I want to determine the nitrate in sediment and water column using Cd nitrate reduction method. I want to know what is the procedure to construct cadmium column.
This method pertains to nitrate analysis of water samples, sediment samples may require a different column preparation procedure.
First, set up the stage for your column construction with a stand, two beaker clamps, and a funnel with a disposable micropipette tip fixed to the neck of the funnel with tape.
Cut a ~6" section of 0.110" ID tygon tubing and fit one end to the pipette tip.
Soak a plastic nipple and some glass wool in your Ammonium Chloride reagent and insert into the tag end of the tygon tubing.
Attach a .050" ID tygon tube and hose clamp to the nipple on your column and fill the neck of the funnel with Ammonium chloride.
Detach the hose clamp and allow the entire column assembly to fill with reagent, tap/squeeze the nipple and wool to get all the air bubbles out of the column prior to assembling the column.
Re-attach the hose clamp to the smaller tygon hose.
Activating the cadmium.
In a 100ml beaker add about 50g of cadmium and 50ml of 6N HCl. Stir by hand for 1 min and rinse several times with DI
Repeat acid wash and DI rinse 2 twice.
Activate the column using 50ml of 20g/L copper sulfate solution. Stir until the reagent loses its blue color or copper particulates start to form.
Rinse with DI until cadmium is clean and repeat copper sulfate activation a second time and rinse with DI, may take up to a dozen rinses.
Once clean, cover cadmium with 50 ml of Ammonium chloride reagent
Prepping the column
Using a clean spatula slowly add cadmium to the funnel, being careful not to expose the cadmium to any air.
Tap and squeeze the cadmium in the column to make it as packed as possible
Leave about 5 cm of space at the top of your column to fit another piece of ammonium chloride soaked glass wool and nipple.
The messy part is removing the column from the funnel and allow the funnel to drain in a beaker. Quickly insert the wool and nipple and attach the tag end of the 0.05" ID tygon to the second nipple.
Holding the entire assembly from the hose clamp, with the nipples facing up, flick the wool and nipples to get all of the air that may be in the column into the smaller tygon with the hose clamp.
From my experience, once the cadmium is activated it is good for a days worth of analysis before it needs to be replaced with a fresh column. I have heard that you may be able to prepare a few columns and store the whole assembly in a beaker of ammonium chloride reagent but haven't experimented with that myself. Hope this helps!
Follow Wood et al. 1967, an article published in JMBA UK.
Determination of Nitrate in Sea Water by Cadmium-Copper Reduction to Nitrite.
Journal of the Marine Biological Association of the UK 47(01) · February 1967
DOI: 10.1017/S002531540003352X
Be extremely cautious (gloves etc.) when working with cadmium!!!
I have prepared few columns with my colleagues a few years ago and the columns still work well. If you work on samples with lots of suspended material, filter the samples and take care about protection of the columns' surface using ammonium chloride and activation (by KNO3) of the columns if you do not work some longer time. Good luck and do not be in a hurry when preparing cadmium-copper fillings for reduction of nitrate into nitrite. Test each column to get the proper factor and do that once in a while.
More to read: 10.1021/ac50062a039
Comment on the first answer: Good tutorial, but it should be stressed that the columns could be used for years once they are made properly, you need to keep them SOAKED all the time and not allow the air to dry them from above. That is why you should use some aluminum cap (loosen, not tight) above, and some strict cap (remove it from the medicine dropper and use it, very cheap and efficient) on the pipe end where the water drops will be captured by some glass tubes (I was collecting 30 mL of the sample, whilst the first 30 mL you should throw away since you use them to wash the system from the previous sample). Once a year do the testing of the column/s factor/s by calibration procedure.
Dear Sir
I think the links below will benefit you in your search
https://archive.epa.gov/water/archive/web/html/vms57.html
https://www.nodc.noaa.gov/archive/arc0001/9900162/2.2/data/0-data/jgofscd/Files/protocols/Chap8.htm
Article A Modified Procedure for the Determination of Nitrate in Sed...
Best Regards
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