Marcone Augusto Leal de Oliveira

Evaluation of the transdermal permeation of different paraben combinations through a pig ear skin model

Although parabens have several features of ideal preservatives, different studies have shown that they may affect human health due to their estrogenic activity. Therefore, various strategies have been applied to reduce their skin penetration. However, the effect of paraben combinations on transdermal permeation has not yet been investigated. Thus, the objective of this study was to evaluate paraben permeation in pig ear skin using a Franz diffusion cell system with capillary electrophoresis detection, in order to identify which paraben combinations (defined by a factorial design) have the lowest skin permeation. The permeation of isolated parabens was also evaluated and the permeation characteristics, obtained by the Moser model, confirmed that lipophilicity and molecular weight may influence the systemic absorption of these compounds. In previous tests using isolated parabens, methyl and ethyl parabens presented greater retention in the epidermis compared to the dermis, while propyl and butyl parabens had similar retention profiles in these layers. An increase in ethanol concentration and experimental time promoted greater parabens retention in the dermis compared to the epidermis. The binary combinations of methyl and ethyl parabens as well as of methyl and propyl parabens (added to several cosmetic products in order to increase the antimicrobial spectrum) reduced significantly their permeation rates through pig ear skin (with the exception of EP), probably due to the high retention of these parabens in the epidermis and dermis.

Simultaneous determination of first-line anti-tuberculosis drugs by capillary zone electrophoresis using direct UV detection.

An alternative methodology for simultaneous analysis of ethambutol, isoniazid, rifampicin and pyrazinamide in pharmaceutical formulations by capillary zone electrophoresis under UV direct detection with an analysis time of 8.0 min is proposed. Background running was based on the effective mobility curve of the analytes and an optimum separation condition was achieved using a 3(3) Box-Behnken design, with Brij 35, Cu(2+) and acetic acid/sodium acetate buffer as factors. An electrolyte consisting of 50.0 mmol L(-1) of acetic acid/sodium acetate buffer, 12.5 mmol L(-1) of CuSO(4), and standard and sample solutions prepared in 2.00 mmol L(-1) of Brij 35 and 12.5 mmol L(-1) of CuSO(4) were optimized. After evaluating validation parameters, the method was successfully applied to the analysis of samples in the form of tablets and sachets.

Determination of losartan associated with chlorthalidone or hydrochlorothiazide in capsules by capillary zone electrophoresis

An alternative methodology by capillary zone electrophoresis (CZE) is proposed for the determination of losartan potassium (LOS) associated with chlorthalidone (CTD) or hydrochlorothiazide (HCT) in capsules, using 50 mmol L-1 of sodium carbonate buffer with detection at 226 nm. The electrolyte system was optimized, taking into account peak profiles, resolution, run times, baseline stability and repeatability (adsorption absence). The method was successfully applied to the analysis of pharmaceutical formulations purchased in manipulation drugstores. The analytes were baseline separated in less than 5 min. The results did not present significant difference in the 95% confidence interval in relation to the label claim values. The method can be applied to analyze these compounds and could also be employed in other similar formulated products containing these drugs.

Factorial design of electrolyte systems for the separation of fatty acids by capillary electrophoresis.

In this work, a capillary zone electrophoretic methodology using UV indirect detection (224 nm) for the analysis of fatty acids (FAs) in saponified oils is proposed. The electrolyte consisted of a 5 mmol l(-1) phosphate buffer, pH 7. containing 4 mmol l(-1) sodium dodecylbenzenesulfonate (SDBS) as chromophore, 4 mmol l(-1) dimethyl-beta-cyclodextrin and 45% acetonitrile (ACN). The composition of the electrolyte was optimized by a 2(3) factorial design with triplicate at the central point. The design established practical concentration boundaries for SDBS and ACN. In a defined concentration range of 2-4 l(-1), SDBS can certainly be used as a chromophore for indirect detection without imparting excessive baseline noise. For ACN, a suitable interval of 45-55% was found to enhance FAs solubilization without overflowing the system with bubble formation and current interruption. Additionally, the design revealed the importance of dimethyl-beta-cyclodextrin in the resolution of difficult pairs and its function as a solubilizing agent for long chain FAs. At the optimized conditions, nine FAs from C10 to C20, including mono- di- and tri-unsaturated C18 fatty acids were baseline separated in less than 10 min. The proposed method was applied to the separation of FAs in edible oils and polyunsaturated fatty acid enriched margarine. Additionally, spectral monitoring at 206 nm was used to confirm peak identity in the samples.

