I worked in a QC laboratory for few years and I see how much stuff is wasted and thrown away every single day.
Printing paper and paper towels for start, but tons of (usefull ?) equipment is just discarded. In my series of instructables I will try to to show how one can minimize the waste and / or save some money.
On the plus side I am proud of those little improvements.
For the first improvement I will show you how to reuse defective HPLC columns (which should be the first step in recycle cycle not scraping).
If your peaks are getting wider and wider or begin to divide you can try flushing the column or use a cleaning procedure. Frankly in my 10+ years in the lab I saw maybe 30 positive effects of cleaning a column. It usually lasted for a short amount of time and it was never a remarkable improvement. Still, this should be the first step before you use my procedure. In some cases (specially with just the resolution loss or non soluble particles in the frits) one can return to a normal state column just by washing it or back flushing. Just try to think about what could block or stick to the stationary phase and use proper measures for reversing the bond.
If all procedures fail (and in QC lab you often have many examples of the same errors and changes) you can try to turn one old column into a source of stationary phase for other.
The peak division often means that the front (head) of a column is clogged or really dirty. The physical blockadge can be also visible on the frits inside. So go to the next step if you are interested in the procedure.
Step 1: Step 1: Preparing the Columns
First you should find the last chromatograms which were done on these particular column. You need at least 2 of them. Print or save them and clearly mark the corresponding data in order to be 100% positive which column should be repaired and which scrapped. I often repair the last one that lost some performance and the oldest one is going to be the donor.
Step 2: Step 2: Opening the Columns
This one is a bit tricky. Look closely at your equipment and find out what type of tools is needed. Then gently but gradually apply force to unscrew the top of the donor.
Once open take out the front frit (wash it in 50% MeOH/H2O) and pack it in a zip bag. Label it properly.
If the phase was clogged you can often see the change of the color, most of the popular fillings are pure white powder or paste (if not dry).
Take your thin spatula and take out first few mm of the phase, under it you can see the change of colors. Many times the sides of the first 1cm are really dirty. I take out all different color silica from the column. Discard it, your goal is under it. Now take out some or all the phase and store it in a small labeled container, like HPLC vial.
It is important to know exacly which phase you have and use it in the same type of healed column.
Step 3: Step 3: Prepare the Patient
Now open the second column. Remember that this one will be used again so be extra carefull !
Clean the frit, scrub out the dirty phase and get ready for refill.
Rinse the pure white donor powder in some mixture of MeOH and water (small amount, like 1-2 drops) it should be sticky and pasty. Now carefully pack as much of it into the previously created cavity. Scrape to flat and then add a little more. If you took out much of the stationary phase you should probably push it in with a glass rod the diameter of the column inside.
Clean the sides of the thread and reassemble the column. You will probably need to thighten it more then it was before. Done. 100% succes. Now let's see if the patient dies.
Take your repaired column and reproduce the same analysis on your HPLC. Try to replicate as much of the test as on the saved chromatograms to have definite knowledge that there was no equipment change.
If the procedure failed you will quickly see it on the charts.
Start with a mixture of non aggresive phase or pure methanol and increase the flow to a maximum allowed pressure, in this way you can repack some small voids created by your operation.
If you want to be precice use a proper, tested method, inject 5-10 times your mixed stantards and compare the results.
In my tests I saw a major improvement in peak shape. Sometimes a little loss on the resolution.
You can expect to have weird distorions in few of the first injections, this is normal. Once the pressure is stable test your (new) column.
In this way one can repair old columns several times. It is not magic and some repairs will fail. Many columns are pressure packed and returning to the same state is hard. So be prepaired for failure. The plus is that you combine 2 old columns into one usable so in worst case you just throw them away.
Have fun !!!