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J Vial

Publications and source records attributed to J Vial.

At least 19 recordsLinked to original sources
PubMed2006

An interlaboratory study to evaluate potential matrix reference materials for herbicides in water.

Matrix reference materials (MRM) are essential tools for the validation of analytical protocols. Nowadays, there are no such materials for the determination of herbicides in water. Pesticides stored in acetonitrile and stored on solid phase extraction (SPE) cartridges previously percolated with a water sample spiked with triazines and phenylureas have proven to be good candidates for reference materials because of their satisfactory stability under appropriate temperature conditions. To evaluate the behaviors of these materials containing pesticides and to be analyzed by liquid chromatography, a collaborative study including 15 laboratories has been organized. Observed reproducibility on candidate materials after the removal of extreme results was 16.1% for the vials with pesticides in acetonitrile (at around 0.125 mg/L) directly analyzed, 29.2% for a water sample spiked with the pesticides (at around 0.5 microg/L) analyzed after preconcentration on a cartridge and 26.7% for the cartridges previously percolated with a water containing the pesticides (250 mL at around 0.5 microg/L for each pesticide) analyzed after elution. Such dispersion values are quite compatible with the requirement of a further certification for such materials.

Acetonitriles↗
PubMed2005

Development and validation of a reversed-phase liquid chromatography method for the quantitative determination of carboxylic acids in industrial reaction mixtures.

Usually analysis of low molecular-mass carboxylic acids was performed by anion-exchange or ion-exclusion chromatographic methods. Reversed-phase liquid chromatography (RPLC) was evaluated in this work as an alternative method for the analysis of low molecular-mass aliphatic mono- and di-carboxylic acids (formic, acetic, propionic, butyric, valeric, caproic, succinic, glutaric and adipic) in aqueous media. The separation of the nine organic acids was optimised in 21 min on a high-density C18 column with an elution gradient made up of HClO4 aqueous solution 10(-3) mol L(-1) and acetonitrile. For the quantitation, external standard and standard addition methods were compared. Both methods gave similar results, so the most convenient method, external standard, was chosen for acids quantitation. Then the method had been validated and applied to the semi-quantitative analysis of formic and acetic acids and to the quantitative analysis of the others compounds in industrial reaction mixtures with concentrations ranging from 20 to 570 ppm.

Carboxylic Acids↗
PubMed2005

Reversed-phase liquid chromatography testing. Role of organic solvent through an extended set of columns.

Column testing is a primary concerns for analysts. It is of use not only for the choice of set of development columns with different behaviors, but also for a substitution column in a validated method or as a quality control of new batches of stationary phase. A validated chromatographic procedure for column testing was applied to 42 commercially available columns, including alkyl, polar embedded and Aqua type stationary phases. This procedure was based on the use of two different solvents: MeOH and MeCN; and two different solvent/aqueous buffer fractions. Principal component analysis has been combined to hierarchical cluster analysis to provide both rational and objective classifications. The solvent effects were then studied on the obtained representations, revealing the necessity for considering both the solvent nature and its fraction in RPLC column testing. Differences observed depending on the solvent nature and fractions revealed quite different chromatographic behaviors according to these parameters.

Chromatography, Liquid↗
PubMed2004

Reversed-phase liquid chromatography column testing: robustness study of the test.

Choosing the right RPLC column for an actual separation among the more than 600 commercially available ones still represents a real challenge for the analyst particularly when basic solutes are involved. Many tests dedicated to the characterization and the classification of stationary phases have been proposed in the literature and some of them highlighted the need of a better understanding of retention properties to lead to a rational choice of columns. However, unlike classical chromatographic methods, the problem of their robustness evaluation has often been left unaddressed. In the present study, we present a robustness study that was applied to the chromatographic testing procedure we had developed and optimized previously. A design of experiment (DoE) approach was implemented. Four factors, previously identified as potentially influent, were selected and subjected to small controlled variations: solvent fraction, temperature, pH and buffer concentration. As our model comprised quadratic terms instead of a simple linear model, we chose a D-optimal design in order to minimize the experiment number. As a previous batch-to-batch study [K. Le Mapihan, Caractérisation et classification des phases stationnaires utilisées pour l'analyse CPL de produits pharmaceutiques, Ph.D. Thesis, Pierre and Marie Curie University, 2004] had shown a low variability on the selected stationary phase, it was then possible to split the design into two parts, according to the solvent nature, each using one column. Actually, our testing procedure involving assays both with methanol and with acetonitrile as organic modifier, such an approach enabled to avoid a possible bias due to the column ageing considering the number of experiments required (16 + 6 center points). Experimental results were computed thanks to a Partial Least Squares regression procedure, more adapted than the classical regression to handle factors and responses not completely independent. The results showed the behavior of the solutes in relation to their physico-chemical properties and the relevance of the second term degree of our model. Finally, the robust domain of the test has been fairly identified, so that any potential user precisely knows to which extend each experimental parameter must be controlled when our testing procedure is to be implemented.

