A method for measuring potency of narasin extracts using near-IR spectroscopy

We present a method for extracting the active component from granulated nar asin samples using chloroform with subsequent quantitation by near-infrared absorption spectroscopy (NIRS). A multiple linear regression (MLR) calibra tion equation was developed using a set of 41 calibration samples. The pote ncies obtained using NIR analysis exhibit no larger than an 8% (3.03 mg/g) error when compared to results based on the primary HPLC reference method. We estimate the detection limit using this method to be 400 ppm narasin (20 mg/g potency), and the standard deviation for five independent extractions of the same sample is approximate to 24 ppm (approximate to 1.2 mg/g poten cy or approximately 1%). We also present the results from a robustness stud y based upon a full factorial experimental design in which we varied extrac tion and measurement parameters. This study indicates that sample mass caus es the most variation in the results. Bottle-to-bottle variations in the ch loroform used for the extraction also proved significant. Variations in sam ple batch, number of spectral scans, and the interactions between sample ba tch*soneration time, no. Scans*time in NIR, and sample batch*sample mass we re borderline significant. (C) 2001 Elsevier Science B.V. All lights reserv ed.