Standardization and Quality Assurance in Fluorescence Measurements II Bioanalytical and Biomedical Applications

In the booming ?elds of the life and material sciences, advances are taking place on all fronts and often involve the use of luminescence techniques as analytical tools and detection methods due to their high sensitivity, intrinsic selectivity,noninvasive(oratleastminimallyinvasive)character,comparative easeofuse,potentialformultiplexingapplications,andremoteaccessibilityof signals. Despite the fact that the measurement of ?uorescence—with its birth marked by the study of Sir Stokes on quinine sulfate in 1852—is not a new technique and many ?uorescence techniques have matured to a state where quanti?cation is desired, standardization of the broad variety of ?uorescence methodsandapplicationsisstillinitsinfancyascomparedtootherprominent (bio)analytical methods. It is still often overlooked that all types of ?uorescence measurements yield signals containing both analyte-speci?c and instrument-speci?c cont- butions.Furthermore,theabsorptionand?uorescenceofmost?uorophoresis sensitivetotheirmicroenvironment,andthiscanhamperquanti?cationbased on measurements of relative ?uorescence intensities as well as accurate m- surementsofabsolute?uorescenceintensities.Hence,therealizationofatruly quantitative measurement is inherently challenging. This situation renders qualityassurancein?uorometryveryimportant,especiallywithrespecttothe increasing complexity of instrumentation, and the blackbox-type of prese- day instruments and software. This may compromise future applications of ?uorescence techniques in strongly regulated areas like medical diagnostics and clinical chemistry that are within reach. As a result, there is an ever increasing need for (a) recommendations and guidelinesforthecharacterizationandperformancevalidationof?uorescence instrumentation and the performance of typical ?uorescence measurements, and (b) for an improved understanding of ?uorescence-inherent sources of error. This is closely linked to the availability of suitable and easily handled standards that can be operated under routine analytical conditions, are a- quately characterized, and meet overallaccepted quality criteria.