Proficiency Testing and Laboratory Performance in the Field of pH Measurement: An Indonesian Experiment

Proficiency testing (PT) for pH measurements for two consecutive years (2013 and 2014) in Indonesia have been conducted to discern the current condition of participant laboratories regarding their capacity on the pH measurement and to evaluate the effect on usage of the standard reference material. On 2013, two buffer solutions (phthalate and phosphate) and their corresponding standard reference solutions were distributed to the participant laboratory. While on 2014, the PT was conducted for citrate buffer solution but no corresponding standard reference solution was provided; thus the participant laboratory can used their own reference standard. The PT for both phthalate and phosphate buffer in 2013 were completed by involving 10 participant laboratories. In 2014, the PT was conducted with 90 participant laboratories. The PT results were evaluated based on ISO 13528:2005(E). From 10 participant laboratories on 2013, it was found that 80% of participant for phthalate buffer and a 70% of participant for phosphate buffer attain a satisfactory category. For the PT of citrate buffer on 2014, it was found that 54% of 90 participant have held a satisfactory category. Moreover, form the evaluation regarding the effect of standard reference material usage; it was found that a better result can be achieved by using a reference buffer solution from the RCChem LIPI as the PT provider rather than by using their own standard reference. Overall, it can be concluded that capability of the laboratory in Indonesia regarding pH measurement is needed to be improved by which more attention is given in term of the use and handling of standard buffer solution.