Biomedical subjects

David Semin

Publications and source records attributed to David Semin.

3 recordsLinked to original sources

PubMed2005

Supercritical fluid chromatography tandem-column method development in pharmaceutical sciences for a mixture of four stereoisomers.

A tandem-column method using Chiralpak AD-H and Chiralcel OD-H columns was achieved for baseline separation of a mixture of chiral pharmaceutical compounds (i.e., four stereoisomers) via supercritical fluid chromatography (SFC) with a mobile phase consisting of 90% liquid carbon dioxide and 10% ethanol:isopropanol (50:50 v/v). On the contrary, this mixture (mixture A) could not be baseline separated by SFC conditions explored with individual Chiralpak AD-H and Chiralcel OD-H columns. The effects of various mobile phases on elution order, capacity factor, selectivity, and resolution were determined with mixture A on the individual aforementioned columns to develop the tandem-column method.

Chromatography, Liquid↗

PubMed2003

Rapid method development for chiral separation in drug discovery using sample pooling and supercritical fluid chromatography-mass spectrometry.

A novel strategy for rapid chiral method development has been implemented using sample pooling and supercritical fluid chromatography-mass spectrometry (SFC-MS) on four chiral stationary phases, namely Chiralpak AD and AS, and Chiralcel OJ and OD, and eight different modifier concentrations (5 to 40% methanol-0.2% isopropylamine). The screening is performed under an outlet pressure of 110 bar at 35 degrees C, and at a flow-rate of 2.5 ml/min for the initial 20 min and then ramped up to 4 ml/min and held for 4.5 min to elute all solutes from the column. The entire process is fully automated from injection to data processing, and operates unattended for 15 h overnight to obtain optimal chiral separation for multiple compounds. A unique feature of using SFC-MS to monitor chiral synthesis is the negligible interferences from achiral impurities. In addition, with SFC-MS, enantiomeric excess can be determined with much lower detection limits than UV and much shorter analysis times compared to normal-phase/reversed-phase liquid chromatography.

Amylose↗

PubMed2002

High-throughput logP measurement using parallel liquid chromatography/ultraviolet/mass spectrometry and sample-pooling.

A novel approach to high-throughput logP measurement based on liquid chromatography/ultraviolet/mass spectrometry (LC/UV/MS) is proposed. The logP value is determined by correlation with the logk value, where k is the capacity factor k = (t(r)-t(0))/t(0), with the logP value using a defined set of standards. Since the analyte retention time (t(r)) is determined from the appropriate extracted ion chromatogram (EIC), there are no interferences from impurities and this allows the pooling of multiple compounds into one injection. To ensure the accuracy and instrument robustness in a routine high-throughput environment, a simple and MS-friendly mobile phase consisting of 20 mM ammonium carbonate (pH 8.0) for basic compounds or 20 mM ammonium formate (pH 1.0) for acidic compounds, both in combination with methanol at a ratio of 45:55, is used. This approach has been successfully used on single as well as parallel multi-channel LC/UV/MS systems to screen small to large sets of lead compounds and their analogs. A high-throughput capability to analyze over 1000 compounds per day has been achieved.

Animals↗