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Papers by Thu Thao Nguyen
The Open Analytical Chemistry Journal, 2008
The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatograph... more The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatography coupled to mass spectrometry involves time-consuming procedures such as derivatisation, degradation, solid-phase extraction, liquidliquid extraction, thin layer chromatography and sometimes, combination of all these procedures prior to the injection of the sample in the chromatography system. The performance of a method that allows the direct injection of redissolved cell culture media into a single-column liquid chromatography instrument coupled to mass spectrometry is evaluated. The external standard calibration curves were linear between 1-50 ng/ml for Williams' medium E and L-15 medium. The limit of detection and quantification were 0.5 and 1 ng/ml in both media respectively. The recovery values were 98.6% for Williams' medium E and 100.3% for L-15 medium. The internal standard method was not used for quantitative purposes due to the variability of the response factor. The proposed method has potential for broad implementation in monitoring biomarkers in cell cultures.
Talanta, 2010
Though liquid chromatography electrospray tandem mass spectrometry (LC–ESI-MS2) has been widely u... more Though liquid chromatography electrospray tandem mass spectrometry (LC–ESI-MS2) has been widely used in the structural elucidation of triacylglycerols (TAG) in vegetable oils, its potentiality for the identification of TAG molecules in omega-3 rich oils remains unexplored till date. Hence, this article investigates the applicability of LC–ESI-MS2 for the structural characterization of naturally occurring TAG in cod liver oil without the TAG fractionation during the sample preparation. A computational algorithm was developed to automatically interpret the mass spectra and elucidate the TAG structures respectively. The results were compared against the lipase benchmark method. A principal component analysis study revealed that it is possible to discriminate genuine from adulterated cod liver oil.
Journal of The American Society for Mass Spectrometry, 2005
The article presents a comprehensive account of the application of chemometric approaches to dete... more The article presents a comprehensive account of the application of chemometric approaches to determine the factors that influence the tri-α-linolenoylglycerol (TALG) ammoniated adduct signal m/z 890.6 in an ion-trap mass spectrometer coupled to a liquid chromatograph and the estimation of different sources of errors involved in TALG calibration experiments. It was found that by using experimental design, the influence of the nebulizer pressure on the analytical signal is less pronounced than the influence of the drying gas flow and the chromatographic flow rate. The results revealed that without using tandem mass or atmospheric pressure chemical ionization, it is possible to fragment the TALG backbone and obtain the free α-linolenic acid by varying the drying gas flow and using an electrospray interface. The error decomposition approach revealed that the preparation error was 26 times higher than the instrumental error.
The Open Analytical Chemistry Journal, 2008
The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatograph... more The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatography coupled to mass spectrometry involves time-consuming procedures such as derivatisation, degradation, solid-phase extraction, liquidliquid extraction, thin layer chromatography and sometimes, combination of all these procedures prior to the injection of the sample in the chromatography system. The performance of a method that allows the direct injection of redissolved cell culture media into a single-column liquid chromatography instrument coupled to mass spectrometry is evaluated. The external standard calibration curves were linear between 1-50 ng/ml for Williams' medium E and L-15 medium. The limit of detection and quantification were 0.5 and 1 ng/ml in both media respectively. The recovery values were 98.6% for Williams' medium E and 100.3% for L-15 medium. The internal standard method was not used for quantitative purposes due to the variability of the response factor. The proposed method has potential for broad implementation in monitoring biomarkers in cell cultures.
Journal of Chromatography A, 2008
A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatog... more A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatography is proposed as an alternative to the conventional method and the variables of the protocol examined to optimize the processing conditions. The modified method involves direct methylation of fatty acids in homogenized samples with boron trihalide (BF3 or BCl3 in methanol) followed by extraction with hexane. The addition of hexane to the reaction mixture after the methylation process can enhance the efficiency of fatty acid methylation and is critical for those samples that contain high levels of triglycerides. A mechanism underlying this effect is proposed.
Lipids, 2010
Exploring the capabilities of instrumental techniques for discriminating n-3 rich oils derived fr... more Exploring the capabilities of instrumental techniques for discriminating n-3 rich oils derived from animals is a very important though much neglected area that was emphasized more than 100 years ago. In this study the potential of gas chromatography (GC) for discriminating full fatty acid methyl ester (FAME) profiles from fish (cod liver and salmon) and marine mammal (seal and whale) oils is evaluated by means of principal component analysis (PCA). The FAME profiles from plant oils such as rapeseed, linseed and soy oils and seven different brands of n-3 supplements are also used in the discrimination process. The results from the PCA plots can reliably distinguish between plant, n-3 supplements, fish and marine mammal oils. By removing the contribution of the n-3 supplements and plant oils it is possible to discriminate between types of fish and marine animal oils. GC offers a rapid, simple and convenient means of discriminating oils from different species, brands and grades.
