Determination Of Linear Alkylbenzene Sulfonates Research Articles

A novel method of reversed migration capillary electrophoresis for determination of linear alkylbenzene sulfonates

A reversed migration capillary electrophoresis (RMCE) has been developed to determine linear alkylbenzene sulfonates (LAS). The sample stacking and separation conditions have been systematically investigated and optimized under reversed separation voltage at a low pH value. The separation effect of LAS homologs has been greatly improved based on the relative motion of electrophoresis and electroosmotic flow. RMCE demonstrates a good linear range of 0.1 mg/l to 10.0 mg/l, and the detection limit of LAS homologs reaches 0.001–0.004 mg/l. The relative standard deviations (n=6) of peak area and migration time were 2.25–4.40% and 0.67–0.75%, respectively. RMCE has also been applied for LAS detection in practical wastewater. The results show RMCE exhibits easy pretreatment, fast detection, high sensitivity, good peak shapes and resolution, and less solvent consumption, compared with the established high-performance liquid chromatography method.

Quantitative determination of linear alkylbenzene sulfonate (LAS) concentration and simultaneous power generation in a microbial fuel cell-based biosensor

Linear alkylbenzene sulfonate (LAS), one of the most widely used synthetic surfactants in laundry detergent industry, is considered a hazardous contaminant in wastewater. In the present study, a microbial fuel cell (MFC) based biosensor is developed to quantitively determine the LAS concentration in wastewater. To do so, the developed MFC is fed with LAS concentration of 60 mg l−1. Finally, a sustained biofilm is formed after almost 34 days and the highest open circuit potential of 425 mV is recorded. The maximum power and current densities of 75 mW m−3 and 663 mA m−3 are obtained, respectively; and the internal resistance of the MFC-based biosensor is calculated to be about 1 kΩ. After 98 h, LAS removal and coulombic efficiency are 90% and 65%, respectively. A linear correlation between the current density and LAS concentration (in the range of 10–120 mg l−1) is obtained. Furthermore, a comprehensive model is used to interpret the output electrical signal of the MFC representing temporal and spatial distributions of different microorganisms as well as the hierarchal processes of the LAS biodegradation. The competition between electrogens and methanogens in the biofilm; and also, the effect of external resistance on electrogen concentration are shown as well. Besides, the MFC-based biosensor desirably performed as a power generator and purifier in addition to being an accurate biosensor.

Front Cover: Ionic-liquid-modified magnetic nanoparticles as a solid-phase extraction adsorbent coupled with high-performance liquid chromatography for the determination of linear alkylbenzene sulfonates in water samples

Front Cover: Ionic-liquid-modified magnetic nanoparticles as a solid-phase extraction adsorbent coupled with high-performance liquid chromatography for the determination of linear alkylbenzene sulfonates in water samples

Ionic-liquid-modified magnetic nanoparticles as a solid-phase extraction adsorbent coupled with high-performance liquid chromatography for the determination of linear alkylbenzene sulfonates in water samples.

Novel ionic-liquid-functionalized Fe3 O4 magnetic nanoparticles were synthesized by the thiol-ene click reaction. The prepared functionalized Fe3 O4 nanoparticles possessed multiple interactions, such as electrostatic, hydrophobic, and π-π interactions. The functionalized Fe3 O4 nanoparticles were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and transmission electron microscopy. Four kinds of linear alkylbenzene sulfonates, namely, sodium decylbenzenesulfonate, sodium undecylbenzene sulfonate, sodium dodecylbenzenesulfonate, and sodium tridecylbenzenesulfonate, were selected as model compounds to evaluate the applicability of adsorbents for extraction and subjected to high-performance liquid chromatography analysis. In addition, the effects of various parameters, such as sorbent amount, pH value, ionic strength, sample volume, extraction time, and elution conditions on extraction efficiency were studied in detail. Under the optimum conditions, good linearities were attained, with correlation coefficients between 0.9912 and 0.9968. The proposed method exhibited limits of detection ranging from 0.061 to 0.099 μg/L for all the target analytes. The spiked recoveries of the target analytes in real water samples ranged from 86.3 to 107.5%, with relative standard deviations lower than 7.96%. The enrichment factors of the analytes ranged from 364 to 391, indicating that the obtained functionalized Fe3 O4 nanoparticles can effectively extract trace target analytes from environmental water samples.

