allergy to the olive fruit and olive oil have been also described. Several scientific studies dealing with olive allergens has been reported, being the information available about them constantly increasing. Up to date, twelve allergens have been identified in olive pollen while just one allergen has been identified in olive fruit. This review article describes considerations about allergen extraction and production, also describing the different methodologies employed in the physicochemical and immunological characterization of olive allergens. Finally, a revision of the most relevant studies in the analysis of both olive pollen and olive fruit allergens is carried out.

Ultrarapid quantitation of maize proteins by perfusion and monolithic reversed-phase high-performance liquid chromatography

The main objective of this study was to develop a new methodology alternative to the classical Kjeldahl analysis for determining maize proteins in maize products and seeds. For that purpose, two different chromatographic methodologies using perfusion and monolithic stationary phases, both enabling rapid separations of maize proteins, were investigated. Due to the difficulty to find suitable standards for this type of analysis, three different maize products were initially tested as proteins standards: zein F4000, corn gluten meal, and maize flour. Different figures of merit (i.e., linearity, correlation coefficient, precision, limits of detection and quantitation), as well as the presence of matrix inferences, were investigated. The results obtained for the different chromatographic stationary phases and protein standards were compared in order to select the most suitable analytical conditions. Despite both perfusion and monolithic methodologies resulting, in general, as appropriate for the quantitation of maize proteins, the highest reduction of analysis time and lowest detection and determination limits provided by perfusion methodology enabled to select this one as the method of choice for the quantitation of maize proteins. Regarding the different protein standards studied in this work, in general the best results were obtained using the zein standard. Compared to Kjeldahl methodology, perfusion chromatography yields total protein contents in shorter analysis time while enabling the separation of the different kinds of proteins. Due to the high diversity and complexity of industrial maize products, the proposed chromatographic method could be a very useful tool for their routine analysis.

Development of a perfusion ion-exchange chromatography method for the separation of soybean proteins and its application to cultivar characterization

A perfusion ion-exchange chromatography method has been designed, for the first time, for the separation of soybean proteins and its application to the characterization of soybean cultivars. For that purpose, the gradient, the mobile phase composition (buffer concentration, buffer pH, and elution salt), and the temperature were optimized. The method consisted of a two-step gradient (0% B for 2 min and from 0 to 50% B in 10 min) being mobile phase A a 2 0mM borate buffer (pH 9) and mobile phase B a 20 mM borate buffer (pH 9) containing 1M sodium chloride. The procedure used for the preparation of sample solutions was significantly simpler than that proposed by other authors and basically consisted of dissolving in water. This method enabled the separation of soybean proteins from a soybean protein isolate in 11 peaks in about 9 min. The method was used to separate soybean proteins in different commercial soybeans. In general, the 11 peaks yielded by the soybean protein isolate were also observed in the chromatograms of all soybeans. However, the area percentages of every peak in every soybean enabled the differentiation between soybeans. Moreover, the method was also used to separate soybean proteins in the proteic fractions obtained from every soybean. Multivariate methods were used for patterns recognition and the classification of samples.

Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography

The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60 degrees C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH=11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.

Monolithic supports for the characterization of commercial maize products based on their chromatographic profile. Application of experimental design and classification techniques

Modern analytical techniques based on the use of RP-HPLC with monolithic stationary phases and the application of experimental design and classification tools have been applied to the analysis of maize proteins. Solubilization conditions of maize proteins and separation conditions (temperature, detection wavelength, type and concentration of ion-pairing agent, and gradient) were optimized. The elution gradient was optimized by the application of experimental design techniques. The optimized method consisted of a linear binary gradient of water/acetonitrile/0.1% trifluoroacetic acid in three steps at a flow rate of 3 mL/min with a column temperature of 35 degrees C and UV detection at 280 nm. The developed method enabled the separation of maize proteins in an analysis time close to 8 min. Moreover, this is the first time that commercial maize products have been characterized by the use of multivariate classification techniques.

Development of a perfusion reversed-phase high performance liquid chromatography method for the characterisation of maize products using multivariate analysis

A perfusion reversed-phase high performance liquid chromatography (RP-HPLC) method has been designed to allow rapid (3.4 min) separations of maize proteins with high resolution. Several factors, such as extraction conditions, temperature, detection wavelength and type and concentration of ion-pairing agent were optimised. A fine optimisation of the gradient elution was also performed by applying experimental design. Commercial maize products for human consumption (flours, precocked flours, fried snacks and extruded snacks) were characterised for the first time by perfusion RP-HPLC and their chromatographic profiles allowed a differentiation among products relating the different technological process used for their preparation. Furthermore, applying discriminant analysis makes it possible to group the samples according with the technological process suffered by maize products, obtaining a good prediction in 92% of the samples.

