ADV06-15_1-412

When performing GC/MS analysis of drugs, many chemists choose to derivatize samples prior to analysis. Derivatization not only increases the volatil-

ity of some drug compounds, but it also reduces activity, resulting in improved peak shape andmore accurate quantification. An additional advantage

is that derivatized compounds have a higher molecular weight, thus producing more reliable mass spectra than underivatized compounds. Despite

these benefits, derivatization reagents are often

harsh and can damage analytical columns, lead-

ing to high bleed, significant reduction in reten-

tion times, and increased tailing for active com-

pounds. Often, this damage is concentrated

near the head of the column, so trimming a

short length can improve results. However, trim-

ming is a finite solutionas repeated clippingulti-

mately results in decreased efficiency and short-

er column lifetimes. Choosing a more rugged

column, such as the Rxi®-5Sil MS column, is a

better alternative. The Rxi®-5Sil MS column is

extremely stable and holds up to harsh treat-

ment, including repeated exposure to derivati-

zation reagents.

The analysis of amphetamine illustrates the

ruggedness of the arylene-based Rxi®-5Sil MS

polymer. Amphetamine is typically derivatized,

because the underivatized form is an active

basic compound that produces only a few low

molecular weight ions for monitoring. In con-

trast, upon derivatization, activity decreases,

resulting in dramatically improved peak shape

and more accurate quantitation. Additionally,

several higher molecular weight ions are pro-

duced, which can be monitored for definitive

identification.

By Amanda Rigdon, Clinical/Forensic Innovations Chemist and Gary Stidsen, GC Columns Product Marketing Manager

• Save costs with long column lifetime.

• Reduce downtime from column trimming and replacement.

• Improve peak shape for active compounds.

Clinical Forensic

Column:

Rxi

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

Sample:

Column Test Mix (cat.# 35226)

Inj.:

1.0 µL split (split ratio 1:60), 4 mm recessed

gooseneck liner (cat.# 20983)

Inj. temp.:

250 °C

Carrier gas:

helium, constant pressure

Linear velocity: 36 cm/sec @ 125 °C

Oven temp.:

125 °C

Det:

FID @ 320 °C

Instrument:

Agilent 6890

1. 2-ethylhexanoic acid

2. 1,6-hexanediol

3. 4-chlorophenol

4. tridecane

5. 1-methylnaphthalene

6. 1-undecanol

7. tetradecane

8. dicyclohexylamine

Figure 1

Rugged Rxi®-5Sil MS columns produce consistent retention times, even after

400 injections of derivatization reagent.

GC_CF01131

Rugged Rxi®-5Sil MS Columns Stand up to Derivatization

Reagents, Reducing Downtime and Replacement Costs

www.restek.com

Website :

www.chromtech.net.au

E-mail :

info@chromtech.net.au

TelNo : 03 9762 2034 . . . in AUSTRALIA