Technology Forum: ICP and ICP-MS

From meeting demanding EPA standards for toxin levels to providing trace elemental profiles of bird feathers, ICP and ICP-MS have emerged as highly valuable techniques that are finding application in a wide range of new and interesting areas. And with new applications and stricter regulations on the horizon, these techniques will have an even greater role to play in the future of analytical chemistry.

Joining us for a discussion of these techniques and the issues and trends surrounding them are Steve Wilbur, Agilent Technologies; Jerry Dulude, Glass Expansion, Inc.; Ken Neubauer, PerkinElmer Life and Analytical Sciences; and Bill Spence, Thermo Fisher Scientific.

What is the current state of the ICP and ICP-MS marketplace? What trends do you see emerging?

Wilbur: ICP-OES continues to be the workhorse instrument for rapid multi-element analysis in high matrix applications where ultimate sensitivity is not required. These applications include many in the mining, manufacturing, and hydrocarbon processing industries. However, superior sensitivity and fewer, simpler interferences have led to the dominance of ICP-MS in the environmental monitoring industry where ICP-OES was once the major player.

Emerging trends include continued increasing acceptance of the use of collision reaction cell technology with ICP-MS for most common applications where high sensitivity and reduced interferences are critical. Additionally, recent improvements in ICP-MS sample introduction and interface systems have resulted in significantly improved sample throughput and matrix tolerance. These improvements will likely continue resulting in additional penetration of the OES market by ICP-MS.

Finally, the use of ICP-MS as a highly selective, sensitive element-specific detector for chromatography and electrophoresis applications will continue to increase.

Dulude: Up until now the ICP market seems to have been quite stable showing 5 to 10% annual growth over the past 10 years. As expected the relatively newer ICP-MS technique has shown slightly higher growth than the more established ICP-OES technique. The environmental market is still the largest single application of ICP spectrometers with the balance of ICP-OES vs. ICP-MS being affected by regulatory issues. The lowering of required detection limits by the US EPA several years ago has encouraged more ICP-MS acquisitions. However, recent advances toward lower detection limits for ICP-OES may challenge that shift. The big question that we face now is the effect of the current economic downturn on capital expenditures in 2009.

As far as emerging trends, I think for ICP-OES, we will see more automated quality control in the next few years. Since all detectors use some form of charge transfer device that covers a large portion of the spectrum simultaneously, it is possible to monitor lines that give us information on the state of the system such as nebulizer flow, sample uptake, and temperature.

Neubauer: ICP-MS continues to grow as people migrate from graphitefurnace AA to ICP-MS. Although there is some migration fromICP-OES to ICP-MS, these two techniques have distinctadvantages and applications which are best suited for each.Therefore, both of these techniques will always be complementaryto each other.

In emerging countries, the move from Flame AA and Graphite Furnace AA to ICP-OES is being seen. This is due to both productivity as well as performance concerns.

Spence: ICP is recognized as a mature analytical technique and its market has been growing at single-digit percentages in recent years in Western markets, and at higher rates in geographical markets whose industries have been showing stronger growth, such as China, India, and parts of Latin America. The technique is commonly employed in the routine laboratory environment as a result of its renowned capabilities for rugged multi-element analyses of liquid matrices and its underlying ease-of-use characteristics.

Recent technology innovations within ICP instrumentation in areas such as optical design and detector technology have facilitated some notable improvements in analytical sensitivity and stability and reductions in instrument footprint. However, major groundbreaking technological innovations have been relatively seldom in the optical ICP field in recent years, further demonstrating the maturity of the technique. The majority of the ICP market is now a replacement market.

ICP-MS, by slight contrast, is a maturing technique, the market for which has been experiencing moderate-to-high growth rates in recent years, again with notable increases in developing geographical territories. The technique has been widely adopted in both routine and research laboratories. It is expected that this growth will continue in the coming years and that some customers will consider replacing their ICP-OES instruments with ICP-MS. There will, however, continue to be a market for both techniques as they are complementary, having their own strengths and weaknesses and applications of greatest suitability.

What applications for ICP and ICP-MS have you most intrigued?

Wilbur: While certainly not a mainstream application yet, the use of ICP-MS coupled with laser ablation for two and three dimensional elemental imaging in biological tissues shows tremendous potential for life sciences research. The ability to map relative distributions of specific elements in organs and tissues and compare these distributions between healthy and diseased animals is a powerful tool that is just beginning to be realized.

