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.

Magnetic nanoparticles coated with carboxylate-terminated carbosilane dendrons as a reusable and green approach to extract/purify proteins

Extraction/purification of proteins, at both analytical and industrial levels, is a limiting step that usually requires the use of organic solvents and involves tedious work and a high cost. This work proposes a more sustainable alternative based on the use of magnetic nanoparticles (MNPs) coated with carboxylate-terminated carbosilane dendrons. MNPs coated with first- and second-generation carbosilane dendrons and bare MNPs were employed for the extraction of proteins with different molecular weights and charges. Interaction of proteins with MNPs significantly varied with the pH, the protein, and the dendron generation (different sizes and number of charges in the periphery). Optimal dendron:protein molar ratios and suitable conditions for disrupting interactions after protein extraction were also researched. Second-generation dendron-coated MNPs showed 100% retention capability for all proteins when using acidic conditions. They were reused without losing magnetism or interaction capacity after a disruption of protein-dendron interactions with 0.2% SDS at 100 °C for 10 min. The capacity of dendron-coated MNPs was successfully applied to the recovery/purification of proteins from two food by-products, olive seeds and cheese whey.

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.

Immobilization of thermolysin enzyme on dendronized silica supports. Evaluation of its feasibility on multiple protein hydrolysis cycles

This work evaluates different dendrimer-silica supports for the immobilization of enzymes by multipoint covalent binding. Thermolysin was immobilized on two dendrimers (PAMAM and carbosilane) with two different generations (zero (G0) and first (G1)). Results were compared with a control, a silica support functionalized with a monofunctional molecule. Dendrimers increased the number of available sites to bind the enzyme. Despite the enzyme was immobilized on all supports, G0 dendrimers immobilized a 30% more enzyme than G1. Thermolysin immobilized on G0 dendrimer supports showed the highest activity and could be employed in three consecutive hydrolysis cycles. Optimal immobilization time was 1 h while optimal protein loading was 25 mg enzyme/100 mg support. Enzyme activity was promoted when using 5 mg of immobilized enzyme at 750 rpm, 60 °C, and 2 h of hydrolysis. Under these conditions, the activity of thermolysin increased up to the 78% of the free enzyme activity. Kinetics of the hydrolysis reaction using the immobilized thermolysin was also studied and compared with the obtained using the free thermolysin. The addition of ZnCl₂ and NaCl during the immobilization procedure increased thermolysin activity in the second (22% more) and in the third (14% more) hydrolysis clycles.

Evaluation of the relationship between the peptide profiles and the lipid-lowering properties of olive seed hydrolysates as a tool for tuning hypocholesterolemic functionality

Olive processing generates large amounts of stones with high protein contents. Previous studies have demonstrated that Manzanilla variety olive seed proteins release peptides with lipid-lowering capacity. However, no work has demonstrated their roles in the overall hypolipidemic activity. Moreover, further studies using different olive varieties are required to propose a solid method for the exploitation of olive seeds. Twenty different olive varieties were employed in this work. Proteins were extracted using high-intensity focused ultrasound and digested with Alcalase. The released peptides were identified using proteomic techniques, and their capabilities to reduce the absorption of dietary cholesterol (by inhibiting cholesterol esterase enzyme, binding bile acids, and reducing micellar cholesterol solubility) or the biosynthesis of endogenous cholesterol were evaluated. Peptides with different lipid lowering capacities were obtained from all varieties although the genotype significantly affected the hypolipidemic characteristics. Univariate and multivariate statistical analyses showed strong correlations, positive and negative, between the presence of certain peptides in the hydrolysates and their capacity to reduce exogenous cholesterol absorption and endogenous cholesterol synthesis. Therefore, the selection of the olive seed genotype can direct its lipid-lowering properties, e.g., by promoting the reduction of dietary cholesterol absorption or the inhibition of cholesterol biosynthesis.

