Miriam Beneito-Cambra

γ-Oryzanol and tocopherol contents in residues of rice bran oil refining

Rice bran oil (RBO) contains significant amounts of the natural antioxidants γ-oryzanol and tocopherols, which are lost to a large degree during oil refining. This results in a number of industrial residues with high contents of these phytochemicals. With the aim of supporting the development of profitable industrial procedures for γ-oryzanol and tocopherol recovery, the contents of these phytochemicals in all the residues produced during RBO refining were evaluated. The samples included residues from the degumming, soap precipitation, bleaching earth filtering, dewaxing and deodorisation distillation steps. The highest phytochemical concentrations were found in the precipitated soap for γ-oryzanol (14.2 mg g(-1), representing 95.3% of total γ-oryzanol in crude RBO), and in the deodorisation distillate for tocopherols (576 mg 100 g(-1), representing 6.7% of total tocopherols in crude RBO). Therefore, among the residues of RBO processing, the deodorisation distillate was the best source of tocopherols. As the soap is further processed for the recovery of fatty acids, samples taken from every step of this secondary process, including hydrosoluble fraction, hydrolysed soap, distillation residue and purified fatty acid fraction, were also analyzed. The distillation residue left after fatty acid recovery from soap was found to be the best source of γ-oryzanol (43.1 mg g(-1), representing 11.5% of total γ-oryzanol in crude RBO).

Photo-polymerized lauryl methacrylate monolithic columns for CEC using lauroyl peroxide as initiator

Lauryl methacrylate (LMA)‐ester based monolithic columns photo‐polymerized using lauroyl peroxide (LPO) as initiator were prepared, and their morphological and CEC properties were studied. The composition of the polymerization mixture (i.e. ratios of monomers/porogenic solvents, 1,4‐butanediol/1‐propanol and LMA/crosslinker) was optimized. The morphological and chromatographic properties of LMA columns were evaluated by means of SEM pictures and van Deemter plots of PAHs, respectively. The polymerization mixture selected as optimal provided a fast separation of a mixture of PAHs with excellent efficiencies (minimum plate heights of 8.9–11.1 μm). Satisfactory column‐to‐column (RSD<4.5%) and batch‐to‐batch reproducibilities (RSD<6.3%) were achieved. The LMA columns photo‐polymerized with LPO were compared with those prepared with AIBN. Using PAHs, alkylbenzenes and basic compounds for testing, the columns obtained with LPO gave the best compromise between efficiency, resolution and analysis time.

Determination of fatty alcohol ethoxylates and alkylether sulfates by anionic exchange separation, derivatization with a cyclic anhydride and liquid chromatography

A method for the separation, characterization and determination of fatty alcohol ethoxylates (FAE) and alkylether sulfates (AES) in industrial and environmental samples is described. Separation of the two surfactant classes was achieved in a 50:50 methanol-water medium by retaining AES on a strong anionic exchanger (SAX) whereas most FAE were eluted. After washing the SAX cartridges to remove cations, the residual hydrophobic FAE were eluted by increasing methanol to 80%. Finally, AES were eluted using 80:20 and 95:5 methanol-concentrated aqueous HCl mixtures. Methanol and water were removed from the FAE and AES fractions, and the residues were dissolved in 1,4-dioxane. In this medium, esterification of FAE and transesterification of AES with a cyclic anhydride was performed. Phthalic and diphenic anhydrides were used to derivatizate the surfactants in industrial samples and seawater extracts, respectively. Separation of the derivatized oligomers was achieved by gradient elution on a C8 column with acetonitrile/water in the presence of 0.1% acetic acid. Good resolution between both the hydrocarbon series and the successive oligomers within the series was achieved. Cross-contamination of FAE with AES and vice versa was not observed. Using dodecyl alcohol as calibration standard, and correction of the peak areas of the derivatized oligomers by their respective UV-vis response factors, both FAE and AES were evaluated. After solid-phase extraction on C18, the proposed method was successfully applied to the characterization and determination of the two surfactant classes in industrial samples and in seawater.

Determination of non-ionic and anionic surfactants in industrial products by separation on a weak ion-exchanger, derivatization and liquid chromatography.

