Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 50
Filtrar
1.
BMJ Mil Health ; 2023 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-36702521

RESUMO

BACKGROUND: In the UK, there have been multiple waves of COVID-19, with a five-tier alert system created to describe the transmission rate and appropriate restrictions. While acute mortality decreased, there continued to be a significant morbidity, with individuals suffering from persistent, life-restricting symptoms for months to years afterwards. A remote rehabilitation tool was created at the Defence Medical Rehabilitation Centre (DMRC) Stanford Hall to assess post-COVID-19 symptoms and their impact on the UK military.This study aims to understand changes in post-COVID-19 syndrome between wave 1 and wave 2, identify interactions between alert level and symptoms and investigate any predictive nature of acute symptoms for postacute symptomology in a young, physically active population. METHODS: Cross-sectional study of 458 consecutive remote rehabilitation assessments performed at DMRC Stanford Hall between 2 April 2020 and 29 July 2021. Consultations were coded, anonymised, and statistical analysis was performed to determine associations between acute and postacute symptoms, and between symptoms, alert levels and waves. RESULTS: 435 assessments were eligible; 174 in wave 1 and 261 in wave 2. Post-COVID-19 syndrome prevalence reduced from 43% to 2% between the waves. Acutely, widespread pain was more prevalent in wave 2 (p<0.001). Postacutely, there was increased anxiety (p=0.10) in wave 1 and increased sleep disturbance (p<0.001), memory/concentration issues (p<0.001) and shortness of breath/cough (p=0.017) in wave 2. Increasing alert level was associated with increased postacute symptom prevalence (p=0.046), with sleep disturbance increasing at higher alert level (p=0.016). Acute symptoms, including fatigue, sleep disturbance and myalgia, were associated with multiple postacute symptoms. CONCLUSIONS: This study reports the overall prevalence and symptom burden in the UK military in the first two waves of COVID-19. By reporting differences in COVID-19 in different waves and alert level, this study highlights the importance of careful assessment and contextual understanding of acute and postacute illnesses for individual management plans.

2.
Dis Aquat Organ ; 152: 73-83, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36453456

RESUMO

The Critically Endangered southern corroboree frog Pseudophryne corroboree is dependent upon captive assurance colonies for its continued survival. Although the captive breeding programme for this species has largely been successful, embryonic mortality remains high (40-90% per year). This study aimed to investigate the causes of mortality in P. corroboree embryos in the captive collection at Melbourne Zoo. During the 2021 breeding season, we investigated 108 abnormal embryos to determine the impact of infections and anatomical deformities on survival and used culture and molecular methods to identify microbes. Overall, 100% of abnormal embryos had fungal infections, and of these, 41.6% also had anatomical deformities. The mortality rate in abnormal embryos was 89.8%; however, we detected no difference in survival in any of the 3 observed fungal growth patterns or between deformed and non-deformed embryos. Sanger sequencing of the ITS region identified fungal isolates belonging to the genus Ilyonectria, the first record in a vertebrate host, and another as a Plectosphaerella sp., which is the first record of infection in an embryo. Dominant bacteria identified were of the genera Herbaspirillum and Flavobacterium; however, their role in the mortality is unknown. Fungal infection and deformities have a significant impact on embryo survival in captive-bred P. corroboree. In a species which relies on captive breeding, identifying and reducing the impacts of embryonic mortality can inform conservation efforts and improve reintroduction outcomes.


Assuntos
Anuros , Flavobacterium , Animais , Estações do Ano
3.
Cell ; 180(5): 878-894.e19, 2020 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-32059783

RESUMO

Pathogenic autoantibodies arise in many autoimmune diseases, but it is not understood how the cells making them evade immune checkpoints. Here, single-cell multi-omics analysis demonstrates a shared mechanism with lymphoid malignancy in the formation of public rheumatoid factor autoantibodies responsible for mixed cryoglobulinemic vasculitis. By combining single-cell DNA and RNA sequencing with serum antibody peptide sequencing and antibody synthesis, rare circulating B lymphocytes making pathogenic autoantibodies were found to comprise clonal trees accumulating mutations. Lymphoma driver mutations in genes regulating B cell proliferation and V(D)J mutation (CARD11, TNFAIP3, CCND3, ID3, BTG2, and KLHL6) were present in rogue B cells producing the pathogenic autoantibody. Antibody V(D)J mutations conferred pathogenicity by causing the antigen-bound autoantibodies to undergo phase transition to insoluble aggregates at lower temperatures. These results reveal a pre-neoplastic stage in human lymphomagenesis and a cascade of somatic mutations leading to an iconic pathogenic autoantibody.


