Linear Alkylbenzene Sulfonates Homologues Research Articles

Predictive Study of the Influence of the Position of the Sulfonate Substituent on the Chemical Stability of Some Linear Alkylbenzene Sulfonate Isomers

Molecules from industrial formulations are used as palliative solutions in the treatment and reuse of industrial waste, with very encouraging results in developing countries. However, the lack of knowledge of the physicochemical properties of these molecules constitutes a major obstacle in the search for an effective solution. To contribute to the characterization of their physicochemical properties, twenty molecules of linear alkyl benzenesulphonate isomers of C10 and C13 homologs and their parent structures were the subject of this study. The stability and overall reactivity parameters such as the energy gap (.∆E), the chemical potential (μ), the electrophilic index (ω) as well as the molecular dipole moment (μD) are determined by the DFT method with the level B3LYP / 6-311G (d, p) / (water; IEFPCM). The results showed that the meta position of the sulfonate substituent increases overall stability and reactivity and decreases the solubility of the more stable 2C10, 4C10, 2C13 and 3C13 homologues of linear alkylbenzene sulfonates. The parent molecules (2mC10, 4mC10, 2mC13 and 3mC13) obtained more stable and less soluble are in favor of the effects observed in the treatment of industrial waste.

Occurrence, fate and environmental risk of linear alkylbenzene sulfonate in the Langat and Selangor River basins, Malaysia

Five homologs (C10-C14) of linear alkylbenzene sulfonate (LAS) were quantitated in surface water collected in the Langat and Selangor River basins using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A geographic information system (GIS) was used to spatially analyze the occurrence of LAS in both river basins, and the LAS contamination associated with the population was elucidated by spatial analysis at a sub-basin level. The LAS concentrations in the dissolved phase (<0.45 μm) and 4 fractions separated by particle size (<0.1 μm, 0.1–1 μm, 1–11 μm and >11 μm) were analyzed to elucidate the environmental fate of LAS in the study area. The environmental risks of the observed LAS concentration were assessed based on predicted no effect concentration (PNEC) normalized by a quantitative structure–activity relationship model. The LAS contamination mainly occurred from a few populated sub-basins, and it was correlated with the population density and ammonia nitrogen. The dissolved phase was less than 20% in high contamination sites (>1000 μg/L), whereas it was more than 60% in less contaminated sites (<100 μg/L). The environmental fate of LAS in the study area was primarily subject to the adsorption to suspended solids rather than biodegradation because the LAS homologs, particularly in longer alkyl chain lengths, were considerably absorbed to the large size fraction (>11 μm) that settled in a few hours. The observed LAS concentrations exceeded the normalized PNEC at 3 sites, and environmental risk areas and susceptible areas to the LAS contamination were spatially identified based on their catchment areas.

Degradation of surface-active compounds in a constructed wetland determined using high performance liquid chromatography and extraction spectrophotometry

Degradation of anionic and nonionic surfactants in a constructed wetland with horizontal subsurface flow was studied using high performance liquid chromatography and extraction spectrophotometry. The ratio of individual homologues of linear alkylbenzene sulfonates (LAS) and the efficiency of their removal were studied. Tridecyl-, dodecyl-, undecyl-, and decylbenzene sulfonates were removed with efficiencies of 92.9%, 84.3%, 64.7%, and 41.1%, respectively. These differences are due to sequential shortening of the alkyl chain in homologues during degradation (the higher homologue can provide the lower one). The formation of sulfophenyl carboxylic acids during ω-oxidation of the alkyl chain followed by successive α- and/or β-oxidation is also a possible mechanism for removal of LAS. Solid phase extraction using Chromabond® HR-P columns was used for preconcentration of the analytes prior to their determination by HPLC. Methylene blue active compounds were determined using extraction spectrophotometry. The average efficiency of their removal was 84.9% in this case. The efficiency of nonionic surfactant removal (98.2%) was significantly higher in comparison to that for anionic surfactants. The concentration of the endocrine disruptor nonylphenol (a product of nonylphenol polyethoxylate surfactant degradation) determined in the profile of the wetland was beneath the limit of detection (0.4 μg/L). The average outflow concentrations of anionic and nonionic surfactants determined by spectrophotometry were 0.54 and 0.021 mg/L, respectively. The average outflow concentrations of decyl- and tridecylbenzene sulfonates determined by HPLC were 0.195 and 0.015 mg/L. Efficiencies of 86.4% and 92.2% were obtained for removal of organic compounds as indicated by chemical and biochemical oxygen demand (CODCr and BOD5). These results demonstrate the suitability of the constructed wetland for degrading surface-active compounds.

