Quantitative analysis of synthetic dyes in lipstick by micellar electrokinetic capillary chromatography

Applicability of a graphene oxide nanocomposite for fabrication of an electrochemical sensor for simultaneous detection of sunset yellow and rhodamine B in food samples

Developing a sensitive portable sensor for the determination of food additives is very important. Herein, a simple and sensitive electrochemical sensor has been constructed based on a carbon paste electrode (CPE) modified with graphene oxide (GO) nanosheets for the simultaneous determination of sunset yellow (SY) and rhodamine B (RhB) in phosphate buffer solution (pH = 4). The cyclic and differential pulse voltammetry (CV and DPV) results revealed two well-resolved anodic peaks for SY and RhB with a remarkable increase in oxidation signals of these colorants. Based on this, an electrochemical method was developed for the first time for the simultaneous detection of SY and RhB. Applicability of the sensor was confirmed in various concentrations of two analytes in two linear ranges of 1-20 μM for SY and 1-30 μM for RhB with a limit of detection (LOD) of 10.0 nM and 20.0 nM, respectively. Furthermore, the proposed sensor was successfully employed for the simultaneous detection of SY and RhB in food samples with recoveries of 93.1-106.0% indicating promising potential in practical application.

Zwitterionic surfactant as an additive for efficient electrophoretic separation of easily absorbed rhodamine dyes on plastic microchips

Plastic microchips possess the advantages of easy fabrication and low-cost, but their surface properties are frequently incompatible with electrophoretic separation without proper surface modification. Meanwhile, the separation microchannels on typical microchips are usually only a few centimeters long, the pressurized flow may significantly affect the electrophoretic separation if their inner diameters (id) are relatively larger (approximately > 50 μm), viscous separation medium is therefore required for efficient separation. Herein, a zwitterionic surfactant, N-hexadecyl-N,N-dimethyl-3-ammonio-1-propane sulfonate (HDAPS), was used as a multifunctional additive to inhibit the analyte adsorption, improve the surface status, control Joule heating and modulate the resolution on cyclic olefin copolymer microchips with 80 μm id, 5 cm long separation microchannels, eliminating the necessity of viscous polymeric additives. The effectiveness of HDAPS was compared with an ionic polymeric additive, poly(diallydimethylammonium chloride). The streaming potential and electroosmotic flow measurements indicated an effective inhibition of the adsorption of rhodamine B and a stable negative surface charge with zwitterionic HDAPS. Using 15 mmol/L HDAPS, 40% (v/v) methanol, and 10 mmol/L boric acid (pH 3.2) as the running buffer, rapid separation of four rhodamines was achieved within 90 s under a separation electric field of 520 V/cm. The theoretical plate numbers were in a range of 5.0×10⁵-6.9×10⁵/m. The relative standard deviations were no more than 0.9% for retention time and 1.5% for peak area. The proposed system was verified by the determination of rhodamines in eyeshadow and wolfberry, with standard recoveries in a range of 98.2%-101.4%.

Analysis of Prohibited and Restricted Ingredients in Cosmetics

The general public uses cosmetics daily. Cosmetic products contain substances (ingredients) with various functions, from skincare to enhancing appearance, as well as ingredients that preserve the cosmetic products. Some cosmetic ingredients are prohibited or restricted in certain geographical regions, such as the European Union and the United States of America, due to their potential to cause adverse effects such as cancer, birth defects, and/or developmental and reproductive disorders. However, the ingredients may be used in other regions, and, hence, the monitoring of the cosmetic ingredients actually used is important to ensure the safety of cosmetic products. This review provides an overview of recent analytical methods that have been developed for detecting certain ingredients that are restricted or prohibited by the U.S. Food and Drug Administration (FDA) and/or EU legislation on cosmetic products.

