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Selected papers from the latest issue:
Development of a chromatographic low pressure flow injection system: application to the analysis of methylxanthines in coffee
11 December 2011, 02:34:10
Publication year: 2011
Source: Analytica Chimica Acta, Available online 9 December 2011
João Rodrigo Santos, António O.S.S. Rangel
In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection.The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10 M range for theobromine and theophylline, and 10 M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h.The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented
Source: Analytica Chimica Acta, Available online 9 December 2011
João Rodrigo Santos, António O.S.S. Rangel
In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection.The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10 M range for theobromine and theophylline, and 10 M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h.The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented
Highlights
► Coupling of monolithic columns into traditional low-pressure FIA systems ► Potential selectivity and increased versatility over low pressure FIA system ► Flow system presenting lower cost of analysis if compared to HPLCDevelopment of a chromatographic low pressure flow injection system: application to the analysis of methylxanthines in coffee
10 December 2011, 01:25:12
Publication year: 2011
Source: Analytica Chimica Acta, Available online 9 December 2011
João Rodrigo Santos, António O.S.S. Rangel
In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection.The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10 M range for theobromine and theophylline, and 10 M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h.The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented
Source: Analytica Chimica Acta, Available online 9 December 2011
João Rodrigo Santos, António O.S.S. Rangel
In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection.The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10 M range for theobromine and theophylline, and 10 M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h.The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented
Highlights
► Coupling of monolithic columns into traditional low-pressure FIA systems ► Potential selectivity and increased versatility over low pressure FIA system ► Flow system presenting lower cost of analysis if compared to HPLCComparison of ultrasound–assisted emulsification and dispersive liquid–liquid microextraction methods for the speciation of inorganic selenium in environmental water samples using low density extraction solvents
09 December 2011, 00:24:42
Publication year: 2011
Source: Analytica Chimica Acta, Available online 8 December 2011
Nahid Mashkouri Najafi, Hamed Tavakoli, Yaser Abdollahzadeh, Reza Alizadeh
Herein, ultrasound–assisted emulsification microextraction (USAEME) and dispersive liquid–liquid microextraction (DLLME) methods based on applying low-density organic solvents have been critically compared for the speciation of inorganic selenium, Se(IV) (selenite) and Se(VI) (selenate) in environmental water samples by gas chromatography–flame ionization detection (GC–FID). At pH = 2 and T = 75 ˚C for 7 min, only Se(IV) was able to form the piazselenol complex with 4–nitro–o–phenylendiamine. Piazselenol was extracted using an extraction solvent and was injected into a GC–FID instrument for the determination of Se(IV). Conveniently, Se(VI) remained in the aqueous phase. Total inorganic selenium was determined after the reduction of Se(VI) to Se(IV) and prior to the above procedures. The Se(VI) concentration was calculated as the difference between the measured total inorganic selenium and Se(IV) content. The effect of various experimental parameters on the efficiencies of the two methods and their optimum values were studied with the aid of response surface methodology and experimental design. Under the optimal conditions, the limit of detections (LODs) for Se(IV) obtained by USAEME-GC-FID and DLLME-GC-FID were 0.05 and 0.11 ng mL, respectively. The relative standard deviations (RSDs, n = 6) for the measurement 10 ng mLof Se(IV) were 5.32% and 4.57% with the enrichment factors of 2491 and 1129 for USAEME-GC-FID and DLLME-GC-FID, respectively. Both methods were successfully applied to the analysis of inorganic selenium in different environmental water samples and certified reference material (NIST SRM 1643e).
Source: Analytica Chimica Acta, Available online 8 December 2011
Nahid Mashkouri Najafi, Hamed Tavakoli, Yaser Abdollahzadeh, Reza Alizadeh
Herein, ultrasound–assisted emulsification microextraction (USAEME) and dispersive liquid–liquid microextraction (DLLME) methods based on applying low-density organic solvents have been critically compared for the speciation of inorganic selenium, Se(IV) (selenite) and Se(VI) (selenate) in environmental water samples by gas chromatography–flame ionization detection (GC–FID). At pH = 2 and T = 75 ˚C for 7 min, only Se(IV) was able to form the piazselenol complex with 4–nitro–o–phenylendiamine. Piazselenol was extracted using an extraction solvent and was injected into a GC–FID instrument for the determination of Se(IV). Conveniently, Se(VI) remained in the aqueous phase. Total inorganic selenium was determined after the reduction of Se(VI) to Se(IV) and prior to the above procedures. The Se(VI) concentration was calculated as the difference between the measured total inorganic selenium and Se(IV) content. The effect of various experimental parameters on the efficiencies of the two methods and their optimum values were studied with the aid of response surface methodology and experimental design. Under the optimal conditions, the limit of detections (LODs) for Se(IV) obtained by USAEME-GC-FID and DLLME-GC-FID were 0.05 and 0.11 ng mL, respectively. The relative standard deviations (RSDs, n = 6) for the measurement 10 ng mLof Se(IV) were 5.32% and 4.57% with the enrichment factors of 2491 and 1129 for USAEME-GC-FID and DLLME-GC-FID, respectively. Both methods were successfully applied to the analysis of inorganic selenium in different environmental water samples and certified reference material (NIST SRM 1643e).
