Novel Eco-Friendly Stability Indicating Capillary Zone Electrophoresis Method for Determination of Aripiprazole in Tablet Dosage form: DoE Directed Optimization, Development and Method Validation.

In this work, a novel environment-friendly stability indicating capillary zone electrophoresis (CZE) method has been developed and validated for assaying the aripiprazole (ARP) in tablet dosage form. The separation of ARP from its degradation products and internal standard was achieved using a fused silica capillary column (30.2 cm x 75 µm ID), a background electrolyte containing 6 mmol L-1 ammonium formate buffer (pH 3) with 5% methanol under a potential of 15 kV and detection at 214 nm. The stability indicating ability of the method was investigated by analyzing ARP after being subjected to acidic, alkaline, thermal, photolytic, and oxidative stress conditions, according to ICH guidelines. Design of experiments was used during forced degradation and method optimization. Oxidation was the main degradation pathway among those evaluated. The drug was separated from its oxidative degradation products in less than 4 min. CZE method was linear between 60 - 140 µg mL-1, R2 = 0.9980, precise (intra-day 0.88% and inter-day 1.30%). The average recovery was 100.93 ± 0.77%. This is the first method in the literature for quantification of ARP in the presence of its related degradation products with high separation efficiency, low operation cost and minimum solvent consumption. This method could be helpful in the routine quality control analysis in the pharmaceutical industries with least harmful effect on the environment. CZE is considered an eco-friendly alternative of conventionally HPLC methods.

Evaluation of two highly effective lipid-lowering therapies in subjects with acute myocardial infarction.

For cardiovascular disease prevention, statins alone or combined with ezetimibe have been recommended to achieve low-density lipoprotein cholesterol targets, but their effects on other lipids are less reported. This study was designed to examine lipid changes in subjects with ST-segment elevation myocardial infarction (STEMI) after two highly effective lipid-lowering therapies. Twenty patients with STEMI were randomized to be treated with rosuvastatin 20 mg QD or simvastatin 40 mg combined with ezetimibe 10 mg QD for 30 days. Fasting blood samples were collected on the first day (D1) and after 30 days (D30). Lipidomic analysis was performed using the Lipidyzer platform. Similar classic lipid profile was obtained in both groups of lipid-lowering therapies. However, differences with the lipidomic analysis were observed between D30 and D1 for most of the analyzed classes. Differences were noted with lipid-lowering therapies for lipids such as FA, LPC, PC, PE, CE, Cer, and SM, notably in patients treated with rosuvastatin. Correlation studies between classic lipid profiles and lipidomic results showed different information. These findings seem relevant, due to the involvement of these lipid classes in crucial mechanisms of atherosclerosis, and may account for residual cardiovascular risk.Randomized clinical trial: ClinicalTrials.gov, NCT02428374, registered on 28/09/2014.

Improving data quality in liquid chromatography-mass spectrometry metabolomics of human urine.

Signal variation is a common drawback in untargeted metabolomics using liquid chromatography-mass spectrometry (LC-MS), mainly due to the complexity of biological matrices and reduced sample preparation, which results in the accumulation of sample components in the column and the ion source. Here we propose a simple, easy to implement approach to improve data quality in untargeted metabolomics by LC-MS. This approach involves the use of a divert valve to direct the column effluent to waste at the beginning of the chromatographic run and during column cleanup and equilibration, in combination with longer column cleanups in between injections. Our approach was tested using urine samples collected from patients after renal transplantation. Analytical responses were contrasted before and after introducing these modifications by analyzing a batch of untargeted metabolomics data. A significant improvement in peak area repeatability was observed for the quality controls, with relative standard deviations (RSDs) for several metabolites decreasing from ∼60% to ∼10% when our approach was introduced. Similarly, RSDs of peak areas for internal standards improved from ∼40% to ∼10%. Furthermore, calibrant solutions were more consistent after introducing these modifications when comparing peak areas of solutions injected at the beginning and the end of each analytical sequence. Therefore, we recommend the use of a divert valve and extended column cleanup as a powerful strategy to improve data quality in untargeted metabolomics, especially for very complex types of samples where minimum sample preparation is required, such as in this untargeted metabolomics study with urine from renal transplanted patients.