Dulude: Although they have been around for a while now, I am most intrigued by the speciation applications of ICP-MS and ICP-OES. When interfaced with a chromatograph, ICP spectrometers have the ability to detect trace concentrations of a variety of metal species. We have long known that chromium III is a trace nutrient while chromium VI is toxic, for example. And we know that specific elemental nutrients are more easily biologically absorbed if they are properly complexed. Speciation by ICP spectrometers gives us a level of specificity and sensitivity that has been previously unavailable.

Neubauer: For ICP-MS, there have been an increasing number of inquiriesfor the analysis of elements which are not commonly measured by ICP-MS, such as Si, P, S, and Cl.

For ICP-OES, the market is more mature, but labs are being required to measure a wider variety of analytes at lower detection limits.

Spence: Recent advances in ICP instrumentation such as the significant reductions in footprint, enhanced stability, and robustness and speed of analysis capabilities have recently enabled the development of mobile laboratory environments equipped with ICP instrumentation. An interesting and emerging application area enabled by these mobile laboratories is the on-site analysis of used lubrication oils from engines and industrial machinery for wear metals, contaminants, and element additives. This emerging analytical approach enables rapid interpretation of key element concentrations in the lubrication oils to enable responsive predictive maintenance operations and to minimize costs associated with unexpected mechanical failure and the associated downtime.

An additional emerging application area relates to the growing demand for migration away from the burning of fossil fuels and the increased usage of ICP technology to determine trace element concentrations in alternative fuel sources such as biofuels. Plant-based biofuels are being increasingly utilized and are known to offer significant benefits to the environment as they approach carbon neutrality. The trace element composition of both raw and final refined products must be monitored to ensure optimal fuel quality and performance and to minimize detrimental effects such as atmospheric pollution and acid rain formation. Developments with sample introduction accessories and RF Generator technology have enabled modern day ICP instrumentation to provide powerful solutions to these analytical applications and the scope for ICP applications in this market segment is expected to grow as the use biofuels is increasingly adopted.

ICP-MS has enjoyed a flurry of research in fields related to elemental speciation in the past decade and these application areas continue to dominate current research using the technique. It remains to be seen whether speciation-ICP-MS techniques will crossover fully to the mainstream production lab market where simplicity of operation with completely integrated speciation solutions could possibly be the ultimate way forward. This is probably only likely if, for example, global environmental legislation begins to require routine speciated analyses, rather than the current approach of analyzing for the total metal, in the first instance.

The use of ICP-MS-based techniques as an element-specific detector for biological and biotechnological applications is also of increasing interest. The application of the technique in routine clinical chemistry laboratories has seen dramatic increase over the past few years, as ICP-MS has begun to replace graphite furnace AA, while at the research end, the science of metallomics – the study of metals and metal moieties in biological systems – is receiving increased press and the application of ICP-MS technology to immunoassay has seen activity.

What industry has been impacted most by advances in ICP and ICP-MS? Why?

Wilbur: Certainly the environmental monitoring industry has been most impacted by the improvements in sensitivity, robustness, ease of use, and interference control in ICP-MS in recent years. As a result, ICP-MS has nearly completely eliminated the need for secondary, high sensitivity techniques such as graphite furnace and hydride generation AA. In most cases, a single ICP-MS instrument can do the work of a combination of ICP-OES, GFAA (or hydride), and a dedicated mercury analyzer, simplifying sample preparation, analysis, and reporting, while reducing the cost and improving the data quality.

Dulude: For the reasons discussed in question two above, I believe that the biomedical industry including pharma has been most affected by recent advances in ICP spectrometry.

Neubauer: The biomonitoring, semiconductor, and solar industries have been most impacted by advances in ICP-MS, most notably the continued development of cell technology.

Labs which perform biomonitoring have been able to replace methods previously run on graphite furnace with cell-based ICP-MS. These methods and matrices are difficult to run by graphite furnace; cell-based ICP-MS provides equivalent or better results with shorter analysis times.

The goal of the semiconductor and solar industries is to minimize the impurities in their materials, which means measuring concentrations as low as possible. Cell technology allows continuously lower levels of difficult-to-analyze elements to be measured. At this point, the limiting factor for most elements is the cleanliness of the matrices, rather than limits of the instrumentation.

Spence: The environmental industry has been very much impacted by advances in both techniques. This industry is the largest segment for trace elemental analysis instrumentation and is at the leading edge of high-throughput analyses. Consequently, any advancement in technology is realized here in the first instance.

