Method of single point internal lock-mobility correction
A method of mass spectrometry is disclosed comprising passing ions through an ion mobility spectrometer and acquiring first ion mobility drift time data. A calibration function is applied to the first ion mobility drift time data to determine a physico-chemical property (e.g. CCS) of the ions. Second ion mobility drift time data is then acquired and the calibration function is applied to the second ion mobility drift time data to determine the physico-chemical property of one or more known or reference ions. The calibration function is then adjusted.
1. A method of mass spectrometry comprising:
separating a first plurality of ions including one or more known or reference ions according to their ion mobility and acquiring first ion mobility data;
applying an initial calibration function to said first ion mobility data;
determining an estimated property of said one or more known or reference ions;
comparing said estimated property with a known property of said one or more known or reference ions; and
varying said initial calibration function to generate a revised calibration function;
wherein the step of varying said initial calibration function comprises altering one or more constants or one or more coefficients or one or more terms of said initial calibration function to generate said revised calibration function;
wherein the step of varying said initial calibration function is performed in real-time during an experimental acquisition; and
wherein the step of varying said initial calibration function comprises either: (a) altering a first order coefficient or a first order term in said initial calibration function; or (b) altering a second or higher order coefficient or a second or higher order term in said initial calibration function.
2. A method as claimed in claim 1 , further comprising determining said initial calibration function using a multi-point external calibration method.
3. A method as claimed in claim 1 , further comprising determining said initial calibration function using a multi-point internal calibration method.
4. A method as claimed in claim 1 , wherein said initial calibration function relates experimentally determined ion mobility drift times of ions with a physico-chemical property of said ions.
5. A method as claimed in claim 4 , wherein said physico-chemical property comprises a conformational property of said ions.
6. A method as claimed in claim 5 , wherein said conformational property comprises a collision cross section (“CCS”) of said ions.
7. A method as claimed in claim 1 , wherein said estimated property or said known property comprises a collision cross section (“CSS”) of said ions.
8. A method as claimed in claim 1 , wherein an estimated property of said one or more known or reference ions as determined using said revised calibration function corresponds more closely with said known property of said one or more known or reference ions than an estimated property of said one or more known or reference ions as determined using said initial calibration function.
9. A method as claimed in claim 1 , further comprising:
separating a second plurality of ions according to their ion mobility and acquiring second ion mobility data;
applying said revised calibration function to said second ion mobility data; and
determining said estimated property of said second plurality of ions.
10. A method as claimed in claim 1 , wherein said one or more known or reference ions comprise one or more parent or precursor ions.
11. A method as claimed in claim 1 , wherein said one or more known or reference ions comprise one or more fragment, daughter or product ions.
12. A mass spectrometer comprising:
an ion mobility spectrometer or separator arranged and adapted to separate a first plurality of ions including one or more known or reference ions according to their ion mobility; and
a control system arranged and adapted:
(i) to acquire first ion mobility data;
(ii) to apply an initial calibration function to said first ion mobility data;
(iii) to determine an estimated property of said one or more known or reference ions;
(iv) to compare said estimated property with a known property of said one or more known or reference ions; and
(v) to vary said initial calibration function to generate a revised calibration function;
wherein said varying comprises altering one or more constants or one or more coefficients or one or more terms of said initial calibration function to generate said revised calibration function, and is performed in real-time during an experimental acquisition; and
wherein the step of varying said initial calibration function comprises either: (a) altering a first order coefficient or a first order term in said initial calibration function; or (b) altering a second or higher order coefficient or a second or higher order term in said initial calibration function.