Development and Validation of Stability-Indicating HPLC Methods for Quantitative Determination of Pravastatin,Fluvastatin, Atorvastatin,and Rosuvastatin in Pharmaceuticals

Abstract

High-performance liquid-chromatographic (HPLC) methods were validated for determination of pravastatin sodium (PS), fluvastatin sodium (FVS), atorvastatin calcium (ATC), and rosuvastatin calcium (RC) in pharmaceuticals. Two stability-indicating HPLC methods were developed with a small change (10%) in the composition of the organic modifier in the mobile phase. The HPLC method for each statin was validated using isocratic elution. An RP-18 column was used with mobile phases consisting of methanol–water (60:40, v/v, for PS and RC and 70:30, v/v, for FVS and ATC). The pH of each mobile phase was adjusted to 3.0 with orthophosphoric acid, and the flow rate was 1.0 mL/min. Calibration plots showed correlation coefficients (r) > 0.999, which were calculated by the least square method. The detection limit (DL) and quantitation limit (QL) were 1.22 and 3.08 µg/mL for PS, 2.02 and 6.12 µg/mL for FVS, 0.44 and 1.34 µg/mL for ATC, and 1.55 and 4.70 µg/mL for RC. Intraday and interday relative standard deviations (RSDs) were <2.0%. The methods were applied successfully for quantitative determination of statins in pharmaceuticals.     

Optimisation of the analysis of anti-influenza drugs in wastewater and surface water

We optimised the simultaneous analysis of four analytes, namely three anti-influenza drugs (oseltamivir (OS), zanamivir (ZAN) and amantadine (AMN)) and one metabolite of OS (oseltamivir carboxylate (OC)), in sewage treatment plant (STP) influent and effluent by verifying the types and conditions of solid phase extraction (SPE) appropriate for LC-MS/MS analysis. In summary, these target analytes were extracted from aqueous samples (30–50 mL) by using strong cation-exchange SPE cartridges (500 mg adsorbent) under acidic conditions (pH 3–4). After washing of the cartridges with acidified water (pH 3.0, 3 mL) and methanol (3 mL), the analytes were eluted with a mixed solvent (2 mL) of 10% (v/v) triethylamine in a 1:1 (v/v) mixture of acetone and water. Application of this technique to the target compounds should yield a comprehensive understanding of the occurrence and fate of anti-influenza drugs in the water environment.     

Development of a One-Shot Optical Citrate Sensor Based on a Guanidinium Synthetic Receptor

A new optical absorption-based one-shot sensor for the determination of citrate is described. The citrate-sensitive element is a plasticized polymeric membrane containing a synthetic guanidinium receptor and a pH-sensitive lipophilic dye. The rigid amide-based receptor with C₃ symmetry controls the anion selectivity pattern of the optical element. The optical selectivity coefficients obtained for citrate over a variety of common carboxylate anions meet the requirements for the determination of citrate in different types of samples. The one-shot sensor responds rapidly – in 40 s – and reversibly to citrate over a dynamic range of 0.779 to 25.0 mM with a sensor-to-sensor reproducibility of 5.7%, as log a_cit, in the medium level of the range. The performance of the optical one-shot sensor has been tested in the analysis of citrate in soft drinks and pharmaceuticals, validating the results against a reference procedure. The proposed method is quick, inexpensive, selective and sensitive, and uses conventional instrumentation only.     

Liquid chromatographic–tandem mass spectrometry assay for the quantification of MDT‐637 in human nasal wash

MDT‐637 is a new chemical entity that shows potent and selective antiviral activity against respiratory syncytial virus. As part of the new drug development program, a method for quantitating MDT‐637 in nasal wash collected from human subjects was required. This article describes the method development and validation and application of a bioanalytical assay for MDT‐637 in human nasal wash using liquid chromatography–tandem mass spectrometry. Sample pretreatment utilized supported liquid extraction and final extracts were injected onto an Agilent Poroshell 120 EC‐C₁₈ column and eluted under isocratic conditions of 65:35 (v/v) 10 mm ammonium formate in water and acetonitrile Detection was performed on an API 5000 tandem mass spectrometer operating in negative electrospray ionization mode applying multiple reaction monitoring. The assay was validated in accordance with the US Food and Drug Administration guidance on bioanalytical method validation and was applied in support of a Phase IIa human safety and tolerability study.     