Determination of priority pollutants in aqueous samples by dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method followed by high-performance liquid chromatography–triple quadrupole mass spectrometry has been developed for the simultaneous determination of linear alkylbenzene sulfonates (LAS C10, C11, C12, and C13), nonylphenol (NP), nonylphenol mono- and diethoxylates (NP1EO and NP2EO), and di-(2-ethylhexyl)phthalate (DEHP). The applicability of the method has been tested by the determination of the above mentioned organic pollutants in tap water and wastewater. Several parameters affecting DLLME, such as, the type and volume of the extraction and disperser solvents, sample pH, ionic strength and number of extractions, have been evaluated. Methanol (1.5mL) was selected among the six disperser solvent tested. Dichlorobenzene (50μL) was selected among the four extraction solvent tested. Enrichment factor achieved was 80. Linear ranges in samples were 0.01–3.42μg L−1 for LAS C10–13 and NP2EO, 0.09–5.17μgL−1 for NP1EO, 0.17–9.19μgL−1 for NP and 0.40–17.9μgL−1 for DEHP. Coefficients of correlation were higher than 0.997. Limits of quantitation in tap water and wastewater were in the ranges 0.009–0.019μgL−1 for LAS, 0.009–0.091μgL−1 for NP, NP1EO and NP2EO and 0.201–0.224μgL−1 for DEHP. Extraction recoveries were in the range from 57 to 80%, except for LAS C10 (30–36%). The method was successfully applied to the determination of these pollutants in tap water and effluent wastewater from Seville (South of Spain). The DLLME method developed is fast, easy to perform, requires low solvent volumes and allows the determination of the priority hazardous substances NP and DEHP (Directive 2008/105/EC).

Trace determination of linear alkylbenzene sulfonates using ionic liquid based ultrasound-assisted dispersive liquid–liquid microextraction and response surface methodology

A new method was developed for determination of linear alkylbenzene sulfonates (LASs) in environmental water samples using ionic liquid based ultrasound-assisted dispersive liquid–liquid microextraction (IL-USA-DLLME) coupled with spectrophotometry detection. Different operational conditions affecting extraction efficiency of LASs including pH, volume of extraction solvent, methylene blue (MB) concentration, salt concentration and sonication time were studied via central composite design (CCD) optimization method. The statistical parameters of the model were F = 39.01 and R2 = 0.9254. The optimal conditions were 8.3 for sample pH, 72 μL for extraction solvent, 49.2 μg mL−1 for MB concentration, 17.2% (w/v) for sodium chloride concentration and 30 s for sonication time. Under the optimal conditions, a calibration curve was obtained with linear dynamic range between 0.8 and 100 ng mL−1 and detection limit of 0.37 ng mL−1. The relative standard deviation (RSD%, n = 5) for the extraction and determination of 40.0 ng mL−1 of linear alkylbenzene sulfonates in the aqueous samples was obtained as 2.0%. The proposed method was successfully applied to determine concentrations of LASs in different non-spiked aqueous samples and satisfactory results were obtained.