Within ICP-OES, the move from PMT to solid-state detectors was huge with regard to expanding the capability of the technique and realized massive time benefits whilst enhancing the stability of methods with simultaneous background corrections, as well as opening up the possibility of easily adding additional elements and wavelengths into an analysis, compared to older fixed channel simultaneous PMT systems. Further improvements in the speed of computers and their platform-integration helped increase productivity within labs and this saw the entire workflow process being affected, with the widespread adoption of Laboratory Information Management Systems (LIMS). Modern designs of ICP need to focus on productivity and economy. The iCAP 6000’s size, intelligent gas flow, and optical technology was designed specifically for this type of production laboratory environment and it offers significant productivity and running cost enhancements without the use of expensive accessories – this is especially prudent in the current economic climate, where cutting costs whilst increasing or maintaining productivity is important.

Within ICP-MS, labs in the environmental industry were among the first to benefit from innovations such as collision/reaction cells as their complex sample types inevitably suffered from interference problems on early generation instruments. Environmental samples typically contain high ppm to % levels of dissolved mineral elements, which also cause problems for ICP-MS in terms of suppression effects and signal drift. This industry was therefore quick to employ interface and sample introduction technologies that alleviated these problems. Furthermore, any innovations that improve speed of analysis will always be welcomed in environmental labs since they typically need to run large numbers of samples in short timescales.

More topically, the petrochemical industry is also changing and this is impacting the use of ICP instruments in the industry as we see more and more biofuel analyses – increasing numbers of governments are turning to alternative sources of fuel and we are seeing airlines such as Virgin, Air New Zealand, and Continental Airlines trialing the use of biofuel blends as an alternative flight fuel. ICP-OES is currently the technique of choice for this type of application.

Is there anything further you would like to add about ICP and ICP-MS?

Wilbur: The power of hyphenated ICP-MS in life sciences research has been well understood and exhaustively researched within the atomic spectroscopy community for a number of years. However, it is just now making inroads as a simple, useful tool into the much larger field of pure life sciences research. The reason is that ICP-MS, when used as an LC detector provides elemental selectivity and quantitative capability unavailable using other MS detectors. As this trend continues, we will likely see better integration of multi-MS techniques. We will also see more direct communication between the life sciences research community and the ICP-MS manufacturers resulting in design enhancements specifically for this industry.

Dulude: Another trend that has been revealed for both ICP-OES and ICP-MS is the decrease in size of the footprint which addresses the rising expense of laboratory real estate. I expect this trend to continue.

Neubauer: As new regulations come into existence and new sample types emerge, both ICP-OES and ICP-MS will continue to grow. Examples include the stricter lead testing regulations in children’s products, which have been implemented, and the continued development of alternative energy sources.

Spence: The most important consideration for any ICP-based instrument continues to be its reliability and the ability of the company to offer excellent support and service. Enhancements in instrument reliability look set to continue as production processes become more and more sophisticated and unit numbers produced per annum continue to rise.

With ever-increasing financial pressures on the modern day analytical laboratory, there remains a continual demand for ICP-OES instrumentation to deliver more powerful analytical performance at the lowest possible cost and with capabilities to enable the most cost-efficient sample analysis regimes. This is especially important in the current global financial climate. There is also a growing requirement for the development of more versatile ICP instruments with enhanced accessory compatibility and software tools to enable performance of an increasingly wide range of analytical applications, encompassing gaseous, liquid, and solid sample matrices using a single ICP technique. Most forthcoming innovations in ICP-OES technology are likely to be in one of the above directions.

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. However, the major challenges for ICP-MS instruments have been the formation of polyatomic interferences and the inability to cope with high levels of dissolved material in samples. The relatively recent advent of collision/reaction cells and the availability of high mass resolution ICP-MS instruments has been a major step forward for the removal of the problem of polyatomic interferences and there have been some improvements in the ability of the technique to cope with dirty samples, including improvements in plasma-vacuum interface design and sample introduction equipment and accessories. There also remains a perception that ICP-MS instruments are more challenging to use than ICP-OES instruments. Most major forthcoming innovations in ICP-MS are likely to be in one of the above directions.

There has been a continual increase in the use of solid sampling accessories such as laser ablation to enable direct sampling of solid material into the plasma for analyte quantification. These solid sampling accessories offer some interesting opportunities for the reduction of time consuming and expensive sample preparation procedures and can also enable spatial resolution of trace element concentrations within a given solid sample in contrast to the bulk analysis/steady state data acquisition regimes that are most commonly employed. Continual technological developments with laser ablation and ICP and ICP-MS detection systems are anticipated to continue fueling the development of attractive new analytical solutions for direct bulk and spatial resolution analyses of trace element concentrations in solid samples both the routine and research analytical laboratory environment.

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