Solvent Delivery Research Articles

A simplified tutorial on charged aerosol detection: Understanding the basics, optimization, and troubleshooting

The charged aerosol detector (CAD) measures the overall charge deposited on aerosolized particles to produce a signal proportional to the mass of analyte present, which applies to compounds with or without a chromophore. A significant benefit of CAD is the ability to quantitate a wide range of non-volatile compounds in absence of their authentic standards due to uniform response factor for such analytes. CAD is also a valuable tool to help detect and/or quantitate compounds with poor or no UV absorption. These can include salts, impurities, and a variety of other types of analytes.In this tutorial, fundamental principles of CAD and its utilization, troubleshooting, and maintenance will be demonstrated to ensure proper CAD usage. Successful operation of CAD includes optimizing power function value (PFV) to allow for a broader dynamic range and improve uniformity of response. The use of an inverse gradient (admixed post-column) enables more accurate quantitation, when employing a gradient analysis method. Several troubleshooting strategies, including diagnosing inverse gradient pump organic solvent delivery and determining volume match/mismatch between the inverse gradient and system pumps, will be presented along with important aspects of operating a CAD. Lastly, ensuring reliable results involves monitoring the performance of CAD over time to understand whether it is working sufficiently or if maintenance is required.

A greener RP-HPLC method for quaternary estimation of caffeine, paracetamol, levocetirizine, and phenylephrine acquiring AQbD with stability studies

Abstract The main objective of this article was to develop method and validate quaternary estimation of caffeine (CFE), paracetamol (PCM), levocetirizine (LEV), and phenylephrine (PHE) and to conduct degradation experiments using reverse-phase high-performance liquid chromatography (RP-HPLC). This was the first innovative approach to this drug combination, combining analytical quality by design with green analytical chemistry. This method was developed using HPLC Agilent 1220 Infinity II, a binary solvent delivery pump, an automatic sampling device injector, and a photodiode array detector. Agilent Inertsil ODS 3 (250 mm × 4.6 mm, 5 μm) was used for separation. The mobile phase is composed of ethanol and 10 mM phosphate buffer (pH 3). To adjust the pH, 1% of orthophosphoric acid was used. The flow rate was set to 0.8 ml·min−1, the injection volume was 10 μl, and the detecting wavelength was 220 nm. The analytes were eluted via gradient elution. The retention time for PCM was 3.5 min, CFE was 8.1 min, PHE was 15.9 min, and LEV was 20.5 min. Green evaluation tools used in this research include Green Analytical Procedure Index, analytical eco-scale, analytical greenness, analytical method greenness score, and carbon footprint analysis. The developed method was greener than the previously reported method, as per the results of the greenness evaluation tools.

Facile synthesis and self-assembly of pharmaceutically important oligobenzylidene-d-sorbitol dialdehydes: direct encapsulation and stimuli responsive delivery of H2S

We report the direct in situ encapsulation of H2S into the gel formed by a pharmaceutical solvent and stimuli-responsive delivery, which enable future studies of the physiological role of H2S in various biological processes.

Stability-indicating method development and validation for quantitative estimation of organic impurities of the antidiabetic drug glipizide in drug substance and pharmaceutical dosage form using HPLC.

Glipizide is an antidiabetic drug used for the treatment of type 2 diabetes. A simple, reliable and robust reverse-phase liquid chromatographic method (RP-HPLC) was developed and validated as per International Conference on Harmonization Q2(R1) for estimating the impurities of glipizide in pharmaceutical formulations. The chromatographic separation was carried out on a Phenomenex Luna C18 (2), 250 × 4.6mm, 5μm with a binary solvent delivery system [MP-A, a homogenous mixture of water and acetonitrile in a ratio of 90:10 (v/v) and 1ml of orthophosphoric acid; and MP-B, a homogenous mixture of water and acetonitrile in a ratio of 10:90 (v/v) and 1ml of orthophosphoric acid] with a detection wavelength of 225 nm, a column temperature of 30°C, a flow rate of 1.5ml/min, and an injection volume of 20 μl. All process, degradant and unknown impurities were separated well with a resolution >2.2 and were estimated accurately without any interference. The recovered values and regression values were 98.7-100.5% and R2 > 0.9999, respectively. The recovery and linearity studies covered the quantitation limit to 150% of the specification limit. The stability-indicating properties of the developed RP-HPLC method was assessed from the forced degradation studies. The developed method was successfully applied for real-time sample analysis of the glipizide dosage form.

