Rapid Tests

What are the options for testing free chlorine when superchlorinating fresh produce?

When fresh produce like salad products are processed, the disinfection is often performed by adding hypochlorite solution to the wash water.

Several standards state this must be maintained at 50mg/L or greater concentration – a very high level in terms of measurement for quality control.

Palintest offer two methods which are able to detect chlorine at such high levels for ongoing quality control monitoring during the washing of fresh produce.

superchlorination monitoring by Palintest
Palintest’s 2 options for testing very high range chlorine during superchlorination – the high chlorine solutions used to wash and disinfect fresh produce

Washing Fresh Produce

The high chlorine concentrations of 50mg/L or more used in the wash water for fresh produce is often referred to as “superchlorination”.

The levels aim to avoid the formation of chloramines (or combined chlorine) which are formed when free chlorine reacts with nitrogenous compounds like ammonia. Chloramines are much weaker disinfectants than free chlorine.

There isn’t currently a perfect way to measure the free chlorine at superchlorination levels, but Palintest offer 2 options which can provide a test solution.


This method relies on an electrochemical technique called chronoamperometry, and includes and instrument and a disposable, pre-calibrated sensor.

ChloroSense Palintest
The ChloroSense unit by Palintest for reagent and glass free high range chlorine testing

The test is fast, simple and doesn’t need messy reagents or powders so it allows non-technical users to rapidly read accurate results.

The device provides a free chlorine reading up to 10mg/L, so superchlorinating users will need to use the total chlorine reading (up to 100mg/L) to demonstrate the levels have been reached.

The ChloroSense system is glass and reagent free, so is ideal for use in production areas, high care environments, or GMP sites where contamination of product is a concern.

Chlorometer Duo

The second option Palintest offers is the Chlorometer Duo – this is a colorimetric version of a standard method, and allows total chlorine readings up to 250mg/L, again enough to demonstrate superchlorination has been achieved.

chlorometer duo palintest
Chlorometer Duo meters for low and high range chlorine testing

The DPD method has been the standard method for determining free and total chlorine in water for over 50 years.

This method does involve tablet reagents and requires a little more work from the tester, but is available at lower cost than the ChloroSense unit.


For more information on either test method, follow the links above or contact us if you have any questions;