Records of cattle slaughtered at two Chilean slaughterhouses (SLH1 and SLH2) were used to determi... more Records of cattle slaughtered at two Chilean slaughterhouses (SLH1 and SLH2) were used to determine prevalence and risk factors for carcasses with bruises. Bruise prevalence amounted to 12.3% but differed between slaughterhouses (20.8% for SLH1 and 8.6% for SLH2 respectively). Bruise severity grade 1 (mild) was most frequently recorded. The type of the animal, source of animal, the level of fat cover and lairage time were associated with the presence of bruises. Older categories of animals and animals that pass through a market before being moved to the slaughterhouse are more prone to show bruises. The results also indicate that under the reported Chilean circumstances animals that have longer lairage times (over 12 h) have a significantly reduced risk for bruises, except for oxen. Presence of bruises is also significantly associated with increased carcass pH values.
Degradation processes of amitraz in aqueous media have been studied by spectrophotometry, HPLC an... more Degradation processes of amitraz in aqueous media have been studied by spectrophotometry, HPLC and GC-MS. Amitraz undergoes hydrolysis reactions at any pH, but towards the acidic pH range hydrolysis proceeds at a faster rate. Depending on the pH value, different products of the hydrolysis have been identified. The main degradation products are 2,4-dimethylaniline at very acidic pH values (pH<3), N-(2,4-dimethylphenyl)-N'-methylformamidine and 2,4-dimethylphenylformamide at less acidic media (pH 3-6) and 2,4-dimethylphenylformamide at basic pH. The mechanisms of the different hydrolysis processes have been elucidated.
A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC proce... more A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure is reported for the assay of papaverine, diltiazem, desipramine and nicardipine in urine. Disposable extraction cartridges (DECs) filled with C18, C8, C2, CH and PH silica-bonded phases were used. The effect on recovery of sample pH, composition of washing and elution solvents and nature of SPE cartridge were evaluated. The selectivity of SPE was examined using spiked urine samples and the PH cartridge gave rise to the cleanest extracts. Phenyl cartridges were conditioned with methanol and acetic acid-sodium acetate buffer. Urine sample was buffered and then applied to the DEC. The washing step was with acetone-water and subsequently with methanol-acetate buffer. The analytes were eluted with methanol-acetate buffer. The extract was evaporated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with UV detection at 212 nm. Recoveries of the tested compounds from spiked urine samples using the PH cartridge were in all cases>80%. The within-day and between-day repeatabilities were<5% and 9%, respectively.
A review with 178 references on the basic principles and recent developments in the solid phase e... more A review with 178 references on the basic principles and recent developments in the solid phase extraction is presented. New solid phases, chromatographic modes, experimental configurations and off-line and on-line automated devices are discussed.
Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiol... more Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiolysis, in order to characterise and differentiate these beverages and then develop a classification system capable of confirming the authenticities of both kinds of cider. A data set consisting of 165 cider samples and 27 measured features was evaluated using multivariate chemometric techniques, such as cluster analysis and principal component analysis, in order to perform a preliminary study of data structure. Supervised pattern recognition techniques such as linear discriminant analysis (LDA), K-nearest neighbours (KNN), soft independent modelling of class analogy (SIMCA), and multilayer feed-forward artificial neural networks (MLF-ANN) attained classification rules for the two categories using the chemical data, which produced satisfactory results. Authentication systems obtained by combining two of these techniques were proposed. We found that SIMCA and LDA or KNN models achieved 100% hit-rates, since LDA and KNN permit the detection of every Basque cider and SIMCA provides a model for Basque cider that excludes all French ciders. Polyphenolic profiles of the ciders provided enough information to be able to develop classification rules for identifying ciders according to their geographical origin (Basque or French regions). Chemical and organoleptic differences between these two types of cider are probably due to the original and distinctive cidermaking technologies used for their elaboration. Using polyphenic profiles, about 80% of French ciders could be distinguished according to their region of origin (Brittany or Normandy). Although their polyphenolic profiles did not provide enough information to achieve an authentication system for Breton and Norman ciders.
