A multi-family offline SPE LC-MS/MS analytical method for anionic, cationic and non-ionic surfactants quantification in surface water

Triethanolamine-based esterquat in sediments: New analytical method, environmental occurrence, and homologue composition

The cationic surfactant triethanolamine-based esterquat (TEAQ) is a main ingredient in commercial fabric softeners and is produced and used in large quantities. However, little information is available for its occurrence in the environment, particularly in sediments. Here, we developed an analytical method for quantifying TEAQ in sediment and investigated TEAQ contamination in Japanese river and lake sediments. In our analytical method, TEAQ concentrations were measured by liquid chromatography-tandem mass spectrometry using a polymer-based size-exclusion column, which resulted in excellent peak shapes. TEAQ was detected at significant levels in procedural blanks, resulting in a method limit of detection in the sediment of 8.9-97 μg/kg-dry for TEAQ monoesters and 0.6-24 μg/kg-dry for TEAQ diesters. TEAQ was detected in 22 out of 26 sediment samples, with the sum of all homologue concentrations being up to 1340 μg/kg-dry. The concentration of TEAQ in sediments was high at locations where the concentrations of benzalkoniums and the organic carbon content were also high. TEAQ was detected in 8 out of 14 commercial fabric softeners at concentrations of 1.7-7.4 wt%. TEAQ homologues containing only saturated fatty acids accounted for 83 ± 5% of the total TEAQ in the sediments, whereas those with unsaturated fatty acids accounted for 71 ± 14% of the total TEAQ in a commercial technical mixture and the softener products. The results of this study will be useful for the environmental risk assessment of esterquats.

Dual-Emission Single Sensing Element-Assembled Fluorescent Sensor Arrays for the Rapid Discrimination of Multiple Surfactants in Environments

Surfactants are considered as typical emerging pollutants, their extensive use of in disinfectants has hugely threatened the ecosystem and human health, particularly during the pandemic of coronavirus disease-19 (COVID-19), whereas the rapid discrimination of multiple surfactants in environments is still a great challenge. Herein, we designed a fluorescent sensor array based on luminescent metal-organic frameworks (UiO-66-NH2@Au NCs) for the specific discrimination of six surfactants (AOS, SDS, SDSO, MES, SDBS, and Tween-20). Wherein, UiO-66-NH2@Au NCs were fabricated by integrating UiO-66-NH2 (2-aminoterephthalic acid-anchored-MOFs based on zirconium ions) with gold nanoclusters (Au NCs), which exhibited a dual-emission features, showing good luminescence. Interestingly, due to the interactions of surfactants and UiO-66-NH2@Au NCs, the surfactants can differentially regulate the fluorescence property of UiO-66-NH2@Au NCs, producing diverse fluorescent "fingerprints", which were further identified by pattern recognition methods. The proposed fluorescence sensor array achieved 100% accuracy in identifying various surfactants and multicomponent mixtures, with the detection limit in the range of 0.0032 to 0.0315 mM for six pollutants, which was successfully employed in the discrimination of surfactants in real environmental waters. More importantly, our findings provided a new avenue in rapid detection of surfactants, rendering a promising technique for environmental monitoring against trace multicontaminants.

Microfluidic paper-based analytical device with a preconcentration system for the measurement of anionic surfactants using an optode detector

The paper discusses the development of a low-cost, simple, and sensitive on-site measurement system for anionic surfactants (AS), specifically sodium alkylbenzene sulfonate (LAS), using a microfluidic paper-based analytical device (μPAD) with an optode as a detector. The need arises due to the discharge of AS-containing wastewater into natural environments, posing risks to aquatic organisms. Traditional methods for AS measurement have drawbacks like the use of harmful solvents, time-consuming procedures, and the need for expensive equipment, prompting the exploration of alternative approaches. The μPAD incorporates a sample solution preconcentration system using filter paper modified with chitosan. The optode, a chemical sensor detecting analytes optically, is employed for AS detection. When a large volume of AS is added to a positively charged modified filter paper with chitosan, the AS is adsorbed and concentrated on the filter paper. The concentrated AS is eluted with a small volume of alkaline solution, and the eluted AS is detected by the optode in the μPAD. The μPAD with preconcentration provides improved sensitivity and a broader range of detection compared to the method without preconcentration. In the present μPAD method, linear alkylbenzenesulfonate (LAS) in the concentration range of 0.1 to 10 μmol dm-3 was measured. The developed μPAD offers advantages such as portability, cost-effectiveness, and negligible interference from coexisting substances in environmental water samples. The μPAD method was applied for the determination of LAS in tap water and river water.