Identification of Peptides Potentially Responsible for In Vivo Hypolipidemic Activity of a Hydrolysate from Olive Seeds

Previous studies demonstrated that peptides produced by the hydrolysis of olive seed proteins using Alcalase enzyme showed in vitro multifunctional lipid-lowering capability. This work presents a deeper insight into the hypolipidemic effect of olive seed peptides. The capability of olive seed peptides to inhibit endogenous cholesterol biosynthesis through the inhibition of HMG-CoA reductase enzyme was evaluated observing a 38 ± 7% of inhibition. Two in vivo assays using different peptides concentrations (200 and 400 mg/kg/day) were designed to evaluate the hypolipidemic effect of olive seed peptides in male and female mice. A low concentration of hydrolysate reduced total cholesterol in male mice in a 20% after 11 weeks compared to the mice feeding with hypercholesterolemic diet. A higher hydrolysate concentration showed a greater reduction in total cholesterol (25%). The analysis of the olive seed hydrolysate by reverse phase high-performance liquid chromatography mass spectrometry (RP-HPLC-MS) enabled the identification of peptides that could be responsible for this hypolipidemic effect.

Isolation and Characterization of Angiotensin Converting Enzyme Inhibitory Peptides from Peach Seed Hydrolysates: In Vivo Assessment of Antihypertensive Activity

A peptide fraction with molecular masses below 3 kDa (PSH-3 kDa) from a peach seed hydrolysate demonstrated high angiotensin converting enzyme (ACE) inhibitory activity (concentration to inhibit 50% ACE (IC₅₀) = 16.4 μg/mL) in our previous work. This work proposes a further study of this highly active fraction. RP-HPLC enabled two fractions (F3 and F4) with high inhibitory activity (IC₅₀ = 2.0 ± 0.5 and 1.2 ± 0.2 μg/mL, respectively) to be isolated. Peptide analysis by LC-Q-TOF-MS/MS using reverse-phase and hydrophilic interaction chromatography enabled 33 peptides within both fractions to be identified. Among them, peptide isoleucine-tyrosine-serine-proline-histidine (IYSPH) showed the highest capacity. The lack of cytotoxicity of peptides was demonstrated in three different cell lines (HeLa, HT-29, and HK-2). Oral administration of PSH-3 kDa fraction or peptide IYSPH caused a significant systolic blood pressure reduction (-30 mmHg) on spontaneously hypertensive rats after 3-6 h treatment.

Isolation and identification by high resolution liquid chromatography tandem mass spectrometry of novel peptides with multifunctional lipid-lowering capacity

This work describes the isolation, characterization, and identification by RP-HPLC-ESI-Q-TOF of novel peptides that interfere in the fat digestion and absorption mechanisms by multiple pathways. Peptides were ultrafiltrated and peptides in the most active fraction were further separated by semipreparative RP-HPLC. Nine different subfractions were obtained observing a high amount of peptides in subfraction F3. Peptides in subfraction F3 could simultaneously reduce the solubility of cholesterol in micelles and inhibit pancreatic cholesterol esterase and pancreatic lipase, even after a simulated gastrointestinal digestion. The identification of lipid-lowering peptides has been scarcely performed and when done, low selectivity or sensitivity of employed identification techniques or conditions did not yield reliable results. Separation and detection of peptides by RP-HPLC-ESI-Q-TOF-MS was optimized and most favorable conditions were employed for the identification of peptides using de novo sequencing. Ten different peptides with 4-9 amino acids were identified. Main feature of identified peptides was the high acidity derived from a high presence of amino acids glutamic acid and aspartic acid in their sequences.

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.

Derivatization in Capillary Electrophoresis

Capillary electrophoresis is a well-established separation technique in analytical research laboratories worldwide. Its interesting advantages make CE an efficient and potent alternative to other chromatographic techniques. However, it is also recognized that its main drawback is the relatively poor sensitivity when using optical detection. One way to overcome this limitation is to perform a derivatization reaction which is intended to provide the analyte more suitable analytical characteristics enabling a high sensitive detection. Based on the analytical step where the CE derivatization takes place, it can be classified as precapillary (before separation), in-capillary (during separation), or postcapillary (after separation). This chapter describes the application of four different derivatization protocols (in-capillary and precapillary modes) to carry out the achiral and chiral analysis of different compounds in food and biological samples with three different detection modes (UV, LIF, and MS).

