Metrohm NIRS XDS MasterLab Analyzer - Manual (Page 31)

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5.1 Introduction to Tablet Analysis
The MasterLab Analyzer is designed to provide
sampling for trays of tablets, like that shown at
right. This provides for a great degree of
automation, and permits the operator to perform
sample loading and other duties while one tray is
being scanned by the instrument.
This extends the usefulness of the instrument
into a routine analytical tool, since no operator
input is required, once the sample information is
entered and the tray is in place.
Spectral information for each tablet is acquired and stored, and the calibration or library identification
is automatically applied.
Transmission sampling is preferred when the core of the tablet is of primary interest. The transmission
detector must be in the proper position over the tray, and the aperture must be positioned over the
sampling window to narrow the beam. In transmission, the instrument scans from 800 to 1650 nm,
where the NIR energy is best able to penetrate thick tablets. Note that transmission detector height is
adjustable, to accommodate thick tablets. While this feature is notable, the user should always
document the height setting for a given type of tablet, and return the detector height to that same
setting for subsequent analysis. Failure to do so may result in inaccuracy. A vernier height adjustment
is provided to facilitate correct height. A locking screw maintains setting height for consistency.
Reflectance sampling is often used to study the tablet coating, or the tablet core near the surface of
the tablet. Reflectance is also useful for discriminating between polymorphs, which may appear
similar at lower wavelengths, yet are very visible in the higher wavelength areas. This mode uses
detectors beneath the sample window. The transmission detector may be rotated (clockwise, 90
degrees) out of the sampling position when using reflectance.
Partial trays may be run, with the order of scanning determined by the user. Vision provides easy
graphical tools to make setup easy and accurate. No special software skill is required to set up the
instrument for routine analysis, once the calibration is in place.
Because the MasterLab Analyzer may be used with different size tablets, Vision accommodates setup
by offering a screen to help define the tray dimensions, including tablet (or vial) spacing. The number
of columns and rows of tablets (or vials) is entered, along with the manufacturer’s nominal diameter
and tolerance. Vision takes this information and provides centerline data for each bored hole in the
tray, which can be used for machining.
The Table of Contents separates most analysis functions by “Reflectance” or “Tablet Transmission”.
We suggest the user start with one mode and follow it through to completion before starting the
next mode. This approach allows mastery of one mode before learning the next.
The MasterLab also operates as a vial analyzer in reflectance. The transmission detector should be
rotated out of the tablet sampling position, to permit vial clearance. The maximum vial height with
this instrument is approximately 70 mm. (2.75”).
There are multiple default “vial” sizes set up in Vision, for commonly-used vials and tablet layouts.
In the case of tablet analysis, the layout (example: “4 x 5”) is the important selection criteria. Note