LaMotte SMART3 Colorimeter - Manual (Page 14)

 REAGENT BLANK
Some tests will provide greater accuracy if a reagent blank is determined to
compensate for any color or turbidity resulting from the reagents themselves. A
reagent blank is performed by running the test procedure on demineralized or
deionized water. Use sample water to SCAN BLANK. Insert the reacted reagent
blank in the colorimeter chamber and select SCAN SAMPLE. Note result of
reagent blank. Perform the tests on the sample water as described. Subtract
results of reagent blank from all subsequent test results. NOTE: Some tests
require a reagent blank to be used to SCAN BLANK.
 COLORIMETER TUBES AND CHAMBER
Colorimeter tubes and colorimeter chambers which have been scratched
through excessive use should be discarded and replaced with new ones. Dirty
tubes should be cleaned on both the inside and outside. Fingerprints on the
exterior of the tubes can cause excessive light scattering and result in errors.
Handle the tubes carefully, making sure the bottom half of the tube is not
handled.
LaMotte Company makes every effort to provide high quality colorimeter tubes.
However, wall thicknesses and diameter of tubes may still vary slightly. This may
lead to slight variations in results (e.g. if a tube is turned while in the sample
chamber, the reading will likely change slightly). To eliminate this error put the
tubes into the sample chamber with the same orientation every time.
The tubes that are included with the colorimeter have an index mark to facilitate
this. If possible, use the same tube to SCAN BLANK and SCAN SAMPLE.
 METER CARE
The optical system of the SMART3 must be kept clean and dry for optimal
performance. Dry the colorimeter tubes before placing them in the chamber to
avoid introducing moisture. For best results store the instrument in a area that is
dry and free from aggressive chemical vapors.
 SELECTING AN APPROPRIATE WAVELENGTH
The most appropriate wavelength to use when creating a calibration curve
is usually the one which gives the greatest change from the lowest reacted
standard concentration to the highest reacted standard concentration. However,
the absorbance of the highest reacted standard concentration should never
be greater than 2.0 absorbance units. Scan the lowest and highest reacted
standards at different wavelengths using the absorbance mode to fi nd the
wavelength which gives the greatest change in absorbance without exceeding
2.0 absorbance units. Use this wavelength to create a calibration curve.
12 SMART3 Colorimeter 02.12