A multitechnique approach for discrimination and identification of lipsticks for forensic purposes

Cosmetics are becoming more and more popular; consequently, the chance of finding them as microtraces at a crime scene increases. They are easily transferable and can provide a link between a suspect and a victim. For this reason, identifying and comparative analysis of red lipstick - the most popular and used - is required. The aim of this study was to apply a multitechnique methodology for the comparative forensic analysis of the red lipsticks traces of a very similar hue. For this purpose, four methods of different physicochemical basics - two nondestructive spectroscopic and two destructive separation techniques - were used. The possibilities and advantages of attenuated total reflection infrared spectroscopy (ATR-FTIR), confocal Raman microscopy (CRM), capillary electrophoresis (MEKC) and gas chromatography-mass spectrometry (GC-MS) have been combined. Specially prepared lipstick traces in various forms (imprints, smears) on different surfaces (absorbent and nonabsorbent) were analyzed to confirm the usefulness of the proposed methods. The premise is that if two methods yield a consistent result, the investigation is terminated at this stage. All investigated traces were properly identified. First, the ATR-FTIR method as a nondestructive technique is recommended. Sometimes, due to strong interferences from the substrates, the newly proposed method with the use of confocal Raman microscopy may be an alternative. The next recommendation is the MEKC method. Only in case of the absence of unambiguous conclusions, it is proposed to use the GC-MS method. This methodology has the potential to be applied in the comparative analysis of red lipsticks for forensic purposes.

Application of micellar electrokinetic capillary chromatography to the discrimination of red lipstick samples

The main aim of this study was to apply capillary electrophoresis (CE) to the discrimination of red lipsticks - the first step towards developing the methodology for forensic purposes. The separation method was optimized using a mixture of eight dyes and micellar electrokinetic capillary chromatography (MEKC). The influence of the buffer pH and the concentration of SDS on the separation of dye mixtures was investigated. The best separation (highly efficient with the large resolution capacity in relatively short time) was accomplished using a buffer at pH 9 enriched with 80 mM SDS. The developed separation method was evaluated, determining the stability of sample (5 h) and buffer (10 h), the limit of detection of dyes (LOD < 1 μg·mL^-1), the repeatability of migration times in one day (RSD < 1.2%), and over three days (RSD < 2.4%), as well as the reproducibility using different capillaries and CE instruments. In order to develop a versatile extraction method for compounds from red lipsticks, various types of solvents, temperatures and durations of ultrasound assisted extraction (UAE) were tested. The use of a specially designed and constructed device for repetitive sampling without contamination was suggested. The extraction method was characterized in terms of precision, obtaining very good results for the qualitative (RSD of migration time < 2.0%) and quantitative (RSD of peak height < 10.0%) methods. The proposed UAE/MEKC-DAD method was successfully applied to distinguish red lipstick samples with a very similar hue, achieving a high value of discrimination power (DP = 0.998). It was found that it has great potential in forensic investigations.

A simple solvent extraction and ultra-performance liquid chromatography-tandem mass spectrometric method for the identification and quantification of rhodamine B in commercial lip balm samples

Rhodamine B is a synthetic dye used in many industries including cosmetics. Long-term contact may results neurotoxicity, genotoxicity and cancer. In the present work, a simple solvent extraction followed by rapid, sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometric method has been proposed for the identification and quantification of rhodamine B in lip balm samples for the first time to our knowledge. The best extraction was achieved using organic solvent n-hexane followed by sonication, centrifugation and evaporation. The chromatographic separation was attained in <1 min with Acquity™ BEH C₁₈ reversed phase column and a tandem mass spectrometer. The limit of detection (LOD), limit of quantification (LOQ), linearity, precisions and accuracy of the proposed method were determined. The LOD and LOQ were found to be 0.1 μg/kg and 0.4 μg/kg, respectively. The linearity (R²) was obtained (>0.999) when analyzing low to higher range of concentrations. The precisions with relative standard deviation (RSD%) values in terms of repeatability (<2%, n = 5) and reproducibility (<3%, n = 5) were achieved. The accuracy in terms of recovery was obtained between 93% and 98%. The optimized procedures have been applied for the identification and quantification of rhodamine B in commercial lip balm samples from various brands and origin, and the amounts were obtained from not detected to 70.44 μg/kg. The good quality conditions, negligible matrix influence and higher recovery values obtained throughout analysis have proved the suitability of the present method for the routine analysis of rhodamine B in lip balm samples. The achieved results could be used to approximate the application of rhodamine B from individuals either from Saudi Arabia or globally, and thus to improve the quality and safety of lip balm products.