Easy determination of the addition of soybean proteins to heat-processed meat products prepared with turkey meat or pork−turkey meat blends that could also contain milk proteins

The addition of non-meat proteins to processed meat products is limited by regulations. Therefore, this work has investigated the determination of added soybean proteins in commercial heat-processed meat products prepared with turkey meat or pork-turkey meat blends that could also contain milk proteins. The method consisted of extracting proteins from the meat products in a Tris-HCl buffer (pH 8) and analysing the extract by high-performance liquid chromatography with a linear gradient water-acetonitrile containing 0.05% (v/v) TFA. This method enabled the detection and quantitation of up to 0.08 and 0.28% (w/w), respectively, of soybean proteins (related to 6 g initial product) in these products. Satisfactory precision and recovery data were established. Accuracy was evaluated by a comparison of soybean protein contents determined by the proposed method and the existing AOAC official method based on an enzyme-linked immunosorbent assay (ELISA) from which no statistically significant differences were observed.

Development of a perfusion reversed-phase HPLC method for the separation of soybean and cereal (wheat, corn, and rice) proteins in binary mixtures. Application to the detection of soybean proteins in commercial bakery products

A perfusion reversed-phase HPLC method enabling the simultaneous separation of soybean and cereal (wheat, corn, and rice) proteins in commercial bakery products has been proposed for the first time. The method utilises an acetonitrile-water gradient containing an ion-pairing agent. Different ion-pairing agents were tried, 0.3% (v/v) acetic acid being observed to enable the separation of soybean from wheat, rice, and corn proteins while with 0.1% (v/v) trifluoroacetic acid only the separation of soybean and corn proteins was possible. Optimisation of the solubilisation conditions for proteins was achieved by testing different acetonitrile concentrations for the simultaneous extraction of soybean and cereal proteins: best recoveries were found with 25% (v/v) acetonitrile + 0.3% (v/v) acetic acid and with 40% (v/v) acetonitrile + 0.1% (v/v) trifluoroacetic acid. Chromatographic conditions such as gradient, temperature, and wavelength detection were also optimised. The method enabled the separation of soybean and cereal proteins in binary mixtures (soybean and wheat, soybean and corn, or soybean and rice proteins) in less than 5 minutes in a total analysis time of 20 min.

Micellar electrokinetic chromatography with bile salts for predicting ecotoxicity of aromatic compounds

The retention factors of several aromatic compounds were obtained by micellar electrokinetic chromatography (MEKC) using cholate, taurocholate, deoxycholate and deoxytaurocholate as micellar systems. The possibility of using these retention factors to describe and predict several ecotoxicological activities of different aromatic compounds was evaluated. Adequate correlations retention-ecotoxicity (log LC50 in fish and daphnia, log EC50 in green algae and daphnia, chronic values in fish and green algae, bioconcentration factor, and soil sorption coefficient) were obtained for the micellar systems studied. The predictive ability of the models obtained for these micellar systems was compared. Predicted values concur with the experimental log LC50 in Bluegill, Rainbow trout, Fathead minnows and Daphnia Magna values for the compounds studied. The results obtained indicated the usefulness of the MEKC systems investigated for the rapid ecotoxicity assessment of aromatic compounds.

Analysis of soyabean proteins in meat products: a review

The use of soyabean proteins as meat extenders has spread significantly due to the interesting nutritional and functional properties that are present in soyabean proteins. Together with these, health and economical reasons are the major causes for the addition of soyabean proteins to meat products. Nevertheless, despite the good properties associated to soyabean proteins, there are many countries in which the addition of these proteins is forbidden or in which the addition of soyabean proteins is allowed up to a certain extent. Thus, the need of analytical methods enabling the detection of added soyabean proteins in meat products is obvious. Microscopic, electrophoretic, immunologic, and chromatographic methods are the most widely used for this purpose. However, the detection of soyabean proteins in meat products presents difficulties related to the composition (meat species, meat quality, soyabean protein source, presence of other non-meat proteins, etc.) and the processing of the meat products, and, although these analytical methods have tried to overcome all these difficulties, there is still not a method enabling quantitative assessment of soyabean proteins in all kinds of meat products.