Distinct pattern of one-carbon metabolism, a nutrient-sensitive pathway, in invasive breast cancer: A metabolomic study.

Altered cell metabolism is a hallmark of cancer and critical for its development. Particularly, activation of one-carbon metabolism in tumor cells can sustain oncogenesis while contributing to epigenetic changes and metabolic adaptation during tumor progression. We assessed whether increased one-carbon metabolism activity is a metabolic feature of invasive ductal carcinoma (IDC). Differences in the metabolic profile between biopsies from IDC (n = 47) and its adjacent tissue (n = 43) and between biopsies from different breast cancer subtypes were assessed by gas spectrometry in targeted (Biocrates Life Science ® ) and untargeted approaches, respectively. The metabolomics data were statistically treated using MetaboAnalyst 4.0, SIMCA P+ (version 12.01), Statistica 10 software and t test with p < 0.05. The Cancer Genome Atlas breast cancer dataset was also assessed to validate the metabolomic profile of IDC. Our targeted metabolomics analysis showed distinct metabolomics profiles between IDC and adjacent tissue, where IDC displayed a comparative enrichment of metabolites involved in one-carbon metabolism (serine, glycine, threonine, and methionine) and a predicted increase in the activity of pathways that receive and donate carbon units (i.e., folate, methionine, and homocysteine). In addition, the targeted and untargeted metabolomics analyses showed similar metabolomics profiles between breast cancer subtypes. The gene set enrichment analysis identified different transcription-related functions between IDC and non-tumor tissues that involved one-carbon metabolism. Our data suggest that one-carbon metabolism may be a central pathway in IDC and even in general breast tumors, representing a potential target for its treatment and prevention.

Capillary electrophoresis with dual diode array detection and tandem mass spectrometry to access cardiovascular biomarkers candidates in human urine: Trimethylamine-N-Oxide and l-carnitine.

A capillary electrophoresis with diode array and tandem mass spectrometry detection (CE-UV-MS/MS) method has been developed for the targeted assessment of cardiovascular biomarkers candidates, trimethylamine-N-Oxide (TMAO) and l-carnitine, and creatinine in human urine samples. The dual detection was applied due to the high concentration of creatinine (monitored by UV detection at 200 nm) in relation to TMAO and l-carnitine (quantified by selected reaction monitoring (SRM) mass spectrometry), in human urine. All instrumental parameters, sheath liquid (SHL) and background electrolyte (BGE) compositions were optimized with a pool of urine provided by adult healthy volunteers and evaluated by signal-to-noise ratio (SNR) and peak shape of TMAO. The compositions for the optimized BGE was formic acid at concentration of 0.10 mol L-1, and for SHL was 70:30 MeOH:H2O containing 0.05% (v/v) formic acid, delivered at a flow rate of 5 µL min-1. Limits of detection for TMAO, l-carnitine and creatinine were 0.76, 0.54 and 303 µmol L-1, respectively. Limits of quantification were 2.5, 1.8 and 1000 µmol L-1, respectively. Linearity was evaluated by ANOVA and presented R2 from 0.993 to 0.997. Precision and accuracy were evaluated at three concentration levels. Coefficients of variation (CV) from 1 to 21% were obtained for the intra-day precision evaluation and from 2 to 16% for the inter-day precision evaluation. The recovery ranged from 75 to 116%. Quantitation of TMAO and l-carnitine in infarcted patients urine in comparison to healthy individuals indicated a 2.2 fold increase of TMAO and a 7.0 fold increase of l-carnitine. These results showed the potential applicability of the proposed method for the evaluation of TMAO and l-carnitine in urine within a panel of candidate metabolites in targeted metabolomics studies of cardiovascular diseases among other conditions.

