Determination of thioguanine in pharmaceutical preparations by paper substrate room temperature phosphorimetry

A room temperature phosphorimetric (RTP) procedure was used for the determination of 6-thioguanine (6-TG). The method is based on paper substrate room temperature phosphorimetry (PS-RTP) using indium sulfate, In2(SO4)3 as a heavy atom perturber. Various factors affecting the room temperature phosphorescence of 6-TG are discussed. The linear dynamic range for 6-TG is from 3.3 to 334.3 ng per spot with a detection limit of 4.6 ng per spot and a relative standard deviation (RSD) of 2.38%. The recovery of standard 6-TG added to commercial tablets is in the range 96.39-98.44%. The method is simple, rapid and sensitive and can be applied to the analysis of commercial tablets without interference.     

Study on the paper substrate room temperature phosphorescence of theobromine,caffeine and theophylline and analytical application

Paper substrate room temperature phosphorescence (RTP) of theobromine (TB), caffeine (CF) and theophylline (TP) were investigated. The method is based on fast speed quantitative filter paper as substrate and KI-NaAc as heavy atom perturber. Various factors affecting their RTP were discussed in detail. Under the optimum experimental conditions, the linear dynamic range, limit of detection (LOD), and relative standard deviation (R.S.D.) were 14.41 approximately 576.54 ng per spot, 1.14 ng per spot, 4.8% for TB, 5.44 approximately 699.08 ng per spot, 0.78 ng per spot, 1.56% for CF, 7.21 approximately 360.34 ng per spot, 1.80 ng per spot, 3.80% for TP, respectively. The first analytical application for the determination of these compounds was developed. The recovery of standard samples added to commercial products chocolate, tea, coffee and aminophylline is in the range 92.80-106.08%. The proposed method was successfully applied to real sample analysis without separation.     

Kinetic Spectrophotometric Determination of Vanadium (V) Based on its Inhibitory Effect on the Thionine – Ascorbic Acid Reaction

ABSTRACT

A simple and sensitive kinetic method for the determination of vanadium(V) based on its inhibitory effect on the reduction of thionine by ascorbic acid at pH=5 is described. The reaction rate is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 598 nm after a fixed time (10 min). The calibration graph is linear in the range of 10 ? 120 ng ml^?1 of vanadium(V) and the detection limit is 6 ng ml^?1. The relative standard deviation (RSD) for 80 ng ml^?1 of V(V) was 0.96% (n=10). The method was successfully applied to the determination of vanadium in a certified reference sample.     

Determination of LY217332, A New 3'-Quaternary Ammonium Cephalosporin,In Plasma by Solid Phase Column Extraction and HPLC

Abstract

A sensitive and rapid assay has been developed for the determination of LY217332, a 3'-imidazolo[4,5-c]pyridinium cephalosporin, in plasma. The method utilizes cyano solid phase column extraction and HPLC with ultraviolet detection. The lower limit of detection is 5 ng/ml plasma and the relative standard deviation for precision and accuracy was 5% or less from 50–500 ng/ml. The method is applicable to the assay of ceftazidime, cephaloridine, cefpirome and BMY-28142 with minor modification of the mobile phase and the detection wavelength.     

Quantitation of a novel antiemetic (ADR-851) in plasma and urine by reversed-phase high-performance liquid chromatography with fluorescence detection

A sensitive and specific bioanalytical method for quantitation of a novel antiemetic (ADR-851) in plasma and urine has been developed and validated. The drug and internal standard (metoclopramide) are extracted from the plasma matrix by solid-phase extraction on cyanopropyl bonded-phase columns. After extraction, samples are separated by isocratic reversed-phase high-performance liquid chromatography. The parent drug, internal standard and a yet unidentified metabolite are detected by fluorescence. The method requires 1.0 ml of plasma or 0.1 ml of urine and has a lower limit of quantitation of 2 ng/ml with 10.9% relative standard deviation (R.S.D.). Method linearity has been established over a 2-800 ng/ml range when 1.0 ml of plasma is used. The intra- and inter-day imprecisions for the method are typically better than 6% and 11% R.S.D., respectively, in both plasma and urine over the entire dynamic range. The pooled estimate of bias is less than 5% and attests to the excellent accuracy.     

