1. A method for calibrating and analyzing data from a mass spectrometer, comprising the steps of:
a. acquiring raw profile mode data containing mass spectral responses of ions with or without isotopes;
b. calculating theoretical isotope distributions for each of at least one calibration ion based on elemental composition;
c. convoluting the theoretical isotope distributions with an initial peak shape function to obtain theoretical isotope profiles for each ion;
d. constructing a peak component matrix including the theoretical isotope profiles for calibration ions as peak components;
e. performing a regression analysis between the raw profile mode mass spectral data and the peak component matrix; and
f. reporting the regression coefficients as the relative concentrations for each of the components.
2. The method of claim 1, further comprising:
g. using the relative concentrations as combination coefficients, to provide a linear combination of all calculated isotope distributions of step b.
3. The method of claim 2, further comprising:
h. calculating at least one of a peak shape function and a calibration filter through convolution and deconvolution between the results of step a. and step g.
4. The method of claim 3, further comprising:
i. when a calibration filter is calculated, applying the calibration filter to raw data from step a.; and
j. performing the convolution of step c. using a target peak shape function specified for calculation of the calibration filter in place of initial peak shape function.
5. The method of claim 4, further comprising:
iteratively repeating steps d. through j. until the relative concentrations or calibration filter or both converge.
6. The method of claim 5, where the process is iterative and includes calculating theoretical isotope profiles based on one of initial estimated peak shape functions and refined peak shape functions.
7. The method of claim 3, wherein:
k. the convolution of step c. is performed using the peak shape function.
8. The method of claim 7, further comprising:
iteratively repeating steps d. through h. and k. until the relative concentrations or calibration filter or both converge.
9. The method of claim 1, wherein baseline components are included in the regression analysis.
10. The method of claim 9, wherein baseline components are represented as linear or nonlinear functions.
11. The method of claim 1, where the regression is a multiple linear regression.
12. The method of claim 11, where the multiple linear regression is performed with weights for each mass spectral point.
13. The method of claim 11, where the multiple linear regression is performed with mass spectral centroids after peak analysis on both the profile mode mass spectral data and theoretical isotope profiles.
14. The method of claim 1, where the process is iterative and starts with initial estimated peak shape functions.
15. The method of claim 1, where the process becomes a single pass process when the relative contributions of overlapped ions are known or given.
16. The method of claim 1, where one of actual peak shape function and calibration filter is obtained by using a deconvolution operation involving actual measured mass spectral profile mode data and a linear combination of theoretically calculated isotope distributions.
17. A method for calibrating a mass spectrometer, comprising:
generating fragment ions of known elemental compositions within the mass spectrometer;
acquiring profile mode mass spectral data of the fragment ions;
calculating theoretical isotope distribution for each of the fragment ions; and
calculating mass spectral calibration filters through at least one of convolution and deconvolution involving the acquired profile mode mass spectral data and theoretical isotope distributions for said ions.
18. A method to avoid mass spectral nonlinearity in one of mass spectral calibration and mass spectral data analysis, comprising:
acquiring mass spectral data in profile mode in a mass spectral range;
measuring one of ion counts or relative abundances for isotope clusters within said mass spectral range and comparing to a nonlinearity threshold;
excluding all the mass spectral sub-regions with nonlinearity from later mass spectral calibration and mass spectral data analysis;
excluding corresponding isotopes from the theoretically calculated isotope distributions; and
performing a mass spectral calibration or mass spectral data analysis involving theoretical isotope distributions and acquired profile mode data through one of convolution, deconvolution, and regression operation.
19. A method for calibrating a mass spectrometer for higher mass accuracy than otherwise available, comprising:
operating the mass spectrometer at a slower scanning and higher resolution mode;
acquiring profile mode mass spectral data containing at least one standard ions of known elemental compositions in one or more mass spectral segments;
calculating theoretical isotope distribution for each of the standard ions; and
calculating mass spectral calibration filters through at least one of convolution and deconvolution involving the acquired profile mode mass spectral data and theoretical isotope distributions for said ions.
