Investigations on the metabolism of alkyl polyglucosides and their determination in waste water by means of liquid chromatography-electrospray mass spectrometry

Alkyl polyglucoside compound influences freshwater plankton community structure in floating field mesocosms

Synthetic surfactants in cleaners and detergents commonly contaminate freshwater systems, therefore use of low-toxicity alternatives is becoming increasingly important. Alkyl polyglucosides (APGs) derived from natural products are less toxic than synthetic surfactants, and degrade rapidly reducing chemical exposure time. However, single species toxicity tests showed APGs have toxic effects on aquatic primary producers and zooplankton, and that species demonstrate different sensitivities to APGs. Furthermore, species unaffected by APGs directly may be indirectly affected by removal of a food source or changes in predator densities, thereby changing plankton community structure. To determine the effects of APGs on plankton communities under environmental conditions, floating mesocosms were deployed in a shallow pond in southeast Georgia, USA and dosed with 0, 0.01, 2.5, 5, or 10 mg L^-1 APG. Zooplankton community composition and abundance, phytoplankton abundance (as chlorophyll a), and water column dissolved oxygen concentration were determined weekly for 1 month. Zooplankton abundance decreased primarily due to loss of copepods, and community composition shifted toward small-bodied cladocerans (Bosmina sp.), and chlorophyll a concentrations declined by up to 81 % following exposure to APG concentrations of 2.5 mg L^-1 or greater. Concentrations of dissolved oxygen never dropped below 5.70 mg L^-1, but the observed declines of ~2 mg L^-1 could become stressful during periods of high water temperatures. Nevertheless, the APG-induced shift from copepod to cladoceran dominated communities and decrease in autochthonous carbon availability has important implications for food availability and quality to higher trophic levels such as planktivorous fishes.

Hot foam for weed control-Do alkyl polyglucoside surfactants used as foaming agents affect the mobility of organic contaminants in soil?

Use of alkyl polyglucosides (APGs) as a foaming agent during hot water weed control may influence the environmental fate of organic contaminants in soil. We studied the effects of the APG-based foaming agent NCC Spuma (C8-C10) on leaching of diuron, glyphosate, and polycyclic aromatic hydrocarbons (PAHs) in sand columns. We also examined how APG concentration affected the apparent water solubility and adsorption of the herbicides and of the PAHs acenaphthene, acenaphthylene and fluorene. Application of APGs at the recommended concentration of 0.3% did not significantly affect leaching of any of the compounds studied. However, at a concentration of 1.5%, leaching of both diuron and glyphosate was significantly increased. The increased leaching corresponded to an increase in apparent water solubility of diuron and a decrease in glyphosate adsorption to the sand. However, APG addition did not significantly affect the mobility of PAHs even though their apparent water solubility was increased. These results suggest that application of APG-based foam during hot water weed control does not significantly affect the mobility of organic contaminants in soil if used according to recommendations. Moreover, they suggest that APGs could be useful for soil bioremediation purposes if higher concentrations are used.

Alkali Metal Cationization of Alkyl Glucosides under Electrospray Ionization Conditions

Alkyl glucosides have been studied by electrospray ionization mass spectrometry. The effect of the hydrophobic and the hydrophilic parts of these compounds on the stability of [M + Na]+ ions has been evaluated by mass spectra at growing cone voltages. The longer the hydrophobic or the hydrophilic part, the higher the stability of these ions. It has been also found that solvent used affects the abundances of [M + Na]+ ions. In order to check if the radii of alkali metal ions influence the stability of their adducts with the compounds studied, the mass spectra have been recorded for solution containing lithium and potassium ions. The cations of smaller radius form more stable adducts, especially with the compounds having longer hydrophobic parts.

Alkyl Poly Glucosides (APGs) Surfactants and Their Properties: A Review

Alkyl polyglucosides are non-ionic surfactants consisting of a hydrophilic saccharide moiety and a hydrophobic fatty alkyl chain. They are synthesized from renewable raw materials and have excellent ecotoxicological profiles and are readily biodegradable. The alkyl polyglucosides are mixtures of homologues, anomers and isomers. The alkyl polyglucosides with a longer alkyl chain biodegrade faster than those with a shorter one. The short to medium alkyl chain containing alkyl polyglucosides are water soluble. They exhibit favorable wetting and surface tension reduction, electrolyte and hard water tolerance, great stability in wide pH range, synergism with other surfactants and act as hydrotropes and dispersants. The dermatological, toxicological, mildness and high compatibility to skin make alkyl polyglucosides superior to all other existing surfactants. They show good functionality in various applications like detergents, food emulsifiers, cosmetic surfactants, industrial emulsifiers and pharmaceutical granulating agents.