Stability-indicating high performance thin layer chromatographic determination of sulfanilamide in human urine

A simple, sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic (HPTLC) method was developed and applied to human urine for the densitometric determination of sulfanilamide. A mixture of chloroform-ethyl acetate-xylene (2.5: 4.0: 1.0, v/v/v) was used as a mobile phase. The system was found to give compact spots for sulfanilamide (retardation factor, R _f = 0.21±0.02). The linear regression analysis data for the calibration plots showed good linear relationship with r ² = 0.9970 ± 0.0003 and r ² = 0.9947 ± 0.020 within the concentration range of 50–250 ng per spot and 100–1000 ng per spot with respect to peak area, respectively. The limit of detection (LOD) and quantification (LOQ) were 8 and 25 ng per spot, respectively. Sulfanilamide was subjected to acid and alkali hydrolysis, oxidation, dry heat and wet heat treatment. According to the International Conference on Harmonization (ICH) guidelines the method was validated for precision, recovery and robustness. The ultraviolet (UV) spectra of the degradation products which had different spectra from sulfanilamide were also recorded. The article is published in the original.     

A high selective and sensitive liquid chromatography–tandem mass spectrometry method for quantization of BPA urinary levels in children

A selective and highly sensitive liquid chromatography–tandem mass spectrometry method has been developed and validated for determination of Bisphenol A (BPA) in human urine using labeled d₆-BPA as internal standard. BPA was purified from human urine by affinity chromatography on solid extraction AFFINIMIP® Bisphenol A cartridges, based on molecularly imprinted polymers. After purification, the samples were analyzed on a Phenomenex Kinetex 100?×?4.6 mm, 2.6 μm particle PFP reversed-phase HPLC column, coupled to a triple quadrupole mass spectrometer by an electrospray ion source. Analyses were performed in the multiple reaction monitoring mode and negative ionization; the product ions at 133.2 and 212.1?m/z for BPA and at 138.2 and 215.0?m/z for d₆-BPA were monitored to assess unambiguous identification. The linearity of the detector response was verified in human urine over the concentration range 0.100–200 ng/mL. The detection limit was calculated as 0.03 ng/mL and the limit of quantification of the method is 0.10 ng/mL. This LC/ESI-MS/MS method was in-house validated evaluating specificity, trueness, within-day and between-days precision. The mean recoveries of BPA from spiked urine samples were higher than 94 % and good reproducibility (relative standard deviations?≤?8.1 %) was observed. The developed method was applied to a pilot study involving 105 children, aged from 6 to 14 years (16 normal weight and 89 obese children), from the Regione Campania (Southern Italy). The aim of this study was to determine the concentrations of BPA in urine of children and possible correlations with childhood obesity.     

A Unique Solid Phase Extraction Column for Isolation of 11-Nor-Δ-9-Tetrahydrocannabinol-9-Carboxylic Acid in Human Urine

Abstract

A sensitive, specific, qualitative, and quantitative extraction procedure followed by an hplc assay of 11-nor-Δ-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) from human urine is developed. Using a new, “mixed mode”, bonded silica gel solid phase extraction (SPE) column, the analyte was selectively isolated from the urine component. Following extraction, the presence of THC-COOH was confirmed and quantitated by a UV detector on a Varian 15cm C18 column using 35:65 v/v 50 mM phosphoric acid:acetonitrile at a flow rate of 1.5 mL/min. The limit of detection was 10 ng/mL at a signal to noise ratio of 2.5. The method showed linearity in the 10–300 ng/mL range (r=0.999) with good precision (RSD 1.4%) and accuracy (87% absolute recovery).     

