The perils of RSL testing

The Toggler blog
Published:  01 February, 2014
The Toggler

I wrote in my most recent ILM column about value for money in RSL testing (RSL's  - Are we getting what we paid for?), which was published in the December/January edition. Following on from that article here is another issue relating to RSL’s for you to consider. 

One of the most frustrating things about RSL (Restricted Substance Lists) testing is when the laboratory gets it wrong. How can this happen? Easy – the same sample goes to two laboratories and different results come back to the tannery, or even worse the same sample is sent to the same laboratory and results come back differently.

Probably the most common issue relates to chromium VI. The leather passes one test and fails another. This is understandable for results around 3-5ppm Chromium VI, especially if one understands that the test method is working at the limit of detection ie 3ppm. 3ppm is as accurate as the test can be, sometimes for values in this area, the test will measure a bit above 3 (fail) and sometimes a bit below 3 (pass). This is due to variance; variance is a scientific thing. Variance in results means that every time you measure something it will not always give exactly the same answer, there will be some variation. Try this yourself, ask 10 people in a room the exact time and you will not get one answer! There is only one correct time but each watch may indicate a slightly different time, this is variance at its simplest. So chromium VI failures around the 3ppm level that pass one time and fail the next are just a fact of life that we have to live with. Some Brands build this into their systems.

Two different results

A much worse situation is when two results are significantly different and relate to one of the newer requirements for RSL testing. Many of these new “requirements” do not have recognised test methods and examples of widely different results (that cannot be correct) exist. The example above for chromium VI – everyone uses the same method: EN ISO 17075 (2007). But when (for example) APEO’s or short chain chlorinated hydrocarbons are tested – the methods used by different laboratories may be different. The method of extraction or detection may be different so it is no surprise that sometimes the results are different. The order of magnitude of some of these results would make one consider how reliable some methods are and begs the question, has any validation of test methods been carried out? Validation means have several laboratories used the same method to see if they get the same result. It is highly unlikely that this will have happened in the rush to get the business and with each laboratory claiming security of information/knowledge. The result is that the paying customer has to deal with the results some of which are incorrect.

In the event that you obtain an anomalous result, it should be taken up with the laboratory. All ISO17025 accredited laboratories (and most laboratories used by the global supply chain today are accredited to this standard) must have a non-compliance policy as part of their ISO17025 system. This means that if the customer’s requirements are not met (and two results for the same leather giving significantly different results are a matter of non-compliance) this should be taken seriously by the laboratory and they should offer both an explanation and detail how they intend to put it right.

The Toggler

thetoggler@internationalleathermaker.com

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