Assuntos
Autoanticorpos/genética , Doenças Autoimunes/genética , Linfócitos B/imunologia , Linfoma/genética , Animais , Autoanticorpos/imunologia , Doenças Autoimunes/imunologia , Doenças Autoimunes/patologia , Linfócitos B/patologia , Proteínas Adaptadoras de Sinalização CARD/genética , Proteínas de Transporte/genética , Evolução Clonal/genética , Evolução Clonal/imunologia , Ciclina D3/genética , Guanilato Ciclase/genética , Humanos , Proteínas Imediatamente Precoces/genética , Região Variável de Imunoglobulina/genética , Região Variável de Imunoglobulina/imunologia , Proteínas Inibidoras de Diferenciação/genética , Linfoma/imunologia , Linfoma/patologia , Camundongos , Mutação/genética , Mutação/imunologia , Proteínas de Neoplasias/genética , Análise de Sequência de DNA/métodos , Análise de Sequência de RNA/métodos , Análise de Célula Única/métodos , Proteína 3 Induzida por Fator de Necrose Tumoral alfa/genética , Proteínas Supressoras de Tumor/genética , Recombinação V(D)J/genética
4.
Public Health ; 128(6): 497-503, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24837784

RESUMO

OBJECTIVES: Knowledge translation (KT) is becoming common vocabulary, but as a concept it is not clearly defined. Many related terms exist; these are often used interchangeably and given multiple interpretations. While there is a growing body of literature exploring these concepts, using it to inform public health practice, strategy, research and education is challenging given the range of sources and need for local 'contextual fit'. This study explores how various public health stakeholders make sense of, and experience, KT and related concepts. STUDY DESIGN: A qualitative mapping study using a phenomenographic approach. METHODS: Thirty-four academics, students and practitioners working in public health across the north east of England participated in six focus groups and five one-to-one interviews. Discussions were audio-recorded, transcribed and analysed using a thematic framework approach. The framework drew on findings from reviews of the existing literature, whilst allowing unanticipated issues to emerge. RESULTS: Three main themes were identified from the stakeholder discussions: CONCLUSIONS: This study has enabled further development of theoretical understandings of the KT discourses at play in public health, and identified the ways in which these may be bound by discipline and context. Ironically, the findings suggest that terms such as knowledge translation, transfer and exchange are seen as themselves requiring translation, or at least debate and discussion.


Assuntos
Conhecimento , Saúde Pública , Terminologia como Assunto , Pesquisa Translacional Biomédica , Inglaterra , Docentes , Grupos Focais , Humanos , Entrevistas como Assunto , Prática de Saúde Pública , Pesquisa Qualitativa , Estudantes de Saúde Pública , Gravação em Fita
5.
Cell Death Differ ; 19(4): 671-9, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22117198

RESUMO

A wide range of molecules acting as apoptotic cell-associated ligands, phagocyte-associated receptors or soluble bridging molecules have been implicated within the complex sequential processes that result in phagocytosis and degradation of apoptotic cells. Intercellular adhesion molecule 3 (ICAM-3, also known as CD50), a human leukocyte-restricted immunoglobulin super-family (IgSF) member, has previously been implicated in apoptotic cell clearance, although its precise role in the clearance process is ill defined. The main objective of this work is to further characterise the function of ICAM-3 in the removal of apoptotic cells. Using a range of novel anti-ICAM-3 monoclonal antibodies (mAbs), including one (MA4) that blocks apoptotic cell clearance by macrophages, alongside apoptotic human leukocytes that are normal or deficient for ICAM-3, we demonstrate that ICAM-3 promotes a domain 1-2-dependent tethering interaction with phagocytes. Furthermore, we demonstrate an apoptosis-associated reduction in ICAM-3 that results from release of ICAM-3 within microparticles that potently attract macrophages to apoptotic cells. Taken together, these data suggest that apoptotic cell-derived microparticles bearing ICAM-3 promote macrophage chemoattraction to sites of leukocyte cell death and that ICAM-3 mediates subsequent cell corpse tethering to macrophages. The defined function of ICAM-3 in these processes and profound defect in chemotaxis noted to ICAM-3-deficient microparticles suggest that ICAM-3 may be an important adhesion molecule involved in chemotaxis to apoptotic human leukocytes.