Validation criteria for developing ion-selective membrane electrodes for analysis of pharmaceuticals

 The problem of validation criteria for developing ion-selective membrane electrodes for the analysis of pharmaceuticals arises from the connection between the reliability of ion-selective membrane electrodes construction and the reliability of the analytical information. Liquid membrane selective electrodes are more suitable for validation than the solid variety. The influence of the stability of ion pair complexes from the membrane on various parameters (e.g. response, limit of detection, and selectivity) is discussed. Validation criteria are proposed. Received: 18 September 1997 · Accepted: 17 November 1997     

Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere

Pharmaceutical and agrochemical discovery programs are under considerable pressure to meet increasing global demand and thus require constant innovation. Classical hydrocarbon scaffolds have long assisted in bringing new molecules to the market place, but an obvious omission is that of the Platonic solid cubane. Eaton, however, suggested that this molecule has the potential to act as a benzene bioisostere. Herein, we report the validation of Eaton's hypothesis with cubane derivatives of five molecules that are used clinically or as agrochemicals. Two cubane analogues showed increased bioactivity compared to their benzene counterparts whereas two further analogues displayed equal bioactivity, and the fifth one demonstrated only partial efficacy. Ramifications from this study are best realized by reflecting on the number of bioactive molecules that contain a benzene ring. Substitution with the cubane scaffold where possible could revitalize these systems, and thus expedite much needed lead candidate identification.     

Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part II: Heptakis(3-O-acetyl-2,6-di-O-pentyl)-ß-cyclodextrin

Heptakis (3-O-acetyl-2,6-di-O-pentyl)-ß-cyclodextrin is used as a chiral stationary phase in capillary gas chromatography. High enantioselectivity towards trifluoro-acetylated α and β-chiral amines, amino alcohols, α- and β-amino acid esters, and cyclic trans-diols is observed. In contrast to chiral polysiloxane phases, where hydrogen bonding interaction is essential for enantiomer separation, in cyclodextrins inclusion properties contribute to enantioselectivity. This can be concluded from the separation of N-alkylated amino compounds. The new chiral stationary phase exhibits a wide operating temperature range and is stable above 200°C.     

Gas in scattering media absorption spectroscopy – from basic studies to biomedical applications

The recently introduced Gas in Scattering Media Absorption Spectroscopy (GASMAS) technique provides novel possibilities for analysis in biophotonics. Free gas in pores or cavities is monitored with narrow‐band laser radiation, which can discern the gas absorptive imprints which are typically several orders of magnitude more narrow than the features of the surrounding tissue through which the diffusely scattered light emerges to the detector. Important gases monitored are oxygen and water vapour. Applications include diagnosis of human sinus cavities and surveillance of neonatal children, but also characterization of food‐stuffs, food packages and pharmaceutical preparations. Non‐biological applications include the study of construction materials such as wood, polystyrene foams and ceramics. For nano‐porous materials, information on the pore sizes can be obtained from observed line broadening. Apart from concentration measurements, the GASMAS technique also allows the study of gas transport and diffusion, and pressure and temperature information can also be obtained.     

A Fluorescence Spot Test for Salicylate Determination

Abstract

A procedure based on a spot test for salicylate is presented. The method is simple, rugged and is based on the salycilate native fluorescence measurement on the surface of a filter paper by using optical fibers for light conduction. The fluorescence was linear at concentration range of 0.01–0.4 mmol l^?1. The relative standard deviation of 5% (n=10) was observed. Detection and quantification limits were 4 and 14 µmol l^?1, respectively. The results obtained in pharmaceutical salicylate determinations showed that practically no statistical difference existed with the pharmacopeical method (95% confidence level). The recovery studies in biological samples spiked with salicylic acid at overdose concentration levels showed that the matrix sample did not interfere in the method.     

Simultaneous Quantification of Three Polymorphic Forms of Carbamazepine using Raman Spectroscopy and Multivariate Calibration

Carbamazepine is a pharmaceutical product used to treat epilepsy and bipolar disorder. Some active pharmaceutical ingredients, such as carbamazepine, present polymorphism that may alter the bioavailability. Consequently, the determination of different polymorphic forms has become important for the pharmaceutical industry. In this work, polymorphic forms were synthesized and characterized by differential scanning calorimetry and X-ray diffraction. Raman spectroscopy was used to quantify mixtures of the three common polymorphic forms of carbamazepine. A ternary mixture design was used to create the calibration set of ten samples and six levels of concentration for each polymorph. Partial least squares was performed to build the prediction models. Ten spectra were obtained to obtain representative Raman spectra of the mixtures. The calibration models were built using the average spectra, and an external set of samples was used to evaluate the models. The partial least squares model gave a root mean square error of prediction of 6.2% for carbamazepine I, 6.8% for carbamazepine III, and 11.6% for carbamazepine dihydrate. The results showed that good results were obtained for the solid state characterization of the mixtures of polymorphs using a fast strategy for simultaneous analysis.