Development and Validation of an LC Method for Simultaneous Determination of Ascorbic Acid and Three Phenolic Acids in Sustained Release Tablets at Single Wavelength

A simple, rapid and sensitive column liquid chromatographic method was developed and validated to measure simultaneously the amount of ascorbic acid and phenolic acids at single wavelength (240 nm) in order to assess drug release profiles and drug-excipients compatibility studies for a new sustained release tablet formulation and its subsequent stability studies. A combined isocratic and linear gradient reversed-phase LC method was carried out at 240 nm. Quantification was achieved with reference to the external standards. The linearity for concentrations between 0.042 and 0.150 mg mL^?1 for ascorbic acid, 0.084–0.250 mg mL^?1 for chlorogenic acid, 0.053–0.360 mg mL^?1 for caffeic acid, and 0.016–0.250 mg mL^?1 for ferulic acid (r > 0.99 for all analytes) were established. The recovery of the active ingredients from the samples was at the range of 92.3–102.9%. Intra- and inter-day precisions were less than 2.5%. The limits of detection and quantification were 8 and 24 μg mL^?1 for ascorbic acid, 18 and 54 μg mL^?1 for chlorogenic acid, 37 and 112 μg mL^?1 for caffeic acid, and 11 and 34 μg mL^?1 for ferulic acid. The determination of the four active ingredients was not interfered by the excipients of the products. Samples were stable in the release mediums (37 °C) at least for 12 h.     

Simultaneous Determination of Ibuprofen and Diphenhydramine Citrate in Tablets by Validated LC

A stability-indicating LC method was developed for the simultaneous determination of ibuprofen and diphenhydramine citrate in pharmaceutical dosage forms. The chromatographic separation was achieved on an Inertsil ODS 3V, 150 × 4.6 mm, 5 μm, column. The mobile phase contained a mixture of 50 mM potassium dihydrogen phosphate buffer:acetonitrile:triethylamine:glacial acetic acid (55:45:0.2:0.2, v/v/v/v). This method allowed the determination of 2.85–9.14 mg mL^?1 of ibuprofen and 0.54–1.73 mg mL^?1 of diphenhydramine citrate, in a diluent consisting of pH 7.2, 50 mM potassium dihydrogen phosphate buffer:acetonitrile (40:60, v/v). The flow rate was 1.2 mL min^?1 and the detection wavelength was 260 nm. The limit of detection for ibuprofen and diphenhydramine citrate was 1.72 and 0.54 μg mL^?1 and the limit of quantification was 5.73 and 1.64 μg mL^?1, respectively. This method was validated for accuracy, precision and linearity. The method was also found to be stability indicating.     

Removal, preconcentration and spectrophotometric determination of U(VI) from water samples using modified maghemite nanoparticles

Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples. The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10^?4–1.0 × 10^?2 mol L^?1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on A-MMNPs was 285 mg g^?1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L^?1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration graph was linear in the range 0.04–2.4 ng mL^?1 (1.0 × 10^?10–1.0 × 10^?8 mol L^?1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL^?1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL^?1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.     

A New Flow‐Injection Chemiluminescence Method for the Determination of Acyclovir and Gancyclovir

Abstract

A rapid and sensitive flow‐injection chemiluminescence (FI‐CL) method, which is based on the CL intensity that generated from the redox reaction of Ce(IV)‐rhodamine B in H₂SO₄ medium, for the determination of acyclovir and gancyclovir is described. For acyclovir, the determination range is 3×10^?8 g mL^?1–7×10^?5 g mL^?1, with 1.56×10^?8 g mL^?1 as its determination limit. During 11 repeated measurements for 1×10^?6 g mL^?1 acyclovir, the relative standard deviation was 2.08%. For gancyclovir, the determination range was 5×10^?8 g mL^?1–7×10^?5 g mL^?1, with 2.35×10^?8 g mL^?1 as its determination limit. The relative standard deviation is 2.83% with 11 repeated measurements of 1×10^?6 g mL^?1 gancyclovir. This method can be successfully used to determine the content of acyclovir and gancyclovir in injections, acyclovir in eye drops, and, maybe, also for other ciclovirs.     

