At FoodSense we have a HPLC and it is through the use of this instrument that we have discovered an inconsistency between labs with regard to the HPLC detection of capsaicin.
Over the years we have realized that the precision of the ASTA method can be good within a lab but the absolute value of a sample between labs can often be variable.
One company that we spoke to in the US tested their sauces on their HPLC in their labs and got a score of 5000 SHU. When the same sauces were subsequently tested by a customer using their lab and their HPLC the customer reported 15,000 SHU. The issue that we see is that individual labs may be precise but the accuracy between labs is not necessarily high.