Stability-Indicating Method Development and Validation for Quantitative Estimation of Assay and Organic Impurities of anti-viral drug Baloxavir-Marboxil in Drug Substance and Pharmaceutical Dosage Form using HPLC and LC-MS Methods.

Baloxavir-Marboxil (BXM) is a polymerase-acidic-endonuclease inhibitor used as an anti-viral drug. A simple, reliable, and robust liquid chromatographic method was developed and validated per ICH Q2(R1) for estimating the assay and impurities of BXM in drug substance and pharmaceutical formulations. The chromatographic separation was carried-out on C18 (100 x 4.6 mm, 5-μm) with binary solvent delivery system (A:0.1% trifluoroacetic-acid in water; B:0.1% trifluoroacetic-acid in acetonitrile) along with detection wavelength of 260 nm, column temperature of 57°C, flow of 1.2-mL/min and injection volume of 10-μL. All five known impurities and unknown impurities were separated well with resolution >1.7, and were estimated accurately without any interference. Recovered values and regression value were 99.5-101.2% and R2 >0.999, respectively. The recovery and linearity studies covered from 50-150% for assay, and quantitation limit (QL) - 120% for five BXM impurities. Stability-indicating property of the HPLC developed method was assessed from the forced degradation studies. The mass spectral data of unknown impurity formed under oxidation stress condition was discussed. The developed method was also successfully utilized for stability samples analysis of drug substance and tablets dosage form.

Ultrafast, High-Strain, and Strong Uniaxial Hydrogel Actuators from Recyclable Nanofibril Networks.

Synthetic polymeric hydrogels mimic biological tissues and are suitable for future lifelike machines. However, in polymer hydrogel actuators, actuation is isotropic, so they must be crosslinked or placed in a turgor membrane to achieve high actuation pressures, severely impeding their performance. Here, we show that organizing cellulose nanofibrils in anisotropic fibrillar networks leads to hydrogel sheets with a mechanical in-plane reinforcement that generates a uniaxial, out-of-plane strain with performance far surpassing polymer hydrogels. These fibrillar hydrogel actuators expand uniaxially by 250 times with an initial rate of 100-150% s-1 , compared to <10 times and <1% s-1 in directional strain rate for isotropic hydrogels, respectively. The blocking pressure was up to 0.9MPa, similar to turgor actuators, while the time to reach 90% of the max pressure was 1-2 minutes, compared to 10 minutes to hours for crosslinked polymers or turgor actuators. We showcase uniaxial actuators that lift objects 120 000 times their weight and soft grippers that grasp objects. In addition, the hydrogels could be recycled without a loss in performance. The uniaxial swelling allowed adding channels through the gel for local solvent delivery, further increasing the actuation rate and cyclability. Thus, fibrillar networks can overcome the major drawbacks of hydrogel actuators and is a significant advancement toward hydrogel-based lifelike machines. This article is protected by copyright. All rights reserved.

Evaluation and improvement of a miniature mass spectrometry system for quantitative harm reduction drug checking

The increasing variability of the illicit drug market has imposed serious health risks for people who use drugs (PWUD), particularly due to the increasing co-occurrence of opioids and etizolam (or other benzodiazepines) in some jurisdictions. A miniature mass spectrometer (MS) equipped with paper capillary spray ionization was evaluated for its ability to quantify fentanyl, fluorofentanyl, carfentanil, and etizolam in illicit drug samples. Prior to testing actual drug samples, inter- and intra-day reproducibility, calibration linearity, and analytical sensitivity were assessed. The development of a continuous spray solvent delivery system improved MS/MS quantitation by prolonging ionization stability. A simple, rapid and quantitative tandem mass spectrometry method was developed and employed for the analysis of real-world illicit drug samples provided by PWUD at a harm reduction site in Victoria, British Columbia, Canada. Limits of detection ranged from 0.001 to 0.24% w/w of illicit analyte in the original solid drug samples. Target analytes were detected and quantified via the miniature MS system for samples where conventional on-site drug checking technologies were not always effective. These promising results demonstrate the potential role for miniature mass spectrometer systems for on-site drug checking services that can be both sensitive to trace, toxic levels as well as adaptable/selective for new drug threats as they appear in the illicit drug supply.

