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1.
A highly sensitive and relatively interference-free spectrophotometric method for determination of calcium is described. The method is based on the reaction between calcium ions and carboxyazo-p-CH3 in aqueous citrate medium of pH 7, to form a blue complex with maximum absorption at 716 nm. The calibration is linear up to 0.12 μg ml−1 calcium with a repeatability (R.S.D.) of 1.0% at a concentration of 0.04 μg ml−1 (n=5). The molar absorptivity of the complex and Sandell’s sensitivity are 3.5×105 l mol−1 cm−1 and 0.11 ng cm−2, its 10σ limit of quantification and the 3σ limit of detection were found to be 0.3 ng ml−1 and 0.09 ng ml−1 respectively. The influence of reaction variables and the effect of interfering ions are studied; no interference was observed in clinical samples. The proposed method has been applied directly to the determination of calcium in clinical samples without the need for pre-concentration, masking metal ions and digesting samples.  相似文献   

2.
Quantitation of trace levels of domoic acid (DA) in seawater samples usually requires labour-intensive protocols involving chemical derivatization with 9-fluorenylmethylchloroformate and liquid chromatography with fluorescence detection (FMOC–LC–FLD). Procedures based on LC–MS have been published, but time-consuming and costly solid-phase extraction pre-concentration steps are required to achieve suitable detection limits. This paper describes an alternative, simple and inexpensive LC method with ultraviolet detection (LC–UVD) for the routine analysis of trace levels of DA in seawater without the use of sample pre-concentration or derivatization steps. Qualitative confirmation of DA identity in dubious samples can be achieved by mass spectrometry (LC–MS) using the same chromatographic conditions. Addition of an ion-pairing/acidifying agent (0.15% trifluoroacetic acid) to sample extracts and the use of a gradient elution permitted the direct analysis of large sample volumes (100 μl), resulting in both high selectivity and sensitivity (limit of detection = 42 pg ml−1 by LC–UVD and 15 pg ml−1 by LC–MS). Same-day precision varied between 0.4 and 5%, depending on the detection method and DA concentration. Mean recoveries of spiked DA in seawater by LC–UVD were 98.8% at 0.1–10 ng ml−1 and 99.8% at 50–1000 ng ml−1. LC–UVD exhibited strong correlation with FMOC–LC–FLD during inter-laboratory analysis of Pseudo-nitzschia multiseries cultures containing 60–2000 ng DA ml−1 (r2 > 0.99), but more variable results were obtained by LC–MS (r2 = 0.85). This new technique was used to confirm the presence of trace DA levels in low-toxicity Pseudo-nitzschia spp. isolates (0.2–1.6 ng ml−1) and in whole-water field samples (0.3–5.8 ng ml−1), even in the absence of detectable Pseudo-nitzschia spp. cells in the water column.  相似文献   

3.
A novel kinetic chemiluminescent method using the stopped-flow mixing technique has been investigated for the rapid and sensitive determination of citrate and pyruvate. The method is based on a tris(2,2′-bipyridiyl)ruthenium(III) (Ru(bpy)33+) chemiluminescence (CL) reaction. Ru(bpy)33+ was generated in the mixing chamber by oxidising tris(2,2′-bipyridyl)ruthenium(II) with cerium(IV). After selecting the best operating parameters, calibration graphs were obtained over the concentration ranges 0.38-38 μg ml−1 and 8.7-1300 ng ml−1 for citrate and pyruvate, respectively. The limits of detection were 0.1 μg ml−1 for citrate and 0.3 ng ml−1 for pyruvate. Based on the differential rate of the chemiluminescent reaction corresponding to citrate and pyruvate, a very simple kinetic procedure was developed for the simultaneous determination of both compounds. Mixtures of citrate and pyruvate in ratios between 15:1 and 1.5:1 were satisfactorily resolved. The proposed method was successfully applied to the determination of citrate in pharmaceutical formulations, pyruvate in animal blood serum and both compounds in human urine.  相似文献   

