A simple HPLC method for quantitation of quercetin in herbal extracts

A reversed-phase HPLC method with UV detection was developed for the determination of quercetin. The method produced linear response over a wide concentration range, with an average accuracy of 95% and average intra- and interday variation of 0.75 and 0.3, respectively. The exactness of the method was proven by determining the recovery rates from 50 to 150% of standard concentration, which were found within the acceptable range of 95 to 105%. The method was used for quantitation of quercetin in the extracts of Psidium guajava, Vitis vinifera, and extracts rich in quercetin and other flavonols in the flavonoid family.     

A simple, sensitive liquid chromatographic method for quantitation of D-galactose and D-glucose in blood plasma

The concentrations of D-glucose and D-galactose in plasma of galactosemic rats were quantitatively measured by a liquid chromatographic method, based on retention of the weakly ionized monosaccharides by an anion exchange column under alkaline conditions, elution with 9 mmol/L NaOH, and electrochemical detection. This method is both simple and sensitive, since very dilute plasma samples can be directly analysed.     

A simple TLC and HPTLC method for separation of selected steroid drugs

Chromatographic properties of five steroid drugs: cortisone, hydrocortisone, methylprednisolone, prednisolone and norgestrel have been studied by normal-, reversed-phase and hydrophilic neutral cyano-bonded silica stationary phase with five binary mobile phases (acetonitrile-water, acetonitrile-DMSO, acetonitrile-methanol, acetone-petroleum ether, acetone-water) in which the concentration of organic modifier was varied from 0 to 100% (v/v). This study reports the optimization of steroid hormones separation. Chromatographic retention data and possible retention mechanisms are discussed. Separation abilities of mobile and stationary phases were studied using the principal component analysis method. The best separation of methylprednisolone and prednisolone is with a chromatographic system included silica gel as stationary phase and mixture of acetonitrile and DMSO (10:90 v/v). These two anti-inflammatory drugs can be fast separated from norgestrel when CN is used as stationary phase and acetone and water (40:60 v/v) as mobile phase. The highest values of the parameter Δ(ΔG°) and alfa for cortisone and hydrocortisone was observed in case of using CN as stationary phase and water-acetonitryle (40:60 v/v) as mobile phase.      

A simple spectroscopic method for the determination of the release kinetics of drugs from PHB

A simple method is proposed for the determination of the release kinetics of small molecular weight drugs from amorphous PHB. The method uses the hipsochromic shift of the absorbance of active molecules caused by changes in the UV–Vis spectra as an effect of changing environment. Fuchsine with a strong hypsochromic shift was used as model drug in the experiments. A simple experimental setup was created which consists of the positioning of a thin PHB film into the center of the cell of a spectrometer. The light goes through the film and the surrounding solution and records their spectra simultaneously. The arrangement makes possible the quantitative determination of the dissolution of the drug without any further interference. The solution of Fick's second law under the initial and boundary conditions of the experimental setup and the numerical solution of the equation allow the quantitative analysis of the experimental results and the prediction of release kinetics. Excellent agreement was found between prediction and the experimental results. The approach made possible also the determination of the diffusion coefficient of the model drug in amorphous PHB. The developed method can be used for all polymers and with all drugs, which show sufficiently strong hypsochromic shift during their transfer from the polymer to the solution phase.     

A colorimetric method for the quantitation of galacturonic acid

A simple, colorimetric assay that is specific for galacturonic acid is presented. The assay uses sulfuric acid, carbazole, a controlled heat water bath, and a spectrophotometer. Galacturonic acid can be detected as free sugar or in polymer forms, such as pectin.     

A quantitation method for mass spectrometry imaging

A new quantitation method for mass spectrometry imaging (MSI) with matrix-assisted laser desorption/ionization (MALDI) has been developed. In this method, drug concentrations were determined by tissue homogenization of five 10 μm tissue sections adjacent to those analyzed by MSI. Drug levels in tissue extracts were measured by liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). The integrated MSI response was correlated to the LC/MS/MS drug concentrations to determine the amount of drug detected per MSI ion count. The study reported here evaluates olanzapine in liver tissue. Tissue samples containing a range of concentrations were created from liver harvested from rats administered a single dose of olanzapine at 0, 1, 4, 8, 16, 30, or 100 mg/kg. The liver samples were then analyzed by MALDI-MSI and LC/MS/MS. The MALDI-MSI and LC/MS/MS correlation was determined for tissue concentrations of ~300 to 60,000 ng/g and yielded a linear relationship over two orders of magnitude (R(2) = 0.9792). From this correlation, a conversion factor of 6.3 ± 0.23 fg/ion count was used to quantitate MSI responses at the pixel level (100 μm). The details of the method, its importance in pharmaceutical analysis, and the considerations necessary when implementing it are presented.     