Validation of a capillary zone electrophoresis method for the determination of ciprofloxacin, gatifloxacin, moxifloxacin and ofloxacin in pharmaceutical formulations

An alternative capillary zone electrophoresis (CZE) method for the determination of ciprofloxacin (CPFLX), gatifloxacin (GTFLX), moxifloxacin (MFLX) and ofloxacin (OFLX) through a simple aqueous electrolyte system consisting of 25 mmol L-1 of TRIS/ hydrochloride and 15 mmol L-1 of sodium tetraborate buffer mixture (pH 8.87) using direct UV detection at 282 nm within 3 min was validated. The analytical parameters of validation evaluated were: linearity (r > 0.998), selectivity (comparison between slope of the calibration curve of external standard and calibration curve of standard addition), repeatability in area for sample (RSD%: < 3.94% for CPFLX, < 3.87% for GTFLX, 1.30% for MFLX and < 1.88% for OFLX), intermediate precision in area for sample (RSD%: < 3.59% for CPFLX, < 3.09% for GTFLX, 2.67% for MFLX and < 2.25% for OFLX), accuracy (mean of recovery range: 101.2% for CPFLX, 101.0% for GTFLX, 101.3% for MFLX and 99.9% for OFLX), limit of detection (mg L-1: 2.72 for CPFLX, 1.92 for GTFLX, 0.795 for MFLX and 1.05 for OFLX), limit of quantification (mg L-1: 9.06 for CPFLX, 6.40 for GTFLX, 2.65 for MFLX and 3.50 for OFLX) and robustness. Due to its simplicity, selectivity, precision, accuracy and rapidity, the methodology can be an interesting alternative for quality assurance in the pharmaceutical industry of these drugs.

Development of a fast capillary electrophoresis method to determine inorganic cations in biodiesel samples.

The aim of this study was to develop a fast capillary electrophoresis method for the determination of inorganic cations (Na(+), K(+), Ca(2+), Mg(2+)) in biodiesel samples, using barium (Ba(2+)) as the internal standard. The running electrolyte was optimized through effective mobility curves in order to select the co-ion and Peakmaster software was used to determine electromigration dispersion and buffer capacity. The optimum background electrolyte was composed of 10 mmol L(-1) imidazole and 40 mmol L(-1) of acetic acid. Separation was conducted in a fused-silica capillary (32 cm total length and 23.5 cm effective length, 50 microm I.D.), with indirect UV detection at 214 nm. The migration time was only 36 s. In order to obtain the optimized conditions for extraction, a fractional factorial experimental design was used. The variables investigated were biodiesel mass, pH, extractant volume, agitation and sonication time. The optimum conditions were: biodiesel mass of 200 mg, extractant volume of 200 microL and agitation of 20 min. The method is characterized by good linearity in the concentration range of 0.5-20 mg kg(-1) (r>0.999), limit of detection was equal to 0.3 mg kg(-1), inter-day precision was equal to 1.88% and recovery in the range of 88.0-120%. The developed method was successfully applied to the determination of cations in biodiesel samples.

Análise de ácidos graxos por eletroforese capilar utilizando detecção condutométrica sem contato

This article describes a novel approach to the separation of fatty acids ranging from 8 to 20 carbons using capillary electrophoresis with contactless conductivity detection. Complete separation of nine linear chain fatty acids (from C8:0 to C20:0) was achieved in 15 min under normal polarity operation. Limits of detection ranged from 35 to 319 µmol L-1 for C20:0 to C8:0, respectively. The optimized running electrolyte composition was 5.0 mmol L-1 phosphate buffer at pH 7, 4.0 mmol L-1 dimethyl-b-cyclodextrin, 2.0 mmol L-1 trimethyl-b-cyclodextrin, acetonitrile 50% (v/v), and methanol 20% (v/v). The applicability of the separation system was demonstrated by the analysis of coconut vegetable oil.