4.
A new capillary electrophoresis (CE) method for the determination of quinolizidine alkaloids in Sophora medicinal plants was developed. A total of seven alkaloid components (cytisine, sophocarpine, matrine, lehmannine, sophoranol, oxymatrine and oxysophocarpine) were separated within 15 min. The running buffer was a 50 mM phosphate buffer containing 1%HP-β-CD and 3.3% isopropanol. The linear calibration ranges were 5.50-88.0 μg ml−1 for cytisine and lehmannine, 5.00-88.0 μg ml−1 for sophocarpine and sophoranol, 5.60-89.6 μg ml−1 for matrine and oxysophocarpine, and 24.0-384 μg ml−1 for oxymatrine. The recoveries of the seven alkaloids were 96.0-102.9% with relative standard deviations from 1.50 to 3.00% (n = 5). The method was successfully applied to different Sophora medicinal plants including Sophora flavescens, Sophora tonkinensis and Sophora alopecuroides.  相似文献   

5.
There has been considerable public interest and a growing number of scientific studies linking certain phenolic compounds in grapes and wines, particularly trans-resveratrol (trans-3,5,4′-trihydroxystilbene, TRA), to human health benefits. Typical TRA concentrations in wine are very low. It is a polar compound with very low volatility, which makes it difficult to extract and to separate on a gas chromatography (GC) column without derivatization. In this study, a new method for trace analysis of TRA was developed using solid-phase microextraction (SPME) with on-fiber silylation derivatization. Multidimensional GC equipped with a heartcut valve and cryogenic focusing was coupled with a mass-selective detector and used for improved separations and analysis. The effects of SPME fiber selection, extraction time, temperature, and desorption time were investigated. The derivatization conditions, time/temperature and the volume of derivatization reagent were also optimized. The calibration curve was linear over the concentration range from 10 ng L−1 to 5 mg L−1, with a correlation coefficient of 0.9996. The average recovery of TRA in red wine was 83.6 ± 5.6%. The method detection limit (MDL) for TRA in ethanol:water (12.5:87.5, v/v) solution in this study was 7.08 ng L−1 whereas the MDL for TRA in pure water was 2.85 ng L−1. The new method was used to test the TRA content in six selected Iowa red wine samples. Measured concentrations varied from 12.72 to 851.9 μg L−1.  相似文献   

6.
A simpler UV-vis spectrophotometric method was investigated for hydroquinone (HQ) determination using KMnO4 as oxidizing agent for conversion of HQ to p-benzoquinone (BQ) as well as signal enhancer. Various parameters such as analytical wavelength, stability time, temperature, pH, solvent effect and interference of chemicals were checked and parameters optimized by using 1 μg ml−1 standard solution of HQ. Beer's Law was applicable in the range of 0.07-2 μg ml−1 and 0.005-0.05 μg ml−1 at 245.5 nm and at 262 nm for aqueous standard solutions of HQ with linear regression coefficient value of 0.9978 and 0.9843 and detection limit of 0.021 μg ml−1 and 0.0016 μg ml−1 HQ, respectively. Standard deviation of 1.7% and 2.4% was true for 1 μg ml−1 and 0.03 μg ml−1 HQ solution (n = 11) run at respective wavelengths. The method was successfully applied to dilute waste photographic developer samples for free HQ determination.  相似文献   

7.
Two highly sensitive and selective methods based on gas chromatography coupled to mass spectrometry (GC-MS) in the selected ion monitoring (SIM) mode have been developed for the quantification of 2,6-dichlorophenol (2,6-DCP), a sex pheromone of the tick females of Anocentor nitens. Standard addition method and calibration curve techniques using 5-bromine-4-hydroxy-3-methoxybenzaldehyde (5-BrV) as internal standard (IS) afforded detection limit of 0.1 ng ml−1. The calibration curve was linear over the concentration range from 0.5 to 500 ng ml−1 for 2,6-DCP. Results show that the concentration range of sex pheromone in the extracts samples was 1.08-10.35 ng ml−1. The methods developed provided reliable procedures to determine amounts of 2,6-DCP present in ticks.  相似文献   