A method is reported for the first time for the determination in beeswax of several acaricides us... more A method is reported for the first time for the determination in beeswax of several acaricides used for the control of the bee parasite Varroa destructor. The method was optimized and validated for amitraz residues in wax and was applied to the determination of other acaricides: bromopropylate (BP), chlordimeform, cymiazole and chlorfenvinphos. It consists of a methanol extraction step, cleanup by solid-phase extraction (SPE) with octadecylsilica and determination by capillary gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) detection. The limits of detection for the different substances were between 0.02 and 0.2 mg/kg, and the recoveries, between 40 and 95%.
Polyphenols in the peel and pulp of 15 Basque cider apple varieties were determined by accelerate... more Polyphenols in the peel and pulp of 15 Basque cider apple varieties were determined by accelerated solvent extraction followed by reversed phase high-performance liquid chromatography with diode array detection. It was observed that the polyphenolic composition in apple peel depended on varieties, whereas the main classes of phenolic compounds in apple pulp were flavan-3-ols and hydroxycinnamic acids in all cases, representing both together between 86 and 95% of total polyphenols assayed.
A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chroma... more A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure is reported for the assay of a wide polarity range acaricide residues in honey. After selection of suitable chromatographic and detection conditions, most steps of the SPE procedure that may affect to the recovery were investigated. Honey sample was buffered at pH 6 and then applied to the preconditioned C18 sorbent. A washing step was performed with 1 ml of a mixture of tetrahydrofuran (THF)-phosphate buffer (10:90, v/v) and finally, the analytes were eluted with 1 ml of THF. The extract was evaporated to dryness, reconstituted in mobile phase and chromatographed on a reversed-phase C18 column with diode array detection. The recoveries of the more polar acaricides were higher than 80% and 60-70% for the more apolar ones. Limits of detection obtained ranged from 1 to 200 ng/g.
Total polyphenol contents, estimated by Folin-Ciocalteu method, and CIELab chromatic parameters w... more Total polyphenol contents, estimated by Folin-Ciocalteu method, and CIELab chromatic parameters were determined in Basque and French ciders with the aim of developing a classification system to confirm the authenticity of ciders. A preliminary study of data structure was performed by a multivariate data analysis using chemometric techniques such as cluster analysis and principal component analysis. Supervised pattern recognition methods, such as linear discriminant analysis, K-nearest neighbours (KNN), soft independent modelling of class analogy and multilayer feed-forward artificial neural networks (MLF-ANN), provided classification rules for the two categories based on the experimental data. KNN results for Basque ciders afforded an excellent performance in terms of recognition and prediction abilities (99%), providing a useful tool to detect genuine Basque ciders. Despite KNN and MLF-ANN giving the best results for French ciders, with a success rate of prediction ability around 91%, this would not be acceptable for authentication purposes.
Apple polyphenols were characterised by means of hyphenated techniques such as HPLC coupled to UV... more Apple polyphenols were characterised by means of hyphenated techniques such as HPLC coupled to UV photodiode array detection (LC-DAD) and to mass spectrometry (LC-MS). LC-MS using atmospheric pressure ionisation (APCI) in the positive ion mode provided the molecular weight, the number of hydroxyl groups, the number of sugars and an idea about the substitution pattern of the polyphenols. LC-DAD with postcolumn addition of UV shift reagents afforded precise structural information about the position of the free hydroxyl groups in the polyphenolic nucleus. Five isorhamnetin glycosides, two hydroxyphloretin glycosides and quercetin were reported in apple peel for the first time. Postcolumn addition of UV shift reagents in LC-DAD analysis confirmed the presence of isorhamnetin glycosides and not the isomeric glycosides of rhamnetin. Moreover, isorhamnetin-3-O-rhamnoglucoside was identified unambiguously by comparison with a standard. These results are relevant not only from a chemotaxonomic point of view, but also in the control of authenticity of fruit derived products in order to detect fraudulent admixtures.
