In this context, “complex” is a polite way of describing samples that are utterly filthy, full of high boiling, involatile material and liable to contaminate your inlet and column pretty quickly.

Extensive clean-up can be used, but this is expensive, extremely time-consuming and usually results in very low analye recoveries, so an increasing number of analysts use simplified sample preparation methods and choose to live with the instrument down-time that results from a build-up of dirt within the system.

GC-MS suppliers recognize this reality and it is common to fit a back-flush capability to the system, so that the high boiling gunk can be back-flushed into the hot injector, preserving the integrity of the main analytical column.

In our experience, the approach offers only a partial solution:

• Samples often contain involatile material that remains in the injector, and injector contamination will build up rapidly to a point where it becomes problem. Back-flushing is no help in solving this problem.
• Material that is back-flushed into the injector will accumulate somewhere in the injector or its associated pneumatics and will often give rise to carry-over and eventualy, blockages. Cleaning-out the injection system at this point is a big job.

There is another way of approaching the problem.

The GERSTEL  ALEX provides a way of using the GERSTEL MultiPurpose Sampler to automate the exchange of injection port liners installed within the CIS 4 PTV injector.

ALEX works like this:

1. Use the lowest injector temperature that will transfer enable your least volatile target analyte to the column completely (easy to find with a few scouting runs using your standard mix).
2. This temperature will ensure that all of the involatile material stays within the injector and that the only material to enter the column and detector is certain to come out at the other end.
3. As you run successive samples, you will begin to accumulate muck within the injector and experience will soon tell you how frequently you need the system to swap out the liner automatically.
4. Once you have this sorted out, you should then be able to maintain you data quality while running for extended periods.

More up time, means that you can run more samples with less hassle.

It is pretty easy to clean-up and deactivate the used liners, and I know of analysts that recycle their ALEX liners continuously.

If you wanted a real belt-and-braces approach, you could combine ALEX with a column back-flush.

With ALEX, you are restricted the normal injection volumes (1-2 microlitres), however, there is a variation on this concept that enables you to work with much bigger samples (GERSTEL ATEX).

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Last week, the Association of Clinical Biochemists (ACB) held an event in Liverpool called FOCUS, which is their annual conference and exhibition.

Anatune attended the meeting and displayed the Clinical Workstation that has been developed to automate sample preparation for the analysis of clinical samples by LC-MS.

LC-MS has a huge amount to offer to people working in this field, but the labour intensive nature of the sample preparation needed, is a serious drag on the use of this powerful technique. Clinical labs are busy places and it is always hard to find spare pairs of hands.

Clinical labs are staffed with highly qualified people and it is an utter waste of talent, to have to assign PhD Biochemists to perform repetitive sample preparation on a routine basis.  As you can imagine,  Anatune’s  stand was one of the busiest and despite the fact that the number of delegates was smaller than last year, we demonstrated our system to almost 140 people over the three days and we received a large number of serious enquiries.

Workshop –Automated Sample Preparation of Clinical Samples

For those that want to learn more, we are organizing a one-day workshop at out laboratory in Cambridge on Thursday 21st June 2012, where attendees will be able to get hands-on with the workstation and see it running on our LC-triple Quad. Our aim, by the end of the day, is to ensure that attendees will have a very good understanding of how this technology might work in their own labs.

This is a one-day event and we only have a few places left, so if you are interested in attending, please contact us now on 01223 279210 or email enquiries@anatune.co.uk

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Agilent GC-MSD configured for DHS (FET)

Over the last few months, Fully Evaporative Dynamic Headspace Sampling (DHS (FET)) has been gaining the attention of many people.

DHS (FET) is developing a bit of a buzz about it.

Compared to conventional static headspace, DHS (FET) offers:

• Significantly lower detection
  limits.
• To a large degree, the elimination of effects due to matrix variability.
• Uniform high recoveries for analytes of different polarities, without the need to modify the matrix.
• Good recoveries for analytes of a much wider volatility range.

If you have experience of using static headspace, then you will understand that
these four items represent fixes for four of the most significant limitations
that users of headspace sampling encounter. As a consequence DHS (FET) greatly extends the number of tasks that headspace sampling can perform. This is big news for some.

What can it be used for?

Important potential applications for the technique include:

• Trace impurities in pharmaceutical products (GTIs and PGTIs).
• Residual fragrances in consumer products.
• Profiling of low level flavour compounds in foods and beverages.

For certain, there will be others.

Like static headspace, you only transfer gas phase analytes from the sample to
the GC-MS, so you keep the inlet, column and source squeaky clean – however
grim the sample may be.