8.
The inhibitory effects of five hydroxyanthraquinones (HAQs) from root and rhizoma of Rheum officinale Baill, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by calorimetry. The power-time curves of S.aureus with and without HAQ were acquired and the extent and duration of inhibitory effects on the metabolism evaluated by growth rate constants (k1, k2), half inhibitory ratio (IC50), maximum heat output (Pmax) and peak time (tp). The value of k1 and k2 of S. aureus in the presence of the five HAQs decreased with the increasing concentrations of HAQs. Moreover, Pmax was reduced and the value of tp increased with increasing concentrations of the five drugs. The inhibitory activity varied for different drugs. IC50 of the five HAQs was 4 μg ml−1 for emodin, 3.5 μg ml−1 for rhein, 10 μg ml−1 for aloe-emodin, 1000 μg ml−1 for chrysophanol, 1600 μg ml−1 for physcion. The sequence of antimicrobial activity of the five HAQs: rhein > emodin > aloe-emodin > chrysophanol > physicion.  相似文献   

9.
An electrochemiluminescence (ECL)-based method for rapid and sensitive detection of acridinium ester in neutral solution was described. Strong ECL emission was observed when a positive voltage over 2.0 V (versus Ag/AgCl) was applied to the working electrode (Pt) immersed in the acridinium ester solution of 2.0 mol l−1 KNO3 (pH 7.0). The possible ECL mechanism was discussed. It was proposed that the ECL emission came out of N-methylacridone, the oxidization product of acridinium ester by the nascent oxygen generated on the surface of working electrode in the course of oxidization of water. Other influenced factors including the electrochemical parameters, the ECL reaction medium and pH value, were investigated in detail. Under the optimal conditions, ECL intensity has a linear relationship with the concentration of acridinium ester in the range of 0.24-96 ng ml−1 (r=0.9999). The relative standard deviation for 24 ng ml−1 acridinium ester was 4.6% (n=11). The limit of detection was 0.16 ng ml−1.  相似文献   

10.
A simple and rapid analytical method was developed for the determination of phthalates, usually employed in nail cosmetic products. The method is based on an ultrasonic extraction of the sample with ethanol-water (90:10, v/v) followed by HPLC separation and quantitation. HPLC was carried out using a C18 column and spectrophotometric detection at 254 nm. A linear gradient elution was performed with ethanol-water starting from 50 to 95% ethanol in 30 min. Standard calibration curves were linear for all the analytes over the concentration range 5-200 μg ml−1 with LOD values of about 0.5 μg ml−1.The proposed green analytical method has been successfully applied for the analysis of commercial samples in order to check the presence of phthalates and to determine their concentration.  相似文献   

11.
Wei Li 《Talanta》2007,71(1):385-390
A novel high-performance liquid chromatographic (HPLC) method using pre-column derivatization and UV detection at 275 nm for the determination of clarithromycin in rat plasma has been validated. Clarithromycin was extracted from plasma sample spiked with internal standard (erythromycin) under alkaline condition with ethyl ether and derivatizated with trimethylbromosilane. The analyses were run on a C18 column, maintained at 40 °C during elution, using a mobile phase comprised of potassium dihydrogen phosphate (50 mM, pH 6.8, contained 0.7% triethylamine), acetonitrile, and methanol (30:45:25, v/v/v). The standard calibration curve for clarithromycin was linear (r2 = 0.9998) over the concentration range of 0.1-10 μg ml−1 in rat plasma. The limit of detection (LOD) and limit of quantitation (LOQ) was 30 ng ml−1 and 0.1 μg ml−1 respectively. The intra- and inter-day assay variability range was 2.6-7.4% and 3.3-8.5%, respectively. This method has been successfully applied to a pharmacokinetic study of clarithromycin in rats.  相似文献   