Coupling handheld liquid microjunction-surface sampling probe (hLMJ-SSP) to the miniature mass spectrometer for automated and in-situ surface analysis.

In-situ surface analysis has always been a significant but challenging issue in many analytical applications. To enable surface sampling and MS analysis on the field, a handheld liquid microjunction-surface sampling probe (hLMJ-SSP) was coupled to a miniature mass spectrometer in this study. The hLMJ-SSP was connected to the miniature mass spectrometer with a 50cm long flexible tube and controlled by an integrated microcontroller unit (MCU). By simply pressing a button on the probe, automated surface analysis could be carried out and completed within ∼2min, in which solvent delivery, sample extraction, extract aspiration, injection and MS analysis were performed in sequence. A limit of detection (LOD) as low as 5pg was achieved. The capability of in-situ surface analysis was also demonstrated by directly analyzing illicit drug residues on fingers and medicines in biological fluids. With the merits of automated operation, high sensitivity and nondestructive analysis, this LMJ-SSP-mini MS system would be a promising tool for various in-situ analytical applications.

Characterization and optimization of a rapid, automated 3D-printed cone spray ionization-mass spectrometry (3D-PCSI-MS) methodology

3D-printed cone spray ionization-mass spectrometry (3D-PCSI-MS) is an ambient ionization technique developed for the rapid, in-situ analysis of bulk solids and trace analytes within solid matrices. A reproducibly fabricated 3D-printed cone is used as the collection device, the extraction chamber, and the spray-based ionization source. Herein, we discuss the material selection based on the extraction and spray solvent compatibility with conductive plastic types, the strength of the selected material, and the advantages and disadvantages of the cone geometry. The ease of printing and the required parameters for reproducible manufacturing is also documented. To allow for improved sample throughput, reproducible positioning, and automated solvent delivery and analysis, an autosampler was developed from commercial-off-the-shelf (COTS) parts and custom 3D-printed pieces. Finally, the application of this automated sampling via 3D-PCSI-MS on a field portable mass spectrometer was demonstrated for environmental, defense, and forensic applications.

Research advances in nano liquid chromatography instrumentation

小型化是液相色谱分离技术发展的重要趋势之一,包括仪器外形尺寸的小型化、分离材料粒径的小型化以及色谱柱内径的小型化。色谱柱内径的减小能够降低样品和流动相的消耗,具有更高的质量灵敏度,特别适合用于复杂样品体系的分离分析。纳升液相色谱一般是指使用内径小于100 μm的毛细管色谱柱,流速范围在每分钟几十至几百纳升的色谱技术。由于流速很低,色谱柱体积很小,柱外效应显著,因此对色谱仪器系统各个模块的性能以及系统柱外效应的优化提出了较高的要求。纳升液相色谱的输液装置需要能够准确稳定地输送纳升级流速,具有梯度输液模式,且拥有一定的耐压能力,以适应不同规格的色谱柱类型;进样装置需要能够进行准确重复的进样过程,进样体积及进样方式适合毛细管色谱柱,同时不产生明显的柱外效应;检测装置需要具有较高的灵敏度,且具有较小的柱外扩散;管路与连接系统需要稳定、可靠、易操作,并能够最大限度地减小柱外体积,适配纳升级流速。鉴于目前大多数纳升液相色谱系统与质谱检测器联用,因而本文主要从输液装置、进样装置、管路与连接3个方面对相关技术领域的研究论文、技术专利以及仪器厂商的宣传文件等进行了检索与归纳,综述了这些模块的技术路线与研究进展,同时简要介绍光学吸收型检测装置的优化思路与研究进展,并对部分商品化的纳升液相色谱系统进行了对比。

Simultaneous separation of insulin and six therapeutic analogues on a mixed mode column: HPLC-UV method development and application

Human insulin and six most used therapeutic analogues are very similar in terms of retention on a reversed-phase column. Thus, the LC methods prescribed in the European Pharmacopoeia monographs for insulin and insulin analogues include many similar separation methods, which tend to be time consuming when separating individual products of insulins or are inadequate when handling a mixture. In this study, we present a simple, robust, versatile and accessible HPLC-UV separation method for identification and quantification of human insulin and its analogues in one run. The simultaneous separation and detection is possible by fine-tuning the mobile phase properties that affect the separation mechanism on a mixed mode column combining anion exchange and reversed-phase characteristics. Also developed was a simple and effective SPE sample cleaning procedure with insulin recoveries ranging from 80 to 100% for all analogues. On the other hand, the concentration of major excipients such as phenol and m-cresol fall below 1%. The two developed and validated separation methods differ in their compatibility with the use of a quaternary or binary pump, thus enabling sample characterisation independent of the HPLC solvent delivery system. The methods are compatible with the use of a mass spectrometric detector for an indisputable identification.