Journal of the American Society for Mass Spectrometry, 2005
The article presents a comprehensive account of the application of chemometric approaches to dete... more The article presents a comprehensive account of the application of chemometric approaches to determine the factors that influence the tri-␣-linolenoylglycerol (TALG) ammoniated adduct signal m/z 890.6 in an ion-trap mass spectrometer coupled to a liquid chromatograph and the estimation of different sources of errors involved in TALG calibration experiments. It was found that by using experimental design, the influence of the nebulizer pressure on the analytical signal is less pronounced than the influence of the drying gas flow and the chromatographic flow rate. The results revealed that without using tandem mass or atmospheric pressure chemical ionization, it is possible to fragment the TALG backbone and obtain the free ␣-linolenic acid by varying the drying gas flow and using an electrospray interface. The error decomposition approach revealed that the preparation error was 26 times higher than the instrumental error. (J Am Soc Mass Spectrom 2005, 16, 388 -396) A s an essential polyunsaturated fatty acid, ␣-linoleic acid (ALA, 18:3n-3) is not synthesized de novo in animals, but must be provided in their diets in the form of triacylglycerol [1]. The development of analytical methods in the analysis and quantification of ALA and more general triacylglycerols (TAG) is of considerable importance [2, 3] in view of their involvement in many vital biochemical processes and their association with the alleviation of a wide variety of diseases . Quantification of TAG using coupled techniques such as LCMS depends mainly on two aspects, the sample preparation technique and the instrumental condition settings. Well-established protocols and books [6 -8] have been devoted to the former and nowadays many research laboratories around the world invest time and resources to investigate new, rapid, and simpler techniques. Works regarding the latter aspect are not widespread in the literature, perhaps because variation of the instrumental conditions can cause drastic alterations to the results obtained with a tested and optimized method . Continuity of results within long periods of time (years) is of paramount importance in clinical studies [10], impairing in some degree the interest in the exploration of new or existing methodologies aiming at optimizing the set-ting of the LCMS instrumental conditions used in the quantitative analysis of TAG. Superb LCMS instruments equipped with automatic optimization devices could be another reason for the limited number of publications on this field. It has been reported that the sole chromatographic system is influenced by more than 50 factors , hence the complexity of chromatography coupled to mass spectrometry overwhelms even the most sophisticated software intended for automatic optimization and method development. The classic one-at-the-time methodology for optimization has been widely used in TAG quantification studies. One of the drawbacks of this method is that it is a tedious procedure and the true optimum can be missed if there are important interactions between the factors. The optimization of a LCMS method is prone to difficulties resulting from the inherent high number of instrumental factors involved and their interactions. The determination of the local response surface and exploitation of the local factor dependence is essential. The discovery and application of methods to that effect are extremely important. This study was undertaken, first to estimate the optimal combination of liquid chromatography-ion-trap-mass spectrometry (LCITMS) experimental variables, specifically nebulizer gas pressure, drying gas flow, and chromatographic flow rate involved in the quantitative determination of tri-␣-linolenoylglycerol (TALG) by using the response surface methodology, in particular a Doehlert matrix ; second, to study under optimal LCITMS
Journal of Chromatography A, 2008
A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatog... more A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatography is proposed as an alternative to the conventional method and the variables of the protocol examined to optimize the processing conditions. The modified method involves direct methylation of fatty acids in homogenized samples with boron trihalide (BF 3 or BCl 3 in methanol) followed by extraction with hexane. The addition of hexane to the reaction mixture after the methylation process can enhance the efficiency of fatty acid methylation and is critical for those samples that contain high levels of triglycerides. A mechanism underlying this effect is proposed.