Temporal Evolution of Linear Alkylbenzene Sulfonates and Heavy Metals in Sludge from Wastewater Treatment Plant

Five homologues of linear alkylbenzene sulfonates (LAS)-LAS C-10, LAS C-11, LAS C-12, and LAS C-13 and total LAS-were monitored during a one-year period in primary, secondary, and digested sludge to evaluate their presence and temporal evolution. Extraction of LAS was carried out using microwaves energy, and determination was performed using high-performance liquid chromatographic- fluorescence (HPLC-FL). The results showed that concentrations of total LAS were between 9 337 mg/kg(-1) dry matter for primary sludge and 33.3 mg/kg(-1)(DM) for secondary sludge. Concentrations of total LAS were greater than 2 113 mg/kg(-1) in primary and digested sludge and were less than 260 mg/kg(-) in secondary sludge. On the other hand, the highest concentrations of LAS in primary sludge were found in summer, probably because of lack of rain during those months. Concentrations tend to be constant throughout the year in digested sludge. In addition heavy metals also were analyzed. Heavy metals, including zinc, copper, nickel, lead, and chromium are persistent environmental contaminants that cannot be destroyed. Biomagnification through the food-chain and potential accumulation in human tissues can cause both human health and environmental concerns. Concern regarding total heavy metal content of sludge limits sludge recycling for use on agricultural lands. This paper presents a comparative study of wastewater sludge that are going to be used as fertilizer based on the requirements of legislation proposed in the European Union. This research found that concentrations of total LAS in digested sludge are higher than the limits established in the proposed new draft.

Method for the simultaneous determination of the most problematic families of organic pollutants in compost and compost-amended soil

Linear alkylbenzene sulfonates (LAS), nonylphenol ethoxylates (NPE; sum of nonylphenol, nonylphenol monoethoxylate, and nonylphenol diethoxylate), and di-(2-ethylhexyl)phthalate (DEHP) are the most problematic organic pollutants in sludge owing to their high concentrations and the concentration limits of 2,600, 50, and 100 mg/kg, respectively, proposed in the European Union directive draft for land application of sludge. In this paper, an analytical method for the simultaneous determination of the C(10), C(11), C(12), and C(13) LAS homologues, the nonylphenolic compounds nonylphenol, nonylphenol monoethoxylate, and nonylphenol diethoxylate, and di(2-ethylhexyl)phthalate in compost and compost-amended soil is proposed. The method is based on sonication-assisted extraction, cleanup by solid-phase extraction, and determination by high-performance liquid chromatography with diode-array and fluorescence detectors. The mean recoveries of LAS, NPE, and DEHP were 83, 87, and 79%, respectively, in compost samples, and 77, 96, and 99%, respectively, in compost-amended soil samples. The limits of detection and quantification in compost samples were lower than 6.77 and 22.3 mg/kg dry matter, respectively, for LAS; lower than 7.34 and 22.8 mg/kg dry matter, respectively, for NPE; and 0.78 and 1.18 mg/kg dry matter, respectively, for DEHP. The limits of detection and quantification in compost-amended soil samples were lower than 0.03 and 0.10 mg/kg dry matter, respectively, for LAS; lower than 0.04 and 0.12 mg/kg dry matter, respectively, for NPE; and 0.03 and 0.10 mg/kg dry matter, respectively, for DEHP. The method was successfully applied to compost and compost-amended soil samples from Seville (south of 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.

