Isotope ratios, variations background

Despite the development of sophisticated instrumentation and techniques, the accurate determination of boron in biological materials is difficult at concentrations less than 1.0 mg B/kg. Problems associated with analysis of boron from biological sources include contamination from teflon vessels during microwave digestion losses due to freeze-drying variations in boron isotope ratios, standards preparation, and reagent backgrounds and instrumental interference. Inductively coupled plasma-mass spectrometry now... 

Each ion current, lots, measured with an ICP-MS instrument is biased as a result of mass discrimination, variations in detector gain and detector efficiency, and other effects. These other effects, such as background, detector dead time effects (counting devices), interferences, and matrix effects, will not be discussed here, because they vary strongly depending on the type of mass spectrometer. Discussions on these topics can be found in Chapters 2 and 3 and in the literature [38-42]. An observed isotope amount ratio, or in other words an ion current ratio, Robs.i [Eq- (6.2)], calculated for two isotopes a and b is therefore also biased. This means that every measured or observed isotope amount ratio is biased or, to put it bluntly, these observed isotope amount ratios are wrong, unless they have been corrected for all effects mentioned above. 

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