A method for the determination of priority surfactants, including fatty alcohol ethoxylates (FAE), alkylether sulfates (AES) and linear alkylbenzene sulfonates (LAS) is described. The samples were diluted with 50% methanol at pH 4 prior to solid-phase extraction on a weak anionic exchanger (WAX). The AES and LAS surfactant classes were retained, whereas the non-ionic components, including most FAE oligomers were eluted. After washing the WAX cartridge to remove cations, the remaining hydrophobic FAE oligomers were eluted using hot 80% methanol at pH 4 (at ca. 50°C). These two eluates were combined to constitute the non-ionic fraction. Then, AES and LAS were eluted using 80% MeOH with 3M NH3 followed by 95% methanol with 0.75M NH3. The two eluates obtained in basic media were combined to constitute the anionic fraction. The solvents were evaporated, the residues were dissolved in 1,4-dioxane, and esterification of the alcohols and transesterification of AES with phthalic anhydride was performed. Separation of the derivatized oligomers was achieved by gradient elution on a C8 column with acetonitrile/water in the presence of 0.1% acetic acid and 0.1M NaClO4. The chromatogram of the non-ionic fraction showed the peaks of the resolved FAE oligomers. The chromatogram of the anionic fraction showed the peaks of the LAS homologues well resolved from those of the AES oligomers. The method was applied to laundry and industrial cleaners, shampoos and a shower gel.

Evaluation of molecular mass and tacticity of polyvinyl alcohol by non-equilibrium capillary electrophoresis of equilibrium mixtures of a polymer and a dye.

Non-equilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) has been used to characterize polyvinyl alcohol (PVA). Commercial PVA samples with different molecular masses, from M(w)=15 up to 205 kDa, were used. According to the (13)C NMR spectra, the samples also differed in tacticity (stereoregularity). Mixtures of PVA and the anionic azo-dye Congo Red (CR) were injected in the presence of a borate buffer. The electropherograms gave a band and a peak due to the residual PVA-CR complex and the excess dye, respectively, plus a superimposed exponential decay due to the partial dissociation of the complex during migration. The stoichiometry of the PVA-CR complex, q=[monomer]/[dye], reached a maximum, q(sat), which depended on both M(w) and tacticity of PVA. Thus, q(sat) decreased from a molar ratio of ca. 4.9 to 3.6 at increasing M(w) values, this variation also being largely dependent on tacticity. A similar dependence of the electrophoretic mobility of the complex on both M(w) and tacticity was also observed. A possible explanation, based on the formation of a stack of CR ions inside the PVA-CR complex, was proposed and discussed. Finally, at increasing M(w) values, the stability constant of the complex increased slightly, and the pseudo-first order dissociation rate of the complex decreased, this later parameter also showing a dependence on both M(w) and tacticity.

Comparison of monolithic and microparticulate columns for reversed-phase liquid chromatography of tryptic digests of industrial enzymes in cleaning products

Enzymes of several classes used in the formulations of cleaning products were characterized by trypsin digestion followed by HPLC with UV detection. A polymeric monolithic column (ProSwift) was used to optimize the separation of both the intact enzymes and their tryptic digests. This column was adequate for the quality control of raw industrial enzyme concentrates. Then, monolithic and microparticulate columns were compared for peptide analysis. Under optimized conditions, the analysis of tryptic digests of enzymes of different classes commonly used in the formulation of cleaning products was carried out. Number of peaks, peak capacity and global resolution were obtained in order to evaluate the chromatographic performance of each column. Particulate shell-core C18 columns (Kinetex, 2.6 μm) showed the best performance, followed by a silica monolithic column (Chromolith RP-18e) and the conventional C18 packings (Gemini, 5 μm or 3 μm). A polymeric monolithic column (ProSwift) gave the worst performances. The proposed method was satisfactorily applied to the characterization of the enzymes present in spiked detergent bases and commercial cleaners.

Determination of alcohols in essential oils by liquid chromatography with ultraviolet detection after chromogenic derivatization.

