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.
Below are the most common products used for measurement of surfactants.
Spectrophotometers are available that have the anionic surfactant method pre-programmed into the meter. The spectrophotometer offers the highest precision due to the quality of the optical system that has a wavelength accuracy of +/- 1.5 nm. The spectrophotometer allows for custom methods to be used as well.
Benchtop photometers include multiparameter versions for water and wastewater treatment. Each photometer is customized to have the parameters used by a specific industry. The wastewater benchtop photometer is able to measure both anionic and nonionic surfactants. All benchtop have a digital pH electrode input allowing it to be used as a traditional pH meter.
A portable photometer is available to measure anionic surfactants. The portable photometers have a CAL Check feature that allows for performance verification, and if needed, recalibration using the CAL Check standards. The meters are available as a meter only option or as a kit. The kit version includes a rugged carrying case and CAL Check standards.
In this category are the anionic and nonionic surfactant reagents for the photometers.
Solutions for surfactant measurement include the CAL Check standards for verifying and, if needed, the calibration of our portable photometers. Each CAL Check standard is supplied with a Certificate of Analysis stating the accuracy and traceability of the standard.
Accessories include the replacement cuvettes and caps for the photometers.