Miniaturized flexible micro-tube plasma ionization source for the effective ionization of non-easily ionizable pesticides in food with liquid chromatography/mass spectrometry.

In this article, we have studied the potential of flexible microtube plasma (FµTP) as ionization source for the liquid chromatography high-resolution mass spectrometry detection of non-easily ionizable pesticides (viz. nonpolar and non-ionizable by acid/basic moieties). Phthalimide-related compounds such as dicofol, dinocap, o-phenylphenol, captan, captafol, folpet and their metabolites were studied. Dielectric barrier discharge ionization (DBDI) was examined using two electrode configurations, including the miniaturized one based on a single high-voltage (HV) electrode and a virtual ground electrode configuration (FµTP), and also the two-ring electrode DBDI configuration. Different ionization pathways were observed to ionize these challenging, non-easily ionizable nonpolar compounds, involving nucleophilic substitutions and proton abstraction, with subtle differences in the spectra obtained compared with APCI. An average sensitivity increase of 5-fold was attained compared with the standard APCI source. In addition, more tolerance with matrix effects was observed in both DBDI sources. The importance of the data reported is not just limited to the sensitivity enhancement compared to APCI, but, more notably, to the ability to effectively ionize nonpolar, late-eluting (in reverse-phase chromatography) non-ionizable compounds. Besides o-phenylphenol ([M - H]-), all the parent species were efficiently ionized through different mechanisms involving bond cleavages through the effect of plasma reagent species or its combination with thermal degradation and subsequent ionization. This tool can be used to figure out overlooked nonpolar compounds in different environmental samples of societal interest through non-target screening (NTS) strategies.

Reticular framework materials in miniaturized and emerging formats in analytical chemistry.

In recent years, important efforts have been put into miniaturization, coming on the scene formats such as chips, 3D-printed objects and paper-based devices. These systems have been applied to biological and chemical processes taking profit of their advantages such as waste reduction, low cost, portability, etc. Despite their benefits, there is a need to continue developing easier-to-use devices with enhanced performance addressed to face the current analytical challenges. In this sense, reticular porous materials such as metal- (MOFs) and covalent- (COFs) organic frameworks with unique features including tailorable porous architectures and tunable chemistry have attracted a lot of attention in various fields. Nevertheless, the combination of these materials with miniaturized and emerging formats has been scarcely investigated. This review is intended to bridge this gap and highlight the recent contributions of these materials in these analytical formats. Thus, this work aims to provide a comprehensive review of the field, highlighting incorporation strategies into the functional supports available to date, and the applications of the resulting systems in both off-site laboratory studies (mostly dedicated to (micro)extraction purposes) and on-site analysis. Finally, a discussion of challenges and future directions in this field is also given.

Ambient (desorption/ionization) mass spectrometry methods for pesticide testing in food: a review.

Ambient mass spectrometry refers to the family of techniques that allows ions to be generated from condensed phase samples under ambient conditions and then, collected and analysed by mass spectrometry. One of their key advantages relies on their ability to allow the analysis of samples with minimal to no sample workup. This feature maps well to the requirements of food safety testing, in particular, those related to the fast determination of pesticide residues in foods. This review discusses the application of different ambient ionization methods for the qualitative and (semi)quantitative determination of pesticides in foods, with the focus on different specific methods used and their ionization mechanisms. More popular techniques used are those commercially available including desorption electrospray ionization (DESI-MS), direct analysis on real time (DART-MS), paper spray (PS-MS) and low-temperature plasma (LTP-MS). Several applications described with ambient MS have reported limits of quantitation approaching those of reference methods, typically based on LC-MS and generic sample extraction procedures. Some of them have been combined with portable mass spectrometers thus allowing "in situ" analysis. In addition, these techniques have the ability to map surfaces (ambient MS imaging) to unravel the distribution of agrochemicals on crops.

Critical assessment of two sample treatment methods for multiresidue determination of veterinary drugs in milk by UHPLC-MS/MS.