Aqueous Solution Properties, Biodegradability, and Antimicrobial Activity of some Alkylpolyglycosides Surfactants

In the present investigation, a series of alkyl polyglycosides with alkyl chain length of C 8, 9, 10, 12 and 14 were synthesized using transacetalization method. Purity of the products was investigated using high performance liquid chromatography. Surface parameters particularly Effectiveness πcmc, Efficiency Pc20, maximum surface excess Γmax, minimum surface area Amin and HLB values are investigated, in addition to thermodynamic parameters (ΔGads and ΔGmic). Resistance to hydrolysis for the prepared compounds was investigated. The synthesized compounds were tested for their biodegradability in Nile river water according to Die-away test method and their antimicrobial activity against different strains of bacteria, yeast and fungi was investigated.

Effect of concentration on the primary and ultimate biodegradation of alkylpolyglucosides in aerobic biodegradation tests

This study examines the primary and ultimate biodegradation of a non-ionic surfactant, an alkylpolyglucoside, in ready biodegradability tests. The surfactant concentration was tested by the anthrone method, while the ultimate biodegradation (mineralization) was analyzed by the total organic carbon determinations. The influence of the concentration on the extent of primary and ultimate biodegradation and the kinetics of degradation also were determined. The primary and ultimate biodegradation was studied at different initial concentrations-15, 25, 50, 75, and 100 mg/L. The increasing concentration of test chemical from 15 to 100 mg/L resulted in a decrease in the relative maximum mineralization rate and longer estimated lag times by a factor of approximately 4.3. During the degradative process, two different stages were noted; these are better described with Quiroga and first-order kinetic models, respectively. For the study of the influence of concentration, the parameters characteristic of the biodegradation profiles in the different biodegradation assays were evaluated.

Analysis of alkyl polyglucosides in industrial products by capillary electrophoresis with pulsed amperometric detection

Pulsed amperometric detection following micellar electrokinetic chromatography has been applied successfully to the direct detection of alkyl polyglucosides (APGs) in shampoos and other industrial products without prior conversion to highly absorbing or fluorescing derivatives. For electrochemical detection, it is necessary to dissociate the hydroxyl groups of the APGs. Thus, we used 0.1 M NaOH in the outlet vial to dissociate the APGs. The main problems associated with the combination of electrochemical detection and capillary electrophoresis are the need to isolate the detector from the electric field used in the capillary electrophoresis separation and the difficulty of aligning the working electrode with the end of the capillary. To overcome these problems, a simple capillary-electrode holder was constructed. This holder automatically aligns the capillary and the electrode in a wall-jet configuration without the aid of micropositioners and facilitates the replacement of electrodes and capillaries without reconstruction of the entire capillary/electrode setup. Special microcylindrical gold electrodes have been produced by sealing 300-microm-diameter gold wire into borosilicate-glass capillaries.

Characterization of Mixtures of Alkyl Polyglycosides (Plantacare) by Liquid Chromatography-Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry

PURPOSE

Industrial products of alkyl polyglycosides (APGs) are widely used as well tolerated surfactants in washing and cleaning agents. APGs belong to the class of nonionic surfactants and are mixtures of molecules consisting of a hydrocarbon chain with Y carbon atoms linked to X sugar residues. Physicochemical properties of APG products strongly depend on the molecular composition. Therefore, a detailed analytical investigation of technical-grade APGs is presented.

METHODS

Complex mixtures of alkyl/alkenyl polyglycosides (APGs, Plantacare) and mixtures of APGs with other surfactants were analyzed by reversed-phase liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOF-MS) using methanol-water as mobile phase and gradient elution.

RESULTS

Analytes were separated according to the chain length of the alkyl homologs. Under the soft ionization of the ESI technique, mainly [M+Na]+ ions were observed, which proved to be very stable. Additionally [M+H]+ ions were detected. The QTOF mass spectrometer allows to identify even high molecular mass components in the mixtures, and APGs up to eight sugar residues were found. From these data, the alkyl/alkenyl chain lengths and the degree of oligomerization of the sugar moiety for different technical-grade APGs were calculated. Using MS/MS experiments, additional structural and chemical information was obtained.

CONCLUSIONS

The presented LC/ESI-QTOF-MS approach allows to analyze and characterize various APG products, such as Plantacare. The ability of this LC/ESI-QTOF-MS approach to analyze mixtures of APGs with other surfactants is demonstrated.

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants

Liquid chromatography-mass spectrometry using atmospheric pressure ionization (LC-API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC-MS application to transformation products.

