Abstract
The measurement error generated by non-ionic detergents (Brij 35 and Triton X-100) in nine commercial pH test strips [thymol blue (TB), bromophenol blue (BPB), bromocresol green (BCG), bromocresol purple (BCP), bromothymol blue (BTB), methyl red (MR), phenol red (PR), cresol red (CR), alizarin yellow (AZY)] was investigated. A false negative error was produced by the detergents. The measurement error rates, which were proportional to the detergent concentration, were high in BTB, BCG, BCP and BPB in the presence of Brij 35, and in BTB and BCG in the presence of Triton X-100. The measurement error rates in PR, CR, MR, and AZY were low. The measurement error rate tended to correlate with the molecular weight of the pH indicator.
