Micellar electrokinetic capillary chromatography was used for the determination of picoxystrobin and pyraclostrobin. The background electrolyte consisted of borate buffer (40 mmol L−1 pH 8.5), SDS (30 mmol L−1) and acetonitrile (15% in volume). Runs were made at 25 °C with 25 kV applied potential. The developed method was applied to analyte fortified urine samples. On-line analyte concentration, combined with a capillary of a longer optical path length, allowed limits of quantification of 8.6 × 10−8 mol L−1 for picoxystrobin and 1.8 × 10−7 mol L−1 for pyraclostrobin.
相似文献A method for isotachophoretic determination of potassium and ammonium cations in fertilizers and silage was developed. A capillary of 0.4 mm i.d. and 100 mm effective length made of fluorinated ethylene–propylene copolymer was filled with an electrolyte system consisting of 10 mmol L−1 RbOH + 0.1% (w/v) hydroxyethylcellulose, adjusted to pH 9.0 with l-histidine (leading electrolyte) and 10 mmol L−1 lithium citrate (terminating electrolyte). Using contactless conductivity detection, the calibration curves in the tested concentration range up to 0.5 mmol L−1 were linear for both cations. The concentration detection limits for potassium and ammonium were 2.9 and 2.7 μmol L−1, respectively. RSD values of step lengths (n = 6) were 1.3% for potassium and 1.5% for ammonium. The separation time was about 20 min. Similar results were obtained with cesium cation used as the leading ion, however, in the system with rubidium better resolution of other cations present in tested matrices was reached. The elaborated method is simple to perform, sufficiently sensitive and accurate and can be recommended as an alternative procedure to the methods used so far for the determination of potassium and ammonium.
相似文献An alternative methodology for simultaneous determination of isoniazid, isonicotinic acid, 4-cyanopyridine, ethyl isonicotinate and isonicotinamide by capillary zone electrophoresis, within an analysis time of 11 min, is proposed. An electrolyte composed by 50 mmol L−1 of acetic acid/sodium acetate buffer and 12.5 mmol L−1 of Cu2+, an analyte dilution in 1 mmol L−1 of Brij 35 and 12.5 mmol L−1 of Cu2+ and +20 kV voltage were optimized. After evaluating some figures of merit, such as linearity, precision, recovery and quantification limit, the method was successfully applied to the isoniazid analysis in tablets. The contents found were 99.3 mg of isoniazid and 0.3 mg of isonicotinic acid, corresponding to 0.3 % of impurity regarding the content of the active ingredient in the pharmaceutical formulation.
相似文献A sensitive and selective method for simultaneous determination of 29 toxic alkaloids in human blood and 31 in urine using high-performance liquid chromatography–electrospray ionization-tandem mass spectrometry was developed and validated. The samples were diluted with 0.1 mol L−1 HCl, and the target alkaloids were purified by solid phase extraction. The separation of 31 alkaloids was carried out on a C18 column using a gradient mobile phase with 10 mmol L−1 ammonium formate in water with 0.1% formic acid and methanol at the rate of 0.25 mL min−1. The triple-quadrupole mass spectrometer equipped with an electrospray source in the positive mode was set up in the dynamic multiple reactions monitoring mode (dynamic MRM) to detect the ion transitions of 31 alkaloids. The calibration curves were linear over a range of 0.5–400, 1–400, or 4–400 μg L−1 for target alkaloids in human blood and urine, and the correlation coefficients (r 2) was higher than 0.9943. The limit of determination and limit of quantification were 0.2–1 and 0.5–4 μg L−1 for blood and urine, respectively. The only exceptions were sanguinarine and chelerythrine in human blood. All the target alkaloids were stable under the test condition. In addition, the solvent effect and reconstituted solution were investigated. The method was validated and proved to be accurate and precise over the studied concentrations and suitable for poisoning diagnosis and forensic toxicology.