A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-perfor... more A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection is reported for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils. The effects of experimental variables, such as washing and elution solvents, sample solvent and drying time have been studied using C cartridges. Recoveries and selectivity using other sorbent materials (C , C , CH, PH and 18 8 2 NH ) were also examined, with C being the best one. The recoveries ranged between 50 and 103% depending on the 2 1 8 molecular mass of the PAH. The limits of quantitation were lower than 1 ng / g for most PAHs and good precision was achieved. The method was validated using certified reference materials.
A solvent extraction procedure of freeze-dried aliquots followed by the analysis of phenolic comp... more A solvent extraction procedure of freeze-dried aliquots followed by the analysis of phenolic compounds by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detection (DAD) has been developed for the analysis of polyphenolic compounds in fruit juices. This methodology is focussed on the characterization of fruit juices, mainly for quality control purposes. The effects of experimental variables, such as solvent composition and volume and time and temperature on extraction, have been studied. A unique gradient program for the separation of several phenolic classes (hydroquinones, hydroxybenzoic acids, flavan-3-oles, hydroxycinnamic acids, coumarins, flavanones, flavones, dihydrochalcones and flavonols) has been optimized, using standards of 55 commercially available phenolic compounds present in fruits, as well as representative real extracts from fruit juices. All phenolic compounds showed a high repeatability within-day (n = 5) and between days (n = 3) in peak area (RSD < 8%) and excellent stability of their retention times. High precision was also observed in calibration slopes (RSD < 8%). Detection limits ranged between 0.005 and 0.03 g/mL for the different detected polyphenols. Complete recoveries (98-100%) were obtained for the majority of the phenolic structures of all representative phenolic families present in fruits. The method was successfully employed to measure diverse phenolic families in juices from 18 different fruits and consequently could be used for evaluate the quality of fruit juices.
The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, a... more The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography with diode array detection analysis of crude extracts and after thiolysis. Total polyphenols are distributed in a wide concentration range depending on the cultivar. Procyanidins are the class of polyphenols that present major concentrations in apple. Their average degrees of polymerization range from 4 to 8 depending on the cultivar. Apple cultivars were technologically classified into bitter and nonbitter categories using different classification systems obtained by applying several pattern recognition techniques, such as principal component analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed-forward-artificial neural networks, to apple pulp, peel, or juice data (individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins). Bitter apple cultivars present higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Detailed knowledge of the polyphenolic profile of each apple cultivar affords information about their susceptibility to oxidation, their sensory properties (bitterness, astringency), and their possible influence on the characteristics and quality of the final product (juice, cider) when apples are processed.
... The dried tissues were crushed in closed vials to avoid hydration, using stainless-steel ball... more ... The dried tissues were crushed in closed vials to avoid hydration, using stainless-steel balls ( 1 cm) and an ... acid (30:69:1, v/v/v) with ascorbic acid (2 g/l) in an ultrasonic bath during ... which was performed by dividing the complete data set into a training set and an evaluation set. ...
A study on the possible degradation of amitraz, bromopropylate, coumaphos, chlordimeform, cymiazo... more A study on the possible degradation of amitraz, bromopropylate, coumaphos, chlordimeform, cymiazole, flumethrin, and tau-fluvalinate during the storage of honey was carried out by HPLC. Except amitraz, the other acaricides are stable in this medium for at least 9 months. Degradation studies of amitraz in honey and beeswax were carried out; the degradation products detected in both matrices were 2,4-dimethylphenylformamide (DMF) and N-(2,4-dimethylphenyl)-N′-methylformamidine (DPMF). The reaction rate constants and the half-lives of the amitraz degradation in honey and wax were calculated. Amitraz was nearly completely degraded within 1 day in beeswax and within 10 days in honey. When amitraz-spiked combs are recycled into new beeswax, DMF was found to be the principal degradation product left in pure wax.
