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RESTEK Advantage
800-356-1688
New Semivolatiles Reference Mix
for Wastewater Analysis
by Gas Chromatography/Mass Spectrometry
By Katia May, Ph.D., R&D Chemist, Chris English, Environmental Innovations Chemist,
and John Lidgett, Analytical Reference Materials Manager
✔ New MegaMix™ formulation of all 54 target compounds, for fast preparation
of working solutions.
✔ Mix includes “additional” extractable Method 625 compounds.
✔ Inert, low-bleed Rtx® -5Sil MS column ensures fast analysis, reliable data.
US EPA Method 625 is a GC/MS method applicable to
analysis of organic compounds in water and soil. The
sample is serially extracted with methylene chloride
at pH >11, then at pH <2; the extract is dried, con-
centrated to 1mL, and analyzed.
Method 625 is appropriate for several classes of
chemicals: phenols, benzidines, phthalate esters, pol-
yaromatic hydrocarbons, chlorinated pesticides,
toxaphene, and Aroclor® PCBs. Our new calibration
mix, Semivolatiles MegaMix™, EPA Method 625,
combines many of these analytes in a single mix, for
faster and more convenient preparation. For com-
Figure 1 - Method 625 semivolatile analytes resolved for mass spectrometry, using an Rtx®-5Sil MS column.
pleteness, we also include target compounds listed as
“additional” in Method 625. The mixture has been
formulated carefully, to ensure maximum stability,
and two independently prepared lots are available.
The components of the mix are listed in Figure 1.
Some of the target compounds in Method 625 are
subject to thermal or chemical degradation in the
heated GC injection port. The most labile compound,
N-nitrosodiphenylamine, totally decomposes to
diphenylamine at the GC inlet. In formulating the new
MegaMix™ we have taken steps to compensate for the
degradation problem. For example, we include the
compound that is analyzed, diphenylamine, rather
than the parent compound, N-nitrosodiphenylamine,
in the mix.
Hexachlorocyclopentadiene, pentachlorophenol, 2,4-
dinitrophenol, and other compounds will degrade to
varying degrees on contact with active sites in the
injection port. To minimize this problem, we use a
Drilled Uniliner® inlet liner to prevent the sample
from coming into contact with the metal surface
below the inlet sleeve. The end of the column seals
against the tapered end of the Drilled Uniliner® inlet
liner, and the sample is channeled directly from the
liner into the column, eliminating the most active
portion of the sample flow path. A hole in the side of
the liner allows carrier gas to flow normally during
split/splitless injections.
Method 625 calls for a column that exhibits low
bleed, in addition to providing adequate analyte sep-
aration. We recommend a 30m, 0.25mm ID, 0.25µm
Rtx®-5Sil MS column (cat.# 12723) — these
columns are characterized by effective selectivity for
the target analytes, low bleed, excellent inertness,
and a high maximum operating temperature. A 30m,
0.25mm ID, 0.25µm column separates critical ana-
lyte pairs in less than 22 minutes (Figure 1).
Rtx®-5Sil MS 30m, 0.25mm ID, 0.25µm (cat.# 12723)
Sample: US EPA Method 625 Mix 1µL 10ppm (20ppm IS)
Standards used: cat. #s 31048, 31044, 31039, 31047, 31046, 31040, 31829
Inj.: 1.0µL 20psi 0.3 min. pulsed splitless (hold 0.3 min.), 4mm Drilled Uniliner ® (cat.# 21055)
Inj. Temp.: 300°C
Carrier Gas: helium, constant flow
Flow Rate: 1.0mL/min.
Oven Temp.: 35°C (hold 1 min.) to 270°C @ 18°C/min
(hold 0 min.) to 305°C @ 5°C/min. (hold 0 min.)
to 330° @ 30°C (hold 1 min.)
Det: Agilent 5973 GC/MS
Transfer Line Temp.: 280°C
Scan Range: 35-450 amu
Solvent Delay: 3.0 min.
Tune: DFTPP
Ionization: EI
1. N-nitrosodimethylamine
2. pyridine-d5 (SS)
3. 2-fluorophenol (SS)
4. pentafluorophenol (IS)
5. phenol
6. bis(2-chloroethyl)ether
7. 2-chlorophenol
8. 1,3-dichlorobenzene
9. 1,4-dichlorobenzene
10. 1,2-dichlorobenzene
11. bis(2-chloroisopropyl)ether
12. N-nitroso-di- n-propylamine
13. hexachloroethane
14. nitrobenzene-d5 (IS)
15. nitrobenzene
16. isophorone
17. 2-nitrophenol
18. 2,4-dimethylphenol
19. bis(2-chloroethoxy)methane
20. 2,4-dichlorophenol
21. 1,2,4-trichlorobenzene
22. naphthalene
23. hexachlorobutadiene
24. 4-chloro-3-methylphenol
25. hexachlorocyclopentadiene
26. 2,4,6-trichlorophenol
27. 2-chloronaphthalene
28. dimethylphthalate
29. 2,6-dinitrotoluene
30. acenaphthylene
31. acenaphthene
32. 2,4-dinitrophenol
33. 4-nitrophenol
34. 2,4-dinitrotoluene
35. diethyl phthalate
36. fluorene
37. 4-chlorophenyl phenyl ether
38. 4,6-dinitro-2-methylphenol
39. diphenylamine
40. 4,4’-dibromooctafluorophenol (SS)
41. 4-bromophenyl phenyl ether
42. hexachlorobenzene
43. pentachlorophenol
44. phenanthrene
45. anthracene
46. di-n-butylphthalate
47. 4,4’-dibromobiphenyl (IS)
48. fluoranthene
49. pyrene
50. butyl benzyl phthalate
51. benzo(a)anthracene
52. chrysene
53. bis(2-ethylhexyl)phthalate
54. di-n-octyl phthalate
55. benzo(b)fluoranthene
56. benzo(k)fluoranthene
57. benzo(a)pyrene
58. indeno(1,2,3,-cd)pyrene
59. dibenzo(a,h)anthracene
60. benzo(ghi)perylene
GC_EV00700