HPTLC Determination of Cefpodoxime Proxetil in Formulations

An HPTLC method has been developed that coelutes both the isomers of cefpodoxime proxetil (CFP). CFP was chromatographed on a silica gel 60 F₂₅₄ TLC plate using toluene:acetonitrile (6:4) as a mobile phase and was quantified at 234 nm. The method was validated with respect to linearity, accuracy, precision and specificity. The limit of detection and limit of quantification for CFP were found to be 0.150 and 0.4 μg spot⁻¹, respectively. The proposed method was successfully used to determine the amount of CFP present in the marketed tablets and self-nanoemulsifying systems.

     

Composite electrocatalyst Mo<Subscript>x</Subscript>W<Subscript>1-x</Subscript>S<Subscript>2</Subscript> nanosheets on carbon fiber paper for highly efficient hydrogen evolution reaction

Molybdenum disulfide (MoS₂) or tungsten disulfide (WS₂), as a promising catalyst, is widely investigated for hydrogen evolution reaction (HER). In this work, a composite electrocatalysts Mo_xW_1-xS₂ is successfully decorated on carbon fiber paper (CFP) through a facile hydrothermal method. The three-dimensional porous CFP can enable the diffusion and penetration of electrolyte. Comparing with MoS₂ and WS₂ catalyst, the composite electrocatalyst Mo_xW_1-xS₂ nanosheets can expose the large number of electrochemically active sites. Hence, the as-prepared Mo_xW_1-xS₂/CFP (3:1) exhibit the outstanding HER catalytic activity with the small Tafel slope of 68 mV dec^?1 and the low overpotential of ??178.4?±?0.5 mV at a current density of 10 mA cm^?2. Chronoamperometric current test for 18 h confirm the long-term stability of the composite electrocatalyst.     

Simultaneous Determination of Abacavir,Efavirenz and Valganciclovir in Human Serum Samples by Isocratic HPLC-DAD Detection

A rapid, sensitive, and specific reverse phase high performance liquid chromatography with diode array detection procedure for the simultaneous determination of abacavir, efavirenz and valganciclovir in spiked human serum is described. Separation was performed on a 5 μm Waters Spherisorb column (250 × 4.6 mm ID) with acetonitrile: methanol:KH₂PO₄ (at pH 5.00) (40:20:40 v/v/v) isocratic elution at a flow rate of 1.0 mL min⁻¹. Calibration curves were constructed in the range of 50–30,000 ng mL⁻¹ for abacavir and efavirenz, and 10–30,000 ngmL⁻¹ for valganciclovir in serum samples. The limit of detection and limit of quantification concentrations of the HPLC method were 3.80 and 12.68 ng mL⁻¹ for abacavir, 2.61 and 8.69 ng mL⁻¹ for efavirenz, 1.30 and 4.32 ng mL⁻¹ for valganciclovir. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in human serum.

     

Development and Validation of an RP-HPLC Method for Determination of Valganciclovir in Human Serum and Tablets

This paper describes the validation of an isocratic high-performance liquid chromatographic method for the assay of valganciclovir in raw materials, tablets and human serum samples. Valganciclovir and fluvastatin (internal standard) were well separated using a reversed phase column and a mobile phase consisting of a mixture of acetonitrile:methanol:KH₂PO₄ (0.02 M) (40:20:40; v/v/v) (at pH 5.0). The mobile phase was pumped at 1.0 mL min⁻¹ flow rate and valganciclovir was detected by diode-array detection at 255 nm. The retention times for valganciclovir and fluvastatin were 3.41 and 5.60 min, respectively. A linear response (r > 0.999) was observed in the range of 10–30,000 ng mL⁻¹ in mobile phase and serum. The limit of detection and limit of quantification were found as 2.95 and 9.82 ng mL⁻¹ in mobile phase and 1.73 and 5.77 ng mL⁻¹ in human serum samples, respectively. Validation parameters as precision, accuracy, selectivity, reproducibility and system suitability tests were also determined. The method can be used for valganciclovir assay of tablets and human serum samples as the method separates valganciclovir from tablet excipients and endogenous substances.

