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  • Author: Vancea Szende x
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Abstract

Objective: The purpose of this study was to develop a LC-MS method to determine amiodarone (AMI) and its major metabolite desethylamiodarone (DEA) from rat plasma released from the adipose tissue of AMI treated rats subjected to a weight gain/weight loss cycle. Methods: Separation of the compounds was performed on a Kinetex 2.6 μm C18 100 x 4.6 mm column under isocratic conditions using a mixture of acetonitrile: 0.1% formic acid 65:35 at a flow rate of 0.5 ml/min. Detection of the analyte was performed by electrospray positive ionization, the monitored ions being 135 m/z from 646 for AMI and 135 m/z of 618 for DEA. Analytes were extracted after plasma protein precipitation with methanol. Results: The developed method presented specificity and linearity on the concentration range of 25-2500 ng/ml plasma for AMI and 2.5-1250 ng/ml plasma for DEA and the precision and accuracy of the method at all of quality control concentration levels including LLOQ were according to official guidelines for validating analytical methods. Conclusions: A sensitive and accurate LC-MS method has been developed with a much lower LLOQ than literature data to detect the plasma concentration differences of the studied analytes that result from forced lipolysis and mobilization from the adipose tissue.

Abstract

An uncomplicated, sensitive liquid chromatography linked to mass spectrometry (LC/MS) for evaluation of carbamazepine and carbamazepine-10,11-epoxide (its metabolite) in human plasma, human saliva, rat plasma, and rabbit plasma was developed. Analyses were conducted on a Zorbax SB-C18, 100 mm × 3 mm ID, 3.5 μm column, at a column temperature of 40 ºC. The mobile phase was comprised of 0.1% formic acid in water and methanol in a 35 : 65 (v/v) ratio, with a flow rate of 0.4 mL/min. Lacosamide was utilized as internal standard. Under these chromatographic conditions, the retention times of lacosamide, carbamazepine-10,11-epoxide, and carbamazepine were 1.4 min, 1.6 min, and 2.2 min, respectively. The quantification of the analytes was performed using multiple reaction monitoring, with the use of a triple quadrupole mass spectrometer with electrospray positive ionization. The monitored ions were m/z 194 derived from m/z 237 for carbamazepine, m/z 180 derived from m/z 253 for carbamazepine-10,11-epoxide, and m/z 108 derived from m/z 251 for lacosamide. The samples were prepared by protein precipitation from 0.2 mL of plasma/saliva using 0.6 mL of internal standard solution in methanol. Calibration curves were constructed over the ranges 1.1–17.6 µg/mL and 0.23–5.47 µg/mL for carbamazepine and carbamazepine-epoxide, respectively. The coefficients of determination obtained by using a weighted (1/x) linear regression were greater than 0.994. The reported LC-MS/MS method was applied to preclinical pharmacokinetic studies and therapeutic drug monitoring.

Abstract

Objective: The aim of the study was a comparative investigation by spectral and thermal analysis in order to asses a number of characteristics of different varieties ofrawmaterials of ursodeoxycholic acid and ibuprofen. The different dissolution behavior of two ursodeoxycholic acid pharmaceutical product by crystallinity pattern was investigated. Methods: Raw materials of ursodeoxycholic acid and ibuprofen were used. IR spectroscopy, differential scanning calorimetry and X-Ray Diffraction Analysis were applied. Results: The results show no crystallinitydifferences for different batches of the tested drugs. No solid solid transition was proved during sample preparation for transmission IR analysis. Conclusions: A combination of two more affordabletests by IR spectrometry and differential scanning calorimetry lead to the same results as X-Ray diffraction analysis for crystallinity similarity assessment of the studied substances. The dissolution differences of test drugs were not related to the polymorphism of the raw materials.

Abstract

Corticosterone is an adrenocortical steroid hormone with glucocorticoid and mineralocorticoid effects. Based on previous studies, the plasma level of corticosterone correlates with the stress exposure of rodents. Because the half-life of corticosterone in blood is short, its plasma concentration can be used as an acute stress marker. But hair is accumulating the systemic and locally produced corticosterone, therefore it can be used to study chronic stress. However, the accurate quantification of corticosterone is an analytical challenge owing to the very low amount of hormone found in a complicated biological matrix. The high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) can provide the required selectivity and sensitivity for this purpose. Currently published methods for corticosterone quantification involve complicated sample preparation and long run time. Accordingly, the aims of the study were to simplify the extraction method of the corticosterone from rat hair samples and to develop an optimized HPLC-MS method for the accurate quantification. The rat hair samples were washed with methanol, dried and cut, then extracted with methanol at room temperature for 24 hours. The lipids were precipitated with formic acid aqueous solution and eliminated by centrifugation. The corticosterone was separated from other compounds with reverse phase chromatography using acetonitrile and 0,1% aqueous solution of formic acid as mobile phase. The detection was performed in positive SIM mode measuring the 347 m/z molecular ion. A six point calibration was performed in the range of 0,5-20 ng/ml, the accuracy was tested with quality control samples at two different concentration level. The total run time is only 4,2 minutes and the lower limit of quantification (LLOQ) is 0,5 ng/ml, with 10 pg absolute sensitivity. By determining the quantity of the hormone for a well-defined hair region, based on the speed of hair growth, we can characterize the retrospective stress exposure of the animals in different conditions.

Abstract

Objective: Silver complexes of antibacterial quinolones have the potential advantage of combining the antibacterial activity of silver and fluoroquinolones. The objective of our study was the preparation and the preliminary physico-chemical characterization of a silver complex with ofloxacin.

Methods: To achieve our goals several spectroscopic methods (ultraviolet spectrophotometry, mass spectrometry, and Fourier transform infrared spectroscopy) and thermal methods (differential scanning calorimetry and thermogravimetric analysis) were used in order to elucidate the chemical structure of the complex.

Results: Using mass spectrometry we established the stoichiometric ratio silver:ofloxacin as 1:2. Experimental data suggest a particular coordination for ofloxacin, as a monodentate ligand, in the formation of a complex with silver, through the nitrogen atom from the methyl-piperazine cycle.

Conclusions: The obtained complex has a chemical structure likely [Ag(Ofloxacin)2]NO3, requiring evaluation through other physico-chemical methods.