A simple and sensitive HPLC method for quantitation of low phenoprolamine hydrochloride concentrations in human plasma and its pharmacokinetic application

Phenoprolamine hydrochloride is a novel compound that works against a variety of types of hypertension. The purpose of this study was to develop a simple and sensitive high-performance liquid chromatographic method for quantitation of low phenoprolamine hydrochloride concentrations in human plasma and to apply it to pharmacokinetic study. The procedure involved extraction of the drug and clonidine (internal standard) from the plasma using diethyl ether. Chromatographic separations were carried out on a 4.6 x 200 mm Hypersil silica column with UV detection at 230 nm. The isocratic mobile phase, 1% ammonium acetate (pH 5.4) and methanol (0.3:99.7, v/v), was run at 1 mL/min. Extraction recovery was 84% for phenoprolamine hydrochloride at a concentration level of 200 ng/mL, and 76% for clonidine at 200 ng/mL. The method was linear in the concentration range 5-4000 ng/mL with a lower limit of quantitation of 5 ng/mL for phenoprolamine hydrochloride. Inter- and intra-day coefficients of variation were less than 10%. The validated method was successfully applied to a pharmacokinetic study in human after an oral administration of the drug, and the pharmacokinetic parameters are presented.     

A predictive-kinetic method for the quantitation of amino acids with ninhydrin

The development and evaluation of a predictive-kinetic method for quantifying amino acids based on reactions with ninhydrin are described. Conditions are developed for which reactions are pseudo-first-order in the amino acid. Absorbance vs. time data from the kinetic region of the reaction (1–3 half-lives) are fitted to a first-order model to predict the total absorbance change that would occur if the reaction were monitored to completion. Computed absorbance changes vary linearly with amino acid concentration between 1 × 10^?5 and 5 × 10^?5 mol l^?1. Results are virtually independent of changes in temperature (± 1° C) and ninhydrin concentration (± 3 × 10^?3 mol l^?1).     

A simple method for the alpha-oxygenation of aldehydes

A mild, efficient and general method for the chemospecific alpha-oxygenation of aldehydes is described. Treatment of a series of aldehydes with N-tert-butyl-O-benzoyl hydroxylamine hydrochloride gives the corresponding alpha-oxygenated carbonyl via a proposed pericyclic rearrangement process.     

A simple method for the purification of fluorine

A simple method for the purification of fluorine gas is described. With the exception of nitrogen and argon, all impurities usually present in commercial fluorine can be readily removed by 1) conversion of O₂ to non-volatile O⁺₂ salts, and 2) a 70 to 63°K trap-to-trap distillation.     

一种测定功能蛋白与其配体结合参数的简单方法

以羰基二咪唑法分别将牛血清白蛋白(BSA)和β2-肾上腺素受体(β2-AR)键合在大孔硅胶上,合成两种色谱固定相。采用直接进样法测定BSA与奥美拉唑、普萘洛尔和盐酸异丙嗪的结合常数及结合位点数,β2-AR与盐酸异丙肾上腺素、沙丁胺醇和去甲肾上腺素的结合常数及结合位点数。方法可用于功能蛋白与其配体分子相互作用的研究。     

一种测定功能蛋白与其配体结合参数的简单方法

以羰基二咪唑法分别将牛血清白蛋白(BSA)和β2-肾上腺素受体(β2-AR)键合在大孔硅胶上,合成两种色谱固定相。采用直接进样法测定BSA与奥美拉唑、普萘洛尔和盐酸异丙嗪的结合常数及结合位点数,β2-AR与盐酸异丙肾上腺素、沙丁胺醇和去甲肾上腺素的结合常数及结合位点数。方法可用于功能蛋白与其配体分子相互作用的研究。     