     

LC Analysis and Pharmacokinetic Study of Pachymic Acid After Intravenous Administration to Rats

A simple and sensitive high-performance liquid chromatographic method with UV detection was developed and validated to investigate the concentration of pachymic acid (PA) in rat plasma. The sample preparation was a liquid-liquid extraction and chromatographic separation was achieved with a Dikma Diamonsil^TM C₁₈ column (250 × 4.6 mm I.D.) with a C₁₈ guard column (8 × 4 mm I.D.) using a mobile phase consisting of MeOH-MeCN-aq. 0.45% H₃PO₄ (45:40:22) at a flow rate of 1.0 mL min^?1. The UV detection was at 210 nm. Standard curves were linear (r = 0.9998) in plasma over the concentration range of 0.5–50 μg mL^?1 and had acceptable accuracy and precision. Intra- and inter-day precisions expressed as the relative standard deviation (RSD) were 0.26–1.60% and 1.24–2.31%. The lower limit of quantification and lower limit of detection were 0.45 and 0.17 μg mL^?1. The method has been used successfully to study the pharmacokinetics of PA. After a dose of 30 mg kg^?1 by intravenous administration, the main pharmacokinetic parameters t _1/2, AUC_0-∞, CL, V_ss and MRT_0-∞ were 8.79 ± 6.80 h, 18.90 ± 9.39 μg h mL^?1, 0.53 ± 0.28 L h^?1, 5.60 ± 4.60 L and 12.58 ± 9.95 h, respectively.     

Development and Validation of Stability Indicating LC Method to Quantify Captopril in Tablets of Controlled Release

An accurate, simple, reproducible, and sensitive liquid chromatographic method was developed and validated for the captopril determination in controlled release tablets. The analyses were performed at room temperature on a reversed-phase Phenomenex Luna C₁₈ column (250 mm × 4.6 mm). The mobile phase was composed of water:methanol (45:55; v/v) pH 2.5, and it was eluted isocratically at a 1.0 mL min⁻¹ flow rate. The method was validated in terms of specificity, linearity, quantification limit, detection limit, accuracy, precision and robustness. The response was linear in the range 0.3–1.5 mg mL⁻¹ (r ² = 0.9983). The relative standard deviation values for inter-and intra-day precision were 0.77% and 0.50%, respectively. Recoveries ranged between 97.7 and 99.1%. The method was successfully applied for the determination of captopril in the developed formulations.

     

Affinity Adsorption Solid Substrate‐Room Temperature Phosphorimetry for the Determination of Alkaline Phosphatase

Abstract

In the presence of Pb(Ac)₂, the silicon dioxide nanoparticle containing rhodamine 6G (R‐SiO₂) can emit strong and stable solid substrate‐room temperature phosphorescence (SS‐RTP) signal on the surface of acetyl cellulose membrane (ACM) at λ_ex/λ_em=482/649 nm. It was found in the research that specific affinity adsorption reaction between triticum vulgare lectin (WGA) (which was labeled with luminescent silicon dioxide nanoparticle) and alkaline phosphatase (AP) can be carried out on the surface of ACM. The product of the reaction can emit stronger SS‐RTP signal. A new method of SS‐RTP for the determination of AP was established, based on an affinity adsorption reaction between AP and WGA labeled with nanoparticles containing rhodanime 6G luminescent molecules. The linear range of this WGA‐AP‐WGA‐R‐SiO₂ method is 1.00–360.00 ag AP spot^?1 (sample volume: 0.40 µL spot^?1, corresponding concentration range: 2.50–900.00 fg mL^?1). The regression equation of working curve is ΔIp=16.24+0.8856 m_AP (ag spot^?1), r=0.9993. Detection limit of this method calculated by 3S_b/k is 0.14 ag spot^?1. After 11‐fold replicate measurements, RSD are 3.9% and 3.1% for the systems containing 1.00 and 360.00 ag AP spot^?1, respectively. Compared with R‐SiO₂‐WGA‐AP method (detection limit: 0.45 ag spot^?1, corresponding concentration range: 2.00–320.00 ag spot^?1), the sensitivity of WGA‐AP‐WGA‐R‐SiO₂ method was obviously improved and the linear range was wider. The sensitivity, accuracy, and precision of this method are high. It has been successfully applied to determine AP in human serum.     

