Methods of identification and confirmation of abusive drugs in human urine

A thin-layer chromatography (TLC) procedure is described to be used as the initial drug detection method for urine surveillance in a drug abuse treatment program. While the TLC method is sufficiently sensitive, it is prone to false-positive results. For this reason, two other drug detection methods (gas—liquid chromatography and radioimmunoassay) have been incorporated to confirm positive results obtained with TLC. The combined methodologies result in a urine surveillance procedure that is versatile, sensitive and highly reliable.     

Stability‐indicating chromatographic methods for determination of flecainide acetate in the presence of its degradation products; isolation and identification of two of its impurities

In this work, two stability‐indicating chromatographic methods have been developed and validated for determination of flecainide acetate (an antiarrhythmic drug) in the presence of its degradation products (flecainide impurities; B and D). Flecainide acetate was subjected to a stress stability study including acid, alkali, oxidative, photolytic and thermal degradation. The suggested chromatographic methods included the use of thin layer chromatography (TLC‐densitometry) and high‐performance liquid chromatography (HPLC). The TLC method employed aluminum TLC plates precoated with silica gel G.F₂₅₄ as the stationary phase and methanol–ethyl acetate–33% ammonia (3:7:0.3, by volume) as the mobile phase. The chromatograms were scanned at 290 nm and visualized in daylight by the aid of iodine vapor. The developed HPLC method used a RP‐C₁₈ column with isocratic elution. Separation was achieved using a mobile phase composed of phosphate buffer pH 3.3–acetonitrile–triethylamine (53:47:0.03, by volume) at a flow rate of 1.0 mL/min and UV detection at 292 nm. Factors affecting the efficiency of HPLC method have been studied carefully to reach the optimum conditions for separation. The developed methods were validated according to the International Conference on Harmonization guidelines and were applied for bulk powder and dosage form. Copyright © 2016 John Wiley & Sons, Ltd.     

Utilization of a scientifically operated charge-coupled device detector for high-performance thin-layer chromatographic analysis of tetracyclines

A high-performance thin-layer chromatography (HPTLC) method using a scientifically operated charge-coupled device detector is described for the assay of tetracycline pharmaceutical products. Quantitative information can be obtained for all samples on a TLC plate within a few seconds. The separation efficiency and detection limits were determined on both normal phase and reverse phase TLC plates. Fluorescence detection mode offers higher sensitivity than fluorescence quenching mode. The dynamic range, sensitivity, accuracy and precision of the system were evaluated. Detection limits of the impurities are in the range of 0.1 to 0.5 ng or 0.3 to 1% of tetracycline, depending on the compound, with a recovery percentage over 85%. The existing impurities in tetracycline capsules were determined using both HPLC and HPTLC techniques. All of the impurities were below the regulation level.     

Separation,Characterization, and Quantification of Atorvastatin and Related Impurities by Liquid Chromatography-Electrospray Ionization Mass Spectrometry

A method coupling high-performance liquid chromatography with diode-array detector and electrospray ionization mass spectrometry (HPLC-DAD-ESI/MSⁿ) has been developed for the separation and characterization of atorvastatin and its related impurities. The results obtained using positive ion mode showed some diagnostic fragments that are useful for the identification of atorvastatin related impurities in real samples. Quantitative analysis of drug impurities was performed in the multiple reaction monitoring mode. Quantification limits for impurities were in the ranges 21.5–70.8 ng mL^?1. The method was successfully applied to the drug purity evaluation and quantitative determination of atorvastatin related impurities in bulk drugs and pharmaceutical formulations.     

Quantitative Analysis of a Chloroquinolin-Ethenyl Phenyl Derivative Using Thin Layers Impregnated With Di-P-Toluyl Tartaricacid

Abstract

Thin Layer Chromatography (TLC) is an established method for the evaluation of final product drug and intermediate impurity profiles. Quantitative TLC has gained credibility within the Pharmaceutical industry as a result of the latest developments in an availability of scanning technology. In the present paper we wish to report a quantitative TLC method for the determination of some potential impurities which may exist in a final bulk drug MK0679. In order to improve the selectivity of the chromatographic method, di-p-toluyl tartaric acid was impregnated on the stationary phase. Utilizing the modified layer, complete separation of the known impurity was obtained. The calibration curves for all components studied were linear and the detection limits obtained were less than 5ng.     

Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

Using the high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) technique, together with established trends from the literature, the structures of metabolites and impurities of amiodarone, an anti-arrhythmic drug, have been assigned. By comparing analyses of products of incubation with rat liver microsomes with controls in which glucose 6-phosphate dehydrogenase was omitted, metabolites could be distinguished from impurities. Structures for the two proposed metabolites and four impurities are proposed.     

