Abstract
This paper examines the limits of accuracy in reporting isolated
product yields (i.e., recovery of total mass from chromatography
or extractions) as well as ratios of isomers determined by HPLC,
GC, or NMR methods. Attention is directed to the magnitude of errors
encountered in the HPLC or GC measurements of such ratios when these
measurements are conducted without accurate calibrations or determinations
of response factors for the particular isomers. Accurately defined
mixtures of compounds (prepared by volumetric means) were examined
by the above methods and the obtained measurements compared with
the actual composition. The relative errors between actual content and the measured values are listed for all
comparisons. In addition, accuracy in the determination of weight
of a sample as a function of scale was also examined. The results
are tabulated for comparison and suggestions are made to the reader
as to how to avoid inaccurate reporting of experimental parameters.
The authors hope that disclosure of these facts will result in new
editorial policies requiring that a phrase ‘dr or er ratios reported in this paper
have not been validated by calibration ’ be inserted
into general experimental descriptions. In addition, such editorial
policy should also discourage the use of terms ‘de’ and ‘ee’ , as these descriptors do
not provide accurate and meaningful information about stereoisomer
composition. This latter issue has already been suggested in the
literature on several occasions.
1 Introduction
2 On the Question of Isolated Product Yields
3 On Determination of Accurate Weights
4 On the Question of Accurate Detection of Stereoisomer Ratios
5 Conclusion
Key words
accuracy of determination of ratios of stereoisomers - accuracy
of weighing - accuracy of product yield determination - product content determination - errors in reporting
of analytical data
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