Assuntos
Antígenos CD/metabolismo , Apoptose/fisiologia , Moléculas de Adesão Celular/metabolismo , Micropartículas Derivadas de Células/metabolismo , Quimiotaxia/fisiologia , Macrófagos/metabolismo , Animais , Anticorpos Monoclonais Murinos/farmacologia , Antígenos CD/genética , Moléculas de Adesão Celular/antagonistas & inibidores , Moléculas de Adesão Celular/genética , Micropartículas Derivadas de Células/genética , Quimiotaxia/efeitos dos fármacos , Células HeLa , Humanos , Células Jurkat , Macrófagos/citologia , Camundongos , Camundongos Endogâmicos BALB C
7.
Eur J Phys Rehabil Med ; 44(2): 177-93, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18418338

RESUMO

Traditionally, the treatment options for adolescent idiopathic scoliosis (AIS), the most common form of scoliosis, are exercises; in-patient rehabilitation; braces and surgery. The outcomes of treatments are usually compared with the natural history or observation (non-intervention). The aim of this paper was to provide a synopsis of all treatment options in the light of evidence based practice (EBP). A systematic review was carried out using the most encompassing databases available. Literature has been searched for the outcome parameter ''rate of progression'' and only prospective controlled studies that have considered the treatment versus the natural history have been included. The search strategy included the following terms: ''adolescent idiopathic scoliosis''; ''idiopathic scoliosis''; ''natural history''; ''observation''; ''physiotherapy''; ''physical therapy''; ''rehabilitation''; ''bracing''; ''orthotics'' and ''surgery''. Prospective short-term studies have been found to support outpatient physiotherapy. One prospective controlled study was found to support scoliosis in-patient rehabilitation (SIR). One prospective multi-centre study, a long-term prospective controlled study and a meta-analysis have been found to support bracing. No controlled study, neither short, mid nor long-term, was found to reveal any substantial evidence to support surgery as a treatment for this condition. There is some evidence supporting the conservative treatment for AIS. No substantial evidence has been found in terms of prospective controlled studies to support surgical intervention. In light of the unknown long-term effects of surgery, a randomised controlled trial (RCT) seems necessary. Due to the presence of evidence to support conservative treatments, a plan to compose a RCT for conservative treatment options seems unethical. But it is also important to conclude that the evidence for conservative treatments is weak in number and length.


Assuntos
Escoliose/reabilitação , Adolescente , Braquetes , Medicina Baseada em Evidências , Terapia por Exercício , Humanos , Procedimentos Ortopédicos , Modalidades de Fisioterapia
8.
Biochim Biophys Acta ; 1760(4): 669-77, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16413679

RESUMO

Post-translational modifications (PTMs) of proteins produced in vivo may be tissue, developmentally and/or disease specific. PTMs impact on the stability and function of proteins and offer a challenge to the commercial production of protein biotherapeutics. We have previously reported a marked deficit in galactosylation of oligosaccharides released from polyclonal IgG isolated from sera of patients with the anti-neutrophil cytoplasmic antibodies (ANCA) associated vasculitides; Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA). Whilst normal polyclonal IgG molecules are glycosylated within the IgG-Fc region, approximately 20% of molecules also bear oligosaccharides attached to the variable regions of the light or heavy chain IgG-Fab. It is of interest, therefore to compare profiles of oligosaccharides released from the IgG-Fc and IgG-Fab of normal IgG with that isolated from the sera of patients with WG or MPA. This study shows that whilst the oligosaccharides released from ANCA IgG-Fc are hypogalactosylated those released from IgG-Fab are galactosylated and sialylated. These results show that hypogalactosylation of IgG-Fc is not due to a defect in the glycosylation or processing machinery. It rather suggests a subtle change in IgG-Fc conformation that influences the addition of galactose. Remarkably, this influence is exerted on all plasma cells. Interestingly, a licensed monoclonal antibody therapeutic, produced in Sp2/0 cells, is also shown to be hypogalactosylated in its IgG-Fc but fully galactosylated in its IgG-Fab.


