Separation and determination of basic dyes formulated in hair care products by capillary electrophoresis

Assessment of semi-permanent hair dyes in wash water from beauty salons by liquid chromatography-tandem mass spectrometry-selected reaction monitoring (LC-MS/MS-SRM)

Herein, we present an approach for the analytical determination and quantification of semi-permanent hair dyes in wash water samples released during washing of dyed hair employing a liquid chromatography-tandem mass spectrometry-selected reaction monitoring (LC-MS/MS-SRM) method with electrospray ionization detection. Specifically, Basic Blue 99 (BB 99), Basic Brown 16 (BB 16), Basic Red 76 (BR 76), Basic Yellow 57 (BY 57) and Acid Violet 43 (AV 43) are hair dyes with properties known to be harmful to human health and the environment. The hair dyes are present in commercial formulation and are discharged into the effluents without fully effective treatment. The detection and quantification by the LC-MS/MS technique show a linear relationship for each studied hair dye in the concentration range from 1 to 200 ng mL^-1 in aqueous solution. The limits of detection and quantification were found from 0.66 to 20 ng mL^-1 and from 2.0 to 63 ng mL^-1, respectively, values that are compatible with the level required in wash water analysis. The method was applied in samples collected from 5 successive washings of hair dyed with a commercial formulation using the established procedure. BB 99 and BY 57 dyes have lower fixation on the scalp and hair, showing 866 ng mL^-1 and 145 ng mL^-1 release on the first day of washing, respectively. The accumulation of dye and slow release after washing can lead to future problems for both the environment and living organisms.

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.

CE of tricyclic antidepressant clomipramine and metabolites: Electromigration and wall adsorption

CE of tricyclic antidepressants clomipramine and its metabolites demethylclomipramine, didemethylclomipramine and 8-hydroxyclomipramine resulted in partly extremely tailing peaks in bare fused-silica capillaries. Especially at high pH of the BGE this behavior was not unexpected as adsorption of the cationic analytes onto the negatively charged wall due to electrostatic attraction can be supposed. Less expected was the observation that peak tailing could not be overcome neither by using a capillary with dynamic coating with cationic CTAB added to the BGE, nor by the usage of a capillary permanently coated with polyvinyl alcohol (PVA), both operated at acidic pH. As this tailing was even more pronounced than with bare fused silica, and was suppressed upon addition of MeCN to the BGE, another source of adsorption than pure ion-ion interaction seems plausible. In the bare silica capillary the mobility, mu, of the analytes followed roughly the pH dependence of a monoacidic base, but two deviations from the sigmoid theoretical curve were evident: (i) even at low pH the mobilities were not constant; they decreased in contrary with pH over the entire range; (ii) the apparent pK(a) values of two analytes, derived at the pH with halve the mobility at low pH, are significantly smaller than the thermodynamic pK(a). Upon modifying the expression for mu = f(pH), and considering the pH dependence of the negative charge density at the wall by an additional term which takes chromatographic retention into account, an equation was derived which enables the description of the observed electromigration of the analytes as function of pH, pK(a) of analytes and surface silanol groups, actual mobility of analytes, distribution coefficient (or retention factor) due to adsorption including its pH dependence. The interplay of electrophoretic movement and residual adsorptive retention allowed to resolve the analytes finally in an uncoated capillary, namely at pH 7.65 (30 mM ionic strength), whereas at the cost of the robustness of the separation system.