CE-MS for the Analysis of Amino Acids.

Amino acids play an important role in clinical analysis. Capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) has proven to possess several characteristics that make it a powerful and useful tool for the analysis of amino acids in clinical studies. Here we present a method for the separation and quantitative analysis of 27 amino acids in urine based on CE-ESI-MS. The method presents an improved resolution between the isomers Leu, Ile, and aIle, in comparison to other CE-ESI-MS methods in the literature. This method is fast, selective, and simple and has improved sensitivity by applying a pH-mediated stacking strategy, showing that it can be successfully used for amino acid analysis and probably for other small cationic metabolites.

Metabolomics: Definitions and Significance in Systems Biology.

Nowadays, there is a growing interest in deeply understanding biological mechanisms not only at the molecular level (biological components) but also the effects of an ongoing biological process in the organism as a whole (biological functionality), as established by the concept of systems biology. Within this context, metabolomics is one of the most powerful bioanalytical strategies that allow obtaining a picture of the metabolites of an organism in the course of a biological process, being considered as a phenotyping tool. Briefly, metabolomics approach consists in identifying and determining the set of metabolites (or specific metabolites) in biological samples (tissues, cells, fluids, or organisms) under normal conditions in comparison with altered states promoted by disease, drug treatment, dietary intervention, or environmental modulation. The aim of this chapter is to review the fundamentals and definitions used in the metabolomics field, as well as to emphasize its importance in systems biology and clinical studies.

Strategies Involving Mass Spectrometry Combined with Capillary Electrophoresis in Metabolomics.

This chapter focuses on the important contribution of CE-MS in metabolomics, describing the nature of CE-MS coupling and the technical improvements that have led to the interfaces used in modern instrumentation. Moreover, it will discourse how the variety of electrolyte compositions and additives, which has conferred CE the exceptional selectivity of its multiple separation modes, has been handled to allow interfacing with MS without compromising ionization efficiency and the spectrometer integrity. Finally, the methodologies of CE-MS in current use for metabolomics will be discussed in detail. To verify the scope of CE-MS in clinical metabolomics, a myriad of representative applications has been compiled.

Down regulation of NO signaling in Trypanosoma cruzi upon parasite-extracellular matrix interaction: changes in protein modification by nitrosylation and nitration.

BACKGROUND: Adhesion of the Trypanosoma cruzi trypomastigotes, the causative agent of Chagas' disease in humans, to components of the extracellular matrix (ECM) is an important step in host cell invasion. The signaling events triggered in the parasite upon binding to ECM are less explored and, to our knowledge, there is no data available regarding •NO signaling. METHODOLOGY/PRINCIPAL FINDINGS: Trypomastigotes were incubated with ECM for different periods of time. Nitrated and S-nitrosylated proteins were analyzed by Western blotting using anti-nitrotyrosine and S-nitrosyl cysteine antibodies. At 2 h incubation time, a decrease in NO synthase activity, •NO, citrulline, arginine and cGMP concentrations, as well as the protein modifications levels have been observed in the parasite. The modified proteins were enriched by immunoprecipitation with anti-nitrotyrosine antibodies (nitrated proteins) or by the biotin switch method (S-nitrosylated proteins) and identified by MS/MS. The presence of both modifications was confirmed in proteins of interest by immunoblotting or immunoprecipitation. CONCLUSIONS/SIGNIFICANCE: For the first time it was shown that T. cruzi proteins are amenable to modifications by S-nitrosylation and nitration. When T. cruzi trypomastigotes are incubated with the extracellular matrix there is a general down regulation of these reactions, including a decrease in both NOS activity and cGMP concentration. Notwithstanding, some specific proteins, such as enolase or histones had, at least, their nitration levels increased. This suggests that post-translational modifications of T. cruzi proteins are not only a reflex of NOS activity, implying other mechanisms that circumvent a relatively low synthesis of •NO. In conclusion, the extracellular matrix, a cell surrounding layer of macromolecules that have to be trespassed by the parasite in order to be internalized into host cells, contributes to the modification of •NO signaling in the parasite, probably an essential move for the ensuing invasion step.

