Simultaneous Determination of Ceftriaxone Sodium and Non Steroidal Anti‐Inflammatory Drugs in Pharmaceutical Formulations and Human Serum by RP‐HPLC

An accurate, sensitive and least time consuming reverse phase high performance liquid chromatographic (RP‐HPLC) method for the estimation of ceftriaxone in the presence of non steroidal anti‐inflammatory drugs in formulation and human serum has been developed and validated. Chromatographic separation was conducted on prepacked Purospher Star, C18 (5 μm, 250 × 4.6 mm) column at room temperature using methanol:water:acetonitrile (80:15:5 v/v/v) as a mobile phase, pH adjusted at 2.8 with ortho‐phosphoric acid and at a flow rate of 1.0 mL/minute, while UV detection was performed at 270 nm. The results obtained showed a good agreement with the declared content. The method shows good linearity in the range of 2.5‐25 μg/mL ceftriaxone serum concentrations with a correlation coefficient 0.999 (inter‐ and intra‐day RSD < 2.0%). The limit of detection and quantification for ceftriaxone and NSAID's in pharmaceutical formulation and serum were in the range 0.51‐1.54 μg/mL. Analytical recovery was >98.1%. The proposed method may be used for the quantitative analysis of commonly administered non steroidal anti‐inflammatory drugs i.e. tiaprofenic acid, naproxen sodium, flurbiprofen, diclofenac acid and mefenamic acid alone or in combination with ceftriaxone from raw materials, dosage formulations and in serum. The established HPLC method is rapid, accurate and selective, because of its sensitivity and reproducibility.     

Design and Synthesis of ZnII‐Coordination Polymers Anchored with NSAIDs: Metallovesicle Formation and Multi‐drug Delivery

A series of coordination polymers synthesized from a bis‐pyridyl linker, namely 4,4′‐azopyridine ( L ), selected non‐steroidal‐anti‐inflammatory drugs (NSAIDs), namely diclofenac ( Dic ), ibuprofen ( Ibu ), flurbiprofen ( Flu ), mefenamic acid ( Mefe ), and naproxen ( Nap ), and Zn(NO₃)₂ were characterized by single crystal X‐ray diffraction. One of the coordination polymers, namely CP3 derived from Flu , was able to form metallovesicles in DMSO, DMSO/H₂O and DMSO/DMEM (biological media) as revealed by TEM, AFM and DLS. Metallovesicle formation by CP3 was further supported by loading a fluorescent dye, namely calcein, as well as an anti‐cancer drug, doxorubicin hydrochloride ( DOX ), as revealed by UV‐vis and emission spectra, and fluorescence microscopy. DOX ‐loaded metallovesicles of CP3 ( DOX@CP3‐vesicle ) could be delivered in vitro to a highly aggressive human breast cancer cell line, namely MDA‐MB‐231, as revealed by MTT and cell migration assays, and also cell imaging performed under laser scanning confocal microscope (LSCM). Thus, a proof of concept for developing a multi‐drug delivery system derived from a metallovesicle for delivering an anti‐cancer drug to cancer cells is demonstrated for the first time.     

Liquid Chromatographic Determination of NSAIDs in Urine After Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplets

An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL⁻¹, with coefficients of determination (r ²) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL⁻¹ with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL⁻¹, respectively.

     

An LC–MS/MS method for the quantification of diclofenac sodium in dairy cow plasma and its application in pharmacokinetics studies

An LC–MS/MS method with internal standard tolfenamic acid for determining diclofenac sodium (DCF) in dairy cow plasma was developed and validated. Samples were processed with protein precipitation by cold formic acid–acetonitrile. Determination of DCF was performed using LC–ESI⁺–MS/MS with the matrix‐matched calibration curve. The results showed that the method was sensitive (LOD 2 ng mL^?1, LOQ 5 ng mL^?1), accurate (97.60 ± 5.64%), precise (<10%) and linear in the range of 5–10,000 ng mL^?1. A single intravenous (i.v.) or intramuscular (i.m.) administration of 5% diclofenac sodium injection at a dose of 2.2 mg kg^?1 was performed in six healthy dairy cows according to a two‐period crossover design. The main pharmacokinetic (PK) parameters after a single i.v. administration were as follows: t_1/2β, 4.52 ± 1.71 h; AUC, 77.79 ± 16.76 h μg mL^?1; mean residence time, 5.16 ± 1.11 h. The main PK parameters after a single i.m. administration were as follows: T_max, 2.38 ± 1.19 h; C_max, 7.46 ± 1.85 μg mL^?1; t_1/2β, 9.46 ± 2.86 h; AUC 67.57 ± 13.07 h μg mL^?1. The absolute bioavailability was 87.37 ± 5.96%. The results showed that the diclofenac sodium injection had PK characteristics of rapid absorption and slow elimination, and high peak concentration and bioavailability in dairy cows, and that the recommended clinical dosage of diclofenac sodium injection is 2.2 mg kg^?1.     