Matrix effect study in the determination of linear alkylbenzene sulfonates in sewage sludge samples

We propose a study of the matrix effect in the determination of linear alkylbenzene sulfonates (LAS) in sewage sludge samples. First, a rapid, selective and sensitive method is proposed. The method involves two stages: the extraction of the compound from the samples and analysis by liquid chromatography with fluorescence detection (LC-FLD). Three different techniques of extraction (microwave-assisted extraction, Soxhlet, and ultrasounds) were compared, and microwave-assisted extraction was selected as the best suited for our purpose. Microwave-assisted extraction allows reducing the extraction time (25 min compared with 12 h for conventional Soxhlet extraction) and solvent waste (25 ml of methanol compared with 200 ml for Soxhlet or more than 50 ml for the ultrasonic procedure). Absence of matrix effect was evaluated with two standards (2ØC(8:0) and 2ØC(16:0) ) that are not commercial; therefore, neither of them was detected in sewage sludge samples and they showed similar environmental behavior (adsorption and precipitation) to LAS (C(11:0) -C(13.0) ), which allow us to evaluate the matrix effect. Validation was carried out by a recovery assay, and the method was applied to samples from different sources; therefore, they had different compositions.

Determination of linear alkylbenzene sulfonates by ion-pair solid-phase extraction and high-performance liquid chromatography

In this paper, the potential use of multiwalled carbon nanotubes (MWCNTs) as solid phase extraction (SPE) adsorbent was evaluated for preconcentration of linear alkylbenzene sulfonates (LAS) using ion-pair (IP)-SPE with tetrabutylammonium hydroxide (TBAH). The LAS homologues present in the aqueous sample were ion-paired with TBAH and the solution was passed through the MWCNT cartridges. The analytes retained in the cartridge were eluted with methanol and the concentrated methanol extract was analysed by HPLC-UV. In order to obtain the satisfactory recovery of LAS homologues, various parameters including the type and amount of the ion-pair reagents, the desorption and enrichment conditions such as the effect of eluent and its volume, pH, the flow rate, the ultrasonic time of sample, and the volume of sample solution were systematically optimized. Under the optimal conditions, LAS homologues could be easily extracted by the proposed SPE cartridge. The favorable limits of detection (LOD) for LAS homologues were in the range from 0.02 to 0.03μgL−1, and the relative standard deviations (RSDs) were 1.55–2.54% for 10μgL−1 LAS (n=6). The proposed method has been successfully applied for the analysis of LAS homologues in aqueous environmental samples. A comparison study with ion-pair solid extraction on MWCNTs, C8 and C18 as adsorbents for LAS demonstrated that ion pair-based solid extraction on MWCNTs adsorbent was advantageous over C8 and C18, the widely used traditional adsorbents.

Determination of linear alkylbenzenesulfonates (LASs) in sewage sludge and carrots by capillary electrophoresis–UV detection

A method based on capillary zone electrophoresis has been proposed in order to separate and determine four groups of linear alkylbenzenesulfonates in sewage sludge and carrots. The separation was carried out in a silica capillary of 50 cm × 75 µm at 25 kV using a sodium borate buffer solution of 100 mM which includes 40% of acetonitrile. The detection was made by UV–Vis diode array detector. Precision, accuracy, linearity, detection and quantification limits of the method were determined. Finally, the method was applied to analyse samples of sewage sludge from a wastewater depuration station in Crispijana (Alava, Spain) and carrots sown in soils spiked with this sludge. In this case, it is necessary to carry out an extraction step for its determination. The extraction was carried out by solid phase extraction with a C18 cartridge. The solid phase extraction (SPE) parameters were also optimized and the recoveries were calculated. Samples of sewage sludge were analysed weekly during two years and, in all cases, results under legal limits for their use in agriculture were obtained.

Trace Determination of Linear Alkylbenzene Sulfonates: Application in Artificially Polluted Soil—Carrots System

Surfactants are widely used in household and industrial products. The risk of incorporation of linear alkylbenzene sulfonates (LAS) from biosolids, wastewater, and fertilizers land application to the food chain is being assessed at present by the European Union. In the present work, a complete analytical method for LAS trace determination has been developed and successfully applied to LAS (C10–C13) uptake in carrot plants used as model. These carrots were grown in soil with the trace organics compounds added directly into the plant containers in pure substances form. LAS trace determination (μg kg−1 dry matter) in carrots samples was achieved by Soxtec apparatus and high-performance liquid chromatography-fluorescence detection. The methodology developed provides LAS determination at low detection limits (5 μg kg−1 dry matter) for carrot sample (2 g dry matter) with good recoveries rate (>90%). Transfer of LAS has been followed into the various parts of the carrot plant. LAS are generally found in the carrot leaves and percentage transfer remains very low (0.02%).

