ABSTRACT
A simple and sensitive method was developed for quantitation of obeticholic acid in rat plasma with liquid chromatography-tandem mass spectrometry (LC-MS/MS). After liquid-liquid extraction by methyl tert-butyl ether, the chromatographic separation was carried out on an ACE Excel 2 Super C18 column (50 mm×2.1 mm ID, 1.7 μm) with a gradient mobile phase consisting of acetonitrile and 2 mmol·L-1 ammonium formate at a flow rate of 0.2 mL·min-1. The quantitation analysis was performed using multiple reaction monitoring (MRM) at the specific ion transitions of m/z 418.9[M-H]-→401.2 for obeticholic acid and m/z 469.0[M-H]-→ 425.2 for glycyrrhetinic acid (internal standard) in the negative ion mode with electrospray ionization (ESI) source. This validated LC-MS/MS method yielded a good linearity over the range of 5 -5 000 ng·mL-1 with the lower limit of quantitation (LLOQ) of 5 ng·mL-1. The intra and inter-assay precisions (RSD) were all less than 9.82% and the accuracy (RE) was within ±6.90%. The extraction recovery of obeticholic acid was from 85.4% to 88.5%, and the matrix effect of obeticholic acid ranged from 78.9% to 82.5%. Stability test suggest that obeticholic acid in rat plasma was stable for 24 h on workbench, up to 1 month at -70℃, and after three cycles of freeze-thaw. Extracted samples were stable for more than 24 h in an auto-sampler at 6℃. The precision was less than 7.25%, and the accuracy was within ±11.2%, after being diluted 10 times by blank rat plasma. The method has been successfully applied to a pharmacokinetic study of obeticholic acid in rats following oral administration at the dose of 2.5 mg·kg-1.
ABSTRACT
A pre-column derivatization method combined with UHPLC-MS/MS was developed for the simultaneous determination of salidroside and tyrosol in Beagle dog plasma. After protein precipitation by acetonitrile, the liquid supernatant was treated with dansyl chloride under dark conditions at 60℃ for 30 min, and then, the sample solution was extracted using methyl tertiary butyl ether. The multiple reaction monitoring in positive ion mode was used for MS detection of the tested analytes with the specific ion transitions of m/z 534.2→372.0 for salidroside derivative, m/z 372.0→171.0 for tyrosol derivative and m/z 506.0→171.0 for arbutin derivative. The chromatograph separation was achieved on an ACQUITY UPLC® BEH C18 column (100 mm×2.1 mm, 1.7 μm) with a gradient mobile phase consisting of acetonitrile (0.1% formic acid)-water (10% acetonitrile, 0.1% formic acid) for 9 min. The assay showed a good linearity over the range of 0.02/0.1-20/10 μmol·L-1 with a lower limit of quantitation of 0.02 and 0.1 μmol·L-1 for salidroside and tyrosol in dog plasma, respectively. The intra-and inter-day precisions were all less than 8.68%, and the accuracy was within ±11.4%. The established method with a high sensitivity, good specificity and reliability was appropriate for simultaneous determination of salidroside and tyrosol in dog plasma and successfully applied to a pharmacokinetic study after intragastric administration of salidroside to Beagle dogs.
ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the access to the frontal recess by identifying the agger nasi cell and uncinate process.</p><p><b>METHODS</b>Forty-seven patients (85 sides) who underwent endoscopic frontal sinus surgery in our department constituted the study population. Computed tomographic (CT) scans of the sinuses were obtained in coronal and axial views. The frontal ostium was identified by using agger nasi cell approach or identifying the uncinate process.</p><p><b>RESULTS</b>The frontal sinus ostium was identified in 100% of patients (85 sides). After an average follow-up of 9 months, 41 sides of 49 sides (84%) had endoscopically healed sinuses by using agger nasi cell approach. And 21 sides of 36 sides (81%) had endoscopically healed sinuses by identifying the uncinate process.</p><p><b>CONCLUSIONS</b>The agger nasi cell approach to the frontal recess gives an access and allows identification of the frontal ostium. In addition, it provides direct visualization with a 0 degree endoscope into the frontal recess.</p>
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Chronic Disease , Endoscopy , Methods , Frontal Sinus , General Surgery , Nasal Cavity , Nose , General Surgery , Paranasal Sinuses , Sinusitis , General SurgeryABSTRACT
<p><b>AIM</b>To compare two methods, the total radioactivity assay (RA method) and the radioactivity assay after separation with high performance liquid chromatography (HPLC-RA method).</p><p><b>METHODS</b>125I-Lidamycin was prepared by Iodogen method and separated by size exclusive high performance liquid chromatography. The pharmacokinetic parameters of lidamycin were assayed by two methods after intravenous injection to mice at the dose of 100 microg x kg(-1), and compared by statistical analysis.</p><p><b>RESULTS</b>The pharmacokinetic parameters (Vd, T1/2alpha, T1/2beta, K21, K10, K12, AUC and CL) showed significant difference between the two methods (P < 0.05).</p><p><b>CONCLUSION</b>The HPLC-RA method was better than the RA method to determine unchanged 125I-lidamycin.</p>