In spite of the largely increasing use of Raman spectroscopy in

research and development over the last few decades, it has, so

far, rarely been applied for quantitative measurements in analytical

chemistry and not at all as a reference measurement method

on a metrological level. Especially when it comes to critical

measurements in internationally regulated areas such as clinical

chemistry other tools such as mass spectrometry are applied. The

main factors limiting the application of Raman spectroscopy so far

have been the lack of reproducibility and sensitivity of the method.

We will describe here, how these limitations can be completely

and simultaneously overcome by the application of isotope-dilution

surface-enhanced Raman spectroscopy (ID-SERS). This chapter

describes the critical demand for SI-traceable measurements of a

high accuracy in clinical chemistry, the application of this new tool to

solve the aforementioned problem and the analytical potential of ID-

SERS beyond the limits of established analytical reference methods.

With the continuing globalization of trade and economy, the

reliability of measurement results of any kind is of increasing

importance. Traceability to recognized references, ultimately to the

International System of Units (abbreviated as SI, from the French

Le Syste`me International d’Unite´s), is an indispensable prerequisite for measurement results to be comparable and trustworthy. This

also holds for chemical measurements. Particularly in this field

decisions and agreements on life and well being of each individual

often critically depend on analytical results, be it in medical

diagnostics or by the monitoring of limit values in foodstuffs and

environmental analysis. It is the central aim of current activities

in Metrology in Chemistry to build confidence in the reliability of chemical measurements and thereby afford both trade and society

an internationally recognized metrological reference framework.