Application of probe sonication extraction for the determination of linear alkylbenzene sulfonates from sewage sludge. Comparison with other extraction methods

A new method based on probe sonication extraction (USP) prior to high performance liquid chromatography (HPLC) has been developed for the determination of linear alkylbenzene sulfonates (LAS) from sewage sludge. The optimized method was designed to be cost effective compared to existing extraction methods (ultrasonic assisted extraction, Soxhlet or pressurized liquid extraction) which may require large quantities of organic solvents, or costly instrumentation or equipment. The main factors affecting the extraction efficiency (extractant volume, ultrasounds power and extraction time) were optimized using compost sludge. The detection limit of total LAS in the sludge was 10 mg kg − 1 . The extraction of C 10–C 13 homologues is carried out using an extraction time of 7 min with 10 mL of methanol. Liquid chromatography with fluorescence (FL) detector is used for determination of LAS homologues. A mobile phase acetonitrile-water containing 0.1 M NaClO 4 (65:35) and isocratic elution was used. Compounds were eluted over 6 min at a flow rate of 1 mL/min. Polar interferences are eluted between 0 and 2 min and no purification of the samples is required prior to the final determination by high performance liquid chromatography (HPLC). The recoveries of LAS in spiked sewage sludge were between 84.0% and 97.0%, which reflect the efficiency of the method for extraction of these analytes from sewage sludge. Concentration levels found were between 11,858 mg kg − 1 for digested sludge and 2379 mg kg − 1 for compost sludge.

Surface Plasmon Resonance Immunosensor for Anionic Surfactants Based on an Indirect Competitive Immunoreaction

A highly sensitive surface plasmon resonance immunosensor for the determination of linear alkylbenzene sulfonate (LAS) was fabricated. The method is based on an indirect competitive reaction of an anti‐LAS antibody in a sample solution with LAS immobilized on a sensor chip and with LAS in the sample solution. A sensor chip immobilized with LAS was prepared by utilizing an electrostatic interaction between an LAS conjugate, LAS–horseradish peroxidase (LAS‐HRP), and a self‐assembled monolayer of 11‐amino‐1‐undecanethiol hydrochloride, which was preliminary prepared on a gold thin film of the sensor chip. The quantitative determination of LAS in the concentration range 10–1000 ppb was achieved by using the proposed immunosensor.

Lab‐on‐valve for the automatic determination of the total content and individual profiles of linear alkylbenzene sulfonates in water samples

Methods for the total content and individual determination of linear alkylbenzene sulfonates (LAS) in water samples based on the use of a lab-on-valve (LOV) module alone or coupled to CE equipment, respectively, have been developed. The total content of LAS has been determined by intrinsic absorption measurements (DA method) and after reaction with a methyl orange-cetylpyridine chloride mixture (MO method) with detection limits (LODs) of 21 ng/L and 15 microg/L, respectively, quantification limits (LOQs) of 70 ng/L, 50 microg/L, and development times of 100 and 124 s, respectively. The method for individual separation-quantification of LAS at very low concentration is based on automatic SPE preconcentration in the LOV module coupled on-line with the CE equipment. The LODs and LOQs thus obtained range between 1-21 and 4-70 ng/L, respectively, with linear dynamic ranges from the LOQ to 10 microg/L. Preconcentration factors of 10,000 and high efficiency to eliminate interferents by SPE enable application of the method to treated effluent, waste, surface and sea waters.

