Biomedical subjects

Gabriel Vivó-Truyols

Publications and source records attributed to Gabriel Vivó-Truyols.

5 recordsLinked to original sources

PubMed2006

Development of an algorithm for peak detection in comprehensive two-dimensional chromatography.

A method for peak detection in two-dimensional chromatography is presented. The algorithm applies first the methods developed for peak detection in one-dimensional chromatography to detect peaks in one dimension. In a second step, a decision tree is applied to decide which one-dimensional peaks are originated from the same compound and have to be 'merged' into one two-dimensional peak. To this end, different features of the peaks (second-dimension peak regions and second-dimension retention times) are compared and different criteria (common peak regions, retention time differences, unimodality in the first dimension) are applied. Different options can be used, depending on the nature of the data. The user controls this decision tree by establishing several options and "switches". The algorithm was tested with GCxGC chromatograms obtained for a commercial air-freshener sample, detecting and merging the modulated peaks belonging to the same compound. Recommendations for the set of options and switches are given. A utility that calculates and sums peak areas from merged peaks is added to facilitate automated quantification. Although the algorithm was developed for GCxGC, its application to comprehensive two-dimensional liquid chromatography (LCxLC) data should at most require minor modifications.

Algorithms↗

PubMed2006

Automatic selection of optimal Savitzky-Golay smoothing.

A method to select the optimal window size of the Savitzky-Golay (SG) algorithm is presented. The approach is based on a comparison of the fitting residuals (i.e., the differences between the input signal and the smoothed signal) with the noise of the instrument. The window size that yields an autocorrelation of the residuals closest to the autocorrelation of the noise of the instrument is considered optimal. The method is applied in two steps. In a first step, the lag-one autocorrelation value of the noise of the instrument is computed through the study of a blank signal. In a second step, the SG algorithm is applied to "smooth" the signal using different window sizes. The method was applied to data from NMR, chromatography, and mass spectrometry and was shown to be robust. It finds the optimal window size for different signal features. This allows the method to be used in an unsupervised way, embedded in a more complex algorithm in which smoothing and/or differentiation of signals is required, provided that the lag-one autocorrelation value of the instrument noise does not change.

Journal Article↗

PubMed2005

A protocol for designing comprehensive two-dimensional liquid chromatography separation systems.

In this paper a protocol is proposed for establishing suitable column dimensions (length and diameters), particle sizes, flow rates, and second-dimension injection volumes (i.e. loop sizes) in comprehensive two-dimensional liquid chromatography (LC x LC). The chromatographer should select the maximum allowable first-dimension retention time, which is approximately equal to the overall analysis time. Also, (s)he should define the maximum allowable pressure in both dimensions and the (minimum) diameter of the first-dimension column. The proposed protocol provides design parameters corresponding to the ideal (theoretically optimal) conditions or to realistic practical conditions. The protocol also allowed us to study the implications of contemporary developments in LC, such as the use of high temperatures (implying reduced viscosities and increased diffusion coefficients), monolithic columns (implying smaller flow-resistance factors), and ultra-high-pressure LC. The combination of (reversed-phase or normal-phase) liquid chromatography with size-exclusion chromatography (LC x SEC) is frequently employed for analysing complex polymers. The proposed protocol is used to design a suitable LC x SEC system under realistic conditions. The results resemble the systems that have been designed and implemented by expert chromatographers, but they also indicate how current practice can be improved.

Algorithms↗

PubMed2005

Performance limits of monolithic and packed capillary columns in high-performance liquid chromatography and capillary electrochromatography.

A method is proposed for the comprehensive characterization and comparison of columns in the high-performance liquid chromatographic (HPLC) and capillary electrochromatographic (CEC) modes. Using this approach, column parameters such as the number of plates, the eddy-diffusion and mass-transfer contributions to peak broadening, the permeability, and the analysis time are incorporated in a single graph and a comparison in terms of efficiency and speed is obtained. The chromatographic performance of silica-based and polymer-based monolithic capillary columns is discussed and a comparison is made with the performance of packed columns. Also, the potential of ultra-high-pressure liquid chromatography is discussed in this context. In the HPLC mode, the best results were obtained with silica monoliths; in the CEC mode, the low-density methacrylate-ester-based monoliths showed the best performance.

Chromatography, High Pressure Liquid↗

PubMed2005

Chemical variance, a useful tool for the interpretation and analysis of two-dimensional chromatograms.

A new method is presented for the analysis of comprehensive two-dimensional data. The approach complements existing chemometric methods for analysing these kinds of data (e.g. multivariate-curve-resolution methods, MCR), and is especially suited for the analysis of families of compounds. The method is based on finding a new pair of axes (replacing the retention time axes) to represent the data. A drop in the matrix rank is observed when one of the axes collects all the variance for a certain family of compounds. This is achieved by introducing retention models (in both chromatographic dimensions) that describe the behaviour of a family of compounds as a function of the property that varies between the members. After this transformation, a single family of compounds gives rise to a single source of variance. This suggests the application of MCR techniques in a second step to separate the contributions of different (overlapped) families of compounds. For the latter application, more research has to be performed. The approach is illustrated using the separation of families of functional poly(methyl-methacrylate) polymers with different numbers of hydroxyl end groups and degrees of polymerisation or, equivalently, with the molecular weight as the key descriptive property within one family.

Algorithms↗