Sensitivity Analysis of a Simulated Hydrogel

AbstractCrosslinked polyelectrolytic polymers embedded in an aqueous solution, so‐called hydrogels, show stimuli‐responsive behaviour under various kinds of stimulation. These “smart” reactions can be triggered by e.g. chemical, electrical, mechanical or thermal stimuli. The hydrogels react via uptake or delivery of mobile ions and solvent, and show enormous swelling capabilities. This behaviour can be used for chemo‐electro‐mechanical energy converters or as an actuator or sensor.The presented research investigates anionic hydrogels in the framework of a sensitivity analysis, by a design of experiment (DOE) with the use of ANSYS optiSLang. The hydrogel itself is modelled within a finite element code (Abaqus Unified FEA) as a user element. The applied stimuli are of different nature: chemical, electrical, mechanical and thermal.On the one hand, the stimulus is applied by the change of boundary conditions, e.g. for chemical stimulation by a change of the concentrations of the constituents themselves (Na+ and Cl−). For electrically stimulated hydrogels, two electrodes are incorporated at the boundaries and the electric potential is changed. On the other hand, the mechanical stimulus is defined by prescribed displacements at a boundary of the fixed hydrogel. The thermal stimulus is applied over the whole domain in the form of transient temperature changes with temperature‐dependent material parameters. The reactions of the hydrogel differ – depending on the type of hydrogel and the stronger or weaker sensitivity – on the applied stimulus. The fully coupled three‐field description of the chemo‐electro‐mechanical model enhanced with thermal dependencies is capable of giving local concentrations, electric potential and displacements.

Development and Validation by Reverse Phase High Performance Liquid Chromatography Method for the Estimation of Piperine and Coenzyme Q10 in Bulk and Pharmaceutical Dosage Form

Today people are focused on their health, as good health is a key to the happiness of our life. Medicine takes a big responsibility to take care of our health. Various supplements are available to meet the nutritional requirement. One such supplement is a combination of piperine and coenzyme Q10. The medicines have to be analyzed properly before introducing them to the market. As no analytical method is available for simultaneous estimation of the combination, hence an attempt was made to develop a validated method for the estimation of piperine and coenzyme Q10 simultaneously in bulk and its dosage form. A simple, precise, accurate and validated reversed phase high performance liquid chromatography technique was developed for the estimation of piperine and coenzyme Q10 in bulk and its tablet formulation. In this developed method, Waters X Bridge C18 column (250 mm×4.6 mm, 5 μm) was used as a stationary phase and acetonitrile, tetrahydrofuran and water was used in 65:32:3 (v/v) ratio as mobile phase with 1 ml/min flow rate. This isocratic separation was accomplished using Waters 2707 Autosampler high performance liquid chromatography system, Waters 515 solvent delivery system, with photodiode array detector detection at 275 nm. Chromatographic data was processed by Empower 2 software. The retention times of coenzyme Q10 and piperine were 4.56 and 8.19 min respectively. The linearity ranges have lied between 4-6 μg/ml, 240-360 μg/ml for piperine and coenzyme Q10 respectively with 0.997 as correlation coefficient for both.