High-performance Liquid Chromatographic Analysis of Pioglitazone,Gliquidone,Rosuvastatin and Simvastatin in Formulations and Human Serum

Co‐administration of HMG‐CoA reductase with antidiabetic drugs is most common since antidiabetic drugs are mostly prescribed for long term therapy. In the present paper, we describe the simultaneous determination of antidiabetic (pioglitazone hydrochloride and gliquidone) in presence of statins (rosvastatin and simvastatin) in formulations and in human serum using RP‐HPLC technique. The serum samples were subjected to protein precipitation with acetonitrile prior to an HPLC analysis. At a flow rate of 1 mL·min⁻¹ isocratic elution was employed, using mobile phase consisting of methanol/water (90:10, V:V), pH 3.50 with phosphoric acid and absorbance was recorded at 235 nm. The assay was reproducible, linear (concentration range of 5–50 μg·mL⁻¹) and accurate. The LOD and LOQ values were 1.32, 0.28, 0.05 and 0.57 μg·mL⁻¹ and 4.39, 0.93, 0.16 and 1.90 μg·mL⁻¹ for pioglitazone hydrochloride, gliquidone, rosvastatin and simvastatin, respectively. There were no interfering peaks due to the excipients present in the pharmaceutical tablet and serum. Thus, the proposed method is simple and suitable for the analysis of active ingredient in tablet form and human serum.     

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.

     

Relative tissue distribution and excretion studies of gastrodin and parishin from powder and extract of Gastrodiae Rhizoma in rat by UHPLC‐ESI‐MS/MS

New research has indicated that Gastrodiae Rhizome (GR) has potential anti‐diabetic and anti‐asthmatic effects in mouse models. On the basis of our previous study of the relative bioavailability of gastrodin (GAS) and parishin (PA) from extract and powder of GR, we performed further research on the tissue distribution and excretion of the two analytes. A reliable bioanalytical method for the quantification of GAS and PA in rat tissues and excretion is required. Chromatographic separation was carried out on a gradient mobile phase of acetonitrile–water with 0.1% formic acid. Calibration curves (1/x ² weighted) offered satisfactory linearity (r ² > 0.9835) within 100–3000 ng mL⁻¹ for GAS and (r ² > 0.9862) within 10–1000 ng mL⁻¹ for PA. The relative standard deviations of the intra‐day and inter‐day precision were all <14.98%, whilst the relative errors of the intra‐day and inter‐day accuracy were all within ±14.71%. The matrix effect and recovery values were satisfactory in all of the biological matrices examination. The data of relative differences in tissue distribution and excretion of GAS and PA from powder and extract of GR indicated that higher bioavailabilities for GAS and PA were obtained when a dosage of 4 g kg⁻¹ GR powder was used.     

Simple and Sensitive High-Performance Liquid Chromatographic Method for Determination of Transdermally Applied Flurbiprofen in Rat Plasma and Excised Skin Samples

A simple reversed-phase HPLC method has been developed for determination of flurbiprofen in rat plasma, excised skin extract, and transdermal patch formulations. The mobile phase was methanol–1% (v/v) phosphoric acid in water, 80:20 (v/v), at a flow rate of 0.5 mL min^-1; ibuprofen was used as internal standard. Flurbiprofen and ibuprofen was detected by UV absorption at 254 nm and 220 nm, respectively. The limit of quantitation was 0.1 µg mL^-1. The response was linearly dependent on concentration in the range 0.1–10 µg mL^-1, and accuracy and reproducibility were good. At these concentrations intraday and interday assay variability were below 8%. Recovery of flurbiprofen was greater than 94% over the linear range of calibration plot.     