Chromatography, Liquid↗
PubMed2004

Testing of "special base" columns in reversed-phase liquid chromatography. A rational approach considering solvent effects.

A methodology for building a chromatographic test aiming at characterizing special base stationary phases was described. Instead of choosing its conditions a priori, a "full" comprehensive test based on extended running conditions was performed on a 12 column set. The conditions were carefully chosen from their ability to take into account the solvent and the pH effects. Principal component analysis (PCA) has been combined to hierarchical cluster analysis both to provide interpreted classifications and to reduce drastically the test itself by eliminating redundant information. The final reduced test can be considered optimal because the minimized set of test conditions allows to provide as much information as in the initial full test.

Chromatography, Liquid↗
PubMed2003

Photocatalytic treatment of diuron by solar photocatalysis: evaluation of main intermediates and toxicity.

The technical feasibility, mechanisms, and performance of degradation of aqueous diuron (22 mg/L) have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale (made up of Compound Parabolic Collectors (CPCs) specially designed for solar photocatalytic applications) and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated en route to mineralization by both systems. Total disappearance of diuron is attained by both phototreatments in 45 min. 100% of chlorine was recovered as chloride, but total recovery of nitrogen as inorganic ions was not attained. 90% of mineralization was reached after 200 min of photocatalytic treatment, but toxicity measured by two different bioassays (Daphnia magna and a Microalga) was reduced to below the threshold (EC50%) in a shorter time. Transformation products evaluated by LC-IT-MS by direct injection of the samples were the same in both cases. The main differences between the two processes were in the amount of transformation products (DPs) generated, not in the DPs detected, which were always the same.

Animals↗
PubMed2003

[Evaluation of adherence to the regulations for declaration of notification of transfusion reactions with fever and chills. A study of the Association Inter-Régionale du Sud-Est d'Hémovigilance (AIRSEH)].

Febrile non-hemolytic transfusion reactions (FNHTR) are the most frequently reported acute adverse effects of blood products, and should be notified within 48 h according to the hemovigilance regulation. In order to study the conformity of these notifications and to search for factors associated with non-conformity, we retrospectively studied all FNHTR notified by voluntary centers of the AIRSEH group from 1st September 1994 to 31st December 1999. Seven hundred and sixty-one FNHTR were registered by 10 centers, most of them were benign (grade 1); 67.8% were non-conform. The non-conformity was associated with the number of biological investigations performed (median number, respectively, 4.24 and 2.94--P = 0.038--in non-conform and conform notifications--P = 0.038) in univariate analysis. Using a logistic regression model, center and severity were the only two factors significantly associated with non-conformity. Different center practices, and in particular the interface between the hospital and the blood bank, may be responsible for the effect center. Moreover, the non-conformity concerns first of all benign FNHTR. A stronger separation between alert and epidemiological surveillance is proposed in order to improve the notifications' conformity.

Adult↗
PubMed2001

Use of porous graphitic carbon coupled with mass detection for the analysis of polar phenolic compounds by liquid chromatography.

Phenolic compounds present in olive mill wastewater (OMW) need to be quantified because of their pollution capacity toward the environment. In the present study, six representative phenolic compounds of OMW were chosen to develop a LC-MS method. The high polarity of the compounds caused problems when using traditional reversed-phase liquid chromatography (RPLC). Consequently, a method was developed on another kind of chromatographic phase: Porous Graphitic Carbon (PGC) involving the use of a tetrahydrofuran (THF) gradient. The influence of THF as mobile phase in LC-MS coupling, which is not common practice, was evaluated. In Atmosperic Pressure Chemical Ionisation (APCI) in the negative ion mode, the presence of THF in the mobile phase did not degrade the MS signal of the target compounds in the conditions studied. On the contrary, an improvement was even observed when the percentage of THF increased. The proposed PGC-LC-MS method was selective and linear for the six phenolic compounds analysed with limits of quantification lower than 5 ppm in all cases. The precision was satisfactory (pooled RSD around 6%). The analyses of OMW matrix spiked sample confirmed the good performance of the proposed method.

