Question: Does light affect hydrogen peroxide and should I shield an assay/instrument from light when making accurate and precise hydrogen peroxide concentrations, especially at lower concentrations?
As with many things, the answer to this question is not simple, if your assay is optically based then the answer is 'of course', but for electrochemical assays the answer is it depends. Zimmer and Peacock are experts in assays involving hydrogen peroxide and we are happy to answer questions on this topic, so please feel free to contact us to discuss the parameters that might affect your assay.
Below we give an example where consistent light shielding was necessary.
Zimmer and Peacock have a number of technologies for hydrogen peroxide monitoring including the AL2021. Recently a collaborator noticed that their hydrogen peroxide concentrations dropped in the night. Zimmer and Peacock had supplied, installed and trained and so we went back on site to understand the nighttime phenomena.
The Zimmer and Peacock engineer noticed that the case/shielding was only partially on the instrument and within a few minutes was able to demonstrate to the customer that because they were working at very low hydrogen peroxide concentration the signal and the instrument had an increased susceptibility to light, and so the instrument needed to be calibrated with all the shielding in place and similarly run with the shielding in place.
Below we have included the direct comments from the Engineer's report '...I have been using the Aero-laser and noticed the importance of having the machine covered every time it is functioning. This includes calibration as well as measurements.
Basically, I noticed that, when measuring the ambient H2O2, the machine would record negative values during the night. This is due to me turning off the lights when leaving the lab/work for the day. I attached an image that shows a clear effect of the lights when the lid is off. The same is not noticeable when the lid in on.
I thought the photomultiplier was better protected from the light but, apparently, not. It does not mean that our measurements before were wrong, i.e., if we calibrated, and measured, with the lid off then it should be ok (just small fluctuations depending on LUX changes). However, if we are calibrating with the lid off and measuring with the lid on, there will be a difference that might result (for very low [H2O2]) in negative values. One could try to cover the photomultiplier with aluminum foil but the best is to use the Aero-laser with the lid/cover in place.