High Sensitive Detection of Prostate Specific Antigen by Using Ferrocene Cored Asymmetric PAMAM Dendrimer Interface Screen Printed Electrodes

In this study, electrochemical immunosensors were developed for the detection of prostate specific antigen (PSA) using ferrocene (Fc) and polyamidoamine dendrimer (PAMAM) constructs. The biosensor fabrication was designed by modifying the screen‐printed gold electrode (Au) with ferrocene cored dendrimers (FcPAMAM) synthesized in three different generations. The self‐assembled monolayer principle was followed, to obtain sensitive, selective and disposable electrodes. Therefore, the Au electrodes were modified with cysteamine (Cys) to obtain a functional surface for FcPAMAM dendrimers to bind. Dendrimer generations were attached to this surface using a cross‐linker (glutaraldehyde) so that a suitable surface was obtained for binding of biological components. The Monoclonal PSA antibody (anti‐PSA) was immobilized on the Au electrode surface which coated with dendrimer, and (Au/Cys/FcPAMAM/anti‐PSA) biosensing electrode was obtained. The PSA detection performances of electrochemical impedance spectroscopy (EIS) and Amperometry based immunosensors exhibited very low detection limits; 0.001 ng mL^?1 and 0.1 pg mL^?1, respectively. In addition, EIS and Amperometry based biosensors using Au/Cys/FcPAMAM/anti‐PSA sensing electrode were represented excellent linear ranges of 0.01 ng mL^?1 to 100 ng mL^?1 and 0.001 ng mL^?1 to 100 ng mL^?1. In order to determine the applicability recovery and selectivity tests were performed using three different proteins in human serum.     

Simultaneous analysis of non‐steroidal anti‐inflammatory drugs using electrochemically controlled solid‐phase microextraction based on nanostructure molecularly imprinted polypyrrole film coupled to ion mobility spectrometry

A simple, rapid, and highly sensitive method for simultaneous analysis of anti‐inflammatory drugs (naproxen, ibuprofen, and mefenamic acid) in diluted human serum was developed using the electrochemically controlled solid‐phase microextraction coupled to ion mobility spectrometry. A conducting molecularly imprinted polymer film based on polypyrrole was synthesized for the selective uptake and release of drugs. The film was prepared by incorporation of a template molecule (naproxen) during the electropolymerization of pyrrole onto a platinum electrode using cyclic voltammetry method. The measured ion mobility spectrometry intensity was related to the concentration of analytes taken up into the films. The calibration graphs (naproxen, ibuprofen, and mefenamic acid) were linear in the range of 0.1–30 ng/mL and detection limits were 0.07–0.37 ng/mL and relative standard deviation was lower than 6%. On the basis of the results obtained in this work, the conducting molecularly imprinted polymer films as absorbent have been applied in the electrochemically controlled solid‐phase microextraction and ion mobility spectrometry system for the selective clean‐up and quantification of trace amounts of anti‐inflammatory drugs in human serum samples. Scanning electron microscopy has confirmed the nano‐structure morphology of the polypyrrole film.     

An LC–MS/MS method for rapid and sensitive high‐throughput simultaneous determination of various protein kinase inhibitors in human plasma

A reliable, high‐throughput and sensitive LC–MS/MS procedure was developed and validated for the determination of five tyrosine kinase inhibitors in human plasma. Following their extraction from human plasma, samples were eluted on a RP Luna®‐PFP 100 Å column using a mobile phase system composed of acetonitrile and 0.01 m ammonium formate in water (pH ~4.1) with a ratio of (50:50, v /v) flowing at 0.3 mL min⁻¹. The mass spectrometer was operating with electrospray ionization in the positive ion multiple reaction monitoring mode. The proposed methodology resulted in linear calibration plots with correlation coefficients values of r ² = 0.9995–0.9999 from concentration ranges of 2.5–100 ng mL⁻¹ for imatinib, 5.0–100 ng mL⁻¹ for sorafenib, tofacitinib and afatinib, and 1.0–100 ng mL⁻¹ for cabozantinib. The procedure was validated in terms of its specificity, limit of detection (0.32–1.71 ng mL⁻¹), lower limit of quantification (0.97–5.07 ng mL⁻¹), intra‐ and inter assay accuracy (−3.83 to +2.40%) and precision (<3.37%), matrix effect and recovery and stability. Our results demonstrated that the proposed method is highly reliable for routine quantification of the investigated tyrosine kinase inhibitors in human plasma and can be efficiently applied in the rapid and sensitive analysis of their clinical samples.     

