Technology Forum: HPLC/Ion Chromatography

This month's Technology Forum looks at the topic of HPLC/Ion Chromatography Focus and the trends and issues surrounding it. Joining us for this discussion is Chris Pohl, VP and Chief Science Officer at Dionex Corporation, Larry Tucker from Metrohm-Peak, and Yuichi Fusho of Shodex.

What trends do you see emerging in HPLC/Ion Chromatography?

Pohl: Over the course of the development of ion chromatography there have been substantial changes in chromatographic performance, improvements in the selectivity, and in the range of analytes amenable to the technique. I expect we will see continued substantial advancements in this area, including phases that are more broadly applicable to a wide variety of analytes than today's phases. Already, we have seen in the last five years a significant trend toward such broad application range phases, but further improvements can be expected with recent advances in stationary phase synthesis techniques. In addition, I expect to see monolithic materials play a significant role in the future of stationary phases for ion chromatography. In the near term, their use will be focused on improved analysis speed for applications requiring gradient separations, but in the future we can expect monoliths to be broadly employed in all areas where either rapid analysis or high-resolution are important.

Tucker: We are seeing an increase in activity where hyphenated techniques utilizing IC as a separation tool coupled to mass spectrometers and ICP-MS are able to provide the answers to customers’ research questions.

Fusho: Some recent trends in IC include the analysis on small amounts of several kinds of ions at the same time, smaller IC systems for onsite analysis, and analysis on NH₄⁺, SO₃^2-, ClO₄^-.

What is the future of HPLC/Ion Chromatography?

Pohl:There has been a significant trend toward use of only two eluents in ion chromatography: hydronium eluents for cations and hydroxide eluents for anions. The substantial advantages that these eluents provide in terms of detection limit and applicability to gradient separations have placed more and more focus on development of stationary phases that work with them. It is likely that in the future, older eluents systems, such as carbonate and borate, will largely disappear from use in ion chromatography. There has been a slow but steady transition of all areas of analytical liquid chromatography to smaller internal-diameter columns. Similar trends have been seen in ion chromatography over the last decade. I expect that this trend will continue in ion chromatography, driven not by the cost savings associated with lower solvent consumption or by applications with small sample sizes, but rather by the advantages of "always on" instrumentation. By operating at low flow rates, it becomes feasible to leave an ion chromatography instrument operating around-the-clock with minimal consumption of reagents. Such an "always on" instrument is always ready, always calibrated; providing exceptional accuracy and precision while substantially improving ease of use. In the future we can expect to see a trend toward such "always on," microscale ion chromatography instrumentation.

Tucker: The future of ion chromatography is in emerging markets such as biofuels and forensic science for new opportunities. Customers are continuously looking for ease of operation through intelligent features such as the icolumn, ipump, and newer software to allow less skilled analysts to operate the system and obtain good analytical results. The existing markets are requiring simpler, more robust, easy-to-use systems which will also help expand IC into the new and emerging markets. Metrohm has introduced a number of firsts to address customer wishes including a three year warranty, ten year suppressor warranty, intelligent component IC for ease of use, and new software with intuitive user interface to simplify routine operation.

Fusho: The future of IC will include significant growth in the Asian and Canadian markets.

What is the HPLC/Ion Chromatography application area that you see growing the fastest?

Pohl: Measurement of disinfection byproduct anions in drinking water and bottled water have been a major area of growth over the past decade. I expect this trend will continue as regulatory agencies continue to regulate additional analytes and require increasingly stringent detection limits. Specifically, I expect to see a substantial increase in the use of two-dimensional separations in order to satisfy the increasingly challenging requirements of regulatory agencies for this application area.

Tucker: As we move forward, chemists will need integrated sample preparation to address matrix challenges. Work has been done in sample preparation and a number of solutions have been developed such as ultrafiltration for particulate removal, dialysis for separating ions from high solid matrices, and automatic neutralization for pH adjustment of the sample.

Fusho: IC applications areas such as the analysis of wastewater from semiconductor facilities will grow the fastest.

What obstacles stand in the way of HPLC/Ion Chromatography development?

Pohl: What is most challenging in ion chromatography development is sourcing suitable nonmetallic materials for plumbing and column hardware, with appropriate chemical compatibility and mechanical tolerances for use in analytical instrumentation. Because ion chromatography makes use of eluents that will remove the protective oxide layer from stainless steel (especially when alternating between acidic and basic eluents), it is not advisable to use stainless steel for ion chromatography instrumentation. Currently, PEEK is the material of choice for such applications, but it is not available with the same stringent dimensional tolerances as stainless steel components. This limits the column quality control specifications possible in today’s column hardware.