High Sensitive and Selective Spectrophotometric Determination of Aluminium after Collection on a Membrane Filter Using 2,3‐Dichloro‐6‐(3‐carboxy‐2‐hydroxy‐1‐naphthylazo)quinoxaline and Zephiramine

Abstract

A high sensitive and selective spectrophotometric method for the determination of aluminium(III) using 2,3‐dichloro‐6‐(3‐carboxy‐2‐hydroxy‐1‐naphthylazo)quinoxaline (DCHNAQ) and zephiramine (zeph) is described. The formed ion pair precipitate between zephiramine and perchlorate ions is effective for the enrichment of aluminium(III) on a membrane filter as its ternary complex with DCHNAQ and zephiramine. The solid–state absorbance of the complex on the membrane filter is measured at 655 nm against a blank thin layer and the difference is calculated. The colour system obeys Beer's law from 5.0–150 ng ml^?1 of aluminium. The detection and quantification limits were calculated. The relative standard deviation for 60 ng of aluminium(III) in 20‐ml sample volume amounts 0.84% (n=10). A ligand buffer solution, composed of transcyclohexane‐1,2‐diaminetetraacetic acid with an excess of zinc(II), is effective for masking interferences from foreign ions, particularly iron(III). The proposed method was applied successfully to tap and environmental water, biological (human blood, urine, and gallstone), and soil samples.     

Determination of Pyridostigmine in Human Plasma by High-Performance Liquid Chromatography

Abstract

An easy to perform, specific, reproducible and sensitive high performance liquid chromatographic (HPLC) method to measure pyridostigmine concentration in human plasma was developed and validated. Sample clean-up consists of ion-pair extraction into dichloromethane in the presence of neostigmine as internal standard, followed by back extraction into an aqueous phase. Mean recovery of 110% (with a standard deviation of 10%) was determined for concentrations of 5 – 100 ng/ml. Chromatography on a 125·4 mm CN-propyl column using a mobile phase composed of 10% acetonitrile in 3.5×10^?4M NaH₂PO₄ and UV detection at 270 nm, yields clean chromatograms without any interferences from endogenous plasma components. Using 1 ml plasma samples the method has a limit of detection (LD) of 3 ng/ml, with %CV (precision) and bias (accuracy) ≥ 10% for concentrations in the range of 0–100 ng/ml. The method is being used in human pharmacokinetic studies of oral dosage forms of pyridostigmine.     

Rapid and Simple Methods for Determination of Medazepam in Pharmaceutical Preparations using GC-FID and GC-MS

Abstract

This paper describes two rapid, sensitive, and specific methods for the determination of medazepam with internal standard (diazepam) in pharmaceutical preparations by gas chromatography (GC) with flame ionization (FID) and mass spectrometric (MS) detection. The linearity was established over the concentration range of 0.25–5 µg/mL for GC-FID and 50–1000 ng/mL for GC-MS method. The intra- and inter-day relative standard deviation was less than 2.94 and 4.95%, respectively. Developed GC-FID and GC-MS methods in this study are accurate, sensitive, and precise and can be directly and easily applied to Tranko buskas as pharmaceutical preparation.     

Simultaneous analysis of gemfibrozil,morphine, and its two active metabolites in different mouse brain structures using solid‐phase extraction with ultra‐high performance liquid chromatography and tandem mass spectrometry with a deuterated internal standard

A rapid and sensitive bioassay was established and validated to simultaneously determine gemfibrozil, morphine, morphine‐3β‐glucuronide, and morphine‐6β‐glucuronide in mouse cerebrum, epencephalon, and hippocampus based on ultra‐high performance liquid chromatography and tandem mass spectrometry. The deuterated internal standard, M6G‐d3, was mixed with the prepared samples at 10 ng/mL as the final concentration. The samples were transferred into the C₁₈ solid‐phase extraction columns with gradient elution for solid‐phase extraction. The mobile phase consisted of methanol and 0.05% formic acid (pH 3.2). Multiple reaction monitoring has been applied to analyze gemfibrozil (m/z 249.0 → 121.0) in anion mode, and M6G‐d3 (m/z 465.1 → 289.1), morphine (m/z 286.0 → 200.9), and M3G and M6G (m/z 462.1 → 286.1) in the positive ion mode. The method has a linear calibration range from 0.05 to 10 ng for gemfibrozil, morphine, and M3G and M6G with correlation coefficients >0.993. The lower limit of quantitation for all four analytes was 0.05 ng/mL, relative standard deviation of intra‐ and interday precision was less than 10.5%, and the relative error of accuracy was from ?8.2 to 8.3% at low, medium, and high concentrations for all the analytes. In conclusion, gemfibrozil can influence the morphine antinociception after coronary heart disease induced chronic angina by the change in one of morphine metabolites', M3G, distribution in mouse brain.     

