Surfactant is a combination of the words surface active agent. Surfactants are compounds that lower the surface tensions between liquid-liquid, liquid-gas, and liquid-solids.

Surfactants are present in waters and wastewaters. Surfactants are discharged via aqueous waste from households, industrial laundering, and other cleansing operations. Generally present in detergents and other cleaning agents, a surfactant molecule consists of a strongly hydrophobic tail and a strongly hydrophilic head, permitting solubility in both aqueous and non-aqueous media. When the hydrophilic head is negatively charged, it is deemed an anionic surfactant; when the hydrophilic head is positively charged, it is deemed a cationic surfactant. When hydrophilic head has no charge then it is a non-ionic surfactant.

Hanna offers multiple chemical methods for the measurement of surfactants. Methods for measuring surfactants include anionic surfactants as SDBS and non-ionic surfactants as Triton X-100.

The anionic surfactant method is an adaptation of the USEPA method 425.1 and Standard Methods for the Examination of Water and Wastewater 20th Edition, 5540C, Anionic Surfactants as MBAS. In this method methylene blue reagent is added to samples containing anionic surfactants, the sample will turn a blue hue; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law.

For non-ionic surfactants a TBPE method is used in which ethoxylates with 3 to 20 ether bridges react with an indicator (TBPE) to form a complex that is then extracted with dichloromethane. The green color of the organic phase is then determined photometrically.

Available technologies to measure anionic surfactants include spectrophotometers, benchtop photometers and portable photometers. A benchtop photometer is available to measure non-ionic surfactants.


Accessories include the replacement cuvettes and caps for the photometers.