THPI elutes as a single peak in just over 2 min; the response is sufficient for detection of 0.2 ng of THPI.
Results from triplicate determinations at each spike level (0.05, 0.10, and 0.20 ppm THPI in milk) gave recoveries between 70.0 and 87.7 % (Table 1). Table 1 Recovery of THPI from spiked milk samples. Spike level [ppm] Recovery [%I 0.05 80.4 71.7 74.5 0.10 72.4 79.0 70.0 0.20 87.7 84.4 83.3 Mean (n = 9) = 78.2 % Relative standard deviation (n = 9) = 8 0 % Samples for each individual spike level were run a t different times and two analysts working separately were involved in acquiring the data. The relative standard deviation of 8.0 % for the 9 determinations is satisfactory. Mass spectral confirmation of the identity of THPI was achieved using an ion trap detector. a b C 4 Conclusion A need has been established for a rapid and reliable method to determine THPI in milk. This procedure utilizes solid phase extraction to reduce solvent consumption and sample preparation times in comparison with previous procedures. THPI is quantified at levels down to 0.05 ppm in whole milk via nitrogen-phosphorus detection without derivatization. Four or more determinations can be completed in 8 hours by one analyst. D V. Reed (Ed.