Jenway 6715 - Manual (Page 30)

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g) All sample containers must be handled with care; by the top and non-optical surfaces only. Any
finger marks evident must be removed using a suitable cleaning process.
h) Flow-through cuvettes must be selected with care and consideration for the sample type, sample
volume, pumping system, rinse, sample and waste handling to be used.
5. Samples and standards should not be stored in open cuvettes or sample containers as evaporation
will change the value and lead to staining of the walls which may be irreversible. If stored in stoppered
and sealed cuvettes, they should be filled with little or no air space and the values regularly checked
against a reference standard or quality control material.
6. Cold samples should be allowed to equilibrate to ambient temperature before measurement (unless
a suitable temperature controlled sample holder is in use). Temperature change during measurement
may cause air bubbles to form on the walls of the sample holder. This is a common cause of drift
during measurement.
7. In the preparation of samples and standards high grade borosilicate glass and AR grade chemicals
and reagents must be used. Good quality deionised water or other suitable solvent must be used for
dissolving or diluting samples, chemicals and reagents.
8. All measurements require calibration to a blank, for maximum accuracy this should be prepared
with care using the same deionised water or solvent used for dissolving or diluting the sample. Where
reagents are added to the sample to produce a colour proportional to its concentration a ‘sample
based’ blank should be used. In this case the blank should consist of the sample plus any reagents or
chemicals to be used,
except those that produce the colour to be measured.
9. Deviations from the Beer-Lambert Law may occur at high and low concentrations giving non-linear
response during sample concentration measurements. For all new methods a linear range should be
defined by the preparation of a calibration curve. The quantitation mode may be used to construct
such a curve against which sample results are automatically measured.
10. Cuvettes and sample holders must be filled to a minimum level which covers the light path.