Journal of Chromatography B: Biomedical Sciences and Applications, 1993
A reversed-phase high-performance liquid chromatographic method for oxazepam in human urine sampl... more A reversed-phase high-performance liquid chromatographic method for oxazepam in human urine samples has been developed. The sample preparation consists of an enzymatic hydrolysis with beta-glucuronidase, followed by a solid-phase extraction process using Bond-Elut C2 cartridges. The mobile phase used was a methanol-water (60:40, v/v) mixture at a flow-rate of 0.50 ml/min. The column was a 3.5 cm x 4.6 mm I.D. C18 reversed-phase column. The detection system was based on a fluorescence post-column derivatization of oxazepam in mixtures of methanol and acetic acid. A linear range from 0.01 to 1 micrograms/ml of urine and a limit of detection of 4 ng/ml of urine were attained. Within-day recoveries and reproducibilities from urine samples spiked with 0.2 and 0.02 microgram/ml oxazepam were 97.9 and 95.0 and 2.1 and 9.4%, respectively.
The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, a... more The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography--diode array detection analysis of crude extracts and after thiolysis. Data sets, consisting of individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins, were evaluated by multivariate chemometric techniques, to develop decision rules for classifying apple cultivars technologically into bitter and nonbitter categories. A preliminary study of the data structure was performed by cluster analysis and principal component analysis in each apple material. Bitter apple varieties presented higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Different classification systems for the two categories on the basis of the chemical data were obtained applying several supervised pattern recognition procedures, such as linear discriminant analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed forward artificial neural networks. Excellent performance in terms of recognition and prediction abilities for both categories (100% of hits) was achieved in every case (pulp, peel, or juice). Polyphenolic profiles of apple pulp, peel, or juice provide enough information to develop classification criteria for establishing the technological group of apple cultivars (bitter or nonbitter).
Records of cattle slaughtered at two Chilean slaughterhouses (SLH1 and SLH2) were used to determi... more Records of cattle slaughtered at two Chilean slaughterhouses (SLH1 and SLH2) were used to determine prevalence and risk factors for carcasses with bruises. Bruise prevalence amounted to 12.3% but differed between slaughterhouses (20.8% for SLH1 and 8.6% for SLH2 respectively). Bruise severity grade 1 (mild) was most frequently recorded. The type of the animal, source of animal, the level of fat cover and lairage time were associated with the presence of bruises. Older categories of animals and animals that pass through a market before being moved to the slaughterhouse are more prone to show bruises. The results also indicate that under the reported Chilean circumstances animals that have longer lairage times (over 12 h) have a significantly reduced risk for bruises, except for oxen. Presence of bruises is also significantly associated with increased carcass pH values.
Degradation processes of amitraz in aqueous media have been studied by spectrophotometry, HPLC an... more Degradation processes of amitraz in aqueous media have been studied by spectrophotometry, HPLC and GC-MS. Amitraz undergoes hydrolysis reactions at any pH, but towards the acidic pH range hydrolysis proceeds at a faster rate. Depending on the pH value, different products of the hydrolysis have been identified. The main degradation products are 2,4-dimethylaniline at very acidic pH values (pH&lt;3), N-(2,4-dimethylphenyl)-N&#39;-methylformamidine and 2,4-dimethylphenylformamide at less acidic media (pH 3-6) and 2,4-dimethylphenylformamide at basic pH. The mechanisms of the different hydrolysis processes have been elucidated.
