Journal of Chromatography A, 874 (2000) 207–215 www.elsevier.com / locate / chroma Determination of anionic surfactants during wastewater recycling process by ion pair chromatography with suppressed conductivity detection * Lanfang H. Levine , Jennifer E. Judkins, Jay L. Garland Dynamac Corporation, DYN-3, Kennedy Space Center, FL 32899, USA Received 9 November 1999; received in revised form 12 January 2000; accepted 26 January 2000 Abstract A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C –C ) ether sulfate] were 2|500, 10 16 1|500, 2.5|550 and 3.0|630 mg / ml, respectively.  2000 Elsevier Science B.V. All rights reserved. Keywords: Anionic surfactants; Wastewater recycling 1. Introduction has always been a challenge due to their foaming and amphiphilic nature and general lack of light ab- Surfactants are the active ingredients in household sorbance. detergents, industrial cleaning agents and personal Methylene blue active substances (MBASs) have care products. Surfactants used in personal care long been used as a standard method for measuring preparations account for an estimated 15–16% of the sulfonate and sulfate-based anionics in wastewater total surfactant consumption for the time period [2]. While this method is sensitive, with a detection between 1977 to 1992 [1]. Among the different types limit of 10 mg in a 100-ml sample, it is time- of surfactants, anionic surfactants are the most consuming and often interfered with by sample widely used as primary surfactants in personal care matrix. Substances such as organic sulfonates, sul- products. They are almost exclusively organic sul- fates, carboxylates and phenols and inorganic thio- fonates and sulfates with some being carboxylates cyanates, cyanates, nitrates and chlorides may trans- such as bar soaps. Accurate measurement of these fer more or less methylene blue into the chloroform surfactants in wastewater or environmental samples phase and result in positive interference. Negative interference can result from the presence of cationic surfactants and other cationic materials (e.g., *Corresponding author. Fax: 11-321-8534-220. E-mail address: lanfang.levine-1@ksc.nasa.gov (L.H. Levine) amines), because they compete with the methylene 0021-9673 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0021-9673(00)00155-2