Rapid, Reliable Assay without Ion Pairing Agents
Chlorhexidine contains numerous amine functional groups that can have a detrimental effect on Peak Shape in HPLC. The USP Assay Method uses Triethylamine as an Ion Pairing Agent in the Mobile Phase for this reason. The Method developed in this Application Note uses only Formic Acid as the Mobile Phase Additive.
The Figure below illustrates how this Method avoids Peak Shape issues encountered in the USP Reversed Phase Monograph. In addition, this Method shows excellent Repeatability, shown by the five Chromatogram overlay.
Column: Cogent Diamond Hydride™, 4μm, 100Å
Catalog No.: 70000-7.5P
Dimensions: 4.6 x 75mm
—A: DI Water / 0.1% Formic Acid
—B: 97% Acetonitrile / 3% DI Water / 0.1% Formic Acid
Injection vol.: 2μL
Flow rate: 1.0mL / minute
Detection: UV @ 239nm
—Stock Solution: 1mg / mL Chlorhexidine in Methanol diluent.
—Working Solution: A 100μL aliquot of the Stock Solution was diluted to 0.1mg / mL using 900μL 50:50 Solvent A / Solvent B mixture diluent.
t0: 1.0 minute
Note: Chlorhexidine is an antiseptic which is used in a variety of common products, including contact lens solutions and mouthwash.
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