A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC proce... more A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure is reported for the assay of papaverine, diltiazem, desipramine and nicardipine in urine. Disposable extraction cartridges (DECs) filled with C18, C8, C2, CH and PH silica-bonded phases were used. The effect on recovery of sample pH, composition of washing and elution solvents and nature of SPE cartridge were evaluated. The selectivity of SPE was examined using spiked urine samples and the PH cartridge gave rise to the cleanest extracts. Phenyl cartridges were conditioned with methanol and acetic acid-sodium acetate buffer. Urine sample was buffered and then applied to the DEC. The washing step was with acetone-water and subsequently with methanol-acetate buffer. The analytes were eluted with methanol-acetate buffer. The extract was evaporated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with UV detection at 212 nm. Recoveries of the tested compounds from spiked urine samples using the PH cartridge were in all cases>80%. The within-day and between-day repeatabilities were<5% and 9%, respectively.
A review with 178 references on the basic principles and recent developments in the solid phase e... more A review with 178 references on the basic principles and recent developments in the solid phase extraction is presented. New solid phases, chromatographic modes, experimental configurations and off-line and on-line automated devices are discussed.
Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiol... more Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiolysis, in order to characterise and differentiate these beverages and then develop a classification system capable of confirming the authenticities of both kinds of cider. A data set consisting of 165 cider samples and 27 measured features was evaluated using multivariate chemometric techniques, such as cluster analysis and principal component analysis, in order to perform a preliminary study of data structure. Supervised pattern recognition techniques such as linear discriminant analysis (LDA), K-nearest neighbours (KNN), soft independent modelling of class analogy (SIMCA), and multilayer feed-forward artificial neural networks (MLF-ANN) attained classification rules for the two categories using the chemical data, which produced satisfactory results. Authentication systems obtained by combining two of these techniques were proposed. We found that SIMCA and LDA or KNN models achieved 100% hit-rates, since LDA and KNN permit the detection of every Basque cider and SIMCA provides a model for Basque cider that excludes all French ciders. Polyphenolic profiles of the ciders provided enough information to be able to develop classification rules for identifying ciders according to their geographical origin (Basque or French regions). Chemical and organoleptic differences between these two types of cider are probably due to the original and distinctive cidermaking technologies used for their elaboration. Using polyphenic profiles, about 80% of French ciders could be distinguished according to their region of origin (Brittany or Normandy). Although their polyphenolic profiles did not provide enough information to achieve an authentication system for Breton and Norman ciders.
A method is reported for the first time for the determination in beeswax of several acaricides us... more A method is reported for the first time for the determination in beeswax of several acaricides used for the control of the bee parasite Varroa destructor. The method was optimized and validated for amitraz residues in wax and was applied to the determination of other acaricides: bromopropylate (BP), chlordimeform, cymiazole and chlorfenvinphos. It consists of a methanol extraction step, cleanup by solid-phase extraction (SPE) with octadecylsilica and determination by capillary gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) detection. The limits of detection for the different substances were between 0.02 and 0.2 mg/kg, and the recoveries, between 40 and 95%.
Polyphenols in the peel and pulp of 15 Basque cider apple varieties were determined by accelerate... more Polyphenols in the peel and pulp of 15 Basque cider apple varieties were determined by accelerated solvent extraction followed by reversed phase high-performance liquid chromatography with diode array detection. It was observed that the polyphenolic composition in apple peel depended on varieties, whereas the main classes of phenolic compounds in apple pulp were flavan-3-ols and hydroxycinnamic acids in all cases, representing both together between 86 and 95% of total polyphenols assayed.
A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chroma... more A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure is reported for the assay of a wide polarity range acaricide residues in honey. After selection of suitable chromatographic and detection conditions, most steps of the SPE procedure that may affect to the recovery were investigated. Honey sample was buffered at pH 6 and then applied to the preconditioned C18 sorbent. A washing step was performed with 1 ml of a mixture of tetrahydrofuran (THF)-phosphate buffer (10:90, v/v) and finally, the analytes were eluted with 1 ml of THF. The extract was evaporated to dryness, reconstituted in mobile phase and chromatographed on a reversed-phase C18 column with diode array detection. The recoveries of the more polar acaricides were higher than 80% and 60-70% for the more apolar ones. Limits of detection obtained ranged from 1 to 200 ng/g.