Highlights
► USAEME and DLLME have been applied for the speciation of inorganic selenium ► Low density organic solvents have been used as extraction solvent in the two methods ► Response surface methodology has been applied for optimization of the two methods ► The advantages and disadvantages of both methods have been discussedDevelopment of a dispersive liquid-liquid microextraction method for the determination of fluoroquinolones in chicken liver by high performance liquid chromatography
09 December 2011, 00:24:42
Publication year: 2011
Source: Analytica Chimica Acta, Available online 8 December 2011
D. Moema, M.M. Nindi, S. Dube
A simple and cost effective sample pre-treatment method, dispersive liquid liquid microextraction (DLLME), has been developed for the extraction of six fluoroquinolones from chicken liver samples. Clean DLLME extracts were analyzed for fluoroquinolones using liquid chromatography with diode array detection (LC-DAD). Parameters such as type and volume of disperser solvent, type and volume of extraction solvent, concentration and composition of phosphoric acid in the disperser solvent and pH were optimized. Linearity in the concentration range of 30-500 μg kgwas obtained with regression coefficients ranging from 0.9945 to 0.9974. Intra-day repeatability expressed as % RSD was between 4 to 7%. The recoveries determined in spiked blank chicken livers at three concentration levels (i.e. 50, 100 and 300 μg kg) ranged from 83-102%. LODs were between 5 to 19 μg kgwhile LOQs ranged between 23 and 62 μg kg. All of the eight chicken liver samples obtained from the local supermarkets were found to contain at least one type of fluoroquinolone with enrofloxacin being the most commonly detected. Only one sample had four fluoroquinolone antibiotics (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin). Norfloxacin which is unlicensed for use in South Africa was also detected in three of the eight chicken liver samples analyzed. The concentration levels of all FQs antibiotics in eight samples ranged from 8.8 to 35.3 μg kg, values which are lower than the South African stipulated MRL.
Source: Analytica Chimica Acta, Available online 8 December 2011
D. Moema, M.M. Nindi, S. Dube
A simple and cost effective sample pre-treatment method, dispersive liquid liquid microextraction (DLLME), has been developed for the extraction of six fluoroquinolones from chicken liver samples. Clean DLLME extracts were analyzed for fluoroquinolones using liquid chromatography with diode array detection (LC-DAD). Parameters such as type and volume of disperser solvent, type and volume of extraction solvent, concentration and composition of phosphoric acid in the disperser solvent and pH were optimized. Linearity in the concentration range of 30-500 μg kgwas obtained with regression coefficients ranging from 0.9945 to 0.9974. Intra-day repeatability expressed as % RSD was between 4 to 7%. The recoveries determined in spiked blank chicken livers at three concentration levels (i.e. 50, 100 and 300 μg kg) ranged from 83-102%. LODs were between 5 to 19 μg kgwhile LOQs ranged between 23 and 62 μg kg. All of the eight chicken liver samples obtained from the local supermarkets were found to contain at least one type of fluoroquinolone with enrofloxacin being the most commonly detected. Only one sample had four fluoroquinolone antibiotics (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin). Norfloxacin which is unlicensed for use in South Africa was also detected in three of the eight chicken liver samples analyzed. The concentration levels of all FQs antibiotics in eight samples ranged from 8.8 to 35.3 μg kg, values which are lower than the South African stipulated MRL.
Highlights
► We developed DLLME a novel technique has been for fluoroquinolones in chicken livers. ► This greener sample preparation technique has potential for veterinary drugs residue. ► DLLME is a cheap, fast, green method of sample extraction from biological matrixes.Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry
09 December 2011, 00:24:42
Publication year: 2011
Source: Analytica Chimica Acta, Available online 8 December 2011
S. García-Salgado, M.A. Quijano, M.M. Bonilla
Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9Sargassum fulvellumwere analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g. Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography–ultraviolet photo-oxidation–hydride generation atomic–fluorescence spectrometry (HPLC-(UV)-HG-AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g, whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g) and generally high arsenate (As(V)) concentrations (up to 77 μg g) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.
Source: Analytica Chimica Acta, Available online 8 December 2011
S. García-Salgado, M.A. Quijano, M.M. Bonilla
Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9Sargassum fulvellumwere analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g. Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography–ultraviolet photo-oxidation–hydride generation atomic–fluorescence spectrometry (HPLC-(UV)-HG-AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g, whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g) and generally high arsenate (As(V)) concentrations (up to 77 μg g) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.
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