Improving the radiochemical purity determination of 123I-labeled metaiodobenzylguanidine

The HPLC method originally applied at the Nuclear Engineering Institute (IEN) for the radiochemical purity determination of ¹²³iodine labeled m-iodobenzylguanidine (¹²³I-mIBG) takes 18.5 min. The final product release also depends on this result, and to facilitate this stage, we aimed to decrease this analysis time. We also intended to use fewer toxic compounds, if feasible. The optimization approach used herein was a combination of factorial and mixture designs to study simultaneously the selected variables. Analysis time, resolution and chromatograms aspect were the measured responses. The qualitative analysis of these responses provided the best chromatographic separation conditions that were 52 mM KH₂PO₄ in a solution of ethanol and water (1:1), applying a flow rate of 0.50 mL min^?1 and C18 column (4.6 × 250 mm, 5 μm). These optimum conditions not only decreased the analysis time in 61 %, but also allowed the reduction of mobile phase toxicity. To assure reliable data, method validation was performed for these conditions. The method has proved its specificity, the detection limit found was 3.70 × 10^?4 MBq mL^?1 and the quantification limit has corresponded to 1.11 × 10^?3 MBq mL^?1. Repeatability and intermediate precision has not exceeded 3 and 5 %, respectively, and the accuracy has matched the interval of 95–105 %. This new method has been routinely applied in the radiochemical purity determination of ¹²³I-mIBG at IEN.     

LC-UV Column-Switching for Quantitation of Vitamin K1 in Infant Formula

This study was undertaken in order to develop an analytical method for vitamin K₁ in infant formula. The content of vitamin K₁ was investigated by using a column-switching LC-UV method. A Certified Reference Material sample of infant formula containing 0.94 ± 0.04 mg kg^?1 of vitamin K₁ was extracted with hexane followed by enzymatic digestion of fat and precipitation of the fatty acids. The linearity of this method was calculated using five consecutive standard curves, and the coefficient of determination (r ²) was found to be 0.9995. The limit of detection (LOD) and the limit of quantitation (LOQ) was 3.31 and 11.12 μg L^?1, respectively. The accuracy of intra- and inter-day measurements was in the range from 96.67 to 108.67%, and the precision of intra- and inter-day measurements was less than 5.13%. The recoveries were 109.27 ± 5.92%, and the recoveries of inter-laboratory results were in the range from 97.59 ± 1.29 to 109.27 ± 5.92%. The newly developed method uses the optimum conditions required to determine the content of vitamin K₁ in infant formula.     

Optimization,Validation and Application of a Capillary Zone Electrophoresis Method for the Assay of Sparfloxacin in Pharmaceutical Formulation

Abstract

A capillary zone electrophoresis (CZE) method has been developed for the determination of the antibiotic sparfloxacin in tablets. The CZE separation was performed using 75 µm×35 cm fused-silica capillary under the following conditions: 25°C; applied voltage, 12 kV; 25 mM H₃PO₄-NaOH running buffer (pH 8.5). The detection wavelength was 254 nm. Flumequine was used as internal standard (IS). The method was suitably validated with respect to linearity, limit of detection and quantification, accuracy, precision, specificity, and robustness. The calibration was linear from 10 to 60 µg mL^?1 and the limit of detection and quantification were 5.38 and 9.46 µg mL^?1, respectively. Recoveries ranging from 95.68%–102.4% were obtained in the determination of sparfloxacin that were spiked to placebos. Excipients in the commercial tablets and degraded products from different stress conditions did not interfere in the assay. The method was successfully applied to the determination of sparfloxacin in pharmaceutical tablets.     

