Normal Phase HPLC
Normal-phase chromatography (NP-HPLC) separates molecules on the basis of differences in the strength of their interaction with a polar stationary phase. The components of the analyte mixture pass over stationary-phase particles bearing pores large enough for them to enter, where interactions with the polar surface removes them from the flowing mobile-phase stream. As the concentration of polar solvent in the eluant increases, it reaches a critical value for each analyte which desorbs it from the polar stationary-phase surface and allows it to elute from the column in the flowing mobile phase. Since this elution depends on the precise distribution of polar residues in each species, each analyte elutes from the column at a characteristic time, and the resulting peak can be used to confirm its identity and quantify it.
Varying types of NP-HPLC columns are available with different pore sizes and polar coatings, allowing the investigator to manipulate the strength of the analyte-stationary phase interaction. Typically, bare silica or silica derivitized with small organic ligands are used for NP-HPLC. Additionally the steepness of the polar mobile-phase gradient can be varied to alter the sample binding characteristics and analyte retention times.
At Analytical Ventura, we vary the NP-HPLC parameters to maximize the separation of your analyte while optimizing the resolution, column capacity, and run time, among other things. Additionally, we can combine NP-HPLC with other types of chromatography to develop a comprehensive purification and analysis strategy for your product. We also offer ESI-MS services coupled to NP-HPLC to assist us in elucidating the identity and structure of your product and any contaminants or degradants.