Screening of beta-blockers in human serum by ion-pair chromatography and their identification as methyl or acetyl derivatives by gas chromatography-mass spectrometry

Rapid Characterization of Undeclared Pharmaceuticals in Herbal Preparations by Ambient Ionization Mass Spectrometry for Emergency Care

In Asia, some herbal preparations have been found to be adulterated with undeclared synthetic medicines to increase their therapeutic efficiency. Many of these adulterants were found to be toxic when overdosed and have been documented to bring about severe, even life-threatening acute poisoning events. The objective of this study is to develop a rapid and sensitive ambient ionization mass spectrometric platform to characterize the undeclared toxic adulterated ingredients in herbal preparations. Several common adulterants were spiked into different herbal preparations and human sera to simulate the clinical conditions of acute poisoning. They were then sampled with a metallic probe and analyzed by the thermal desorption-electrospray ionization mass spectrometry. The experimental parameters including sensitivity, specificity, accuracy, and turnaround time were prudently optimized in this study. Since tedious and time-consuming pretreatment of the sample is unnecessary, the toxic adulterants could be characterized within 60 s. The results can help emergency physicians to make clinical judgments and prescribe appropriate antidotes or supportive treatment in a time-sensitive manner.

Thermal desorption ambient ionization mass spectrometry for emergency toxicology

In the emergency department, it is important to rapidly identify the toxic substances that have led to acute poisoning because different toxicants or toxins cause poisoning through different mechanisms, requiring disparate therapeutic strategies and precautions against contraindicating actions, and diverse directions of clinical course monitoring and prediction of prognosis. Ambient ionization mass spectrometry, a state-of-the-art technology, has been proved to be a fast, accurate, and user-friendly tool for rapidly identifying toxicants like residual pesticides on fruits and vegetables. In view of this, developing an analytical platform that explores the application of such a cutting-edge technology in a novel direction has been initiated a research program, namely, the rapid identification of toxic substances which might have caused acute poisoning in patients who visit the emergency department and requires an accurate diagnosis for correct clinical decision-making to bring about corresponding data-guided management. This review includes (i) a narrative account of the breakthrough in emergency toxicology brought about by the advent of ambient ionization mass spectrometry and (ii) a thorough discussion about the clinical implications and technical limitations of such a promising innovation for promoting toxicological tests from tier two-level to tier one level.

Rapid point-of-care identification of oral medications in gastric lavage content by ambient mass spectrometry in the emergency room

RATIONALE

Acute poisoning should be handled with high efficiency in order to minimize morbidity and mortality in the emergency room. Unfortunately, history-taking and physical examination are not always reliable. Mis-swallowing of oral medications is common in the pediatric group. This study aimed at developing a rapid point-of-care ambient mass spectrometric method for the early identification of ingested oral medications in gastric lavage content.

METHODS

Four different types of oral medications that are most commonly mis-swallowed by children were diluted to different concentrations. Each of these chemical solutions was mixed with human gastric lavage content. A direct metallic sampling probe was dipped into the solution. It was then inserted promptly into the thermal desorption electrospray ionization source to carry out ionization and subsequent mass spectrometric analysis of the medications. The corresponding compounds were identified through matching of the obtained mass spectrometric data with those provided by well-established databases.

RESULTS

Since no pretreatment of the specimen was required, the sampling step, and the subsequent thermal desorption electrospray ionization and mass spectrometric detection of the medications were completed within 30 s. Mass spectra were obtained for four different kinds of oral medication. The limit-of-detection of the four tested oral medications in gastric lavage content is at sub-ppm level, which is sensitive enough for emergency medicine applications since the quantities of medications ingested by pediatric patients are usually much higher.

CONCLUSIONS

Thermal desorption electrospray ionization mass spectrometry, with informational support provided by an online mass spectral database, allows for early point-of-care identification of mis-swallowed oral medications in the evacuated gastric lavage contents obtained from gastric lavage of patients in the emergency room, and it is promising in providing important toxicological information to ensure the appropriateness of the subsequent medical management. Copyright © 2016 John Wiley & Sons, Ltd.