LC–MS Method for the Sensitive Determination of Metoclopramide: Application to Rabbit Plasma, Gel Formulations and Pharmaceuticals

To support real biological sample application, a simple, selective and rapid LC–MS method has been developed and validated for the sensitive determination of metoclopramide in rabbit blood, ex vivo permeation studies and pharmaceutical dosage form. LC–MS analysis was performed isocratically on a Zorbax SB-C₁₈ column with a mobile phase consisting of methanol:ammonium acetate buffer (pH 3.0) 75:25 (v/v) at a flow rate of 0.70 mL min^?1. The outlet of the column was connected to a single quadrupole mass spectrometer with positive mass spectrometric detection. Ions were detected in the positive multiple reaction monitoring mode. The assay was linear over the concentration range of 1.25–200 pg μL^?1 with a limit of detection of 0.077 pg μL^?1 for standard solutions and 2.5–200 pg μL^?1 with a limit of detection of 0.42 pg μL^?1 for serum samples. The method is applicable, covering a variety of pharmaceutical and biological studies. Metoclopramide was extracted from rabbit blood by liquid–liquid extraction using ether as the extraction solvent. The reproducibility of the method was found to be between 0.96 and 1.98 % (RSD) values. The proposed method has been extensively validated for the determination of metoclopramide in all working media. The sample preparations, flow rate and run time of the analytical systems are not time consuming. Moreover, for the stability of metoclopramide, the effect of temperature, UV light, H₂O₂, HCl and NaOH were also investigated.     

Sensitive detection of sulfanilamide by redox process electroanalysis of oxidation products formed in situ on glassy carbon electrode

This paper reported a simple method for sulfanilamide determination by redox process electroanalysis of oxidation products (SFDox) formed in situ on glassy carbon electrode. The CV experiments showed a reversible process after applied E _acc = + 1.06 V and t _acc = 1 s, in 0.1 mol L^?1 BRBS (pH = 2.0) at 50 mV s^?1. Different voltammetric scan rates (from 10 to 450 mV s^?1) suggested that the redox peaks of SFDox on the glassy carbon electrode (GCE) is an adsorption-controlled process. Square-wave voltammetry (SWV) method optimized conditions showed a linear response to SFD from 3.00 to 250.0 μmol L^?1 (R = 0.998) with a limit of detection of 0.638 μmol L^?1 and limit of quantification of 2.0 μmol L^?1. The developed the SWV method was successfully used in the determination of SFD pharmaceutical formulation and human serum. The SFD quantification results in pharmaceutical obtained by SWV-GCE were comparable to those found by official analytical protocols.     

Development and Validation of a RP-HPLC–PDA Method for Determination of Curcuminoids in Microemulsions

A sensitive, specific and rapid high-performance liquid chromatography method was developed in an effort to quantify extremely low curcuminoid levels for the future transdermal experiments where the curcuminoids are incorporated with excipients such as microemulsion, liposomes, and micelles. The chromatographic separation was performed using a Symmetry^® C₁₈, 250 × 4.6 mm, 5-μm column, with a mobile phase composed of 5 mM acetonitrile:phosphoric acid (45:55, v/v) at a flow rate of 1.0 mL min⁻¹, it was sensitive with a low limit of quantitation for curcuminoids (0.626 ng mL⁻¹ for curcumin) and good linearity (r ² ≥ 0.999) over the range 1–100 ng mL⁻¹. All the validation data, such as accuracy and precision, were within the required limits from the ICH guideline. The assay method was successfully applied during forced degradation of curcuminoid solutions. The method retained its accuracy and precision when the standard addition technique was applied.