Densitometric Determination of Omeprazole,Pantoprazole, and their Impurities in Pharmaceuticals

JPC – Journal of Planar Chromatography – Modern TLC - A method has been developed for separation of omeprazole and pantoprazole, and their impurities omeprazole sulfone and...     

Separation and identification of moxifloxacin impurities in drug substance by high-performance liquid chromatography coupled with ultraviolet detection and Fourier transform ion cyclotron resonance mass spectrometry

In this paper,a high-performance liquid chromatography coupled with ultraviolet detection and Fourier transform-ion cyclotron resonance mass spectrometry(HPLC-UV/FTICRMS) method was described for the investigation of impurity profile in moxifloxacin (MOX) drug substance and chemical reference substance.Ten impurities were detected by HPLC-UV,while eight impurities were identified by using the high accurate molecular mass combined with multiple-stage mass spectrometric data and fragmentation rules.In addition,to our knowledge,five impurities were founded for the first time in MOX drug substance.     

Determination of minor impurities in temafloxacin hydrochloride by high-performance liquid chromatography

Minor impurities in the antibacterial agent temafloxacin hydrochloride were determined using high-performance liquid chromatography. Manufacturing impurities and degradation products were separated using a reversed-phase system with gradient elution. Detector response was linear for the individual impurities to approximately 50 micrograms/ml which represents 2.5% of the drug concentration. The procedure provides quantitation of impurities to approximately the 0.05% level with precision (relative standard deviations) of 4.7% to 29% in typical bulk drug lots. A variety of reversed-phase columns were evaluated for the assay method with optimum resolution achieved using a 5-microns Nucleosil C18 packing.     

Application of TLC and OPLC in the Determination of Pigments from Natural Products

JPC – Journal of Planar Chromatography – Modern TLC - Planar chromatographic methods thin-layer chromatography (TLC) and over-pressure thin-layer chromatography (OPLC) have been...     

Synthesis and Spectral Characterization of Related Substances of Lacidipine,an Antihypertensive Drug

Five related substances (impurities) were detected in lacidipine bulk drug substance by a simple high-performance liquid chromatographic method (HPLC) and were identified by liquid chromatography–mass spectrometry (LC-MS). These related substances were independently synthesized, characterized, and co-injected with the sample containing impurities.     

LC Separation of Co-Existing Cetylpyridinium Chloride, Tetradecyltrimethylammonium Bromide and Dodecyltrimethylammonium Bromide on Silica TLC Plates with Aqueous-Organic Eluents

Thin-layer chromatography (TLC) of three cationic surfactants was performed on silica TLC plates with various solvent systems. The mutual separation of cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB) was achieved on silica TLC plates with ethanol: 1% aqueous ammonium chloride (4:6, v/v) as an eluent. Effects of cations and anions in the mobile phase on mobility and separation of CPC, TTAB and DTAB were examined. The interference due to the presence of metal cations as impurities on the resolution in the mixture of CPC, TTAB and DTAB was also examined. The limits of detection of CPC, TTAB and DTAB estimated were 0.015, 0.031 and 0.062 μg zone⁻¹, respectively. The developed method was utilized to identify these surfactants in different spiked water samples after their preliminary separation.     

Investigation of amodiaquine bulk drug impurities by liquid chromatography/ion trap mass spectrometry

Three unknown impurities in an amodiaquine bulk drug sample were detected by reversed-phase high-performance liquid chromatography with ultraviolet detection (HPLC/UV). A liquid chromatography/tandem mass spectrometry (LC/MS(n)) method is described for the investigation of these impurities. Mass spectral data were acquired on an LCQ ion trap mass analyzer equipped with an electrospray ionization (ESI) source operated in positive ion mode. The fragmentation behavior of amodiaquine and its impurities has been studied. Based on the mass spectral data and the specifics of the synthetic route, the possible structures of these impurities were elucidated as 4-[(5-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)phenol (impurity I), 4-[(7-chloroquinolin-4-yl)-amino]phenol (impurity II) and 4-[(7-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)-N(1)-oxy]phenol (impurity III). The structures were confirmed by their independent synthesis and NMR spectral assignment.     

