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1.
A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, followed by a 96-well protein precipitation, has been developed and fully validated for the determination of Phakellistatin 13 (PK13), a new cyclic heptapeptide isolated from the sponge Phakellia fusca Thiele, in rat plasma. After protein precipitation of the plasma samples (50 μL) in a 96-well plate by methanol (200 μL) containing the internal standard Pseudostellarin B (20 ng/mL), the plate was vortex mixed for 3 min. Following filtration for 5 min, the filtrate was directly injected into the LC-MS/MS system. The analytes were separated on an XB-C18 analytical column (5 μm, 50 mm × 4.6 mm i.d.) using an eluent of methanol–water (85:15, v/v) and detected by electrospray ionization mass spectrometry in the negative multiple reaction monitoring mode with a chromatographic run time of 5.0 min. The method was sensitive with a lower limit of quantification (LLOQ) of 0.1 ng/mL, with good linearity (r > 0.999) over the quantitation range of 0.1–5 ng/mL. The validation results demonstrated that this method was significantly specific, accurate, precise, and was successfully applied in measuring levels of PK13 in rat plasma following intravenous administration of 20, 50, and 100 μg/kg of peptide in rats, respectively, which was suitable for the preclinical pharmacokinetic studies on PK13.  相似文献   

2.
A simple and sensitive assay was developed and validated for the simultaneous quantification of rosuvastatin acid (RST), rosuvastatin-5S-lactone (RST-LAC), and N-desmethyl rosuvastatin (DM-RST), in buffered human plasma using liquid chromatography–tandem mass spectrometry (LC-MS/MS). All the three analytes and the corresponding deuterium-labeled (d6) internal standards were extracted from 50 μL of buffered human plasma by protein precipitation. The analytes were chromatographically separated using a Zorbax-SB Phenyl column (2.1 mm × 100 mm, 3.5 μm). The mobile phase comprised of a gradient mixture of 0.1% v/v glacial acetic acid in 10% v/v methanol in water (solvent A) and 40% v/v methanol in acetonitrile (solvent B). The analytes were separated at baseline within 6.0 min using a flow rate of 0.35 mL/min. Mass spectrometry detection was carried out in positive electrospray ionization mode. The calibration curves for all three analytes were linear (R ≥ 0.9964, n = 3) over the concentration range of 0.1–100 ng/mL for RST and RST-LAC, and 0.5–100 ng/mL for DM-RST. Mean extraction recoveries ranged within 88.0–106%. Intra- and inter-run mean percent accuracy were within 91.8–111% and percent imprecision was ≤15%. Stability studies revealed that all the analytes were stable in matrix during bench-top (6 h on ice–water slurry), at the end of three successive freeze and thaw cycles and at −80°C for 1 month. The method was successfully applied in a clinical study to determine the concentrations of RST and the lactone metabolite over 12-h post-dose in patients who received a single dose of rosuvastatin.  相似文献   

3.
A validated method for the simultaneous determination of prominent volatile cleavage products (CPs) of β-carotene in cell culture media has been developed. Target CPs comprised β-ionone (β-IO), cyclocitral (CC), dihydroactinidiolide (DHA), and 1,1,6-trimethyltetraline (TMT). CPs were extracted by solid-phase extraction applying a phenyl adsorbent, eluted with 10% (v/v) tetrahydrofuran in n-hexane, and identified and quantified by gas chromatography-mass spectrometry with electron impact ionization. Method validation addressed linearity confirmation over two application ranges and homoscedasticity testing. Recoveries from culture media were between 71.7% and 95.7% at 1.0 μg/ml. Precision of recoveries determined in intra-day (N = 5) and inter-day (N = 15) assays were <2.0% and <4.8%, respectively. Limit of detection and limit of quantification of the analysis method were <18.0 and <53.0 ng/ml for β-IO, CC, and TMT, whereas 156 and 474 ng/ml were determined for DHA, respectively. Although extractions of blank matrix proved the absence of interfering peaks, statistical comparison between slopes determined for instrumental and total method linearity revealed significant differences. The method was successfully applied in selecting an appropriate solvent for the fortification of culture media with volatile CPs, including the determination of their availability over the incubation period. For the first time, quantification of volatile CPs in treatment solutions and culture media for primary cells becomes accessible by this validated method.  相似文献   

