Latest Blog posts from Markes.com

In the news – Trichloroethylene linked to Parkinson's Disease

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Over the last day or so, the attention of the global media has been attracted by a study concluding that occupational exposure to a once-common chlorinated solvent substantially raises the chance of acquiring Parkinson’s Disease.

The study, published on 14 November in Annals of Neurology, found that long-term exposure to trichloroethylene (aka TCE or trichloroethene) was found to raise the risk of Parkinson’s Disease by more than a factor of 6. Two other ‘air toxics’, perchloroethylene (aka tetrachloroethene) and carbon tetrachloride, were also found to be risk factors.

Trichloroethylene of continued interest to analysts

Although the cohort of twins studied are likely to have been exposed to the solvents before modern working practices and exposure limits came into force, the study is nevertheless of interest to analysts. For example, trichloroethylene remains in use for industrial degreasing and is widespread in groundwater, although it has long been banned for use as a general anaesthetic, skin disinfectant, and coffee decaffeinating agent.

Advice on detecting chlorinated solvents

Chlorinated solvents such as those mentioned in this study are easily detected by thermal desorption–GC/MS, and Markes offers a range of solutions for detecting these chemicals. Examples can be found in the following documents:

Analysts interested in detecting components in workplace air may find the first in our series of Applications Guides a useful starting point: Thermal Desorption: A Practical Applications Guide. I. Environmental Monitoring & Exposure to Chemicals at Work (Contact Markes for your personal copy)

Application Note TDTS 86 describes the detection of ‘air toxic’ compounds in compliance with a standard method (US EPA Method TO-17)

Application Note TDTS 78 describes how headspace–thermal desorption can be used to detect volatile compounds in water

Application Note TDTS 13 describes how the Bio-VOC can be used to detect compounds in breath. The UK’s Health & Safety Laboratory also offers guidance on breath sampling

If you’d like any more information on detecting trichloroethylene or other volatile organic chemicals, please contact our specialists directly for impartial advice.

David Barden

The Peltier effect – a ‘cool technology’ for thermal desorption

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David Barden, Media Officer at Markes International, dusts off his physics books and gets to grips with Peltier cooling, one of the key technologies behind Markes’ thermal desorption instrumentation.

The Peltier effect, despite being first noticed by Jean Peltier in 1834, remained a backwater of physics for over a century. However, in the last few decades, the technology has experienced a revival, leading to its incorporation into a number of commercial systems, our thermal desorption instrumentation being one. To understand why we use it, let’s first take a look at what the effect is.

How Peltier cooling works

The Peltier effect is the heat exchange that results when electricity is passed across a junction of two conductors, and is a close relative of the Seebeck effect (effectively the same phenomenon in reverse, used in thermocouples used to measure temperature), and the Thomson effect (generation of electricity along a conductor with a temperature gradient). Sparing ourselves the maths, conduction electrons have different energies in different materials, and so when they are forced to move from one conductor to another, they either gain or lose energy. This difference is either released as heat, or absorbed from the surroundings.

Therefore, when two conductors are arranged in a circuit (see diagram), they form a heat pump, able to move heat from one junction to the other. Unfortunately, though, it’s not always this simple, as the Peltier effect is always up against the Joule effect – the ‘frictional’ heating that results from electrons bouncing off the atoms. In most systems, this swamps the Peltier effect, and means that all that you get is a bit more heating at one junction, and a bit less heating at the other.

Such problems hindered the development of practical Peltier coolers, and it took the development of suitable materials for the technology to really take off. In modern devices, semiconductors are normally used, with many ‘couples’ like those in the diagram being formed into an array. Linking them together is a thin metal film, while ceramics are used for the cold and hot ‘plates’.

Why use Peltier cooling in thermal desorption instrumentation?

The most obvious benefit is that Peltier coolers don’t use liquid cryogen. This is a big advantage for thermal desorption technology, sparing the analyst from the cost and trouble of keeping the instrument topped up with liquid cryogen, and making it much easier to run automated cycles.

In addition, Peltier units are small, and because they have no moving parts, they also have a long lifetime. In our UNITY thermal desorber, we use two Peltier units stacked on top of one another to get down to the low temperatures needed to quantitatively trap the most volatile analytes like acetylene.

So why aren’t they used more widely in consumer products? The main reason is their relative inefficiency – typically only 0.5 J of cooling is achieved for every 1 J of electricity used, making them roughly an eighth as efficient as a modern refrigerator. In the case of the UNITY thermal desorber, this doesn’t really matter because we’re only cooling a 6 cm length of a focusing trap. However, the energy consumption becomes significant when cooling larger objects, and that’s why Peltier cooling is not yet routinely used for refrigerators or freezers.