20. A mass spectrometer system operated in accordance with any one of claims 1 to 19.
21. A computer readable medium having computer readable program instructions readable by the computer for causing a mass spectrometer system to perform in accordance with the methods of any one of claims 1 to 19.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A circuit adapted to be responsive to an input current supplied to an input terminal of the circuit, comprising:
an input stage adapted to establish a first bias voltage at the input terminal in response to the input current;
a current stage adapted to produce at least one mirror current proportional to the input current in response to the first bias voltage and a second bias voltage;
a feedback stage adapted to produce a feedback current proportional to the input current in response to the at least one mirror current; and
a reference bias stage adapted to establish the second bias voltage in response to the feedback current from the feedback stage, whereby the first and second bias voltages track the input current.
2. The circuit of claim 1, wherein the at least one current includes a bias current and a main mirror current.
3. The circuit of claim 1, wherein the feedback stage includes:
a reference voltage stage adapted to establish third and fourth bias voltages in response to the bias current and the main mirror current; and
a current source adapted to produce the feedback current in response to the third and fourth bias voltages.
4. A bias circuit for establishing bias voltages from an input current supplied to an input terminal of the bias circuit, comprising:
input stage means for establishing a first bias voltage at the input terminal in response to the input current;
current stage means for producing a bias current and a main mirror current each proportional to the input current in response to the first bias voltage and a second bias voltage;
feedback stage means for producing a feedback current proportional to the input current in response to the bias current and the main mirror current; and
reference bias stage means for establishing the second bias voltage in response to the feedback current, whereby the first and second bias voltages track the input current.
5. The circuit of claim 4, further comprising means for setting a value of the input current supplied to the input terminal.
6. The circuit of claim 4, further comprising start-up stage means for providing a trickle-current to the reference bias stage to force the bias circuit into a stable operating condition.
7. The circuit of claim 4, further comprising shut-down stage means for selectively enabling and disabling the supply of the input current to the input terminal so as to selectively enable and disable an operation of the bias circuit, respectively.
8. A method of establishing bias voltages suitable for biasing current sources from an input current supplied to a bias circuit, comprising:
(a) receiving the input current;
(b) establishing a first bias voltage in response to the input current;
(c) producing at least one mirror current proportional to the input current in response to the first bias voltage and a second bias voltage;
(d) producing a feedback current proportional to the input current in response to the at least one mirror current; and
(e) establishing the second bias voltage in response to the feedback current of step (d), whereby the first and second bias voltages track the input current.
9. The method of claim 8, wherein step (c) comprises:
(c)(i) producing a main mirror current proportional to the input current in response to the first bias voltage and the second bias voltage; and
(c)(ii) producing a bias current proportional to the input current in response to the first bias voltage and the second bias voltage.
10. The method of claim 9, wherein step (d) comprises:
(d)(i) establishing third and fourth bias voltages in response to the bias current and the main mirror current; and
(d)(ii) producing the feedback current in response to the third and fourth bias voltages.
11. The method of claim 10, wherein:
step (b) and step (e) together comprise establishing the first and second bias voltages such that the first and second bias voltages are suitable for biasing one or more current sources of a first type; and
step (d)(i) comprises establishing the third and fourth bias voltages such that the third and fourth bias voltages are suitable for biasing current sources of a second type complementary to the first type.
12. The method of claim 8, further comprising:
supplying a trickle current to establish a stable operating condition of the bias circuit.
13. The method of claim 12, further comprising:
reducing the trickle current from an initial current value to a final current value in response to a rise in the second bias voltage indicative of the stable operating condition.
14. The method of claim 8, further comprising:
selectively enabling and disabling the circuit by selectively enabling and disabling the input current in step (a) in response to an enabledisable signal.