REAGENT TARGET DELIVERY TO ELECTRIC CENTRIFUGAL PUMP SUCTION

Background The subsurface equipment of an oil producing well serves for recovery products to the surface of the earth and its structurally imperfect for delivering a physicochemical reagent to receive a submersible pump suction. Periodic and timely flushing of the pump and the tubing string with a suitable solvent while maintaining the necessary characteristics of the gas-liquid composition at the pump suction is the key to a long and effective operation of the producing well. In the article it was considered the existing technologies for the delivery of reagents to the zone with deposits and prepossessed a new route for the movement of solvent and inhibitor from the wellhead pump to the electric centrifugal pump suction. Aims and Objectives: o analysis of technologies for the delivery of organic solvent to the submersible pump suction for an oil well, complicated by the presence of asphalt-resin-paraffin deposits (ARPD), to identify the potential for improving this technological procedure; o development of an intrawell device for target delivery of reagents to the submersible pump suction. Methods: o study of the experience of using capillary and coil-tubing pipes for injecting solvents and inhibitors into the zone with well deposits; o estimation of operating parameters of the reagent tube in the cavity of the column of tubing strings using the Darcy-Weisbach equation. Results To remove ARPD from a deep pumping equipment, oil companies, as a rule, use solvent injection through the annulus, thereby reducing the functionality of the reagent. Oil industry workers proposed for consideration the scheme of reagent supply through a tube of considerable diameter located in the cavity of the tubing string.

An Overview of Simulated Hydrogel Behaviour under Various Kinds of Stimulation

AbstractPolyelectrolytic gels placed in aqueous solution show effects under various kinds of stimulation. The stimuli could be e.g. of chemical, electrical, mechanical or thermal nature. The hydrogels react via uptake or delivery of mobile ions and solvent, and they show enormous swelling capabilities. This multifunctional behaviour is potentially attractive for chemo‐electro‐mechanical energy converters or for the use as actuators or sensors. In the present research, anionic and cationic hydrogels are investigated, which means that the polymer network contains anionic or cationic bound charged groups. The chemical stimulation is applied by a change of boundary conditions in the solution bath for the salt concentrations. The electrical stimulus is realized by incorporating electrodes between which an electric potential difference is applied. The mechanical stimulus is realized by prescribed displacements at a boundary of the hydrogel itself. The thermal stimulus is applied as transient temperature change over the whole domain, incorporating temperature‐dependent material parameters and osmotic pressure differences. The reactions of the hydrogel differ depending on the sensitivity of the gel to the applied stimulus. The incorporated chemo‐electro‐mechanical model enhanced with thermal dependencies is capable of giving local concentrations, electric potential and mechanical displacements.

The Methoxylated, Highly Conjugated C40 Carotenoids, Spirilloxanthin and Anhydrorhodovibrin, Can Be Separated Using High Performance Liquid Chromatography with Safe and Environmentally Friendly Solvents.

High performance liquid chromatography (HPLC) is a frequently used technique in carotenoid research. So far, however, little attention has been paid to the fact that many of the organic solvents used in HPLC separation of highly apolar C40 carotenoids impose a significant threat to both health (especially for women) and the general laboratory environment. Here, we developed a solvent combination capable of allowing high-resolution HPLC separation of the C40 carotenoid, spirilloxanthin, and all of its biosynthetic precursors beginning with phytoene, using relatively safe, environmentally friendly solvents. We show that separation of spirilloxanthin and its precursors anhydrorhodovibrin and lycopene using modern ultra-high performance chromatography (UHPLC) poses particular problems for apolar carotenoid separation, due to the long residence times in the sample delivery system, which facilitates carotenoid aggregation. We resolved these problems by developing the solvent delivery combination acetone/acetonitrile/isopropanol/methanol (65/30/5/2 (v/v/v/v)), which allows excellent column separation using the safe isocratic solvent system methanol/tetrahydrofuran (98/2 (v/v)). We also demonstrate that the development strategy for optimizing a solvent system for carotenoid separation can be well-described by the use of the average dielectric constant of the total sample delivery solvent, and present a formal method for analysis of the efficiency of separation.

Behaviour of Anionic and Cationic Hydrogels

AbstractIonic polyelectrolytic gels in an aqueous solution, i.e. hydrogels – also known as smart materials – react to different kinds of environmental changes, e.g. chemical, electrical, mechanical, and thermal stimulation. As a reaction, they show enormous swelling capabilities resulting from the delivery or uptake of ions and solvent. These properties make them attractive for chemo‐electro‐mechanical energy converters and for the application as actuators or sensors. The applied multi‐field formulation consists of the chemical, electrical, and mechanical field and is capable of giving local concentrations, electric potential distributions and displacements. In this excerpt the reaction of a modelled hydrogel finger gripper under electrical stimulation is shown. The swelling ratio is assumed to be in the regime of small volume changes and corresponding displacements.