How does it work?

DHS (FET) can be performed using the GERSTEL Multi-Purpose Sampler. FET stands for: “Full Evaporation Technique”, a concept, was originally devised by
Michael Markelov and co-workers⁽¹⁾ in the 1990′s as a way of performing matrix
independent headspace sampling. DHS stands for Dynamic Headspace Sampling, which is also an established sampling technique, that gives better detection limits than static headspace. What is new, is this combination of the two techniques, that ends-up delivering the best attributes of DHS and FET techniques.

This is the sequence of events:

1. Around 100 microlitres of liquid phase sample (this can be aqueous) is placed into a 10ml headspace vial.
2. The vial containing the sample is moved to a sampling station where it can be shaken, and if appropriate, warmed.
3. The whole liquid portion of the sample is allowed to evaporate in the vial, moving all of the volatile components in the vapour phase and leaving any solids in the bottom of the vial.
4. The whole of the vapour phase contained in the vial is swept out and onto an
   adsorbent packed trap that is closely coupled to the vial.
5. The trap is then moved to a thermal desorber mounted on top of a cooled, PTV injector.
6. The trap is heated and thermally desorbed into the cold injector, where the
   analytes are focused into a tight band and then injected, splitless, onto the
   column.

You can see the effect by comparing the two chromatograms (below), a greater than 100 fold increase in sensitivity can be observed by switching from Static Headspace to DHS (FET) for this sample of a herbal based liquor.

Comparing Sensitivity of DHS (FET) with Static Headspace Sampling

For more details follow this link to download a PDF copy of the application note.

We are thinking of organising a training day on DHS (FET) in our Cambridge
laboratory. Are you are interested in the idea? Perhaps you can let me know.

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Down Hall Country House Hotel

1. Meet to exchange experience and ideas with analytical scientists who are making automated sample preparation work for them.
2. Find out why Unilever Research believe that an instrument that combines large volume headspace and cryo-trapping is so important to them.
3. Learn about the UK Health and Safety Laboratories take on the future of chromatographic analysis in work-place measurements.
4. If you need to get more sensitivity from headspace analysis, find out just how broad your range of options are and how they compare.
5. Learn how automated solvent evaporation can be combined with other automated techniques – such as SPE and Liquid-Liquid extraction, to automate common, manual, sample preparation procedures.
6. SPME is an established and popular sampling technique. Sigma-Aldrich have developed new ways of taking samples with SPME fibres.
7. Purge and Trap sampling is popular as a way of getting the extra sensitivity needed to run in scan rather than SIM. See what World leader in P&T –  Teledyne Tekmar have been up to.
8. Applying miniaturized solvent extraction together with large volume injection is now a practical possibility for the automation of cumbersome liquid-liquid extraction procedures. See how this could work for you.
9. Learn about the newest instrumentation and automation tools from GERSTEL and Anatune.

Our conference is called: Automation in the Chromatography Laboratory and is held at the beautiful Down Hall Country House Hotel on Tuesday 12th & Wednesday 13th June, 2012.

You can register on-line here, or by telephoning Sue Roach on 01223 279210

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Butter flavourings are popular with consumers of popcorn

Last week, we organised a couple of “Technology Days” so that we could show customers some of our newest offerings and a few things that we have coming-up in the near future.

Craig Duckham was one of the attendees. Craig is an old friend of Anatune, a highly skilled analyst, now working as an independent analytical consultant to the food and beverage industry.

One of the things that we showed on the day was our new automated system for the analysis of formaldehyde and other carbonyl compounds in air. Craig drew our attention to the possibility of using the system for the determination of diacetyl in air.

Diacetyl (2,3-butanedione) is a naturally occurring flavour compound and one of the chemicals responsible for giving a “buttery” flavour to foods. It has been used for many years as a flavouring agent by the food ingredients industry. However, excessive exposure airborne diacetyl is now known to contribute to a serious respiratory condition, known as “popcorn workers lung”, that can afflict some workers in the food processing industry.

If there is a need for an automated solution for this analysis, then there is a reasonable chance that our automated formaldehyde system could be set-up to do it.

So, my questions are:

1. Who needs to analyse diacetyl in air?
2. Who runs enough samples to make it worthwhile developing an automated solution for this analysis?
3. Would anyone be interested in discussing this application with Craig and I?

If so please drop me an email via: enquiries@anatune.co.uk, or phone me on +44( 0)1223 279210.

Craig can be contacted via email on: craig.duckham@CDRnD.co.uk or by phone on +44
(0)7530 859977.

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