Identification of native angiotensin-I converting enzyme inhibitory peptides in commercial soybean based infant formulas using HPLC-Q-ToF-MS

This work evaluates, the presence of native antihypertensive peptides in five soybean-based infant formulas (SBIFs). SBIFs peptide extracts (<10 kDa) and their sub-fractions (5-10 kDa, 3-5 kDa, and <3 kDa) from a variety of samples were obtained by ultrafiltration and ACE inhibitory activity was determined. The highest activities were observed in the smaller (<5 kDa) peptide fractions. A set of peptides present in various SBIFs were studied, and identified using HPLC-Q-ToF-MS. Despite ACE inhibitory activity decreasing after in vitro gastrointestinal digestion, it still remained at a high value (IC50 values of 18.2±0.1 and 4.9±0.1 μg/mL). Peptides resisting the action of gastrointestinal enzymes were identified and compared to previously identified peptides, highlighting the presence of peptide RPSYT. This peptide was synthesised, its antihypertensive and antioxidant activity were evaluated, and its resistance to in vitro gastrointestinal digestion and to high processing temperatures were studied.

Development of a capillary high performance liquid chromatography-ion trap-mass spectrometry method for the determination of VLIVP antihypertensive peptide in soybean crops

Soybean peptide VLIVP presents a very high antihypertensive activity (IC50 value 1.69μM), even higher than extensively studied IPP and VPP peptides from milk. Nevertheless, no much attention has been paid to this peptide and there is no method enabling its determination in soybeans. The aim of this work was the development of an analytical methodology for this purpose. A methodology consisting of the extraction of soybean proteins, their digestion with Protease P enzyme, their chromatographic separation using capillary-HPLC, and IT-MS detection was optimized. Protein extraction was performed by the use of high intensity focused ultrasounds to obtain a reduced extraction time. Optimization of chromatographic and mass spectrometry parameters enabled the separation of VLIVP peptide within just 7min and its sensitive detection. The analytical characteristics of the capillary-HPLC-IT-MS method were evaluated through the study of linearity, LOD, LOQ, study of the presence of matrix interferences, precision, and recovery. The method enabled to detect as low as 3.6ng of peptide and to determine as low as 12ng of peptide in 1g of soybean (as dry basis). Finally, the developed method was applied to the determination of the antihypertensive peptide VLIVP in different soybean varieties. The results showed the highest yield of VLIVP peptide in variety Mazowiecka II from Poland.

Isolation and identification of antioxidant peptides from commercial soybean-based infant formulas

Soybean-based infant formulas (SBIFs) based on soybean protein isolate (90% of proteins) are an interesting alternative to cow's milk infant formulas. Different works have demonstrated the presence of bioactive peptides in different soybean-based foodstuffs. The aim of this work was the evaluation, for the first time, of antioxidant peptides in five different commercially available SBIFs. Ultrafiltration through 10 kDa molecular weight cut-off filters was the most suitable extraction method. Despite peptide concentrations ranging between 1.19 and 2.27 mg/mL, similar antioxidant capacities were detected in all SBIF extracts. Extracts were further fractionated according to their molecular weight by ultrafiltration, and fractions from 5 to 10 kDa, 3 to 5 kDa, and below 3 kDa were obtained. The most active fraction was further fractionated by off-gel isoelectrofocusing and reversed-phase chromatography. Antioxidant fractions were also submitted to simulated gastrointestinal digestion (GI) with pepsin and pancreatin to evaluate their antioxidant capacity after digestion. Peptides were identified by HPLC-ESI-Q-ToF-MS/MS. At least 120 peptides were identified in every antioxidant fraction, with 42 peptides common to all SBIFs.

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.