Fast enantiomeric separation of basis drugs by electrokinetic chromatography. Application to the quantitation of terbutaline in a pharmaceutical preparation

Electrokinetic chromatography (EKC) using micelles of bile salts alone or mixed with sodium dodecyl sulfate (SDS) and neutral, anionic, or cationic cyclodextrins (CDs) in the separation buffer has been employed in order to achieve fast enantiomeric separation of basic drugs. A study of the enantiomeric separation ability of these chiral selectors concerning four basic drugs (epinephrine, terbutaline, clenbuterol, and salbutamol) has been carried out under different experimental conditions. The best chiral selectors to perform the enantiomeric separation of these drugs were neutral beta-CD derivatives, specifically permethylated beta-CD PM-beta-CD. The effect of the PM-beta-CD concentration, temperature, and applied voltage on the enantiomeric resolution of the basic drugs was investigated. The use of a 25 mM ammonium acetate buffer (pH 5.0), 30 mM in PM-beta-CD together with an applied voltage of 20 kV and a temperature of 15 degrees C enabled the individual and fast enantiomeric separation of epinephrine, norepinephrine, terbutaline, clenbuterol, and salbutamol each one into its two enantiomers in less than 3 min. The EKC method was validated (precision and accuracy) to quantitate terbutaline in a pharmaceutical preparation, obtaining a limit of detection of 4 microg/mL.

Enantiomeric separation of chiral phenoxy acid herbicides by electrokinetic chromatography. Application to the determination of analyte-selector apparent binding constants for enantiomers

The enantiomeric resolution of chiral phenoxy acid herbicides was performed by electrokinetic chromatography using a cyclodextrin as chiral pseudophase (CD-EKC). A systematic evaluation of several neutral and charged cyclodextrins was made. Among the cyclodextrins tested, (2-hydroxy)propyl beta-cyclodextrin (HP-beta-CD) was found to be the most appropriate for the enantioseparation of phenoxy acids. The influence of some experimental conditions, such as nature and pH of the background electrolyte, chiral selector concentration, and temperature, on the enantiomeric separation of phenoxy acids was also studied. The use of a 50 mM electrolyte solution in ammonium formate at pH 5 and a temperature of 40 degrees C enabled the enantiomeric resolution of four of the six phenoxy acids investigated (2-phenoxypropionic acid, 2(3-chlorophenoxy)propionic acid, 2-(4-chlorophenoxy)propionic acid, and 2-(2,4-dichlorophenoxy)propionic acid) obtaining migration times ranging from 9 to 15 min. Mixtures of the two phenoxy acids not enantiomerically resolved (2-(4-chlorophenoxy)-2-methylpropionic acid and 2-(2,4,5-trichlorophenoxy)propionic acid) and up to three of the phenoxy acids enantiomerically resolved were separated in about 15 min. Finally, the apparent binding constants for each enantiomer-HP-beta-CD pair were calculated at two temperature values (20 and 40 degrees C).

Application of capillary zone electrophoresis with off-line solid-phase extraction to in vitro metabolism studies of antifungals

A simple and robust solid-phase extraction (SPE) procedure for the cleanup and sample preconcentration of antifungals (ketoconazole, clotrimazole, itraconazole, fluconazole, and voriconazole) and their metabolites after incubation with human liver microsomes, as well as a simplified capillary zone electrophoresis (CZE) method for their rapid analysis, have been developed to determine the stability of these compounds in in vitro samples. Three different sample pretreatment procedures using SPE with reversed-phase sorbents (100 mg C8, 100 mg C18, and 30 mg Oasis-HLB) were studied. The highest and most reproducible recoveries were obtained using a 30 mg Oasis-HLB sorbent and methanol containing 2% acetic acid as eluent. Enrichment by a factor of about four times was achieved by reconstituting the final SPE eluates to a small volume. For the CZE separation, good separations without interfering peaks due to the in vitro matrix were obtained with a simple running electrolyte using a fused-silica capillary. The best separation for all components originated by each tested drug after incubation with human liver microsomes (unmetabolized parent drug and its metabolites) was obtained using a 0.05 M phosphate running buffer (pH 2.2) without additives. The effect of the injection volume was also investigated in order to obtain the best sensitivity. Performance levels in terms of precision, linearity, limits of detection, and robustness were determined.

Rapid separation of tetracycline derivatives and their main degradation products by capillary zone electrophoresis

A mixture of five tetracycline (TC) derivatives: minocycline (MC), demeclocycline (DMCTC), doxycycline (DC), and sancycline (SC), as well as each TC derivative from its main degradation product were separated by capillary zone electrophoresis (CZE). The influence of the pH and the concentration and nature of the background electrolyte (BGE) on the separations was investigated. Ethylenediaminetetraacetic acid (EDTA; 1 mM) was used as additive in a 25 mM phosphate buffer (pH 2.3) because this BGE enabled the rapid separation of the TC derivatives and of each TC derivative from its respective degradation product in less than 6 min. After optimization of the separation conditions, the analytical characteristics of the method were investigated. The parameters involved were linearity, precision (repeatability and reproducibility), and limits of detection (LODs). LODs obtained for the five TC derivatives studied were about 3 microg/mL. Finally, the CZE method developed was applied to study the stability of TC derivatives and to analyze the TC derivative content in three different pharmaceutical preparations.