Development and Validation of a Liquid Chromatographic Method for the Determination of Leflunomide: Application to in vitro Drug Metal Interactions

Leflunomide is a leading drug for the treatment of rheumatoid arthritis. The principle aim of this study was to develop and validate an RP‐HPLC method for the determination of leflunomide in bulk and pharmaceutical dosage form using diclofenac sodium as an internal standard. For this purpose, chromatography was accomplished on a Purospher Start, C₁₈ (5 (m, 12.5 cm×0.46 cm) column at ambient temperature. Methanol:water (80:20, V/V) solvent system was selected as mobile phase, the pH of which was adjusted to 3.4 by ortho‐phosphoric acid and delivered at a flow rate of 1.2 mL·min⁻¹. Seperation of leflunomide and diclofenac sodium was carried out on a Purospher Start, C₁₈ equipped with a UV‐visible detector at 248 nm. The suitability of the method for the quantitative determination of the drugs is proven by validation in accordance with the requirements laid down by the International Conference on Harmonization (ICH) guidelines. The method was accurate (99.55%–100.03%), specific, linear (R²>0.999) and precise (intra‐day precision 0.023%–0.93% and inter‐day precision 0.26%–0.944%) in the range of 0.5–20 (g·mL⁻¹. The minimum limit of detection and quantification in pharmaceutical formulation were 0.05 and 0.15 (g·mL⁻¹, respectively. Thus the proposed method is simple, accurate, reproducible and suitable for the routine analysis of leflunomide in pharmaceutical formulations and was applied to study in vitro drug‐metal interactions.     

Analysis of Acidic Drugs in Swiss Wastewaters

Five acidic drugs (clofibric acid, ibuprofen, ketoprofen, mefenamic acid and diclofenac) were chosen in order to determine their behavior in a sewage treatment plant (STP). An analytical method using solid phase extraction (SPE) and a gas chromatograph coupled with a mass spectrometer (GC-MS) was used. The results show that four pharmaceuticals (clofibric acid, ketoprofen, mefenamic acid and diclofenac) are not well removed by treatment in Swiss STPs. Maximum concentration in the effluent was determined for mefenamic acid up to 1.0 µg/L. This component seems to be relevant in Swiss STPs effluents and we can expect its presence in surface waters.     

Simultaneous Electrochemical Detection of Co(II) and Cu(II) by 1‐Diazo‐2‐Naphthol‐4‐Sulfonic Acid/MWCNTs Modified Electrode

This work describes a simple preparation of 1‐diazo‐2‐naphthol‐4‐sulfonic acid (1,2,4‐acid) and multiwalled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) for the simultaneous detection of Co(II) and Cu(II). MWCNTs, with their good conductivity and large surface area, were drop‐casted onto the surface of the GCE prior to the electrodeposition of 1,2,4‐acid, a metal chelating agent. Co(II) and Cu(II) were simultaneously measured by differential pulse anodic stripping voltammetry (DPASV) in a batch system. Under optimum conditions, the linear range of Co(II) was between 0.10 and 2.5 μg mL⁻¹ with an LOD of 80 ng mL⁻¹. Two linear ranges were obtained for Cu(II), 0.0050 to 0.030 μg mL⁻¹ and 0.040 to 0.25 μg mL⁻¹,with an LOD of 2.4 ng mL⁻¹. The method offered a high operational stability for up to 52 measurements (RSD=3.4 % for Co(II) and 2.6 % for Cu(II)) and good reproducibility (RSD=1.2 % for Co(II) and 1.7 % for Cu(II)). In the simultaneous detection of Co(II) and Cu(II), there was no effect from common interferences found in wastewater. The method was successfully applied in real water samples with good recoveries (88.2±0.8 to 102.0±0.8 % for Co(II) and 96.5±0.4 to 103.8±0.9 % for Cu(II)) and the results were in good agreement with those obtained from inductively coupled plasma optical emission spectrometry (ICP‐OES) (P >0.05).     

