Sample preparation and photometric determination of nonionic surfactants in Extran® rinse solutions (MA 01, MA 02, MA 05, AP 22)
Many facilities are required to prove residue-free cleanliness of their lab equipment because any residues that remain after cleaning could affect the accuracy of analytical results. Extran® detergent can be used in such situations because it can provide residue-free cleaning and equipment can be tested for residues by a straightforward photometric test. Here we describe a procedure to analyze Extran® rinse solutions for residual detergent using the Spectroquant® Surfactants (nonionic) Cell Test Kit.
For further information on Extran® detergents please have a look at the brochure “Cleaner – Extran® Detergents – The perfect solution for cleaning your laboratory utensils” at www.SigmaAldrich.com/cleaning.
Nonionic surfactants (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 determined photometrically.
0.10 - 7.50mg/L Triton® X-100
For the measurement the following Spectroquant® test kit is necessary:
For the measurement one of the following Spectroquant® photometers is necessary (bold used for the development of this application note):
The sampling procedure depends on the material of the surface that is to be analyzed for residues:
The method for analyzing surfactants (nonionic) is pre-calibrated in our most current and old photometers. Programming data for other manufacturer’s spectrophotometers are available at http://www.sigmaaldrich.com.
For the nonionic surfactant analysis, 16-mm round cells must be used. For the verification of the handling, a Triton® X-100 Standard (reference substance for nonionic surfactants) is recommended. Detailed information on the preparation of standard solution can be found in the application "AQA Standard nonionic surfactants". Alternatively, this information can be found also in the manuals of the above-provided photometers.
Follow the instructions for use of the cell test. A clear phase separation must occur within the reaction time. An emulsion indicates too high Extran® concentrations in the tested sample.
This application gives an example of a possible procedure for cleaning validation. Nonionic surfactants adhere to most surfaces relatively well. This is the reason that it is essential to assure the absence of those substances. Ionic surfactants and phosphates are much easier to remove from the cleaning system by rinsing with water for analysis. Therefore, the absence of those substances doesn’t indicate the conclusion that the nonionic surfactants are not present. For this, it is essential to implement the sample preparation step before analysis. For the analysis system used, the method must be validated against a reference system in accordance with the current regulatory requirements (e.g., GMP, cGMP).
Analytical quality assurance (AQA) is recommended before each measurement series.
For more information visit us at SigmaAldrich.com/photometry
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