A validated flame AAS method for determining magnesium in a multivitamin pharmaceutical preparation

A rapid method for determining magnesium in a multivitamin pharmaceutical preparation has been validated. This element is analysed by flame atomic absorption spectrometry after dissolution of the sample in acid medium. Linearity, precision, accuracy and robustness of the method have been determined, and detection and quantification limits have been calculated. Linearity of response was verified for concentrations ranging from 0.05 to 0.40 mg x l(-1) of magnesium. Correlation coefficient of the calibration straight lines was always > or =0.9999. Repeatability of the method gave relative standard deviation (R.S.D.) of 0.6%. Reproducibility of the method calculated after analysis of samples by the same analyst in different days (day-to-day fluctuation) and by two different analysts in different days (analyst-to-analyst fluctuation) gave relative standard deviation of 1.1 and 1.6%, respectively. Mean recoveries of magnesium obtained after spiking sample placebos with increasing amounts of magnesium chloride ranged from 98.9 to 100.8%. Robustness of the method evaluated by changing different experimental conditions under which analyses were performed, gave relative standard deviation from 0.2 to 0.5%. Limits of detection and quantification were 3.8 and 7.0 microg of Mg per gram of sample, respectively. Results show the suitability of the method for direct measurement of magnesium in a water-soluble multivitamin pharmaceutical preparation.

Study of retention in micellar liquid chromatography on a C8 column by the use of linear solvation energy relationships

Linear solvation energy relationships (LSERs) are used to investigate the fundamental chemical interactions governing the micellar liquid chromatographic retention of 22 aromatic compounds (11 benzene derivatives and 11 aromatic polycyclic hydrocarbons) in 80 mobile phases on a C8 column. The systems studied involve combinations of 0.050 to 0.140 M sodium dodecyl sulfate or cetyltrimethylammonium bromide, with 0 to 10% methanol, n-propanol, and n-butanol as mobile phase modifiers. The ability of the LSERs to account for the chemical interactions underlying solute retention is shown. A comparison of predicted and experimental retention factors suggests that LSER formalism is able to reproduce adequately the experimental retention factors of the solutes studied in the different experimental conditions investigated.

Optimization of the separation of a group of antifungals by capillary zone electrophoresis

Two simple, rapid, and efficient methods for the analysis of seven antifungal compounds have been developed by capillary zone electrophoresis. Resolutions higher than 1.5 were obtained using 0.025 M phosphate buffer (pH 2.30) (analysis time close to 9 min) or 0.2 M formic acid (pH 2.15) (analysis time close to 6 min), with an applied voltage of 20 kV and a temperature of 30 degrees C. The highest sensitivity and selectivity can be obtained using phosphate buffer but the shortest analysis times are achieved in the formic system. The analytical characteristics of the optimized methods were investigated. The reproducibility obtained for migration times (RSD(n = 10) < or = 1.0%) and peak areas (RSD(n = 10) < or = 4.3%) was acceptable, but better reproducibilities were obtained when verapamil was used as internal standard (RSD(n = 10) < 0.4% for relative migration times and RSD(n = 10) < or = 2.2% for peak area ratios). The lowest limit of detection was obtained for clotrimazole (0.12 microg/ml) and the highest for fluconazole and voriconazole (0.90 microg/ml). The lowest and the highest limits of quantitation were, respectively, 0.40 microg/ml for clotrimazole and 3.00 microg/ml for fluconazole and voriconazole.

Determination of iron and molybdenum in a dietetic preparation by flame AAS after dry ashing

Methods for the determination of iron and molybdenum in a dietetic pharmaceutical preparation by flame atomic absorption spectrometry (FAAS) after dry ashing at 600 degrees C have been validated. Linearity, precision, accuracy, detection and quantification limits, specificity and robustness have been determined. Linearity of response was verified for concentrations ranging from 0.50 to 4.00 mg l(-1) of iron and 1.00 to 6.00 mg l(-1) of molybdenum. Precision of the methods, performed under conditions of repeatability and reproducibility, gave relative standard deviations of 0.4 and 1.1%, respectively, for the iron determination and of 1.0 and 6.5%, respectively, for the molybdenum determination. Mean recoveries determined after spiking dietetic preparation placebos ranged from 97.1 to 102.6% for iron and 95.2 to 102.9% for molybdenum. The limit of detection for iron was 126 microg g(-1) and for molybdenum 129 microg l(-1). Quantification limits were 420 and 433microg l(-1) for iron and molybdenum, respectively. No interference in the iron and molybdenum determination due to other components present in the dietetic capsules was found. Day-to-day and analyst-to-analyst variability was less than 1.1% for iron and 4.5% for molybdenum. Results show the suitability of the method for measurement of iron and molybdenum in a complex matrix sample such as a dietetic pharmaceutical preparation.