Development of a high-performance liquid chromatography-electrospray ionization-quadrupole-time-of-flight-mass spectrometry methodology for the determination of three highly antihypertensive peptides in maize crops

The simultaneous quantification of three highly antihypertensive peptides (LRP, LSP, and LQP) in six maize crops using novel HPLC-ESI-Q-ToF methodology is presented. The method included the extraction of α-zein proteins from maize, their purification by acetone precipitation, digestion with thermolysin and HPLC separation in a fused-core column. Several MS parameters were optimized to increase sensitivity and reduce spontaneous fragmentation of peptide ions into the ESI source. The ions with m/z 193.1315, 385.2558 (for LRP), 316.1867 (for LSP), and 357.2132 (for LQP) were monitored in the optimization and characterization of the method. In order to improve the repeatability, sensitivity, and the stability of peptides in the sample, the removal of urea was required. The use of two solid-phase extraction methods to remove urea from digested extract was evaluated. For the first time filter-aided sample preparation approach for the study of bioactive peptides in foodstuffs has been proposed. The optimized HPLC-ESI-Q-ToF method was characterized by the evaluation of linearity, LOD, LOQ, precision, and recovery. A study on the existence of matrix interferences was also performed. The developed method was applied to the quantification of LRP, LQP, and LSP peptides in maize lines using the standard addition method. The results showed the highest yield of LSP peptide in EZ11A line and LRP and LQP peptides in A632 line.

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.

Development of an ultra-high performance liquid chromatography analytical methodology for the profiling of olive (Olea europaea L.) pulp proteins

Ultra-high performance liquid chromatography (UHPLC) constitutes an interesting proposal to speed protein separations but it is almost not explored. In this work UHPLC is proposed, for the first time, to separate olive pulp proteins. An important difficulty in the analysis of proteins is related to their extraction. The difficulty in the extraction of proteins from the olive pulp is derived from its high content in lipids and phenolic compounds. Eight different methods for the extraction of pulp proteins were designed and evaluated. The optimized extraction procedure consisted of a cleaning step to remove interfering compounds, followed by the extraction of proteins with a Tris-HCl buffer containing sodium dodecyl sulphate (SDS) and dithiothreitol (DTT), precipitation of proteins with acetone, and solubilization in the Tris-HCl buffer. This methodology yielded the most successful isolation of pulp proteins and enabled the optimization of a UHPLC methodology for their separation. The method was applied to the profiling of olive pulp proteins from different olive cultivars observing in all cases a protein that had never been described before.

Simultaneous and rapid determination of the anticarcinogenic proteins Bowman-Birk inhibitor and lectin in soybean crops by perfusion RP-HPLC

There are numerous studies demonstrating a direct association between the ingestion of soybean and low cancer incidence. This fact has been related to the presence of Bowman-Birk inhibitor (BBI) and lectin in soybean. The simultaneous and fast determination of BBI and lectin in soybean is proposed, for the first time, in this work. Two different strategies were designed for the extraction of BBI and lectin: extraction of soybean proteins using a Tris-HCl buffer followed by isolation of BBI and lectin by the isoelectric precipitation of other soybean proteins (method I) or by the direct extraction of BBI and lectin using an acetate buffer (method II). The effect of the previous soybean defating on the extraction of BBI and lectin was also studied. Moreover, the possibility of using a high-intensity focalized ultrasonic probe for accelerating the extraction was explored and an optimization of the extraction time and ultrasound amplitude was performed. The extracts obtained were analysed by RP-HPLC-ESI-MS for the correct identification of BBI and lectin in soybean. Moreover, a fast chromatographic methodology using a perfusion column and UV detection was optimized for the rapid determination of BBI and lectin in soybean. After evaluating its analytical characteristics (linearity, precision, and recovery), the method was applied to the quantitation of BBI and lectin in different soybean varieties.

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.

Separation and online preconcentration by multistep stacking with large-volume injection of anabolic steroids by capillary electrokinetic chromatography using charged cyclodextrins and UV-absorption detection

