A sensitive determination method for a non-fluorescent anti-arrhythmic drug, mexiletine, in rat plasma is presented utilizing a HPLC peroxyoxalate chemiluminescence (PO-CL) detection system. After an internal standard (4-methylmexiletine, 4.35 pmol) and 0.1 N sodium hydroxide solution were added to 5 microL rat plasma, the solution was poured onto an Extrelut 1 column. Both mexiletine and the internal standard were eluted with diethy ether and then the eluate was evaporated to dryness. The residue was dissolved in 0.2 M borate buffer (pH 8.5) and mixed with dansyl chloride (75 nmol) in acetronitrile. After standing of 90 min at room temperature, 0.5 N HCl was added to the reaction mixture to stop the reaction and a 2/45 aliquot of the mixture was subjected to a HPLC PO-CL detection system using bis(4-nitro-2(3,6,9-trioxadecyloxycarbonyl)phenyl) oxalate (TDPO) and hydrogen peroxide. The calibration curve for mexiletine in rat plasma was linear over the range 20-100 ng/mL plasma (20.6-103 fmol/injection). The detection limit (S/N = 2) was 1.0 fmol over the whole procedure. The method was applied to the measurement of the time courses of plasma mexiletine concentration after oral administration of the drug [25 mg (115.9 mumol)/kg] to rats.

Animals↗

PubMedDate not supplied

Development of a chemiluminescence detection system using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate for the sensitive determination of the fluorescent compounds separated with an acidic mobile phase.

A rotating flow mixing device having three directional inlets was developed for a high performance liquid chromatographic peroxyoxalate chemiluminescence detection system for the sensitive detection of fluorescent compounds separated with acidic mobile phases, such as those containing trifluoroacetic acid. The diameters of the three inlets were 0.3, 0.3 and 0.5 mm i.d., for an acidic column eluate, chemiluminogenic reagents (bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl) phenyl] oxalate and hydrogen peroxide) and imidazole solution (for neutralization and as a catalyst), respectively. The three mixed solutions flowed out through an outlet (0.5 mm i.d.) at the centre of the top of the vessel. The reaction conditions to give the appropriate signal-to-noise ratio (S/N) were investigated using dipyridamole (an antiplatelet aggregation drug) as a typical fluorescent compound. The system was applied to the detection of dipyridamole and dansylated amino acids with a mobile phase containing trifluoroacetic acid. The detection limits for dipyridamole and each dansylated amino acid were 10 amol and sub-fmol (S/N = 2), respectively.

Amino Acids↗