A liquid chromatography-mass spectrometry method for the quantitation of aristololactam-I in rat plasma

A sensitive method with liquid chromatography-electrospray ionization mass spectrometry has been developed and validated for the determination of aristololactam-I in rat plasma after oral administration of aristolochic acid-I using finesteride as the internal standard. Chromatographic separation was achieved on a Lichrospher C(18) column using methanol:0.05% acetic acid in water (71:29, v/v) as a mobile phase delivered at a flow rate of 1 mL/min. The assay was linear for aristololactam-I over the range 0.3-300 ng/mL. The analysis of quality control samples demonstrated precision with coefficient of variation less than 20% (n = 5). Absolute recovery of aristololactam-I was 90.4-97.3%. The LC-MS method for the determination of aristololactam-I is sensitive, specific and can be used to investigate the toxicokinetics of aristololactam-I.     

A simple method for a determination

The a term is a primary parameter that is used to indicate the deviation of the epithermal neutron distribution in the k ₀-standardization method of neutron activation analysis, k ₀-NAA. The calculation of a using a mathematical procedure is a challenge for some researchers. The calculation of a by the "bare-triple monitor" method is possible using the dedicated commercial software KAYZERO^®/SOLCOI^®. However, when this software is not available in the laboratory it is possible to carry out the calculation of a applying a simple iterative linear regression using any spreadsheets. This approach is described in this paper. The experimental data used in the example were obtained by the irradiation of a set of suitable monitors in the NAA #1 irradiation channel of the HANARO research reactor (KAERI, Korea). The results obtained by this iterative linear regression method agree well with the results calculated by the validated mathematical method.     

A HPLC method for the quantitation of propafenone and 5-hydroxy propafenone

Summary This paper presents a method for the simultaneous detection of propafenone and 5-hydroxypropafenone (5-OH propafenone) using HPLC. The method is sensitive, selective, and reproducible. The chromatographic separation is based on a 25×0.4 cm 5 m ODS column, a mobil phase of 0.1 M potassium phosphate (K₂HPO₄) buffer (pH 2.5) and acetonitrile (6337), and UV absorbance detection. There is excellent intra- and interassay variation. Retention times of the internal standard, propafenone, and 5-OH propafenone are 4.3, 6.0 and 2.9 minutes respectively. This method shows linearity over the therapeutic range for propafenone and 5-OH propafenone (0.15 to 3.0 g/ml and 0.075 to 1.5 g/ml respectively). No interference has been found from other commonly administered drugs, including several antiarrhythmic drugs, at therapeutic levels.     

A liquid chromatography–tandem mass spectrometry method for the quantitation of actarit in rabbit plasma: application to pharmacokinetics and metabolic stability

Actarit (ATR), 4‐acetylaminophenylacetic acid is an orally effective disease‐modifying anti‐rheumatic drug widely prescribed for the treatment of rheumatoid arthritis. The present study demonstrates the first report on a selective and sensitive liquid chromatography–tandem mass spectrometry method for the quantification of ATR in rabbit plasma using p‐coumaric acid as an internal standard (IS). Following liquid–liquid extraction, chromatographic separation of the reconstituted samples was achieved isocratically on a Syncronis‐C18 column with a mobile phase consisting of aqueous ammonium acetate (10 mM, pH 4)‐ methanol and acetonitrile mixture (8 : 92, v/v) at a flow rate of 0.6 ml/min. ATR and IS were detected using electrospray ionization operated in negative multiple reaction monitoring mode. The calibration curve was linear (r² ≥ 0.990) over the concentration range of 1–4000 ng/ml with a lower limit of quantitation of 1 ng/ml. The mean extraction recovery of ATR and IS from rabbit plasma was greater than 85%. The method complied well with US Food and Drug Administration guidelines for selectivity, sensitivity, accuracy, precision, matrix effect, dilution integrity, carry‐over effect and stability. The method was successfully applied to in vitro metabolic stability (using rabbit liver microsomes) and in vivo pharmacokinetic study after oral administration of ATR at a dose of 10 mg/kg in New Zealand rabbits. Copyright © 2015 John Wiley & Sons, Ltd.