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its use as a preservative. It was thus determined that police authorities had
not tampered with the evidence. In support of the specificity of MS/MS,
10
scientists at Cornell University published their findings for determining
EDTA in blood. They found that the use of LC/MS/MS removes the chemical
background or interferences from the target compound of interest; in fact,
in their experiments “the blank blood plasma sample is free of all matrix
peaks” or potential interferences. They stated that MS/MS “provides the
highest specificity and the best detection level of any method currently pub-
lished.” Also, in their conclusions in reference to the O.J. Simpson trial, “The
question of blood-evidence tampering in a criminal trial has led not only to
improved analytical techniques for the determination of EDTA but also to
the demonstration that a relatively new technique (MS/MS) is ready to be
used as credible evidence in the courtroom.” The high specificity of MS/MS
has lead some scientists to consider that the results are irrefutable. 11

5.2.3.1 GC/MS and GC/MS/MS Spectra Comparison
The following figures will give the reader an insight into the difference
between regular GC/MS spectra and the daughter ion spectra obtained from

Chromatogram Plots
File: I:\data0199\file 4886.ms
Sample: 1.00 MIN SAMPLING TIME.5 MIN DESORB.GB 5/1/99 12:27 PM
Sample Notes: F6-G ASO LINE 1 PPM
Operator: D.SUTHERLAND Scan Range: 1-2008 Time Range: 0.01 - 15.00 min.
Slecl 1 7.087 m In. Scan: 11+50 han: Ion: 37 us R 10: 1023++39
B P 131 (3201387-100%) file + 886.ms 131
100%
75%
50%
25% 91 115 146
41 51 63 77 105
0%
Slecl 2 7.23 + m In. Scan: 1161 Chan: 1 Ion: +6 us R IC: 7979382
100% B P 131 (1816+8+-100%) file + 886.ms 131
75%
50%
91 146
25% 41 51 69 77 105 115 160
0%
D In Slecl 1 - Specl 2 7.087 m In. Scan: 11+5 Chan: 1 lon: 37 us R IC: 1023++39
100% Normalized 7.23 + m In. Scan: 1161 Chan: 1 lon: +6 us R IC: 7979382
50%
0%
−50%
−100%
50 75 100 125 150 175 200 m/z
M Counts file + 886 msions: 131 all
2.5
2.0
1.5
1.0
0.5
0.0
M Counts file + 886 msions: 1+6 all
0.75
0.50
0.25
0.00
6 7 8 9 minutes
1026 1135 1245 1354 Scans
Figure 5.12 Comparison of GC/MS spectra of two indane isomers (flagged in
mass ion profile): essentially identical.
© 2004 by CRC Press LLC