TECHNICAL NOTE
Benefits of Using Temperature Programming on
Micro GC Fusion®
INTRODUCTION

EXPERIMENTAL

A Micro GC provides fast analysis of gas mixtures byanalyzing samples in parallel using multiple GCmodules. Traditional Micro GCs operate isothermally,
which is sufficient for fast analysis of fixed gases andlight hydrocarbons. Micro GC Fusion, the next
generation Micro GC, is capable of both isothermal andtemperature programmable operation.

In experiment 1, a natural gas calibration standard isanalyzed isothermally on an 8 m Rt-Q-Bond column.
In experiment 2, a natural gas calibration standard isanalyzed on the same 8 m Rt-Q-Bond column using atemperature programmed method. The concentrationsof the components are shown in Table 1.

Isothermal operation maintains a consistent column
temperature during the entire analysis. This has
several disadvantages, particularly when heavy (C4and above) components are present in the gas sample.
The disadvantages include:
Broad peaks for later eluting components

Carryover effect from heavier components

Longer run times when compared to temperature
rampingLower sample throughput

Temperature programming allows adjustment of thetemperature profile and ramp rate during the run.
The temperature profile of each module is optimized toelute the desired components quickly. Cool down timeis optimized in Micro GC Fusion to provide quick cycle
times, often under two minutes.
Advantages of temperature programming include:Sharper peaks for later eluting componentsExtended application range on a single columnLess carryoverHigher sample throughput

RESULTS
When used isothermally, the Rt-Q-Bond column islimited to methane through propane analysis. (SeeFigure 1.) Heavier components will stick to the column,
and an additional two to three minutes of run time isrequired to clear these components from the column.
The temperature programmed run extends theapplication range of the Rt-Q-Bond column, providing
analysis of heavier components, such as C4–C8 "plus."
These heavier components elute during the course of
the run, reducing carryover. (See Figure 2.)
A sharper peak shape, a benefit of temperature
programming, is demonstrated by comparing theretention time and shape of the propane peak in bothexperiments. Using isothermal operation, propane
elutes at 161 seconds, compared to 49.4 seconds
using temperature programming. By eluting propane
faster, the peak shape becomes sharper, providing amore accurate integration. Table 2 contains a list ofcomponent retention times.

CONCLUSION
Temperature programming on Micro GC Fusion
provides numerous advantages when compared toisothermal operation. More components can beanalyzed on a single column, with improved peak
shape and sample throughput.

1 of 3DATATable 1 Natural gas calibration standard concentration information
Component

Mole %

nitrogen

1.53

methane88.7

carbon dioxide

1.21

ethane2.99

propane2.01

isobutane

1.00

n-butane

0.996

isopentane

0.300

n-pentane

0.300

hexanes0.603

heptanes

0.320

octanes "plus"

0.0750

Table 2 Retention time comparison for the natural gas calibration standard
Number ofComponent

Name ofComponent

Retention Time (s)Isothermal

Retention Time (s)Temperature Programmed

1.

nitrogen

19.2

18.5

2.

methane

20.5

19.5

3.

carbon dioxide

25.2

22.9

4.

ethane

40.8

30.6

5.

propane

161

49.4

6.

isobutane

N/A

64.7

7.

n-butane

N/A

68.2

8.

isopentane

N/A

82.1

9.

n-pentane

N/A

84.4

10.

hexanes

N/A

86.0 to 100

11.

heptanes

N/A

101 to 119

12.

octanes "plus"

N/A

120 to 240

Benefits of Using Temperature Programming on Micro GC Fusion®

2 of 33 of 3

Benefits of Using Temperature Programming on Micro GC Fusion®

Figure 1 Chromatogram of the natural gas calibration standard—isothermal
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Column: Rt-Q-Bond, 8 m, Variable Volume Injector
Column Temperature: 50°C, isothermal
Column Head Pressure: 20 psi

Figure 2 Chromatogram of the natural gas calibration standard—temperature programmed

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Column: Rt-Q-Bond, 8 m, Variable Volume Injector
Column Temperature: 50°C (10 s)→90°C (0 s)→240°C,
Ramp Rate: 2°C/s, 2.2°C/s
Column Head Pressure: 20 psi

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