YSI 600DW-B Sonde - Manual (Page 232)

Principles of Operation Section 5
Use the following procedure to prepare a Rhodamine WT solution for use as a sensor stability check reagent.
1. Rhodamine WT dye is usually purchased in solution form and can vary somewhat in nominal
concentration. YSI uses Rhodamine WT from the supplier noted below and recommends that the user
purchase this exact item if possible. The solution is approximately 2 % in Rhodamine WT.
Fluorescent FWT Red Dye (Lot# 257201; 16 Fl. Oz.)
Kingscote Chemicals
9676 N. Looney Road
Piqua, OH 45356
1-800-394-0678
Fax: 937-773-7994
2. Accurately transfer 5.0 mL of the Rhodamine WT solution into a 1000 mL volumetric flask. Fill the
flask to the volumetric mark with deionized or distilled water and mix well to produce a solution that is
approximately 100 mg/L of Rhodamine WT. Transfer this standard to a glass bottle and retain it for
future use.
3. Accurately transfer 5.0 mL of the solution prepared in the above step to a 1000 mL volumetric flask and
then fill the flask to the volumetric mark with deionized or distilled water. Mix well to obtain a solution,
which is 0.5 mg/L in water (a 200:1dilution of the concentrated solution).
4. Store the concentrated standard solution produced in (6) above in a glass bottle in a refrigerator to retard
decomposition. The dilute standard prepared in the previous step should be used within 24 hours of its
preparation.
When rhodamine standards are required in the future, perform another dilution of the concentrated rhodamine
solution after warming it to ambient temperature. Our experience has indicated that the concentrated solution
that has been kept at cold temperatures is much more stable than the dilute solution stored at room
temperature.
It is well known that the intensity of the fluorescence of many dyes shows an inverse relationship with
temperature. The effect must also be accounted for when “calibrating” the YSI chlorophyll sensor with
rhodamine WT. Enter the calibration value from the table below corresponding to the temperature of the
standard.
WARNING: The “Chl Tempco” factor in the Advanced|Sensor menu, MUST BE SET TO ZERO,
when calibrating with Rhodamine WT.
Table. Approximate algal chlorophyll equivalent of 0.5 mg/L Rhodamine WT as a function of temperature.
T, C
ug/L Chl to
Enter T, C Ug/L Chl to
Enter
30 100 18 122
28 103 16 126
26 106 14 131
24 110 12 136
22 113 10 140
20 118 8 144
YSI Incorporated Drinking Water Monitoring Systems Operation Manual 5-19