In this work, two sample treatment procedures have been evaluated for the determination of veterinary drug residues in milk. In order to cover a wide range of polarities, a total of 66 veterinary drugs with log Kow ranging from - 1 to 5 were selected. Two sample cleanup steps, (i) dispersive solid-phase extraction (dSPE) using enhanced matrix removal lipid as sorbent and (ii) solid-phase extraction (in pass-through mode) using Oasis HLB PRiME cartridges, were critically assessed in terms of sample throughput, recovery, matrix effect, cleanliness of extracts, limit of quantification, and repeatability. The veterinary drugs tested (viz. benzimidazoles, cephalosporins, imidazothiazoles, macrolides, NSAIDs, penicillins, quinolones, steroids, sulfonamides, and ß-agonists) were analyzed by ultra-high-performance liquid chromatography tandem mass spectrometry. According to the results, both methods exhibited similar recovery rates between 70 and 120% for most of compounds tested. Matrix effects were satisfactory for both methodologies, although the tolerance to matrix effects was slightly higher with HLB PRiME with nearly negligible matrix effects in most cases. Limits of quantitation were also well below the current maximum residue levels established by the European Union. Notably, sample throughput was higher in the case of HLB PRiME, since this pass-through SPE cleanup approach involved fewer steps than the EMR-Lipid dSPE approach. The results in terms of analysis time, sensitivity, precision, cleanliness of extracts, and matrix effect showed the suitability of both procedures for the monitoring of veterinary drugs residues in milk samples in a single run. Graphical abstract.

Multi-residue pesticide analysis in virgin olive oil by nanoflow liquid chromatography high resolution mass spectrometry.

In this article, a nanoflow liquid chromatography system coupled to high resolution mass spectrometry (nanoflow LC/ESI Q-Orbitrap-MS) has been applied for the development of a multiresidue pesticide method for the determination of 162 multiclass pesticides in olive oil samples. Due to the relatively high lipid content of the raw QuEChERS acetonitrile extracts obtained from this type of fatty vegetable samples, a dispersive solid phase extraction (dSPE) sorbent proposed to retain both fatty acids and triglycerides, namely Enhanced Matrix Removal-Lipid (EMR-Lipid) has been implemented as additional cleanup step. The analytical performances of the proposed method were evaluated,achieving recoveries in the range 75-119% with relative standard deviations lower than 19% (n = 6). The dSPE sorbent allowed the removal of most coextracted interferences without a significant loss of analytes. Matrix effects were also evaluated, showing a negligible effect for most of the compounds tested, when a dilution factor of 50 was applied. Notably, despite the use of relatively high dilution factors (e.g. 1:50) to minimize matrix effects, the lowest concentration levels detected with this method - in the low µg kg-1 range - are well below the corresponding maximum residue levels established by the current European legislation.

Dilute-and-shoot coupled to nanoflow liquid chromatography high resolution mass spectrometry for the determination of drugs of abuse and sport drugs in human urine.

In this work, a sensitive nanoflow liquid chromatography high-resolution mass spectrometry screening method has been developed for the determination of multiclass drugs of abuse and sport drugs in human urine. 81 drugs belonging to different multiclass pharmaceuticals were targeted. The method is based on the use of a nanoLC column (75 µm × 150 mm, 3 µm particle size and 100 Špore) with the nanospray emitter tip integrated so that dead volumes are significantly minimized. Data acquisition method included both full-scan and all ion fragmentation experiments using an Orbitrap analyser (Q-Exactive) operated in the positive ionization mode. To increase laboratory throughput, a dilute-and-shoot methodology has been tested and proposed, based solely on direct urine dilution without further sample workup. Matrix effects were evaluated, showing a negligible effect for all studied compounds when a dilution 1:50 was implemented. Despite this high-dilution factor, limits of quantification were still satisfactory, with values below 5 µg L-1 in most cases, being lower than their minimum required performance limits correspond established by the World Anti-Doping Agency. Therefore, the use of the dilute-and-shoot method with the enhanced sensitivity provided by nanoflow LC setup could be useful tool for the determination of studied compounds in drug testing, thus increasing laboratory performance, because a minimum sample treatment steps are required.

Renewable chemiluminescence optosensors based on implementation of bead injection principle with multicommutation.

