Why Choose Microwave Digestion Systems for Sample Preparation

Interview conducted by Mychealla RiceAug 21 2014

Microwave digestion is an established technique that has been used for many years. Recently laboratories are beginning to use microwave digestion for sample preparation.

In this interview, Bob Lockerman, Analytical Product Manager at CEM Corporation, speaks to AZoM.com about the company, their microwave systems and the future of the industry.

What has changed at CEM since we last spoke in 2014?

Things have changed a lot since we last spoke. CEM is still ran by its original founder, doctor Mike Collins who started the business in 1978, and still follows his original vision. The company has over 300 employees worldwide, with six global subsidiaries and headquarters in Matthews, North Carolina.

The company now consists of four divisions, which is one more than when we last spoke; with the new division focusing on analytical organic technology, which has just released a revolutionary new EDGE system that does solid liquid extraction in as little as five minutes. The more established divisions are our life science and bio-science division, which focuses on peptide and small molecule synthesis, our process control division, which focuses on food testing, and our analytical inorganics division.

The analytical inorganics division is our largest and is also where I work. Here, we focus on microwave digestion systems with trace metals analysis. Our primary markets include environmental, food and agricultural, pharmaceutical, along with chemicals and petrochemicals.

We’ve also recently updated our MARS 6 batch digestion system with technological and accessory updates, making it easier to use, more advanced, and more accurate.

Why do laboratories choose microwave digestion for sample preparation?

Microwave digestion is an established technique that has been used for the last 30 years. Despite this, many groups have only just begun using the technique, which means they are not aware of how the technique has developed.

Sample digestions are used to suspend samples in the liquid phase, as this facilitates trace metal analysis. Using a microwave digestion method provides two main benefits.

Firstly, using microwave energy in a sealed vessel significantly increases the boiling point of an acid. For example, nitric acid boils at about 120 °C at atmospheric pressure, whereas in a sealed vessel nitric acid can be heated up to 250 °C. This extra temperature means samples can be digested faster and more effectively. An example would be that a US EPA soil digestion can be performed in ten minutes using a microwave digestion system versus four hours by traditional methods.

The other advantage is that it is impossible to completely digest some types of materials using just acids at atmospheric boiling points. In order to digest these types of materials a higher temperature is necessary. Using the sealed container, as in microwave digestions, this is possible.

Have there been any developments on the Discover SP-D?

We have found another application for our SP-D technology. We have found that many of our SP-D customers or prospects wanted to run very small samples such as clinical laboratories. These acid samples can be as small as 0.5 mL or less, which are very hard to process with standard microwave systems, as microwaves work best with larger volumes.

To address this problem we recently introduced our new Discover SP-D Clinical system, which is designed to run a 4 mL or a 10 mL sample vial in glass or quartz. If our users have the 4 mL option they will be able to run digestions with a 0.5 mL acid volume, allowing clinical labs to still have access to the technology.

The design of the system was instinctive, and we were interested to take on this challenge. Most of our customers want to go the other way and digest increasingly large samples, whereas these customers wanted us to go smaller!

What sets CEM’s products apart from your competitors?

CEM developed and introduced the very first microwave digestion system back in 1986. At that time the only parameters you could control were power and time. This made it very difficult to take a method from one laboratory and transfer it to another lab if the lab had different line voltage or a more powerful magnetron. It was almost almost impossible to transfer methods.

Once CEM introduced temperature control in the early 1990s it became easier to exchange methods across the globe and from lab to lab. That was when microwave digestion started to gain worldwide acceptance.

Since then many more innovations have taken place. I think that's what sets CEM apart; we're the innovators, we are the ones that make the scientific advancements.

In the early 2000’s we introduced the ability to run up to 40 samples. Prior to this it was only possible to run 12 samples at once – so the jump to 40 was a three-fold increase in lab capacity. It also meant that microwave digestion systems could compete with Hot Blocks. It was at this point that commercial labs began to show interest in our systems for their EPA samples.