Spectrophotometric Catalytic Determination of Trace Amounts of Selenium Based on the Reduction of Azurea by Sulphide

ABSTRACT

A sensitive catalytic kinetic spectrophotometric method for determining ng ml^?1 concentrations of selenium is described. The method, based on the catalytic effect of Se (IV) on the reduction of azureA by sulphide, is monitored spectrophotometrically at 600 nm. The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, free from many interferences and is widely applicable. The limit of detection is 2.5ng ml^?1 of Se. The relative standard deviation of seven determinations of 100 ng ml^?1 Se was 1.5%. The method was applied to the determination of selenium in spiked water, Kjeldahl tablets, synthetic samples and health care products.     

Rapid determination of subnanogram urapidil using flow injection enhancement chemiluminescence

A sensitive flow-injection (FI) chemiluminescence (CL) for the determination of urapidil is described in this paper. It is based on the enhancement effect of urapidil on the CL reaction between luminol and hydrogen peroxide. The increment of CL intensity is proportional to the concentration of urapidil in the range 0.1−10 ng/mL (R ²=0.9986), with a detection limit (3σ) of 0.03 ng/mL. The whole process, at a flow rate of 2.0 mL/min, including sampling and washing, could be completed in 0.5 min, and the relative standard deviation (RSD) at the concentration of 0.1, 1.0, and 10.0 ng/mL was less than 3.0% (n = 5). The proposed method has been successfully applied for the determination of urapidil in pharmaceutical preparation, human urine, and serum. The text was submitted by the authors in English.     

An HPLC Assay for a Prostacyclin Analogue,Ciprostene Calcium,in Human Plasma

Abstract

A sensitive assay has been developed for the quantification of the prostacyclin analogue, ciprostene calcium, in human plasma. The method involves solid phase extraction of ciprostene calcium and internal standard, carbacyclin, from a small volume of human plasma. The extract is derivatized with 4-bramamethyl-7-acetoxycoumarin, and the derivatized product extracted with a polar solid phase cartridge and concentrated by evaporation. The final extract is separated by reversed phase HPIC and measured by a fluorimetric detector following post-column alkaline hydrolysis. The overall extraction efficiency is better than 75%, and the assay is linear over the concentration range studied (5–20 ng/ml). The limit of quantification was approximately 5 ng/ml. Ultimate sensitivity was limited by interfering peaks endogenous to the biological matrix. Coefficients of variation at mid-range concentrations are less than 10%.     

A highly sensitive method for the determination of 7‐aminonitrazepam,a metabolite of nitrazepam,in human urine using high‐performance electrospray liquid chromatography tandem mass spectrometry

A highly sensitive method has been developed for the determination of urinary 7‐aminonitrazepam (7‐ANZP), the major metabolite of nitrazepam, using high‐performance electrospray liquid chromatography tandem mass spectrometry. The samples were prepared for analysis by adding 7‐aminoclonazepam (7‐ACZP, internal standard), hydrolysis with β‐glucuronidase and liquid–liquid extraction. Mass spectral acquisition was achieved by selectively monitoring the reaction between the two diagnostic transition reactions. Qualitative analysis was based on the retention time, and the quantitation was carried out by comparison with the internal standard. The recoveries of different concentrations of 7‐ANZP from spiked blank samples was 89.0–95.2%, and the relative standard deviation was below 6.4%. The limit of determination in urine was 0.07 ng/mL, and the limit of quantitation was 0.5 ng/mL in the linear range of 1–50 ng/mL. This method possesses the merits of convenient operation, high sensitivity and good repeatability, making it a practical method for analysis of 7‐ANZP in urine. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical Enzyme‐Linked Immunoassay for the Determination of Estriol Using Methyl Red as Substrate