Analysis of linear alkylbenzene sulfonate homologues in environmental water samples by mixed admicelle-based extraction and liquid chromatography/mass spectrometry

Hemimicelles and admicelles of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), adsorbed onto silica, were tested as sorbents for the solid phase extraction (SPE) of linear alkylbenzene sulfonate (LAS) homologues from environmental water samples. LASs were quantitatively retained on both surfactants due to high hydrophobic and ionic interactions, which led to the formation of analyte-extractant mixed aggregates. Parameters affecting the SPE of LASs were optimised. Recoveries of analytes from wastewater influent and effluent and river water samples ranged between 86 and 110%. Combination of SPE with liquid chromatography/mass spectrometry provided detection limits for the different LAS homologues of about 4 ng L(-1). The precision of the method, expressed as relative standard deviation, ranged from 5 to 9%. The method was applied to the analysis of LASs in wastewater and river samples using sample volumes between 10 and 25 mL. The LAS concentrations found ranged from 9 to 503 microg L(-1). No cleaning step was required to get accurate results.

Anaerobic digestion of linear alkyl benzene sulfonates: Biodegradation kinetics and metabolite analysis

In the present work the effect of the alkyl chain length and the position of the sulfophenyl substituent of the linear alkylbenzene sulfonates (LAS) on their anaerobic biodegradability have been investigated. Degradation kinetics of the linear alkyl benzene sulfonates homologues, 2 ϕC 10LAS, 2 ϕC 12LAS and 2 ϕC 14LAS, have been studied. It has been also investigated the effect of the isomer type on the degradation rate of the LAS molecule through the comparative study of the 2 ϕC 10LAS and 5 ϕC 10LAS isomers. Batch anaerobic biodegradation tests were performed using sludge from the anaerobic digester of a wastewater treatment plant as microorganisms source. Ultimate biodegradation was evaluated from the biogas production whereas primary biodegradation was determined by specific analysis of the surfactant. LAS homologues and isomers showed a negligible primary biodegradation under anaerobic conditions. Furthermore, analysis of sulfophenyl carboxilates (SPC) by LC–MS indicated a low and constant level of these LAS degradation metabolites over the test period. These data are consistent with a minimal transformation of the LAS parent molecule in the anaerobic digesters. On the other hand, the addition of the shortest alkyl chain length homologues, decyl and dodecylbenzene sulfonates, reduces the biogas production whereas the most hydrophobic homologue, the tetradecylbenzene sulfonate, enhances the biogas production. This LAS homologue seems to increase the availability of organic compounds sorbed on the anaerobic sludge promoting their biodegradation.

Levels Of Linear Alkylbenzenesulfonates (LAS) In Sediments Of The Berre Lagoon (FRANCE)

A method is described to extract, concentrate and determine trace levels of linear alkylbenzenesulfonates (LAS) (a major anionic surfactant) from sediment samples. It consists of an ultrasonic extraction, followed by clean up and enrichment with C18 mini-columns cartridges and determination by HPLC. Both efficiency and accuracy of the method are high, i.e. mean recovery of 85% and repeatability of 2.8% relative standard deviation for five-replicate LAS analyses. The spatial distribution of LAS and their composition of homologues in sediments of the Berre lagoon, the widest lagoon of the Mediterranean littoral, have been studied. The levels of total LAS in sediments range from 0.21 to 5.00 mg=g (dry weight). Results show that LAS principally associated with solids in suspension, and originating from industrial and urban wastewaters, are principally discharged into the Arc and Cadière Rivers then decant in the mouths of these rivers. The maximum concentrations have been monitored in three zones of the site: the Bolmon lagoon, the Vaine lagoon and the northeast part of the Berre lagoon. The distribution of the LAS homologues in the sediments is not the same as that of the commercial LAS. A great percentage of C13-LAS has been observed (>50%).

