Packed column supercritical fluid chromatography of a peroxysome proliferator-activating receptor agonist drug. Achiral and chiral purity of substance, formulation assay and its enantiomeric purity.
This paper describes packed column supercritical fluid chromatography (SFC) for the analysis of a peroxysome proliferator-activating gamma-receptor agonist that is a carboxylic acid. Evaluation of conditions for the separation of this candidate drug and related compounds in bulk substance is described. A Chiralcel OD column was used for this purpose due to its high selective retention of related substances and relative inertness, though the enantioselectivity was negligible, with methanol as polar modifier. A high enantioselectivity was obtained on Chiralpak AD and it was possible to determine the enantiomeric purity within 10 min on a 5 cm short column. Both the achiral and the chiral systems were run without acid additive in the mobile phase and the level of detection of impurities by area was about 0.1%. For the analysis of samples dissolved in water, without any isolation step, 2-propanol was used as modifier. Due to the column surface activity, evidently generated by injected water, citric acid 1 mM was included as additive in the 2-propanol in order to maintain symmetric and undistorted peak shape. The detection limit for the assay was 21 microg mL(-1) (50 nmol mL(-1)) for 5 microL injected (R.S.D. 6.4%, n = 8). A 5 cm short Chiralcel OD column was used. Determination of enantiomeric purity of the drug in aqueous samples required increased sensitivity. The sample was acidified and extracted into a small volume of 1-pentanol, out of which 25 microl was analyzed by SFC. The minor enantiomer at the 3% (w/w) level added could be confirmed. Its ratio remained constant during the procedure as measured relative to a reference solution in organic media.
Gyllenhaal
Olle
O
Analytical Development, AstraZeneca R & D Mölndal, S-431 83 Mölndal, Sweden. olle.gyllenhaal@astrazeneca.com
D002021:Buffers; D002626:Chemistry, Pharmaceutical; D002853:Chromatography, Liquid; D004340:Drug Contamination; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007475:Ion Exchange Resins; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D012996:Solutions; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013644:Tartrates; D014157:Transcription Factors / Q000819:agonists*; D014867:Water / Q000032:analysis
D002021:Buffers; D007202:Indicators and Reagents; D007475:Ion Exchange Resins; D018160:Receptors, Cytoplasmic and Nuclear; D012996:Solutions; D012997:Solvents; D013644:Tartrates; D014157:Transcription Factors; D014867:Water