Chromatography, Liquid↗
PubMed2001

Degradation of imidacloprid in water by photo-Fenton and TiO2 photocatalysis at a solar pilot plant: a comparative study.

The technical feasibility, mechanisms, and performance of degradation of aqueous imidacloprid have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (<2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with photo-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal anytoxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detected which were always the same. At the end of both processes low concentration (<0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around 1 mg/L of formate in the case of photo-Fenton.

Ferric Compounds↗
PubMed2000

Taking into account both preparation and injection in high-performance liquid chromatography linearity studies

As mentioned in International Conference on Harmonisation publications, linearity is a principal parameter in method validation. The most popular statistical tool used is linear least-squares regression. Contrary to what is still very often practiced, the correlation coefficient can in no way be considered as an indicator of the fit quality. There is in fact a test called the "lack-of-fit test" that enables one to answer the question, "Is the linear model adapted to the calibration curve?". However, this test can give erroneous conclusions when, at each level, several sources of variation for the response are influent. It often occurs in high-performance liquid chromatography, as shown in a following example, where the calibration curve is obtained from repeated injections of repeated dilutions of a parent solution. The lack-of-fit test rejected linearity, although it was at least questionable. In fact, the reason for a discrepancy of this kind lies in the presence of a double source of variation: injection and dilution. It is possible to overcome the problem by mixing a nested ANOVA with the standard least-square linear regression. As shown in an example, implementing this methodology for data processing allows one not only to carry out an unbiased lack-of-fit test but also give estimates of the dispersion introduced respectively by the preparation and the injection.

Journal Article↗
PubMed1998

How to better define the characteristics of dispersion of results in liquid chromatographic analyses through an interlaboratory study. Example of collaborative studies on ketoprofen and spiramycin.

The aim of this study was to use statistical tools, especially the analysis of variance (ANOVA), to improve knowledge of the characteristics of the dispersion of results in high-performance liquid chromatography (HPLC) methods for quantitative analysis. It is in this regard that two interlaboratory studies have been carried out in collaboration with Rhône-Poulenc Rorer. The first concerned the analysis of a single drug product (ketoprofen) and was typically a "simple analysis". The second one involved a complex mixture of drug products and related substances (spiramycin), requiring far more constraining analysis conditions. Preliminary studies of the analyses were carried out to develop an optimized protocol. Statistical exploitation of the data for ketoprofen showed that there was no significant influence of the factors "laboratory" and "preparation", under the conditions of the study. On the other hand, in the case of spiramycin, a significant influence of the factors "laboratory" and "preparation" was observed under the conditions of the collaborative study, indicating that the latter factor must be taken into account to establish certified assays. Results of these two studies will help to determine the factors that have a significant influence, depending on the product and the chromatographic method used. By completing the statistical data base, interlaboratory studies will also contribute in the near future to the elaboration of more rigorous protocols for analytical transfers.

Chromatography, High Pressure Liquid↗
PubMed1995

Combined factor IX and protein C deficiency in a child: thrombogenic effects of two factor IX concentrates.

We have recently described an unusual situation which involved a combination of a factor IX and a protein C deficiency in a young child who presented, according to the bleeding tendency, as a hemophilia B patient. In this particular hemophiliac, baseline prothrombin fragment F1 + 2 levels were unexpectedly elevated and increased after an injection of a very high purity factor IX concentrate. This observation raised a question regarding the substitution schedule in the case of repeated injections of factor IX, since the thrombotic tendency has been a major concern with some factor IX concentrates. We monitored factor IX, prothrombin fragment F1 + 2, and D-dimer plasma levels before and during the 6 hr following the injection of an immunopurified factor IX concentrate. The results showed an increase in the F1 + 2 levels after the factor IX injection, but an increase lower than previously observed with an ion-exchange chromatography-purified concentrate. Furthermore, the F1 + 2 level returned to baseline value 6 hr after administration. This factor IX concentrate seems to be best for use in the patient where repeated injections are involved (as employed during surgery). Moreover, the data point out the advantage of a monoclonal antibody-purified factor IX concentrate over less purified concentrates in a specific situation, with regard to the thrombogenic risk.

Antibodies, Monoclonal↗
PubMed1995

Naproxen concentrations in plasma and synovial fluid and effects on prostanoid concentrations.