Analytica Chimica Acta, 2012
Basel 3 bắt dầu dược triển khai ap dụng
Genetic Analysis of ORF5 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Isolated in Vietnam
Microbiology and Immunology, 2013
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically impor... more Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important swine pathogens because it is highly infectious and causes economic losses due to decreased pig productivity. In this study, the 603 bp complete major envelope protein encoding gene (ORF5) of 32 field PRRSV isolates from Vietnam collected during 2008-2012 were sequenced and analyzed. Multiple nucleotide (nt) and deduced amino acid (aa) alignments of ORF5 were performed on the 32 isolates: the representative strains (European and North American genotypes), Chinese strains available in GenBank and vaccine strains licensed for use in Vietnam. The results showed 94.8-100.0% nt identity and 94.0-100% aa similarity among the 32 isolates. These isolates shared similarities with the prototype of the North American PRRSV strain (VR-2332; nt 87.8-89.3%, aa 87.5-90.0%), and Lelystat virus, the prototype of the European PRRSV strain (LV; nt 61.1-61.9%, aa 55.1-57.0%). There was greater similarity with QN07 (nt 96.5-98.5%, aa 96.0-99.0%) from the 2007 PRRS outbreak in QuangNam Province, CH-1a (nt 93.2-95.1%, 91.5-93.5%) isolated in China in 1995 and JXA1 (nt 96.5-98.6%, aa 95.0-98.0%), the highly pathogenic strain from China isolated in 2006. The Vietnamese isolates were more similar to JXA1-R (nt 96.5-98.6%, aa 95.0-98.0%), the strain used in Chinese vaccines, than to Ingelvac MLV/BSL-PS (nt 87.2-89.0%, aa 86.0-89.0%). Phylogenetic analysis showed that the 32 isolates were of the North American genotype and classified into sub-lineage 8.7. This sub-lineage contains highly pathogenic Chinese PRRSV strains. This study documents genetic variation in circulating PRRSV strains and could assist more effective use of PRRS vaccines in Vietnam.
Tropical Medicine & International Health, 2015
objectives To determine the extent of physicians' adherence to prescribing guidelines for acute c... more objectives To determine the extent of physicians' adherence to prescribing guidelines for acute coronary syndrome in Vietnamese hospitals.
Fertigungswirtschaft
Betriebswirtschaftliche Anwendungen mit SAP R/3®, 1999
Prevalence of Salmonella and Escherichia coli O157 from Acute Diarrheic Children in the Mekong Delta, Vietnam
Journal of Veterinary Epidemiology, 2010
The Open Analytical Chemistry Journal, 2008
The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatograph... more The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatography coupled to mass spectrometry involves time-consuming procedures such as derivatisation, degradation, solid-phase extraction, liquidliquid extraction, thin layer chromatography and sometimes, combination of all these procedures prior to the injection of the sample in the chromatography system. The performance of a method that allows the direct injection of redissolved cell culture media into a single-column liquid chromatography instrument coupled to mass spectrometry is evaluated. The external standard calibration curves were linear between 1-50 ng/ml for Williams' medium E and L-15 medium. The limit of detection and quantification were 0.5 and 1 ng/ml in both media respectively. The recovery values were 98.6% for Williams' medium E and 100.3% for L-15 medium. The internal standard method was not used for quantitative purposes due to the variability of the response factor. The proposed method has potential for broad implementation in monitoring biomarkers in cell cultures.
Talanta, 2010
Though liquid chromatography electrospray tandem mass spectrometry (LC–ESI-MS2) has been widely u... more Though liquid chromatography electrospray tandem mass spectrometry (LC–ESI-MS2) has been widely used in the structural elucidation of triacylglycerols (TAG) in vegetable oils, its potentiality for the identification of TAG molecules in omega-3 rich oils remains unexplored till date. Hence, this article investigates the applicability of LC–ESI-MS2 for the structural characterization of naturally occurring TAG in cod liver oil without the TAG fractionation during the sample preparation. A computational algorithm was developed to automatically interpret the mass spectra and elucidate the TAG structures respectively. The results were compared against the lipase benchmark method. A principal component analysis study revealed that it is possible to discriminate genuine from adulterated cod liver oil.
Journal of The American Society for Mass Spectrometry, 2005
The article presents a comprehensive account of the application of chemometric approaches to dete... more The article presents a comprehensive account of the application of chemometric approaches to determine the factors that influence the tri-α-linolenoylglycerol (TALG) ammoniated adduct signal m/z 890.6 in an ion-trap mass spectrometer coupled to a liquid chromatograph and the estimation of different sources of errors involved in TALG calibration experiments. It was found that by using experimental design, the influence of the nebulizer pressure on the analytical signal is less pronounced than the influence of the drying gas flow and the chromatographic flow rate. The results revealed that without using tandem mass or atmospheric pressure chemical ionization, it is possible to fragment the TALG backbone and obtain the free α-linolenic acid by varying the drying gas flow and using an electrospray interface. The error decomposition approach revealed that the preparation error was 26 times higher than the instrumental error.