More recent advancements have centered on the ability to operate our systems remotely. This allows researchers to run the system from their desk, allowing them to be more productive whilst the system runs in the lab.

A new temperature measurement system, iWave, has also been developed. iWave is a floor-mounted temperature sensor which uses light emitting technology to see right through the vessel material and into the liquid. In the past a single reference control vessel was used to control the batch, whereas now every single sample is under full control because you can measure the exact temperature of every vessel. This temperature can also be recorded and reported.

We have also developed a new high-performance vessel called iPrep. iPrep has a patented dual seal design that allows us to reach much higher temperatures and pressures than previous models and digest more difficult materials with ease.

These materials include Kevlar, which is used to make bulletproof vests, bunker oil, the thickest type of crude oil, and even PET plastics, which are very difficult to digest. Microwave digestion using the iPrep vessel allows these materials to be digested. These advancements have made the system much more versatile, more adaptable to different applications, and made the system easier to use.

Are there different vessels for different applications?

Yes, we do provide different vessels for different applications. The decision on which vessel to use really comes down to what temperatures you need to work with to get a complete digestion, and also how much sample do you need to work with in order to achieve your detection limits.

Most samples requiring moderate digestion conditions, which we consider to be up to 210 °C, can be run using our CEM MARSXpress vessel technology. This is the vessel technology that can run up to 40 samples at a time, providing a great tool for high throughput laboratories such as those running US EPA methods, food samples, tissue, feeds and fertilizers, and nutraceuticals, among others.

For samples that require higher temperatures, we offer a high-performance vessel called the iPrep, which I mentioned earlier. The iPrep uses patented dual seal technology that can hold extremely high pressures, allowing for the digestion of materials such as Kevlar, Bunker oil, PET, and many other difficult organics. The iPrep can run 16 vessels in a carousel, which is good throughput, but nothing like the MARSXpress. Vessels like these are more expensive than MARSXpress vessels, because of the material construction.

When working with customers, we try to pick and choose the vessel that best meets the needs of that particular laboratory.

Do CEM provide application support?

We have a full application support team at our headquarters, with both ICP-OES and ICP-MS capabilities. This means we support the digestion side and we can also assist on the analysis – this is something that none of our competitors offer.

In addition, we also offer two-day training classes at our facility several times per year, and we can provide on-site training as well.

Of course, we are always available with toll-free support over the phone or via email. There are many options for support because it is very important to us, to ensure that our customers are successful when using their new equipment.

What’s in store for the future of CEM?

Sample prep is always going to be part of the trace metals analysis equation because you have to get the sample into an aqueous solution prior to analysis. Over the years there have been many tremendous changes, which have made the systems more productive, easier to use, and safer. I think most of the innovations moving forward will make the user interface easier to use or make the system smarter.

In terms of the interface, I would like future systems to recognize users via fingerprint or face recognition, much like the features on our own smartphones. Following facial ID they would then be identified and automatically logged in to the system via the activity log. This in turn would give them the permissions that they have been assigned by the administrator. This could be very helpful for CFR considerations.

I also think the systems will be able to better monitor how the digestion process is progressing, even to the point of knowing when the sample digestion is completed. For example, at the end point the system could shut down and alert the user. We normally overcook the samples, so to speak, in order to make sure we get a complete digestion, so this could significantly save time. CEM's been providing innovations for solutions for over 40 years now. I am excited to see how we can continue to push the technology forward into the future.

About Bob Lockerman

A 1984 graduate of the University of New Hampshire (B.S., Analytical Chemistry), Bob Lockerman has worked in the scientific industry for thirty years. Most of that time has been spent at CEM Corporation in multiple roles including applications, sales and product management.

He has co-authored several papers on microwave chemistry and makes presentations on the topic worldwide. He has served on several AOAC committees, as well. He is currently the Analytical Product Manager for CEM Corporation.