direct path through "channels" between the aligned liquid crystal molecules. The researchers are currently working on the essential components of a membrane—suitable electrodes and cell devices to contain and manipulate the membrane. They are also tailoring their liquid crystals for different potential applications and are collaborating with a Welsh company, Phase Separations of Clwyd.
with a mere 100-nL internal volume. Manz emphasizes that this is only preliminary work, and although the volumes involved are large compared with the scale of CE, which runs on single-nanoliter quantities, the present system serves as a model for further studies. Electrochemiluminescence is seen when Ru(bpy)|+ is reduced by tripropylamine (TPA) (the Ru3+ is reduced to excited-state Ru2+*) at the surface of a platinum electrode in a three-electrode system. Manz and his Glowing on a small team have demonstrated the potential of their chemical chip by detecting electroscale chemiluminescence in 100 nL of the reacElectrogenerated chemiluminescence of + tants Ru2+ and TPA with a continuousflowof Ru(bpy)f is well-known but is usually carried out in standard-scale equipment for sen- the reactant mixture through the system.+ The minimum detection limit of Ru(bpy)f sitive and selective detection of a variety of 1 compounds that can be labeled—proteins or ions in just 200 nL is 5 x x0" " M, which, nucleic acid fragments, for instance. Andreas points out Manz, corresponds to 30,000 Manz, Aran Arora, and Andrew de Mello oo molecules! the Zeneca/SmithKline Beecham Centre for Manz stresses that the results, although Analytical Chemistry at Imperial College, very good, are preliminary only and use "a London (Anal. Chem. 1997,69,456 A)A nonrelevant sample". He adds, "The real however, prefer to think small and have denews at the moment is exclusively related to veloped a micromachined hybrid chip of the small volume and to the detection limit polymethylmethacrylate and acetate sheet obtained [in terms of amount of material]." GOVERNMENT
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SOCIETY
Controversial HPLC reference column project Each year, approximately 500,000 analytical HPLC columns are sold worldwide— most of them are of the Cg or Clg reversedphase type. Materials that are ostensibly the same can still vary broadly in their properties: A separation that works well on one column might not be possible on another manufacturer's column. Is there a need for a reference material that will allow "calibrations" or standardized comparisons of the properties of a given Clg stationary phase? The idea, which was hotly debated at HPLC '97 (Birmingham, U.K.), probably has as many supporters as opponents. Under the guidance of Klaus Unger of the University of Mainz (Germany), an international working party plans to develop an HPLC stationary phase and column that can be used as a reference material. Four universities (Mainz and Saarbriicken in Germany, Eindhoven in The Netherlands, and Loughborough in the United Kingdom) and five industrial partners (Eka Chemicals in Switzerland and MachereyNagel, Merck, Bischoff, and Promochem in
Germany) are participating in the project, which is funded by the European Union. The goal is to standardize and describe in detail the steps that are necessary to obtain a fully reproducible HPLC column. The reference column will be a 4-mm i.d. x 15-cm-long C18 silica-based column. The project is not intended to produce the "best" or "only" RP-HPLC column, nor will it offer anything extraordinary with regard to separations. However, it will be thefirstcolumn for which the production steps are fully described and validated in a form accessible to the public. Therefore, any manufacturer of stationary phases will be able to reproduce this material by carefully following the silica synthesis and chemical-bonding processes. The members of the working party realize that many details of a silica synthesis, such as vessel size and stirring speed, influence the properties of the material. In addition to influences from differences in the synthesis procedure, different properties can arise from differences in the Si starting material. Batches of Si are not necessarily the same from lot to lot. The process of column packing and the testing procedure will also be described.
The test mixture of compounds—which must disclose the selectivity properties of the stationary phase, including the behavior toward basic analytes, in an unbuffered methanol/water mobile phase—is being developed by the research group of Heinz Engelhardt at the University of Saarbriicken. Such a column will be viewed as a reference material that allows analytical results to be traced. The separation properties (for example, the selectivity) of other RP-HPLC materials and even of individual batches can be compared with the reference column. Proponents of the reference column believe this will facilitate the quality management and accreditation of a laboratory and the interlaboratory comparison of analytical results. One concern of the opponents is the prospect of a growing bureaucracy: Will it be necessary to standardize all separations relevant for the approval of new drugs or for any interlaboratory collaboration against the reference column? Will such tests be requested by European authorities? Will it be necessary to substantiate why the reference column was not used for the setup of a certain analytical protocol? Fritz Erni of Novartis Pharma (Basel, Switzerland) is one prominent opponent. His main concern is that further progress in stationary phase and column technology could be hampered by a "standard" material. Even if the reference column were based on the most recent technologies for silica synthesis and bonding chemistry (which seems not to be the case), Erni is convinced that developments are underway worldwide that will result in better stationary phases with improved durability, less silanol activity, fewer problems with basic analytes, expanded pH range, and improved homogeneity of the surface. Although a 4-mm x 15-cm column is better than one with 4.6-mm i.d., today's HPLC instruments can easily be used with 2-mm i.d. columns, which allow a fourfold reduction of solvent consumption (and waste production) compared with a 4-mm "standard". A real step into the next century would be the recommendation of authorities to use columns with 1-mm i.d. or less. In the meantime, research and development activities on the HPLC reference column project continue, and the debate rages on. Veronika R. Meyer
Analytical Chemistry News & Features, February 1, 1998 9 7 A
