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AOAC 955.16

Chlorine available in Disinfectants

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AOAC 955.16 – Chlorine available in disinfectants

AOAC 955.16 also known as the “chlorine equivalency method”, and outlines a test used to determine the amount of a test substance that matches the germicide efficacy of a confirmed effective level of free chlorine i.e. sodium hypochlorite. It is designed for testing disinfectants and sanitising rinses utilized within the food processing industry.

AOAC 955.16 Test Method

  • Standard chlorine solutions with concentrations of 200 ppm, 100 ppm, and 50 ppm are prepared as a reference for comparison with the test substance.
  • A timer is started, as the test microorganism is introduced into the 200 ppm standard chlorine solution.
      1. After 1 minute, a 4 mm sterile loop is used to move a small portion of the solution into a subculture tube.
      2. After 1.5 minutes, more of the test microorganism is added to the standard chlorine solution.
      3. At 2.5 minutes, another transfer of the solution is made to a subculture tube
  • This process of adding the test microbe culture and transferring the solution to a subculture is repeated 10 times.
  • The remaining standard chlorine solutions and the test solutions are subjected to the same procedure.
  • All subculture tubes are incubated at 36°C for 48 hours.
  • The subculture tubes from the standard chlorine solutions are checked for growth and compared to the subculture growth of the test substance solutions in order to determine the chlorine activity equivalent of the test substance.
  • The test microorganisms should display similar growth in consecutive tubes as observed in standard solutions.

Importance of AOAC 955.16 Test

AOAC 955.16 testing is generally used to test the germicidal efficacy of halogens such as chlorine, bromine, and iodine. This standard test method is able to determine chlorine equivalents of test substances over a wide range of available chlorine concentrations. Hence, it’s an EPA preferred method for validating claims of halide-based sanitizers and disinfectant products used in the food processing industry.

Why Trust Us for AOAC 955.16 Test

At MIS, all the tests are carried out in accordance with the standard operating procedure and our microbiologists and chemists can also design a protocol according to your needs and expectations. We have excellent infrastructure and a fully equipped laboratory with the latest technology to perform AOAC tests. 

To get more information regarding the AOAC 955.16 test and other disinfectant testing methods, reach out to our experts here.


The AOAC 955.16 test, also known as chlorine in disinfectants germicidal equivalent concentration, provides efficacy data that shows the equivalent performance of test product equivalent concentrations to sodium hypochlorite.

AOAC 955.16 test is applicable to halide-based sanitisers and disinfectant products.

The AOAC 955.16 test takes 4-5 days to complete.

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