These practices cover a guide for the multivariate calibration of
infrared spectrometers used in
determining the physical or chemical characteristics of materials.
These practices are applicable
to analyses conducted in the near infrared (NIR) spectral region
(roughly 780 to 2500 nm) through
the mid infrared (MIR) spectral region (roughly 4000 to 400
NOTE 1 - While the practices described herein deal specifically with
mid- and near-infrared
analysis, much of the mathematical and procedural detail contained
herein is also applicable for
multivariate quantitative analysis done using other forms of
spectroscopy. The user is cautioned
that typical and best practices for multivariate quantitative analysis
using other forms of
spectroscopy may differ from practices described herein for mid- and
Procedures for collecting and treating data for developing IR
calibrations are outlined.
Definitions, terms, and calibration techniques are described. Criteria
for validating the
performance of the calibration model are described.
The implementation of these practices require that the IR spectrometer
has been installed in
compliance with the manufacturer's specifications. In addition, it
assumes that, at the times of
calibration and of validation, the analyzer is operating at the
conditions specified by the
These practices cover techniques that are routinely applied in the
near and mid infrared spectral
regions for quantitative analysis. The practices outlined cover the
general cases for coarse
solids, fine ground solids, and liquids. All techniques covered
require the use of a computer for
data collection and analysis.
These practices provide a questionnaire against which multivariate
calibrations can be examined to
determine if they conform to the requirements defined herein.
For some multivariate spectroscopic analyses, interferences and matrix
effects are sufficiently
small that it is possible to calibrate using mixtures that contain
substantially fewer chemical
components than the samples that will ultimately be analyzed. While
these surrogate methods
generally make use of the multivariate mathematics described herein,
they do not conform to
procedures described herein, specifically with respect to the handling
of outliers. Surrogate
methods may indicate that they make use of the mathematics described
herein, but they should not
claim to follow the procedures described herein.
This standard does not purport to address all of the safety concerns,
if any, associated with its
use. It is the responsibility of the user of this standard to
establish appropriate safety and
health practices and determine the applicability of regulatory
limitations prior to use.
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