Metrohm NIRS XDS Transmission OptiProbe Analyzer - Manual (Page 31)

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Vials are inserted as shown. Normally the operator
will use latex gloves, both for safety and to avoid
fingerprints on the vial.
The Vial Heater Module is designed for 300 micro-
liter “Clear Round Bottom Vials, 8mm Crimp”.
Always follow these safety guidelines when handling sample materials:
• Always use appropriate safety equipment with hazardous materials, to prevent injury. This
equipment may include safety glasses, gloves, lab apron, and fume hood.
• Always check the MSDS (Material Safety Data Sheet) for the materials being analyzed for
recommended handling precautions.
5.3 Liquid Sampling Considerations
The XDS OptiProbe Transmission Analyzer is capable of detecting low levels of analytes in liquids. A
brief overview of absorbance and pathlength considerations on a simple type of sample may be
helpful.
A suitable pathlength must be selected for the sample, in expected concentration levels. This
pathlength must be long enough that the analyte material absorbs energy, and also must be short
enough that the absorption is not masked by other factors.
First, determine the wavelength areas for analysis. Take spectra of the pure materials to see where
the absorptions occur, without confusion from other components of the sample matrix. Much of this
work should be done using cuvettes for ease of handling.
Once the possible wavelength areas are determined, the sample should be run in at different
pathlengths to determine what pathlength gives the optimum analytical results. The example below
illustrates some of the initial steps in this process.
In this example, we wish to measure 2-propanol in water, at concentrations up to 25% of 2-
propanol. We take spectra of each material, to see where the absorbances occur.