Rapid enantiomeric separation of polychlorinated biphenyls by electrokinetic chromatography using mixtures of neutral and charged cyclodextrin derivatives

Electrokinetic chromatography with cyclodextrin derivatives (CD-EKC) was used to achieve the rapid enantiomeric separation of chiral polychlorinated biphenyls (PCBs). Thirteen of the 19 chiral PCBs stable at room temperature were individually separated into their two enantiomers by using 2-morpholinoethanesulfonic acid (MES) buffer (pH 6.5) containing carboxymethylated gamma-cyclodextrin (CM-gamma-CD) as pseudostationary phase mixed with beta-cyclodextrin (beta-CD) or permethylated beta-cyclodextrin (PM-beta-CD). Urea was also added to increase the solubility of PCBs and cyclodextrins in the aqueous separation buffer. Several experimental parameters such as the nature, concentration, and pH of the buffer, nature and concentration of the cyclodextrin derivatives used, and the addition of different additives were studied in order to improve the enantiomeric separation. In addition, the effect of some instrumental parameters such as separation temperature and applied voltage was also investigated. PCBs were enantiomerically separated in less than 12 min by using a 50 mM MES buffer (pH 6.5) containing 20 mM CM-gamma-CD, 10 mM beta-CD or 20 mM PM-beta-CD, and 2 M urea at a temperature of 45 degrees C and an applied voltage of 20 kV.

Laser-induced fluorescence detection at 266 nm in capillary electrophoresis. Polycyclic aromatic hydrocarbon metabolites in biota

The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of gamma-cyclodextrin (gamma-CD). A concentration of 12.5 mM gamma-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd-YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.

Fast enantiomeric separation of uniconazole and diniconazole by electrokinetic chromatography using an anionic cyclodextrin: application to the determination of analyte-selector apparent binding constants for enantiomers

The enantiomeric resolution of the fungicides uniconazole and diniconazole was performed using electrokinetic chromatography with cyclodextrins as pseudostationary phase (CD-EKC). A systematic evaluation of several chiral selectors was made. The anionic derivative carboxymethylated-gamma-cyclodextrin (CM-gamma-CD) was found to be the most appropriate for the enantioseparation of fungicides among all cyclodextrins tested. The influence of some experimental conditions such as nature and buffer pH, chiral selector concentration, and temperature on the enantiomeric separation of the compounds studied was also investigated. The use of a 50 mM phosphate buffer (pH 6.5) containing 5 mM CM-gamma-CD and a temperature of 50 degrees C enabled the baseline enantioresolution of mixtures of uniconazole and diniconazole in less than 5 min. In addition, apparent binding constants for each enantiomer-CM-gamma-CD pair at several temperatures, as well as thermodynamic parameters for binding were calculated.

Organochlorine and heavy metal residues in the water/sediment system of the Southeast Regional Park in Madrid, Spain

A study into levels of contamination by organochlorine compounds (insecticides and PCBs) and heavy metals (Cd and Pb) in the water/sediment system of the Southeast Regional Park (SERP) in Madrid, Spain, has been carried out. Residue levels of xenobiotics were determined in surface and underground waters and sediments from selected sites throughout the protected area. The results showed these contaminants to be widespread throughout the studied area. p,p'-DDT concentration levels were consistently higher than its metabolite p,p'-DDE, indicating a recent use of this organochlorine insecticide in the area. PCB levels exceeded, in the majority of the cases, the levels taken as the maximum (100 ng/microl) for highly polluted waters. Cd and Pb levels found in water samples were under the detection limits of the methodology used. Pb levels found in sediment samples were higher than Cd.

Separation of a group of N-phenylpyrazole derivatives by micellar electrokinetic chromatography: application to the determination of solute-micelle association constants and estimation of the hydrophobicity

Micellar electrokinetic chromatography (MEKC) was applied to the separation of a group of N-phenylpyrazole derivatives. Sodium dodecyl sulfate (SDS) as micellar system and 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) as separation buffer (pH 10) were employed in the absence and presence of different percentages of medium chain alcohols (n-propanol or n-butanol). The separation of multicomponent mixtures of the solutes studied enabled the rapid determination of their retention factors which, in turn, allowed the study of the separation selectivity of compounds and the determination of their solute-micelle association constants (from the linear variation of the retention factors as a function of the total surfactant concentration in the separation buffer). Separation selectivity was studied according to the elution range and number of solutes separated in all the electrolyte solutions employed (45 micellar phases). The effect of the buffer concentration (0.05, 0.08 and 0.10 M), the alcohol nature (n-propanol or n-butanol) and the alcohol percentage (1, 3 or 5%) of the values obtained for the solute-micelle association constants was also studied. The best separation (12 solutes) was performed when a 0.08 M CHES buffer, pH 10, 0.02 M SDS modified by 5% n-butanol was used. The possibilities of using MEKC for evaluating the hydrophobicity of compounds was investigated through the study of the correlation between the logarithm of the retention factors of N-phenylpyrazole derivatives and their logarithm of the octanol-water distribution coefficients estimated by high performance liquid chromatography (HPLC).

