Analysis of Basic Pharmaceuticals and Peptides on a Multi-Mode ODS Column

Bryan Evans and Itaru Yazawa, Imtakt USA (formerly Silvertone Sciences)

Analyzing basic pharmaceuticals and peptides can be challenging with conventional ODS columns. Often times, separating these compounds requires the use of ion-pairing reagents. In this paper, we present an alternative solution using Scherzo SM-C18 (Multi-Mode ODS column).

Figure 1: Multi-Mode ODS column structure.

Experimental and Results

All data was generated with a semi-micro HPLC system equipped with UV or ELS detection. Solutes were separated using LC–MS compatible conditions on Unison UK-C18 (conventional ODS) and Scherzo SM-C18 (Multi-Mode ODS consisting of ODS + anion + cation ligands, Figure 1). Figure 2 shows the separation of antidepressant drugs under acidic and neutral conditions. The data shows that ionic interaction between basic solute and the stationary phase increases at higher pH (organic composition was increased to optimize separation). Figure 3 shows the separation of anserine and related compounds. Both L-carnosine and L-anserine contain histidine and show improved retention on the Multi-Mode ODS column due to cation exchange. The nucleotide Inosine 5'-monophosphate shows improved retention due to anion exchange.

Figure 2: Basic compounds - antidepressant drugs.

Conclusion

Scherzo SM-C18 (Multi-Mode ODS) offers an alternative method to ion-pairing chromatography for basic pharmaceuticals and peptides. Scherzo SM-C18 will be useful for those looking to eliminate ion-pairing chromatography, as well as those who require an ODS column with different selectivity.

Figure 3: Anserine and related compounds.

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