OBJECTIVE: To test the hypothesis that unbound concentrations of naproxen in synovial fluid (SF) and plasma (P) are equal over a drug dosage interval at steady state or after a single dose of drug. The relationship between plasma and SF concentrations of naproxen, respectively, and prostaglandin concentrations were also examined. METHODS: Paired, sequential, total, and unbound naproxen concentrations were determined in plasma and SF in 2 groups of 6 patients. A single dose group was given naproxen 500 mg. The chronic dose group was given 500 mg bd for 7 days before collection of blood and SF samples. The effect of naproxen on prostanoid production by clotting whole blood (thromboxane B2, TXB2) and in SF (PGE2, 6-keto-PGF1 alpha) was determined by radioimmunoassay. RESULTS: Average area under the curve (AUC) of unbound (U) naproxen concentrations against time in plasma and SF were the same over a dosage interval at steady state (ratio AUCU,SF/AUCU,P, 1.12 +/- 0.18; p = 0.108), but not after a single acute dose (AUCU,SF/AUCU,P, 1.34 +/- 0.32; p = 0.044). Data from the single dose study revealed that the mean (+/- SD) of the concentrations required for 50% inhibition (EC50) of platelet derived TXB2 by total naproxen was 7.7 +/- 4.4 micrograms/ml (n = 5) and for unbound drug 25.4 +/- 22.0 ng/ml (n = 5). SF prostanoid concentrations after both acute and chronic dosing were low, as expected, but temporal and dose relationships of prostanoid concentrations with SF naproxen could not be discerned. However, this may reflect study design. CONCLUSIONS: The AUC of unbound naproxen in SF and plasma were similar at steady state. Plasma concentrations correlated with inhibition of TXB2 generation by platelets. There was sustained depression of PG concentrations in SF beyond the time suggested by plasma drug concentrations.

Adult↗
PubMed1992

Activation of human monocyte chemiluminescence response by acylpoly(1,3)galactosides derived from Klebsiella pneumoniae.

The stimulating activity of several preparations isolated from a membrane proteoglycan of a nonencapsulated smooth strain of Klebsiella pneumoniae (Kp-MPG) on the oxidative burst of human blood monocytes was assessed by luminol-enhanced chemiluminescence (CL). Five Kp derivatives were studied: a 34-kd acylpoly(1,3)galactoside (APG), obtained by drastic alkaline hydrolysis and purified by chromatography; an APG preparation subjected to acid hydrolysis that removed the core part and all fatty acids, leaving intact the galactose chain of APG (GC-APG); an APG preparation subjected to mild oxidation (ox APG); a preparation obtained by mild alkaline hydrolysis of Kp-MPG, containing additional ester-linked C14 and C16 fatty acids bound to the APG molecule (EFA-APG); and a polymer of the latter compound, APG pol. EFA-APG directly stimulated monocyte CL, whereas Kp-MPG, APG pol, and the whole bacterial cells had little or no activity. APG itself and ox APG induced a weaker response than EFA-APG. Polymyxin B sulfate completely inhibited the CL response to bacterial lipopolysaccharide (LPS) but not to EFA-APG. The stimulating action of EFA-APG on blood monocytes was dependent on the extracellular levels of both calcium and magnesium. Preincubation of monocytes with monoclonal antibody anti-Mac-1 directed against CD11b, the alpha chain of complement receptor type 3 (CR3; CD11b/CD18), strongly inhibited CL activation by EFA-APG and to a lesser extent CL activation by unopsonized zymosan and rough LPS. Altogether, these findings provide indirect evidence for the contribution of the CD11b/CD18 integrin in the functional interaction of EFA-APG with monocyte membranes. They demonstrate the role of fatty acids in the triggering of monocyte oxidative burst, while the polysaccharide chain itself does not contribute to induction of the CL response in this model. In keeping with the effects of EFA-APG and APG, we show that the monocyte CL response was triggered by bacterial LPS from the rough strain of Salmonella minnesota Re 595 and its lipid A, but not by LPS from smooth strains, again suggesting a critical role for the lipid moiety.

Calcium↗
PubMed1987

Single-step procedure for the extraction and purification of leukotrienes B4, C4 and D4.

A rapid and simple method for the on-line concentration and high-performance liquid chromatographic (HPLC) purification of the leukotrienes in good yield from biological fluids is described. Readily available antisera are used in conjunction with this system to give a specific and sensitive assay for leukotrienes B4, C4 and D4 with sub-nanogram limits of detection. Tritium-labelled leukotrienes are used as internal standards, both to locate the leukotrienes post-HPLC and to accurately determine recoveries.

Animals↗