In its most simple conception, the method of isotope dilution comprises the addition of known amounts of isotopically-enriched substance to the analyzed sample.
12.
Mixing of the isotopic standard with the sample effectively " dilutes " the isotopic enrichment of the standard and this forms the basis for the isotope dilution method.
13.
Isotope dilution is classified as a method of internal standardisation, because the standard ( isotopically-enriched form of analyte ) is added directly to the sample.
14.
An early application of isotope dilution in the form of radiotracer method was determination of the solubility of lead sulphide and lead chromate in 1913 by George de Hevesy and Friedrich Adolf Paneth.
15.
When calibration plots are markedly nonlinear, one can bypass the empirical polynomial fitting and employ the ratio of two linear functions ( known as Pad?approximant ) which is shown to describe the curvature of isotope dilution curves exactly.
16.
The NKDEP program in the United States has attempted to solve this problem by trying to get all laboratories to calibrate their measures of creatinine to a " gold standard ", which in this case is isotope dilution mass spectrometry ( IDMS ).