Development of a method for the analysis of drugs of abuse in vitreous humor by capillary electrophoresis with diode array detection (CE-DAD).

This work presents the development of an analytical method based on capillary electrophoresis with diode array detection for the analysis of drugs of abuse and biotransformation products in vitreous humor. Composition of the background electrolyte, implementation of an online pre-concentration strategy and sample preparation procedures were objects of study. The complete electrophoretic separation of 12 analytes (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), ketamine, cocaine, cocaethylene, lidocaine, morphine, 6-monoacetylmorphine and heroin) and the internal standard N-methyl-1-(3,4-methylenedioxyphenyl)-2-butamine (MBDB) was obtained within 13min of run. The method was validated presenting good linearity (r(2)>0.99), recovery ≥90%, precision better than 12% RSD and acceptable accuracy in the range of 86-118% at three concentration levels (50, 100 and 500ng/mL). LODs and LOQs in the order of 1-5ng/mL and 5-10ng/mL, respectively, were obtained. After validation, the method was applied to eighty-seven vitreous humor samples and the results were compared to those obtained by a liquid chromatography tandem mass spectrometry (LC-MS/MS) screening method, routinely used by the forensic toxicology laboratory of the Sao Paulo State Police, Brazil. Cocaine was detected in 7.1%, cocaethylene in 3.6%, lidocaine in 2.4% and ketamine in 1.2% of the total number of analyzed samples.

Anxiety-like effects of meta-chlorophenylpiperazine in paradoxically sleep-deprived mice.

Chlorophenylpiperazines (CPP) are psychotropic drugs used in nightclub parties and are frequently used in a state of sleep deprivation, a condition which can potentiate the effects of psychoactive drugs. This study aimed to investigate the effects of sleep deprivation and sleep rebound (RB) on anxiety-like measures in mCPP-treated mice using the open field test. We first optimized our procedure by performing dose-effect curves and examining different pretreatment times in naïve male Swiss mice. Subsequently, a separate cohort of mice underwent paradoxical sleep deprivation (PSD) for 24 or 48h. In the last experiment, immediately after the 24h-PSD period, mice received an injection of saline or mCPP, but their general activity was quantified in the open field only after the RB period (24 or 48h). The dose of 5mgmL(-1) of mCPP was the most effective at decreasing rearing behavior, with peak effects 15min after injection. PSD decreased locomotion and rearing behaviors, thereby inhibiting a further impairment induced by mCPP. Plasma concentrations of mCPP were significantly higher in PSD 48h animals compared to the non-PSD control group. Twenty-four hours of RB combined with mCPP administration produced a slight reduction in locomotion. Our results show that mCPP was able to significantly change the behavior of naïve, PSD, and RB mice. When combined with sleep deprivation, there was a higher availability of drug in plasma levels. Taken together, our results suggest that sleep loss can enhance the behavioral effects of the potent psychoactive drug, mCPP, even after a period of rebound sleep.

Characterization of protein hydrolysates of cosmetic use by CE-MS.

Protein hydrolysates have been used as active principles in cosmetic products conferring different properties to the final formulations, which are mostly controlled by the peptide size and its amino acid sequence. In this work, capillary electrophoresis coupled to mass spectrometry analyses were carried out in order to investigate such characteristics of protein hydrolysates. Samples of different origins (milk, soy and rice) were obtained from a local company, and were analyzed without a previous preparation step. The background electrolyte (BGE) and sheath liquid compositions were optimized for each sample. The best BGE composition (860 mmol/L formic acid--pH 1.8--in 70:30 v/v water/methanol hydro-organic solvent) was chosen based on the overall peak resolution whereas the best sheath liquid was selected based on increased sensitivity and presented different compositions to each sample (10.9-217 mmol/L formic acid in 75:25-25:75 v/v water/methanol hydro-organic solvent). Most of the putative peptides in the hydrolysate samples under investigation presented molecular masses of 1000 Da or less. De novo sequencing was carried out for some of the analytes, revealing the hydrophobicity/polarity of the peptides. Hence, the technique has proved to be an advantageous tool for the quality control of industrial protein hydrolysates.

