Esmeralda Millán

Kromatografia elektrozinetiko mizelar ezurtsuan oinarrituta metodo bat garatu da perfumeetan Galaxolide®, Tonalide®; eta Traseolide® musketa poliziklikoak kuantifikatzeko. Konposatu horiek kosmetikoen osagai moduan asko erabiltzen dira zainketa pertsonalerako produktuetan. Metodoa optimizatzeko esperimentu-diseinua eta erantzun-gainazalen metodologia erabili ziren. Metodoaren ezaugarri analitikoak ebaluatu ziren eta balio onargarriak lortu ziren ezaugarri hauei dagokienez: linealtasuna, detekzio- eta kuantifikazio-mugak, doitasuna eta zehaztasuna. Optimizatutako eta balioztatutako metodoa perfume-lagin komertzialetan hautatutako osagaiak determinatzeko erabili zen.

In this work, a simple and reliable micellar electrokinetic chromatography method for the separation and quantification of 14 preservatives, including isothiazolinones, and two benzophenone‐type UV filters in household, cosmetic and personal care products was developed. The selected priority compounds are widely used as ingredients in many personal care products, and are included in the European Regulation concerning cosmetic products. The electrophoretic separation parameters were optimized by means of a modified chromatographic response function in combination with an experimental design, namely a central composite design. After optimization of experimental conditions, the BGE selected for the separation of the targets consisted of 60 mM SDS, 18 mM sodium tetraborate, pH 9.4 and 10% v/v methanol. The MEKC method was checked in terms of linearity, LODs and quantification, repeatability, intermediate precision, and accuracy, providing appropriate values (i.e. R² ≥ 0.992, repeatability RSD values ˂9%, and accuracy 90–115%). Applicability of the validated method was successfully assessed by quantifying preservatives and UV filters in commercial consumer products.

A micellar electrokinetic chromatography method was developed for determination of 15 suspected fragrance allergens and preservatives. The target compounds are widely used as ingredients in many personal care products, and all of them are included in the European Regulation concerning cosmetic products. The method was optimized by using a central composite experimental design and response surface methodology. A modified chromatographic response function was defined to weigh the terms in the response function adequately. After optimization of experimental conditions, a background electrolyte of 100 mM sodium dodecyl sulphate and 24 mM sodium tetraborate and pH 9.0 was selected for the separation of the analytes. The developed methodology was evaluated in terms of linearity, limits of detection and quantification, precision and accuracy, showing appropriate values (i.e., R ² = ≥0.99 and accuracy of 89–115 %). Finally, applicability of the micellar electrokinetic chromatography method was assessed by successfully quantifying fragrance allergens and preservatives in commercial personal care products. The most commonly found analyte was linalool (48.3 % of samples) followed by benzoic acid (37.6 %). All samples contained at least one of the target compounds, thus confirming the ubiquity of fragrance allergens and preservatives in personal care products. Scheme of data transformation to obtain the modified chromatogoraphic response function (MCRF)

A screening method for determination of six triazole fungicides (diniconazole, fluquinconazole, flusilazole, myclobutanil, tebuconazole and tetraconazole) using the solid-phase microextraction (SPME) technique coupled to a high-performance liquid chromatography-diode array detector (HPLC-DAD) was developed. Experimental variables were chosen and their values were fixed according to an experimental design with the steps of screening (2⁵⁻¹ fractional factorial design) and optimization of the significant variables (central composite design). Using polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers, the other experimental conditions were: extraction time, 90 min; extraction temperature, 60 °C; NaCl addition, 180 g L⁻¹; static desorption mode and desorption time, 2 min. The method showed good inter and intraday precision (RSD values less than 13.2%) and the limits of detection were from 1.5 to 5.9 μg L⁻¹ in liquid extracts and from 0.08 to 0.3 mg kg⁻¹ in solid products. The method was applied to grape and apple fruit samples previously sprayed with commercial products containing the analytes. Samples were taken from peel, pulp and juice following a pre-harvest interval of two weeks. Also, rain samples under the fruit trees were collected. Myclobutanil and tebuconazole were found in the peel and rain, but not in pulp and juice samples.

A nonaqueous micellar electrokinetic chromatography method was developed for determination of Tonalide®, Galaxolide®, and Traseolide® polycyclic musks (PCMs). These compounds are widely used as fragrance ingredients in cosmetics. The method was optimized by using a three variable Box‐Behnken experimental design and response surface methodology. A modified chromatographic response function was defined in order to adequately weigh the terms in the response function. After optimization of experimental conditions, an electrolyte solution of 195 mM SDS and 40 mM NaH₂PO₄ in formamide was selected for the separation of the three PCMs, and the applied voltage was fixed at 30 kV. The nonaqueous MEKC method was then checked in terms of linearity, limits of detection and quantification, repeatability, intermediate precision and accuracy, providing appropriate values (i.e. RSD values for precision never exceeding 7%, and accuracy 96–107%). Nonaqueous MEKC for determination of the selected compounds was successfully applied to the analysis of commercial perfume samples.

A simple and reliable method for Cd determination in plastic materials using optimized wet acid digestion procedure and atomic absorption spectroscopy was developed. In order to obtain the best experimental conditions for plastic digestion, a 2^7–4 Plackett-Burman design for screening the significant factors and a 2^4–1 central composite design to optimize the significant experimental variables were carried out. The polyethylene European Reference Material ERM-EC680 with certified Cd content was used in both the screening and the optimization steps. The optimized experimental conditions 0.200 g of plastic material digested with 2 mL nitric acid (30 min, 130°C) followed by 1 mL sulfuric acid (30 min, 140°C). The accuracy and precision was checked using ERM-EC680. The Cd recovery was 101.3% and the relative standard deviation was 5.6%. The limit of detection obtained was 0.23 mg kg⁻¹. The method was applied in the analysis of one PVC plastic material, several commercial packaging materials, and plastic toys.

A simple procedure for epychlorohydrin determination in water is presented. In order to optimize the epichlorohydrin extraction conditions in water using headspace (HS)-solid-phase microextraction (SPME), followed by gas chromatography, an experimental design in two steps is performed. Firstly, a 2^5-2 fractional factorial design for screening the significant variables is used. Secondly, a central composite design for optimizing them is carried out. The best experimental conditions are the followings: poly(dimethysiloxane)-divinylbenzene coating fiber; 20 min extraction time; 5°C extraction temperature; 300 g/L sodium chloride; and 20 mL HS volume in a 40-mL vial. Using the previous extraction conditions with gas chromatography (GC)-flame ionization detection equipment, a limit of detection (LOD) of 1.8 µg/L and a relative standard deviation (RSD) of 3.8% (for 25 µg/L) are obtained. With a GC electron capture detection equipment the RSD is 6.6% (for 5 µg/L), and the LOD found is lower (0.08 µg/L). The method is applied to the analysis of water from four treatment plants at the entrance and effluent stream. The standard addition method is used to quantitate the epichlorohydrin that is found in the raw water of the three wastewater treatment plants.