Assuntos
Anticorpos Anticitoplasma de Neutrófilos/sangue , Imunoglobulina G/química , Oligossacarídeos/análise , Vasculite/imunologia , Estudos de Casos e Controles , Galactose , Glicosilação , Humanos , Fragmentos Fab das Imunoglobulinas/sangue , Fragmentos Fab das Imunoglobulinas/química , Fragmentos Fc das Imunoglobulinas/sangue , Fragmentos Fc das Imunoglobulinas/química , Imunoglobulina G/sangue , Processamento de Proteína Pós-Traducional
9.
Food Addit Contam ; 21(7): 658-69, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15370839

RESUMO

The European Union Baby Food Directive (1999/39/EC), which came into force on 1 July 2002, set legal maximum residue levels at 0.01 mg kg(-1) for all pesticides in baby foods. The combination of large volume-difficult matrix introduction (LV-DMI) with gas chromatography-time of flight-mass spectrometry (GC-TOF-MS), described herein, provides the analyst with a simple but rapid alternative GC-MS technique for the multiresidue analysis of pesticides in fruit-based baby foods. Samples were extracted with ethyl acetate in the presence of Na2SO4 and NaHCO3 and the crude extracts were analysed directly using LV-DMI-GC-TOF-MS. The best overall results (98 pesticides quantified satisfactorily at a spiking level of 0.01 mg kg(-1)) were obtained by analysis of concentrated extracts (2.5 g crop ml(-1)) using a 30-m column, with a chromatographic run time of 25 min. A good signal-to-noise ratio was obtained at the lowest calibrated level (0.0125 microg ml(-1)), with excellent linearity achieved over the range 0.0125-0.25 microg ml(-1) (equivalent to 0.005-0.1 mg kg(-1)). Average recoveries for the analysis of five replicate determinations at a spiking level of 0.01 mg kg(-1) were between 79 and 114% with relative standard derivations generally less than 20%.


Assuntos
Contaminação de Alimentos/análise , Frutas/química , Alimentos Infantis , Praguicidas/análise , Calibragem , Fungicidas Industriais/análise , Hexaclorobenzeno/análise , Humanos , Concentração de Íons de Hidrogênio , Lactente , Organotiofosfatos , Compostos Organotiofosforados/análise , Piretrinas/análise , Reprodutibilidade dos Testes
10.
J Agric Food Chem ; 49(12): 5822-7, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11743769

RESUMO

Analysis by SDS-PAGE and GPC-MS of fermented cocoa extracts shows changes in the amount and composition of the major proteins, accompanied by formation of complex distributions of peptides. MS/MS studies and application of SEQUEST sequencing software have allowed identification of two related peptides, a hexapeptide and a nonapeptide, formed from vicilin, one of the cocoa storage proteins. Time course studies of the two peptides show different abundance profiles and indicate, in part, production of the hexapeptide from the nonapeptide.