Looking to the future, improvements in the materials used to make Peltier coolers are starting to make the technology more appealing, and already they can be found incorporated into portable devices for cooling drinks and the like. It’s possible that with further advances, the efficiencies of Peltier coolers may start to approach that of modern refrigeration systems, and this intriguing aspect of physics may start to feature more in our everyday lives!

Material emissions legislation in the EU – is your company ready?

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Caroline Widdowson, Material Emissions Specialist at Markes International, examines what the upcoming EU Construction Products Regulation will mean for materials manufacturers, testing laboratories, and the GC(MS) industry.

Concerns about air quality used to be associated just with outdoor air, but as this has got cleaner, attention has shifted to the quality of indoor air. Clearly, the most troublesome VOCs from indoor materials are those that are both toxic and widespread, and manufacturers are already under pressure to reduce or eliminate such chemicals from their products.

In the EU, this pressure is about to increase substantially, due to the implementation of the Construction Product Regulation (CPR). The upshot of this is that, from 1st July 2013, manufacturers wishing to CE-mark their construction products for sale in the EU will need to have their products tested by accredited third-party test labs using the harmonised methods. Significantly, they’ll also need to carry out in-house checks and controls to demonstrate ongoing conformity of their products – something that may well come as a bit of a shock to the system!

The implications for manufacturers of construction products in the EU and elsewhere are clear – unless they adapt to the new regulations, they will not be able to obtain the necessary labels to sell their products. It would be wrong of manufacturers to view this in a negative light, however – on the contrary, it is an excellent opportunity for product improvement and innovation. Even now, some companies are making low chemical emissions a key selling point of their products, and this is something that we can expect to see a lot more of in the future.

So what does this mean for those involved in chemical emissions testing and supply of TD–GC(MS) equipment? The effects will be twofold – small producers will be looking to third-party laboratories to provide a quick, simple and affordable screening service to evaluate prototype products and raw materials, while larger manufacturers will be more likely to invest in test equipment for routine in-house checks. Clearly, then, those involved in all areas of TD–GC(MS) would be well-advised to consider how the requirement for increased testing will affect their business. The methodology and tools for meeting the requirements of the incoming regulations already exist – the challenge will be in making sure that they’re available to the people who need it.

Notes

This blog post is an abridged version of an article that appeared in Separation Science in August 2011. For the full version, which also includes a discussion of the latest developments in the US, please see http://www.sepscience.com/emails/SepSci0811EU.pdf#page=2

What’s in the air I breathe?

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Matt Bates, Thermal Desorption Product Manager at Markes International, gets a handle on the amounts of volatile organic compounds present in the air

Speaking as an analytical chemist, I quite happily use ‘parts per billion volume’ (ppbv) to describe concentrations of volatile organic compounds (VOCs) in the ambient atmosphere – but it’s easy to lose sight of what these values actually represent in real life.

The air we breathe is made up predominantly of permanent gases, along with a variable amount of water vapour. The VOCs too vary substantially from place to place, but the most concentrated is methane (1.8 ppmv), with all the other organic compounds being in the low ppbv range. To get an idea of just how little these amounts are, see the accompanying graphic.

Outdoor air is one thing, but indoor air is quite another. With emissions of VOCs from indoor furnishings an area of concern at the moment, it’s worth taking a closer look at these. A pretty well-known one is styrene (the monomer that goes to make polystyrene). Widely acknowledged to be a ubiquitous component of indoor air, it’s released from a variety of materials used in interior furnishings, and is the subject of lots of regulations due to its suspected health effects. But how much might you actually breathe in over the course of a day?

Let’s say you’re in a new office, and it’s a cold day, so the heating’s on and the windows are closed, with not much fresh air circulating. A browse around the Web suggests that the indoor styrene concentration might be 2 ppbv, so let’s start with that. Given that you breathe in 10 litres of air per minute when at rest, that’s 4200 litres in a 7-hour working day. Multiplying that by 2 × 10–9 gives 8.4 µL of pure styrene vapour every day, which is equivalent to 0.34 µmol, or 36 µg (using the the molar volume of an ideal gas of 24.4 L to get a rough idea). It’s not very much really – less than the weight of a grain of table salt – and certainly much less than you get in the lab if you open a solvent bottle outside the fumehood!