Occurrence and distribution of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids in several Iberian littoral ecosystems

The distribution of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPC) has been characterized in water and sediment of five Iberian estuaries and a saltmarsh channel. The highest concentrations of LAS and SPC were detected in shallow zones close to discharge points of untreated urban effluent, and decreased sharply with increasing distance from these. SPC homologues of between 3 and 12 carbon atoms were detected, although their concentrations were several orders of magnitude lower than the corresponding LAS. The highest SPC concentrations found were of medium carboxylic chain lengths (C6–C8) in water, and of longer chain lengths (C9–C11) in particulate material. LAS homologues were associated preferentially with the particulate material. The vertical distribution of LAS in the water column was not homogeneous, in contrast to that presented by the SPC homologues. In the case of the Sancti Petri Channel, there was a net flow of LAS exportation into the Bay of Cádiz, of −38.6 kg day −1, and a net flow for SPC of −6.0 kg day −1. The daily mass input of LAS and their biodegradation intermediates from the Sancti Petri Channel to Cadiz Bay was 44.6 kg.

Formation of metabolites during biodegradation of linear alkylbenzene sulfonate in an upflow anaerobic sludge bed reactor under thermophilic conditions.

Biodegradation of linear alkylbenzene sulfonate (LAS) was shown in an upflow anaerobic sludge blanket reactor under thermophilic conditions. The reactor was inoculated with granular biomass and fed with a synthetic medium and 3 micromol/L of a mixture of LAS with alkylchain length of 10 to 13 carbon atoms. The reactor was operated with a hydraulic retention time of 12 h with effluent recirculation in an effluent to influent ratio of 5 to 1. A sterile reactor operated in parallel revealed that sorption to sludge particles initially accounted for a major LAS removal. After 8 days of reactor operation, the removal of LAS in the reactor inoculated with active granular biomass exceeded the removal in the sterile reactor inoculated with sterile granular biomass. The effect of sorption ceased after 185 to 555 h depending on the LAS homologs. 40% of the LAS was biodegraded, and the removal rate was 0.5 x 10(-6) mol/h/mL granular biomass. Acidified effluent from the reactor was subjected to dichloromethane extraction followed by gas chromatography/mass spectrometry. Benzenesulfonic acid and benzaldehyde were detected in the reactor effluent from the reactor with active granular biomass but not in the sterile and unamended reactor effluent. Benzenesulfonic acid and benzaldehyde are the first identified degradation products in the anaerobic degradation of LAS.

Analysis of linear alkylbenzenesulfonates by capillary zone electrophoresis with large-volume sample stacking

A systematic investigation of optimal conditions for determining the homologues of linear alkylbenzenesulfonates (LAS) by capillary zone electrophoresis (CZE) using the large-volume sample stacking technique was presented. The most effective sample stacking and separation conditions was 20 m M borate buffer with 30% acetonitrile at pH 9.0, and the sample hydrodynamic injection of up to 90 s at 4 p.s.i. (1 p.s.i.=6892.86 Pa) (around 711 nl). Under such conditions, approximately a 100-fold enrichment factor was achieved based on peak heights. The reproducibility of migration time and quantitative results of stacking CZE can be improved by using internal standards. Quantitation limits of the homologues of LAS were 0.002–0.01 mg/l under these enrichment conditions. The analysis of real samples of laundry and dishwashing detergents was performed. The established high-performance liquid chromatography method was applied to evaluate the stacking CZE method, and compatible results were obtained.

Linear alkylbenzene sulfonates (LAS) as tracers of urban waste waters in shallow littoral ecosystems: A case study in the Bay of Cádiz

The spatial distribution of linear alkylbenzene sulfonates (LAS) and their composition of homologues in sediments of Cádiz Bay, a semienclosed system surrounded by urbanized areas, has been studied. LAS homologues were measured in marine sediments using solid-phase extraction and reversed-phase high-perfomance liquid chromatography with spectrofluorimetric detection. Results showed that LAS, principally associated with solids in suspension and originating from the existing outlet where urban waste waters are discharged into the Sancti Petri Channel, are transported to Cádiz Bay during the ebb tide or emptying phase. The transport of solids in suspension is defined by the circulation of tidal currents and its sedimentation will be encouraged in those zones where the water has a long residence time, zones of low energy, where the accumulation of the surfactant takes place. These results enable the area of influence of the urban waste water discharge to be determined. The distribution of the various LAS homologues in the sediment samples is different from that of the commercial LAS. The greater the distance from the discharge point, the smaller the quantities of the long-chain homologues.

