EXO Standard Preparation - Rhodamine

EXO Standard Preparation - Rhodamine

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EXO Standard Preparation - Rhodamine

This video covers the preparation of standards for the calibration of the EXO Rhodamine sensor.

Timestamps of specific moments of the video

  • 0:00 – Overview and Required Equipment
  • 0:54 – Working Solution of Rhodamine Dye
  • 2:57 – Concentration 1
  • 4:57 – Concentration 2
  • 6:30 – Storage Instructions

Video Transcript

In this video, we will prepare the rhodamine dye standards used for the calibration of the EXO Rhodamine sensor.

While the dye is not toxic, it can stain easily. So it’s a good idea to wear safety glasses, gloves, and a lab coat. You will need three one-liter volumetric flasks, a high-accuracy pipetter that can measure five mL, a high-accuracy pipetter that can measure 200 µL, three labeled amber bottles for storage, deionized water, a transfer pipet, and rhodamine dye. Make sure you have purchased Rhodamine WT as a 2.5% solution. This is your stock rhodamine dye. You can purchase this from Kingscote Chemicals, which is referenced in the EXO manual.

First, prepare a working solution of the Rhodamine dye. This will be a 125 mg/L solution that you will use to prepare further dilutions. Make sure you use good lab techniques, especially when pipetting, to minimize errors in transferring liquids.

Using a one-liter volumetric flask, fill it to about 90% of the volumetric mark with deionized water. This does not have to be exact. Using a micropipette, or other high-accuracy pipette, transfer 5.00 mL of the 2.5% Rhodamine solution into the 1-L flask. Deposit the dye directly in the water and rinse the pipet tip to get all of the dye in the solution.

Now fill the flask up to the volumetric mark to make one liter of solution. Use a transfer pipet to get an accurate volume.  Cap the flask and invert three times to mix. This is now your working solution of 125 mg/L. Store this solution in an amber bottle in the refrigerator to minimize degradation. You can come back to this working solution to make your standard dilutions for up to two years.

Now, we will prepare two concentrations that we’ll use for the Rhodamine sensor calibration. One will be 25 µg/L, and the other must be somewhere between 125 µg/L and 1000 µg/L. Choose the concentration that works best for your site conditions and desired range. We will use 125 µg/L today. For our 25 µg/L solutions, first, we will take a clean one-liter volumetric flask and fill it to about 90% of the volumetric mark with DI water. Again, doesn’t have to be exact. Now, use a micropipette to transfer 200 µL of the working 125 mg/L solution to the flask. And rinse the pipette tip to make sure all of the dye transfers. Then, fill the flask up to the volumetric mark to make one liter of 25 µg/L solutions. And use a pipet or dropper to get an accurate volume. Cap the flask and invert three times to mix. Transfer this solution to a labeled bottle, and we have our first Rhodamine standard!

Now for the 125 µg/L standard. We will take a clean one-liter volumetric flask and fill it to about 90% of the volumetric mark with DI water. Then we use the micropipette to transfer 1.00 mL of our working 125 mg/L solution. And rinse the pipette tip in the solution. And finally, we fill the flask to the one-liter mark with DI water and use the transfer pipet to get right to the line. Cap the flask and invert three times to mix. I’ll transfer this to a labeled bottle. And we have our second Rhodamine standard, and we’re ready to do our Rhodamine sensor calibration! These two prepared standards can be stored in the refrigerator at 4 degrees Celsius and should be used within 30 days.

Please check out our other EXO University videos, and thank you for watching!

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