Y. Martín-Biosca

Cyclodextrins in capillary electrophoresis: Recent developments and new trends

Despite the fact that extensive research in the field of separations by capillary electrophoresis (CE) has been carried out and many reviews have been published in the last years, a specific review on the use and future potential of cyclodextrins (CDs) in CE is not available. This review focuses the attention in the CD-CE topic over the January 2013-February 2014 period (not covered by previous more general CE-reviews). Recent contributions (reviews and research articles) including practical uses (e.g. solute-CD binding constant estimation and further potentials; 19% of publications), developments and applications (mainly chiral and achiral analysis; 38 and 24% of publications, respectively) are summarized in nine comprehensive tables and are commented. Statistics and predictions related to the CD-CE publications are highlighted in order to infer the current and expected research interests. Finally, trends and initiatives on CD-CE attending to real needs or practical criteria are outlined.

Micellar liquid chromatography for prediction of drug transport

The vast majority of well absorbed drugs are transported passively across the cell membranes. Physicochemical descriptors of drug molecules that are believed to influence transcellular transport are routinely used to predict drug absorption by means of complex mathematical models. In this paper, a new in vitro method, based on the retention data in micellar liquid chromatography (MLC), is validated for the prediction of passive drug absorption. The retention of a heterogeneous drugs set in MLC using Brij 35 as surfactant in the mobile phase is compared with the retention data reported in literature obtained in red cell membrane lipid liposomes, human red cell membranes vesicles (vesicles), native membranes of adsorbed red cells (ghosts) and egg phospholipids liposomes [Beigi et al., Int. J. Pharm., 164 (1998) 129-137]. Finally, the correlation between the logarithm of retention factors in MLC and reported oral drug absorption values for barbiturates and beta-blockers is studied. Predictive regression models for estimating oral drug absorption using the logarithm of the retention values as independent variable are proposed.

QRAR Models for Central Nervous System Drugs using Biopartitioning Micellar Chromatography

The capability of biopartitioning Micellar Chromatography, BMC, to describe and estimate pharmacokinetic and pharmacodynamic parameters of central nervous system drugs is reviewed in this article. BMC is a mode of micellar liquid chromatography, MLC, that uses micellar mobile phases of Brij35 (polyoxyethilene(23) lauryl ether) prepared in physiological conditions (pH, ionic strength). The retention of a drug in this system depends on its hydrophobic, electronic and steric properties, which also determine its biological activity. The results of BMC studies suggest that this in vitro approach is an attractive useful tool to be implemented into the lead optimization step of drug development scheme.

Enantiomeric separation of chiral phenoxy acid herbicides by electrokinetic chromatography. Application to the determination of analyte-selector apparent binding constants for enantiomers

The enantiomeric resolution of chiral phenoxy acid herbicides was performed by electrokinetic chromatography using a cyclodextrin as chiral pseudophase (CD‐EKC). A systematic evaluation of several neutral and charged cyclodextrins was made. Among the cyclodextrins tested, (2‐hydroxy)propyl β‐cyclodextrin (HP‐β‐CD) was found to be the most appropriate for the enantioseparation of phenoxy acids. The influence of some experimental conditions, such as nature and pH of the background electrolyte, chiral selector concentration, and temperature, on the enantiomeric separation of phenoxy acids was also studied. The use of a 50 mM electrolyte solution in ammonium formate at pH 5 and a temperature of 40°C enabled the enantiomeric resolution of four of the six phenoxy acids investigated (2‐phenoxypropionic acid, 2‐(3‐chlorophenoxy)propionic acid, 2‐(4‐chlorophenoxy)propionic acid, and 2‐(2,4‐dichlorophenoxy)propionic acid) obtaining migration times ranging from 9 to 15 min. Mixtures of the two phenoxy acids not enantiomerically resolved (2‐(4‐chlorophenoxy)‐2‐methylpropionic acid and 2‐(2,4,5‐trichlorophenoxy)propionic acid) and up to three of the phenoxy acids enantiomerically resolved were separated in about 15 min. Finally, the apparent binding constants for each enantiomer‐HP‐β‐CD pair were calculated at two temperature values (20 and 40°C).

Determination of barbiturates in urine by micellar liquid chromatography and direct injection of sample.

A liquid chromatographic procedure for the determination of six barbiturates (barbital, diallyl barbituric acid, phenobarbital, butabarbital, amobarbital and pentobarbital) in urine samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C18 analytical column and a guard column of similar characteristics. The UV detector was set at 240 nm. A study to select adequate composition of the micellar mobile phase for the separation of these compounds in urine samples is performed. Maximum resolution was achieved with a 0.07 M sodium dodecylsulphate-0.3% propanol at pH 7.4 eluent. Limits of detection at 240 nm were ranged between 0.13 microg ml(-1) for diallyl barbituric acid and 2.7 microg ml(-1) for amobarbital. The procedure allows for the determination of these compounds in 20 minutes, it does not require prior a sample preparation step and it can be very useful to the investigation of intoxication.

