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Environmental Article

High Throughput of Semivolatile Samples by GC/MS

Using a 20m x 0.18mm x 0.30µm Rxi™-5ms Column

By Robert Freeman, Environmental Innovations Chemist
  • Increase productivity and sample throughput by 75%.
  • Improved resolution of benzo(b)fluoranthene & benzo(k)fluoranthene.
  • Highly inert, ultra-low bleed column is ideal for GC/MS analyses.

Analysis of semivolatile contaminants is complicated by variation in matrix type and complexity, as well as by the broad variety of chemicals tested. Extensive lists of up to 100 compounds are routinely analyzed, and potential target compounds can include aldehydes, ketones, anilines, phenols, ethers, pyridines, polynuclear aromatic hydrocarbons, and multiple types of pesticides. Coupled with the inherent complications of difficult analyses and problematic matrices, most laboratories also are challenged by trying to increase sample throughput.

Restek developed the 20m x 0.18mm x 0.30µm Rxi™-5ms capillary column to balance the demand for shorter analysis times with the need to maintain both column capacity and column efficiency. Analysis times for semivolatiles on typical 30m x 0.25mm x 0.5µm, 5% diphenyl/95% dimethyl polysiloxane columns generally range from 19 to 24 minutes. Using the short, thin film Rxi™-5ms capillary column, we have established conditions for eluting more than 90 semivolatiles, including 7 surrogates and 6 internal standards, in less than 12 minutes (Figure 1).

The new 20m x 0.18mm x 0.30µm Rxi™-5ms capillary column enables us to use an initial temperature of 55°C. By starting the analysis at a temperature 15°C higher than that used with typical 30m x 0.25mm x 0.5µm columns, we cut the oven cool-down time to 6 minutes, and reduced total analysis cycle time from 31 to 18 minutes. Cycle times were further reduced by eliminating the oven equilibrium hold time feature since the autosampler syringe rinse procedure provided an adequate interval between runs (saving another 0.5 minute/run).

Many methods, US EPA Method 8270 for example, require that specific quality assurance measures be met every 12 hours. Assuming all the required system performance checks and calibration verifications pass, there may only be a 10.5-hour window for sample analysis. Using a 20m x 0.18mm x 0.30µm Rxi™-5ms column under the conditions listed for Figure 1, a typical lab should be able to process 35 sample extracts, rather than an anticipated 20 extracts with a 30m x 0.25mm x 0.5µm column, in the same 10.5 hour analysis window. The additional 15 sample extracts per 12 hour shift represent a 75% increase in sample throughput (Table 1). We recommend you try a 20m x 0.18mm x 0.30µm Rxi™-5ms column, and see how much you can reduce your cost per analysis.


Table 1  Analyze 75% more samples with a 20m x 0.18mm x 0.30µm Rxi™-5ms capillary column.
Restek 20m x
0.18mm x 0.30µm
Rxi™-5ms column
30m x 0.25mm x 0.5µm,
5% diphenyl/95% dimethyl
polysiloxane column


Evaluation
Total run time (min.):
18
31
13 minute savings/run
  Sample analysis (min.):
12
22
  Oven cooling (min.):
6
9
Number of samples analyzed:
35
20
75% increase
(Data based on a 10.5 hour sample analysis period, following quality assurance and method performance samples, in a 12 hour shift.)


