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Adding More Capability to Dilute and Shoot

Kathy Ridgway

31st March 2014


As Andy Golby discussed in his recent post, for anyone involved in LC-MS or GC-MS the “Dilute and Shoot” approach to sample preparation and introduction has real attractions. You just dilute the sample with an appropriate solvent so that the concentration of any problem matrix compounds are reduced and inject the same volume as before. A modern mass-spec with its greater sensitivity compensates for this dilution of your analytes. You can see why this would be worth considering.

Unfortunately this approach just doesn’t cut the mustard for some analytes or sample types.

  • What if dilution removes the problem of matrix but reduces the concentration of some of your analytes to where the sensitivity of your mass-spec can’t detect them?
  • What if the matrix still causes an issue even after being diluted?
  • What if your samples contain particulate materials?

In these cases, it may be that you still need to do some sample pre-concentration or clean-up of the sample, before introducing it into the mass-spec. This means that your sample-prep process ends up being ‘clean-up and dilute and shoot’ which of course involves more time and effort to get right.

If you’re processing a large amount of samples, errors are bound to creep in.

SPE has long been a useful, but labour intensive, approach to sample prep. Filtration can also be time consuming – especially if you have to extract the filtrate.

In the real World, simple dilute and shoot is useful, but it won’t be the answer every time.

The GERSTEL MultiPurpose Sampler (MPS) can help you with the practicalities of dilute and shoot in two ways:

  • Firstly, it can automate sample dilution and the addition of standards.
  • Secondly, when you need to do some sample clean-up the MPS can automate both sample filtration and solid phase clean-up for you.

This is where Instrument Top Sample Prep (ITSPTM) comes in. This is a low-cost accessory for the GERSTEL MPS that takes the manual labour out of both sample filtration and solid-phase clean-up.

Think of ITSPTM as both a micro-scale filter and SPE device. Each ITSP cartridge can either contain a membrane for sample filtration or a sorbent that is appropriate to your sample chemistry. The MPS syringe needle looks after the liquid handling tasks needed to either filter, concentrate or clean-up your sample.

The GERSTEL MPS can add internal standards, surrogates, reagents and also prepare calibration curves for you. In fact, your whole sample preparation process can be automated in many cases.

One final twist is that if you are preparing samples by hand, you really have no choice but to work with your samples batch-wise. This means that no two samples are ever treated exactly the same. On the other hand, the MPS deals with samples one at a time – so that to first approximation, every sample is dealt with in the same way.

If you would like to see how the GERSTEL MultiPurpose Sampler can help improve the way you work, please call us on +44 (0)1223 279210 or email: enquiries@anatune.co.uk.