Mrs/Miss Iyer,

First of all, quantification of analytes both organics and inorganics in vitro and in vivo can be carried our reliably by mass spectrometric methods, instead of, by Fs; due to (i) significant error contribution to the chemometric parameters from data-processing of the Fs patterns; as well as (ii) the high method performances of Fs such as LODs and LOQs.

Second, the quantification by mass spectrometry, can be ccried out highly reliably (correlation coefficients within r = 0.99996 - 1) using our stochastic dynamic concept and model formulas developed, more recently [1]-[3], where the analysis can be done directly in solution evaluating the MS intensity of the analytes per span of the scan time. The method has been tested on mixture of 4 steroids at ng.(L)-1 and pg.(mL)-1 concentration levels (reference [1].)

[1] Book QUANTITATIVE RELATIONS AMONG TEMPERATURE, ANALYTE CONCENTRAT...

[2] A mass spectrometric stochastic dynamic diffusion approach to selective quantitative and 3D structural analyses of native cyclodextrins by electrospray ionization and atmospheric pressure chemical ionization methods, Bioorganic Chemistry, 9, 2019, 103308, Bojidarka Ivanova, Michael Spiteller

[3] https://zenodo.org/record/3606820#.XpFyTUAzaig

You should bear in mind that this approach improves significantly the method performances of th emass spectrometry, instead of, using the standard quantitative protools as they have been implemented into the EU Directive 2002/657/EC; https://eur-lex.europa.eu/legal-content/DE/ALL/?uri=CELEX%3A32002D0657; Official Journal of the European Communities L 221/8 , 17.8.2002 employed within the EU member Countries.

In addition, currently, we have developed even more symplistic model equation (derived from the same theoretical framework) which reduces the calculation tasks (Consider reference [2],) which also shows very high reliability of the date (a work submitted for consideration.)

Therefore, the more recent research on the soft-ionization methods of mass spectrometry and developments of methods for MS data-processing show that this is the method of choice for quantification; rather than optical spectroscopic approaches and tools.