Piezoelectric-based high performance spray solvent delivery system for desorption electrospray ionization mass spectrometry: Systematic design and case studies for high throughput screening of N-alkylation reactions

Desorption electrospray ionization mass spectrometry (DESI-MS) is a powerful tool for ultra-high throughput chemical reaction screening having enormous scientific and practical implications. DESI-MS enables considerably faster chemical reaction and/or product discovery than most current screening methods using very small amount of materials. It has the advantage of bringing the reagents in contact inside charged micro-droplets, that can accelerate reaction by compared to bulk or flow reaction approaches. Since both the desorption efficiency from the surface and the reaction kinetics can be significantly influenced by the DESI spray solvent flowrate and composition, these parameters are expected to play key roles in the overall performance of the ultrahigh-throughput screening. Syringe pumps are frequently used to deliver the DESI spray. They are robust, but inflexible and slow when it comes to manipulating solvent composition and varying flowrate setpoints. This study addresses the importance of designing a high performance, flexible solvent delivery system that enables more rapid solvent composition and flowrate setpoint changes than the routinely used syringe pumps. Our system utilizes a piezoelectric-based pressure controller and valve system employed with fine-tuned adaptive proportional-integrative-derivative (PID) controller. N-alkylation reactions were used to demonstrate the impact of spray-solvent composition and flowrate on the DESI-MS outcome. In particular, the results showed that ions resulting from solvent mixtures can induce reactions that would be otherwise unobserved when using the corresponding neat solvents. This further signifies the need for a flexible spray-solvent delivery system with fast dynamics in the context of ultra-high throughput DESI-MS analysis.

Development of Validated Methods and Quantification of Curcuminoids and Curcumin Metabolites and Their Pharmacokinetic Study of Oral Administration of Complete Natural Turmeric Formulation (Cureit™) in Human Plasma via UPLC/ESI-Q-TOF-MS Spectrometry.

Specific and sensitive ultra-high performance liquid chromatography-quadrupole time of flight-mass spectroscopy (UPLC-QTOF-MS) methods have been developed for the determination of curcuminoids and curcumin metabolites in human blood plasma. The UPLC-QTOF-MS method used a binary solvent delivery system and the chromatographic separation was performed on a C-18 (2.1 × 50 mm; 1.7 µm) column. Mass spectra were obtained on a Waters Xevo G2S Q-TOF mass spectrometer. The developed methods to characterize the pharmacokinetics of curcuminoids and curcumin metabolites in human blood plasma after an oral administration of bioavailable curcumin—Cureit™—were validated. It was found that the complete turmeric matrix enhances the concentration of tetrahydrocurcumin (THC), hexahydrocurcumin (HHC), octahydrocurcumin (OHC), curcumin-O-glucuronide (COG) and curcumin-O-sulfate (COS) in the blood plasma once the product is administrated.

Development and Validation of HPLC Method for Simultaneous Determination of Ceftriaxone and Cefaclor in Commercial Formulations and Biological Samples

A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of cefaclor and ceftriaxone cephalosporin antibiotic. The developed method has been validated and applied to mixtures of the commercial formulation and spiked human plasma. A mediterranea C18 column (4.6 × 250 mm) was used with isocratic solvent delivery system and UV-visible detector. Different experimental parameters like solvent composition (acetonitrile: methanol: triethyl amine buffer 1:1:2 (v/v), flow rate of mobile phase (0.6 mLmin-1), pH of the buffer (7), and wavelength (260 nm) were optimized for effective separation and esolution of the analyte peaks. The separation was achieved in 6 min with retention times of 4.94 ± 0.056 min and 3.39 ± 0.022 min for cefaclor and ceftriaxone respectively. The linear range for both the studied drugs was found to be 0.5-250 μgmL-1 with r2 of 0.9987 (cefaclor) and 0.9997 (ceftriaxone). The limit of detection (3.3 σ/S) was found to be 2.34 × 10-2 μgmL−1 and 1.70 × 10−2 μgmL-1, respectively, for cefaclor and ceftriaxone. Similarly limit of quantification (10σ/S) was 7.10 × 10−2 μgmL-1 for cefaclor and 5.15 × 10−2 μgmL-1 for ceftriaxone. The chromatographic procedure was applied to commercial formulations and spiked human plasma and the results were compared with literature HPLC method.