4.
A liquid chromatography–mass spectrometry (LC-MS) method was developed and validated for the simultaneous determination of alisol A and alisol A 24-acetate from Alisma orientale (Sam.) Juz. in rat plasma using diazepam as an internal standard. A 200-μl plasma sample was extracted by methyl tert-butyl ether and the separation was performed on Kromasil C18 column (150 × 4.6 mm, 5 μm) with the mobile phase of acetonitrile (containing 0.1% of formic acid)–water (73:27, v/v) at a flow rate of 0.8 ml/min in a run time of 10 min. The two analytes were monitored with positive electrospray ionization by selected ion monitoring mode. The lower limit of quantitation for both alisol A and alisol A 24-acetate were 10 ng/ml. The calibration curves were linear in the measured range 10–1,000 ng/ml for alisol A and 10–500 ng/ml for alisol A 24-acetate. The mean extraction recoveries were above 74.7% for alisol A and above 72.4% for alisol A 24-acetate from biological matrixes. The intra- and inter-day precision for all concentrations of quality controls was lower than 14.1% (RSD %) for each analyte. The accuracy ranged from −12.3% to 9.8% (RE %) for alisol A, and −8.6% to 14.2% (RE %) for alisol A 24-acetate. The method was successfully applied to the study on the pharmacokinetics of alisol A and alisol A 24-acetate in rat plasma.  相似文献   

5.
In vivo measurement of multiple functionally related neurochemicals and metabolites (NMs) is highly interesting but remains challenging in the field of basic neuroscience and clinical research. We present here an analytical method for determining five functionally and metabolically related polar substances, including acetylcholine (quaternary ammonium), lactate and pyruvate (organic acids), as well as glutamine and glutamate (amino acids). These NMs are acquired from samples of the brain and the blood of non-human primates in parallel by dual microdialysis, and subsequently analyzed by a direct capillary hydrophilic interaction chromatography (HILIC)–mass spectrometry (MS) based method. To obtain high sensitivity in electrospray ionization (ESI)–MS, lactate and pyruvate were detected in negative ionization mode whereas the other NMs were detected in positive ionization mode during each HILIC-MS run. The method was validated for linearity, the limits of detection and quantification, precision, accuracy, stability and matrix effect. The detection limit of acetylcholine, lactate, pyruvate, glutamine, and glutamate was 150 pM, 3 μM, 2 μM, 5 nM, and 50 nM, respectively. This allowed us to quantitatively and simultaneously measure the concentrations of all the substances from the acquired dialysates. The concentration ratios of both lactate/pyruvate and glutamine/glutamate were found to be higher in the brain compared to blood (p < 0.05). The reliable and simultaneous quantification of these five NMs from brain and blood samples allows us to investigate their relative distribution in the brain and blood, and most importantly paves the way for future non-invasive studies of the functional and metabolic relation of these substances to each other.  相似文献   

6.
The purpose of this study was the development and validation of an LC–MS–MS method for simultaneous analysis of ibuprofen (IBP), 2-hydroxyibuprofen (2-OH-IBP) enantiomers, and carboxyibuprofen (COOH-IBP) stereoisomers in fungi culture medium, to investigate the ability of some endophytic fungi to biotransform the chiral drug IBP into its metabolites. Resolution of IBP and the stereoisomers of its main metabolites was achieved by use of a Chiralpak AS-H column (150 × 4.6 mm, 5 μm particle size), column temperature 8 °C, and the mobile phase hexane–isopropanol–trifluoroacetic acid (95: 5: 0.1, v/v) at a flow rate of 1.2 mL min−1. Post-column infusion with 10 mmol L−1 ammonium acetate in methanol at a flow rate of 0.3 mL min−1 was performed to enhance MS detection (positive electrospray ionization). Liquid–liquid extraction was used for sample preparation with hexane–ethyl acetate (1:1, v/v) as extraction solvent. Linearity was obtained in the range 0.1–20 μg mL−1 for IBP, 0.05–7.5 μg mL−1 for each 2-OH-IBP enantiomer, and 0.025–5.0 μg mL−1 for each COOH-IBP stereoisomer (r ≥ 0.99). The coefficients of variation and relative errors obtained in precision and accuracy studies (within-day and between-day) were below 15%. The stability studies showed that the samples were stable (p > 0.05) during freeze and thaw cycles, short-term exposure to room temperature, storage at −20 °C, and biotransformation conditions. Among the six fungi studied, only the strains Nigrospora sphaerica (SS67) and Chaetomium globosum (VR10) biotransformed IBP enantioselectively, with greater formation of the metabolite (+)-(S)-2-OH-IBP. Formation of the COOH-IBP stereoisomers, which involves hydroxylation at C3 and further oxidation to form the carboxyl group, was not observed.  相似文献   