相似文献A simple and mild method for the determination of fatty acids (C1 – C10) based on a condensation reaction using 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) as labeling reagent with capillary zone electrophoresis has been developed. The detection was performed with a diode array detector at 254 nm. A 58.5 cm × 50 μm i.d. (50 cm effective length) untreated fused-silica capillary was used. To optimize the separation conditions, the background electrolyte concentration, column temperature, voltage and other factors were evaluated. The optimal separation conditions were as follows: 30 mmol L−1 borate buffer (pH 9.5), 15 mmol L−1 β-CD, temperature at 20 °C, pressure 50 mbar and injection time 8 s. Under the established conditions, 10 fatty acid derivatives could be well-separated within 17 min. The linearity was in the range of 0.07–5.0 μmol L−1. Detection limits (at a signal-to-noise ratio of 3) were in the range of 0.027–0.042 μmol L−1. The fatty acids from the extracted Funaria Hedw. and Selaginella samples were determined with satisfactory results.
相似文献In this study, a method of field-amplified sample injection coupled with capillary zone electrophoresis with ultraviolet detection was established for evaluation of DNA methylation and hydroxymethylation levels in biological materials. By modifying an existing method, the separation of cytosine (C), 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) was performed on an uncoated capillary column (40 cm × 75 μm I.D.) using 300 mmol L−1 tris solution (pH 2.90) as running buffer and detected at 280 nm. The detection limits (S/N = 3) of the method were 0.004 ng mL−1 for cytosine (C), 0.01 ng mL−1 for 5-methylcytosine (5-mC), and 0.02 ng mL−1 for 5-hydroxymethylcytosine (5-hmC). The proposed method has been successfully applied to the evaluation of DNA methylation and hydroxymethylation levels of blood samples from 15 hepatocellular carcinoma patients and 5 liver cirrhosis patients and liver tissues from 50 pairs of tumor and matched tumor-adjacent samples.
相似文献How to determine the quantities of acrylamide produced in foods is an important problem. Here, we report a sensitive method of high performance liquid chromatography based on a solid phase extraction using a reversed phase C18 column, which was characterized by adsorption experiments with good adsorption ability and rapid adsorption dynamic toward acrylamide. Under optimal condition, the detection limit based on three times the signal-to-noise ratio of the baseline near the analyte peak was 66.0 ng L−1. With a loading flow rate of 2.0 mL min−1 for loading 100 mL, an enrichment factor of 182 was obtained. The RSD for five replicate extractions of 50 μg L−1 acrylamide was 4.1%. Blank potato samples spiked with acrylamide at 0.125, 0.250, and 0.375 μg g−1 levels were analyzed with recoveries ranging from 88.9 to 89.5%. Moreover, this method was applied to quantitative detection of acrylamide in the crust and potato chip samples.
相似文献Wilforidine is a potentially efficient medicine to cure autoimmune diseases. In this paper, a sensitive and selective liquid chromatographic method coupled with atmospheric -pressure chemical ionization mass spectrometry (LC–APCI–MS/MS) has been developed for quantification of wilforidine in human plasma. Samples were deproteinized with acetonitrile and cleaned by solid-phase extraction. The chromatographic separation was performed on an analytical RRHD C18 column (50 × 2.1 mm) using ammonium acetate solution (10.0 mmol L−1)/acetonitrile (30/70, v/v) as the mobile phase at a flow rate of 0.7 mL min−1. Detection was carried out by the positive multiple reaction monitoring mode with transitions of m/z 780 → 684 for wilforidine, and 646 → 586 for aconitine (internal standard), respectively. The calibration curve was linear (r = 0.9991) in the concentration range of 0.5–100.0 μg L−1 with a lower limit of quantification of 0.5 μg L−1 in plasma. Intra- and inter-day relative standard deviations were less than 6.8 and 13.1 %, respectively, and the recoveries were between 88.0 and 96.0 %. This accurate and highly specific assay provides a useful method for evaluating the pharmacokinetics of wilforidine in human plasma.