12.
Yoon KH  Lee SY  Jang M  Ko SH  Kim W  Park JS  Park I  Kim HJ 《Talanta》2005,66(4):831-836
A simple, fast and sensitive high-performance liquid chromatography (HPLC)-electrospray ionization (ESI) tandem mass spectrometric method (LC-MS/MS) has been developed for determination of propiverine and propiverine N-oxide metabolite in human plasma using oxybutynin as internal standard. Instead of extracting propiverine from plasma using organic solvents, which should be separated from the aqueous phase and evaporated before injecting the sample into the chromatograph, plasma sample containing propiverine and N-oxide was directly injected after precipitating proteins with acetonitrile. Numerous compounds in the plasma did not interfere with the highly specific multiple reaction monitoring in tandem mass spectrometric detection following C8 reversed-phase chromatographic separation under conditions that eluted propiverine, N-oxide and oxybutynin within 2 min (0.1% formic acid in water/acetonitrile, 25:75, v/v). The LC-MS/MS method and an alternative LC-MS method, using methyl-t-butyl ether extraction and selected ion monitoring, were validated over 1-250 ng ml−1 of propiverine and 2 to 500 ng ml−1 of N-oxide, and successfully applied in a pharmacokinetic study. The lower limit of quantitation was 1 ng ml−1 for propiverine and 2 ng ml−1 for N-oxide in both methods.  相似文献   

13.
A study was performed to assess the performance of aminoacids immobilized on carbon nanotubes (CNTs) for their employment as a sorbent for solid phase extraction systems. An immobilization method is introduced and the aminoacid l-tyrosine was chosen as a case study. A spectrophotometric study revealed the amount of aminoacid immobilizated on CNTs surface, and it turned to be of 3174 μmol of l-tyr g−1. The material was tested for Co retention using a minicolumn inserted in a flow system. At pH 7.0, the amount of Co retained by the column was of 37.58 ± 3.06 μmol Co g−1 of CNTs. A 10% (v/v) HNO3 solution was chosen as eluent. The pH study revealed that Co binding increased at elevated pH values. The calculation of the mol ratio (moles of Co bound at pH 9 to moles of l-tyr) turned to be 3:1. The retention capacity was compared to other bivalent cations and showed the following tendency: Cu2+ > Ni2+ > Zn2+ ? Co2+. The analytical performance was evaluated and an enrichment factor of 180 was obtained when 10 mL of 11.37 μg L−1 Co solution was loaded onto the column at pH 9.0; reaching a limit of detection (LoD) of 50 ng L−1. The proposed system was successfully applied to Co determination in QC-LL2 standard reference material (metals in natural water).  相似文献   

