QuantiChrom™ Detergent Assay Kit

What samples have been tested with this assay?

This kit has been tested with several varieties of handsoap, dish detergent, and powder clothing detergent.

You haven’t tested the detergent I am interested in measuring. Is my detergent compatible with the kit?

Since we haven’t tested every single detergent possible with the kit, there may be some which are not compatible. However, as long as it is not a bile acid it is likely to work. We have found that most lower detection limits tend to be the critical micellar concentration of the detergent (CMC) so if the detergent is compatible, the lower detection limit is probably the CMC. You should construct your own standard curve if you have a purified stock of the detergent, and can determine the concentration using this curve.

Can I use this assay with wastewater?

This assay has not been tested with wastewater. However, Dye B is commonly used to test wastewater for detergents although it requires several purification and extraction steps with a separatory funnel to remove interference. See https://doi.org/10.1002/j.1551-8833.1975.tb02144.x for more information.

Can I use this kit on a sample with multiple detergents in it?

If one detergent is anionic and another is cationic, you may. However, if both detergents are the same charge or are nonionic then they will both be measured by the assay and the true concentration of each cannot be determined. Thus it gives an overall detergent strength.

The OD of my detergent is linear for lower concentrations, then drops, then increases again. Why?

Yes, some detergents behave this way. It is recommended to create a standard curve of detergent that is linear and exclude the higher concentrations that are not linear.

My sample is cloudy. What is causing this interference with this assay?

Sodium deoxycholate and other bile acids precipitate out of solution with this assay and are cloudy, so cannot be used. Additionally, high concentrations of compatible detergents can cause cloudiness, so samples must be diluted to within detection limits.

My sample is colored, will this interfere with the assay?

You can run a background of 20 µL sample + 180 µL DI water to see if there is significant absorbance at OD560 or OD650 nm, and subtract this value from your sample when used with working reagent. You may also have to dilute your sample if detergent concentrations are too high, and this may help with reducing color.For more detailed product information and questions, please feel free to Contact Us. Or for more general information regarding our assays, please refer to our General Questions.