The separation of three common anabolic steroids (methyltestosterone, methandrostenolone and testosterone) was performed for the first time by capillary EKC. Different charged CD derivatives and bile salts were tested as dispersed phases in order to achieve the separation. A mixture of 10 mmol/L succinylated-beta-CD with 1 mmol/L beta-CD in a 50 mmol/L borate buffer (pH 9) enabled the separation of the three anabolic steroids in less than 9 min. Concentration LODs, obtained for these compounds with low absorption of UV light, were approximately 5 x 10(-5) mol/L. The use of online reverse migrating sample stacking with large-volume injection (the effective length of the capillary) enabled to improve the detection sensitivity. Sensitivity enhancement factors (SEFs) ranging from 95 (for testosterone) to 149 (for methyltestosterone) were achieved by single stacking preconcentration. Then, the possibilities of multistep stacking to improve the sensitivity for these analytes were investigated. SEFs obtained by double stacking preconcentration ranged from 138 to 185, enabling concentration LODs of 2.79 x 10(-7) mol/L (for methyltestosterone), 3.47 x 10(-7) mol/L (for testosterone) and 3.56 x 10(-7) mol/L (for methandrostenolone). Although online triple stacking preconcentration was achieved, its repeatability was very poor and SEFs for the studied analytes were not calculated.

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.

Separation and quantitation of the four stereoisomers of itraconazole in pharmaceutical formulations by electrokinetic chromatography

The four stereoisomers of itraconazole were resolved for the first time by EKC using a CD as chiral selector. A study on the enantiomeric separation ability of different neutral CDs was carried out. Heptakis-2,3,6-tri-O-methyl-beta-CD was shown to provide the highest values for the enantiomeric resolution. The influence of some experimental conditions, such as pH, chiral selector concentration, and temperature, on the enantiomeric separation was also studied. The use of a 100 mM phosphate buffer (pH 2.5), 30 mM in heptakis-2,3,6-tri-O-methyl-beta-CD together with an applied voltage of 30 kV and a temperature of 20 degrees C enabled the separation of the enantiomers of itraconazole with high resolutions (Rs > 3.0). Finally, the method was validated and successfully applied to the quantitation of itraconazole in three pharmaceutical formulations.

High-performance liquid chromatography and capillary electrophoresis for the analysis of maize proteins

Methods for the analysis of maize proteins using HPLC and CE are reviewed. Most of the references cited in this review concern HPLC methods. Size-exclusion HPLC and especially RP-HPLC methods have been developed for characterization of normal and genetically modified maize, cultivar differentiation, and prediction of quality. Few CE methods for the analysis of maize proteins were found in the existing literature. Most of these methods focus on optimization of the separation of maize proteins using CZE and SDS-capillary gel electrophoresis.

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.

Enantiomeric separation of ketoconazole and terconazole antifungals by electrokinetic chromatography: Rapid quantitative analysis of ketoconazole in pharmaceutical formulations

EKC using a neutral CD as chiral selector was applied in this work to the development of a method enabling the enantiomeric separation of ketoconazole and terconazole antifungals. The influence of different experimental conditions such as temperature, CD concentration, pH, and nature and concentration of the buffer on the enantiomeric resolution of the compounds studied was investigated. The use of 10 mM heptakis-(2,3,6-tri-O-methyl)-beta-CD in a 100 mM phosphate buffer (pH 3.5) with a temperature of 15 degrees C allowed the separation of the enantiomers of ketoconazole and terconazole with high resolution (R(s) > 2.0). The rapid separation of ketoconazole enantiomers with an analysis time less than 3 min was carried out after fitting some experimental parameters. The developed method was applied to the determination of ketoconazole in different pharmaceutical formulations.

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.

Separation of etodolac enantiomers by capillary electrophoresis. Validation and application of the chiral method to the analysis of commercial formulations

Separation of etodolac enantiomers, which exhibit different biological activity and pharmacokinetic profiles, has been achieved using the randomly substituted (2-hydroxy)propyl-beta-cyclodextrin (HP-beta-CD) as chiral selector in capillary electrophoresis. The selection of this CD was made after screening of different CD derivatives of neutral and anionic nature. The effect on the enantioresolution of the buffer concentration and of the degree of substitution (DS) and concentration of the CD as well as of instrumental parameters, such as the capillary temperature and the separation voltage, were studied. The highest resolution of etodolac enantiomers was around 2.5 using 100 mM phosphate buffer (pH 7.0) with 20 mM HP-beta-CD (DS approximately 4.2) and UV detection at 225 (10) nm with a reference wavelength at 360 (50) nm. Validation of the chiral method in terms of selectivity, linearity, precision (instrumental repeatability, method repeatability, intermediate precision), and the limits of detection and quantitation allowed to evaluate its quality to the analysis of etodolac enantiomers in different pharmaceutical preparations containing racemic etodolac.

