Enantioseparation of nonsteroidal anti-inflammatory drugs using single-isomer amino cyclodextrin derivatives in nonaqueous capillary electrophoresis

Poster (2006)

Determination of salbutamol enantiomers in urine by nonaqueous capillary electrophoresis-mass spectrometry

Poster (2006)

Determination of a melanoma biomarker in human plasma the 5-S-cysteinyl-l-dopa by LC-ESI-MS-MS

Conference (2006)

LC method for the determination of R-timolol in S-timolol maleate: Validation of its ability to quantify and uncertainty assessment.

in Talanta (2006), 68(4), 1166-75

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel ... [more ▼]

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel validation strategy based on the accuracy profiles was used to select the most appropriate regression model, to assess the method accuracy within well defined acceptance limits and to determine the limits of quantitation as well as the concentration range. The validation phase was completed by the investigation of the risk profiles of various acceptable regression models in order to ensure the risk of obtaining the future measurements outside the acceptance limits fixed a priori. On the other hand, the present paper also shows how data used in this validation approach can be used to estimate the measurement uncertainty. The uncertainty derived from beta-expectation tolerance interval (sigma(Tol)(2)), which is equal to the uncertainty of measurements as well as the expanded uncertainty (U(x)) using a coverage factor k=2 was estimated. The uncertainty estimates obtained from validation data were finally compared with those obtained from interlaboratory and robustness studies. [less ▲]

Comparaison de trois approches pour l'estimation de l'incertitude.

in Acta Clinica Belgica. Supplementum (2006), (1), 60-2

Three different approaches for the estimation of uncertainty measurements using the same analytical method were compared, namely validation, robustness and inter-laboratory studies. The uncertainty ... [more ▼]

Three different approaches for the estimation of uncertainty measurements using the same analytical method were compared, namely validation, robustness and inter-laboratory studies. The uncertainty obtained with the robustness study! predicted well the uncertainty of the inter-laboratory study. On the other hand, the uncertainty estimation obtained with the validation study is lower than those obtained with the two other approaches but is still acceptable as long as the analytical method will be used in a single laboratory. [less ▲]

Precision study on capillary electrophoresis methods for metacycline.

in Electrophoresis (2006), 27(12), 2317-29

A CE method for metacycline (MTC) determination was investigated in an inter-laboratory experiment. Many problems were encountered in this study, most of which were related to the transfer of the method ... [more ▼]

A CE method for metacycline (MTC) determination was investigated in an inter-laboratory experiment. Many problems were encountered in this study, most of which were related to the transfer of the method to different CE equipment. The reported problems could be classified into different categories: problems related to the precision, to the parameters in the protocol, and to the MTC peak shape. As the peak shape problem was partially responsible for the poor precision, a new CE method was developed in order to obtain a good MTC peak shape on all equipment. The precision of this new method for MTC determination was examined in an intermediate precision study, where the influence of the factors "time" and "equipment" was investigated. Although the new method could be transferred to different instruments, the precision remained poor mainly due to the contributions of the between-replicate and the between-injection variances. [less ▲]

TRANSFER OF A MULTIDIMENSIONAL ON-LINE SPE-LC-ECD METHOD FOR THE DETERMINATION OF THREE MAJOR CATECHOLAMINES IN NATIVE HUMAN URINE

Poster (2006)

Enantioseparations in nonaqueous capillary electrophoresis using charged cyclodextrin derivatives as chiral selectors

Conference (2006)

Uncertainty assessment from robustness testing applied on an LC assay for R-timolol and other related substances in S-timolol maleate

in Analytica Chimica Acta (2005), 531

The robustness testing of a normal-phase liquid chromatographic (LC) method for the Determination of R-timolol and other related substances in S-timolol maleatewas performed applying a two-level ... [more ▼]

The robustness testing of a normal-phase liquid chromatographic (LC) method for the Determination of R-timolol and other related substances in S-timolol maleatewas performed applying a two-level Plackett–Burman design. Two qualitative and five quantitative factors were examined. Two types of responses were considered, qualitative, i.e. chromatographic performance criteria, and quantitative ones. The latter were taken into account to determine if the analytical procedure was robust. The quantitative responses were the contents of R-timolol in two S-timolol maleate samples. Even though some significant factor effects were observed on the qualitative responses, the R-timolol contents were not significantly different from those observed at nominal conditions, which demonstrated the robustness of the procedure. Since the experiments of the Plackett–Burman design can be assimilated to laboratories in an nterlaboratory study, uncertainty can be evaluated using the robustness test data. The robustness test was set-up in such a way that the required variances could be estimated. It was shown that the robustness set-up allows estimating the reproducibility uncertainty without performing an interlaboratory study. [less ▲]

Collaborative study of an liquid chromatographic method for the determination of R-timolol and other related substances in S-timolol maleate

in Analytica Chimica Acta (2005), 546(2), 182-192

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three ... [more ▼]

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three different S-timolol maleate samples. Eight laboratories, all located in Europe, participated in the study. The quantitative results obtained were used to estimate the uncertainty on the content of the different impurities. For that purpose, a set-up was adapted from the ISO guidelines 5725-2, which allowed the estimation of the different variances, i.e. the between-laboratories (s(laboratories)(2)), the between-days (s(days)(2)) and the between-replicates (s(replicates)(2)), The variances of repeatability (s(r)(2)) and reproducibility (s(R)(2)) were then calculated using the equations s(r)(2) = s(replicates)(2) and s(R)(2) = s(replicates)(2) + s(days)(2) + s(laboratories)(2). For the timolol impurities, it was found that the estimated uncertainty seem to be concentration-dependent. Since the LC method which combines the compendial ones for enantiomeric purity and related substances testing was applied to evaluate uncertainty in this collaborative study, it was shown how a laboratory can evaluate the uncertainty of its results when applying the method in the future. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]