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

Abstract

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.

Environmental monitoring study of linear alkylbenzene sulfonates and insoluble soap in Spanish sewage sludge samples

“…The liquid chromatographic analysis was also carried out according to the above mentioned methodologies. [21,22] In short, 100 µL of the final solutions were injected into the chromatographic system. Analytical separation of soap was performed on a LiChrospher-100 RP-8 analytical column (250 mm x 4 mm I.D., 5 µm particle size) coupled with a 15 mm safeguard column.…”

“…[21] Briefly, five grams of sewage sludge sample were thoroughly weighed in a microwave assisted extraction vessel, suspended in 25 mL of methanol, and treated as follow. The suspension was extracted for 25 min (20 min for holding, 70 bars, 1600 W) at 105 • C. Afterwards, 10 mL of the well-separated liquid extract was evaporated in a heater (80 • C, 30 min) and 1 mL of methanol/water (40:60, v/v) solution was added to dissolve the dry extract.…”

Analysis of Surfactants in Environmental Samples by Chromatographic Techniques

“…Some surfactant classes (e.g., LAS and NPEOs) and their metabolites are still good candidates, due to the presence of an aromatic ring in their molecular structure, to be analyzed by the first quantitative methods based on the use of HPLC coupled to ultraviolet (UV) or fluorescence detectors (FL) [68,66,126,129,130]. The presence of a benzene group also facilitates the use of UV for identifying some specific cationic surfactants such as benzalkonium chlorides (BACs) [97].…”

Quantificação de alquilbenzeno linear sulfonato em estação de tratamento de efluentes e rios por cromatografia líquida de alta eficiência e extração em fase sólida

“…10,[18][19][20][21] A extração do LAS de lodo e sedimento de rio pode ser realizada pela extração líquida pressurizada, extração assistida por micro-ondas, ultrassom ou Soxhlet. 20,22,23 A concentração do LAS, quando abaixo do limite de quantificação do método cromatográfico, é realizada pela evaporação de uma alíquota adequada da amostra e o resíduo é redissolvido com um volume e proporção adequados de uma solução metanol:água. Ou ainda, pela extração em fase sólida (SPE -solid phase extraction), que também atua na remoção de interferentes que coeluem com os homólogos do LAS, utilizando as colunas de troca aniônica muito forte (SAX -strong anionic exchange) e fase reversa octadecilsilano (C 18 ), já que o LAS possui na sua estrutura uma porção não polar, a cadeia alquílica, e outra polar, o grupo fenilsulfonato, fazendo com que ele seja retido nas duas colunas.…”

“…Ou ainda, pela extração em fase sólida (SPE -solid phase extraction), que também atua na remoção de interferentes que coeluem com os homólogos do LAS, utilizando as colunas de troca aniônica muito forte (SAX -strong anionic exchange) e fase reversa octadecilsilano (C 18 ), já que o LAS possui na sua estrutura uma porção não polar, a cadeia alquílica, e outra polar, o grupo fenilsulfonato, fazendo com que ele seja retido nas duas colunas. 4,5,9,20,[23][24][25] Dada a crescente preocupação sobre a presença de LAS em amostras ambientais, líquidas e sólidas, e levando-se em conta o maior uso de tratamento anaeróbio para esgotos sanitários, bem como os avanços nos estudos sobre a sua biodegradabilidade, é importante que a sua concentração seja quantificada por método analítico adequado. O objetivo do trabalho foi implantar uma metodologia empregando CLAE e SPE para a quantificação de LAS em afluente, efluente e lodo de ETE e em água e sedimento de rio.…”