7.
A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil, water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target compounds was achieved in <2.0 min. The limits of detection were below 1 μg kg−1, while the limits of quantification did not exceed 3 μg kg−1 in different matrices. Quantitation was determined from calibration curves of standards containing 0.05–100 μg L−1 with r 2 > 0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 μg kg−1 for water; 5, 10, and 100 μg kg−1 for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1–12.5% (n = 5) for all analytes.  相似文献   

8.
The paper presents a new sample clean-up method based on immuno-ultrafiltration for the analysis of ochratoxin A in cereals. In contrast to immunoaffinity chromatography, in immuno-ultrafiltration, the antibodies are used in non-immobilised form. Ochratoxin A was extracted with ACN/water (60/40, v/v), and the extract was loaded onto the ultrafiltration device. After a washing step with phosphate-buffered saline, containing 0.05% Tween 20, ochratoxin A was eluted with MeOH/acetic acid (99/1, v/v). The detection of ochratoxin A was carried out with high-performance liquid chromatography and a fluorescence detector coupled to an electrochemical cell (Coring cell). The electrochemical cell was used to eliminate matrix interferences by oxidising matrix compounds. The method was validated by repeatedly analysing spiked barley and rye samples as well as a certified wheat reference material. Recoveries and standard deviations (1 SD) were found to be 71 ± 9%, 77 ± 12% and 77 ± 8% in wheat, barley and rye, respectively. The limit of detection (S/N = 3) and limit of quantitation (S/N = 10) were determined to be 0.4 μg kg-1 and 1 μg kg-1. The analysis of the certified reference material resulted in ochratoxin A concentrations which were in the range assigned by the producer. Additionally, the effect of the electrochemical cell on other widely used clean-up techniques, namely the immunoaffinity clean-up and multifunctional columns (Mycosep #229), was evaluated. In all clean-up methods, an improvement of the chromatogram quality was registered.  相似文献   

9.
The development of a simple and rapid high-performance liquid chromatography (HPLC) method for the determination of the new antiepileptic drug rufinamide (RFN) in human plasma and saliva is reported. Samples (250 μl) are alkalinized with ammonium hydroxide (pH 9.25) and extracted with dichloromethane using metoclopramide as internal standard. Separation is achieved with a Spherisorb silica column (250 × 4.6 mm i.d., 5 μm) at 30 °C using as mobile phase a solution of methanol/dichloromethane/n-hexane 10/25/65 (vol/vol/vol) mixed with 6 ml ammonium hydroxide. The instrument used was a Shimadzu LC-10Av chromatograph and flow rate was 1.5 ml min-1, with a LaChrom L-7400 UV detector set at 230 nm. Calibration curves are linear [r 2 = 0.998 ± 0.002 for plasma (n = 10) and r 2 = 0.999 ± 0.001 for saliva (n = 9)] over the range of 0.25–20.0 μg ml-1, with a limit of quantification at 0.25 μg ml-1. Precision and accuracy are within current acceptability standards. The assay is suitable for pharmacokinetic studies in humans and for therapeutic drug monitoring.  相似文献   

