
Macro 900 Operation Manual
V3
© 2013 Palintest Ltd.
www.palintest.com
Page 74 of 147
Full two-point calibration should be carried out every few months.
15.4.4.
Calibration Solution Preparation
In order to 'calibrate' (actually, set the relative sensitivity) of the CPHYLL
probe, a 500µg/L calibration solution of fluorescent dye known as Rhodamine
WT should be used.
Please note: there is no direct correlation between Rhodamine concentration
and the concentration of chlorophyll. Rhodamine is used as a convenient dye
for setting the sensitivity of the sensor. The subsequent display of chlorophyll in
terms of mg/L is a generalisation based on research and experience. The only
way to obtain a true value in terms of cells/L is to correlate the values from the
Probe to quantitative data that has been obtained by laboratory analysis of grab
samples. See previous 'Limitations of Use' section.
The 500µg/L calibration solution should be freshly prepared by serial dilution
from 200g/L standard using deionised water. The following Rhodamine WT
standard is recommended:
Part number: 70301027
Description: Rhodamine WT Liquid
Supplier: Keystone Europe Ltd.
Be sure to handle chemicals with care and to read and comply with all
health and safety advice.
15.4.5.
Serial Dilution
The recommended Rhodamine solution is supplied as a 20% or 200g/L solution,
dilution of the stock solution should be carried out as follows.
200g/L stock
→
5
00μg/L is recommended to be done as a
two-step dilution
procedure.
Step 1:
weigh out 0.5g of 200g/L stock solution in a weigh boat and add this to
1L of deionized water in a volumetric flask, use some of the water from the 1L
flask to rinse the weigh boat so no stock Rhodamine remains on the boat. Put
a lid on the 1L flask and invert 10 times.
This step results in a 1 in 2000 dilution of the stock, at this point the 1L flask
will contain a 100mg/L solution.
Step 2:
Transfer 5ml of the 100mg/L solution to a 1L volumetric flask and top
up to 1L with deionized water. Put a lid on the 1L flask and invert 10 times.
This step results in a 1 in 200 dilution of the solution from step 1. The
concentration of this solution is 500μg/L. This solution can now be used as Pt
-2
calibration of the CPHYLL sensor.
The dilute solution can be stored in a dark bottle in a refrigerator for up to five
days. After that time it must be discarded.