Determination of anionic surfactants by flow injection analysis based on ion-pair extraction

Abstract

The ion-pair extraction of anionic surfactants by flow injection analysis (FIA) at a rate of 80 samples/h Is described.Methanol is used as a ion-pair solvating agent, both to enhance the extraction process and to vary the relative molar extractablllties of six different types of surfactants. A phaseseparating system was designed with poly(tetrafluoroethylene) (PTFE) porous membrane which is permeable to chloroform but impermeable to the aqueous solution. The method is suited in the range of up to 1.25 mM of the surfactant. Reproducibility of within 1.5% coefficient of variance was obtained.Several workers (1-8) have reported the automated determination of anionic surfactants in commercial products and natural waters. These methods were based on the ion-pair extraction of anionic surfactants with a cationic dyestuff such as methylene blue, followed by the AutoAnalyzer technique.

Submicrometric Magnetic Nanoporous Carbons Derived from Metal–Organic Frameworks Enabling Automated Electromagnet-Assisted Online Solid-Phase Extraction

“…[40][41][42][43] Furthermore, the proposed method just requires of 150 µL methanol as eluent, so using an organic solvent which is less toxic than the CHCl 3 used in the reference method and requiring an organic solvent volume per analysis approximately 300-fold lower. 38 The organic solvent volume used in the developed method is also much smaller than the required in other reported batch procedures (80 and 30-fold less volume, respectively), 44,45 Furthermore, in front of the 1.5 ml of sample used in the developed procedure, the official standard method requires up to 400 mL of sample to achieve similar levels of sensitivity, which makes more difficult the handling and storage of a large number of samples. Besides that, the combined use of advanced automated techniques, such as sequential injection analysis incorporating automatically actuated electromagnets allow safer handling and additional control over the use for SPE applications of small particles of complex magnetic materials, such µMNPC, allowing also further improvements in the extraction efficiency.…”

Extração líquido-líquido em sistemas de fluxo

“…O terceiro grupo, introduzido por Kawase e colaboradores 105 em 1979, têm sido preferido aos demais e pode ser utilizado com uma faixa mais extensa de solventes imiscíveis em água, porque a diferença de densidade entre as fases não é condição limitante do processo. Entretanto, a permeabilidade das membranas pode ser alterada na presença de agentes tensoativos e outras matrizes complexas, não sendo o tipo recomendável nestes casos 3,43,65 .…”

On-line sample treatment—capillary gas chromatography

“…Various types of phase separators are used in flow systems. Most of these are based on membrane separation [67,68] or on separation effected by gravity and wettability, such as, e.g. the sandwich phase separator [69].…”