Method validation and environmental monitoring of triethanolamine ester quaternary ammonium compounds

In this study water and sediment samples, collected from the River Nene (Northamptonshire) at several sites in the vicinity of the Great Billing sewage treatment plant (STP), were analysed for triethanolamine quaternary compounds (TEAQ, ester quats). A method was developed using liquid chromatography tandem mass spectrometry (LC/MS/MS) with a electrospray ionisation source (ESI). Ten components were determined using a characterised commercial sample of Tallow TEAQ as a standard. To our knowledge this is the first time environmental concentrations of a wide spectrum of individual homologues of TEAQ have been reliably quantified covering a broad range of environmental matrices (STP influent, STP effluent, surface waters and sediments), due to the challenging nature of the analytical method. The method featured novel solutions for the determination of long and multiple chain length alkyl quats, controlling loss processes, background contamination and chromatographic performance. TEAQ compounds were found to be highly removed in the sewage treatment plant resulting in low effluent concentrations. Low concentrations in both river water and sediment samples were found also. In many cases levels were below the Method Detection Limit (MDL). In river water samples, mean values of TEAQ compounds found were 210-398 ng/L for C16:0/C18:0 TEAQ diester and 126-287 ng/L for C18:0/C18:0 TEAQ diester. River sediment was found to contain mean TEAQ levels of 7.07-12.5, 19.7 to 40.3 and 7.04-35.1 μg/kg dry weight for C16:0/C16:0, C16:0/C18:0, and C18:0/C18:0 TEAQ, respectively. At Great Billing STP monoesters and diesters of TEAQ were shown to be efficiently removed (>97 and 99 %, respectively), although limited samples were taken on this occasion.

Unveiling Coformulants in Plant Protection Products by LC-HRMS Using a Polyhydroxy Methacrylate Stationary Phase

A polyhydroxy methacrylate-based stationary reversed phase was used for the determination of coformulants in 20 plant protection products (PPPs). These samples were analyzed by liquid chromatography coupled to Q-Orbitrap high-resolution mass spectrometry (LC-Q-Orbitrap-HRMS) in full-scan MS and data-dependent acquisition (ddMS2) modes. A total of 92 coformulants were tentatively identified in these formulations by nontargeted and unknown analyses. Twelve out of them were quantified by analytical standards. The most concentrated coformulant was the anionic surfactant dodecylbenzenesulfonic acid, whose highest content was obtained in the Score 25 sample (6.87%, w/v). Furthermore, triethylene glycol monomethyl ether, 4-s-butyl-2,6-di-tert-butylphenol, 1-ethyl-2-pyrrolidone, sorbitan monostearate, 2,6-dimethylaniline, palmitamide, and N-lauryldiethanolamine were quantified for the first time in these products. Hence, the polyhydroxy methacrylate-based stationary phase increased the identification of new coformulants in PPPs, being complementary to conventional C18. This strategy could be applied in future studies to estimate potential coformulant residues from PPPs applied to crops.

Human metabolism and excretion kinetics of the surfactant 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) after oral and dermal administration

2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant with a wide range of applications. TMDD is considered a high-production chemical and, due to its low biodegradation rate, possesses a potentially high prevalence in the environment. However, despite its widespread use, toxicokinetic data and data on internal exposure to TMDD in the general population are completely lacking. Hence, we developed a human biomonitoring (HBM) method for TMDD. Our approach included a metabolism study with four subjects, who were administered an oral dose of 75 µg TMDD/kg body weight and a dermal dose of 750 µg/kg body weight. Terminal methyl-hydroxylated TMDD (1-OH-TMDD) was previously identified as the main urinary metabolite in our lab. The results of the oral and dermal applications were used to determine the toxicokinetic parameters of 1-OH-TMDD as a biomarker of exposure. Finally, the method was applied to 50 urine samples from non-occupationally exposed volunteers. Results show that TMDD was rapidly metabolized, with an average tmax of 1.7 h and a rapid and almost complete (96%) excretion of 1-OH-TMDD until 12 h after oral dosage. Elimination was bi-phasic, with half-lives of 0.75-1.6 h and 3.4-3.6 h for phases 1 and 2, respectively. The dermal application resulted in a delayed urinary excretion of this metabolite with a tmax of 12 h and complete excretion after about 48 h. The excreted amounts of 1-OH-TMDD represented 18% of the orally administered TMDD dose. The data of the metabolism study demonstrated a fast oral as well as substantial dermal resorption of TMDD. Moreover, the results indicated an effective metabolism of 1-OH-TMDD, which is excreted rapidly and completely via urine. Application of the method to 50 urine samples revealed a quantification rate of 90%, with an average concentration of 0.19 ng/mL (0.97 nmol/g creatinine). With the urinary excretion factor (Fue) derived from the metabolism study, we estimated an average daily intake of 1.65 µg TMDD from environmental and dietary sources. In conclusion, 1-OH-TMDD in urine is a suitable biomarker of exposure to TMDD and can be applied for biomonitoring of the general population.

