Wavelength Tech Forum: ICP/ICP-MS

One of the most powerful and sensitive testing techniques, ICP/ICP-MS has found application in fields as varied as water testing, food safety, and petroleum analysis. Here, our panel of industry experts talk about all that is happening in this high-growth area.

Joining us for this discussion are Shona McSheehy, Thermo Fisher Scientific; Martin Nash, Thermo Fisher Scientific; and Steven Wilbur, Agilent Technologies, Inc.

What do you think is the most critical area of ICP and ICP-MS research right now? Why?

McSheehy: Research into the fundamentals and plasma-related technology that will theoretically significantly impact the next generations of ICP and MS instrumentation.

Technological progress coupled with advancements in sample introduction systems is generating more sensitive, more robust, and faster analyses for a whole range of scientific markets. Increased legislation is putting higher demand on analytical bodies, both in terms of sample throughput and in terms of analytical performance. Implemented legislation requires conformation to limits for a wider range of samples, a wider range of metals, and often at lower concentration than previous levels. Improvements in instrumentation and analytical solutions to accurately serve an increasingly diverse market are therefore an essential part of research for the analytical community.

Another research area which is anticipated to have a big impact on how we are currently performing analyses is speciation and nanotechnology. A trend of stricter legislation has been coupled with the introduction of more speciation-related directives. Manufacturers have launched a number of tailored speciation systems to ease the transition of speciation analyses from the research area to routine analyses. With the increased use of nanoparticles in food, industry, and the associated risk of their use not fully assessed, the trend for speciation analyses over the past 20 years is now likely to be replicated for nanoparticle analysis in the coming decade. Nanoparticle separation using chromatography, field flow fractionation, or fluid dynamic principles all require transient signal processing with extremely fast scanning, a demand for the latter.

Nash: ICP technology is being increasingly utilized for food safety applications in both the research and routine analytical laboratory environment. The increased demand for usage of this technique is driven through changes in the global food safety legislation and the requirement for monitoring both toxic and essential nutrient element constituents. Recent technology enhancements with ICP instrumentation have led to improved analyte detection capability, ease-of-use, and productivity to enable the most powerful and cost-efficient sample analysis regimes.

Wilbur: There are two areas of research using ICP-MS that are getting a lot of attention right now. They are 1) understanding the environmental fate and toxicity of engineered nanoparticles. This is an interesting and difficult problem because the toxicity of these particles is related much more to their small size (10-100 nm diameter) than to their elemental composition. While we can easily detect and quantify the elemental components, it is much more difficult to be sure that we are measuring the particles in their “native” state. 2) The determination of toxic metals in foods, pharmaceuticals, and nutritional supplements is becoming critical as more and more cases of tainted products are discovered. Many of these products are poorly regulated and the methods commonly specify older, less sensitive, less accurate analytical techniques. Elemental speciation is particularly important in these products because in many cases (chromium is a good example) one form is beneficial (Cr-III) and another highly toxic (Cr-VI).

It has been suggested that ICP-MS is a “universal detection method.” How close is this to being true? Or how far from being true?

McSheehy: Advances in ICP-MS and sample handling have definitely extended the range of sample matrices that ICP-MS can handle and therefore the spread of ICP-MS into different markets and research areas over the last years is comprehensive. ICP-MS use is being adopted into many new SOPs including European norms for foods and upcoming US pharmacopeia methods. ICP-MS is also branching further within the petrochemical industry, in particular for catalyst-destructive elements such as Si and Hg. Isotopic analysis with ICP-MS for the nuclear and geochemical industries, as well as geochronological dating and origin placement studies, is an exciting approach that lets us look into the past and define environmental and food quality for now and in the future. Commercially available packages for coupling liquid and gas chromatography to ICP-MS have also opened the analytical door to elemental species and laser ablation with ICP-MS, making spatial resolution and depth profiling for many materials a possibility. The fact that ICP-MS is able to handle so many different types of sample and to access so many different levels of information makes the technique global, but with demands continually changing and new areas of research emerging, ICP-MS developments are still required to make the technique truly universal.

