restekapp07 - page 53

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RestekCorporation • (800)356-1688 • (814)353-1300 •

http://www.restekcorp.com

Figure2

Ultra IBD shows excellent peak shape for amoxicillin.

Figure3

Ultra IBD shows great separation between cephalexin and cephradine, which differ only by a hydride ion.

10min.

a hydride ion to create a phenyl ring is the only structural

difference between cephradine and its side product cephal-

exin (Figure 3). Semi-synthetic processes are used to create

derivatives like cephaloridine.

Unfortunately, many penicillins and cephalosporins are acid

labile so that liquid chromatographic (LC) analysis of these

molecules only should be performed if the sample is dis-

solved in a neutral media. Furthermore, if analysis time on

the column is prolonged, breakdown of the analytes may

occur

in situ

with a mobile phase that is not at a neutral pH.

When measuring trace quantities of the analytes, especially

by LC/mass spectrometry (MS), maintaining physiological

pH near 7.4 may become important for stability and accurate

quantitation.

Discussionof Analysis

The Restek Ultra IBD phase provides greater versatility

for the LC/MS analysis of penicillins and cephalosporins

compared to a C18 column. The Ultra IBD column is

capable of providing retention for cephaloridine in reverse

phase mode with up to 45% organic solvent in the mobile

phase. A conventional C18 column loses all retention near

35% organic solvent. Unlike a C18 column, the IBD is

capable of polar interactions in a normal phase mode with

analytes that possess charged functional groups. The ability

LC_0095

LC_0094

Column:

Ultra IBD

Catalog #:

9175565

Dimensions:

150 x 4.6mm

Particle Size:

5µm

Pore Size:

100Å

Conditions:

Mobile Phase:

10mM ammonium

formate, pH 2.5:

acetonitrile (90:10, v/v)

Flow:

1.2mL/min.

Temp.:

30°C

Det.:

UV @ 270nm

Peak List:

1. cephalexin

2. cephradine

Sample:

Inj.:

10µL

Conc.:

500µg/mL

Solvent:

acetonitrile:water

(10:90, v/v)