Assuntos
Cacau/fisiologia , Peptídeos/metabolismo , Sementes/fisiologia , Cromatografia Gasosa , Fermentação , Cinética , Espectrometria de Massas , Peptídeos/química , Peptídeos/isolamento & purificação , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Proteínas de Armazenamento de Sementes , Fatores de Tempo
11.
Anal Chem ; 73(20): 4862-72, 2001 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-11681462

RESUMO

We have found that the Haarhoff-Van der Linde (HVL) peak function provides excellent fitting to the shapes of CZE peaks. Initially designed for overloaded peaks in gas chromatography, this function describes a Gaussian peak when there is no peak distortion, and a triangular peak when there is no diffusional peak broadening. As such, it is ideal for CZE peaks distorted by electromigration dispersion (EMD). Fitting peaks with this function gives four parameters: three of them can be related to the Gaussian peak that would have been obtained in case of no EMD; the last one is a measure of the peak distortion. Using moving boundary theory, this peak distortion parameter may readily be expressed in terms of analyte and background electrolyte mobilities and concentrations, electric field, and sample injection length. The variance of an HVL peak is shown to be described by a universal function, and a master equation is presented. The region where EMD adds less than 10% to the Gaussian variance is shown to be very narrowly spread around the mobility matching condition. Under typical CZE operating conditions with an analyte at 1% of the BGE concentration, significant peak distortion is always present. Because the total peak variance is not an addition of the Gaussian and triangular contributions, the HVL model and the methodology introduced here should always be used to correctly combine variances.

12.
Rapid Commun Mass Spectrom ; 15(15): 1341-5, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11466795

RESUMO

Gas-phase cluster formation between the quaternary ammonium pesticides paraquat, diquat, difenzoquat, chlormequat and mepiquat, and chloride and acetate anions present in a liquid chromatography (LC) mobile phase, has been studied using electrospray mass spectrometry. The clusters of paraquat, mepiquat and chlormequat were revealed over the entire m/z range of the mass spectrometer, and their formation is dependent on the concentrations of both the cationic and the anionic species. Mepiquat and chlormequat form clusters of the type [2M(q)(+) + A(-)](+), where M(q)(+) is the quaternary ammonium cation and A(-) is the anion. Paraquat forms a cluster species with ammonia and also an ion-pair complex with chloride anions. Diquat and difenzoquat did not form observable ion-pair complexes or clusters with any of the anions studied. Competitive binding of acetate and chloride anions reflects the higher charge density of chloride, which forms the dominant clusters with mepiquat and chlormequat. The formation of cluster species has implications for the quantification of quaternary ammonium pesticides and may have an influence on the linearity of calibrations.


Assuntos
Praguicidas/química , Compostos de Amônio Quaternário/química , Espectrometria de Massas por Ionização por Electrospray , Acetatos/química , Cátions , Cloretos/química , Clormequat/química , Cromatografia Líquida , Diquat/química , Estrutura Molecular , Paraquat/química , Piperidinas/química , Pirazóis/química
13.
Electrophoresis ; 22(8): 1460-7, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11386657

RESUMO

The present study reports a novel method for the separation of the high-molecular-weight anionic polysaccharides, iota, kappa, and lambda carrageenans, in capillary electrophoresis (CE). Carrageenan samples are first derivatised with 9-aminopyrene-1,4,6-trisulfonic acid (APTS), separated in an ammonium acetate background electrolyte (BGE) and detected with laser-induced fluorescence (LIF). The effects of changes of instrumental parameters (temperature, injection mode, field strength) and the composition of the BGE (concentration and pH) are reported, and are explained in terms of the physical chemistry of the BGE and the biopolymers. Optimal separation conditions for kappa, iota, and lambda carrageenans, including an APTS internal standard, were found in a polyvinyl alcohol coated capillary with an ammonium acetate BGE of low concentration (25 mM) and moderate pH (8.0). This BGE gave the best reproducibility in tests on iota/kappa mixtures, with relative standard deviations (RSDs) in migration times and normalised peak areas (relative to the APTS internal standard) of less than 0.1% and 1%, respectively. Using this BGE at 50 degrees C and a voltage of 30 kV, all three carrageenan subtypes were separated in a run time of 3 min.