In this work, the implementation of Bead Injection with multicommutation-based flow systems is reported. A surface renewable chemiluminescence (CL) flow sensor is presented based on the use of CL reaction of luminol with H2O2. Dowex 1 × 8 beads with immobilized luminol onto them were injected in the flow system by means of a six-port rotary valve and were accommodated into a 1 mm optical glass flow cell placed just in front of the rectangular photosensor window with the same size than the cell wall. Automatic computer-controlled manipulation of both reagents and sample solutions was undertaken using a multicommutated flow system which comprises five three-way solenoid valves, a home-made electronic interface and a Java-written software. Once the chemiluminescence signal was registered, sensing beads were automatically discarded out with a six-port rotary valve without needing to reverse or stop the flow. As a proof of concept and example, the enhancement of the chemiluminescence signal produced by Co(II) on the luminol-H2O2 reaction in alkaline medium was used for illustrating this implementation determining vitamin B12 in pharmaceutical preparations (after mineralization for releasing Co(II)). The analytical performance of the approach was satisfactory, showing a linear dynamic range from 1.7 to 50 µg L-1, a detection limit of 0.5 µg L-1, RSD (%) of 5.3%, with a sampling frequency of 11 h-1. The proposed approach was applied to different samples and the results were consistent with those obtained with a reference method based on ICP-MS. Based on the same reaction (or re-configuring the system to accommodate it to reaction requirements) the approach can also be applied to the determination of other metal ions such as Cr(III) and Fe(II) and appropriately extended to molecules of bioanalytical interest based e.g. in CL immunoassays, given its versatility.

Direct olive oil analysis by mass spectrometry: A comparison of different ambient ionization methods.

Analytical methods based on ambient ionization mass spectrometry (AIMS) combine the classic outstanding performance of mass spectrometry in terms of sensitivity and selectivity along with convenient features related to the lack of sample workup required. In this work, the performance of different mass spectrometry-based methods has been assessed for the direct analyses of virgin olive oil for quality purposes. Two sets of experiments have been setup: (1) direct analysis of untreated olive oil using AIMS methods such as Low-Temperature Plasma Mass Spectrometry (LTP-MS) or paper spray mass spectrometry (PS-MS); or alternatively (2) the use of atmospheric pressure ionization (API) mass spectrometry by direct infusion of a diluted sample through either atmospheric pressure chemical ionization (APCI) or electrospray (ESI) ionization sources. The second strategy involved a minimum sample work-up consisting of a simple olive oil dilution (from 1:10 to 1:1000) with appropriate solvents, which originated critical carry over effects in ESI, making unreliable its use in routine; thus, ESI required the use of a liquid-liquid extraction to shift the measurement towards a specific part of the composition of the edible oil (i.e. polyphenol rich fraction or lipid/fatty acid profile). On the other hand, LTP-MS enabled direct undiluted mass analysis of olive oil. The use of PS-MS provided additional advantages such as an extended ionization coverage/molecular weight range (compared to LTP-MS) and the possibility to increase the ionization efficiency towards nonpolar compounds such as squalene through the formation of Ag+ adducts with carbon-carbon double bounds, an attractive feature to discriminate between oils with different degree of unsaturation.

Sensitive Detection of Neonicotinoid Insecticides and Other Selected Pesticides in Pollen and Nectar Using Nanoflow Liquid Chromatography Orbitrap Tandem Mass Spectrometry.

In this work, a new method based on nanoflow LC with high-resolution MS was developed for the determination of eight pesticides in pollen and nectar samples, including neonicotinoid insecticides and other selected pesticides commonly found in bees and beeswax. Detection was undertaken with a hybrid quadrupole-Orbitrap mass spectrometer (Q Exactive™) equipped with a commercial nanospray ion source. The extraction of pesticides from pollen samples was performed by a modified micro-QuEChERS method scaled down to Eppendorf tubes, whereas nectar samples were simply diluted with a water-methanol (95 + 5, v/v) solution. Good linearity (>0.999 in all cases) was obtained between 0.05 and 500 µg/kg and between 0.04 and 400 µg/kg for pollen and nectar, respectively. Recovery rates in pollen ranged from 85 to 97%, with RSDs <12%. Matrix effect was evaluated and showed negligible effects for all studied pesticides. The lowest concentration levels tested and validated were 0.5 and 0.4 µg/kg for pollen and nectar matrixes, respectively. In addition, selected incurred samples were studied, obtaining several positive findings in pollen and nectar samples, demonstrating the sensitivity and applicability of the proposed method.

First investigations for the characterization of glucosamine-6-phosphate synthase by capillary electrophoresis.

The enzyme glucosamine-6-phosphate synthase (GlmS) is an important point of metabolic control in biosynthesis of amino sugar-containing macromolecules and is therefore a potential target in order to design antibacterial and antifungal drugs. It has two oligomerization states, which are the active dimer and the inactive hexamer. For the first time, the potential of CE to separate and quantify the two forms was studied. After incubating GlmS with the d-glucosamine 6-phosphate (GlcN6P) inhibitor, an electrolyte based on sodium phosphate at pH 7.2 and an ionic strength of 100mM plus GlcN6P (either 2 or 20mM) allowed the hexamer-dimer separation. However, the displacement of the dimer/hexamer equilibrium during the analysis time prevented any improvement of the resolution when varying the effective separation length or the temperature of the analysis. Therefore, the use of a short-end CE method allowed the decrease in the analysis time to about 1min. Some parameters such as the temperature and the time of incubation and the ratio of the inhibitor and enzyme concentrations were studied. Then, it was also possible to test, very rapidly and with a very small amount, some molecules having an inhibition potential for the GlmS enzyme (arabinose-5-phosphate oxime, 2-amino-2-deoxy-d-glucitol 6-phosphate, and glucose-6-phosphate).

