Welcome, Guest -  Log In |  Register  |  Shopping Cart
 

Environmental Article

New Wool Ensures More Accurate Semivolatiles Analyses

By Scott Grossman, Innovations Chemist
  • Lower detection limits for 2,4-dinitrophenol with new wool for semivolatiles.
  • Improve data accuracy with complete sample transfer.
  • Extend column lifetime by reducing matrix contamination.

Ensuring success for semivolatiles analysis is dependent on several issues. The column is an important factor; however, even with a high performance column, other parameters can significantly impact final results. Liner choice is one of the most important noncolumn factors that affects end data and to take full advantage of the column's performance the analytes need to reach the column without degradation or discrimination. How much of the sample is transferred, how reproducible the transfer is, and how representative the data will be of the original sample are all influenced by injection port factors. In this article, we will demonstrate how liners with Semivolatiles Wool—a new wool, specifically designed for semivolatiles analysis—can be used to optimize the injection port for more complete sample transfer, increased accuracy, and lower detection limits.

For semivolatiles analysis, many analysts operate their inlets in the splitless mode using a single gooseneck liner to protect the vaporized sample cloud and prevent analyte breakdown during the relatively long dwell time in the hot injection port. Wool can be used in the liner to promote sample vaporization, minimize molecular weight discrimination, improve chromatography, and extend column lifetime by preventing matrix contaminants from entering the column. However, wool must be chosen with care as some types may have active sites, which can interact with target analytes and negatively affect both peak shape and response. For example, some active phenolic compounds, such as 2,4-dinitrophenol (DNP), can be completely adsorbed and not detected at all, depending on the wool that is used.

Restek's new Semivolatiles Wool was developed specifically for semivolatiles analysis. Liners with Semivolatiles Wool were compared to MS Certified Liners packed with wool, and the Semivolatiles Wool liners were found to have greater response for 2,4-dinitrophenol, allowing it to be detected at much lower levels (Figure 1). Semivolatiles Wool liners also demonstrated greater inertness through consistent results in initial analyses, i.e., very little priming was observed (Table I). While inertness was initially tested using a flame ionization detector (FID), results for mass spectrometry (MS) were also excellent (Figure 2). More than twice the required response factor for 2,4-dinitrophenol was routinely achieved when analyzing just 1ng on-column by MS (Figure 3).

An inert sample pathway allows complete sample transfer and using Semivolatiles Wool liners is key to ensuring accurate, reproducible semivolatiles data when using a wool-packed liner. This new wool outperforms analogous MS Certified Liners and can help extend column lifetime and lower detection limits for active semivolatile compounds.

Figure 1: Active compounds, such as 2,4-dinitrophenol, can be seen at lower levels with Restek's Semivolatiles Wool liners.
  1. 3-nitroaniline
  2. 2,4-dinitrophenol
  3. pentachlorophenol
  4. phenanthrene

Column:

Rxi®-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat.# 13623)

Sample:

Phenols/Anilines/Pesticides Text Mix (cat.# 35245 )

Inj.:

10ng on-column, 1.0µL splitless (hold 0.75 min.), 4mm IP deactivated gooseneck liner packed with semivolatiles wool (cat.# 20798-231.1)

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Flow rate:

1.2mL/min.

Oven temp.:

50°C (hold 3.5 min.) to 180°C @ 35°C/min. (hold 3.5 min.)
to 300°C @ 20°C/min. (hold 0.5 min.)

Det.:

FID

Transfer line temp.:

330°C

Hydrogen:

30mL/min.

Air:

400mL/min.

Nitrogen:

25mL/min.

10ng 2,4-dinitrophenol (DNP) on-column, single gooseneck liner with wool, FID analysis with phenanthrene internal standard.


GC_EV01032

Table I: Higher, more consistent responses with Restek's Semivolatiles Wool allow lower detection limits for active compounds.
Restek's Liner with Semivolatiles Wool
Replicate 2,4-DNP Area Phenanthrene Area Response Factor
1 25.1 125.9 0.199
2 26.2 125 0.210
3 29.4 135.9 0.216
4 30.7 140 0.219
    Average RF =   0.211
    STD =   0.009
    %RSD =   4.19
Competitor's MS Certified Liner with Wool
Replicate 2,4-DNP Area Phenanthrene Area Response Factor
1 7.4 162.3 0.046
2 11.8 165 0.072
3 13.5 165 0.082
4 14.8 165.6 0.089
    Average RF =   0.072
    STD =   0.019
    %RSD =   26.51

Figure 2: The inertness of Semivolatiles Wool liners, coupled with the inertness and resolution of Rxi® technology, results in excellent peak shape, resolution, and response for semivolatiles.
gc_ev01129

Column:

Rxi®-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat.# 13623)

Sample:

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) in methylene chloride, 10ng on column

Inj.:

1.0µL pulsed splitless, pulse 25psi @ 0.3min., 60mL/min. @ 0.25min, 4mm single gooseneck liner with semivolatiles wool (cat.# 20798-231.1)

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Flow rate:

1.2mL/min.

Oven temp:

40°C (hold 1.0 min.) to 280°C @ 25°C/min. to 320°C @ 5°C/min. (hold 1.0 min.)

Det.:

MS

Transfer line temp.:

280°C

Scan range:

35-550amu

Ionization:

EI

Mode:

scan

Instrument:

Agilent 7890A/5975 GC/MS

For peak listing and a printable pdf, click here.

GC_EV01129

Figure 3: Improve low level response for active compounds—more than twice the required RF for 2,4-DNP at just 1ng on column. (Extracted ion chromatogram)
  1. 2,4-dinitrophenol

Column:

Rxi®-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat.# 13623)

Sample:

8270 MegaMix® (cat.# 31850 )

Inj.:

1ng on-column, 1.0µL splitless (hold 0.2 min.), 4mm Siltek® deactivated gooseneck liner packed with semivolatiles wool (cat.# 20799-232.5, 5-pk.)

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Flow rate:

1.2mL/min.

Oven temp.:

35°C (hold 1 min.) to 280°C @ 25°C/min. to 310°C @ 5°C/min. (hold 1 min.)

Det.:

MS

Transfer line temp.:

280°C

Scan range:

35-500amu

Ionization:

EI

Mode:

scan

GC_EV01031


To order the new Semivolatiles Wool in prepacked liners, add the corresponding suffix number to the liner catalog number.

qty. IP Deactivated Liner
with Semivolatiles Wool		 Siltek Liner
with Semivolatiles Wool
each-231.1 (addl. cost)-232.1 (addl. cost)
5-pk.-231.5 (addl. cost)-232.5 (addl. cost)
25-pk.-231.25 (addl. cost)-232.25 (addl. cost)