engleski

Importance of measurement uncertainty in the determination pH value in culture media

Background: Testing laboratories determine control procedures of culture media prepared from dehydrated base as well as the ways to control technological processes of preparation according to EN ISO 11133:2014 and EN 12322:2008. An accreditation of a laboratory conducting certain tests contributes to improving the quality of each laboratory. Therefore, when we say that we did an analysis in an accredited laboratory, we can have confidence in the quality of the lab's work because the work of that laboratory is carried out in accordance with certain quality norms. Objectives: The aim of the study was measure the pH using a pH meter according to ISO 7218 and ISO 8199 in the preparation of culture media the Tryptic Soy Agar (TSA). Methods: The pH value is determined using direct method with pH-meter, 827 pH lab. The pH standard quantification is carried out by use of calibration curve and results are expressed in pH units. The validation of the method is executed over 10 days, with three 2-level neasurements per day. For the purpose of assessing uncertainty in measurement and calculation of the combined and extended uncertainty the data obtained from the method validation (reproducibility, accuracy), calibration curve, of preparation culture media TSA from dehydrated commercial formulations. Results: The comparison of relative standard uncertainty makes it evident that the most significant input to measurement uncertainty derives from the calibration curve and long-term reproducibility. All these are mechanisms that have an impact on the improvement and quality assurance of work in microbiological laboratories.

culture media ; measurement uncertainty ; pH value

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