Differentiation of Linear and Branched Alkylbenzenesulfonates by Gas Chromatography/Tandem Mass Spectrometry

A tandem mass spectrometric method was developed to differentiate linear alkylbenzenesulfonates (LAS) and branched alkylbenezenesulfonates (ABS) by gas chromatography and tandem mass spectrometry (GC/MS/MS). Even though the GC retention times of ABS are generally shorter than those of the corresponding LAS homologues, quantification is difficult because they still overlap to some extent. By monitoring the specific fragmentation of derivatized LAS under negative chemical ionization conditions that leads to a deprotonated vinyl-substituted benzenesulfinic acid and the fragmentation of ABS that yields a deprotonated 2-propenyl-substituted sulfinic acid, the overlapping segment can be broken down into LAS and ABS contributions. This allows the quantification of LAS and ABS mixtures such as occur, for instance, in the sedimentary record of natural waters.

Application of Basin Wide Ecological Models (Bawems) to the Fate of LAS in Tokyo Bay

The primary purpose of this study was to simulate the environmental fate of the homologues of linear alkylbenzene sulfonates (LAS). These were selected as representative chemicals with middle-range aquatic toxicity and environmental persistence, which are used in rather large amounts. A secondary purpose was to determine the composition ratio (i.e., the relative percentages of LAS homologues) of LAS products which results in the minimum risk potential in sediments. The following results were obtained from model simulations: 1. By applying basin wide ecological models (BAWEMs) to Tokyo Bay and the surrounding watershed, distribution patterns of LAS homologues in river water, river sediment, seawater, and sea sediment were relatively well simulated. 2. The minimum risk composition ratio of LAS, with the constraint of considering detergent cleaning capacity, is capable of reducing by about 60% the risk potential of the composition ratio of popularly supplied LAS. Reported composition ratios of LAS in existing consumer products are all in the same or rather low risk level categories. It can be concluded that one of the effective strategies of chemical risk management, particularly with reference to alkylbenzene-based synthetic detergents, is alteration of the composition ratio of LAS.

Reduction of aquatic toxicity of linear alkylbenzene sulfonate (LAS) by biodegradation

Partial biodegradation of LAS is shown to significantly reduce the specific toxicity (i.e. per unit weight) of the remaining LAS to Daphnia magna (water fleas) and Pimephales promelas (fathead minnows). This results from the fact that the longer homologs and more terminal isomers, which are the more toxic, are also the more rapidly degraded under bacterial action. The acute aquatic LC 50 of LAS may range from ∼0.5 to ∼50 mg/l depending mainly upon the chain length of the particular homolog. A high molecular weight commercial type LAS with LC 50 around 2 mg/l before biodegradation may show Daphnia LC 50's of 30–40 mg/l. for the LAS remaining after 80–85% degradation. A further contribution to this toxicity reduction may occur if the methylene blue analytical method is used to determine the amount of LAS remaining, since some of the biodegradation intermediates show methylene blue activity but no significant toxicity. For example, sulfophenylundecanoate, a model of early intermediates, shows Daphnia and fathead lc 50's ∼200 and ∼75 mg/l., respectively. Sulfophenylbutyrate, modeling somewhat later intermediates, gives lc 50 values around 5000–10,000 mg/l. Dialkyl tetralin/indane sulfonates (the major non-linear components in commercial LAS) exhibit 1/2–1/10 the toxicity of the corresponding LAS homologs. These results re-emphasize that analysis simply for methylene blue active substances (MBAS) gives no basis for predicting the aquatic toxicity of an environmental sample. And furthermore, that meaningful water quality criteria and standards cannot be established in terms of MBAS content while based on toxicity studies on intact, undegraded LAS.