10.
A sensitive, specific and efficient high-performance liquid chromatography-tandem mass spectrometry assay for the simultaneous determination of vincristine and actinomycin-D in human dried blood spots is presented. Dried blood spots were punched out of a collection paper with a 0.25-in.-diameter punch. The analytes were extracted from the punched-out disc using sonication during 15 min in a mixture of acetonitrile–methanol–water (1:1:1, v/v/v) containing the internal standard vinorelbine. Twenty-microlitre volumes were injected onto the HPLC system. Separation was achieved on a 50 × 2.1 mm ID Xbridge C18 column using elution with 1 mM ammonium acetate–acetonitrile (70:30, v/v) adjusted to pH 10.5 with ammonia and run in a gradient with methanol at a flow rate of 0.4 mL/min. HPLC run time was 6 min. The assay quantifies vincristine from 1 to 100 ng/mL and actinomycine-D from 2 to 250 ng/mL using a blood sample obtained by a simple finger prick. Validation results demonstrate that vincristine and actinomycin-D can be accurately and precisely quantified in human dried blood spots with the presented method. The assay can now be used to support clinical pharmacologic studies with vincristine and actinomycin-D.  相似文献   

11.
Authors developed a simple, sensitive, selective, rapid, rugged, and reproducible liquid chromatography–tandem mass spectrometry method for the quantification of eletriptan (EP) in human plasma using naratriptan (NP) as an internal standard (IS). Chromatographic separation was performed on Ascentis Express C18, 50 × 4.6 mm, 2.7 μm column. Mobile phase was composed of 0.1% formic acid: methanol (40:60 v/v), with 0.5 mL/min flow rate. Drug and IS were extracted by liquid–liquid extraction. EP and NP were detected with proton adducts at m/z 383.2→84.3 and 336.2→97.8 in multiple reaction monitoring (MRM) positive mode, respectively. The method was validated with the correlation coefficients of (r 2) ≥ 0.9963 over a linear concentration range of 0.5–250.0 ng/mL. This method demonstrated intra- and inter-day precision within 1.4–9.2% and 4.4–5.5% and accuracy within 96.8–103% and 98.5–99.8% for EP. This method is successfully applied in the bioequivalence study of 24 human volunteers.  相似文献   

12.
The first liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous quantification of p-aminohippuric acid and inulin, both typical biomarkers of kidney function. 5-(Hydroxymethyl)furfural, generated from inulin by acid and heat preparation, was used as an inulin substitute for the quantification. Acetaminophen was used as the internal standard. Solid-phase extraction was carried out with 5% methanol as the washing solution to optimize the retention of the analytes and to avoid obstruction of the orifice plate of the mass spectrometer caused by any unreacted inulin residue remaining from the sample preparation process. Chromatography separation was performed on a Symmetry C18 column and a mobile phase composed of 2 mM ammonium formate and 0.1% formic acid in water (solvent A) and 2 mM ammonium formate and 0.1% formic acid in acetonitrile (solvent B) (30:70, v/v). Detection was performed with a triple-quadrupole tandem mass spectrometer using positive ion mode electrospray ionization in the multiple reaction monitoring mode. The selected transitions were m/z 195.2 → 120.2, 127.1 → 109.1, and 152.1 → 110.0 for p-aminohippuric acid, inulin [measured as 5-(hydroxymethyl)furfural], and acetaminophen, respectively. The linearity ranged from 10 to 140 μg/mL and from 100 to 1,400 μg/mL for p-aminohippurric acid and inulin (r > 0.99), respectively. The precisions and accuracies were all within 12 and 11% for the lower limit of quantification and quality control samples, respectively. This application was proven to be reliable and accurate and was successfully applied to a renal function study.  相似文献   

13.
The aim of the proposed work was to develop and validate a simple and sensitive assay for the analysis of atorvastatin (ATV) acid, ortho- and para-hydroxy-ATV, ATV lactone, and ortho- and para-hydroxy-ATV lactone in human plasma using liquid chromatography-tandem mass spectrometry. All six analytes and corresponding deuterium (d5)-labeled internal standards were extracted from 50 μL of human plasma by protein precipitation. The chromatographic separation of analytes was achieved using a Zorbax-SB Phenyl column (2.1 mm × 100 mm, 3.5 μm). The mobile phase consisted of a gradient mixture of 0.1% v/v glacial acetic acid in 10% v/v methanol in water (solvent A) and 40% v/v methanol in acetonitrile (solvent B). All analytes including ortho- and para-hydroxy metabolites were baseline-separated within 7.0 min using a flow rate of 0.35 mL/min. Mass spectrometry detection was carried out in positive electrospray ionization mode, with multiple-reaction monitoring scan. The calibration curves for all analytes were linear (R 2 ≥ 0.9975, n = 3) over the concentration range of 0.05–100 ng/mL and with lower limit of quantitation of 0.05 ng/mL. Mean extraction recoveries ranged between 88.6–111%. Intra- and inter-run mean percent accuracy were between 85–115% and percent imprecision was ≤ 15%. Stability studies revealed that ATV acid and lactone forms were stable in plasma during bench top (6 h on ice-water slurry), at the end of three successive freeze and thaw cycles and at −80 °C for 3 months. The method was successfully applied in a clinical study to determine concentrations of ATV and its metabolites over 12 h post-dose in patients receiving atorvastatin.  相似文献   