Figure 1  Analyze more than 90 semivolatiles in 12 minutes, using a 20m x 0.18mm x 0.30µm Rxi™-5ms column.
  1. 1,4-dioxane
  2. N-nitrosodimethylamine
  3. pyridine
  4. 2-fluorophenol (surr.)
  5. phenol
  6. phenol-d6 (surr.)
  7. aniline
  8. bis(2-chloroethyl)ether
  9. 2-chlorophenol
  10. 1,3-dichlorobenzene
  11. 1,4-dichlorobenzene-d4 (int. std.)
  12. 1,4-dichlorobenzene
  13. benzyl alcohol
  14. 2-methylphenol
  15. 1,2-dichlorobenzene
  16. bis(2-chloroisopropyl)
    ether
  17. a. 4-methylphenol
    b. 3-methylphenol
  18. N-nitroso-di-n-
    propylamine
  19. hexachloroethane
  20. nitrobenzene-d5 (surr.)
  21. nitrobenzene
  22. isophorone
  23. 2,4-dimethylphenol
  24. 2-nitrophenol
  25. benzoic acid
  26. bis(2-chloroethoxy)
    methane
  27. 2,4-dichlorophenol
  28. 1,2,4-trichlorobenzene
  29. naphthalene-d8 (int. std.)
  30. naphthalene
  31. 4-chloroaniline
  1. hexachlorobutadiene
  2. 4-chloro-3-methylphenol
  3. 2-methylnaphthalene
  4. 1-methylnaphthalene
  5. hexachlorocyclo
    pentadiene
  6. 2,4,6-trichlorophenol
  7. 2,4,5-trichlorophenol
  8. 2-fluorobiphenyl (surr.)
  9. 2-chloronaphthalene
  10. 2-nitroaniline
  11. 1,4-dinitrobenzene
  12. dimethyl phthalate
  13. 1,3-dinitrobenzene
  14. 2,6-dinitrotoluene
  15. acenaphthylene
  16. 1,2-dinitrobenzene
  17. 3-nitroaniline
  18. acenaphthene-d10
    (int. std.)
  19. 2,4-dinitrophenol
  20. acenaphthene
  21. 4-nitrophenol
  22. 2,4-dinitrotoluene
  23. dibenzofuran
  24. 2,3,5,6-tetra
    chlorophenol
  25. 2,3,4,6-tetra
    chlorophenol
  26. diethyl phthalate
  27. 4-chlorophenyl phenyl
    ether
  28. fluorene
  29. 4-nitroanaline
  30. 4,6-dinitro-2-methyl
    phenol
  31. N-nitrosodiphenylamine
    (diphenylamine)
  1. 1,2-diphenylhydrazine
    (as azobenzene)
  2. 2,4,6-tribromophenol (surr.)
  3. 4-bromophenyl phenyl ether
  4. hexachlorobenzene
  5. pentachloro
    phenol
  6. phenanthrene-d10
    (int. std.)
  7. phenanthrene
  8. anthracene
  9. carbazole
  10. di-n-butyl phthalate
  11. fluoranthene
  12. benzidine
  13. 3,3'-dimethyl
    benzidine
  14. pyrene
  15. p-terphenyl-d14 (surr.)
  16. butyl benzyl
    phthalate
  17. pyrene-d10 (surr.)
  18. bis(2-ethylhexyl)
    adipate
  19. 3,3'-dichloro
    benzidine
  20. bis(2-ethylhexyl)
    phthalate
  21. benzo(a)anthracene
  22. chrysene-d12 (int. std.)
  23. chrysene
  24. di-n-octyl
    phthalate
  25. benzo(b)fluor
    anthene
  26. benzo(k)fluor
    anthene
  27. benzo(a)pyrene
  28. perylene-d12 (int. std.)
  29. dibenzo(a,h)
    anthracene
  30. indeno(1,2,3-cd)
    pyrene
  31. benzo(ghi)
    perylene

GC_EV00880

Column:

Rxi™-5ms, 20m, 0.18mm ID, 0.30µm (cat.# 13409)

Sample:

US EPA Method 8270D mix: 8270 MegaMix™ (cat.# 31850), Benzoic Acid (cat.# 31879),
8270 Benzidines Mix (cat.# 31852), Acid Surrogate Mix (4/89 SOW) (cat.# 31025),
Revised B/N Surrogate Mix (cat.# 31887), 1,4-Dioxane (cat.# 31853), SV Internal Standard Mix (cat.# 31206), 10µg/mL each component (int. std. at 50µg/mL)

Inj.:

1.0µL (10ng/50ng on column), pulsed splitless: pulse 50psi / 0.2 min., 40mL/min / 0.15 min.;
4mm Drilled Uniliner® inlet liner, hole in bottom (cat.# 20756)

Instrument:

Agilent 6890 EIC

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Flow rate:

1.2mL/min.

Oven temp.:

55°C (hold 0.5 min.) to 280°C @ 40°C/min., to 330°C @ 15°C/min. (hold 2.5 min.)

Det.:

Agilent 5973 MS

Transfer temp:

280°C

Scan range:

35-550 amu

Solvent Delay:

1.65 min.

Tune:

DFTPP

Ionization:

EI

Caution: Verify the scan speed capabilities of your instrument before attempting method.