Chromatography Forum

does anyone know how to sort chemical formulas based on isotope ratio distribution pattern using Xcaliber and orbistrap.

so far as I know, it's not a built-in feature of Xcalibur in the way that it's built into Bruker software. On the other hand, the Bruker version is frustratingly useless because although it gets the answer right quite a lot of the time, it's a black box and there's no cut-off where you can say "this fit is inadequate, this is not a correct identification". Or at least there wasn't when I last used it - correct me someone! Sorting in order of likelihood is sort-of nice, but you absolutely need to know how likely each formula is, if the sorted table is to be of any value.

This contrasts with accurate mass alone, where if you know your instrument and the quality of your calibration, you can say with some confidence "I know that anything with an error > X is definitely not the correct formula".

(sorry, frustrated with both Thermo and Bruker!)

in this sense, bruker is better than Xcalibur. it is always desirable to have more than one filters (even though isotope ratio error is not so clear), so you have much more confidence on the elemental composition you get.
I really have difficult time to understand why Xcalibur does not this so important feature.

so far as I know, it's not a built-in feature of Xcalibur in the way that it's built into Bruker software. On the other hand, the Bruker version is frustratingly useless because although it gets the answer right quite a lot of the time, it's a black box and there's no cut-off where you can say "this fit is inadequate, this is not a correct identification". Or at least there wasn't when I last used it - correct me someone! Sorting in order of likelihood is sort-of nice, but you absolutely need to know how likely each formula is, if the sorted table is to be of any value.

This contrasts with accurate mass alone, where if you know your instrument and the quality of your calibration, you can say with some confidence "I know that anything with an error > X is definitely not the correct formula".

(sorry, frustrated with both Thermo and Bruker!)

The Tal-Aviv isotope abundance analysis (IAA) software can invert experimental data and sort elemental formula based purely on isotope ratio distribution
http://www.avivanalytical.com/Isotope-Abundance.aspx

However it is aimed at automated analysis of Agilent GC-MS Chemstation data linked with NIST library although probably it can work with Xcalibur with ICQ.

Thanks.

The Tal-Aviv isotope abundance analysis (IAA) software can invert experimental data and sort elemental formula based purely on isotope ratio distribution
http://www.avivanalytical.com/Isotope-Abundance.aspx

However it is aimed at automated analysis of Agilent GC-MS Chemstation data linked with NIST library although probably it can work with Xcalibur with ICQ.