Stability and effectiveness of linear polyacrylamide capillary coating to suppress EOF in acidic media in the presence of surfactants, ionic liquids and organic modifiers.

Because of its high hydrophilicity, linear polyacrylamide (LPA) has often been used as a coating to suppress electroosmotic flow (EOF) in capillary electrophoresis (CE); however, its stability and effectiveness in acidic media, with or without organic modifiers, surfactants or ionic liquids is not well documented. In this work, the adequacy of LPA coating to suppress EOF in those different conditions was studied. It was shown that electroosmotic mobilities (µEO) did not change for at least 70h of non-stopped operation in all the tested conditions and the coating was stable. It was also shown that LPA coating efficiently suppresses EOF in acidic media (pH 4.0, 3.1, and 2.3) with or without organic modifiers (50% methanol or acetonitrile, ACN), as measured µEO values were between 18 and 84 times lower than those obtained with bare fused-silica capillaries. In acidic media with anionic surfactant (50mM sodium dodecylsulfate, SDS), ionic liquid (25 mM dodecyldimethylimidazolium bromide) or both SDS and ACN (buffer pH 2.1/ACN (8:2, v/v)+50mM SDS) EOF was reduced to a magnitude lower than with bare fused-silica capillaries, even though slight adsorptions of these surfactants were observed. LPA showed its superiority to hydroxypropyl cellulose, for which marked adsorption occurred because of its lower hydrophilicity.

Study of tamoxifen urinary metabolites in rat by ultra-high-performance liquid chromatography time-of-flight mass spectrometry.

Tamoxifen (TMX) is a nonsteroidal estrogen antagonist drug used for the treatment of breast cancer. It is also included in the list of banned substances of the World Anti Doping Agency (WADA) prohibited in and out of competition. In this work, the excretion of urinary metabolites of TMX after a single therapeutic dose administration in rats has been studied using ultra-high-performance liquid chromatography electrospray time-of-flight mass spectrometry (UHPLC-TOFMS). A systematic strategy based on the search of typical biotransformations that a xenobiotic can undergo in living organisms, based on their corresponding molecular formula modification and accurate mass shifts, was applied for the identification of TMX metabolites. Prior to UHPLC-TOFMS analyses, a solid-phase extraction step with polymeric cartridges was applied to urine samples. Up to 38 TMX metabolites were detected. Additional collision induced dissociation (CID) MS/MS fragmentation was performed using UHPLC-QTOFMS. Compared with recent previous studies in human urine and plasma, new metabolites have been reported for the first time in urine. Metabolites identified in rat urine include the oxygen addition, owing to different possibilities for the hydroxylation of the rings in different positions (m/z 388.2271), the incorporation of two oxygen atoms (m/z 404.2220) (including dihydroxylated derivatives or alternatives such as epoxidation plus hydroxylation or N-oxidation and hydroxylation), epoxide formation or hydroxylation and dehydrogenation [m/z 386.2114 (+O -H2 )], hydroxylation of the ring accompanied by N-desmethylation (m/z 374.2115), combined hydroxylation and methoxylation (m/z 418.2377), desaturated TMX derivate (m/z 370.2165) and its N-desmethylated derivate (m/z 356.2009), the two latter modifications not previously being reported in urine. These findings confirm the usefulness of the proposed approach based on UHPLC-TOFMS.

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.

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).

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.

Chromium(VI) oxide oxidation of non-ethoxylated and ethoxylated alcohols for determination by electrospray ionization mass spectrometry.