A Rapid Sample Screening Method for Authenticity Control of Whiskey Using Capillary Electrophoresis with Online Preconcentration

The present study aimed to develop a methodology using capillary electrophoresis for the determination of sinapaldehyde, syringaldehyde, coniferaldehyde, and vanillin in whiskey samples. The main objective was to obtain a screening method to differentiate authentic samples from seized samples suspected of being false using the phenolic aldehydes as chemical markers. The optimized background electrolyte was composed of 20 mmol L(-1) sodium tetraborate with 10% MeOH at pH 9.3. The study examined two kinds of sample stacking, using a long-end injection mode: normal sample stacking (NSM) and sample stacking with matrix removal (SWMR). In SWMR, the optimized injection time of the samples was 42 s (SWMR42); at this time, no matrix effects were observed. Values of r were >0.99 for the both methods. The LOD and LOQ were better than 100 and 330 mg mL(-1) for NSM and better than 22 and 73 mg L(-1) for SWMR. The CE-UV reliability in the aldehyde analysis in the real sample was compared statistically with LC-MS/MS methodology, and no significant differences were found, with a 95% confidence interval between the methodologies.

Optimization of an electrolyte system for analysis of ethambutol in pharmaceutical formulations by capillary zone electrophoresis using complexation with copper(II)

An alternative methodology for the determination of ethambutol by capillary zone electrophoresis (CZE) under direct UV detection at 262 nm, using acetic acid/sodium acetate buffer solution (pH 4.6) containing copper(II) sulphate to form the ethambutol-copper(II) complex, within analysis time of 2.5 min is proposed. The optimum CE conditions for the background electrolyte were established performing experiments of a 3(2) factorial design. Complex formation was evidenced by the UV batochromic shift and the [CuETB](0) and [CuETB](2+) chemical structures were indicated by LC-MS analysis. After some validation parameters have been performed, such as linearity (r=0.999), selectivity (comparison between slope of the calibration curve of the external standard and calibration curve of the standard addition), area precision (RSD%: <2.13 for ETB and <1.94 for 2A1B), recovery mean (101.7% for ETB and 99.95% for 2A1B) and quantification limit (mg L(-1): 10.17 for ETB and 19.70 for 2A1B), the method was successfully applied to ETB analysis in pharmaceutical formulation samples. It is possible to determine the presence of the 2A1B impurity at concentrations of less than 1% ETB content.

Simultaneous analysis of aspartame, cyclamate, saccharin and acesulfame-K by CZE under UV detection

An alternative methodology for simultaneous analysis of aspartame (ASP), cyclamate (CYC), saccharin (SAC) and acesulfame-K (ACE) by capillary zone electrophoresis was developed and validated. Optimum separation conditions were achieved by evaluation of the effective mobility curve followed by background electrolyte (BGE) optimization through a full 32 factorial design. The optimized electrolyte composed of 20.0 mmol L−1 sodium tetraborate, 15.0 mmol L−1 Tris and 7.5 mmol L−1 benzoic acid (pH 9.15) was suitable for simultaneous direct (ASP, ACE and SAC) and indirect (CYC) UV detection at 215 nm. Method performance was evaluated for linearity (r > 0.992), precision (RSD%: <4.0%, ASP; <3.0%, CYC; <4.5%, SAC and <4.5%, ACE), accuracy (mean recovery range: 101.2%, ASP; 102.2%, CYC; 91.9%, SAC and 94.4%, ACE), detection limit (expressed in mg L−1: 6.80, ASP; 12.0, CYC; 0.50, SAC and 3.30, ACE) and quantification limit (expressed in mg L−1: 22.0, ASP; 40.0, CYC; 1.60, SAC and 10.0, ACE). Method applicability was demonstrated by analysis of lemon tea sachet samples containing ASP, CYC, SAC and ACE.