Total polyphenol contents, estimated by Folin-Ciocalteu method, and CIELab chromatic parameters w... more Total polyphenol contents, estimated by Folin-Ciocalteu method, and CIELab chromatic parameters were determined in Basque and French ciders with the aim of developing a classification system to confirm the authenticity of ciders. A preliminary study of data structure was performed by a multivariate data analysis using chemometric techniques such as cluster analysis and principal component analysis. Supervised pattern recognition methods, such as linear discriminant analysis, K-nearest neighbours (KNN), soft independent modelling of class analogy and multilayer feed-forward artificial neural networks (MLF-ANN), provided classification rules for the two categories based on the experimental data. KNN results for Basque ciders afforded an excellent performance in terms of recognition and prediction abilities (99%), providing a useful tool to detect genuine Basque ciders. Despite KNN and MLF-ANN giving the best results for French ciders, with a success rate of prediction ability around 91%, this would not be acceptable for authentication purposes.
Apple polyphenols were characterised by means of hyphenated techniques such as HPLC coupled to UV... more Apple polyphenols were characterised by means of hyphenated techniques such as HPLC coupled to UV photodiode array detection (LC-DAD) and to mass spectrometry (LC-MS). LC-MS using atmospheric pressure ionisation (APCI) in the positive ion mode provided the molecular weight, the number of hydroxyl groups, the number of sugars and an idea about the substitution pattern of the polyphenols. LC-DAD with postcolumn addition of UV shift reagents afforded precise structural information about the position of the free hydroxyl groups in the polyphenolic nucleus. Five isorhamnetin glycosides, two hydroxyphloretin glycosides and quercetin were reported in apple peel for the first time. Postcolumn addition of UV shift reagents in LC-DAD analysis confirmed the presence of isorhamnetin glycosides and not the isomeric glycosides of rhamnetin. Moreover, isorhamnetin-3-O-rhamnoglucoside was identified unambiguously by comparison with a standard. These results are relevant not only from a chemotaxonomic point of view, but also in the control of authenticity of fruit derived products in order to detect fraudulent admixtures.
A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-perfor... more A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection is reported for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils. The effects of experimental variables, such as washing and elution solvents, sample solvent and drying time have been studied using C cartridges. Recoveries and selectivity using other sorbent materials (C , C , CH, PH and 18 8 2 NH ) were also examined, with C being the best one. The recoveries ranged between 50 and 103% depending on the 2 1 8 molecular mass of the PAH. The limits of quantitation were lower than 1 ng / g for most PAHs and good precision was achieved. The method was validated using certified reference materials.
A solvent extraction procedure of freeze-dried aliquots followed by the analysis of phenolic comp... more A solvent extraction procedure of freeze-dried aliquots followed by the analysis of phenolic compounds by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detection (DAD) has been developed for the analysis of polyphenolic compounds in fruit juices. This methodology is focussed on the characterization of fruit juices, mainly for quality control purposes. The effects of experimental variables, such as solvent composition and volume and time and temperature on extraction, have been studied. A unique gradient program for the separation of several phenolic classes (hydroquinones, hydroxybenzoic acids, flavan-3-oles, hydroxycinnamic acids, coumarins, flavanones, flavones, dihydrochalcones and flavonols) has been optimized, using standards of 55 commercially available phenolic compounds present in fruits, as well as representative real extracts from fruit juices. All phenolic compounds showed a high repeatability within-day (n = 5) and between days (n = 3) in peak area (RSD < 8%) and excellent stability of their retention times. High precision was also observed in calibration slopes (RSD < 8%). Detection limits ranged between 0.005 and 0.03 g/mL for the different detected polyphenols. Complete recoveries (98-100%) were obtained for the majority of the phenolic structures of all representative phenolic families present in fruits. The method was successfully employed to measure diverse phenolic families in juices from 18 different fruits and consequently could be used for evaluate the quality of fruit juices.