The Open Analytical Chemistry Journal, 2008
The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatograph... more The traditional approach to assessing eicosanoids in cell cultures by liquid or gas chromatography coupled to mass spectrometry involves time-consuming procedures such as derivatisation, degradation, solid-phase extraction, liquidliquid extraction, thin layer chromatography and sometimes, combination of all these procedures prior to the injection of the sample in the chromatography system. The performance of a method that allows the direct injection of redissolved cell culture media into a single-column liquid chromatography instrument coupled to mass spectrometry is evaluated. The external standard calibration curves were linear between 1-50 ng/ml for Williams' medium E and L-15 medium. The limit of detection and quantification were 0.5 and 1 ng/ml in both media respectively. The recovery values were 98.6% for Williams' medium E and 100.3% for L-15 medium. The internal standard method was not used for quantitative purposes due to the variability of the response factor. The proposed method has potential for broad implementation in monitoring biomarkers in cell cultures.
Journal of Chromatography A, 2008
A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatog... more A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatography is proposed as an alternative to the conventional method and the variables of the protocol examined to optimize the processing conditions. The modified method involves direct methylation of fatty acids in homogenized samples with boron trihalide (BF3 or BCl3 in methanol) followed by extraction with hexane. The addition of hexane to the reaction mixture after the methylation process can enhance the efficiency of fatty acid methylation and is critical for those samples that contain high levels of triglycerides. A mechanism underlying this effect is proposed.
Lipids, 2010
Exploring the capabilities of instrumental techniques for discriminating n-3 rich oils derived fr... more Exploring the capabilities of instrumental techniques for discriminating n-3 rich oils derived from animals is a very important though much neglected area that was emphasized more than 100 years ago. In this study the potential of gas chromatography (GC) for discriminating full fatty acid methyl ester (FAME) profiles from fish (cod liver and salmon) and marine mammal (seal and whale) oils is evaluated by means of principal component analysis (PCA). The FAME profiles from plant oils such as rapeseed, linseed and soy oils and seven different brands of n-3 supplements are also used in the discrimination process. The results from the PCA plots can reliably distinguish between plant, n-3 supplements, fish and marine mammal oils. By removing the contribution of the n-3 supplements and plant oils it is possible to discriminate between types of fish and marine animal oils. GC offers a rapid, simple and convenient means of discriminating oils from different species, brands and grades.
Journal of the American Society for Mass Spectrometry, 2005
The article presents a comprehensive account of the application of chemometric approaches to dete... more The article presents a comprehensive account of the application of chemometric approaches to determine the factors that influence the tri-␣-linolenoylglycerol (TALG) ammoniated adduct signal m/z 890.6 in an ion-trap mass spectrometer coupled to a liquid chromatograph and the estimation of different sources of errors involved in TALG calibration experiments. It was found that by using experimental design, the influence of the nebulizer pressure on the analytical signal is less pronounced than the influence of the drying gas flow and the chromatographic flow rate. The results revealed that without using tandem mass or atmospheric pressure chemical ionization, it is possible to fragment the TALG backbone and obtain the free ␣-linolenic acid by varying the drying gas flow and using an electrospray interface. The error decomposition approach revealed that the preparation error was 26 times higher than the instrumental error. (J Am Soc Mass Spectrom 2005, 16, 388 -396) A s an essential polyunsaturated fatty acid, ␣-linoleic acid (ALA, 18:3n-3) is not synthesized de novo in animals, but must be provided in their diets in the form of triacylglycerol [1]. The development of analytical methods in the analysis and quantification of ALA and more general triacylglycerols (TAG) is of considerable importance [2, 3] in view of their involvement in many vital biochemical processes and their association with the alleviation of a wide variety of diseases . Quantification of TAG using coupled techniques such as LCMS depends mainly on two aspects, the sample preparation technique and the instrumental condition settings. Well-established protocols and books [6 -8] have been devoted to the former and nowadays many research laboratories around the world invest time and resources to investigate new, rapid, and simpler techniques. Works regarding the latter aspect are not widespread in the literature, perhaps because variation of the instrumental