     

Effervescence-assisted dispersive liquid-liquid microextraction based on deep eutectic solvent for preconcentration and FAAS determination of copper in aqueous samples

A new effervescence-assisted dispersive liquid-liquid microextraction, EA-DLLME, technique was developed for preconcentration and flame atomic absorption spectrometric determination of copper in aqueous samples. Effervescence assistance and DES combination for metal ion extraction was used for the first time. In the presented study, six different effervescence powders were examined to achieve maximum extraction efficiency. In addition, 1,5 diphenyl carbazide was used as complexing agent and DES prepared by mixing choline chloride and phenol was used as extraction solvent. The effect of several parameters such as pH, concentration of complexing agent, composition and volume of DES, amount of THF, composition and amount of effervescent agent were examined. Performed experiments showed that optimum pH was 6.0, the best effervesce powder composition was NaH₂PO₄:Na₂CO₃ with 2 × 10^?3:1 × 10^?3 molar ratio and the amount of effervesce powder was 0.4 g. Under optimum conditions enhancement factor, limit of detection and limit of quantification were calculated as 78, 2.9 and 9.7 μg L^?1, respectively. In addition, to prove precision of the method intra-day relative standard deviations were calculated for 10 and 50 μg L^?1 Cu²⁺ concentrations and found as 2.1% and 1.3%, respectively. The proposed method showed good linearity within the range of 10.0–100 μg L^?1. Finally, proposed method was successfully applied to determination of copper traces in aqueous samples.     

LC–ESI–MS Determination of Imperatorin in Rat Plasma After Oral Administration and Total Furocoumarins of Radix Angelica dahuricae and its Application to a Pharmacokinetic Study

A simple, rapid, sensitive and reliable liquid chromatography–electrospray ionization mass spectrometry method for the quantification of imperatorin in rat plasma after oral administration and total furocoumarins of Radix Angelica dahuricae has been established. The plasma samples were deproteinized by adding internal standard (IS) osthole solution, which was prepared by acetonitrile. The analysis was performed on a Shim-pack C₁₈ column (150 × 2.0 mm i.d., 5 μm) using acetonitrile and 0.5% formic acid solution (70:30, v/v) as a mobile phase. The detection was performed on a quadrupole mass spectrometer detector with an ESI interface operated in the selected ion monitoring mode. The linear quantification range of the method was 2–4000 ng mL^?1 in rat plasma with a correlation coefficient greater than 0.99, the limit of detection (LOD) was 0.5 ng mL^?1 and the lower limit of quantification (LLOQ) 2 ng mL^?1. The intra- and inter-day relative standard deviations (RSD) were less than 2.5 and 3.5%, respectively. The recoveries were above 90%. The validated method was successfully applied to a pharmacokinetic study of imperatorin in rats after oral administration and total furocoumarins of Radix Angelica dahuricae.     

HPLC Method for Monitoring of Degradation Products in Picoplatin Stability Study

An analytical method combining high-performance liquid chromatography (HPLC) with UV detection was developed for an easy and rapid assay determination of the anticancer drug picoplatin (=cis-[Pt(NH₃)(2-methylpyridine)Cl₂]) and its degradation products. An ion exchanger was used as the stationary phase with an aqueous solution of NaH₂PO₄ with pH adjusted to 3.0 with H₃PO₄ as the mobile phase. The calibration curve was linear within the concentration range of 0.10–0.50 g L^?1 (R ² ≥ 0.998). The limit of detection was 0.05 g L^?1 and limit of quantification was 0.09 g L^?1. The developed method was characterized with a high precision (≤6.0%, determined as RSD), an acceptable accuracy (the values of recovery were from intervals 98–103%). The developed method was used for assessing the stability of picoplatin during a stability study.     

Chemiluminescent Determination of Vitamin B12 Using Charge Coupled Device (CCD)

A method was developed for the determination of vitamin B₁₂ based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B₁₂ was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction.

The optima experimental conditions were established: 8.0 m mol L^?1 luminol in a 0.075 mol L^?1 carbonate buffer (pH 10.0) and 0.15 mol L^?1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s^?1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L^?1 (r² = 0.9990), with a detection limit of 0.42 µ g L^?1. The proposed method was successfully applied to the determination of vitamin B₁₂ in pharmaceuticals.     