Assuntos
Carragenina/isolamento & purificação , Eletroforese Capilar/métodos , Carragenina/química , Condutividade Elétrica , Eletrólitos , Concentração de Íons de Hidrogênio , Estrutura Molecular , Plantas/química , Temperatura
14.
Rapid Commun Mass Spectrom ; 15(9): 699-707, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11319792

RESUMO

A detailed MS(n) study on an ion trap instrument of the quaternary ammonium pesticides paraquat, diquat, difenzoquat, mepiquat and chlormequat reveals a number of ions not reported previously, and has allowed examination of the fragmentation pathways. A number of transitions that are highly specific to each quat have been identified. Optimal ion trap operating conditions determined using Simplex optimisation can promote either detection of a particular fragmentation transition or a range of MS/MS product ions with a high overall signal response. Thus, fragmentation conditions were optimised to enhance the specificity or sensitivity of MS/MS methods.


Assuntos
Praguicidas/análise , Compostos de Amônio Quaternário/análise , Cromatografia Líquida , Espectrometria de Massas , Padrões de Referência , Soluções
15.
Electrophoresis ; 22(1): 117-22, 2001 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11197158

RESUMO

Binding constants for tetraphenylborate and tetraphenylphosphonium ions (Ph4B- and Ph4P+) to cyclodextrins (CDs) to give 1:1 host-guest complexes have been measured using capillary electrophoresis. Mobilities of the ions as a function of gamma-CD concentration give binding constants, K, of 1.08 x 10(5) M-1 for Ph4B- and 0.6 x 10(1) M-1 for Ph4P+. This dramatic difference of four orders of magnitude in binding constants is not seen with beta-CD (K = 7.7 x 10(1) M-1 for Ph4B- and 3.7 x 10(1) M-1 for Ph4P+) or dimethyl (DM)-beta-CD (K = 46 x 10(1) M-1 for Ph4B-1 and 7.7 x 10(1) M-1 for Ph4P+). The crystal and hydrodynamic radii of the ions, the latter calculated from their absolute mobilities, indicate that Ph4B- is smaller than the gamma-CD cavity, whereas Ph4P+ is approximately the gamma-CD cavity size. Results suggest that Ph4B- fits exactly into a gamma-CD cavity, with hydrophobic contacts involving several of the phenyl rings, whereas Ph4P+ is too large to enable these multiple contacts to be made. When only a single phenyl ring can fit into the CD cavity, binding strengths are in the order DM-beta-CD > beta-CD > gamma-CD and Ph4B- > Ph4P+. Measurement of electrophoretic mobilities of the complexes shows that their hydrodynamic radii are in the order gamma-CD < beta-CD approximately DM-beta-CD for Ph4B- and gamma-CD > beta-CD approximately DM-beta-CD for Ph4P+.


Assuntos
Ciclodextrinas/química , Oniocompostos/química , Compostos Organofosforados/química , Tetrafenilborato/química , Eletroforese Capilar/métodos , Íons , Estrutura Molecular
16.
J Chromatogr A ; 907(1-2): 313-20, 2001 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-11217038

RESUMO

A new capillary electrophoretic method for trace analysis of gamma-cyclodextrin, gamma-CD, in a sample of beta-CD has been developed, building on our recent work in which the tetraphenylborate ion, Ph4B-, was found to bind to gamma-CD three orders of magnitude more strongly than to beta-CD. The method involves measurement of the change of net electrophoretic mobility of Ph4B- and its CD complexes in a background electrolyte containing a fixed concentration of beta-CD. Good linearity was found between 1/deltamu and 1/Cgamma where deltamu is the difference in the mobility of Ph4B- in the beta-CD solution at a given and at zero concentration of gamma-CD, and Cgamma the gamma-CD concentration. The limit of detection for gamma-CD in a beta-CD sample was found to be 0.020% (w/w), and high precision and accuracy were obtained.


Assuntos
Ciclodextrinas/análise , Ciclodextrinas/química , Eletroforese Capilar/métodos , beta-Ciclodextrinas , gama-Ciclodextrinas , Calibragem , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
J Chromatogr A ; 939(1-2): 41-8, 2001 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-11806544

