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Environmental Article

Separate Explosives and Propellant Residues

Using Ultra C18 and Pinnacle™ II Biphenyl Columns

by Robert Freeman, Environmental Innovations Chemist
  • Excellent resolution, improved accuracy.
  • Easily quantify and confirm new US EPA Method 8330B target analytes.
  • Simple, easy to use, isocratic method.

US EPA 8330, a test method for determining trace amounts of 14 nitroaromatics, nitramines, and nitrate esters, was recently revised to include three new target analytes. The new method, EPA 8330B, includes nitroglycerine (NG), pentaerythritol tetranitrate, (PETN), and 3,5-dinitroaniline (3,5-DNA) and now covers 17 analytes that are commonly found in explosive and propellant residues. This method uses reversed phase HPLC and dual wavelength UV detection (210 & 254nm) in conjunction with a primary and a confirmation column.

We recently assessed the performance of our current column offerings relative to the elution order and retention times of the new analytes in the revised method. Separations on all columns were accomplished using a simple, isocratic water:methanol mobile phase (Table 1). The primary and confirmation columns that we currently recommend for the analysis of EPA 8330 are the Ultra C18 and Pinnacle™ II Biphenyl columns, respectively. Based on this work, this combination will continue to work well for the revised method, EPA 8330B, as shown by the chromatograms in Figures 1 and 2. Both columns provide excellent resolution of the EPA 8330B analytes and their differing selectivity provides a true confirmation analysis.

As an alternative to the Ultra C18/Pinnacle™ II Biphenyl combination, a Pinnacle™ II C18 column and a Pinnacle™ Cyano column work well together as a primary-confirmation column set. Another column of interest is the Allure® Biphenyl column. A high organic mobile phase was required on this column but the analysis was completed in approximately six minutes (Table 1).

Restek can provide the tools necessary to perform your explosives analysis — including the recent changes to EPA Method 8330B. For this method, we recommend an Ultra C18 / Pinnacle™ II Biphenyl column pair, for dependable results for all target analytes.

Table 1  Retention times for EPA 8330B analytes on various Restek columns; new target analytes are shown in red, highlighted cells indicate coelution.
Primary Columns
Confirmation Columns
Mobile
H2O:MeOH
50:50
44:56
45:55
50:50
20:80
Phase
Flow
1.5 mL/min.
1.0 mL/min.
1.2 mL/min.
1.5 mL/min.
1.5 mL/min.
Analytes
Pinnacle™ II C18
Ultra C18
Pinnacle™ II Biphenyl
Pinnacle™ II Cyano
Allure® Biphenyl
1
HMX
2.29
3.38
2.76
18.65
1.61
2
RDX
3.63
5.41
3.22
9.38
1.75
3
1,3,5-TNB
4.89
7.39
14.54
4.78
5.69
4
1,3-DNB
5.94
8.82
9.26
4.59
3.92
5
3,5-DNA
6.63
9.71
5.73
6.34
2.30
6
tetryl
6.97
9.71
16.12
11.47
4.42
7
NB
6.97
9.88
6.31
3.80
2.79
8
2,4,6-TNT
8.23
11.69
20.17
5.94
6.22
9
NG
8.23
11.69
4.94
8.52
1.98
10
2-A-4,6-DNT
8.94
12.05
7.43
7.24
2.50
11
4-A-2,6-DNT
8.94
12.61
7.02
6.34
2.41
12
2,6-DNT
9.73
13.27
12.36
5.10
4.09
13
2,4-DNT
9.73
13.64
15.46
5.58
5.14
14
2-NT
11.92
15.92
9.73
4.38
3.40
15
4-NT
12.76
17.05
11.07
4.38
3.72
16
3-NT
13.74
18.32
11.07
4.38
3.73
17
PETN
16.13
21.08
10.43
17.24
2.67


Figure 1  Excellent resolution of EPA 8330B target analytes on the Ultra C18 column.

 
Ret. Time
(min.)
  1. HMX
  2. RDX
  3. 1,3,5-TNB
  4. 1,3-DNB
  5. 3,5-DNA
  6. NB
  7. tetryl
  8. 2,4,6-TNT
  9. NG
  10. 2-A-4,6-DNT
  11. 4-A-2,6-DNT
  12. 2,4-DNT
  13. 2,6-DNT
  14. 2-NT
  15. 4-NT
  16. 3-NT
  17. PETN
  •   3.38
  •   5.41
  •   7.39
  •   8.82
  •   9.71
  •   9.71
  •   9.88
  • 11.69
  • 11.69
  • 12.05
  • 12.61
  • 13.27
  • 13.64
  • 15.92
  • 17.05
  • 18.32
  • 21.08

Column:
Ultra C18
Cat.#:
9174575
Dimensions:
250mm x 4.6mm
Particle size:
5µm
Pore size:
100Å
Sample:
50µg/mL each compound diluted in acetonitrile
8330 Calibration Mix #1 (cat.# 31450)
8330 Calibration Mix #2 (cat.# 31451)
PETN Standard (cat.# 31600)
3,5-dinitroaniline Standard (cat.# 31661)
Nitroglycerin Standard (cat.# 31498)
Inj.:
10µL
Conditions:
Mobile phase:
water:methanol (44:56 v/v)
Flow:
1.0mL/min.
Temp.:
30°C
Det.:
UV detection @ 210nm

LC_EV0428

Figure 2  Alternate selectivity of EPA 8330B analytes on the Pinnacle™ II Biphenyl column confirms compound identity.

 
Ret. Time
(min.)
  1. HMX
  2. RDX
  3. NG
  4. 3,5-DNA
  5. NB
  6. 4-A-2,6-DNT
  7. 2-A-4,6-DNT
  8. 1,3-DNB
  9. 2-NT
  10. PETN
  11. 3-NT
  12. 4-NT
  13. 2,6-DNT
  14. 1,3,5-TNB
  15. 2,4-DNT
  16. tetryl
  17. 2,4,6-TNT
  •   2.76
  •   3.22
  •   4.94
  •   5.73
  •   6.31
  •   7.02
  •   7.43
  •   9.26
  •   9.73
  • 10.43
  • 11.07
  • 11.07
  • 12.36
  • 14.54
  • 15.46
  • 16.12
  • 20.17

Column:
Pinnacle™ II Biphenyl
Cat.#:
9209565-700
Dimensions:
250mm x 4.6mm
Particle size:
5µm
Pore size:
110Å
Sample:
50µg/mL each compound diluted in acetonitrile
8330 Calibration Mix #1 (cat.# 31450)
8330 Calibration Mix #2 (cat.# 31451)
PETN Standard (cat.# 31600)
3,5-dinitroaniline Standard (cat.# 31661)
Nitroglycerin Standard (cat.# 31498)
Inj.:
10µL
Conditions:
Mobile phase:
water:methanol (44:55 v/v)
Flow:
1.2mL/min.
Temp.:
30°C
Det.:
UV detection @ 210nm

LC_EV0429