A new derivatization procedure to increase the sensitivity of electrospray ionization mass spectrometry (ESI-MS) to non-ethoxylated and ethoxylated alcohols was investigated. The analytes were oxidized with chromium(VI) oxide and the resulting carboxylic and ethoxy-carboxylic acids were isolated by extraction with ethyl acetate; the extracts were alkalinized and infused into the ESI-MS system working in the negative-ion mode. The yields of the combined oxidation-extraction were ca. 100% for non-ethoxylated fatty alcohols dissolved in acetone and they decreased moderately in samples containing increasing amounts of water (e.g., a 75% yield was obtained with 50% water). Ethoxylated alcohols with more than two ethylene oxide units resulted in yields of ca. 60%. Low limits of detection (LODs) were obtained when the procedure was applied to the analysis of body-care products and cosmetics containing fatty alcohols, e.g., in a varicose-vein cream, the LODs were 25 microg cetyl alcohol and 7.5 microg stearyl alcohol (detected as palmitic acid and stearic acid, respectively) per gram of sample. High molecular mass alcohols were also detected in seawater after pre-concentration by solid-phase extraction. Thus, the proposed method is particularly valuable for use in industrial samples having complex matrices and in environmental samples and it is competitive with other methods for the analysis of trace amounts of fatty alcohols.

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 microm). 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.

Rapid classification of enzymes in cleaning products by hydrolysis, mass spectrometry and linear discriminant analysis.

A method for the rapid classification of proteases, lipases, amylases and cellulases used as enhancers in cleaning products, based on precipitation with acetone, hydrolysis with HCl, dilution of the hydrolysates with ethanol, and direct infusion into the electrospray ion source of an ion-trap mass spectrometer, has been developed. The abundances of the ([M+H]+ ions of the amino acids, from the hydrolysates of both the enzyme industrial concentrates and the detergent bases spiked with them, were used to construct linear discriminant analysis models, capable of distinguishing between the enzyme classes. For this purpose, the variables were normalized as follows: (A) the ion abundance of each amino acid was divided by the sum of the ion abundances of all the amino acids in the corresponding mass spectrum; (B) the ratios of pairs of ion abundances were obtained by dividing the ion abundance of each amino acid by each one of the ion abundances of the other 17 amino acids in the corresponding mass spectrum. Using normalization procedure B, excellent class-resolution between proteases, lipases, amylases and cellulases was achieved. In all cases, enzymes in industrial concentrates and manufactured cleaning products were correctly classified with >98% assignment probability.

Characterization of poly(4-vinylpyridine 1-oxide) by free-solution capillary electrophoresis and micellar electrokinetic chromatography.

The migration characteristics of poly(4-vinylpyridine 1-oxide) (PVP-NO) in phosphate buffers of acidic pH (20 mM H3PO4 or NaH2PO4) have been studied using both free-solution capillary electrophoresis (FSCE) and MEKC. To inhibit adsorption, 250 mM o-phosphoethanolamine (2-aminoethyl dihydrogen phosphate) was used. In FSCE, PVP-NO showed a narrow peak and a broader band, both having anionic behavior. These peak and band were attributed to the free and aggregated or micellized PVP-NO forms, respectively. According to surface tension measurements, the CMC of SDS in the BGE was 1.8 and 0.48 mM in the absence and in the presence of 1000 microg/mL PVP-NO, respectively, and the association of the polymer with SDS was completed at 9.7 mM SDS. Using MEKC, a narrow peak and a broader band also appeared at SDS concentrations of ca. 1 mM, and their intensity increased with the SDS concentration. These peak and band were attributed to the formation of mixed micelles constituted by both free PVP-NO/SDS and aggregated PVP-NO/SDS, respectively. The determination of PVP-NO by FSCE in commercial additives for laundry was demonstrated.

Separation and determination of alkylglycosides by liquid chromatography with electrospray mass spectrometric detection.

The separation of alkylpolyglycosides by liquid chromatography with electrospray mass spectrometric detection, using either an alkylamide or a cyanopropyl column, and acetonitrile/water mixtures as mobile phases, was developed. Using the alkylamide column and isocratic elution, the alpha- and beta-epimers and ring isomers (pyranosides and furanosides) of the alkylmonoglycosides were resolved. The ring isomers were also resolved in a much shorter time using the cyanopropyl column with gradient elution. Using these columns, the isomers of the alkyldiglycosides and alkyltriglycosides were also partially resolved. The equilibration time was much shorter with the cyanopropyl column, which was selected to perform quantitation studies. The response factors increased more than an order of magnitude with the length of the alkyl chain, from the methyl to the decylmonoglycoside, and decrease largely for the dodecyl and tetradecylmonoglycoside. The limits of detection were of ca. 25 microM from the hexyl up to the dodecylmonoglycoside. The procedures were applied to the characterisation and determination of alkylmonoglycosides in toiletries.