Development and Validation of a RP-HPLC–PDA Method for Determination of Curcuminoids in Microemulsions

A sensitive, specific and rapid high-performance liquid chromatography method was developed in an effort to quantify extremely low curcuminoid levels for the future transdermal experiments where the curcuminoids are incorporated with excipients such as microemulsion, liposomes, and micelles. The chromatographic separation was performed using a Symmetry^® C₁₈, 250 × 4.6 mm, 5-μm column, with a mobile phase composed of 5 mM acetonitrile:phosphoric acid (45:55, v/v) at a flow rate of 1.0 mL min^?1, it was sensitive with a low limit of quantitation for curcuminoids (0.626 ng mL^?1 for curcumin) and good linearity (r ² ≥ 0.999) over the range 1–100 ng mL^?1. All the validation data, such as accuracy and precision, were within the required limits from the ICH guideline. The assay method was successfully applied during forced degradation of curcuminoid solutions. The method retained its accuracy and precision when the standard addition technique was applied.     

Rapid and Sensitive RP-LC Method for the Quantification and Pharmacokinetic Study of p-Hydroxyphenethyl Anisate in Rat Plasma

A rapid, sensitive and specific reversed-phase liquid chromatographic method was developed and validated for the quantification of p-hydroxyphenethyl anisate (HPA), which is one of the main constituents of Notopterygium Radix (underground parts of Notopterygium incisum and N. forbesii), in rat plasma, and study its pharmacokinetics after the intravenous administration of 40 mg kg^?1 HPA to rats. The method involves a plasma clear-up step using liquid–liquid extraction by ethyl acetate, followed by RP-LC separation and detection. Separation of HPA was performed on an analytical Diamonsil ODS C₁₈ column equipped with a Dikma ODS C₁₈ EasyGuard column using a mobile phase consisting of MeOH–H₂O (75:25, v/v) at a flow-rate of 1.0 mL min^?1. The UV detection was performed at a wavelength of 256 nm. The linear calibration curves were obtained in the concentration range of 0.05–5.0 μg mL^?1 (r = 0.9992, n = 5) in rat plasma with the lower limit of detection of 0.01 μg mL^?1 and the lower limit of quantification of 0.04 μg mL^?1, and the extraction recovery of HPA was calculated to be the range of 82.01–86.66%. The intra- and inter-day precisions in terms of % relative standard deviation were lower than 2.33 and 3.99% in rat plasma, respectively, with accuracies ranging from 91.22 to 110.5%. The developed method was suitable for the determination and pharmacokinetic study of HPA in rat plasma.     

Simultaneous Estimation of Atorvastatin Calcium, Ramipril and Aspirin in Capsule Dosage Form by RP-LC

A simple, sensitive, precise and accurate reversed phase liquid chromatographic method has been developed for the simultaneous estimation of atorvastatin (AT) calcium, ramipril (RA) and aspirin (AS) from capsule dosage form. The method was developed using a Phenomenex Luna C₁₈ (250 mm, 4.6 mm i.d., 5 µm) column with a mobile phase consisting of 0.1%, orthophosphoric acid buffer:acetonitrile:methanol (45:50:5 v/v/v), pH 3.3, at a flow rate of 1 mL min^?1. Detection was carried out with ultra-violet detection at 210 nm. The retention times were about 12.19, 2.35, and 3.95 min for AT calcium, RA and AS, respectively. The developed method was validated for linearity, accuracy, precision, limit of detection, limit of quantitation and robustness. The linearity ranges were 1–6 µg mL^?1 for AT calcium, 0.5–3 µg mL^?1 for RA and 7.5–45 µg mL^?1 for AS with mean recoveries of 100.59 ± 0.68, 100.62 ± 0.83 and 100.49 ± 0.73% for AT calcium, RA and AS, respectively. Limit of detection obtained were 29.85 ng mL^?1 for AT calcium, 4.71 ng mL^?1 for RA and 85.13 ng mL^?1 for AS. Impurity of salicylic acid was found in capsule dosage form at the retention time of about 4.84 min. The proposed method can be used for the estimation of these drugs in combined dosage forms.