Acetyl radical production by the methylglyoxal-peroxynitrite system: a possible route for L-lysine acetylation.

Methylglyoxal is an α-oxoaldehyde putatively produced in excess from triose phosphates, aminoacetone, and acetone in some disorders, particularly in diabetes. Here, we investigate the nucleophilic addition of ONOO(-), known as a potent oxidant and nucleophile, to methylglyoxal, yielding an acetyl radical intermediate and ultimately formate and acetate ions. The rate of ONOO(-) decay in the presence of methylglyoxal [k(2,app) = (1.0 ± 0.1) × 10(3) M(-1) s(-1); k(2) ≈ 1.0 × 10(5) M(-1) s(-1)] at pH 7.2 and 25 °C was found to be faster than that reported with monocarbonyl substrates (k(2) < 10(3) M(-1) s(-1)), diacetyl (k(2) = 1.0 × 10(4) M(-1) s(-1)), or CO(2) (k(2) = 3-6 × 10(4) M(-1) s(-1)). The pH profile of the methylglyoxal-peroxynitrite reaction describes an ascendant curve with an inflection around pH 7.2, which roughly coincides with the pK(a) values of both ONOOH and H(2)PO(4)(-) ion. Electron paramagnetic resonance spin trapping experiments with 2-methyl-2-nitrosopropane revealed concentration-dependent formation of an adduct that can be attributed to 2-methyl-2-nitrosopropane-CH(3)CO(•) (a(N) = 0.83 mT). Spin trapping with 3,5-dibromo-4-nitrosobenzene sulfonate gave a signal that could be assigned to a methyl radical adduct [a(N) = 1.41 mT; a(H) = 1.35 mT; a(H(m)) = 0.08 mT]. The 2-methyl-2-nitrosopropane-CH(3)CO(•) adduct could also be observed by replacement of ONOO(-) with H(2)O(2), although at much lower yields. Acetyl radicals could be also trapped by added L-lysine as indicated by the presence of (ε)N-acetyl-L-lysine in the spent reaction mixture. This raises the hypothesis that ONOO(-)/H(2)O(2) in the presence of methylglyoxal is endowed with the potential to acetylate proteins in post-translational processes.

Simple method for determination of cocaine and main metabolites in urine by CE coupled to MS.

In this work, a simple method for the simultaneous determination of cocaine (COC) and five COC metabolites (benzoylecgonine, cocaethylene (CET), anhydroecgonine, anhydroecgonine methyl ester and ecgonine methyl ester) in human urine using CE coupled to MS via electrospray ionization (CE-ESI-MS) was developed and validated. Formic acid at 1 mol/L concentration was used as electrolyte whereas formic acid at 0.05 mol/L concentration in 1:1 methanol:water composed the coaxial sheath liquid at the ESI nozzle. The developed method presented good linearity in the dynamic range from 250 ng/mL to 5000 ng/mL (coefficient of determination greater than 0.98 for all compounds). LODs (signal-to-noise ratio of 3) were 100 ng/mL for COC and CET and 250 ng/mL for the other studied metabolites whereas LOQ's (signal-to-noise ratio of 10) were 250 ng/mL for COC and CET and 500 ng/mL for all other compounds. Intra-day precision and recovery tests estimated at three different concentration levels (500, 1500 and 5000 ng/mL) provided RSD lower than 10% (except anhydroecgonine, 18% RSD) and recoveries from 83-109% for all analytes. The method was successfully applied to real cases. For the positive urine samples, the presence of COC and its metabolites was further confirmed by MS/MS experiments.