14.
This study aims to use solid phase microextraction (SPME), a simple tool to investigate diffusion rate (time) constant of selected pharmaceuticals in gel and fish muscle by comparing desorption rate of diffusion of the drugs in both agarose gel prepared with phosphate-buffered saline (PBS; pH 7.4) and fish muscle. The gel concentration (agarose gel model) that could be used to simulate tissue matrix (fish muscle) for free diffusion of drugs under in vitro and in vivo conditions was determined to model mass transfer phenomena between fibre polymer coating and environmental matrix such that partition coefficients and desorption time constant (diffusion coefficient) can be determined. SPME procedure involves preloading the extraction phase (fibre) with the standards from spiked PBS for 1 h via direct extraction. Subsequently, the preloaded fibre is introduced to the sample such fish or agarose gel for specified time ranging from 0.5 to 60 h. Then, fibre is removed at specified time and desorbed in 100 μL of desorption solution (acetonitrile: water 1:1) for 90 min under agitation speed of 1000 rpm. The samples extract were immediately injected to the instrument and analysed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The limit of detection of the method in gel and fish muscle was 0.01–0.07 ng mL−1 and 0.07–0.34 ng g−1, respectively, while the limit quantification was 0.10–0.20 ng mL−1 in gel samples and 0.40–0.97 ng g−1 in fish sample. The reproducibility of the method was good (5–15% RSD). The results suggest that kinetics of desorption of the compounds in fish tissue and different viscosity of gel can be determined using desorption time constant. In this study, desorption time constant which is directly related to desorption rate (diffusion kinetics) of selected drugs from the fibre to the gel matrix is faster as the viscosity of the gel matrix reduces from 2% (w/v) to 0.8% (w/v). As the concentration of gel reduces, viscosity of the gel will be reduced therefore allowing faster diffusion which invariably affect desorption time constant. Also, desorption time constant of model drugs in the fish muscle and 0.8–0.9% (w/v) gel model are similar based on free diffusion of studied compounds. In addition, in vitro and in vivo desorption time constant comparison shows that desorption time constant in an in vivo system (live fish muscle) is generally higher than an in vitro system (dead fish muscle) except for sertraline and nordiazepam. This study demonstrates SPME as a simple investigative tool to understand kinetics of desorption in an in vivo system with a goal to measure desorption rate of pharmaceuticals in fish.  相似文献   

15.
A method for the simultaneous preconcentration and determination of Hg(II) and MeHg(I) at the ng ml−1 level has been developed. This method is based on solid phase extraction using a newly synthesized chelating resin containing nitrogen and sulphur donor sites of the 1,2-bis(o-aminophenylthio)ethane moiety that is very selective for mercury. The characterization of the resin has been carried out by elemental analyses, infrared spectral data, thermogravimetric analysis and metal ion capacities. The resin is highly selective for Hg(II) and MeHg(I) with an exchange capacity of 0.38 and 0.30 mmol g−1, respectively. Various parameters like pH, column flow rate, desorbing agents are optimized. Cold vapour atomic absorption spectrometry (CVAAS) was used to measure the concentration of both species of mercury. The calibration graph was linear upto 10 ng ml−1 with a 3σ detection limit of 0.09 ng ml−1. The recovery of Hg(II) and MeHg(I) was found to be 98.9±2.0 and 98.0±1.1%, respectively. The method has been used for routine determination of trace levels of mercury species in natural waters to comply with more stringent regulations.  相似文献   

16.
Wang Z  Zhang Z  Fu Z  Luo W  Zhang X 《Talanta》2004,62(3):611-617
A novel and sensitive chemiluminescence (CL) method for the determination of aminomethylbenzoic acid and aminophylline coupled with flow-injection analysis (FIA) technique is developed in this paper. It is based on the inhibition effect of the studied drugs on the chemiluminescence emission of N-bromosuccinimide-luminol (NBS-luminol) system. Under the optimum conditions, the decreased CL intensity is linear with the concentration of aminomethylbenzoic acid in the range of 2×10−8 to 1.0×10−6 g ml−1 and with the concentration of aminophylline in the range of 1×10−7 to 7.0×10−6 g ml−1, respectively. The detection limit is 7.0×10−9 g ml−1 for aminomethylbenzoic acid (3σ) and 3.4×10−8 g ml−1 for aminophylline (3σ). The relative standard deviations (R.S.D.) for 11 parallel measurements of 2.0×10−7 g ml−1 aminomethylbenzoic acid and 1.0×10−6 g ml−1 aminophylline are 2.6 and 3.0%, respectively. The proposed methods have been applied for the determination of the studied drugs in their pharmaceutical formulations with satisfactory results. The possible use of the proposed system for the determination of aminomethylbenzoic acid in plasma sample was also tested. The possible inhibition mechanism of aminomethylbenzoic acid and aminophylline on luminol-NBS system was discussed briefly.  相似文献   