14.
A new high-performance liquid chromatography assay was developed for the determination of minocycline in plasma and brain. A solid–liquid extraction procedure was coupled with a reversed-phase HPLC system. The system requires a mobile phase consisting of acetonitrile:water:perchloric acid (26:74:0.25, v/v/v) adjusted to pH 2.5 with 5 M sodium hydroxide for elution through a RP8 column (250 × 3.0 mm, i.d.) with UV detection set at 350 nm. The method proved to be accurate, precise (RSD < 20%) and linear between 0.15–20 μg mL−1 in plasma and 1–20 μg mg−1 in brain. The method was successfully applied to a blood-brain barrier minocycline transport study.  相似文献   

15.
The possibilities of different media formed by lecithin/n-butanol (n-BuOH)/water ternary mixtures for the analysis of all-trans-retinol by fluorescence have been studied. Fluorescence intensity of retinol increases in the presence of different types of aggregates formed in these media. Analytical features are good, the detection limit and quantification limit have micrograms per liter levels, and the linear range and sensitivity are appropriate to determine retinol in cosmetic samples. The analysis of retinol in anti-wrinkle creams can be achieved directly without any pretreatment of the sample. The vesicles built up from a biocompatible surfactant (lecithin) in aqueous solution with a low amount of n-BuOH permit an appropriated media for a simple, rapid, and sensitive analytical method. This method has a linear range between 64.1 and 800 μg L−1, a sensitivity of 202.3 L mg−1, and a low detection and quantification limit at 19.2 and 64.1 μg L−1, respectively.  相似文献   

16.
A cloud-point extraction (CPE) method using Triton X-114 non-ionic surfactant was developed for the extraction and preconcentration of carbamate insecticide residues (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in fruit samples. The optimum conditions of CPE were 1.5% (w/v) Triton X-114, 7.0% (w/v) NaCl and 20 min equilibrated at 45 °C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 270 nm, under gradient separation using methanol and 0.1% (v/v) acetic acid. Under the study conditions, six carbamate insecticides were successfully separated within 27 min. Good reproducibility was obtained with the relative standard deviation of <3% for retention time and <9% for peak area. Limits of detection in the studied fruit samples were in the range of 0.1–1.0 mg kg−1. No carbamate insecticides were detected in the studied fruit samples. The high recoveries of the spiked fruit samples were obtained in the range 80.0–107%. The CPE method has been shown to be a potential useful methodology for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environmental friendly.  相似文献   

17.
This study provides a versatile validated method to determine the total vitamin C content, as the sum of the contents of L-ascorbic acid (L-AA) and dehydroascorbic acid (DHAA), in several fruits and vegetables and its degradability with storage time. Seven horticultural crops from two different origins were analyzed using an ultra-high-performance liquid chromatographic–photodiode array (UHPLC-PDA) system, equipped with a new trifunctional high strength silica (100% silica particle) analytical column (100 mm × 2.1 mm, 1.7 μm particle size) using 0.1% (v/v) formic acid as mobile phase, in isocratic mode. This new stationary phase, specially designed for polar compounds, overcomes the problems normally encountered in HPLC and is suitable for the analysis of large batches of samples without L-AA degradation. In addition, it proves to be an excellent alternative to conventional C18 columns for the determination of L-AA in fruits and vegetables. The method was fully validated in terms of linearity, detection (LOD) and quantification (LOQ) limits, accuracy, and inter/intra-day precision. Validation experiments revealed very good recovery rate of 96.6 ± 4.4% for L-AA and 103.1 ± 4.8 % for total vitamin C, good linearity with r 2 -values >0.999 within the established concentration range, excellent repeatability (0.5%), and reproducibility (1.6%) values. The LOD of the method was 22 ng/mL whereas the LOQ was 67 ng/mL. It was possible to demonstrate that L-AA and DHAA concentrations in the different horticulture products varied oppositely with time of storage not always affecting the total amount of vitamin C during shelf-life. Locally produced fruits have higher concentrations of vitamin C, compared with imported ones, but vegetables showed the opposite trend. Moreover, this UHPLC-PDA methodology proves to be an improved, simple, and fast approach for determining the total content of vitamin C in various food commodities, with high sensitivity, selectivity, and resolving power within 3 min of run analysis.  相似文献   