Identification,characterization, and high‐performance liquid chromatography quantification of process‐related impurities in vonoprazan fumarate

High‐performance liquid chromatography analysis of vonoprazan fumarate, a novel proton pump inhibitor drug revealed six impurities. These were identified by liquid chromatography with mass spectrometry. Further, the structures of the impurities were confirmed by synthesis followed by characterization by mass spectrometry, NMR spectroscopy, and infrared spectroscopy. On the basis of these data and knowledge of the synthetic scheme of vonoprazan fumarate, the previously unknown impurity was identified as 1‐[5‐(2‐fluorophenyl)‐1‐(pyridin‐3‐ylsulfonyl)‐1H‐pyrrol‐3‐yl]‐N‐methyldimethylamine, which is a new compound. The possible mechanisms by which these impurities were formed were also discussed. A high‐performance liquid chromatography method was optimized in order to separate, selectively detect, and quantify all process‐related impurities of vonoprazan fumarate. The presented method has been validated in terms of linearity, limits of detection, and quantification, and response factors and, therefore, is highly suitable for routine analysis of vonoprazan fumarate related substances as well as stability studies.     

Frontal elution and frontal displacement methods in thin-layer chromatography and their use in concentrating of impurities

A new method of TLC is proposed for concentrating and separating diluted solutions of samples. Samples being analyzed are concentrated in a narrow band on a plate using the displacement version of TLC the aim of lowering the detection limit of the impurities. We compare the frontal elution described in the first work on TLC by Izmailov and Shraiber with the frontal displacement suggested in this work for concentrating diluted solutions of samples and their further separation by linear TLC. It is demonstrated that using displacement TLC in the analytical process allows us to raise the efficiency of separating the compounds under study, and to lower their detection limit by a factor of 10³. We conclude that the use of this approach for the determination of impurities in TLC is advisable in analytical practice.     

High-performance thin-layer chromatography (HPTLC) method for analysis of secondary metabolites of Semiaquilegiae Radix

JPC – Journal of Planar Chromatography – Modern TLC - Semiaquilegiae Radix has been extensively investigated for its cytotoxic, antitumor, anti-inflammatory, antibacterial,...     

Drug impurity profiling strategies

A general scheme is set up for the estimation of the impurity profile of bulk drug substances by the complex use of chromatographic, spectroscopic and hyphenated techniques. Several examples are presented as illustrations to the scheme from the authors' laboratory involving the use of chromatographic methods such as thin-layer-(TLC), gas-(GC), analytical and preparative high-performance liquid chromatography (HPLC), spectroscopic methods such as mass spectrometry (MS) and NMR spectroscopy as well as hyphenated techniques (HPLC/diode-array UV, GC/MS and HPLC/MS). In addition to summarizing earlier work, new examples are also presented: identification of an impurity (propyl 4-[diethylcarbamoyl(methoxy)]-3-methoxy phenylglyoxylate, II) in propanidid (I) and two unsaturated impurities in allylstrenol (VII) by GC/MS and HPLC/diode-array UV as well as estimation of the impurity profile of mazipredone (III) by HPLC/MS and HPLC/diode-array UV.     

Quantitative analysis by thin-layer chromatography with secondary ion mass spectrometry

Summary A direct combination of thin-layer chromatography with secondary ion mass spectrometry (TLC/SIMS) provides a method for the quantitative analysis of thermally unstable compounds or compounds of low volatility such as nicergoline. The method is very simple and has excellent precision. The analysis was performed by using an aluminium TLC plate and a mixture of methylene chloride, acetone, and distilled water as a developing solvent. After development the portion of the plate with the nicergoline and the internal standard spots was cut off the TLC plate, and was attached to the SIMS holder directly. The amount of nicergoline was determined from the ratio of the fragment ion intensity of the nicergoline to the internal standard. The calibration curve was linear, and the detection limit was 10 ng at a signal-to-noise ratio of 5. This method should be considered for application to the determination of drugs in biological samples and also for the determination of possible impurities and decomposition products in drugs.     

Recognition of Artifacts Occurring in TLC

Abstract

The increased production of drugs requires a concomitant assessment of drug purity. Chromatography in general, and thin layer chromatography in particular, play an important role in determination of the impurity profiles of drug candidates. However, in using chromatography to determine impurities, the chemist must be careful, since extraneous zones or spots do not always indicate impurities. They may instead be artifacts, produced in the chromatographic system. In this paper we present a phenomenon related to on-plate decomposition. MK0912 was chosen as a model compound. To overcome the on-plate degradation an inclusion compound was formed with γ-cyclodextrin in the spotting solution, followed by a mobile phase containing hexadecyltrimethylammonium bromide as a micelle generator. This technique proved to be successful for preventing degradation during chromatography.