Determination of surfactants in environmental samples. part ii. anionic compounds

Abstract

Surface active agents (SAA) with negative charge of polar group are named as anionic compounds. They are the main constituent of most products containing synthetic surfactants. The linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) are typically applied from this class of compounds. Those surfactants are ingredients of household detergents and cleaners, laundry detergents, cosmetic etc. Moreover they can be applied in the paper, textile and tanning industry as optical brighteners, dispersant, wetting and suspending agents. They can be substrates in the formulation of different products like dyes, pigments, pesticides, exchange resins, plasticizers and pharmaceuticals. Anionic surfactants after use are passed into sewage-treatment plants, where they are partially degraded and adsorbed to sewage sludge (applied in agriculture fields). Finally, the anionic SAA or their degradation products are discharged into surface waters and onto bottom sediments, soils or living organisms. Therefore, it is important (widely application, bioaccumulation, toxicity for living organisms) to investigate the environmental fate of those class of compounds in more details. This research involves determination the concentration of anionic surfactants with use appropriated analytical techniques in environmental samples The official methodology for determination of anionic SAA in liquid samples is based on the ion-pair reaction of these analytes compounds with methylene blue (MB) and an extraction with toxic solvent chloroform. During isolation step of anionic compounds from solid samples are employed Soxhlet and ultrasonic-assisted extraction techniques with use of methanol or mixture of other organic solvents as extraction medium. To overcome disadvantages of those traditional techniques were applied following techniques at sample preparation step from liquid and solid matrices: solid-phase extraction (SPE) and solid-phases microextraction (SPME); accelerated solvent extraction (ASE), microwave-assisted extraction (MAE), supercritical fluid extraction (SFE), respectively. For estimate total concentration of anionic analytes in extracts the spectrophotometric technique is used (as official regulation). For determination concentration of individual analytes were applied gas (derivatization step requires) and liquid chromatography mainly with mass spectrometry technique. The presence of anionic surface active agents was confirmed in various ecosystems (liquid and solid environmental samples).