Determination of amino acids by capillary electrophoresis-electrospray ionization-mass spectrometry: an evaluation of different protein hydrolysis procedures.

In this work, a CE equipment, online hyphenated to an IT MS analyzer by a linear sheath liquid interface promoting ESI, was used to develop a method for quantitative determination of amino acids. Under appropriate conditions (BGE composition, 0.8% HCOOH, 20% CH3OH; sheath liquid composition, 0.8% HCOOH, 60% methanol; V ESI, +4.50 kV), analytical curves of all amino acids from 3 to 80 mg/L were recorded presenting acceptable linearity (r >0.99). LODs in the range of 16-172 micromol/L were obtained. BSA, a model protein, was submitted to different hydrolysis procedures (classical acid and basic, and catalyzed by the H+ form of a cation exchanger resin) and its amino acid profiles determined. In general, the resin-mediated hydrolysis yields were overall similar or better than those obtained by classical acid or basic hydrolysis. The resulting experimental-to-theoretical BSA concentration ratios served as correction factors for the quantitation of amino acids in Brazil nut resin generated hydrolysates.

Development and validation of a method for quantitative determination of econazole nitrate in cream formulation by capillary zone electrophoresis.

A simple, fast, inexpensive and reliable capillary zone electrophoresis (CZE) method for the determination of econazole nitrate in cream formulations has been developed and validated. Optimum conditions comprised a pH 2.5 phosphate buffer at 20 mmol L(-1) concentration, +30 kV applied voltage in a 31.5 cm x 50 microm I.D. capillary. Direct UV detection at 200 nm led to an adequate sensitivity without interference from sample excipients. A single extraction step of the cream sample in hydrochloric acid was performed prior to injection. Imidazole (100 microg mL(-1)) was used as internal standard. Econazole nitrate migrates in approximately 1.2 min. The analytical curve presented a coefficient of correlation of 0.9995. Detection and quantitation limits were 1.85 and 5.62 microg mL(-1), respectively. Excellent accuracy and precision were obtained. Recoveries varied from 98.1 to 102.5% and intra- and inter-day precisions, calculated as relative standard deviation (RSD), were better than 2.0%. The proposed CZE method presented advantageous performance characteristics and it can be considered suitable for the quality control of econazole nitrate cream formulations.

Chemical identification of 2,5-dimethoxy-4-bromoamphetamine (DOB).

The consumption of synthetic drugs, generally known as designer drugs, has increased drastically in all parts of the world. Typical constituents of designer synthetic drugs are chemical substances derived from amphetamine but significant differences in effects caused and duration may result. In May, 2005, the civil state police of Sao Paulo seized thirty-one gelatinous capsules containing a very small quantity of a white powder inside (approximately 1.5 mg per capsule). This paper describes the analytical assays that were used to identify the seized material. Preliminary assays using colorimetric tests and high performance thin-layer chromatography indicated that the capsules content could be an amphetamine derivative. In the capillary zone electrophoresis assay, it was possible to observe that the analyzed material had basic characteristics. Mass spectrometry analysis revealed that the compound had the same molecular mass as 2,5-dimethoxy-4-bromoamphetamine (DOB) and its identity was confirmed through collision-induced dissociation (CID) experiments. Finally, the comparison of infrared sample spectrum with a spectra library provided further evidence of the DOB presence in the seized material. Although a reference standard material was not available, the information gathered from the different assays allowed the conclusion that the substance was, in fact, DOB, a substance with a powerful hallucinogenic action of proscribed use in the country and which was seized and identified for the first time in Brazil.

Method development and validation for isoflavones in soy germ pharmaceutical capsules using micellar electrokinetic chromatography.