Polymeric matrix membrane sensors for sensitive potentiometric determination of some beta-blockers in pharmaceutical preparations

Five poly(vinyl chloride) matrix membrane sensors responsive to some beta-blockers (atenolol, bisoprolol, metoprolol, propranolol and timolol) are described and characterized. The sensors are based on the use of the ion-association complexes of the beta-blocker cations with tungstophosphate anion as electroactive materials. The performance characteristics of these sensors, evaluated according to IUPAC recommendations, reveal fast, stable and near-Nernstian response for 10(-2)-2 x 10(-7) mol l(-1) of different beta-blockers over the pH range 2-9. Many inorganic and organic cations as well as drug excipients and diluents normally used in drug formulations do not interfere. The sensors are used for direct potentiometry of beta-blockers in some pharmaceutical preparations. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of these drugs. Results with an average recovery of 99.1% and a mean standard deviation of +/- 1.3% of the nominal are obtained which compare fairly well with data obtained using the British Pharmacopoeia method.

Simple determination of propranolol in pharmaceutical preparations by heavy atom induced room temperature phosphorescence

The applicability of heavy atom induced room temperature phosphorescence in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulphite as oxygen scavenger, were used to obtain phosphorescent signal of propranolol in solution. Thus a new simple, rapid and selective phosphorimetric method is proposed for propranolol determination in pharmaceutical preparations. The phosphorescence intensity was measured at 492 nm exciting at 294 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 0 and 500 ng ml(-1) with a detection limit of 14.4 ng ml(-1), an analytical sensitivity of 6.7 ng ml(-1) and a standard deviation of 1.4% at a 300 ng ml(-1) concentration level. The method has been successfully applied to the analysis of propranolol in an antidepressive pharmaceutical preparation and it was validated using standard addition methodology.

Reversed-phase high-performance liquid chromatography for evaluating the distribution of pharmaceutical substances in suppository base-phosphate buffer system

The aim of this study was to assess the potency of the reversed-phase high-performance liquid chromatography (RP-HPLC) for in vitro evaluation of the distribution behavior of common drugs between one of the generally used suppository bases Witepsol H15 and the rectal liquid which is imitated by a phosphate buffer, pH 7.2. The distribution coefficients (log K) of nine compounds--paracetamol, caffeine, diclofenac, propyphenazone, indomethacin, codeine base, codeine phosphate, phenobarbital acid and phenobarbital sodium salt were determined by the classical shake-flask' method followed by RP-HPLC quantitative assay. The capacity factors log k' of the compounds were determined on reversed-phase C18 column at a number of methanol-5 mM phosphate buffer, pH 7.2 mobile phases containing different percentages of methanol (phiMeOH). The apparent capacity factors log k(w)app were derived by extrapolation of the methanol concentration to zero and using the correction for ionization, the real capacity factors log k'(w) were calculated. The lipophilicity of the compounds was assessed by the partition coefficients CLOGP and the distribution coefficients CLOGD7.2, calculated for the n-octanol-water system. Correlations between log k'(w) and CLOGP, log k(w)app and CLOGD7.2, log k(w)app and log K were found. The last correlation indicated that the parameter log k(w)app was suitable for evaluating the distribution behavior of the studied drugs in the examined Witepsol H15-rectal liquid system. The predictive power of this correlation was tested by a set of nine non-congeners. It was shown that the classical 'shake-flask' method for determination of the distribution behavior of the studied drugs between the suppository base Witepsol H15 and the phosphate buffer, pH 7.2 might be replaced by the RP-HPLC technique due to its priorities of rapid, stable and reproducible experiments.

Automated in-tube solid-phase microextraction coupled with liquid chromatography/electrospray ionization mass spectrometry for the determination of beta-blockers and metabolites in urine and serum samples