The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, a... more The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography with diode array detection analysis of crude extracts and after thiolysis. Total polyphenols are distributed in a wide concentration range depending on the cultivar. Procyanidins are the class of polyphenols that present major concentrations in apple. Their average degrees of polymerization range from 4 to 8 depending on the cultivar. Apple cultivars were technologically classified into bitter and nonbitter categories using different classification systems obtained by applying several pattern recognition techniques, such as principal component analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed-forward-artificial neural networks, to apple pulp, peel, or juice data (individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins). Bitter apple cultivars present higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Detailed knowledge of the polyphenolic profile of each apple cultivar affords information about their susceptibility to oxidation, their sensory properties (bitterness, astringency), and their possible influence on the characteristics and quality of the final product (juice, cider) when apples are processed.
... The dried tissues were crushed in closed vials to avoid hydration, using stainless-steel ball... more ... The dried tissues were crushed in closed vials to avoid hydration, using stainless-steel balls ( 1 cm) and an ... acid (30:69:1, v/v/v) with ascorbic acid (2 g/l) in an ultrasonic bath during ... which was performed by dividing the complete data set into a training set and an evaluation set. ...
A study on the possible degradation of amitraz, bromopropylate, coumaphos, chlordimeform, cymiazo... more A study on the possible degradation of amitraz, bromopropylate, coumaphos, chlordimeform, cymiazole, flumethrin, and tau-fluvalinate during the storage of honey was carried out by HPLC. Except amitraz, the other acaricides are stable in this medium for at least 9 months. Degradation studies of amitraz in honey and beeswax were carried out; the degradation products detected in both matrices were 2,4-dimethylphenylformamide (DMF) and N-(2,4-dimethylphenyl)-N′-methylformamidine (DPMF). The reaction rate constants and the half-lives of the amitraz degradation in honey and wax were calculated. Amitraz was nearly completely degraded within 1 day in beeswax and within 10 days in honey. When amitraz-spiked combs are recycled into new beeswax, DMF was found to be the principal degradation product left in pure wax.
Journal of Chromatography B: Biomedical Sciences and Applications, 1993
A reversed-phase high-performance liquid chromatographic method for oxazepam in human urine sampl... more A reversed-phase high-performance liquid chromatographic method for oxazepam in human urine samples has been developed. The sample preparation consists of an enzymatic hydrolysis with beta-glucuronidase, followed by a solid-phase extraction process using Bond-Elut C2 cartridges. The mobile phase used was a methanol-water (60:40, v/v) mixture at a flow-rate of 0.50 ml/min. The column was a 3.5 cm x 4.6 mm I.D. C18 reversed-phase column. The detection system was based on a fluorescence post-column derivatization of oxazepam in mixtures of methanol and acetic acid. A linear range from 0.01 to 1 micrograms/ml of urine and a limit of detection of 4 ng/ml of urine were attained. Within-day recoveries and reproducibilities from urine samples spiked with 0.2 and 0.02 microgram/ml oxazepam were 97.9 and 95.0 and 2.1 and 9.4%, respectively.
The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, a... more The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography--diode array detection analysis of crude extracts and after thiolysis. Data sets, consisting of individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins, were evaluated by multivariate chemometric techniques, to develop decision rules for classifying apple cultivars technologically into bitter and nonbitter categories. A preliminary study of the data structure was performed by cluster analysis and principal component analysis in each apple material. Bitter apple varieties presented higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Different classification systems for the two categories on the basis of the chemical data were obtained applying several supervised pattern recognition procedures, such as linear discriminant analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed forward artificial neural networks. Excellent performance in terms of recognition and prediction abilities for both categories (100% of hits) was achieved in every case (pulp, peel, or juice). Polyphenolic profiles of apple pulp, peel, or juice provide enough information to develop classification criteria for establishing the technological group of apple cultivars (bitter or nonbitter).
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