Validation and measurement uncertainty of spectrophotometric method in the determination of polyphosphates from meat products

According to the requirements of the standard EN ISO/IEC 17025: 2000, the testing laboratory shall use test methods, which meet the needs of the client and which are appropriate for the required testing. The methods proscribed by the international, regional or national standards shall be applied as methods of choice. The Laboratory - developed methods, non - standard methods or methods adapted by the laboratory may also be used if they are appropriate for the intended use and if they are validated. The testing laboratories shall have and shall apply procedures for validation and procedures estimating the uncertainty of measurement. The method validation studies rely on validation of the overall method performance parameters. These are obtained by the method of development of the following in house validation protocols. The validation study for this spectrophotometric method assumes the following parameters: selectivity, linearity, precision, detection limit and accuracy. Polyphosphates may be used in production of all sorts of sausages (with the exception of shelf-life sausages), canned meat, jelly food, meat salads and jelly which are normally thermally processed, as long as the final product does not contain more than 0,30% of added phosphates expressed as P2O5 (phosphorus penthoxide). The spectrophotometric method (gimel=890 nm) in the detection of polyphosphates in meat products is a reliable method developed by the laboratory for its own use. The measurement uncertainty of the results of the amount of polyphosphates in meat products was evaluated. The major sources of uncertainty of the result of measurement was identified as contribution from: the abundance of the samples, the volume of the flask, the repeatability, and the volume of the pipette... Identification and evaluation of sources of uncertainty was followed by a combined and expanded uncertainty calculations. For measurement value of 0.37% P2O5 there was determined a combined uncertainty of 0.006%. The expanded uncertainty, for a level of confidence of 95%; (k=2), is 0.012%. The greatest part in the combined uncertainty comes from the parameter of the volume of the pipette, and the "repeatability".