Response to “Comments on the uncertainties in isotope patterns of molecules” by J. Meija and Z. Mester (doi:10.1016/j.aca.2010.09.029)

This manuscript presents a response to a recently published article in Analytica Chimica Acta by J. Meija and Z. Mester (doi:10.1016/j.aca.2010.09.029) in which the authors comment on some aspects of our previous work entitled “Determination of the uncertainties in the theoretical mass isotopomer distribution of molecules” Anal. Chim. Acta 664 (2010) 68–76. We present here new arguments to support our previous findings and to clarify some aspects regarding to the calculation of the uncertainty of isotope patterns. The uncertainty calculations proposed by Meija and Mester for carbon-only clusters have been compared with our previously developed first-order model based on the spreadsheet approach described by Kragten (J. Kragten, Analyst 119 (1994) 2161). The results obtained in this comparison demonstrate that the Kragten procedure can be applied safely for the calculation of the uncertainties in the mass isotopomer distribution of molecules when the u average value is calculated. In addition the procedure provides good results even when the first-order error propagation law failed for some particular cases (C93 and C186 clusters).