Characterization of alkyl polyglycosides by both reversed-phase and normal-phase modes of high-performance liquid chromatography

Alkyl polyglycosides today represent the most important sugar surfactant. Nonionic sugar surfactants produced via different synthetic routes are mixtures of alkyl homologues, oligomers, anomers and isomers. Alkyl homologues and oligomers of alkyl mono- and diglucosides were separated by reversed-phase high-performance liquid chromatography (HPLC) with methanol-water as the mobile phase using a gradient elution. The gradient was optimized in respect to a simultaneous separation of alkyl glycosides according to their alkyl chain length and alkyl polyoxyethylene glucosides with regard to their length of the polyoxyethylene spacer. The separation of alkyl glycosides into alpha- and beta-anomers was carried out by normal-phase HPLC with isooctane-ethyl acetate (60:40, v/v)-2-propanol in the gradient mode. Light scattering detection was used. Matrix-assisted laser desorption ionization time-of-flight mass spectra of alkyl glucosides and dodecyl glucosides with oxyethylene spacer groups are presented.

Recalcitrance of poly(vinylpyrrolidone): evidence through matrix-assisted laser desorption-ionization time-of-flight mass spectrometry

The aerobic biodegradability of an extensively used synthetic polymer was monitored the first time on a laboratory-scale fixed-bed bioreactor (FBBR) applying matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). Polymeric poly(vinylpyrrolidone) (PVP) was spiked at concentrations of 10 mg l(-1) onto the FBBR run with river water and the biodegradation monitored after lyophilization of aliquots of the test liquor applying MALDI-TOF-MS. The latter proved to be a powerful tool for qualitative screening purposes of PVP in a molecular mass range <20 kDa in particularly yielding a high sensitivity and shot-to-shot reproducibility. The sample-to-sample reproducibility was enhanced applying the anchor target device. Post-source decay-MALDI-TOF-MS fragmentation investigations determined the unknown end groups of PVP unambiguously. Poor biodegradability of PVP can be assumed, since even after 30 days, no oxidation of the terminal groups and no difference in the repeating units was observed. A decrease in the molecular mass distribution can be drawn back rather to adsorption of PVP in the FBBR other than to biodegradation. This was further investigated performing an adsorption experiment with sewage sludge as solid matrix and analyses of the aqueous phase and sludge samples. Extrapolating these results to the situation in wastewater treatment plants, it is highly likely that PVP is eliminated from the dissolved phase by adsorption onto sludge particles.

Determination of polycyclic aromatic hydrocarbons by liquid chromatography-electrospray ionization mass spectrometry using silver nitrate as a post-column reagent

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) using silver nitrate as a post-column reagent has been used for the determination of 10 polycyclic aromatic hydrocarbons (PAHs) in river water. In this method, after all the PAHs were separated by reversed-phase liquid chromatography, analytes formed complexes with silver cation by mixing with silver nitrate solution. The complexes then transfer the molecular ion, [M]+, of the PAHs by charge transfer using in source collision-induced dissociation. The positive ion ESI mass spectra of all PAHs tested in this study showed [M]+ as the base peak and abundant [M+Ag]+, [2M+Ag]- with very weak or no [2M+Ag]+. For the sample extraction, several solid-phase extraction parameters using the blue-chitin column were optimized. The limits of detection (S/N=3) of all PAHs for the spiked river water sample ranged from 0.001 to 0.03 ng/ml, and the detector responses were linear up to I ng/ml (correlation coefficients > or =0.0998). Repeatability and reproducibility were in the range from 4.3 to 6.8% and from 6.2 to 9.5%, respectively.

Electrospray ionization mass spectrometric studies on the amphoteric surfactant cocamidopropylbetaine

