{"id":2479,"date":"2021-06-23T15:28:50","date_gmt":"2021-06-23T22:28:50","guid":{"rendered":"https:\/\/depts.washington.edu\/chemwp\/chemwpnmr\/?p=2479"},"modified":"2021-06-23T15:28:50","modified_gmt":"2021-06-23T22:28:50","slug":"tips-getting-the-most-out-of-your-shims-av500-as-an-example","status":"publish","type":"post","link":"https:\/\/depts.washington.edu\/chemwp\/chemwpnmr\/2021\/06\/tips-getting-the-most-out-of-your-shims-av500-as-an-example\/","title":{"rendered":"TIPS – GETTING THE MOST OUT OF YOUR SHIMS – AV500 AS AN EXAMPLE"},"content":{"rendered":"

The majority of lock solvents used in our facility are fully deuterated i.e. 99.0% or more 2H enriched.\u00a0 This means that the Topshim system performs what is called ‘1D gradient shimming’\u00a0 or ‘Z-axis only’ shimming.\u00a0 This leaves the job half-done when it comes to shim optimization.\u00a0 The XY-plane or ‘transverse plane’ shims also need adjusting, albeit for a very small subset of shim gradients :\u00a0 [X, Y ] as an absolute minimum <\/strong>and ideally [X, XZ, Y, YZ] as an optimum choice. <\/strong><\/p>\n

I will show below the remarkable difference in the resolution that is made by merely touching up the [X, Y] shims <\/strong>after I complete the Topshim 1D along the Z-axis (i.e. the magnet’s axis) from the model compound Strychnine in CDCl3.<\/p>\n

In the following comparative spectrum :<\/p>\n

GREEN : <\/strong>corresponds to the spectrum recorded after completion of Topshim 1D only.<\/p>\n

RED :\u00a0<\/strong> When we spin the sample we see the dramatic improvement in resolution clearly bringing out the fine structure of the peaks.\u00a0 Spinning effectively <\/em>removes the magnetic field inhomegeneity in the XY plane.<\/p>\n

BLUE : <\/strong>This is a spectrum that is recorded without spinning. <\/strong> But I have merely adjusted the X <\/strong>and Y shims<\/strong> alone after Topshim 1D.\u00a0\u00a0 The resolution we get now is pretty close to what we achive by spinning the sample.<\/p>\n

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Green spectrum is after only Z axis shimming. For a nominal X and Y shim optimization, the resolution is dramatically improved (blue), as good as what one gets with sample spinning (red).<\/p><\/div>\n

You might wonder, why not simply spin the sample to obtain optimum resolution every time. Indeed, sample spinning is recommended<\/strong> to get the best overall resolution from the spectrometer. But there are caveats to keep in mind :<\/p>\n