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1.
Nakamura S Wada M Crabtree BL Reeves PM Montgomery JH Byrd HJ Harada S Kuroda N Nakashima K 《Analytical and bioanalytical chemistry》2007,387(6):1983-1990
A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence (POCL) detection and column switching has been
developed for simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA) and related compounds, for example 3,4-methylenedioxyamphetamine,
methamphetamine, and amphetamine, in hair. After digestion of the hair with 1 mol L−1 sodium hydroxide the compounds were extracted with n-heptane and derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. A mixture of hydrogen peroxide and bis(2,4,5-trichloro-6-carbopentoxyphenyl)oxalate
in acetonitrile was used as post-column CL reagent. Calibration plots showed linearity was good (r = 0.999); detection limits were 0.02–0.16 ng mg−1 hair at a signal-to-noise ratio of 3. The precision of the method, as RSD (n = 5), in intra-day and inter-day assays was better than 5.0 and 6.9%, respectively. The proposed method was sufficiently
sensitive to detect low ng mg−1 levels of MDMA and related compounds in hair, and could be used for quantification of the compounds in hair samples from
patients treated in a chemical dependency unit. 相似文献
2.
A survey of contamination of surface and drinking waters around Lake Maggiore in Northern Italy with polar anthropogenic environmental
pollutants has been conducted. The target analytes were polar herbicides, pharmaceuticals (including antibiotics), steroid
estrogens, perfluorooctanesulfonate (PFOS), perfluoroalkyl carboxylates (including perfluorooctanoate PFOA), nonylphenol and
its carboxylates and ethoxylates (NPEO surfactants), and triclosan, a bactericide used in personal-care products. Analysis
of water samples was performed by solid-phase extraction (SPE) then liquid chromatography–triple-quadrupole (tandem) mass
spectrometry (LC–MS–MS). By extraction of 1-L water samples and concentration of the extract to 100 μL, method detection limits
(MDLs) as low as 0.05–0.1 ng L−1 were achieved for most compounds. Lake-water samples from seven different locations in the Southern part of Lake Maggiore
and eleven samples from different tributary rivers and creeks were investigated. Rain water was also analyzed to investigate
atmospheric input of the contaminants. Compounds regularly detected at very low concentrations in the lake water included:
caffeine (max. concentration 124 ng L−1), the herbicides terbutylazine (7 ng L−1), atrazine (5 ng L−1), simazine (16 ng L−1), diuron (11 ng L−1), and atrazine-desethyl (11 ng L−1), the pharmaceuticals carbamazepine (9 ng L−1), sulfamethoxazole (10 ng L−1), gemfibrozil (1.7 ng L−1), and benzafibrate (1.2 ng L−1), the surfactant metabolite nonylphenol (15 ng L−1), its carboxylates (NPE1C 120 ng L−1, NPE2C 7 ng L−1, NPE3C 15 ng L−1) and ethoxylates (NPE
n
Os, n = 3-17; 300 ng L−1), perfluorinated surfactants (PFOS 9 ng L−1, PFOA 3 ng L−1), and estrone (0.4 ng L−1). Levels of these compounds in drinking water produced from Lake Maggiore were almost identical with those found in the lake
itself, revealing the poor performance of sand filtration and chlorination applied by the local waterworks. 相似文献
3.
Summary An isocratic reversed-phase liquid chromatographic method for the simultaneous determination of hypericin and pseudohypericin,
two of the main constituents ofHypericum Perforatum L., has been developed. The compounds were eluted from an Inertsil ODS-3, column by triethylammonium acetate-methanol-acetonirile
(5:15:80) eluent and detected fluorimetrically, excitation 478, emission 598 nm. Hypericin and pseudohypericin were extracted
from flowring tops by Soxhlet and pseudohypericin was isolated from the extract by collecting its chromatographic peak from
the eluent flow. Identification of peaks was by HPLC coupled to a diode array detector and electrospray MS. The method was
applied to the determination of hypericin and pseudohypericin in plant extract and in pharmaceutical tablets. For the latter
a solid-phase extraction procedure was adopted. Riboflavin (0.1 ng.μL−1) was used as internal standard. The linear working range of the method is 0.025–4 ng.μL−1 and limit of detection 0.2 ng injected on-column. A comparative SPE study for hypericin is presented. 相似文献
4.
A simple and rapid flow-injection spectrophotometric method for the determination of iron(III) and total iron is proposed.
The method is based on the reaction between iron(III) and O-acetylsalicylhydroxamic acid (AcSHA) in a 2 % methanol solution resulting in an intense violet complex with strong absorption
at 475 nm. Optimum conditions for the determination of iron(III) and the interfering ions were tested. The relative standard
deviation for the determination of 5 μg L−1 iron(III) was 0.85 % (n = 10), and the limit of detection (blank signal plus three times the standard deviation of the blank) was 0.5 μg L−1, both based on the injection volumes of 20 μL. The method was successfully applied in the determination of iron(III) and
total iron in water and ore samples. The method was verified by analysing a certified reference material Zn/Al/Cu 43XZ3F and
also by the AAS method. 相似文献
5.