Determination by perfusion reversed-phase high-performance liquid chromatography of the soybean protein content of commercial soybean products prepared directly from whole soybeans

The use of soybean flour as external standard for the determination of soybean proteins in soybean products directly prepared from whole soybeans is investigated. For that purpose a perfusion reversed-phase high-performance liquid chromatography method consisting of a linear binary gradient acetonitrile-water (both with 0.1% trifluoroacetic acid) in 3 min at a flow-rate of 3 ml/min, and a temperature of 60 degrees C is used. Samples dissolved in water are directly injected in the chromatographic system. The method is validated by evaluating detection limits, precision, and accuracy and applied to the quantitation of soybean proteins in soybean products directly prepared from whole soybeans.

Characterization of commercial soybean products by conventional and perfusion reversed-phase high-performance liquid chromatography and multivariate analysis

Conventional and perfusion reversed-phase high-performance liquid chromatography are used to characterize commercial soybean products for human consumption. For this purpose, previously optimized methods of conventional and perfusion chromatography applied to the separation of soybean proteins are employed. Sixty different samples corresponding to 26 different trademarks of soybean products [soybean protein isolate, soybean flour, textured soybean, soybean milks (liquid and powdered), and soybean infant formulas] are analyzed. Characterization of soybean products is carried out on the basis of their protein profiles obtained by both chromatographic methods. Data obtained are processed using multivariate methods such as principal components and discriminant analysis. Perfusion chromatography enables a further and faster characterization of commercial soybean products than conventional chromatography, of great value in the quality control of this kind of product.

Perfusion chromatography: an emergent technique for the analysis of food proteins

Perfusion chromatography is a technique arised to overcome the problem associated with mass transfer in the separation of large molecules such as proteins by high-performance liquid chromatography (HPLC). Perfusion media are constituted by two set of pores: throughpores (6000-8000 A) and diffusive pores (800-1500 A) which enable better access of macromolecules to the inner of the particle by the combination of convective and diffusive flow. As a consequence, times required for a chromatographic separation are reduced. Perfusion media are available in different chromatographic modes: reversed-phase, ion-exchange, hydrophobic interaction, and affinity. From the theoretical models developed to explain the dynamic of retention of solutes in perfusive supports, it was derived that efficiency of a separation was independent of the flow-rate and only depended slightly on the particle diameter. Furthermore, loading capacity was also independent of the superficial velocity. All these advantages have promoted the use of this chromatographic technique for the separation of biomolecules both in analytical and preparative chromatography. Characteristics of perfusion chromatography make this technique very interesting for the analysis of food proteins. Perfusion chromatography enables the assessment of protein composition of a foodstuff at sufficient speed and low cost to be suitable in routine analysis.

Enantiomeric separation of a group of chiral dihydropyridines by electrokinetic chromatography

Electrokinetic chromatography (EKC) was employed to achieve the enantiomeric separation of a group of chiral 1,4-dihydropyridines (DHPs) with pharmacological activity. Micelles of bile salts alone or mixed with neutral cyclodextrins, micelles of sodium dodecyl sulfate (SDS) mixed with neutral cyclodextrins, and anionic cyclodextrin derivatives, i.e., carboxymethyl-gamma-cyclodextrin (CM-gamma-CD), carboxymethyl-beta-cyclodextrin (CM-beta-CD), and succinylated beta-cyclodextrin (Succ-beta-CD), were employed as pseudostationary phases. The enantiomeric separation ability of these chiral selectors with respect to DHPs was studied in different experimental conditions. CM-beta-CD was shown to be the best chiral selector to perform the enantiomeric separation of DHPs by EKC. Next, the influence of the CM-beta-CD concentration, the pH and nature of the buffer, the temperature, and the applied voltage on the enantiomeric resolution of DHPs was studied. The use of a 50 mM ammonium acetate buffer, pH 6.7, 25 mM in CM-beta-CD together with an applied voltage of 15 or 20 kV, and a temperature of 15 degrees C enabled the individual enantiomeric separation of twelve DHPs, each one into its two enantiomers, and their separation in multicomponent mixtures of up to six DHPs into all their enantiomers.