SPE-UPLC-MS/MS for Determination of 36 Monomers of Alkylphenol Ethoxylates in Tea

Alkylphenol ethoxylates (APEOs) represent a non-ionic surfactant widely used as adjuvants in pesticide formulation, which is considered to cause an endocrine-disrupting effect. In the current study, we established a detection method for the APEOs residue in tea based on solid-phase extraction (SPE) for the simultaneous analysis of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) by UPLC-MS/MS. In the spiked concentrations from 0.024 to 125.38 μg/kg for 36 monomers of APEOs (n_EO = 3-20), the recoveries of APEOs range from 70.3-110.7% with RSD ≤ 16.9%, except for OPEO₂₀ (61.8%) and NPEO₂₀ (62.9%). The LOQs of OPEOs and NPEOs are 0.024-6.27 and 0.16-5.01 μg/kg, respectively. OPEOs and NPEOs are detected in 50 marketed tea samples with a total concentration of 0.057-12.94 and 0.30-215.89 µg/kg, respectively. The detection rate and the range of the monomers of NPEOs are generally higher than those of OPEOs. The current study provides a theoretical basis for the rational use of APEOs as adjuvants in commercial pesticide production.

Rapid determination of polyethoxylated tallow amine surfactants in human plasma by LC-MSMS

The potential exposure to the widely used glyphosate-based herbicides, including attempted suicide by ingestion, is of world-wide concern. Whilst the major focus to date has been on managing exposure to the active ingredient glyphosate, it is now recognised that a common major 'inert' surfactant ingredient, polyethoxylated tallow amine (POEA) and related compounds, may be more toxic. However, the information on the toxicokinetics of POEA surfactants after exposure is limited, in part, due to the lack of suitable methods for their analysis in biological matrices. We therefore developed and validated a robust LC-MSMS method that allowed, for the first time, a rapid analysis of 11 POEA homologues in human plasma. Chromatographic separation was achieved on a Kinetex EVO C18 column under a 5 min gradient elution with mobile phase A containing water/acetonitrile/formic acid (95:5:0.1, v/v/v) and mobile phase B containing acetonitrile/water/formic acid (95:5:0.1, v/v/v). Amlodipine was chosen as the internal standard (IS) for this assay. Amlodipine-d4 would be an ideal alternative IS to expand the applicability of the established method especially in antihypertensive patients. Multiple reaction monitoring (MRM) methods were optimized for 11 POEA homologues and the IS. Sample pre-treatment was performed using simple protein precipitation with methanol at a ratio of 4:1, requiring only 20 μL plasma. The validated method showed good specificity, accuracy and precision with lower limits of quantification (LLOQ) ranging from 0.35 to 10.8 ng mL^-1 for all selected POEA homologues. The method was then used to measure concentrations of the various POEA surfactants in more than 600 human plasma samples from 151 patients admitted to hospital with acute glyphosate intoxication. The highest concentrations ranged from 1.07 ng mL^-1 for C₁₈u(EO)₄-362.70 ng mL^-1 for C₁₆s(EO)₂. The analysis of POEA surfactants plasma concentrations as described here underpins the assessment of POEA internal exposure and the relationships between POEA related glyphosate toxicity and the extent of poisoning.

Determination of a specific metabolite for the non-ionic surfactant 2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) by UPLC-MS/MS

2,4,7,9-Tetramethyldec-5-yne-4,7-diol (TMDD) is a non-ionic surfactant commonly used as defoaming agent and numerous other applications. Effluents of wastewater treatment plants have been identified as one of the main sources of TMDD emissions into the environment. Due to its broad application in various fields, TMDD was selected for the development of a biomonitoring method for assessing human exposure within the frame of the cooperation project of the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB) and the German Chemical Industry Association (VCI) in 2020. This study aimed to identify a urinary metabolite for TMDD by UPLC-Q-Orbitrap-MS which can be used as a biomarker of TMDD exposure. Monohydroxylated TMDD (1-OH-TMDD) was deciphered as the most prominent metabolite of TMDD in humans in a series of in vitro and in vivo experiments. In a next step, a quantitative method for the determination of 1-OH-TMDD was developed and validated. Quantification was achieved by isotope dilution using D₃-1-OH-TMDD as internal standard. The method is characterized by a simple sample clean-up procedure and an enzymatic hydrolysis of possible metabolite conjugates with ß-glucuronidase. Method validation was performed according to international guidelines for bioanalytical method validation. The method proved its robustness, precision, accuracy and sensitivity for the intended purpose, i.e. the assessment of TMDD exposure in the general population by means of human biomonitoring.