The separation of six soy isoflavones (Glycitein, Daidzein, Genistein, Daidzin, Glycitin and Genistin) was approached by a 3(2) factorial design studying MEKC electrolyte components at the following levels: methanol (MeOH; 0-10%) and sodium dodecylsulfate (SDS; 20-70 mmol L(-1)); sodium tetraborate buffer (STB) concentration was kept constant at 10 mmol L(-1). Nine experiments were performed and the apparent mobility of each isoflavone was computed as a function of the electrolyte composition. A novel response function (RF) was formulated based on the production of the mobility differences, mobility of the first and last eluting peaks and the electrolyte conductance. The inspection of the response surface indicated an optimum electrolyte composition as 10 mmol L(-1) STB (pH 9.3) containing 40 mmol L(-1) SDS and 1% MeOH promoting baseline separation of all isoflavones in less than 7.5 min. The proposed method was applied to the determination of total isoflavones in soy germ capsules from four different pharmaceutical laboratories. A 2h extraction procedure with 80% (v/v) MeOH under vortexing at room temperature was employed. Peak assignment of unknown isoflavones in certain samples was assisted by hydrolysis procedures, migration behavior and UV spectra comparison. Three malonyl isoflavone derivatives were tentatively assigned. A few figures of merit for the proposed method include: repeatability (n=6) better than 0.30% CV (migration time) and 1.7% CV (peak area); intermediate precision (n=18) better than 6.2% CV (concentration); recoveries at two concentration levels, 20 and 50 microg mL(-1), varied from 99.1 to 103.6%. Furthermore, the proposed method exhibited linearity in the concentration range of 1.6-50 microg mL(-1) (r(2)>0.9999) with LOQ varying from 0.67 to 1.2 microg mL(-1). The capsules purity varied from 93.3 to 97.6%.

Determination of alpha-hydroxy acids in cosmetic products by capillary electrophoresis.

In this work, a simple and reliable method for the simultaneous analysis of alpha-hydroxy acids such as tartaric, glycolic and lactic acids in cosmetic products was developed using capillary electrophoresis with indirect UV detection at 254 nm. A buffer solution containing 10 mmoll(-1) potassium phthalate (pH 4.1) and 0.5 mmoll(-1) cetyltrimethylammonium bromide as electroosmotic flow modifier allowed baseline resolution of the analytes in approximately 3 min. A few validation parameters of the proposed method include: good linearity for all compounds in the range from 10 to 100 mgl(-1) with coefficients of correlation larger than 0.9999. The average recoveries of tartaric, glycolic and lactic acids in commercial samples were 99.12, 99.41 and 99.43%, respectively. The method presented acceptable precision with average relative standard deviation of 0.54% (assay of commercial samples), 0.44% (peak area) and 0.16% (migration time).

Optimizing the separation of food dyes by capillary electrophoresis.

In this work, the separation of eleven food dyes was evaluated by MEKC in electrolytes composed of tetraborate (TBS), Brij 35, and acetonitrile (ACN) using a factorial design at the following levels: TBS concentration (5 and 10 mmol L(-1)), pH (9.5 and 10.1), Brij concentration (5 and 20 mmol L(-1)), and ACN (5 and 15%). Several response functions were evaluated and indicated 10 mmol L(-1) TBS (pH 10.1), 15% ACN, and 20 mmol L(-1) Brij 35 as best values. However, baseline resolution was not achieved (R(cp) = 0.76) and the method lacked robustness. New conditions were sought by studying the dye mobility versus Brij concentration (5-20 mmol L(-1)). A set of well resolved and more uniformly spaced peaks was obtained with an electrolyte consisting of 7.5 mmol L(-1) TBS (pH 10.1), 10 mmol L(-1) Brij, and 15% ACN. Under these new conditions, complete resolution of the 11 dyes was achieved in less than 9 min. Migration time and peak area repeatabilities were better than 1.6% and 5% CV and the LODs were 0.47 to 2.3 microg mL(-1). The methodology was applied to fruit juice powders, lollipops, and other hard and soft chewable treats.