The C3 submersible fluorometer is used to study Chlorophyll a and CDOM in the lake. I want to calibrate the Chl. a sensor. At the same time, I want to establish the relationship between the known concentration and the secondary solid standard (SSS).

Following was the calibration steps (from the C3 manual):

First, I put the C3 into a solution with vivo chlorophyll. After the RFU signal was stable (the standard RFU), I reconded down the signal and performed chlorophyll a extraction to determine the Chl. a concentration of the solution, which was the standard concentration (15 ppm).

Then, I put the C3 into distillation-distillation H2O to set the RFU reading as blank. After that, I dried off the optical end of C3 and installed the SSS. I used a flathead screwdriver to unlock the locking nut by turning it counter clockwise as far as it can. Then, I inserted the green screw driver from Turner Desings to the hole inside the locking nut to adjust the signal of the SSS. When the RFU signal was close to the standard RFU, the standard concentration was set, given by the standard concentration determined previously. I locked the SSS by using the flathead screwdriver, turning it clockwise till it reached down.

Ideally, C3 should read the SSS as the standard concentration afterwards. However, the next day, the reading of SSS was 20 ppm higher than the standard concentration I set before.

Did I use the SSS incorrectly?

I apprecieate your reading and thank you for your respond in advance.

Tochia

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