Graphene Oxide/Polyethylene Glycol-Stick for Thin Film Microextraction of ß-Blockers from Human Oral Fluid by Liquid Chromatography-Tandem Mass Spectrometry.

A wooden stick coated with a novel graphene-based nanocomposite (Graphene oxide/polyethylene glycol (GO/PEG)) is introduced and investigated for its efficacy in solid phase microextraction techniques. The GO/PEG-stick was prepared and subsequently applied for the extraction of ß-blockers, acebutolol, and metoprolol in human oral fluid samples, which were subsequently detected by liquid chromatography tandem mass spectrometry (LC-MS/MS). Experimental parameters affecting the extraction protocol including sample pH, extraction time, desorption time, appropriate desorption solvent, and salt addition were optimized. Method validation for the detection from oral fluid samples was performed following FDA (Food and Drug Administration) guidelines on bioanalytical method validation. Calibration curves ranging from 5.0 to 2000 nmol L-1 for acebutolol and 25.0 to 2000 nmol L-1 for metoprolol were used. The values for the coefficient of determination (R2) were found to be 0.998 and 0.996 (n = 3) for acebutolol and metoprolol, respectively. The recovery of analytes during extraction was 80.0% for acebutolol and 62.0% for metoprolol, respectively. The limit of detections (LODs) were 1.25, 8.00 nmol L-1 for acebutolol and metoprolol and the lower limit of quantifications (LLOQ) were 5.00 nmol L-1 for acebutolol and 25.0 nmol L-1 for metoprolol. Validation experiments conducted with quality control (QC) samples demonstrated method accuracy between 80.0% to 97.0% for acebutolol and from 95.0% to 109.0% for metoprolol. The inter-day precision for QC samples ranged from 3.6% to 12.9% for acebutolol and 9.5% to 11.3% for metoprolol. Additionally, the GO/PEG-stick was demonstrated to be reusable, with the same stick observed to be viable for more than 10 extractions from oral fluid samples.

Combination of capillary electrophoresis and molecular modeling to study the enantiomer affinity pattern between ß-blockers and anionic cyclodextrin derivatives in a methanolic and water background electrolyte.

In order to have deep insights into the mechanisms of enantiomer affinity pattern in both aqueous and non-aqueous systems, an approach combining capillary electrophoresis and molecular modeling was undertaken. A chiral ß-blocker; acebutolol, was enantioseparated in aqueous capillary electrophoresis and non-aqueous capillary electrophoresis using two anionic ß-cyclodextrin derivatives. The enantiomer affinity pattern of acebutolol was found to be opposite when an aqueous background electrolyte was replaced with non-aqueous background electrolyte in the presence of heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin but remained the same in the presence of heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin. Molecular docking of acebutolol into two ß-cyclodextrin derivatives indicated two distinct binding modes called 'up' and 'down' conformations. After structure optimization by molecular dynamics and energy minimization, both enantiomers of acebutolol were preferred to the 'up' conformation with heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin while 'down' conformation with heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin. The further calculation of the complex energy with solvent effect indicated that heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin had higher affinity to S-acebutolol than R-acebutolol in non-aqueous capillary electrophoresis while it showed better binding to R-acebutolol in aqueous capillary electrophoresis. However, the heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin bound better to R-acebutolol in both aqueous and non-aqueous capillary electrophoresis, implying that the binding mode played more important role in chiral separation of heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin while the solvent effect had prevailing impact on heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin.

Graphite-based microextraction by packed sorbent for online extraction of ß-blockers from human plasma samples.

In the present work a new graphitic material (Carbon-XCOS) was used as a sorbent for microextraction by packed sorbent (MEPS). The ß-blockers metoprolol and acebutolol in plasma samples were extracted and detected online using Carbon-MEPS syringe and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Factors affecting the MEPS performance such as conditioning, washing and elution solutions were investigated. The validation of the bioanalytical method was performed using human plasma. The standard curve ranged from 10 to 2000nM and the lower limit of quantification (LLOQ) was set to 10nM. The method validation showed good accuracy and precision for the quality control (QC) samples at three concentration levels (30, 800 and 1600nM). The accuracy values of the QC samples were in the range of 86-108% (n=18). The precision values of intra- and inter-day for QC samples ranged from 4.4% to 14.4% (RSD) for the both studied analytes. The coefficient of determination (R(2)) values were ≥0.999 (n=3).

Potential for biodegradation and sorption of acetaminophen, caffeine, propranolol and acebutolol in lab-scale aqueous environments.