A reversed-phase high-performance liquid chromatographic method for the determination of soya bean proteins in bovine milks

A reversed-phase high-performance liquid chromatographic method was designed for the quantitation of soya bean proteins in bovine milks. The method consisted of a linear binary gradient, acetonitrile-water-0.1% trifluoroacetic acid, at a flow rate of 1 mL/min and a temperature of 50 degrees C which resulted in a separation time for soya bean proteins of 11 min. Calibration by the external standard method using a soya bean protein isolate as standard was employed, and the method was validated by evaluating precision, accuracy, and robustness. This method was shown to be useful for the analysis of soya bean proteins in bovine milks spiked with soya bean protein isolate; soya bean protein concentrations of approximately 13 microg/g of bovine milk could be detected by using the optimized method. The results obtained for some of the bovine milks were compared with those obtained by the method of standard additions.

Influence of mobile phase composition on electroosmotic flow velocity, solute retention and column efficiency in open-tubular reversed-phase capillary electrochromatography

The effects of some experimental parameters, such as the volume fraction and type of organic modifier in the mobile phase, and the concentration, type and pH of the buffer on the electroosmotic flow velocity, the retention behavior of test solutes, and the column efficiency have been investigated in capillary electrochromatography (CEC) using an open-tubular column of 9.60 microm I.D. with a porous silica layer chemically modified with C18 as stationary phase. The retention of a group of polycyclic aromatic hydrocarbons (PAHs) used as a test mixture varied significantly by changing the organic modifier content in the hydroorganic mobile phase according to the reversed-phase-like selectivity of the stationary phase. In addition, an increase in the percentage of organic modifier resulted in a slight increase in the linear velocity of the EOF. On the other hand, when the phosphate buffer concentration was increased over the range 1-50 mM, the electroosmotic mobility fell dramatically, the retention of the solutes decreased steadily, and the plate height showed a significant increase. The results obtained with phosphate, trishydroxymethylaminomethane or 2-morpholinoethanesulfonic acid as buffers were similar when pH remained constant. Optimization in CEC was essential to achieve further enhancement of separation performance, because the analysis time and separation resolution are essentially affected when varying operating parameters. Separations of seven PAHs with more than 100000 plates are presented within 4 min analysis time.

Analysis of bovine whey proteins in soybean dairy-like products by capillary electrophoresis

The simultaneous separation of bovine whey proteins [alpha-lactalbumin and beta-lactoglobulin (A+B)] and soybean proteins was performed, for the first time, by capillary electrophoresis. Different experimental conditions were tested. The most suitable consisted of 0.050 M phosphate buffer (pH 8) with 1 M urea and 1.2 mg/ml methylhydroxyethylcellulose, UV detection at 280 nm, 15 kV applied voltage, and 30 degrees C temperature. Quantitation of bovine whey proteins in a commercial powdered soybean milk manufactured by adding bovine whey to its formulation was performed using the calibration method of the external standard. Direct injection of a solution of the powdered soybean milk only enabled quantitation of alpha-lactalbumin in the commercial sample. Detection of beta-lactoglobulin (A+B) required acid precipitation of the solution of the sample in order to concentrate bovine whey proteins in the supernatant prior to the analysis of this protein in the whey obtained. Since alpha-lactalbumin could also be quantitated from the injection of the whey, the simultaneous determination of alpha-lactalbumin and beta-lactoglobulin (A+B) was possible upon acid precipitation of the powdered soybean milk solution. Detection limits obtained were 14 microg/g sol. for alpha-lactalbumin and 52 microg/g sol. for beta-lactoglobulin (A+B) which represent protein concentrations about 60 microg/100 g sample for alpha-lactalbumin and 100 microg/100 g sample for beta-lactoglobulin (A+B).

Characterization and quantitation of soybean proteins in commercial soybean products by capillary electrophoresis

Capillary electrophoresis was applied for the first time to determine soybean proteins in commercial soybean products. The most suitable conditions for the analysis of these products in less than 7 min were 0.05 M phosphate buffer (pH 8) with 1 M urea; detection wavelength, 254 nm; applied voltage, 20 kV; and temperature, 30 degrees C. Quantitation of soybean proteins was achieved using referenced conditions by means of the method of standard additions, using as standard a soybean protein isolate. This method was validated and applied to the quantitation of soybean proteins in commercial products derived from soybean protein isolate and soybean seeds.

