Thermo Fisher Scientific C101 Colorimeter - Manual (Page 21)

Measurement: Cyanuric Acid
C401/102 Colorimeter
17
Cyanuric Acid Measuring Hints & Tips
2.5.1 Sample Collection
Samples may be collected in either plastic or glass bottles. It is advisable
to wash the container with sample water before collecting the sample.
Do not store the sample for more than 24 hours before conducting the
analysis.
2.5.2 Sample Measurement
Due to the nature of the test method, concentrations less than 5 ppm
Cyanuric Acid are not detectable.
Clean the vial immediately after taking and recording a reading. Do not
leave the sample with added reagent into the vial for more than few
minutes after measurement. The test will cause the build up of a cloudy
layer on the inside wall of the vial. It is important to thoroughly clean the
vial after use to remove this layer because subsequent test results may be
affected.
2.5.3 Interferences
Sample Turbidity:
Turbid samples should be filtered prior to analysis.
2.5.4 Accuracy Check / User Calibration
A stock solution of 1000ppm Cyanuric Acid may be produced by dissolving
exactly 1g of Cyanuric Acid in 1 litre of de-ionised water (check the purity
of the Cyanuric acid being used; if less than 100%, adjust the amount
used accordingly).
The stock solution may then be diluted to give a Cyanuric Acid standard.
To do this take a portion of the stock solution and make up to 1 litre using
de-ionised water (for example, 50ml of stock solution will produce a
50ppm standard).
To check the accuracy of the meter: Prepare a standard in the range
20-80 ppm (it is advisable to check a standard at near the concentration
usually tested for using the meter). Use this standard in place of the
sample water in the above test method. The result obtained should be
approximately the value of the standard used (please refer to instrument’s
specifications for data on meter precision and accuracy).