Simultaneous Determination of Aluminum,Cadmium and Lead in Whole Blood by Simultaneous Atomic Absorption Spectrometry with Oxygen Charring

A method for the simultaneous determination of aluminum (Al), cadmium (Cd) and lead (Pb) in whole blood has been developed by using simultaneous atomic absorption spectrometry (SIMAAS) with oxygen charring. The optimized conditions for the simultaneous determination of Al, Cd and Pb were obtained in the presence of palladium (Pd) as the chemical modifier, using 600 °C and 2400 °C as the pyrolysis and the atomization temperature, respectively. The whole blood samples were diluted 1+5 (v/v) directly with 0.1% (v/v) Triton X‐100. Oxygen was employed to eliminate the interference of carbonaceous residues in the charring step before pyrolysis. The calibration curves were carried out with aqueous standard solutions and the linear ranges were 0–40 ng mL⁻¹, 0–4 ng mL⁻¹ and 0–40 ng mL⁻¹ for Al, Cd and Pb, respectively. The detection limits were 0.96 ng mL⁻¹ (19.2 pg) for Al, 0.03 ng mL⁻¹ (0.6 pg) for Cd and 0.60 ng mL⁻¹ (12.0 pg) for Pb. The spiked recoveries of Al, Cd and Pb in whole blood were 98.0%, 100.0% and 101.7%, respectively. The accuracy of the proposed method was evaluated with the analysis of a whole blood certified reference material (Seronorm, level 2). The found concentrations were in agreement with the recommended values. The proposed method has been successfully applied to the simultaneous determination of Al, Cd and Pb in whole blood of healthy volunteers before and after eating barbecued foods.     

Fe3O4 Nanorods-RGO-ionic Liquid Nanocomposite Based Electrochemical Sensor for Aflatoxin B1 in Ground Paprika

A novel and sensitive method for the determination of aflatoxin B1 (AFA−B1) in ground paprika using a methyltrioctylammonium chloride ionic liquid (IL), iron oxide nanorods (Fe₃O₄ nanorods) and reduced graphene oxide (RGO) fabricated glassy carbon electrode (GCE) was developed. The synthesized nanoparticles, nanocomposites and modified electrode surfaces were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA/DSC) and x-ray diffraction (XRD) analyses. Moreover, the electrochemical performance of the developed sensor was determined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained results demonstrate that the sensitivity of AFA−B1 is significantly enhanced on RGO-Fe₃O₄ nanorods-IL-GCE in comparison with bare GCE, RGO-GCE and RGO-Fe₃O₄ nanorods-GCE. The redox peak currents of AFA−B1 exhibited good linear relationship with its concentration in the range from 0.02 to 0.33 ng mL⁻¹ with detection limit of (LOD) 0.03 ng mL⁻¹ and limit of quantification (LOQ) 0.36 ng mL⁻¹ respectively (S/N=3). In addition, the fabricated electrode showed good stability and reproducibility. The proposed technique was effectively applied to identify the AFA−B1 in real ground paprika samples with acceptable results.     

Direct Electrochemical Nano‐immunosensor for Microcystin‐LR in Seawater

Microcystins are potent hepatotoxins produced by cyanobacteria, which proliferate in wastewaters with high nutrient content. Due to their high toxicity and potential risk to human health, even at low concentrations, the development of a sensitive and rapid method for the monitoring of microcystin‐LR (MC‐LR) in water samples is of great importance. In this context, a new direct electrochemical nano‐immunosensor for MC‐LR detection using the liquid crystal (E)‐1‐decyl‐4‐[(4‐decyloxyphenyl)diazenyl]pyridinium bromide (Br‐Py) as a redox probe and gold nanoparticles stabilized in bovine serum albumin (AuNP‐BSA) is described herein. The microcystin‐LR antibody (anti‐MC‐LR) was covalently immobilized using N‐(3‐dimethylaminopropyl)‐N‐ethylcarbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS) on an AuNP‐BSA/BrPy film. The proposed sensor response is based on the inhibition of the Br‐Py electrochemical signal after the specific interaction of MC‐LR with immobilized anti‐MC‐LR on the electrode surface. The electrochemical behavior of the immunosensor was studied by square‐wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, using SWV and an incubation time of 15 min, the immunosensor exhibits a linear response to MC‐LR concentrations of 0.05 to 500.0 ng mL⁻¹ with a detection limit of 0.05 ng mL⁻¹. The anti‐MC‐LR/AuNP‐BSA/Br‐Py/GCE was successfully applied in the determination of MC‐LR in spiked seawater samples.     

