• Application Note

Cephalexin on Oasis MCX

Cephalexin on Oasis MCX
  • Waters Corporation
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Cefalexin antibiotic drug molecule

This is an Application Brief and does not contain a detailed Experimental section.

Abstract

This application brief demonstrates the analysis of cephalexin on Oasis MCX.

Introduction

Cephalexin is a member of the cephalosporin class of antibiotics used for the treatment of bronchitis, pneumonia, UTI’s and infections of the ears and throat. This molecule is zwitterionic, meaning it has both carboxylic acid and amine moieties. Because the molecule has ionizable functionalities that can be either positively or negatively charged, screening all 4 Oasis sorbents following the Oasis 2x4 Method is clearly the mechanism for identifying the best sorbent. Oasis MCX resulted in the best recoveries and would be used for further sample preparation method development.

Experimental

Test Conditions

Oasis MCX 10-mg plate ( P/N 186000259)

Condition:

500 μL MeOH

Equilibrate:

500 μL H2O

Load:

500 μL (250 μL rat plasma, diluted 1:1 with 4% H3PO4 in H2O)

Wash 1:

500 μL 2% HCOOH

Wash 2:

500 μL MeOH

Elute:

250 μL (125 μL x 2) 5% NH4OH in MeOH

Options:

1. Dilute 250 μL H2O with 2% FA

2. Evaporate/ Reconstitute

3. Direct inject

Inject:

10 μL

Column:

ACQUITY UPLC BEH C18 2.1 x 50 mm, 1.7 μm

Mobile phase A:

0.1% HCOOH in H2O

Mobile phase B:

0.1% HCOOH in MeOH

Flow rate:

0.4 mL /min

Injection volume:

10.0 μL

Column temperature:

45 °C

Sample temperature:

15 °C

Sample diluent:

50/50 water/methanol

Instrument:

ACQUITY UPLC with Quattro Premier

Quattro Premier

ESI+ capillary:

3.0kV

Source temp.:

120 °C

Desolvation temp.:

350 °C

Cone gas flow:

50 L /Hr

Desolvation gas flow:

700 L /Hr

Collision cell pressure:

2.59 e-3 mbar

MRM transition:

348 → 157.9

Cone voltage:

20V

Collision energy:

18eV

Results and Discussion

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