Design of GO–Ag-functionalized Fe3O4@CS composite for magnetic adsorption of rhodamine B

In this study, a novel magnetic composite (Fe₃O₄@CS/GO/Ag) modified with chitosan (CS), graphene oxide (GO) and Ag nanoparticles (Ag NPs) was successfully prepared as an efficient adsorbent for detection of rhodamine B (RB) combined with a fluorescence technique. The properties of the magnetic composite were confirmed by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometry. The components of Fe₃O₄@CS/GO/Ag endowed it with excellent extraction performance and convenient operation. The main parameters affecting extraction and desorption efficiency were all investigated systematically. Under the optimized experimental conditions, the proposed method showed linear ranges (0.2–6.0 μg L⁻¹) with R² = 0.9992. The limits of detection (LODs) and quantification (LOQs) were 0.05 and 0.2 μg L⁻¹ (n = 3), respectively. Fe₃O₄@CS/GO/Ag exhibited outstanding extraction efficiency for RB, compared with CS-coated Fe₃O₄ nanoparticles (Fe₃O₄@CS) and GO-modified Fe₃O₄@CS (Fe₃O₄@CS/GO). The applicability of the proposed method was investigated by analyzing four real samples (waste water, soft drink, shampoo, and red pencil) and the spiked recoveries ranged between 94% and 97% with RSD ranging from 3% to 6%, which showed that the proposed method had satisfactory practicability and operability.

A novel magnetic composite modified with chitosan, graphene oxide and Ag nanoparticles, was successfully prepared as an efficient adsorbent for detection of rhodamine B combining with fluorescence technique.

Rapid, simultaneous and interference-free determination of three rhodamine dyes illegally added into chilli samples using excitation-emission matrix fluorescence coupled with second-order calibration method

In this study, a smart and green analytical method based on the second-order calibration algorithm coupled with excitation-emission matrix (EEM) fluorescence was developed for the determination of rhodamine dyes illegally added into chilli samples. The proposed method not only has the advantage of high sensitivity over the traditional fluorescence method but also fully displays the "second-order advantage". Pure signals of analytes were successfully extracted from severely interferential EEMs profiles via using alternating trilinear decomposition (ATLD) algorithm even in the presence of common fluorescence problems such as scattering, peak overlaps and unknown interferences. It is worth noting that the unknown interferents can denote different kinds of backgrounds, not only refer to a constant background. In addition, the method using interpolation method could avoid the information loss of analytes of interest. The use of "mathematical separation" instead of complicated "chemical or physical separation" strategy can be more effective and environmentally friendly. A series of statistical parameters including figures of merit and RSDs of intra- (≤1.9%) and inter-day (≤6.6%) were calculated to validate the accuracy of the proposed method. Furthermore, the authoritative method of HPLC-FLD was adopted to verify the qualitative and quantitative results of the proposed method. Compared with the two methods, it also showed that the ATLD-EEMs method has the advantages of accuracy, rapidness, simplicity and green, which is expected to be developed as an attractive alternative method for simultaneous and interference-free determination of rhodamine dyes illegally added into complex matrices.

Magnetic solid phase extraction using ionic liquid-coated core-shell magnetic nanoparticles followed by high-performance liquid chromatography for determination of Rhodamine B in food samples

Three hydrophobic ionic liquids (ILs) (1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluoro-phosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluorophosphate ([OMIM]PF6)) were used to coat Fe3O4@SiO2 nanoparticles (NPs) with core-shell structures to prepare magnetic solid phase extraction (MSPE) agents (Fe3O4@SiO2@IL). A novel method of MSPE coupled with high-performance liquid chromatography for the separation/analysis of Rhodamine B was then established. The results showed that Rhodamine B was adsorbed rapidly on Fe3O4@SiO2@[OMIM]PF6 and was released using ethanol. Under optimal conditions, the pre-concentration factor for the proposed method was 25. The linear range, limit of detection (LOD), correlation coefficient (R), and relative standard deviation (RSD) were found to be 0.50-150.00 μgL(-1), 0.08 μgL(-1), 0.9999, and 0.51% (n=3, c=10.00 μgL(-1)), respectively. The Fe3O4@SiO2 NPs could be re-used up to 10 times. The method was successfully applied to the determination of Rhodamine B in food samples.

Development of a rapid, simple and sensitive HPLC-FLD method for determination of rhodamine B in chili-containing products

In this work, a simple, rapid and sensitive analytical method for the determination of rhodamine B in chili-containing foodstuffs is described. The dye is extracted from samples with methanol and analysed without further cleanup procedure by high-performance liquid chromatography (HPLC) coupled to fluorescence detection (FLD). The influence of matrix fluorescent compounds (capsaicin and dihydrocapsaicin) on the analysis was overcome by the optimisation of mobile-phase composition. The limit of determination (LOD) and limit of quantification (LOQ) were 3.7 and 10 μg/kg, respectively. Validation data show a good repeatability and within-lab reproducibility with relative standard deviations <10%. The overall recoveries are in the range of 98-103% in chili powder and in the range of 87-100% in chili oil depending on the concentration of rhodamine B in foodstuffs. This method is suitable for the routine analysis of rhodamine B due to its sensitivity, simplicity, reasonable time and cost.

