Near-infrared spectroscopy prediction error

Near-infrared spectroscopy is quickly becoming a preferred technique for the quantitative identification of an active component within a formulated tablet. In addition, the same spectroscopic measurement can be used to determine water content since the combination band of water displays a fairly large absorption band in the near-IR. In one such study [41] the concentration of ceftazidime pentahydrate and water content in physical mixtures has been determined. Due to the ease of sample preparation, near-IR spectra were collected on 20 samples, and subsequent calibration curves were constructed for active ingredient and water content. An interesting aspect of this study was the determination that the calibration samples must be representative of the production process. When calibration curves were constructed from laboratory samples only, significant prediction errors were noted. When, however, calibration curves were constructed from laboratory and production samples, realistic prediction values were determined ( 5%). 

For brevity, results from selected in vitro and in vivo studies employing either near-infrared absorption spectroscopy or Raman spectroscopy, the most commonly used techniques, are documented in Tables 12.1 and 12.2. In these tables, error estimates are reported with either CV or P in parentheses, indicating cross-validated or predicted results, respectively. For an explanation of these terms, please refer to Section 12.4. 

Figure 10 NIR-predicted serum glucose levels vs reference assays (see also NIR B in Table 4). Open circles correspond to the calibration (training) set, solid circles to the validation (test) set, and the solid line is the line of identity. A Clarke error grid(3°) is superimposed, distinguishing regions corresponding to clinically safe analytical errors (regions A, B) from analytical errors that would result in dangerously inappropriate clinical decisions (C, D, E). (Adapted from K.H. Hazen, M.A. Arnold, G.W. Small, Measurement of Glucose and Other Analytes in Undiluted Human Serum with Near-infrared Transmission Spectroscopy , Analytica Chimica Acta, 255-267, Vol. 371, 1998, with permission from Elsevier Science.)...

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