Abstract
Liquid polymeric membrane sensors based on the hydrophobic cationic surfactant methyltrioctayammonium chloride (MTOAC) are described herein for batch and flow injection analysis of sodium lauryl sulfate (SLS) surfactant. PVC-based membrane sensors were prepared using different plasticizers in two different electrode designs: conventional polymeric membrane discs for batch measurements and flow-through half cell module for flow-injection analysis. o-nitrophenyloctyl ether plasticized sensors exhibited the most distinguished response characteristics among other sensors in 10(-2) M phosphate buffer solution at pH =7, with a lower detection limit of 3.97x10(-7) M, a linear dynamic range of 9.33x10(-7) - 5.31x10(-3) M, a slope of -59.4 mV/concentration decade, a correlation coefficient of 0.999 and a response time of 60 s. The sensors were selective towards SLS over other common anions and exhibited a long life time (more than 2.5 months) with a constant detection limit, an enhanced linear range, and a slight increase in its slope. The fabricated sensors were efficiently used in the determination of SLS concentrations in a wide range of samples including powder detergents, tooth paste, liquid hand wash, and shampoo, and wastewater.