title: Liquid chromatography-tandem mass spectrometry for analysis of intestinal permeability of loperamide in physiological buffer.
abstract: Analysis of in vitro samples with high salt concentrations represents a major challenge for fast and specific quantification with liquid chromatography-tandem mass spectrometry (LC-MS/MS). To investigate the intestinal permeability of opioids in vitro employing the Ussing chamber technique, we developed and validated a fast, sensitive and selective method based on LC-MS/MS for the determination of loperamide in HEPES-buffered Ringer's solution. Chromatographic separation was achieved with an Atlantis dC18 column, 2.1 mm×20 mm, 3 µm particle size and a gradient consisting of methanol/0.1% formic acid and ammonium acetate. The flow rate was 0.7 ml/min, and the total run time was 3 min. For quantification, two mass transitions for loperamide and a deuterated internal standard (methadone-d(3)) were used. The lower limit of loperamide quantification was 0.2 ng/ml. This new LC-MS/MS method can be used for the detection of loperamide in any experimental setup using HEPES-buffered Ringer's solution as a matrix compound.
authors.affiliation: Department of Anesthesiology, Charité, Campus Benjamin Franklin, Berlin, Germany. miriam.heydt@charite.de
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Rubelt
authors.forename: Salah
authors.initials: S
authors.lastname: Amasheh
authors.forename: Thomas
authors.initials: T
authors.lastname: Grobosch
authors.forename: Christoph
authors.initials: C
authors.lastname: Stein
mesh_terms: D002021:Buffers; D018938:Caco-2 Cells; D002853:Chromatography, Liquid; D006801:Humans; D007422:Intestines / Q000502:physiology*; D007477:Ions; D057230:Limit of Detection; D008139:Loperamide / Q000737:chemistry / Q000378:metabolism*; D008691:Methadone / Q000737:chemistry; D010539:Permeability; D012015:Reference Standards; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002021:Buffers; D007477:Ions; D008139:Loperamide; D008691:Methadone