Wilbur: From an elemental standpoint, ICP-MS is nearly universal, meaning that there are only a small handful of elements which cannot be measured with high sensitivity and specificity directly by ICP-MS. They are H, He, Ne, Ar, and F. So from that respect it is nearly universal. On the other hand, ICP-MS by itself provides no molecular information, so while it can provide the elemental composition of any sample (after appropriate sample preparation), it cannot provide information about how those elements are combined in the sample. Hyphenation to chromatographic or electrophoretic techniques and parallel analysis with molecular mass spectrometers is still required to make the technique truly universal.

The trend in U.S. and worldwide governmental agencies with regard to water, lead, etc., is toward stricter regulations. How will this impact ICP and ICP-MS research?

McSheehy: With a drive to lower levels and stricter regulations, it is likely that there will be a parallel drive that sees ICP-OES users turn to ICP-MS. The benefit of ICP-MS compared with ICP-OES is the ability of the technique to allow confident determination of ultratrace elements at the part-per-trillion level and below. There remains a perception that ICP-MS instruments are more challenging to use than ICP-OES instruments. However, with improvements in software and application-specific methods for ICP-MS, the transfer from ICP-OES to ICP-MS should be smoother for many routine laboratories. Speciation, too, requires the sensitivity of ICP-MS. EU Water regulations will specify annual average concentrations of 0.2 ppt tributyl tin and 0.5 ppt of pentobromodiphenyl ether, limits that are currently realistic only with GC-ICP-MS without excessive preconcentration.

Nash: With continual evolution and refinement of U.S. and worldwide government agency-driven regulations, there will be a continued emphasis on detection limit capabilities and instrument technologies to enable the most productive and cost efficient sample analysis regimes.

Wilbur: The trends are toward lower regulatory limits and toward elemental speciation, meaning that in many cases, it isn’t good enough to know how much toxic metal is present (even at really low levels), we must now know the form the metal is in. The lower required detection limits are already moving many analyses from ICP-OES to ICP-MS (arsenic in drinking water is a good recent example). Additionally, hyphenated techniques such as GC-ICP-MS and LC-ICP-MS will be required to meet the increasing requirements for elemental speciation analysis.

How important is cleaning and maintenance to the various forms of ICP research?

McSheehy:Appropriate maintenance of any instrumentation is closely related to the amount of time the instrument performs without a service related intervention. Daily procedures such as checking or replacing pump tubing, regular cleaning of the sample introduction components, and biannual replacement of forward pump oil is all instrumental in maintaining a well performing instrument.

Nash:The design concepts employed by modern day ICP instrumentation, for example within liquid the sample introduction system components, have greatly simplified and reduced the requirement for cleaning and maintenance operations within the research laboratory environment.

Wilbur:Maintaining the instrument (ICP-OES or ICP-MS) in optimum condition is obviously important. While the two techniques have a lot in common, the maintenance requirements are different in several important areas. ICP-MS instruments differ from ICP-OES instruments in that they must actually extract ions from the hot plasma into the high vacuum region, as opposed to merely “watching” the plasma. This requires a system of interface cones and ion focusing lenses (collectively called the interface) that must be kept clean for best performance. Recent advances in interface design and improvements in sensitivity have permitted newer instruments to measure much smaller sample volumes and lower flows, which significantly reduces the need for frequent interface maintenance.

What developments or trends do you see emerging in this field in 2010?

McSheehy:There is likely to be a continuing trend of ICP-MS as a tool in the field of metallomics and the application of ICP-MS technology to immunoassay. The study of naturally occurring biometal species and the role they play in cellular biology and the artificially generated metal-protein species for absolute protein quantification enjoy the explicit advantage of ICP-MS sensitivity. This means analysts are able to characterize and quantify species and proteins at concentrations lower than ever before, levels which are actually representative of real samples.

Another trend in the biometal field is bio-imaging of metals. The role of metals in causing or alleviating disease can be assessed by analysis of affected tissues using laser ablation ICP-MS. This technique allows for spatial resolution, critical for characterizing metal pools associated with tissue or organs and advanced software permits concentration maps of metals throughout tissue slices.

Nash:New developments with ICP torch design and the use of new sample introductions accessories, which greatly reduce the sample volumes encountered by the liquids sample introduction system.

Wilbur:There is a lot of interest and funding available currently for nanoparticle research. This will continue through the year. As far as research into the actual technique of ICP-MS, continued improvements in interference removal and improved sample throughput are important ongoing trends. Additionally, improving the measurement of biologically important nonmetals, particularly sulfur and phosphorus in biological samples will continue to drive ICP-MS R&D.

What do you think?

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