Isotope Distribution Calculator and Mass Spec Plotter

Overview

This program can calculate the isotopic distribution of a given chemical species. It can also plot either calculated or manually inputted isotopic distributions.

This program has been developed by Scientific Instrument Services as part of the Mass Spec Tools Collection. For a complete description of this program visit the Description of this Program Page. This program is still under development. If you have any comments or suggestions we would like to hear from you.

Instructions

Key in the chemical formula for which you would like to determine the isotopic distributions. Also type in the titles and the mass scale range which will be present in the final graphical output. You have the option of calculating the masses in low resolution or high resolution.

Example Chemical Formulas:

CH4

(CH3)2CHCH(CH3)2

C10H22

C6H5Cl

(CH3)2C6H4

Calculation should take upwards of a few seconds depending on the size of the chemical species.

The species is assumed neutral (mass of added/removed electrons and binding energy is not taken into account), which can have an affect on the high resolution methods.

These isotopes are supported:

• Hone (for 1H)
• Htwo (for 2H)
• Hthree (for 3H)
• Cthirteen (for 13C)
• Cfourteen (for 14C)
• Nfourteen (for 14N)
• Nfifteen (for 15N)

Note: 2/2000. Low resolution has been enabled again since we have corrected a roundoff (typically off-by-one) error that was occuring in low-resolution calculation of certain combinations of larger atoms (such as Rh). Low resolution now uses the same underlying algorithm as does high resolution. The "low resolution fast approximation" option uses basically our previous low-resolution algorithm, except that the accuracy has been increased by a factor of 10; nevertheless, some roundoff may occur in large molecules. However, for large molecules, the fast approximation algorithm is orders of magnitude faster than the standard algorithm.

2009-10-12: Added support for some labeled isotopes (e.g. Dtwo and Dthree -- see above)

2009-10-13: Rounding change: abundances now round to nearest (not round down)

Other mass spectra tools

SIS also sells the Mass Spec Calculator Pro™, a standalone Windows application. Unlike the online calculator, you are not as limited to the size of compounds that may be calculated. A demo may be downloaded.

• Molecular drawing, fragmentation, and autofragmentation
• Enhanced Isotopic Profile utility based on a completely new algorithm that calculates isotopic mass distributions for a structure.
• Elemental Formula utility calculates the possible compositions of an ion given its mass.
• Spectrum Capture utility that can automatically digitize a scanned spectrum and import it for use within MSC.

Isotope distributions can also be calculated using the Isotopes Calculator in the MS Interpreter tool in the NIST Mass Spectral Database.

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