An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. The sample is diluted with 1,4-dioxane and the analytes are derivatized with phthalic anhydride. The derivatives (phthalates hemiesters) are separated on a C8 column using an acetonitrile (ACN)/water gradient. Separation conditions were optimized using the DryLab(®) method development software. For the alcohols and phenols present in mint and rose essential oils, optimization led to a ca. 40min gradient time and a column temperature of 8°C. The alcohol and its derivatives were identified using HPLC with mass spectrometry (MS) detection. A large sensitivity enhancement was obtained by derivatization protocol. The HPLC-UV method was compared to GC with flame ionization detector (FID) and GC-MS. The limits of detection (LODs) obtained by the proposed method were better than those obtained by GC-FID and of the same order as those achieved by GC-MS. The three methods were satisfactorily applied to the determination of alcohols in essential oils. Therefore, the recommended method is of interest as an alternative to GC methods, to investigate the presence of compounds having an alcohol group at low concentrations in essential oils.

Analytical methods for the characterization and determination of nonionic surfactants in cosmetics and environmental matrices

Nonionic synthetic surfactants, constituted of an assortment of classes, are common ingredients of industrial, household and body-care products. Alone or in combination with anionic surfactants, they perform a variety of functions including cleaning action, emulsification, skin conditioning, appearance and consistency modification, solubilization and dispersing agents. By far fatty alcohol ethoxylates (AEs) and alkylphenol ethoxylates (APEs) are more extensively used than any other nonionic surfactant class; however, works appearing in the literature making reference to the analysis of other nonionic surfactant classes have also been collected in this review. The production volume worldwide of AEs and APEs, and consequently their environmental impact, is very high. Although readily biodegraded, stable non-ethoxylated lipophilic residues remain for long periods in the aquatic environment and sediments. In addition to its harmful impact on the food chain, there is also concern on landscape spoiling, particularly in coastal areas. The analytical methods used for quality control of nonionic surfactants in industrial products and in environmental samples are revised and commented upon here. The fundamentals and characteristics of the methods, including their most relevant operative and statistical aspects, are briefly presented. Attention is also paid to the techniques used to extract and preconcentrate the analytes from liquid and solid environmental samples.

Study of the Fragmentation of D-Glucose and Alkylmonoglycosides in the Presence of Sodium Ions in an Ion-Trap Mass Spectrometer

Abstract Using electrospray ion-trap mass spectrometry, the fragmentation of D-glucose and alkylmonoglycopyranosides (alkyl-GPs) was studied. In the presence of Na+, B1 and 0,2A fragmentations were observed. The alkyl-GPs also showed a 2,5Afragmentation. A cluster containing no carbon atoms and adducts of this cluster with neutral molecules were observed. Standards of alkylmonoglycofuranosides (alkyl-GFs) were not available; however, their fragmentation was studied by high-performace liquid chromatography–mass spectrometry (HPLC-MS) and HPLC-MS2 using an industrial mixture of alkylpolyglycosides. The cluster and its adducts were more easily formed by the alkyl-GPs than by the alkyl-GFs, but the 0,2A cross-ring cleavage was more easily produced by the alkyl-GFs.

Single-pump heart-cutting two-dimensional liquid chromatography applied to the determination of fatty alcohol ethoxylates

A setup for heart-cutting bi-dimensional liquid chromatography (LC-LC), constructed with a chromatograph provided with a single pump, an auxiliary 6-port 2-position valve (V6/2) and a column selector valve (VCS), is described. The possible ways of connecting the two valves for LC-LC, namely with V6/2 first followed by VCS and vice versa, are compared. The possibility of using the setups for preconcentration followed by the backwards transfer of the preconcentrated solutes to the detector or to a second column is also shown. The V6/2-first configuration for LC-LC was applied to the characterization of industrial fatty alcohol ethoxylates (FAEs) using UV-vis detection. For this purpose, the phthalates of the FAE oligomers were first obtained. The hydrocarbon series were separated along the 1st dimension by MeOH/water gradient elution on a C8 column at 60°C. Selected segments of the eluate were transferred to the 2nd dimension, where the EO oligomers of the isolated series were resolved by gradient elution with a complementary ACN/water mobile phase on a C8 column at 25°C. In addition, an average response factor of the hydrocarbon series of FAEs was proposed. To apply the factors, the average EO number of the series is first established by chromatographing one of the series along the 2nd dimension. Then, the factors are used to correct the peak areas of the isolated series which are obtained along the 1st dimension chromatogram, thus allowing the fast and accurate determination of the series in industrial FAEs. The method is particularly useful to characterize FAEs having large average EO numbers or constituted by mixtures of even and odd series.