In-line capillary electrophoretic evaluation of the enantioselective metabolism of verapamil by cytochrome P3A4

In this paper a methodology for the in-line evaluation of enantioselective metabolism by capillary electrophoresis has been developed and applied to the study of verapamil metabolism by cytochrome P3A4. The developed methodology comprises an in-capillary reaction step carried out by electrophoretically mediated microanalysis and a separation step in which highly sulfated β-cyclodextrin with partial filling technique has been employed as chiral selector for verapamil and norverapamil enantiomers resolution, joining the advantages of both methodologies in a unique assay. Kinetic parameters of the enzymatic reaction (Km and Vmax) have been evaluated for both verapamil enantiomers by non-linear fitting of experimental data obtained under intermediate precision conditions to Michaelis-Menten equation. Km and Vmax estimated values were 51±9 μM and 22±2 pmol min(-1) (pmol CYP)(-1) for S-VER and 47±9 μM and 21±2 pmol min(-1) (pmol CYP)(-1) for R-VER. Consequently, slight enantioselectivity was found for the CYP3A4 metabolism of verapamil. However, since confidence intervals of estimates overlap, we cannot assure a significant enantioselectivity. Intrinsic clearance values were also estimated from Km and Vmax for both enantiomers.

Fast enantiomeric separation of uniconazole and diniconazole by electrokinetic chromatography using an anionic cyclodextrin: Application to the determination of analyte‐selector apparent binding constants for enantiomers

The enantiomeric resolution of the fungicides uniconazole and diniconazole was performed using electrokinetic chromatography with cyclodextrins as pseudostationary phase (CD‐EKC). A systematic evaluation of several chiral selectors was made. The anionic derivative carboxymethylated‐γ‐cyclodextrin (CM‐γ‐CD) was found to be the most appropriate for the enantioseparation of fungicides among all cyclodextrins tested. The influence of some experimental conditions such as nature and buffer pH, chiral selector concentration, and temperature on the enantiomeric separation of the compounds studied was also investigated. The use of a 50 mM phosphate buffer (pH 6.5) containing 5 mM CM‐γ‐CD and a temperature of 50°C enabled the baseline enantioresolution of mixtures of uniconazole and diniconazole in less than 5 min. In addition, apparent binding constants for each enantiomer‐CM‐γ‐CD pair at several temperatures, as well as thermodynamic parameters for binding were calculated.

Rapid in vitro test to predict ocular tissue permeability based on biopartitioning micellar chromatography

The drug permeability prediction across the ocular tissues is important in the development of new drugs and drug delivery strategies. Physicochemical characteristics of drugs, mainly acid-base character, hydrophobicity and the molecular size determine both their transport across the eye tissue barriers and their retention in biopartitioning micellar chromatography (BMC). An in vitro model able to describe and predict the whole cornea drug permeability is proposed. The model uses the retention of drugs in BMC and molecular weight (MW) as predictive variables. The relationships between drug retention data in BMC and their bibliographic permeability values in stroma, epithelium-plus-stroma and endothelium-plus-stroma are also studied. The results show that BMC can be a useful tool to select drug candidates according to their whole cornea permeability at the early stage of the drug discovery process.

Quality Control of Pharmaceuticals Containing Non-Steroidal Anti-Inflammatory Drugs by Micellar Liquid Chromatography

SummaryA liquid chromatographic procedure is described for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, nabumetone, naproxen, piketoprofen, and tolmentin in pharmaceutical preparations. The compounds were separated on a Kromasil C18 analytical column, with a guard column of similar characteristics; the mobile phase was 0.06 M cetyltrimethylammonium bromide, at pH 7, containing 10% 1-butanol. At a flow rate of 1 mL min−1 the elution time of the most retained compound was 23 min. Limits of detection were between 0.01 μ g mL−1 for diclofenac and 0.2 μ g mL−1 for naproxen. The proposed method enables the determination of non-steroidal anti-inflammatory drugs in pharmaceutical preparations. Recoveries were between 95 and 108% of the nominal content declared by the manufacturer and relative standard deviations were <6%.

On the internal multivariate quality control of analytical laboratories. A case study: the quality of drinking water

Abstract Multivariate statistical process control (MSPC) tools, based on principal component analysis (PCA), partial least squares (PLS) regression and other regression models, are used in the present study for automatic detection of possible errors in the methods used for routine multiparametric analysis in order to design an internal Multivariate Analytical Quality Control (iMAQC) program. Such tools could notice possible failures in the analytical methods without resorting to any external reference since they use their own analytical results as a source for the diagnosis of the methods quality. Pseudo-univariate control charts provide an attractive alternative to traditional univariate and multivariate control charts. This approach uses the relative prediction error in percentage, Er (%), which is calculated from a multivariate model such as PLS, as the univariate control variable. Er offers quantitative information on the magnitude of the error and is sensitive to systematic errors at the 10% level (which are of analytical interest). Finally, its capacity to detect/quantify error in a single method can be checked a priori. As a case study for applying such strategies in routine analysis, the problem of the quality of drinking water was examined.