A Stability Indicating LC Method for Vardenafil HCl

A simple, sensitive gradient RP-LC assay method has been developed for the quantitative determination of vardenafil HCl in bulk drug and in pharmaceutical dosage forms, used to treat erectile dysfunction. The developed method is also applicable for the related substances determination. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in a gradient mode and quantification was carried out using ultraviolet detection at a flow rate of 1.0 mL min^?1. In the developed LC method the resolution between vardenafil and its four potential impurities was found to be greater than 3.0. Regression analysis shows an r ² value (correlation coefficient) greater than 0.99 for vardenafil and its four impurities. This method was capable of detecting all four impurities of vardenafil at a level of 0.009% with respect to test concentration of 1.0 mg mL^?1 for a 10 μL injection volume. The method has shown good and consistent recoveries for vardenafil (98.4–100.6%) and its four impurities (93.5–106.2%). The test solution was found to be stable in the diluent for 48 h. Mass balance was found close to 99.4%.     

Determination and Pharmacokinetic Study of Methyl Nonyl Ketone in Rat Plasma by GC–MS

A rapid and sensitive method for determination of methyl nonyl ketone in rat plasma was developed based on GC–MS. The analyte and internal standard, propyl p-hydroxybenaoate, were extracted from plasma with methyl tert-butyl ether and then separated by an HP-5MS capillary analytical column (30 m × 0.25 mm, 0.25 µm) and determined by a quadrupole mass spectrometer detector operated under EI ionization and selected ion monitoring mode. Excellent linearity was found to be from 5.0 to 1,000 ng mL^?1 with a lower limit of quantitation of 5.0 ng mL^?1. The accuracy was between 96.0 and 106.3%, and the intra- and inter-day precision and accuracy values were found to be within the assay variability criteria limits according to the FDA guidelines. The developed method was successfully applied to the pharmacokinetic study of methyl nonyl ketone, a typical component in the traditional Chinese medicine Houttuynia cordata injection, in rats after a single oral dose of 100 mg kg^?1 and peritoneal injection dose of 5 mg kg^?1, respectively.     

Optimised isolation of polysaccharides from Lentinula edodes strain NCBI JX915793 using response surface methodology and their antibacterial activities

Mycelial growth in a defined medium by submerged fermentation is a rapid and alternative method for obtaining fungal biomass of consistent quality. Biomass, exopolysaccharides (EPS) and intracellular polysaccharides (IPS) production were optimised by response surface methodology in Lentinula edodes strain LeS (NCBI JX915793). The optimised conditions were pH 5.0, temperature 26°C, incubation period of 25 days and agitation rate of 52 r/min for L. edodes strain LeS. Under the calculated optimal culture conditions, biomass production (5.88 mg mL^? 1), EPS production (0.40 mg mL^? 1) and IPS production (12.45 mg g^? 1) were in agreement with the predicted values for biomass (5.93 mg mL^? 1), EPS (0.55 mg mL^? 1) and IPS production (12.64 mg g^? 1). Crude lentinan exhibited highest antibacterial effects followed by alcoholic, crude and aqueous extracts. The results obtained may be useful for highly effective yield of biomass and bioactive metabolites.     

β-Cyclodextrin-based polyurethane (β-CDPU) polymers as solid media for adsorption and determination of Pb(II) ions in dust and water samples

In this work, β-CD-based polyurethane copolymers (β-CDPU) have been prepared by reacting β-CD with hexamethylene diisocyanate as cross-linked agent in dry DMF. This polymer showed high selectivity for preconcentration of Pb(II) at trace level prior to its flame atomic absorption spectrometric determination. The effect of several parameters such as pH, flow rate of sample, eluent kind and volume was investigated. The adsorption behaviors and mechanisms of Pb(II) on the samples were also studied. The maximum adsorption amount of Pb(II) was 8 mg g^?1 with the preconcentration factor of 250 for Pb(II). The Langmuir isotherm was proved to describe the adsorption data better than the Freundlich isotherm and a pseudo-first-order kinetic model fits the adsorption kinetic processes well. The calibration curve was linear in the range of (3–200 ng mL^?1) with a correlation coefficient of 0.9996. The limit of detection based on three times the standard deviation of the blank was 1.15 ng mL^?1. The relative standard deviations for the determination of 10 and 100 ng mL^?1 of Pb(II) were 3.60 and 0.43 % (n = 10), respectively. The method was successfully applied to the determination of lead in some environmental samples such as Tehran and Bushehr drinking water, river water and dust samples.     

Temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction with following back-extraction for HPLC/UV–Vis determination of 3-indole acetic acid in pea plants

In this work, the ionic liquid (IL)[C₆mim][PF₆] was used as IL-based extractant for dispersive liquid–liquid microextraction, followed by back-extraction and HPLC/UV–Vis determination of 3-indole acetic acid (IAA) in pea plant. The effects of some crucial factors such as chemical structure and volume of IL, pH adjustment, dissolution temperature, extraction time, centrifugation time, and ionic strength of aqueous sample were studied. The linear range of the HPLC method for IAA quantification was 17.5 × 10^?2–36.8 mg L^?1. LOD, LOQ, method recovery, and preconcentration factor values were 0.170 mg L^?1, 0.175 mg L^?1, 98.3, and 40 %, respectively. The RSD for the suggested method was calculated as 0.93 % at 35.04 mg L^?1 of IAA and each IL phase was able to be reused for at least four DLLME/back-extraction cycles. To evaluate the applicability of the suggested method, IAA was determined in pea plant samples.     

Determination of Pantoprazole, Rabeprazole, Esomeprazole, Domperidone and Itopride in Pharmaceutical Products by Reversed Phase Liquid Chromatography Using Single Mobile Phase

A simple, sensitive, and precise high performance liquid chromatographic method for the analysis of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride, with ultraviolet detection at 210 nm, has been developed, validated, and used for the determination of compounds in commercial pharmaceutical products. The compounds were well separated on a Hypersil BDS C18 reversed-phase column by use of a mobile phase consisting of 0.05 M, 4.70 pH, potassium dihydrogen phosphate buffer - acetonitrile (720:280 v/v) at a flow rate of 1.0 mL min^?1. The linearity ranges were 400–4,000 ng mL^?1 for pantoprazole, 200–2,000 ng mL^?1 for rabeprazole, 400–4,000 ng mL^?1 for esomeprazole, 300–3,000 ng mL^?1 for domperidone and 500–5,000 ng mL^?1 for itopride. Limits of detection (LOD) obtained were: pantoprazole 147.51 ng mL^?1, rabeprazole 65.65 ng mL^?1, esomeprazole 131.27 ng mL^?1, domperidone 98.33 ng mL^?1 and itopride 162.35 ng mL^?1. The study showed that reversed-phase liquid chromatography is sensitive and selective for the determination of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride using single mobile phase.     

Development and Validation of a New Analytical Method for the Determination of Related Components and Assay of Ranolazine in Bulk Drug and Pharmaceutical Dosage Forms by LC

A novel liquid chromatographic method has been developed and validated for the determination of ranolazine, its potential four impurities in drug substance and drug products. Efficient chromatographic separation was achieved on a C18 stationary phase (150 × 4.6 mm, 3.0 microns particles) with simple mobile phase combination delivered in gradient mode at a flow rate of 1.0 mL min^?1 at 210 nm. In the developed method, the resolution between ranolazine and its four potential impurities was found to be greater than 2.0. Regression analysis shows an r value (correlation coefficient) greater than 0.999 for ranolazine and for its four impurities. This method was capable to detect all four impurities of ranolazine at a level below 0.004% with respect to test concentration of 1.0 mg mL^?1 for a 10 μL injection volume. The method has shown good, consistent recoveries for ranolazine (98.8–101.1%) and for its four impurities (97.2–100.3). The test solution was found to be stable in the diluent for 48 h. The drug was subjected to stress conditions. The mass balance was found close to 99.5%.     

Derivatization and Determination of MCPA in Soil by GC

A reliable and sensitive method for determination of MCPA in soil by derivatization through p-toluenesulfonic acid and 1,3-dichloro-2-propanol followed by gas chromatographic detection under ECD mode has been established. After treatment with hydrochloric acid, the soil samples were directly extracted without any clean-up with dichloromethane by vortexing. After derivatization and liquid–liquid extraction, the product was subjected to GC analysis. Under optimized conditions, recovery of MCPA reached 87–91%; intra- and inter-day precision values were recorded in the range 3.4–6.4% and 7.4–8.7%, respectively. Excellent linear relationship was observed within 0.1–10 μg mL^?1 (0.005–0.5 mg kg^?1) with linear correlation coefficient (R) of 0.9997. The LOD and LOQ were 0.001 and 0.0026 mg kg^?1, respectively, and the overall sensitivity for detection was found to be in the same range as with the conventional GC-MS technique.     