After liquid chromatographic (LC) separation, electrospray ionization mass spectrometry (ESI-MS) was investigated for the determination of the amphoteric surfactant cocamidopropylbetaine (CAPB). In the positive ion mode the molecule formed the adduct ions [M + H](+), [M + Na](+) and [M + K](+). Adducts of these cations were also detected with decreasing abundance as dimer and trimer clusters. Additionally, doubly charged molecular ions with different combinations of cations were identified. It was noticed that the relative abundances of individual cation adducts were not reproducible, apparently owing to varying contents of alkali metal ions originating from the solvent and the sample. Under negative ionization, the major molecular ion was [M - H](-). Higher clusters formed by two and three surfactant molecules, i.e. [2M - H](-) and [3M - H](-) were likewise registered. The tendency to form clusters in both positive and negative ion modes, even at 0.1 mg l(-1) levels, was attributed to strong electrostatic interactions between the zwitterionic head groups. Further evidence for this assumption was provided by the detection of a fragment formed from [2M - H](-) which contained the two charged head groups. Studies were undertaken in the negative ion mode on the concentration- and orifice voltage-dependent monomer, dimer and trimer formation of C(12)-CAPB in order to evaluate potential issues in using the ion [M - H](-) mode for quantitative analysis. Finally, the established (-)-LC/ESI-MS method was applied to follow up the primary degradation of CAPB in a laboratory-scale fixed-bed bioreactor (FBBR) spiked with a test concentration of 10 mg l(-1). Direct analysis without sample pretreatment revealed that higher alkyl homologues were more prone to adsorption. Primary biodegradation of all alkyl homologues was completed after a period of 4 days. Selected lyophilized FBBR samples were examined for the presence of transient or stable degradation intermediates, but no metabolite could be identified.

Aerobic biodegradation studies of nonylphenol ethoxylates in river water using liquid chromatography-electrospray tandem mass spectrometry

The aerobic biodegradation of nonylphenol ethoxylates (A9PEO) was kinetically investigated in a laboratory-scale bioreactor filled with riverwater, spiked at a concentration of 10 mg L(-1) nonionic surfactants. Analyses of the samples applying liquid chromatography-electrospray mass spectrometry (LC-ES-MS) after solid-phase enrichment revealed a relatively fast primary degradation of A9PEO with >99% degradation observed after 4 days. Contrary to the generally proposed degradation pathway of EO chain shortening, it could be shown that the initiating step of the degradation is omega-carboxylation of the individual ethoxylate chains: metabolites with long carboxylated EO chains are identified (A9PEC). Further degradation proceeds gradually into short-chain carboxylated EO with the most abundant species being AgPE2C. The oxidation of the nonyl chain proceeds concomitantly with this degradation, leading to metabolites having both a carboxylated ethoxylate and an alkyl chain of varying lengths (CAPEC). The identity of the CAPEC metabolites was confirmed by the fragmentation pattern obtained with LC-ES-MS/MS. Both A9PEC and CAPEC metabolites are still present in the bioreactor after 31 days. In the aerobic degradation pathway, A9PEO2 is formed only to a minor extent and is even further degraded in several days. The endocrine disruptor nonylphenol was not found as a metabolite in this study.

Isolation of n-decyl-alpha(1-->6) isomaltoside from a technical APG mixture and its identification by the parallel use of LC-MS and NMR spectroscopy

The identification of n-decyl alpha(1-->6)isomaltoside as a main component of technical alkyl polyglucoside (APG) mixtures by the parallel use of liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy is described. Following enrichment on a styrene-divinylbenzene-based solid-phase extraction material, unknown components were separated by reversed-phase liquid chromatography (LC). Chemical characterization was achieved by both mass spectrometry and NMR spectroscopy. It is demonstrated that the combination of LC-MS with various NMR techniques is very suitable for stereochemical assignment of unknown components in technical APG mixtures.

Fate studies of the non-ionic surfactant alkyl glucamide by liquid chromatography/electrospray mass spectrometry

Alkyl glucamides (AGs) were analyzed by reversed-phase liquid chromatography (LC) coupled to mass spectrometry with electrospray ionization (ESMS). Analytes were separated according to the chain length of two homologs, C12- and C14-glucamide. Mass spectrometric detection in the positive ion mode exhibited higher overall sensitivity where, apart from fragments, different molecular and quasi-molecular ions were obtained. However, application of the negative ion mode offered advantages in terms of reproducibility and extent of information when analyzing environmental samples. Therefore, a simple and sensitive analytical methodology was developed for the determination of AGs in municipal sewage treatment plant influent and effluent based on solid-phase enrichment, LC separation and negative ion ESMS quantification. After preconcentration of 100 ml of aqueous sample, the recoveries using polymeric LiChrolut EN cartridges exceeded 89%. A quantification limit of 0.1 microg l(-1) was achieved. Studies on the biodegradability and metabolic pathway of C10-glucamide were carried out on a laboratory-scale microbial test unit under aerobic conditions. A postulated metabolism including omega-oxidation of the alkyl chain followed by subsequent beta-oxidations was checked by LC/ESMS. Identification and formation of 'C4-glucamide acid' as a degradation intermediate was confirmed by mass spectrometric studies. Higher homolog acids such as C10-, C8- and C6-glucamide acids, which should be predicted precursors of C4-glucamide acid, and any other metabolites, were not detectable, presumably owing to rapid breakdown.