Methods for analyzing ion mobility data
View Patent ↗Disclosed herein are methods for analyzing ion mobility data. In one embodiment, a method for analyzing ion mobility spectrometry data is disclosed. The method comprises conducting a number of ion mobility scans on a sample, generating an ion map comprising a first ion line, comparing the first ion line to a standard deviation, wherein the standard deviation is calculated from the system measurement noise, and determining if the sample is a contraband substance.
1. A method for analyzing ion mobility spectrometry data, comprising: conducting a number of ion mobility scans on a sample; generating an ion map comprising a first ion line; comparing the first ion line to a standard deviation, wherein the standard deviation is calculated from a system measurement noise, said comparing comprising; identifying a first maximum drift time and a corresponding first scan index for the first ion line; calculating the standard deviation (s m ) of the first ion line; calculating a statistic for comparison (Z) using the formula:
Z
=
s
-
σ
m
(
σ
m
/
2
n
)
,
wherein s represents system measurement noise standard deviation; identifying a normal curve standard (Z a ); comparing the statistic for comparison (Z) to the normal curve standard (Z a ); and, determining if the sample is a contraband substance.
2. The method of claim 1 , further comprising determining if the first scan index is less than or equal to about 70.
3. The method of claim 1 , further comprising determining if the first maximum drift time corresponds to a sample time that is less than or equal to about 5 seconds.
4. The method of claim 1 , further comprising determining if the first maximum drift time is greater than or equal about 11 ms.
5. The method of claim 1 , further comprising: generating a second ion map comprising a second ion line; identifying a second maximum drift time and a corresponding second scan index for the second ion line; generating an acceptance window that is centered about the first scan index; and, determining if the second scan index is within the acceptance window.
6. The method of claim 5 , further comprising:
calculating a drift ratio of the first maximum drift time to second maximum drift time, wherein the drift ratio is a value; and,
determining if the value is about 0.5 to about 2.0.
7. The method of claim 6 , wherein the value is about 1.0 to about 1.75.
8. The method of claim 7 , wherein the value is about 1.19 to about 1.58.
9. The method of claim 1 , further comprising evaluating if a maximum signal level amplitude at the first scan index is greater than or equal to a specific signal level.
10. The method of claim 9 , wherein the specific signal level is about 2,000 du.
11. A method for analyzing ion mobility spectrometry data, comprising:
conducting a number (n) of ion mobility scans on a sample;
generating a first data array comprising a plurality of scan times;
generating a second data array comprising a plurality of drift times (td);
identifying an ion line using the first data array and second data array, wherein the ion line comprises a line length, a start point (start) and a stop point (stop);
calculating an average drift time (avg) for the ion line using the formula:
avg
=
∑
i
=
Start
Stop
td
(
i
)
(
Stop
-
Start
+
1
)
;
calculating a non-flatness value (Non-Flatness) using the formula:
Non
-
Flatness
=
∑
i
=
Start
Stop
td
(
i
)
-
avg
avg
*
(
Stop
-
Start
)
;
and
,
determining if the sample is a contraband substance.
12. The method of claim 11 , further comprising determining if the non-flatness value is greater than or equal to about 0.085.
13. The method of claim 11 , further comprising:
identifying a maximum drift time; and,
determining if the non-flatness value is greater than or equal to about 0.01 and if the maximum drift time is equal to or greater than about 2 ms at a scan time that is greater than or equal to about 2 seconds.
14. The method of claim 13 , wherein the non-flatness value is greater than or equal to about 0.02, wherein the maximum drift time is equal to or greater than about 4 ms, and the scan time is greater than or equal to about 4 seconds.
15. The method of claim 14 , wherein the non-flatness value is greater than or equal to about 0.0225, wherein the maximum drift time is equal to or greater than about 4.65 ms, and the scan time is greater than or equal to about 4.85 seconds.
16. The method of claim 11 , further comprising determining if the non-flatness value is less than or equal to about 0.001.
17. The method of claim 11 , wherein the non-flatness value is less than or equal to about 0.0003.
18. The method of claim 11 , further comprising:
identifying a maximum drift time; and,
determining if the ion line comprises a line length comprising about 50 to about 55 data points and comprises a maximum drift time that is at a permissible range.
19. The method of claim 18 , wherein the permissible range is about 3 to about 5 ms.
20. The method of claim 19 , wherein the permissible range is about 4 to about 4.1 ms.
21. A method for analyzing ion mobility spectrometry data, comprising: conducting an ion mobility scan on a sample; constructing a composite line set comprising a composite ion line formed by data points; determining if the composite ion line exhibits a variation in drift time that is greater than or equal to a minimum value within a scan time range; comparing the composite ion line to a known ion line, wherein the known ion line comprises known data points; calculating a match score for the composite ion line; comparing the match score to a minimum acceptable match score; and determining if the sample is a contraband substance.
22. The method of claim 21 wherein the scan time range is about 0.5 seconds to about 5 seconds and the minimum value is 0.1 ms.
23. The method of claim 22 wherein the scan time range is about 1 seconds to about 4 seconds and the minimum value is 0.2 ms.
24. The method of claim 23 wherein the scan time range is about 1.2 seconds to about 3.5 seconds and the minimum value is 0.3 ms.
25. The method of claim 21 , wherein the match score is calculated by determining the number of data points that are considered equivalent to the known data points within the scan time range.
26. The method of claim 25 , wherein the number of data points that are considered equivalent is based on a proximity of the data point to the known data point, wherein the data point and the known data point are at an equivalent scan time.
27. The method of claim 26 , wherein the proximity is determined using a Gaussian distribution.
28. The method of claim 21 , further comprising: determining if the composite ion line comprises a portion that is within a sample time window; and,
determining if the portion is within a drift time range, wherein the drift time range is centered about a segment of the known ion line within the sample time window.
29. The method of claim 28 wherein the sample time window is about 0.5 to about 5 seconds and the drift time range is +/− about 4 ms.
30. The method of claim 29 wherein the sample time window is about 1 to about 4 seconds and the drift time range is +/− about 3 ms.
31. The method of claim 30 wherein the sample time window is about 1.2 to about 3.5 seconds and the drift time range is +/− about 2 ms.