OK, so that was a relatively high-concentration component – what about something at the opposite end of the spectrum? CFC-113 (or Freon^® 113) first appeared in the atmosphere in 1961, and underwent a sharp rise in concentration following widespread use as a refrigerant and solvent. However, following the Montreal Protocol, its concentration levelled off in the late 1990s, at about 84 ppt. Because its principal decomposition route is by the action of light in the stratosphere, its concentration is falling at only 1 ppt a year. Incidentally, the worldwide concentration is pretty uniform too (now that production is essentially zero, it’s had time to ‘equilibrate’), making it a useful ‘internal standard’ for air measurements.

Working through the maths again, and using its current concentration of 74 ppt, we find that, at today’s concentrations, you would inhale just 23 mg of CFC-113 over the course of an 80-year lifetime – about the mass of a grain of rice. Using another analogy, 74 ppt equates to just 0.2 mL out of an Olympic-sized swimming pool (2.5 million litres). And yet modern thermal desorption technologies wouldn’t have much trouble in detecting such low levels. That’s pretty amazing really.

However, low as those levels are, Nature’s inevitably got one up on us – at least as far as 1-p-menth-1-ene-8-thiol is concerned. This C₁₀ compound (a monoterpene thiol) is responsible for the fresh juicy smell of grapefruit, and can be detected by humans at levels as low as 0.1 ppt. Now there’s a challenge for the gas chromatographer!

A blog about thermal desorption?

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David Barden, media officer at Markes International, introduces the Markes blog and explains why, if you’re interested in thermal desorption or the wider world of air analysis, you ought to take a look.

What did you think when you saw the ‘blog’ tab on our homepage? Curiosity? Surprise? Incredulity?

Whatever your thoughts, you might legitimately question whether there’s anything worth blogging about on the subject of thermal desorption equipment.

What we hope to prove by writing this blog is that there is – and we hope it makes interesting reading.

First off, why have a blog at all? Well, at Markes, we’ve always been interested in helping customers solve their problems. Not about simply producing equipment, but about understanding what our customers want, and developing solutions that help them. In times gone by, you did that at tradeshows, or by visting customers on-site. With the rise of new media, however, this has changed for many technology companies, and we believe that it shouldn’t be any different for manufacturers of thermal desorption equipment.

So the aim of this blog is to engage more directly with you, the scientist. Perhaps you’re a Markes customer, and want to keep up to date with what’s going on in the world of thermal desorption? Maybe you’re new to the technology, and want advice about making the most of it? Or perhaps you’re just interested in the world of air analysis? If so, then this is the place to come and hear some thoughts on the industry, and have your own say on them. We’ll welcome any comments, and will happily start a conversation with you.

So what can you expect from this blog? Primarily, insight from seasoned specialists at Markes about what’s happening in the world of thermal desorption and related technologies, along with the myriad of applications. We’ll also be examining some of the underlying science, and drawing together some of the latest news on regulations, with commentary on what this might mean for you.

One thing that we’re not going to be doing is giving you the hard-sell on our equipment, as you can read all about that on the other pages on our website. We hope, though, you’ll excuse us if we just mention our products occasionally!

So whatever your interest in thermal desorption or air analysis, visit us from time to time (or follow us on Twitter), and see what we’ve got to say... and let us know what you think.

Latest Blog posts from Markes.com

In the news – Trichloroethylene linked to Parkinson's Disease

Over the last day or so, the attention of the global media has been attracted by a study concluding that occupational exposure to a once-common chlorinated solvent substantially raises the chance of acquiring Parkinson’s Disease.

Trichloroethylene of continued interest to analysts

Advice on detecting chlorinated solvents

Further reading

The Peltier effect – a ‘cool technology’ for thermal desorption

David Barden, Media Officer at Markes International, dusts off his physics books and gets to grips with Peltier cooling, one of the key technologies behind Markes’ thermal desorption instrumentation.

How Peltier cooling works

Why use Peltier cooling in thermal desorption instrumentation?

Further reading

Material emissions legislation in the EU – is your company ready?

Caroline Widdowson, Material Emissions Specialist at Markes International, examines what the upcoming EU Construction Products Regulation will mean for materials manufacturers, testing laboratories, and the GC(MS) industry.

What’s in the air I breathe?

Matt Bates, Thermal Desorption Product Manager at Markes International, gets a handle on the amounts of volatile organic compounds present in the air

Further reading

A blog about thermal desorption?

David Barden, media officer at Markes International, introduces the Markes blog and explains why, if you’re interested in thermal desorption or the wider world of air analysis, you ought to take a look.