Problems associated with the need for standardization in clinical spectrophotometric and fluorometric measurements

Abstract

The re is a growing dema nd in clini cal c he mi stry for ana lyses to be pe rformed in a manner aUowing compari sons of res ults among laboratories and, from time to tim e, in th e same laboratory. Reliable comparability requires adequate procedures of standardization for s pectrophotome tri c and Huorometri c instrum e nts and me thod s. Proble ms with che mi cal and instrume ntal standardization are di sc ussed.For assays wh e re th e substan ce to be measured is available in suitable form, primary c he mical standardization is justifiably popular. Re latively un sophisti cated instrume ntation can be used to compare meas ure me nts of unkn own sa mples with such standard s. Beca use primary standard s mee ting all necessary c riteria are not avai lable for many assays of clini cal significan ce, standardization mu st depend on precision and accuracy of the instrumentation used , and on acc urately co mpiled valu es of chemi cal-opti cal prope rti es for th e mate rials of inte rest. The task of co mpilation is outside the ca pability of the routine laboratory and should be provided by a reliable central agency. If an individual laboratory is to use the agency's compiled values, that laboratory mu st have available precise, accurate and reasonably inexpe nsive in strum entation along with reliabl e ab sorbance, Huorescence, and wavele ngth calibration standard s.

Fluorometric analysis

“…Various types of standard materials for luminescence measurement have been described, including organic compounds in solution (957), inorganic ions in glasses (738), and thallium-doped potassium chloride disks (740). Consideration has been given to several aspects of fluorometric standardization in clinical chemistry (677). Representative papers on the effects of various experimental parameters in fluorometry deal with temperature (572), concentration (944), excitation wavelength (52), bandwidth of exciting and emitted light (957), scattered light (668), the solvent matrix in phosphorimetry (550), and fluorescent impurities leached out of polyethylene containers of aqueous reagents (131).…”