The analytical determination of polyphosphates in food: A point-to-point comparison between direct ion chromatography and indirect photometry.

Being an indirect approach, the standard method for the determination of polyphosphates (PPs) in food maybe characterized by high variability which can lead to significant errors in the final measurement. In this study, this method was validated and then compared to the ion chromatography-based approach. Method trueness and measurement uncertainty resulted comparable, while the precision of ion chromatography approach was higher. No "false positive" responses were obtained from ion chromatography analysis, while indirect photometry may cause "false positive" results (5% of analyzed samples). Regarding "false negative" results, this possibility maybe verified for all food types tested and for seafood when using indirect photometry and ion chromatography, respectively. The percentages of "false negative" samples were equal to 23.3% for indirect photometry and 10% for ion chromatography. In conclusion, the indirect photometry is a reliable method especially as "screening technique", while ion chromatography maybe used as a confirmatory technique, successfully.