Katsu T Tsunamoto Y Hanioka N Komagoe K Masuda K Narimatsu S 《Analytical and bioanalytical chemistry》2007,387(6):2057-2064
S,S,S-Tris(2-ethylhexyl) phosphorotrithioate proved to be an effective solvent mediator for constructing a mexiletine-sensitive
membrane electrode in combination with an ion-exchanger, sodium tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate.
Among a series of phosphorus compounds containing phosphoryl (P=O) groups, this solvent mediator showed the highest sensitivity
to mexiletine in phosphate-buffered physiological saline containing 0.15 mol L−1 NaCl and 0.01 mol L−1 NaH2PO4/Na2HPO4 (pH 7.4), giving a detection limit of 2 × 10−6 mol L−1 with a slope of 58.8 mV decade−1. This is the best reported detection limit of any mexiletine-sensitive electrode developed to date. Owing to its high selectivity
toward inorganic cations, the electrode was used to determine the level of mexiletine in saliva, the monitoring of which is
quite effective for controlling the dose of this drug noninvasively. The mexiletine concentrations determined with the mexiletine-sensitive
electrode compared favorably with those determined by high-performance liquid chromatography. 相似文献
6.
Alaa S. Amin 《Chemical Papers》2009,63(6):625-634
A simple, selective, highly sensitive and accurate procedure for the determination of trace amounts of copper has been developed
based on solid-phase spectrophotometry. Copper reacts with 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) to give a complex
with high molar absorptivity (3.17 × 107 L mol−1 cm−1, 3.07 × 108 L mol−1 cm−1, 1.22 × 109 L mol−1 cm−1, and 1.80 × 109 L mol−1 cm−1), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. The absorbance at
667 nm and 800 nm packed in a 1.0 mm cell was measured directly. Calibration is linear over the range 0.2–3.7 μg L−1 with RSD of < 1.28 % (n = 10). The detection and quantification limits of the 500 mL sample method are 79 ng L−1 and 260 ng L−1 when using 60 mg of Dowex 1-X8. For a 1000 mL sample, the detection and quantification limits are 67 ng L−1 and 220 ng L−1 using 60 mg of the exchanger. Increasing the sample volume can enhance the sensitivity. The proposed method was applied to
the determination of copper in different environmental water samples (tap, pit, spring, and river), food products (rice, corn
flour, and tea), and mushrooms, using the standard addition technique. 相似文献
7.
Patricia W. Stege Lorena L. Sombra Germán A. Messina Luis D. Martinez María F. Silva 《Analytical and bioanalytical chemistry》2009,394(2):567-573
Many aromatic compounds can be found in the environment as a result of anthropogenic activities and some of them are highly
toxic. The need to determine low concentrations of pollutants requires analytical methods with high sensitivity, selectivity,
and resolution for application to soil, sediment, water, and other environmental samples. Complex sample preparation involving
analyte isolation and enrichment is generally necessary before the final analysis. The present paper outlines a novel, simple,
low-cost, and environmentally friendly method for the simultaneous determination of p-nitrophenol (PNP), p-aminophenol (PAP), and hydroquinone (HQ) by micellar electrokinetic capillary chromatography after preconcentration by cloud
point extraction. Enrichment factors of 180 to 200 were achieved. The limits of detection of the analytes for the preconcentration
of 50-ml sample volume were 0.10 μg L−1 for PNP, 0.20 μg L−1 for PAP, and 0.16 μg L−1 for HQ. The optimized procedure was applied to the determination of phenolic pollutants in natural waters from San Luis,
Argentina.
Figure Schematic representation of the cloud point extraction process. 相似文献
8.
A rapid and sensitive capillary electrophoresis (CE) method has been developed for profiling organic metabolites containing
amine functional groups in mammalian biofluids. Metabolites containing an amine group were derivatized with 4-fluoro-7-nitrobenzo-2,1,3-oxadiazol
(NBD-F), separated by micellar electrokinetic chromatography (MEKC), and detected by argon-ion (488 nm) laser-induced fluorescence
detection. The optimized MEKC background electrolyte conditions were: 50 mmol L−1 sodium cholate, 5 mmol L−1 β-cyclodextrin, and 20 mmol L−1 Brij 35 in 20 mmol L−1 aqueous borate buffer, pH 9.3, containing 7% methanol. Under these conditions all the amine compounds in mammalian biofluids,
for example plasma, saliva, and urine, were derivatized directly, without extraction, in a minimum volume of 100 nL and the
derivatives could be separated within 16 min. Up to 90% of the amine-containing metabolites in plasma and saliva could be
identified by reference to standard compounds. For twenty amine standards linearity of calibration was better than R
2 = 0.99. Migration-time and peak-area reproducibility were better than RSD 1.5% and 15% respectively. In replicate analysis
of human plasma bioanalytical precision ranged between 0.7 and 3.8 RSD% for a 5.0-μL volume and between 1.7 and 5.5 RSD% for
100-nL volume. The concentrations measured were found to be in agreement with literature values. 相似文献
9.