相似文献The objective of this work has been to assess the potential of capillary isotachophoretic organic acids profiling using multivariate statistical methods to classify brandy samples and wine distillate samples. The leading electrolyte was 10 mmol L−1 hydrochloric acid including 0.1% methylhydroxylethylcellulose adjusted with β-alanine to pH 2.9. The terminating electrolyte was 5 mmol L−1 acetic acid. Principal component analysis, cluster analysis, and linear discriminant analysis were used for the classification of beverages. The results show that for the 12 acids analysed, 98.57% of the total variance is extracted by the six principal components (PC). After performing backward linear discriminant analysis, a classification function was obtained containing four variables: formic (PC2-loadings: 0.989), lactic (PC1-loadings: 0.886), malic (PC1-loadings: 0.989) and oxalic (PC2-loadings: 0.777) acids, which provide 100.0% correct classification of brandies and wine distillates.
相似文献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.
相似文献Taurine is an amino acid which is not incorporated into proteins but found in the cytosol of many mammalian cells, in high concentrations (2–30 mM). Increase in plasma taurine concentration has already been reported after surgical trauma, X-radiation, muscle necrosis, carbon tetrachloride-induced liver damage, and paracetamol overdose. Plasma taurine concentration was measured using LC with fluorescence detection following derivatization by o-phtalaldehyde plus 3-mercapto-propionic acid and α-aminobutyric acid as internal standard. Under these conditions the retention time of taurine was 10 min. This method was sensitive enough, to quantify 150 pg mL−1 and detect 50 pg mL−1 of taurine ranging normally between 65 and 179 mmol L−1 (8–22 μg mL−1). The validated method allowed simple determination of human plasma taurine in pharmacokinetic and biomarker studies.
相似文献Imatinib, bosutinib, dasatinib, pazopanib, erlotinib, canertinib and vatalanib are new developed anticancer drugs, especially for treatment of leukemia. In this article, a fast and high throughput capillary zone electrophoresis method has been developed and validated for analysis of these new drugs in pharmaceutical formulas. The method can be easily utilized for determination of all the drugs in one run what is advantageous for the quality control in pharmaceutical industry because there is no need for changing and optimization of separation conditions when changing the analyte. The separation was performed using an uncoated fused silica capillary with 100 mmol L−1 sodium phosphate buffer pH 2.75, voltage of 25 kV, hydrodynamic injection time of 5 s by 50 mbar, and detection at 214 nm. Under these conditions, the analysis took about 8 min. The validation of all the drugs resulted in recoveries in the range of 84–100 %. The method showed to be precise for all the drugs with RSDs of migration times lower than 0.9 % (interday precision). A very good linearity in the validated range (5–100 μg mL−1) and the limits of detection (LODs) in the range of 0.5–2.0 (μg mL−1) were achieved. Finally, we proved that the method is robust by the Youden’s test. Therefore, our method can be successfully applied for analysis of the real pharmaceutical samples.
相似文献Rapid, inexpensive, and efficient sample-preparation by dispersive liquid–liquid microextraction (DLLME) then gas chromatography with flame ionization detection (GC–FID) have been used for extraction and analysis of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in water samples. In this extraction method, a mixture of 25.0 μL carbon disulfide (extraction solvent) and 1.00 mL acetonitrile (disperser solvent) is rapidly injected, by means of a syringe, into a 5.00-mL water sample in a conical test tube. A cloudy solution is formed by dispersion of fine droplets of carbon disulfide in the sample solution. During subsequent centrifugation (5,000 rpm for 2.0 min) the fine droplets of carbon disulfide settle at the bottom of the tube. The effect of several conditions (type and volume of disperser solvent, type of extraction solvent, extraction time, etc.) on the performance of the sample-preparation step was carefully evaluated. Under the optimum conditions the enrichment factors and extraction recoveries were high, and ranged from 122–311 to 24.5–66.7%, respectively. A good linear range (0.2–100 μg L−1, i.e., three orders of magnitude; r 2 = 0.9991–0.9999) and good limits of detection (0.1–0.2 μg L−1) were obtained for most of the analytes. Relative standard deviations (RSD, %) for analysis of 5.0 μg L−1 BTEX compounds in water were in the range 0.9–6.4% (n = 5). Relative recovery from well and wastewater at spiked levels of 5.0 μg L−1 was 89–101% and 76–98%, respectively. Finally, the method was successfully used for preconcentration and analysis of BTEX compounds in different real water samples.