conditions can cause drastic alterations to the results obtained with a tested and optimized method . Continuity of results within long periods of time (years) is of paramount importance in clinical studies [10], impairing in some degree the interest in the exploration of new or existing methodologies aiming at optimizing the set-ting of the LCMS instrumental conditions used in the quantitative analysis of TAG. Superb LCMS instruments equipped with automatic optimization devices could be another reason for the limited number of publications on this field. It has been reported that the sole chromatographic system is influenced by more than 50 factors , hence the complexity of chromatography coupled to mass spectrometry overwhelms even the most sophisticated software intended for automatic optimization and method development. The classic one-at-the-time methodology for optimization has been widely used in TAG quantification studies. One of the drawbacks of this method is that it is a tedious procedure and the true optimum can be missed if there are important interactions between the factors. The optimization of a LCMS method is prone to difficulties resulting from the inherent high number of instrumental factors involved and their interactions. The determination of the local response surface and exploitation of the local factor dependence is essential. The discovery and application of methods to that effect are extremely important. This study was undertaken, first to estimate the optimal combination of liquid chromatography-ion-trap-mass spectrometry (LCITMS) experimental variables, specifically nebulizer gas pressure, drying gas flow, and chromatographic flow rate involved in the quantitative determination of tri-␣-linolenoylglycerol (TALG) by using the response surface methodology, in particular a Doehlert matrix ; second, to study under optimal LCITMS
Journal of Chromatography A, 2008
A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatog... more A simplified method for quantitative analysis of fatty acids in various matrices by gas chromatography is proposed as an alternative to the conventional method and the variables of the protocol examined to optimize the processing conditions. The modified method involves direct methylation of fatty acids in homogenized samples with boron trihalide (BF 3 or BCl 3 in methanol) followed by extraction with hexane. The addition of hexane to the reaction mixture after the methylation process can enhance the efficiency of fatty acid methylation and is critical for those samples that contain high levels of triglycerides. A mechanism underlying this effect is proposed.
Analytica Chimica Acta, 2012
Basel 3 bắt dầu dược triển khai ap dụng
Genetic Analysis of ORF5 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Isolated in Vietnam
Microbiology and Immunology, 2013
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically impor... more Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important swine pathogens because it is highly infectious and causes economic losses due to decreased pig productivity. In this study, the 603 bp complete major envelope protein encoding gene (ORF5) of 32 field PRRSV isolates from Vietnam collected during 2008-2012 were sequenced and analyzed. Multiple nucleotide (nt) and deduced amino acid (aa) alignments of ORF5 were performed on the 32 isolates: the representative strains (European and North American genotypes), Chinese strains available in GenBank and vaccine strains licensed for use in Vietnam. The results showed 94.8-100.0% nt identity and 94.0-100% aa similarity among the 32 isolates. These isolates shared similarities with the prototype of the North American PRRSV strain (VR-2332; nt 87.8-89.3%, aa 87.5-90.0%), and Lelystat virus, the prototype of the European PRRSV strain (LV; nt 61.1-61.9%, aa 55.1-57.0%). There was greater similarity with QN07 (nt 96.5-98.5%, aa 96.0-99.0%) from the 2007 PRRS outbreak in QuangNam Province, CH-1a (nt 93.2-95.1%, 91.5-93.5%) isolated in China in 1995 and JXA1 (nt 96.5-98.6%, aa 95.0-98.0%), the highly pathogenic strain from China isolated in 2006. The Vietnamese isolates were more similar to JXA1-R (nt 96.5-98.6%, aa 95.0-98.0%), the strain used in Chinese vaccines, than to Ingelvac MLV/BSL-PS (nt 87.2-89.0%, aa 86.0-89.0%). Phylogenetic analysis showed that the 32 isolates were of the North American genotype and classified into sub-lineage 8.7. This sub-lineage contains highly pathogenic Chinese PRRSV strains. This study documents genetic variation in circulating PRRSV strains and could assist more effective use of PRRS vaccines in Vietnam.
Tropical Medicine & International Health, 2015
objectives To determine the extent of physicians' adherence to prescribing guidelines for acute c... more objectives To determine the extent of physicians' adherence to prescribing guidelines for acute coronary syndrome in Vietnamese hospitals.
Fertigungswirtschaft
Betriebswirtschaftliche Anwendungen mit SAP R/3®, 1999
Prevalence of Salmonella and Escherichia coli O157 from Acute Diarrheic Children in the Mekong Delta, Vietnam
Journal of Veterinary Epidemiology, 2010