Synthetic surfactants in Swiss sewage sludges: Analytical challenges, concentrations and per capita loads

Surfactants are high-production-volume chemicals that are among the most abundant organic pollutants in municipal wastewater. In this study, sewage sludge samples of 36 Swiss wastewater treatment plants (WWTPs), serving 32% of the country's population, were analyzed for major surfactant classes by liquid chromatography mass spectrometry (LC-MS). The analyses required a variety of complementary approaches due to different analytical challenges, including matrix effects (which can affect adduct ion formation) and the lack of reference standards. The most abundant contaminants were linear alkylbenzene sulfonates (LAS; weighted mean [WM] concentration of 3700 μg g^-1 dry weight), followed by secondary alkane sulfonates (SAS; 190 μg g^-1). Alcohol polyethoxylates (AEO; 8.3 μg g^-1), nonylphenol polyethoxylates (NPEO; 16 μg g^-1), nonylphenol (NP; 3.1 μg g^-1), nonylphenol ethoxy carboxylates (NPEC; 0.35 μg g^-1) and tert-octylphenol (tert-OP, 1.8 μg g^-1) were present at much lower concentrations. This concentration pattern agrees with the production volumes of the surfactants and their fates in WWTPs. Branched AEO homologues dominated over linear homologues, probably due to higher persistence. Sludge concentrations of LAS, SAS, and NP were positively correlated with the residence time in the anaerobic digester. Derivation of the per capita loads successfully revealed potential industrial/commercial emission sources. Comparison of recent versus historic data showed a decrease in NPEO and NP levels by one or two orders of magnitude since their ban in the 1980s. By contrast, LAS still exhibit similar concentrations compared to 30 years ago.

Identification of micropollutants from graywater of different complexity and remediation using multilayered membranes

Graywater reuse is one of the important concepts in attaining water sustainability. A major challenge in this area is to realize various components present in graywater. The present study involves the identification of the chemical components of graywater collected from three different environments and to investigate the efficiency of removal of some of these chemical components using ultrafiltration membranes (polyelectrolyte multilayer (PEM) membranes). The chemical components were analyzed using liquid chromatography connected with quadrupole time-of-flight (UPLC-Q-ToF-MS). A number of micropollutants including surfactants and certain contaminants of emerging concern (CECs) were identified from these samples. Out of 16 compounds identified, 13 were surfactants and the remaining were caffeine, oxybenzone, and benzophenone. These surfactants are mostly the ingredients of various detergents. Low-pressure filtration studies of the collected samples were carried out utilizing chitosan/polyacrylic acid (CHI/PAA) multilayer membranes. A 5.5 bilayer membrane showed more than 95% rejection of the identified compounds in the selected samples and significant improvement in the water quality parameters. This demonstrates that the membrane used in this work is effective in the removal of various chemicals from graywater as well as enhancing the water quality.

Ex-situ and in-situ rapid and quantitative determination of benzene derivatives in seawater using nanoconfined liquid phase nanoextraction

Benzene derivatives (BDs) constitute a class of environmental pollutants whose exposure poses a grave risk to human health. These compounds rapidly diffuse from the atmosphere to the marine ecosystem: for this reason, their monitoring in seawater is every day more compelling. In this work, nanoconfined liquid phase nanoextraction (NLPNE), a versatile extraction technique recently described, has been for the first time applied to the gas chromatographic mass spectrometry (GC/MS) analysis of BDs in seawater. Ex-situ and in-situ NLPNE procedures have been developed and optimized in terms of extraction capabilities, analysis time, precision, and accuracy. Compared to the traditional extraction procedures, based on solid-phase microextraction (SPME) and liquid-liquid extraction (LLE), the proposed NLPNE methods allowed a rapid on-site analysis of benzene compounds with low solvent consumption, higher enrichment factors, and improved automation grade. Determination coefficients ranging from 0.9929 to 0.9997 were obtained for all BDs in the range 0.10-500 ng mL^-1 and 5.00-500 ng mL^-1, for ex-situ and in-situ NLPNE, respectively. Ex-situ and in-situ limits of detection ranged from 0.2 to 7.6 ng mL^-1 and 0.04-1.00 ng mL^-1. Our results suggest that NLPNE coupled to GC-MS can be considered a powerful technique for high-throughput analyses of trace compounds in environmental, food and biological samples.