Simultaneous analysis of ten low‐molecular‐mass organic acids in the tricarboxylic acid cycle and photorespiration pathway in Thalassiosira pseudonana at different growth stages

A method using high‐performance liquid chromatography coupled with tandem mass spectrometry was developed for the simultaneous determination of organic acids in microalgae. o‐Benzylhydroxylamine was used to derivatize the analytes, and stable isotope‐labeled compounds were used as internal standards for precise quantification. The proposed method was evaluated in terms of linearity, recovery, matrix effect, sensitivity, and precision. Linear calibration curves with correlation coefficients >0.99 were obtained over the concentration range of 0.4–40 ng/mL for glycolic acid, 0.1–10 ng/mL for malic acid and oxaloacetic acid, 0.02–2 ng/mL for succinic acid and glyoxylic acid, 4–400 ng/mL for fumaric acid, 20–2000 ng/mL for isocitric acid, 2–200 ng mL⁻¹ for citric acid, 100–10000 ng mL⁻¹ for cis‐aconitic acid, and 1–100 ng mL⁻¹ for α‐ketoglutaric acid. Analyte recoveries were between 80.2 and 115.1%, and the matrix effect was minimal. Low limits of detection (0.003–1 ng/mL) and limits of quantification (0.01–5 ng/mL) were obtained except cis‐aconitic acid. Variations in reproducibility for standard solution at three different concentrations levels were <9%. This is the first report of the simultaneous analysis of ten organic acids in microalgae, which promotes better understanding of their growth state and provides reference value for high‐yield microalgae cultures.     

Simultaneous Determination of Atenolol,Rosuvastatin, Spironolactone,Glibenclamide and Naproxen Sodium in Pharmaceutical Formulations and Human Plasma by RP‐HPLC

A rapid and sensitive high‐performance liquid chromatographic method was developed and validated for the simultaneous determination and quantification of atenolol, rosuvastatin, spirnolactone, glibenclamide and naproxen sodium in bulk drugs, pharmaceutical formulations and in human plasma in the presence of internal standard (flurbiprofen). Chromatograms were developed with methanol and water (80:20, v/v) solvent system on a Purospher start, C₁₈ (5 μm, 250 × 4.6 mm) column and pH was adjusted to 3.40 with ortho‐phosphoric acid. Mobile phase was pumped with a flow rate of 0.90 mL/minute with 235 nm UV detection. Standard curves were linear over the concentration range 0.25‐30 μg/mL^?1. The coefficients of variation (C.V.%), were < 3% and LOD and LOQ were <0.0154 & 0.06 for inter‐ and intra‐day, respectively. The method was applied to drug interaction studies of atenolol with rosuvastatin, spironolactone, glibenclamide and naproxen to illustrate the scope and application of the methods to manage four different therapeutic classes of drugs, as they are co‐administered.     

Simultaneous determination and pharmacokinetic study of giraldoid a,giraldoid B in rat plasma after oral administration of Daphne giraldii Nitsche extracts by LC–MS/MS

A simple sensitive LC–MS/MS method has been developed for the simultaneous determination of giraldoid A and giraldoid B in rat plasma. The method was applied to pharmacokinetics studies of the two compounds from Daphne giraldii Nitsche. Chromatographic separation was accomplished on an Acquity UPLC™ BEH C₁₈ column (100 × 2.1 mm, 1.7 mm) by gradient elution with a flow rate of 0.2 mL min⁻¹_. The method was linear over the concentration range of 1.0–1000 ng mL⁻¹, and the lower limits of quantification were 1.04 ± 0.10 and 1.04 ± 0.09 ng mL⁻¹, respectively. The intra‐ and inter‐day precisions (RSD) were <10.14 and 9.96%. The extraction recovery of the analytes was acceptable. Stability studies demonstrated that the two compounds were stable in the preparation and analytical process. The maximum plasma concentration was 687.78 ± 243.62 ng mL⁻¹ for giraldoid A and 952.38 ± 131.99 ng mL⁻¹ for giraldoid B. The time to reach the maximum plasma concentration was 0.50 ± 0.37 h for giraldoid A and 0.50 ± 0.66 h for giraldoid B. The validated method was successfully applied to investigate the concentration–time profiles of giraldoid A and giraldoid B.