RESUMO

Use of instrumentation developed to enable simultaneous monitoring of optical rotation (OR) and transmittance allows OR measurements to be made in the presence of high levels of absorbance, scattering or other effects that change the intensity of the plane-polarised light at the photodiode detector. This extends the application of OR detection to areas where it was previously difficult. Examples of the application of high-performance liquid chromatography (HPLC) with the improved OR detector include (i) the analytical scale separation of fructose and sucrose and (ii) the semi-preparative separation of enantiomers of warfarin and Trögers base. A signal-to-noise improvement of up to 150% is found when comparing signals with and without correction for transmittance changes. The improved OR detector has been used in series with a UV detector and the system shown to be suitable for on-line measurement of peak purity in separations using a chiral column under overload conditions.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Análise Espectral/métodos , Frutose/isolamento & purificação , Lasers , Espalhamento de Radiação , Estereoisomerismo , Sacarose/isolamento & purificação , Varfarina/química , Varfarina/isolamento & purificação
18.
J Chromatogr A ; 897(1-2): 399-404, 2000 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-11128224

RESUMO

Two published separations, using electrospray mass spectrometry (ES-MS), exhibit significant differences in limits of detection (LODs) for chlormequat cation in pear. Separation on ODS1, confirmed to result from ion-exchange, gives shorter analysis times and calibration over a wider concentration range than on an SCX cation-exchange column. The superior LOD using ODS1 (0.04 ng ml(-1) vs. 1.0 ng ml(-1)) results mainly from better chromatographic peak shape. Separation on ODS1 combined with optimised ES-MS detection allows direct quantification of chlormequat on an ion trap instrument at levels lower than those required for residue analysis in foods and also in drinking water.


Assuntos
Clormequat/análise , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia por Troca Iônica/métodos , Sensibilidade e Especificidade
19.
Rapid Commun Mass Spectrom ; 14(2): 112-7, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10623939

RESUMO

Optimisation of the activation parameters for ion trap mass spectrometric analysis of the chlormequat cation using simplex optimisation enabled the product ion (m/z 58) response to be improved 1000-fold. A comparison of the sensitivity of the optimised ion trap mass spectrometer with that of a triple quadrupole mass spectrometer for liquid chromatography/tandem mass spectrometry (LC/MS/MS) showed that similar limits of detection (LODs) could be achieved. For the MS/MS transition of the (35)Cl precursor to the most abundant product, LODs were 0.8 ng cation mL(-1) (0.004 mg cation kg(-1) pear equivalent) and 1.0 ng cation mL(-1) (0.005 mg cation kg(-1) pear equivalent) on the triple quadrupole and ion trap instrument, respectively.


Assuntos
Clormequat/análise , Cromatografia Líquida/métodos , Frutas/química , Espectrometria de Massas/métodos , Extratos Vegetais/análise , Resíduos de Drogas/análise , Sensibilidade e Especificidade
20.
Anal Chem ; 71(19): 4376-84, 1999 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-21662863

RESUMO

A fundamental limitation to the use of single-point absorbance detection for capillary electrophoresis is irradiance, since it is not possible to create an image at the detection point on capillary that is brighter than the light source. This limitation may be overcome by illuminating a length of the capillary using a fiber-optic bundle and using a charge coupled device (CCD) camera that can image the full length of the illuminated zone. The present paper describes design and development of a CCD detector for UV absorbance that can be used in both multiwavelength and single-wavelength modes. The CCD camera images analyte peaks in the capillary dimension, together with wavelength-resolved absorbance in the dimension perpendicular to the capillary. Successive snapshots of the peaks are added together, after appropriate correction for time-dependent peak displacement, without sacrificing spatial resolution. Measured baseline rms noise values at 200 nm are 34 µAU using a holographic grating in multiwavelength mode and 8 µAU with the addition of a band-pass filter. Both values are in excellent agreement with calculations of limiting shot noise. Performance in multiwavelength mode is constrained by the 470-ms readout time of the CCD used, which sets a maximum duty cycle of 2.3%. Noise contributions from source intensity fluctuations are reduced by using a portion of the CCD image to provide a baseline reference signal. With 4-hydroxybenzoate as test analyte, the linear dynamic range in multiwavelength mode is shown to be between 3 and 4 orders of magnitude. High-quality spectra of 2-, 3-, and 4-methylbenzoates are obtained on capillary and used in deconvolution of closely migrating peaks of the 2- and 3-isomers.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...