New sample treatment for determination of linear alkylbenzene sulfonate (LAS) in agricultural soils by liquid chromatography with fluorescence detection

A new sample-treatment procedure has been developed for determination of total linear alkylbenzene sulfonate (LAS), i.e. homologues and isomers, in agricultural soil. The procedure involves two steps, ultrasound-assisted extraction of LAS from the samples with methanol then clean-up of the methanolic extracts and preconcentration of the LAS by solid-phase extraction on two adsorbent cartridges (SAX and C18). The ultrasound-assisted procedure reduces extraction time (10 min in contrast with 6-12 h for conventional Soxhlet extraction) and requires only small volumes of organic solvent. The effect of different variables interacting in the ultrasound-assisted extraction process was studied. Finally, separation and quantification of the homologues and isomers of LAS was performed by liquid chromatography with fluorescence detection (LC-FD). 2-Octylbenzenesulfonic acid sodium salt (Na-2ØC8-LAS) was used as internal standard. The proposed method was satisfactorily used for determination of LAS in agricultural soil samples from the fertile plain of Granada (Spain).

Specific Determination of Linear Alkylbenzenesulfonates (LAS) in Commercial Detergents and Whole Blood by High-Performance Liquid Chromatography with Solid-Phase Extraction

This paper presents the extraction and analysis of linear alkylbenzenesulfonates (LAS) from whole blood using solid-phase extraction (SPE) together with high-performance liquid chromatography (HPLC). The sample was buffered with extraction solution and purified with Bakerbond C(18) SPE columns. The columns were washed, dried, and eluted with experimental optimized solvent systems. HPLC was performed using a Wakopak) WS AS-Aqua column (4.6 * 250-mm) and monitored at 228 nm using a UV detector. A mobile phase consisting of acetonitrile/water (60:40, v/v) and containing 1.2% (w/v) of sodium perchlorate was employed. Good separation was achieved for the five homologues of LAS (C(10) approximately C(14)) eluted at 6.85 and 13.79 min. The linearity range for this analysis was found to be from 10.0 to 100.0 ng/g and the limit of detection was 4.0-5.0 ng/g in blood for each homologue. The recovery of each homologue in blood ranged from 76 to 107%. The LAS in commercial detergents could be extracted and the homologues of C(10) approximately C(13) were detected. Blood samples of rats, which were administered a commercial detergent orally, were determined by the present method, and C(14) was used as an internal standard. The method was simple and reliable for the determination of LAS in blood samples and could be expected to apply to the forensic and clinical specimens.

Evaluation of a Newly Developed Enzyme-Linked Immunosorbent Assay for Determination of Linear Alkyl Benzenesulfonates in Wastewater Treatment Plants

A recently developed enzyme-linked immunosorbent assay (ELISA) for the determination of linear alkyl benzenesulfonates (LAS) and long chain sulfophenyl carboxylates (SPCs) has been evaluated for its application in wastewater control analysis. This ELISA based on the use of polyclonal antibodies in an indirect format shows an IC50 of 28.1 +/- 3.2 microg L(-1) and a limit of detection (LOD) of 1.8 +/- 0.6 microg L(-1) in buffer. The assay uses antibodies raised through a pseudoheterologous immunization strategy using an equimolar mixture of two immunogens, N-(4-alkylphenyl)sulfonyl-3-aminopropanoic acid covalently coupled to keyhole limped hemocyanin (SFA-KLH) and sulfophenyl carboxylate 13C13 coupled to KLH (13C13-SPC-KLH). The immunizing haptens have been designed to address recognition versus two different epitopes of the LAS molecule. To assess the performance of this immunoassay in complex real samples, a cross reactivity study was carried out, and the possible interference of other surfactants commonly detected in wastewater, including nonylphenol ethoxylates (NPEOs), nonylphenol (NP), octylphenol (OP), and coconut fatty acid diethanol amides (CDEA), have been evaluated. Additionally, a study of the matrix effects of different types of wastewater was achieved. This ELISA has been evaluated and validated by measuring the LAS content of 22 samples collected from the influents and the effluents of six wastewater treatment plants (WWTP) located in Catalonia, Spain. A solid-phase extraction followed by liquid chromatography coupled to mass spectrometry detection (SPE-LC-MS) has been used as a validation method of the new ELISA test.