Abstract

A new electrochemical substrate for horseradish peroxidase, methyl red, is reported. In this reaction system, horseradish peroxidase can catalyze the redox reaction of methyl red and H₂O₂. Methyl red exhibits a sensitive voltammetric peak at?0.51 V vs. Ag/AgCl reference electrode, the decrease of the peak current of methyl red is in proportion to the concentration of horseradish peroxidase (HRP). The linear range for determination of horseradish peroxidase is 5.0×10^?8～5.0×10^?7 g mL^?1 and the detection limit is 1.8×10^?8 g mL^?1. The relative standard deviation is 3.3% when 2.0×10^?7 g mL^?1 HRP was sequentially determined 11 times. A voltammetric enzyme‐linked immunoassay method for the determination of estriol was developed, based on this electrochemical system. The linear range for determination of estriol is 1.0～1000.0 ng mL^?1, and the detection limit is 0.33 ng mL^?1. The relative standard deviation for 11 parallel determinations with 200 ng mL^?1 estriol is 4.8%. Some pregnancy serum samples were analyzed with satisfactory results.     

一种催化固体基质室温磷光法测定奋乃静

建立了罗丹明6G(Rhodamene.6G,Rhod 6G+)电子效应催化固体基质室温磷光法(SS-RTP)测定痕量奋乃静(Perphenazine,PPH)的新方法.方法的线性范围为0.080~28×10-9g/L,线性相关系数为0.999 l,相对标准偏差为1.5%~3.1%,检出限为4.8×10-14g/L.方法应用于血样、脉样中残留奋乃静含量的测定,结果令人满意.     

Detection of Wild-Type Hypoxanthine Guanine Phosphoribosyl Transferase of Lymphocytes in Gamma-Irradiated Mice with Surface Plasmon Resonance

A quick and sensitive detection of the wild-type hypoxanthine guanine phosphoribosyl transferase (HPRT), which is known as a biomarker for radiation exposure, was developed. The conventional HPRT measurement technique is to detect the mutant HPRT, which is time-consuming and has low sensitivity. In this study, the wild-type HPRT was detected as a gamma radiation biomarker using a surface plasmon resonance (SPR) biosensor with 6-thioguanine (6-TG) as a probe and the anti-HPRT antibody as a signal amplification factor. First, we used this system to measure the wild-type HPRT dissolved in PBS. Six-TG immobilized on the surface can specifically detect the wild-type HPRT, and the anti-HPRT antibody enhances about 10 times the primary signal produced by the binding of the wild-type HPRT with 6-TG. A linear relationship (r = 0.991) was obtained between the concentration of the wild-type HPRT and the enhanced signal. The low detection limit (LDL) is 2.1 ng/mL. The regeneration using glycine-HCl was also investigated. Six-TG immobilized on the surface can be used in 9 injection-regeneration cycles. The relative standard deviation (RSD) of baseline changes after regenerations is 2.8%. The applicability of the method to real samples has been demonstrated with comparative analyses of lymphocyte extracts in gamma irradiated and unirradiated mice. The irradiated sample displays a significantly lower level of the wild-type HPRT compared to that in the unirradiated sample. The single sample detection only needs about 20 min. Thus, the SPR biosensor could potentially serve as an attractive technique for rapid and sensitive detection of the wild-type HPRT, a gamma radiation biomarker.     

High Performance Liquid Chromatoraphic Determination of R-831, A New Antiallergic Agent,in Dogs and Humans

Abstract

A simple, selective and sensitive HPLC method has been developed to measure R-831 levels in dogs and humans. It is an internal standard technique with a single step extraction and one wash. Samples are chromatographed on a reversed-phase system with ultraviolet detection. The lowest detectable concentration for plasma is 25 ng R-831/ml with a 1 ml sample and the linear range is 25–8000 ng R-831/ml. The lowest detectable concentration for urine is 250 ng R-831/ml with a 0.1 ml sample and the linear range is 250–8000 ng R-831/ml. This method has been used to quantitate levels of R-831 in bioavailability and toxicity studies in dogs, and in pharmacokinetic and efficacy studies in humans.