The technique of automated in-tube solid-phase microextraction (SPME) coupled with liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) was evaluated for the determination of beta-blockers in urine and serum samples. In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. LC/MS analyses of beta-blockers were initially performed by liquid injection onto a LC column. Nine beta-blockers tested in this study gave very simple ESI mass spectra, and strong signals corresponding to [M + H]+ were observed for all beta-blockers. The beta-blockers were separated with a Hypersil BDS C18 column using acetonitrile/methanol/water/acetic acid (15:15:70:1) as a mobile phase. To optimize the extraction of beta-blockers, several in-tube SPME parameters were examined. The optimum extraction conditions were 15 draw/eject cycles of 30 microL of sample in 100 mM Tris-HCl (pH 8.5) at a flow rate of 100 microL/min using an Omegawax 250 capillary (Supelco, Bellefonte, PA). The beta-blockers extracted by the capillary were easily desorbed by mobile-phase flow, and carryover of beta-blockers was not observed. Using in-tube SPME/LC/ESI-MS with selected ion monitoring, the calibration curves of beta-blockers were linear in the range from 2 to 100 ng/mL with correlation coefficients above 0.9982 (n = 18) and detection limits (S/N = 3) of 0.1-1.2 ng/mL. This method was successfully applied to the analysis of biological samples without interference peaks. The recoveries of beta-blockers spiked into human urine and serum samples were above 84 and 71%, respectively. A serum sample from a patient administrated propranolol was analyzed using this method and both propranolol and its metabolites were detected.

Micellar liquid chromatography: a worthy technique for the determination of beta-antagonists in urine samples

Several beta-antagonists (acebutolol, atenolol, celiprolol, labetalol, metoprolol, nadolol, propranolol) were determined in urine samples with fluorometric detection after direct injection, in less than 15 min, with a micellar mobile phase of 0.1 M sodium dodecyl sulfate (SDS), 15% propanol, and 1% triethylamine at pH 3. The limits of detection (38 criterion) were usually between 3 and 30 ng/mL. The addition of propanol and triethylamine and the reduction of the pH of the mobile phase improved the efficiency of the chromatographic peaks that was rather low in pure micellar eluents. The selection of the composition of the mobile phase was easily performed through the use of an interpretive procedure which considered the retention times and peak shapes of the beta-antagonists in six chromatograms, obtained at varying concentrations of SDS (0.05-0.15 M) and propanol (5-15% v/v). The chromatograms of urine samples from healthy volunteers, which were administered atenolol, metoprolol, and propranolol, showed only one peak for the former drug and several peaks for the other two. These peaks corresponded to the parent drug and metabolites, which indicated the partial and the extensive degradation of metoprolol and propranolol, respectively.

A sensitive assay of metoprolol and its major metabolite alpha-hydroxy metoprolol in human plasma and determination of dextromethorphan and its metabolite dextrorphan in urine with high performance liquid chromatography and fluorometric detection

A reverse-phase High Performance Liquid Chromatographic (HPLC) method was developed for the analysis of metoprolol in the large number of human plasma samples obtained in in vitro-in vivo correlations (IVIVC) and bioavailability studies of extended release formulations of metoprolol tartrate. The metabolite, alpha-hydroxy metoprolol (OH-met), could also be quantified. The analytes were extracted from the plasma using solid phase columns, separated on a C-4 analytical column followed by fluorimetric detection. The linearity, precision, accuracy, stability, selectivity and ruggedness were validated for the concentration ranges of 1-400 ng ml-1 for metoprolol and 0.5-200 ng ml-1 for OH-met. The same chromatographic conditions were slightly modified to quantify dextromethorphan and its metabolite dextrorphan in urine in the concentration range 0.052-0.05 microgram ml-1 as a method for screening for fast metabolizers.

Disposition of human drug preparations in the horse. V. Orally administered oxprenolol

Urinary concentrations of the beta-antagonist oxprenolol and some of its major human metabolites were determined following oral administration of a dose of 160 mg to five fasted horses. Quantitation was performed by gas chromatography-mass spectrometry (GC-MS) in the selected ion mode (SIM) by monitoring ion m/z 466 of the heptafluorobutyric derivatives. As early as 2 h after dosage oxprenolol could be detected in hydrolysed urine and remained detectable up to 24 h. Maximum urinary concentrations and excretion rates were obtained between 2 and 12 h. After 12 h only 2.8% of the administered dose was excreted as conjugates of oxprenolol and major human metabolites including 4-OH-oxprenolol and 5-OH-oxprenolol. These metabolites were detectable up to 48 h.