Degradation of dyes from aqueous solution by Fenton processes: a review

Several industries are using dyes as coloring agents. The effluents from these industries are increasingly becoming an environmental problem. The removal of dyes from aqueous solution has a great potential in the field of environmental engineering. This paper reviews the classification, characteristics, and problems of dyes in detail. Advantages and disadvantages of different methods used for dye removal are also analyzed. Among these methods, Fenton process-based advanced oxidation processes are an emerging prospect in the field of dye removal. Fenton processes have been classified and represented as "Fenton circle". This paper analyzes the recent studies on Fenton processes. The studies include analyzing different configurations of reactors used for dye removal, its efficiency, and the effects of various operating parameters such as pH, catalyst concentration, H2O2 concentration, initial dye concentration, and temperature of Fenton processes. From the present study, it can be conclude that Fenton processes are very effective and environmentally friendly methods for dye removal.

Discovery of environmental rhodamine B contamination in paprika during the vegetation process

Recently, rhodamine B (RhB) in paprika and chilli has attracted much attention. Almost all the literature has deemed that the detectable RhB was attributed to malicious intents in the fabrication process. However, the occurrence of increasing cases with ultratrace levels of RhB was difficult to understand on the basis of that statement. Here, we report on the discovery of environmental RhB contamination in paprika during its vegetation process. Samples including paprika, soils, and stems collected from seven fields in the Xinjiang Region, China, were detected by ultraperformance liquid chromatography-tandem mass spectrometry. Far from any anthropogenic addition, the ultratrace RhB concentrations in all the paprika samples provided unambiguous evidence that environmental RhB contamination in paprika had really occurred over its growth period. Further illation suggests that the soil contaminated by RhB is one of the major contamination sources and that there may be a degradation of RhB in paprika during the late maturation stage. The discovery has significant implications for re-evaluating the origin of the RhB in paprika- and chilli-containing products.

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.

Adsorption of a hazardous dye, erythrosine, over hen feathers

Erythrosine is a popular dye that is widely used in cosmetics, foodstuffs, medicines, and textiles. It is highly toxic to mankind and can lead to many diseases including carcinogenicity. Removal of erythrosine has been carried out using waste material--hen feathers--as adsorbent. The effects of pH, concentration of the dye, temperature, and adsorbent dosage have been studied. Adsorption of erythrosine over hen feathers has been correlated with Freundlich and Langmuir isotherms and satisfies both models. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (DeltaG(0)), change in enthalpy (DeltaH(0)), and change in entropy (DeltaS(0)) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. The adsorption follows a first-order kinetics at all the temperatures and values of the rate constant (k(ad)) have been calculated as 0.0179, 0.0177, and 0.0172 s(-1) at 30, 40, and 50 degrees C, respectively. By rate expression and treatment of data it has been ascertained that the adsorption of erythrosine over hen feathers follows a particle diffusion mechanism.

Order of photocatalytic degradation as ranked by critical photonic times (CPTs) indicates the composition of organic dye mixtures: selectivity of hydroxyl radicals

A simple critical photonic time (CPT) ranking method for the simultaneous determination of known organic dyes in the industrial wastewater of different concentrations was developed. A kinetic-measure, CPT theory, was developed to discriminate between the dyes in the textile effluent solution. The CPTs were calculated and ranked 1-4 from the smallest to the largest. The ranks indicate the order in which the individual dyes in the effluents were photocatalytically degraded. The described procedure allowed us to monitor the decolorization kinetics of the dyes in mixtures of different concentrations, when subjected to immobilized TiO2 photocatalysis in the presence of H2O2 from the start (H2O2FS). The outcome of hydroxyl radical (HO*) attack was consistently specific and regioselective for the individual dyes in the textile effluent. To explain the effect of HO*, the order of degradation of Acid Orange 52 < Acid Yellow 36 < Acid Red 17 < Acid Blue 45 < polyvinyl alcohol (PVA) was inferred.