相似文献A simple, rapid and sensitive LC–MS/MS method in positive ion mode was developed and validated to determine CKD-501, lobeglitazone, in human plasma and urine using glipizide as an internal standard (IS). Lobeglitazone is a novel thiazolidinedione (TZDs)-based peroxisome proliferator-activated receptor (PPAR) agonist, used for the management of type-2 diabetes. After mixing the IS, dissolved in acetonitrile, with a plasma or urine sample containing lobeglitazone, 10 μL of supernatant was injected into the LC–MS/MS system. Quantification was performed in the multiple reaction monitoring (MRM) mode using transition of 481.5 → 152.2 (m/z) for lobeglitazone and 446.1 → 321.2 (m/z) for the IS. The method showed good linearity over concentration ranges of 0.5–1,000 ng mL−1 for plasma and 0.2–250 ng mL−1 for urine (r 2 ≥ 0.9996). The mean percent extraction recovery of lobeglitazone was 90.8 % for plasma and 87.3 % for urine, while the recoveries of the IS were greater than 86.4 % for both. The intra-day and inter-day precision of plasma ranged from 1.1 to 3.7 and 2.5 to 3.3 % (RSD), respectively, and the intra- and inter-day precision of urine ranged from 1.5 to 2.7 and 3.2 to 3.5 %, respectively. This method is simple, sensitive, and applicable for the pharmacokinetic study of lobeglitazone in human plasma. Most of the urine concentrations of lobeglitazone were below the LLOQ because the lobeglitazone is extensively metabolized.
相似文献Stereoselective CE method for investigations of pharmacokinetics of ketoprofen enantiomers (KTP) in patients taking also other drugs is proposed, to establish relation between levels of KTP enantiomers in blood and synovial fluid of patients with rheumatoid arthritis. Resolution of the analytes was obtained in silica capillary filled with chiral selector-heptakis 2,3,6-tri-O-methyl–β-cyclodextrin in triethanolamine-phosphate buffer. Calibration curves for enantiomers in plasma and synovial fluid were linear in the range of 0.25–50.0 mg L−1, but 1.0–250.0 mg L−1 in urine. Concentrations of KTP enantiomers in synovial fluid measured at 4 h after the administration of a tablet with racemic KTP were insignificantly greater [(−)-R = 1.07 ± 0.66; (+)-S-KTP = 1.13 ± 0.65 mg L−1] than in plasma [(−)-R = 0.86 ± 0.37; (+)-S-KTP = 0.96 ± 0.42 mg L−1]. The validated method has been successfully applied for the determination of KTP enantiomers in biological fluids of patients with rheumatoid arthritis.
相似文献A simple, sensitive and accurate method was developed for solid-phase extraction and preconcentration of trace levels of gold in various samples. It is based on the adsorption of gold on modified oxidized multi-walled carbon nanotubes prior to its determination by graphite furnace atomic absorption spectrometry. The type and volume of eluent solution, sample pH value, flow rates of sample and eluent, sorption capacity and breakthrough volume were optimized. Under these conditions, the method showed linearity in the range of 0.2–6.0 ng L−1 with coefficients of determination of >0.99 in the sample. The relative standard deviation for seven replicate determinations of gold (at a level of 0.6 ng L−1) is ±3.8 %, the detection limit is 31 pg L−1 (in the initial solution and at an S/N ratio of 3; for n = 8), and the enrichment factor is 200. The sorption capacity of the modified MWCNTs for gold(III) is 4.15 mg g−1. The procedure was successfully applied to the determination of gold in (spiked) water samples, human hair, human urine and standard reference material with recoveries ranging from 97.0 to 104.2 %.
A sorbent based on modified carbon nanotubes was prepared and used to extract gold ion from various samples prior to its determination by graphite furnace atomic absorption spectrometry