Determination of Three Nonsteroidal Anti-Inflammatory Drugs in Human Plasma by LC Coupled with Chemiluminescence Detection

A simple and sensitive method was developed for the determination of three nonsteroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen and fenbufen in human plasma. The method involved in column liquid chromatographic separation and chemilumenescence (CL) detection based on the CL reaction of NSAIDs, potassium permanganate (KMnO₄) and sodium sulfite (Na₂SO₃) in sulfuric acid (H₂SO₄) medium. The chromatographic separation was carried out using a reversed-phase C₁₈ column, which allowed the selective determination of the three medicines in the complicated samples. The special features of the CL detector provided lower LOD for determination than that of existing chromatographic alternatives. The results indicated that the linear ranges were 0.01–10.0 μg mL^?1 for ibuprofen, 0.001–1.0 μg mL^?1 for naproxen, and 0.01–10.0 μg mL^?1 for fenbufen. The limits of detection were 0.5 ng mL^?1 for ibuprofen, 0.05 ng mL^?1 for naproxen and 0.5 ng mL^?1 for fenbufen (S/N = 3). All average recoveries were in the range of 90.0–102.3%. Finally, the method had been satisfactorily applied for the determination of ibuprofen, naproxen and fenbufen in human plasma samples.     

Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol^?1 cm^?1 and 0.67 ng mL^?1, respectively. The detection limit of Hg(II) is 1.40×10^?2 ng mL^?1, and Beer's law is valid in the concentration range 0.05–2.40 µg mL^?1. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL^?1 of Hg(II) and 0.065–0.650 µg mL^?1 of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL^?1 of Hg(II) and 0.620 µg mL^?1 of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.     

Colorimetric Determination of Lead Using Gold Nanoparticles

A combined homogeneous assay and colorimetric determination method using gold nanoparticles was developed for rapid determination of lead(II) in contaminated natural waters. The presence of lead(II) in the colloidal gold suspension causes a change in the absorbance of the suspension. An increase in the absorption property at 595 nm is accompanied by a change in the size of the gold nanoparticles. High concentrations of lead cause aggregation of the gold colloids. Colloidal gold nanoparticles were synthesized using tannic acid as the reducing agent; this reagent allowed selective determination of lead in 10 µL of water, with a detection limit of 310 ng mL^?1 with an analysis time of 5 min. The coefficient of variation for lead(II) within the working range of the assay (520 ng mL^?1–13 µg mL^?1) varied from 1.3% to 9.2%. The limit of detection using this method with a sample volume of 50 µL was 60 ng mL^?1. The coefficient of variation for lead over the working range of the determined concentrations (80 ng mL^?1–25 µg mL^?1) varied from 0.2% to 9.3%, while the values for the inter-day assay (n = 8) were less than 10%. The method was employed for the analysis of river, lake, marsh, and spring water; the recovery of lead was determined to be 72.5%–130% for 10 µL of water and 93.6%–114.7% for 50 µL.     

Determination of Gold(III) by Simplified Room-Temperature Ionic Liquid Extraction with Flame Atomic Absorption Spectrometry

A new simplified extraction of gold(III) using a room-temperature ionic liquid prior to determination by flame atomic absorption spectrometry has been developed. The extraction method uses 1-butyl-3-methylimidazolium hexafluorophosphate without a chelating agent. The parameters of the extraction system were investigated in detail. Under the optimized conditions, a linear range of 0.19 to 38.20 µg · mL^?1, a limit of detection of 0.072 µg · mL^?1, an enrichment factor of 10.0, and an extraction capacity of 6.6 mg · g^?1 were obtained. The extraction mechanism and the selectivity of 1-butyl-3-methylimidazolium hexafluorophosphate for gold(III) were also investigated. The method was applied for the determination of gold(III) in water samples with satisfactory results.     

Development of Immunoaffinity Sample-Purification for GC–MS Analysis of Ractopamine in Swine Tissue

A method combining immunoaffinity chromatography with gas chromatography–mass spectrometry (GC–MS) has been established for determination of ractopamine residues in swine liver and urine. After clean-up on an immunoaffinity chromatography column, GC–MS analysis revealed recovery from blank swine liver and urine fortified at 2.5–20 ng g^?1 (ng mL^?1 for urine), respectively, was 68.2–78.6 and 76.2–83.1%. The limits of detection and quantification were 0.5 ng g^?1 (or ng mL^?1) and 2.0 ng g^?1 (or ng mL^?1), respectively. The procedure was used for analysis of ractopamine residues in samples of swine liver and urine in which the levels were unknown. The amounts detected were 9–216 ng g^?1 (ng mL^?1).     

