China Catches up in Monoliths for LC

Almost 20 years ago, I made my first trip to the People’s Republic of China. Over the next decade, I visited many times, working on various commercial ventures, mostly related to chromatography and other analytical instrumentation. During the trips, I observed the rapid improvement in the state-of-the-art, particularly in separation science. Initially (early 1990s), chromatography instruments were very basic gas chromatographs using packed columns. This was two decades out of date as measured by Western technology. Most of the instruments were manufactured and marketed to customers surrounding their point of production. In the West, this business model is referred to as “friends selling to friends.” Prices were very low. A GC with a packed column injector and thermal conductivity detector had an asking price of only $1000. Of course, the controls were analog, which was good enough. In HPLC, almost all instruments and columns were imported.

My trips from about 1998 through 2005 corresponded to the rapid upgrade in technology in separation science, especially HPLC. By 2005, I was no longer just teaching but observing flashes in which Chinese scientists showed innovations in the global state-of-the-art.

Unfortunately, my opportunities for on-site observation came to an abrupt halt in 2006 for personal reasons. However, I was honored to be included as a member of the Fourth Editorial Board of the Chinese Journal of Chromatography (SE PU).

I’d made many professional friends in China, so I usually reviewed the table of contents and English abstracts in each of the 12 annual issues. In just a short, five-year period, the content of the published papers improved from out-of-date to competent to global, state-of-the-art.

Flash forward another half decade to 2013. Many articles published in SE PU are truly interesting to scientists on the cutting edge. The biggest problem is that the major abstracting services refuse to report the work, since SE PU publishes in Chinese, with only an abbreviated abstract plus figure captions and references in English.

This conflict in editorial policies is bad for global science. Scientists in China who are reporting on state-of-the-art research are forced to publish in English, which often is not their native language. Some concepts and findings seem to be lost, as in Lost in Translation. Yes, the movie is set in Japan, but the analogy fits very well.

The April 2013 issue (SE PU 31[4]) arrived last week. The editorial focus was on monolithic stationary phases for liquid chromatography and solid-phase extraction (SPE).

This is a current global research topic. Column technology is important since it generally leads to instrumentation, which always struggles to catch up.

The issue starts out with an interesting review on monolith column technology by Ying Shen et al. that compares “grafting to” and “grafting from” bonding surface chemicals for adding selectivity to monolithic structures.1 The difference is the type of molecule that is grafted for the surface chemistry. In “grafting to,” a preformed polymer is grated to the activated monolith. In “grafting from,” the polymer is formed on the monolithic surface. This gives higher capacity and often higher column efficiency. The capacity is explained with an animation that compares morphology of brushes for “grafting from” to random polymer globs obtained from “grafting to.”

A second paper describes preparation and evaluation of a monolithic SPE cartridge prepared by two-step atom transfer radical polymerization (ATRP). The performance of the SPE cartridge was evaluated for SPE of steroids. The capacity was higher than obtained by grafting preformed polymers to the activated monolith. The process seems to be generally useful for bonding high-capacity surface chemistry to surfaces such as open tubular capillaries. 2

Dr. Ligai Bai reviews applications of polymeric monoliths for the separation of biomacromolecules.3 Most of the work was done in his lab. Photomicrographs show a wide range of morphology.

Junjie Ou is the lead author on a report on preparation and evaluation of polyhedral oligomeric silsesquioxanes as the base polymer in monolithic columns.4 Porous monolithic beds were prepared by free radical polymerization in the presence of poragens. Test chromatograms show 30-μm plate heights with symmetrical peaks for alkyl benzenes.

Since boronate affinity chromatography is attractive for the separation of cis-diol analytes, several have tried to make monolithic stationary phases for chromatography and SPE. A report by Yunchun Liu describes synthesis of boronate affinity monolithic columns using highly symmetrical monomers (melamine and tris(2,3-epoxypropyl) isocyanurate).5 The copolymer had a high specific surface area (80 m2/g).

Lin Sun describes synthesis and evaluation of a molecularly imprinted stationary phase for enrichment and assay of trace cytokinins, which are plant hormones. The stationary phase was prepared in a stainless steel tube by polymerizing a mixture of the template (kinetin) with methylacrylic acid, ethylene dimethacrylate, plus toluene, plus dodecanol as poragens. The imprinted polymer showed selective retention of cytokinins, with detection limits as slow as 16 ng/L using UV detection.6

China’s research into improving liquid chromatography is on the lead lap along with the traditional technology leaders. To have closed the gap in less than 20 years is truly remarkable. Congratulations to all participants.

For entrepreneurs in the developed world, the time has come to start looking at China for products and technology to import. Today, China is more than just an inexpensive source of commodity products.

References

  1. Shen, Y.; Qi, L. et al. Development of intelligent monolithic stationary phase for chromatography. SE PU 2013, 31(4), 290–6.
  2. Shen, Y.; Qi, L. et al. Preparation of a novel polymer monolith using atom transfer radical polymerization method for solid phase extraction. SE PU 2013, 31(4), 317–21.
  3. Bai, L.; Niu, W. et al. Applications of polymeric monoliths in separation of bio-macromolecules. SE PU 2013, 31(4), 303–9.
  4. Ou, J.; Lin, H. et al. Preparation and modification of polyhedral oligomeric silsesquioxane-containing hybrid monolithic capillary columns. SE PU 2013, 31(4), 322–8.
  5. Liu, Y.; Liu, Z. Preparation of boronate affinity monolithic column with high specific surface using highly structurally symmetrical copolymerizing reagents. SE PU 2013, 31(4), 348–51.
  6. Sun, L.; Du, F. et al. Monolithic molecularly imprinted column-high performance liquid chromatography for enrichment and determination of trace cytokinins in plant samples. SE PU 2013, 31(4), 392–4.

Robert L. Stevenson, Ph.D., is a Consultant and Editor of Separation Science for American Laboratory/Labcompare; e-mail: rlsteven@yahoo.com.

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