Detection of bovine whey proteins by on-column derivatization capillary electrophoresis with laser-induced fluorescence monitoring

1-Anilinonaphthalene-8-sulfonic acid (1,8-ANS), 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) and 2-(p-toluidino)naphthalene-6-sulfonic acid (2,6-TNS) were evaluated as additives in different buffers for the detection of bovine whey proteins using laser-induced fluorescence (LIF) monitoring in capillary electrophoresis (CE). These N-arylaminonaphthalene sulfonates furnish a large fluorescence emission when associated to some proteins whereas their emission in aqueous buffers, such as those used in CE separations, is very small. To select the best detection conditions, the fluorescence of these probes was first compared using experiments carried out in a fluorescence spectrophotometer. Using bovine serum albumin (BSA) as a model protein, it was demonstrated that 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 8 and pH 10.2) and the fluorescent probe 2,6-TNS gave rise to the highest increase in fluorescence for BSA. When the composition of these separation buffers was optimized for the electrophoretic separations, CHES buffer, pH 10.2 was chosen as the most suitable buffer to detect bovine whey proteins. The limit of detection obtained for some whey proteins in CE separations was about 6.10(-8) M for BSA, 3.10(-7) M for beta-lactoglobulin A (beta-LGA), 3.10(-7) M for beta-lactoglobulin B (beta-LGB), and 3.10(-6) M for alpha-lactalbumin (alpha-LA). These detection limits were compared to those achieved using UV detection under the same separation conditions. The results showed that the detection limits of BSA, beta-LGA and beta-LGB were twice as good using LIF than with UV detection. However, the limit of detection for alpha-LA was better when UV was used. The applicability of LIF detection to CE separation of whey proteins in bovine milk samples was also demonstrated.

A perfusion reversed-phase chromatographic method for ultrarapid determination of soybean proteins in soybean infant formulas and soybean milks: method development and validation

Perfusion reversed-phase high-performance liquid chromatography (perfusion RP-HPLC) is applied for the first time to the determination of soybean proteins in commercial samples prepared from soybean protein isolate. A linear binary gradient of acetonitrile-water-0.1% trifluoroacetic acid at a flow rate of 3 mL/min and a temperature of 60 degrees C is optimized to analyze soybean proteins in approximately 3 min. Direct injection of samples into the chromatographic system is possible by dissolving them in water. Quantitation of soybean proteins is achieved by the proposed method using a soybean protein isolate as an external standard. The method is validated and applied to the quantitation of soybean proteins in infant formulas and powdered and liquid soybean milks.

Determination of polychlorinated biphenyls in soybean infant formulas by gas chromatography

A method previously developed for the analysis of organohalogenated compounds in dairy products is now validated for polychlorinated biphenyls (PCBs) determination in soybean infant formulas. The results of this study are consistent with those found for PCBs in powdered full-fat milk. The methodology is based on a solid-liquid extraction step enabling a semi-selective extraction of the apolar lipids of the matrix without affecting the efficiency for the recovery of PCBs. Mean recoveries for the spiked coplanar congeners studied were in the 88-114% range, with relative standard deviations (R.S.D.s) lower than 9.8%. The R.S.D.s related to the determination of endogenous PCBs were in the 1.5-10.0% range. The validated methodology was applied to the PCB analysis in different trademarks of soybean infant formulas commercialised in Spain. Toxic tetraequivalents of tetrachlorodibenzo-p-dioxin and daily intake corresponding to each one were calculated and compared with values previously published and with those found in literature for human breast milk in different countries.

Ultrarapid detection of bovine whey proteins in powdered soybean milk by perfusion reversed-phase high-performance liquid chromatography

A perfusion reversed-phase high-performance liquid chromatographic method has been developed to simultaneously separate soybean and bovine whey proteins (alpha-lactalbumin and beta-lactoglobulins (A + B)) in a very short analysis time (approximately 5 min). The method consisted of a linear binary gradient water-acetonitrile-0.10% trifluoroacetic acid at a flow-rate of 3 ml/min, with the column thermostated at 60 degrees C, and ultraviolet detection at 254 nm. This method enables the rapid detection of adulterations of powdered soybean milks by addition of bovine whey proteins. When bovine whey proteins were too low to be detected by direct injection of the sample, a previous acidic precipitation step was required in order to concentrate these proteins. Quantitatve analysis of bovine whey proteins was also successfully performed. In fact, it was possible to detect about 1% and 1.3% of alpha-lactalbumin and beta-lactoglobulins, respectively, in a commercial powdered soybean milk in which these proteins were included in its formulation. Results were compared with those obtained by conventional reversed-phase high-performance liquid chromatography.

Chiral separation of polychlorinated biphenyls by micellar electrokinetic chromatography with sodium cholate

Micellar electrokinetic chromatography (MEKC) with one kind of bile salt (sodium cholate) was used to separate three chiral polychlorinated biphenyls (PCBs; 84, 95, and 176), each one in its two enantiomers. Sodium cholate was used as chiral surfactant in a 2-(N-cyclohexylamino) ethanesulfonic acid (CHES) buffer under alkaline (pH 10) conditions containing urea (2 M). The influence of bile salt concentration on the efficiency and the resolution between the two enantiomers of PCBs 84 and 95 was established. The chiral separation of three PCBs was successfully achieved in less than 30 min (approximately 23 min for PCB 176 and approximately 29 min for PCBs 84 and 95).