Determination of some cardiovascular drugs in serum and urine by capillary isotachophoresis

The separation and determination of amiloride, metoprolol, deacetylmetipranolol, labetalol and furosemide in human serum and urine by capillary isotachophoresis were investigated. Amiloride and beta-blockers were separated by cationic isotachophoresis in the electrolyte system sodium morpholinoethanesulfonate buffer (pH 5.5) (cL = 10 mM)-glutamic acid. Furosemide was separated using the anionic electrolyte system histidine hydrochloride buffer (pH 6.2) (cL = 10 mM)-morpholinopropanesulfonic acid. Endogenous and the possible exogenous compounds were almost totally removed from serum and urine by solid-phase extraction using a Separon SGX C18 cartridge. The recovery of compounds varied from 98.2 to 103.2%. The linearity range for the compounds was 50-1000 ng/ml. The relative standard deviations varied from 0.1 to 5.6%. The overall limits of determination ranged from 32 to 46 ng/ml of urine and from 39 to 46 ng/ml of serum, depending of the type of drugs.

Detection of beta-blockers in urine by solid-phase extraction-supercritical fluid extraction and gas chromatography-mass spectrometry

The most convenient way to perform supercritical fluid extraction (SFE) of liquid sample matrices is to combine it with solid-phase extraction (SPE). beta-Blockers from urine were collected on an Empore disc, which was then placed into an extraction cell for derivatization and SFE. SPE recovery was best at pH 10. Effects of temperature, pressure and volume of pyridine on the acetylation and SFE processes were studied. Without acetylation the beta-blockers were not significantly soluble in CO2. SFE temperatures of 70 degree C and 150 degree C together with 200 microliters of acetic anhydride and 400 microliters pyridine gave the best results. With the SPE-SFE-GC-MS method developed here, beta-blockers like oxprenolol, metoprolol and propranolol could easily be detected in urine samples, and the limit of detection (LOD) for these compounds was found to be 20 ng/ml, 30 ng/ml and 40 ng/ml, respectively.

High-performance liquid chromatography with amperometric detection applied to the screening of beta-blockers in human urine

A high-performance liquid chromatographic method with electrochemical detection has been developed for the determination of six beta-blockers: atenolol, nadolol, timolol, metoprolol, oxprenolol, and alprenolol. The chromatographic separation was performed using a mu Bondapack C18 column, a mobile phase of acetonitrile-water (40:60), containing 5 mM KH2PO4/K2HPO4 proved to be optimal at a 1.3 ml/min flow-rate, and a pH of 6.5. The temperature was optimized at 30 +/- 0.2 degrees C. The amperometric detector, equipped with a glassy carbon electrode, was operated at 1300 mV versus Ag/AgCl in the direct current mode. The method was applied to the determination of these compounds at two concentration levels: ppm and ppb (ng/ml), obtaining relative standard deviations lower than 5% at ppm levels and lower than 10% at ppb levels, and quantitation limits ranging from 15 ppb to 500 ppb. The method was applied to the screening of beta-blockers in spiked urine samples, with a total elution time lower than 12 min, obtaining the best recoveries for timolol and metoprolol (never greater than 93%). These recoveries together with the low limits of quantitation achieved, allows its application to doping analysis in human urine.

Ion-pair chromatography and micellar electrokinetic capillary chromatography in analyzing beta-adrenergic blocking agents from human biological fluids

Ion-pair chromatography (IPC) and micellar electrokinetic capillary chromatography (MECC) were used for the separation and determination of parent beta-blockers from human biological fluids. In both these techniques, N-cetyl-N,N,N-trimethylammonium bromide (CTAB) was used as a buffer additive. In IPC, CTAB was an ion-pair former, and in MECC it was a micelle-forming surfactant. The effectiveness of the IPC method using methanol-gradient elution and that of MECC were compared for drug-spiked serum and urine samples. Detection was performed with a diode-array detector in the IPC method and with a 214-nm filter in the MECC technique. In both methods a phosphate buffer (pH 7.0) was used. In MECC the buffer solution contained 10 mM CTAB, while in IPC the CTAB concentration was decreased from 7 to 4 mM during the separation when a methanol gradient was used. The study showed that the IPC technique performed better for bioanalyses than the high-performance MECC technique, since in MECC UV detection presented a problem because of the low sample concentration. However, in MECC sample preparation was less time-consuming, using hydrolyzation and protein precipitation and, unlike the IPC technique, it did not require any liquid-liquid extraction step.