17.
Gynostemma pentaphyllum (Thunb.) Makino, a traditional Chinese herb possessing antitumor and antioxidant activities, has been shown to contain several functional components like saponins and flavonoids. However, their identities remain uncertain. The objectives of this study were to develop an appropriate extraction, purification and HPLC-MS method to determine saponins and flavonoids in G. pentaphyllum. Both flavonoids and saponins were extracted with methanol, followed by purification with a C18 cartridge to elute the former with 50% methanol and the latter with 100% methanol. A total of 34 saponins were separated within 40 min by a Gemini C18 column and a gradient mobile phase of acetonitrile and 0.1% formic acid in water, in which 18 saponins were identified by LC-MS with ESI mode and Q-TOF (LC/MS/MS). Similarly, a total of eight flavonoids were separated within 45 min by the same column and a gradient solvent system of methanol and 0.1% formic acid in water, with identification being carried out by a post-column derivatization method and LC-MS with ESI mode. The amounts of flavonoids in G. pentaphyllum ranged from 170.7 to 2416.5 μg g−1, whereas saponins were from 491.0 to 89,888.9 μg g−1.  相似文献   

18.
We describe here a method for detecting and quantifying the highly carcinogenic polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP) in water, based on a flow-trough optical sensor. The technique is fast (response time of 40 s) and simple and at the same time meets the standards of sensitivity and selectivity required by the European Guidelines on Water for Human Consumption. The optosensor is based on the on-line immobilization of BaP on a non-ionic resin (Amberlite XAD-4) solid support in a continuous-flow system. BaP was analyzed in a 15 mM H2PO4/HPO42− buffer solution with 25% (v/v) 1,4-dioxane at pH 7. Fluorescence intensity was measured at λex/em=392/406 nm. The experimental conditions (reagent phase, pH, type and concentration of buffer solution and organic solvent) and flow-injection values (flow rate and injection volume) were carefully controlled. Under these conditions the optosensor was sensitive to a linear concentration range of between 3.0 and 250.0 ng l−1 with a detection limit of 3.0 ng l−1 and a standard deviation of 1.5% at 150 ng l−1. The optosensor was applied to the quantification of BaP in drinking and waste water samples (95-105% recovery) in presence of the other 15 EPA PAHs at 1000 ng l−1 concentration level. The influence of other fluorescent polycyclic aromatic hydrocarbons and potential interference from ions usually present in water was also evaluated.  相似文献   

19.
Yongqiang Cheng  Yuqin Su 《Talanta》2007,71(4):1757-1761
A novel assay of DNA has been proposed by using ferric nanoparticles as probes coupled with resonance light scattering (RLS) detection. At pH 7.40, the RLS intensity of ferric nanoparticles can be greatly enhanced by the aggregation of positively charged ferric nanoparticles through electrostatic interaction with negatively charged DNA. The enhanced intensity of RLS at 452 nm is proportional to the concentration of DNA in the range of 0.01-0.8 μg ml−1 for calf thymus and salmon sperm DNA and in the range of 0.005-0.3 μg ml−1 for E. coli K12 genomic DNA. Detection limits are 3.6 ng ml−1 for calf thymus DNA, 4.4 ng ml−1 for salmon sperm DNA, and 1.9 ng ml−1 for E. coli K12 genomic DNA, respectively. Compared with the chromophores previously used in RLS assay, the ferric nanoparticles have offered several advantages in easy preparation, good photostability and high sensitivity without being modified or functionalized.  相似文献   

20.
A chitosan resin derivatized with N-methyl-d-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-d-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61 mmol ml−1 (= 2.1 mmol g−1). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1 ml resin; (5) complete elution of boron with 1 mol l−1 nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8 μg l−1. The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07 μg l−1 and the limit of quantification (LOQ) was 0.14 μg l−1 when the volume of each sample and eluent was 10 ml.  相似文献   

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