ADV01-05_1-298

• 13 •

www.restekcorp.com

Porous layer open tubular (PLOT) columns com-

monly are used for the analysis of gases, low

molecular weight compounds, and volatile solvents.

In specific, PLOT columns coated with divinylben-

zene (e.g., Porapak

Q or HayeSep

Q polymers)

often are used for analyzing permanent gases such

as air, CO, CO

, and CH

; C1 to C5 hydrocarbons;

polar solvents; and C1 to C6 free fatty acids. While

most compounds exhibited symmetrical peak

shapes on the original Rt-QPLOT

™

column, polar

compounds such as alcohols often resulted in tail-

ing peaks. Additionally, active compounds such as

free fatty acids could display poor response on

Rt-QPLOT

™

columns that were not properly

deactivated.

New deactivation techniques were developed

recently to improve the performance of Restek’s

Rt-QPLOT

™

columns. As a result, peak tailing of

polar solvents has been reduced significantly. The

analysis of 11 alcohols on an Rt-QPLOT

™

column

proves that the enhanced inertness results in more

symmetrical peak shapes of alcohols and other

polar solvents (Figure 1).

Peak tailing and poor response often occur when

analyzing low molecular weight free fatty acids from

C1 to C5 on a divinylbenzene PLOT column.

Therefore, a highly inert PLOT column is required

to obtain good peak shape and response. The

improved deactivation on the Rt-QPLOT

™

column

results in excellent peak shape and response for

low molecular weight free fatty acids (Figure 2).

The Rt-QPLOT

™

column is not sensitive to moisture

and, therefore, can be used for direct aqueous

injections. To eliminate particle generation, which

can cause detector spiking, a special bonding

process immobilizes the stationary phase to pro-

duce strong, uniform particle adherence to the

✔

Improved peak shape of polar solvents.

✔

Not sensitive to moisture—can be used for direct aqueous injections.

✔

Unique particle immobilization process eliminates detector spikes.

Rt-QPLOT

™

GC Column

New Deactivation Improves Response

by Neil Mosesman, GC Columns Product Marketing Manager

Figure 1

Obtain improved peak shapes for alcohols and other polar solvents on the new

Rt-QPLOT

™

column.

Figure 2

Excellent peak shapes and response for free

fatty acids are achieved with the improved

Rt-QPLOT

™

column.

inside of the capillary tube. The Rt-QPLOT

™

columns are available in 0.32 and 0.53mm internal

diameters and in 15- and 30-meter lengths. The

0.32mm ID column has a 10µm particle coating,

and the 0.53mm ID column has a 20µm particle

coating. The maximum operating temperature for

the Rt-QPLOT

™

column is 250°C.

PLOT columns are useful for the analysis of a wide

range of volatile compounds. Because tailing and

poor response of active compounds can occur on

improperly deactivated PLOT columns, it is critical

to select a column with adequate inertness. The

new and improved Rt-QPLOT

™

column is specially

deactivated to produce excellent peak shape and

response for active polar compounds such as alco-

hols and free fatty acids. Also, the unique particle

immobilization process eliminates detector spikes.

Call the Restek Technical Service Team at ext. 4

with questions.

✔

Rt-QPLOT

™

(fused silica PLOT)

divinylbenzene Stable to 250°C

ID df (µm)

15-Meter

30-Meter

0.32mm 10

19717

19718

0.53mm 20

19715

19716

✔

MXT

-QPLOT

(metal Silcosteel

-coated PLOT)

divinylbenzene Stable to 250°C

ID df (µm)

15-Meter

30-Meter

0.53mm 20

79715

79716

min

1. acetic acid

2. propionic

3. isobutyric acid

4. butyric acid

5. isovaleric acid

6. valeric acid

30m, 0.32mm ID, 10µm Rt-QPLOT™ (cat.# 19718);

Sample:

alcohol mix;

Conc.:

1% of each compound in water;

Sample size:

1.0µL;

GC:

Agilent 6890;

Oven program:

100°C to 240°C @ 5°C/min. (hold 10min.);

Injector:

split @ 250°C;

Carrier gas:

helium (constant pressure mode);

Head pressure:

18.0psi;

Column flow rate:

1.1cc/min. @ 100°C;

Linear velocity:

31cm/sec. @ 100C;

Split ratio:

70:1;

Detector:

FID @ 270°C;

Make-up gas flow:

45cc/min.;

Inlet liner:

4mm single gooseneck (cat.# 20798)

30m, 0.32mm ID, 10µm Rt-QPLOT™ (cat.# 19718);

Sample:

atty acids mix;

Conc.:

5% of each compound

in water;

Sample size:

0.5µL;

GC:

TRACE 2000;

Oven program:

75°C to 240°C @ 10°C/min. (hold

15min.);

Injector:

split @ 240°C;

Carrier gas:

hydrogen

(constant pressure mode);

Head pressure:

12.0psi;

Column flow rate:

1.1cc/min. @ 100°C;

Split ratio:

100:1;

Detector:

FID @ 240°C;

Make-up gas flow:

40cc/min.;

Inlet liner:

3mm split w/glass wool

(cat.# 20936-202.1)

1. methanol

2. ethanol

3. 2-propanol

4. 1-propanol

5. tert-butanol

6. 2-butanol

7. isobutyl alcohol

8. 1-butanol

9. 2-methyl-2-butanol

10. 3-methyl-1-butanol

11. 4-methyl-2-pentanol

GC_CH00495

GC_FF00496