Screening and determination of beta-blockers, narcotic analgesics and stimulants in urine by high-performance liquid chromatography with column switching

A fast method is described for the screening of eleven beta-blockers, two narcotic analgesics and two stimulants in urine by HPLC with column switching. The urine sample (100 microliters), buffered to pH 9-9.5, is injected onto a short extraction column packed with CN stationary phase. The extraction column is flushed with water for 2.5 min to elute polar matrix components to waste. The retained components are then backflushed by means of a six-port valve onto the ODS analytical column where they are separated. Phosphate buffer pH 3.0 and acetonitrile were used as mobile phase. Gradient elution was applied in the screening method to improve separation. Detection was performed with a diode-array detector at 220, 235 and 300 nm. Recoveries were near 100%, precision was excellent and sensitivity about 0.25 micrograms/l. To speed up the quantitative analysis, the same method but with isocratic elution was successfully applied to the determination of acebutolol and metoprolol in urine samples collected 4 h after administration of the compounds as single doses.

Determination of nine beta-blockers in serum by micellar electrokinetic capillary chromatography

beta-Adrenergic blocking agents are used for the treatment of angina pectoris, cardiac arrhythmia, hypertension, anxiety attacks, thyrotoxicosis, migraine and glaucoma. Owing to their sedative effect, they are also used as doping agents in sport. All beta-blockers have an alkanol amine side chain terminating in a secondary amino group in their structure. The pKa values vary from 9.2 to 9.8. Because some beta-blockers are hydrophilic and some lipophilic, simultaneous determination is difficult. In this work, a method based on micellar electrokinetic capillary chromatography (MECC) was developed for the separation and determination of beta-blockers in serum. The phosphate buffer 0.08 M (pH 6.7) solution contained 15 mM N-cetyl-N,N,N-trimethylammonium bromide. Nine parent beta-blockers could be separated in a single run and the concentrations determined by internal standard (ephedrine) method. The simple clean-up procedure consisted of enzyme hydrolysis (Helix pomatia), protein precipitation, and filtration through 0.5-microns PTFE membranes. The MECC method exhibited good repeatability and a linear range of 75-300 micrograms/ml. The method was successfully applied after concentration to the determination of propranolol in real samples.

Receptor binding assays in analysing the bioavailability and pharmacodynamic bioequivalence of active drug moieties. A study of metoprolol

The bioavailability and pharmacodynamic bioequivalence of a conventional and an experimental sustained-release formulation of 100 mg metoprolol tartrate were studied in a randomised cross-over study in seven healthy volunteers by assessing over 24 h the plasma kinetics of R,S-metoprolol, its beta 1-adrenoceptor binding component, and by determining the extent to which the active drug moiety in plasma occupied rabbit lung beta 1- and rat reticulocyte beta 2-adrenoceptors. The formulations differed markedly in their kinetic characteristics: the peak plasma concentration (Cmax) of R,S-metoprolol after administration of the conventional formulation was 140 ng.ml-1, (n = 7) and it was approximately one-third of that after the sustained-release formulation, 49 ng.ml-1, (n = 6); the AUC0-24 h-values for the formulations were 700 and 310 ng.h.ml-1, respectively. The Cmax for the beta 1-adrenoceptor binding component of metoprolol was 180 ng.ml-1 (n = 7) after administration of the conventional, and 74 ng.ml-1 after administration of the sustained-release formulation. The corresponding AUC0-24 h-values for the receptor binding component were 920 and 470 ng.h.ml-1 (n = 7). Thus, the kinetic differences between R,S-metoprolol and the beta 1-receptor binding component were considerable and they were affected by the type of formulation. In general, after administration of the sustained-release formulation, the percentage beta 1- and beta 2-adrenoceptor occupancy of metoprolol in plasma was 5-15% less than after administration of the conventional formulation.(ABSTRACT TRUNCATED AT 250 WORDS)