ADV01-05_1-298

tion in high-temperature analysis. They combined

the unique properties of Siltek

™

deactivation, high-

temperature fused silica tubing, and a specially syn-

thesized dimethyl polysiloxane phase to create a

non-polar capillary column with thermal stability

up to 380°C. The result is the new Stx

-1HT col-

umn, which shows significant low bleed, even at

temperatures above 340°C (Figure 1).

Total petroleum hydrocarbon (TPH) analysis is a

common test performed in environmental laborato-

ries. In addition to gasoline range and diesel range

organics (GRO and DRO, respectively), samples

often contain high molecular weight hydrocarbons

from motor oil or hydraulic fluid. To elute these

high molecular weight hydrocarbons from the col-

umn requires high oven temperatures. The Stx

-1HT

column has the necessary thermal stability and low

bleed to perform the analysis of hydrocarbons up

to C58 in approximately 50 minutes (Figure 2).

To ensure continued low-bleed performance at high

temperatures, it is critical to prevent oxygen from

entering the column. Therefore, the system should

be leak-checked before heating the column. Even a

small leak will cause air to enter and bleed to

increase. Also, we recommend using graphite fer-

Innovators of High Resolution Chromatography Products

the

in this issue

Fast Analysis of Dioxin and Related

Compounds

…pg. 6

TO-Can

™

Air

Monitoring Canisters

…pg. 7

Column Bleed and System

Contamination

…pg. 8-9

HPLC Analysis of Carboxylic Acids

…pg. 10

Analyzing Heat Levels of Spicy Foods

…pg. 11

Trident

™

Direct Guard Column System

…pg. 12

Analysis of PAHs

…pg. 13

Rtx

-OPPesticides 2 Columns

…pg. 14–15

US EPA Method 8260B Reference

Materials

…pg. 16

MESI—Membrane Extraction

Sorbent Interface

…pg. 17

Peak Performers

…pg. 18-19

Behind the Scenes

…pg. 16

800-356-1688

814-353-1300

www.restekcorp.com

Spring

’01

by Neil Mosesman, GC Columns Product Marketing Manager,

& Dinesh Patwardhan, Ph.D., Senior R&D Chemist

INTERNATIONAL

Stx

-1HT Columns

Low Bleed for High-Temperature Analysis

Advantage

Stx

-1HT

High-Temp.

Column

…pg. 1–2

Restek

On-the-Road

…pg. 3

Separating

and

Xylene Isomers

…pg. 4

New Reference Texts

…pg. 5

Analyzing high molecular weight compounds by gas

chromatography (GC) has been difficult because of

the limited thermal stability of the stationary phases

and the fused silica tubing. At temperatures above

340°C most stationary phases exhibit high bleed that

can interfere with peak identification and affect

quantitaion. In addition, the polyimide coating on

standard fused silica tubing

can become brittle at tem-

peratures above 360°C,

causing spontaneous

breakage when the column

is exposed to elevated tem-

peratures too long.

Extensive research by

Restek R&D scientists has

led to a significant innova-

✔

Thermally stable to 380°C

✔

True dimethyl polysiloxane

polarity

✔

Low bleed (<10pa @ 380°C)

✔

Unique Siltek

™

-deactivated

high-temperature tubing

Stx

™

-1HT

0 min.

30m, 0.32mm ID, 0.10µm Stx

™

-1HT

(cat.# 11709)

& 30m, 0.32mm ID,

0.10µm Rtx

-1 (cat.# 10109);

GC:

Agilent 6890;

Oven program:

100°C

to 340°C at 10°C/min. (hold 10 min.) to

360°C @ 10°C/min. (hold 10 min.) to

380°C @ 10°C/min. (hold 10 min.);

Detector:

FID @ 380°C;

Injector:

split

at 250°C;

Septum purge:

4.0cc/min.;

Carrier gas:

helium;

Split vent flow

rate:

25cc/min., 20:1 split;

Head pres-

sure:

8.0psi;

Linear velocity:

26cm/sec.;

Make-up gas flow:

45cc/min., nitrogen

Figure 1

The Stx

™

-1HT column exhibits extremely low bleed at high temperatures.

GC_EX00397,

GC_EX00396

new

picoamps

380°C

340°C 360°C