Analytical chemistry is concerned with the composition of materials. The Association of German Chemists gives the following, somewhat formal definition of this investigative discipline: "Chemical analysis is the science of the gain and value-related interpretation of information on materials systems by the means of natural scientific methods." The chemistry historian Ferenc Szabadváry claims to have discovered the oldest historical indication of this branch of science in the Bible. Apparently, a method for testing gold in a rational, analytical way is described in the Old Testament. One certain source of verification comes from Pliny the Elder (23-79 AD) who describes a method for testing the purity in his work Naturalis Historia. It wasn't until the 14th and 15th centuries, however, that the discipline entered the realm of science as such. Paracelsus (1493-1541) described the first form of water analysis and Leonhard Thurneysser (1530-1596) developed methods to analyse mineral baths for cures. It was Robert Boyle (1627-1691) who coined the term "chemical analysis".

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In its early years this branch of science brought forth such publications as those of A. L. Lavoisier (1743-1794), who examined gases, followed in 1790 by the "Complete Chemical Test Cabinet" from J. F. Göttling, a "practical primer on investigative and analytic chemistry", and, between 1841 and 1895, the 16 editions of the standard work by C. R. Fresenius (1818-1897) "Introduction to qualitative chemical analysis". From then on results came thick and fast: In 1859 R. W. Bunsen and G. R. Kirchhoff laid the foundations of spectral analysis, trace analysis is introduced and standards decreed.

An immense range of analytical techniques

The composition of materials is chemically analysed and determined today using titration, gravimetry and electro analysis, subjected to various, mainly chromatographical methods and then further investigated or subjected to organic elementary analyses. Physical methods, such as X-ray deflection or electron spectroscopy, which two ETH professors of chemistry, Richard R. Ernst and Kurt Wüthrich helped to develop, are also firmly established in chemical analysis. The sheer range of techniques and technology employed is truly impressive.

Moreover, it has been extended over the past few years, with biochemical methods, such as the immunoassay or methods based on chemical sensors and biosensors. Fritz Haber (1868-1934, who studied chemistry at ETH Zurich) laid the foundations for this advent with his development of the pH electrode to measure acidity. A little over thirty years ago the first biosensor to measure blood sugar levels arrived and caused a sensation in medical circles. Since then the discipline has firmly established itself.

Ten Years CCS

ETH Zurich has also made important contributions in the area. In the early 1980s Willi Simon and a wider team succeeded in producing a pH-sensitive electrode, and in 1994 the ETH chemistry professor Ursula E. Spichiger-Keller created "a membrane for the selective potentiometrical measurement of free magnesium ions in liquids". This sensor is used to measure the concentration of magnesium in human plasma and whole blood. The discovery provided ETH with the inducement to found the Centre of Chemical Sensors and Chemical Information (CCS). Last week in Technopark – where the centre is located – a two-day conference took place to celebrate its tenth anniversary.

Birthday conference: the Centre of Chemical Sensors and Chemical Information (CCS) celebrates its tenth anniversary. large

"We can look back on a lot of successes over these first ten years," says Ursula Spichiger-Keller. To date the CCS has clocked up 92 publications and over 100 presentations have been held. In all, it has also harvested ten patents, a registered trademark ("Lab in the Bag") and seven prizes. Part of the centre's generated know-how has flowed into two spin-off companies, Sensorix AG in Zurich and C-CIT AG in Wädenswil. "But there were tough times, too," says Ursula Spichiger-Keller. "Our centre is entirely self-financed. That isn't always easy."

"A.P." and the luminescence sensors

"Ursula Spichiger-Keller has done great work," thinks Amilra Prasanna, or "A.P.“ de Silva, from Queen’s University in Belfast, Northern Ireland. The chemist, renowned for his passionate lectures, belongs to the world's best luminescence sensor researchers. Already in the early 1980s he succeeded in producing selective sensors that were able to determine sodium, potassium and calcium ion content in the blood. Mark E. Meyerhoff from the University of Michigan at Ann Arbor also works on sensors for medical application. At the CCS conference he appealed for electrochemical sensors in hospitals.

Sensors for environmental analysis

Another field of application for chemical sensors is in environmental analysis. Guillermo Orellana, from the Laboratorio de Fotoquimica Aplicada of the Universidad Complutense in Madrid, for example, has developed a fibre optical sensor, which registers, selectively and sensitively, the reaction of pollutants with a ruthenium-(II)-complex. "With our product, the 'Optosen’, we can measure the oxygen content in lakes, biological oxygen requirements, hydrocarbons, ammonium ions and detergents," he says. Vinod K. Gupta from the Indian Institute of Technology in Roorkee has developed a different method. His sensor, equipped with a membrane that is sensitive to ions, can detect heavy metals, like chromium, arsenic, lead, mercury, cadmium, zinc, copper and nickel.

"Chemical sensors and biosensors have great potential," says Ursula Spichiger-Keller. For example, in food analysis where such sensors could tell whether a product is fresh. One system that might find application in this area is that of optical sensors for aldehydes and ketones. These are currently being developed at the CCS. A further product of the centre is an optical sensor film with chromogenetic peptides that selectively recognises serine proteases. "A very wide area of research," as the chemistry professors says.