18.
In this work, a new method was developed for the determination of melamine (MEL) in animal feed. The method was based on the on-line coupling of dynamic microwave-assisted extraction (DMAE) to strong cation-exchange (SCX) resin clean-up. The MEL was first extracted by 90% acidified methanol aqueous solution (v/v, pH = 3) under the action of microwave energy, and then the extract was cooled and passed through the SCX resin. Thus, the protonated MEL was retained on the resin through ion exchange interaction and the sample matrixes were washed out. Some obvious benefits were achieved, such as acceleration of analytical process, together with reduction in manual handling, risk of contamination, loss of analyte, and sample consumption. Finally, the analyte was separated by a liquid chromatograph with a SCX analytical column, and then identified and quantitatived by a tandem mass spectrometry with positive ionization mode and multiple-reaction monitoring. The DMAE parameters were optimized by the Box–Behnken design. The linearity of quantification obtained by analyzing matrix-matched standards is in the range of 50–5,000 ng g−1. The limit of detection and limit of quantification obtained are 12.3 and 41.0 ng g−1, respectively. The mean intra- and inter-day precisions expressed as relative standard deviations with three fortified levels (50, 250, and 500 ng g−1) are 5.1% and 7.3%, respectively, and the recoveries of MEL are in the range of 76.1–93.5%. The proposed method was successfully applied to determine MEL in different animal feeds obtained from the local market. MEL was detectable with the contents of 279, 136, and 742 ng g−1 in three samples.   相似文献   

19.
A liquid chromatographic–mass spectrometric (LC–MS) method has been developed and validated for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma. After addition of the internal standard, domperidone, plasma samples were extracted by liquid–liquid extraction with ethyl acetate and separated on an Apollo C18 column (250 mm × 4.6 mm, 5 μm), with methanol–0.01% formic acid water (60:40, v/v) as mobile phase, within a runtime of 12.0 min. The analytes were detected without interference in the selected ion monitoring (SIM) mode with positive electrospray ionization. The linear range was 1.0–500 ng mL−1 for dehydroevodiamine and 2.0–1,000 ng mL−1 for limonin, with lower limits of quantitation of 1.0 and 2.0 ng mL−1, respectively. Intra-day and inter-day precision were within 6.0% and 10.9%, respectively, for both analytes, and the accuracy (relative error, RE, %) was less than 4.8% and 6.5%, respectively. The validated method was successfully applied to a comparative pharmacokinetic study of dehydroevodiamine and limonin in rat plasma after oral administration of dehydroevodiamine, limonin, and an aqueous extract of Evodiae fructus. The results indicated there were obvious differences between the pharmacokinetic behavior after oral administration of an aqueous extract of Evodiae fructus compared with single substances.  相似文献   

20.
A novel method is proposed for the extraction-thermal lens quantification of cobalt with Nitroso-R-Salt based on the distribution of the colored complex in a two-phase aqueous system on the basis of poly-ethylene glycol (PEG) and an ammonium sulfate solution followed by its thermal lens detection in the extract. The limit of detection is 0.3 μM (20 ng/mL); the lower limit of the analytical range is 0.7 μM (40 ng/mL); the relative standard deviation for the concentrations 1–50 μM makes 1–3% (n = 6, P = 0.95). In the determination of cobalt by spectrophotometry under the same conditions, the detection limit is 10 μM (0.6 μg/mL) and the lower limit of the analytical range is 40 μM (2.5 μg/mL). The precision of thermal lens measurements in PEG solutions is higher in comparison to that in aqueous ones because of the weaker interference of convection in aqueous solutions of PEG.  相似文献   

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