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.

Chiral capillary electrophoresis applied to the determination of phenylglycidol enantiomers obtained from cinnamyl alcohol by asymmetric epoxidation using new titanium(IV) alkoxide compounds as catalysts

A capillary electrophoresis method for the simultaneous determination of phenylglycidol enantiomers in the presence of an excess of cinnamyl alcohol was developed. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of methanol or acetonitrile, and the capillary temperature on the chiral resolution of phenylglycidol enantiomers were studied. Separations were achieved using 20 mM succinylated beta-cyclodextrin dissolved in a 10 mM borate buffer (pH 10.0). Chiral resolution for the phenylglycidol enantiomers in the optimized electrophoretic conditions was higher than 2.0 with an analysis time less than 7 min. The method developed was validated in terms of selectivity, linearity, precision (instrumental repeatability, method repeatability, intermediate precision), the limits of detection and quantitation, and accuracy. Limits of detection of 6.5 mg/L and 8.3 mg/L for (2S,3S)-(-)-3-phenylglycidol ((S,S)-PG) and (2R,3R)-(+)-3-phenylglycidol ((R,R)-PG), respectively, were obtained. The method was applied to study the asymmetric epoxidation of cinnamyl alcohol with titanium(IV) alkoxide compounds as catalysts in order to evaluate their catalytic activity and stereoselectivity of the epoxidation processes.

Study of the biodegradation process of polychlorinated biphenyls in liquid medium and soil by a new isolated aerobic bacterium (Janibacter sp.)

We have isolated and characterised a novel aerobic bacterial strain, designated MS3-02, belonging to the genus Janibacter sp. The capability of this new strain to degrade polychlorinated biphenyls (PCBs) in a commercial mixture (Aroclor 1242) in liquid medium and in soil (sterile and non sterile soil), under laboratory scale, has been evaluated. MS3-02 was isolated from the soil around of an incinerator, located in the east of Madrid (Spain). Gas-chromatographic analysis showed that MS3-02 was able to reduce most peaks observed in the chromatogram between 70% and 100% after seven days of incubation in a culture mineral medium containing yeast extract, but without the addition of biphenyl. The presence of biphenyl in the culture medium decreased the rate of PCB degradation by this bacterium. Comparing the performance of the MS3-02 in liquid culture medium and in soil, degradation was less efficient in sterile soil and still less efficient in non sterile soil. Under the best conditions (sterile soil and 20 weeks of incubation) MS3-02 was able to reduce, between 50% and 100%, nine of the main gas-chromatographic peaks in Aroclor 1242.

Comparison of charged cyclodextrin derivatives for the chiral separation of atropisomeric polychlorinated biphenyls by capillary electrophoresis

Charged cyclodextrin (CD) derivatives were used as chiral selectors in electrokinetic chromatography (EKC) for the chiral separation of highly hydrophobic neutral racemates such as atropisomeric polychlorinated biphenyls (PCBs). beta-CD-phosphated, beta-CD sulfated, succinylated-gamma-CD (Succ-gamma-CD) and succinylated-beta-CD (Succ-beta-CD) were used as anionic CDs. As cationic CD, 6-monodeoxy-6-monoamino-beta-CD (beta-CD-NH(2)) was tested for the first time in order to separate PCBs. From the different CD derivatives employed, the best separations were obtained with the cationic CD derivative. Thus, the use of beta-CD-NH(2 )in phosphate buffer at pH 2.0 containing urea allowed the chiral recognition of eleven PCBs (45, 84, 88, 91, 95, 131, 136, 144, 149, 176, and 197). In this case, the addition of 2 M urea to the buffer solution was crucial to achieve the chiral separation of PCBs. The addition of acetonitrile to 10 mM phosphate buffer (pH 2.0) with 30 mM beta-CD-NH(2) and 2 M urea improved considerably the chiral resolution obtained for PCBs 91, 95, 136, 144, 149, and 197 although an increase in the analysis time was also observed. All the results obtained were compared with those previously obtained with the dual CD system carboxymethyl-gamma-CD/beta-CD.

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.