Persistence and dissipation of fluopicolide and propamocarb on cabbage and soil under semi-arid climatic conditions

Persistence and dissipation of fluopicolide and propamocarb were studied on cabbage and soil as per good agricultural practices over a period of 2 years. A modified QuEChERS analytical method in conjunction with gas chromatography (GC) and GC–mass spectrometry was used for analysis of fluopicolide and its metabolite, 2,6-dichlorobenzamide, and propamocarb in cabbage and soil. The results of the method validation were satisfactory with recoveries within 74.5–100.81% and relative standard deviations 4.8–13.9% (n = 6). The limit of detection (LOD) and limit of quantification (LOQ) of both fluopicolide and 2,6-dichlorobenzamide were 0.003 µg mL^?1 and 0.01 mg kg^?1, respectively. The LOD and LOQ of propamocarb were 0.03 µg mL^?1 and 0.1 mg kg^?1, respectively. During 2013, the initial residue deposits of fluopicolide on cabbage were 0.60 and 1.48 mg kg^?1 from treatments at the standard and double doses of 100 and 200 g a.i. ha^?1 which dissipated with the half-life of 3.4 and 3.7 days. During 2014, the residues were 0.49 and 1.13 mg kg^?1 which dissipated with the half-life of 4.2 and 5.1 days. Propamocarb residues on cabbage were 5.36 and 12.58 mg kg^?1 in the first study (2013) and 4.85 and 10.26 mg kg^?1 in the second study (2014) from treatments at the standard and double doses of 1000 and 2000 g a.i. ha^?1, respectively. The residues dissipated with the half-life of 4–5.5 days. The preharvest interval, the time required for fluopicolide + propamocarb residues to dissipate below the maximum residue limits (notified by EU) at the standard dose, was 11.8 and 14 days during 2013 and 2014. Residue of 2,6-dichlorobenzamide was always <LOQ in cabbage. Residues of fluopicolide, 2,6-dichlorobenzamide and propamocarb were <LOQ in field soil at harvest.     

Capillary Electrophoresis Method for the Chiral Purity Determination of Pregabalin Derivatized with Dansyl Chloride

A capillary electrophoresis method for the determination of the chiral purity of pregabalin upon derivatization with dansyl chloride was developed using design of experiment methodologies. A D-optimal design was used for the identification of the critical process parameters, while a central composite face centered design and Monte Carlo simulations were employed for defining the design space of the method. Final working conditions consisted of a background electrolyte composed of a 100 mM sodium phosphate buffer, pH 2.5, containing 40 mg mL^?1 heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, a separation voltage of 15 kV and a capillary temperature of 25 °C. The analyses were carried out in a 40/50.2 cm fused-silica capillary with an inner diameter of 50 µm. Upon testing the robustness using a Plackett–Burman design, the method was validated according to the International Council on Harmonization guideline Q2(R1). The method allowed the detection of the (R)-enantiomer at the 0.015% level with a limit of quantitation at the 0.05% level with regard to a sample containing 1.59 mg mL^?1 pregabalin. The method was subsequently applied to the determination of the stereochemical purity of the drug in commercial capsules.     

UPLC-PDA Analysis for Simultaneous Quantification of Four Active Compounds in Crude and Processed Rhizome of Polygonum multiflorum Thunb

A novel, rapid and specific ultra performance liquid chromatography-photo diode array detection method was developed for the simultaneous determination of 2,3,5,4′-tetrahydroxystilbene-2-O-β-d-glucoside (TSG), emodin-8-O-β-d-glucoside (EMG), emodin (EM) and physcion (PS). The chromatographic separation was performed on an Acquity BEH C₁₈ column (100 × 2.1 mm i.d., 1.7 μm). The mobile phase was a mixture of 0.3% acetic acid–water and 0.3% acetic acid–acetonitrile employing gradient elution at the flow rate of 0.4 mL min^?1. The four compounds behaved linearly in the concentration range between 60.80–3040.00 μg mL^?1 (TSG), 0.50–25.00 μg mL^?1 (EMG), 2.16–108.00 μg mL^?1 (EM) and 1.56–78.00 μg mL^?1 (PS), respectively with correlation coefficients >0.999. The precision of the method were below 5% RSD. Recoveries of the four compounds ranged from 95.71 to 102.97%, with RSD values less than 2%.