Sorption and combined sorption-biodegradation experiments were conducted in laboratory batch studies with 100 g soil/sediments and 500 mL water to investigate the fates in aqueous environments of acetaminophen, caffeine, propranolol, and acebutolol, four frequently used and often-detected pharmaceuticals. All four compounds have demonstrated significant potential for degradation and sorption in natural aqueous systems. For acetaminophen, biodegradation was found to be a primary mechanism for degradation, with a half-life (t(1/2)) for combined sorption-biodegradation of 2.1 days; in contrast, sorption alone was responsible only for a 30% loss of aqueous-phase acetaminophen after 15 days. For caffeine, both biodegradation and sorption were important (t(1/2) for combined sorption-biodegradation was 1.5 days). However, for propranolol and acebutolol, sorption was found to be the most significant removal mechanism and was not affected by biodegradation. Desorption experiments revealed that the sorption process was mostly irreversible. High values were found for K(d) for caffeine, propranolol, and acebutolol, ranging from 250 to 1900 L kg(-1), which explained their greater tendency for sorption onto sediments, compared to the more hydrophilic acetaminophen. Experimentally derived values for logK(oc) differed markedly from values calculated from correlation equations. This discrepancy was attributed to the fact that these equations are well suited for hydrophobic interactions but may fail to predict the sorption of polar and ionic compounds. These results suggest that mechanisms other than hydrophobic interactions played an important role in the sorption process.

Streptococcus pneumoniae PstS production is phosphate responsive and enhanced during growth in the murine peritoneal cavity.

Differential display-PCR (DDPCR) was used to identify a Streptococcus pneumoniae gene with enhanced transcription during growth in the murine peritoneal cavity. Northern dot blot analysis and comparative densitometry confirmed a 1.8-fold increase in expression of the encoded sequence following murine peritoneal culture (MPC) versus laboratory culture or control culture (CC). Sequencing and basic local alignment search tool analysis identified the DDPCR fragment as pstS, the phosphate-binding protein of a high-affinity phosphate uptake system. PCR amplification of the complete pstS gene followed by restriction analysis and sequencing suggests a high level of conservation between strains and serotypes. Quantitative immunodot blotting using antiserum to recombinant PstS (rPstS) demonstrated an approximately twofold increase in PstS production during MPC from that during CCs, a finding consistent with the low levels of phosphate observed in the peritoneum. Moreover, immunodot blot and Northern analysis demonstrated phosphate-dependent production of PstS in six of seven strains examined. These results identify pstS expression as responsive to the MPC environment and extracellular phosphate concentrations. Presently, it remains unclear if phosphate concentrations in vivo contribute to the regulation of pstS. Finally, polyclonal antiserum to rPstS did not inhibit growth of the pneumococcus in vitro, suggesting that antibodies do not block phosphate uptake; moreover, vaccination of mice with rPstS did not protect against intraperitoneal challenge as assessed by the 50% lethal dose.

Analysis of nifedipine-acebutolol hydrochloride binary combination in tablets using UV-derivative spectroscopy, capillary gas chromatography and high performance liquid chromatography.

Three methods are described for the simultaneous determination of nifedipine and acebutolol hydrochloride in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with peak-to-base and zero-crossing measurements methods. The first derivative amplitudes at 400 and 352 nm were selected for the assay of nifedipine and acebutolol hydrochloride, respectively. Calibration graphs follow Beer's law in the range of 4-12 and 44-132 micrograms ml-1 and the linearity was satisfactory (r = 0.999) for nifedipine and acebutolol hydrochloride, respectively. The second method was based on the separation of nifedipine from acebutolol hydrochloride, with an internal standard thymolphthalein, using capillary gas-liquid chromatography with a programmable temperature change. The third method was based on high performance liquid chromatographic separation of the two drugs on a reversed-phase, C18, column using a mobile phase of methanol-water (55:45, pH 4.5) with a programmable flow rate of 1 ml min-1 for 4 min which changed to 2 ml min-1 for the rest of the run. The detection was done at 260 nm using oxprenolol hydrochloride as an internal standard. Both chromatographic methods showed good linearity, precision and reproducibility. No spectral or chromatographic interference from the tablet excipients were found. The proposed methods were successfully applied to the assay of commercial tablets and a content uniformity test. The procedures were rapid, simple nondestructive and suitable for quality control application.

[Determining acebutolol level in the blood serum]. / Oznaczanie acebutalolu w surowicy krwi.

A simple method for isolation of acebutolol from blood serum, and conditions of thin-layer chromatography for detection of this drug in blood are reported. An own colorimetric method has been developed for the determination of acebutolol after its isolation and hydrolysis in the medium of sulphuric acid. Results of the determinations were subjected to statistical analysis. The methods were elaborated using model samples prepared by addition of the acebutolol working standard to blood serum. Sensitivity of the acebutolol detection by thin-layer chromatography under elaborated conditions proved to reach the level of 0.5 microgram.