Simple and Rapid Determination of Linear Alkylbenzene Sulfonates by In-Tube Solid-Phase Microextraction Coupled with Liquid Chromatography

A simple and rapid method for the determination of linear alkylbenzene sulfonates (LAS) in aqueous samples was developed by using in-tube solid-phase microextraction (SPME) coupled with liquid chromatography (LC). Introducing a short section of open-tubular gas chromatography column as the extraction device, in-tube SPME method has been developed by Pawliszyn et al. for an effective on-line coupling of sample preparation and LC separation. As an open tubular capillary column for the in-tube SPME, we used a porous-layer open-tabular (PLOT) column with a porous layer on the inner wall and a larger surface area. The separation of LAS was carried out by using a mobile phase containing 65% acetonitrile and 35% sodium perchlorate aqueous solution (287 mM) with a Wakopak® WS AS-Aqua column. LAS in the sample solution was enriched through the capillary sequentially by using a microsyringe pump equipped with a gastight syringe and analyzed by using high performance liquid chromatography with fluorescence detection. The fluorescence excitation and emission were fixed at λex = 221 nm and λem =284 nm. With the optimum conditions, linear calibration curves were obtained from 0.2 to 25 μg/l. The detection limits based on 3σ were between 0.02 and 0.10 μg/l and the relative standard deviations of the method were between 1.6 and 12% (n = 5). The method was successfully applied to the determination of LAS in natural water samples. This method was applied to the determination of LAS in some urban river waters where domestic wastewater was discharged.

Sequential injection chemiluminescence immunoassay for anionic surfactants using magnetic microbeads immobilized with an antibody

A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminscence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0–500 ppb) under optimum conditions. The time required for analysis is less than 15 min.

Determination of linear alkylbenzene sulfonates in water samples by liquid chromatography–UV detection and confirmation by liquid chromatography–mass spectrometry

A high-performance liquid chromatographic (HPLC) method was developed for the separation and determination of individual (C 10–C 13) linear alkylbenzene sulfonates (LAS). New sets of conditions have been established for routine analysis of individual chemical forms of four LAS surfactants, i.e. C 10–C 13 LAS. Under a condition set using a mobile phase containing 1.5 mM ammonium acetate in methanol/water 80:20 (v/v) mixture, detection limits obtained were in the range 1.5 ppb (for C 10 LAS) to 11.5 ppb (for C 13 LAS). This offers the advantages of significant improvement in resolution, short separation time and using less amount of common salt under isocratic condition. In addition, the use of simple mobile phase containing a simple low amount of salt cannot deposit at the entrance of mass spectrometric detector. The method is applicable to the simultaneous determination of LAS surfactants in various water samples. LAS surfactants presented in these samples were also successfully confirmed by using electrospray mass spectrometry.

Application of liquid chromatography–electrospray-tandem mass spectrometry for the identification and characterisation of linear alkylbenzene sulfonates and sulfophenyl carboxylates in sludge-amended soils

A novel procedure was developed for the simultaneous determination of linear alkylbenzene sulfonates (LAS) and their major metabolites, sulfophenyl carboxylates (SPC), in sludge-amended soil. After pressurised liquid extraction with methanol/water (90:10) and a clean-up on C 18 solid-phase extraction cartridges, final analysis was done by ion-pair liquid chromatography–electrospray–tandem mass spectrometry (LC–ESI–MS/MS). With this method, SPC with 5–13 carbon atoms in the aliphatic side chain were identified for the first time in agricultural soils treated with sewage sludge. Quantification of LAS and SPC in soil from 10 field sites, which differed in the history of sludge application, gave total concentrations of 120–2840 μg kg −1 for LAS and of 4–220 μg kg −1 for SPC. The data provided evidence for rapid biodegradation of LAS in the initial phase after sludge amendment with a transitory build-up of high concentrations of, mainly, short-chain SPC. Trace amounts of residual LAS and SPC were detected in soils having received the last sludge treatment 10 days to 4 years prior to sampling.