A rapid, highly sensitive and selective fluorogenic method for the determination of traces of nitrite is described. It is
based on the reaction of weakly fluorescent 1,3,5,7-tetramethyl-8-(3,4-diaminophenyl)-difluoroboradiaza-s-indacence (DAMBO) and nitrite in acidic aqueous solution to give 1,3,5,7-tetramethyl-8-(5-benzotriazolyl)-difluoroboradiaza-s-indacene (DAMBO-T), which is highly fluorescent. The optimum reaction conditions and other analytical parameters are investigated
to enhance the sensitivity of the method. The fluorescence enhancement at 507 nm is linearly related to the concentration
of nitrite in the range of 6.0 × 10−9–5.0 × 10−7 mol L−1 with a correlation coefficient of R = 0.9995 (n = 10) and a detection limit of 1.0 × 10−10 mol L−1. The R.S.D. is 1.12% (n = 10). The method is applied to the determination of nitrite in human saliva samples with the recoveries of 96. 24–105.30%.
Correspondence: Ke-Jing Huang, Department of Chemistry, Wuhan University, Wuhan 430072, P.R. China 相似文献
10.
Fanjul-Bolado P González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,385(7):1202-1208
p-Nitrophenyl phosphate is one of the most widely used substrates for alkaline phosphatase in ELISAs because its yellow, water-soluble
product, p-nitrophenol, absorbs strongly at 405 nm. p-Nitrophenol is also electroactive; an oxidative peak at 0.97 V (vs. an Ag pseudoreference electrode) is obtained when a bare
screen-printed carbon electrode is used. When an amperometric detector was coupled to a flow-injection analysis system the
detection limit achieved for p-nitrophenol was 2×10−8 mol L−1, almost two orders of magnitude lower than that obtained by measuring the absorbance of the compound. By use of this electrochemical
detection method, measurement of 7×10−14 mol L−1 alkaline phosphatase was achieved after incubation for 20 min. The feasibility of coupling immunoassay to screen-printed
carbon electrode amperometric detection has been demonstrated by performing an ELISA for detection of pneumolysin, a toxin
produced by Streptococcus pneumoniae, which causes respiratory infections. The method is simple, reproducible, and much more sensitive than traditional spectrophotometry. 相似文献
11.
A rapid and inexpensive method for simultaneous quantification of terbumeton (TER), and its major potential metabolites (TED;
terbumeton-desethyl, TOH; terbumeton-2-hydroxy and TID; terbumeton-deisopropyl) in soil bulk water (SBW) samples is proposed.
The analytical method involves extraction–concentration from SBW samples using a graphitized carbon black (GCB) cartridge
followed by their separation–detection by reversed-phase high-performance liquid chromatography analysis using a C18 column and a diode array detector. A mobile phase of acetonitrile−0.005 mol L−1 phosphate buffer (pH 7.0) (35:65, v/v) at a flow rate of 0.8 mL min−1 in isocratic elution mode has been used. After optimization of the extraction and separation conditions, this method can be
used for the simultaneous determination of investigated compounds in the range of the international limits of 0.1 μg L−1. For TER the detection limit was 0.009 μg L−1 and it was 0.100, 0.550, and 0.480 μg L−1 for TED, TOH, and TID, respectively. The recoveries of TER, TED, TOH, and TID from SBW samples, measured at three levels of
concentration range, were found to be between 48.0 and 102.0%. The intra-day precision measured by relative standard deviation
(RSD) was always lower than 9.0%. 相似文献
12.
Huang KJ Zhang M Xie WZ Zhang HS Feng YQ Wang H 《Analytical and bioanalytical chemistry》2007,388(4):939-946
A simple, sensitive, selective, and low-cost method is proposed for rapidly determining nitric oxide (NO) in some rat tissues.
Polymer monolith microextraction (PMME) using a poly(methacrylic acid–ethylene glycol dimethacrylate) (MAA-EGDMA) monolithic
column was combined with derivatization of NO using 1,3,5,7-tetramethyl-8-(3′,4′-diaminophenyl)-difluoroboradiaza-s-indacene (TMDABODIPY), and this was used to analyze the derivatives of NO by high-performance liquid chromatography (HPLC)
with fluorescence detection at λ
ex/λ
em = 498/507 nm. The baseline separation of TMDABODIPY and its NO derivative is performed under simple conditions in which a
C18 column is used and eluted with 50 mmol L−1 ethanolamine and methanol. The conditions for the extraction of NO derivatives were optimized. The limit of detection of
NO was 2 × 10−12 mol L−1 (S/N = 3). The linearity range of the method was 9 × 10−11−4.5 × 10−8 mol L−1. The interday and intraday relative standard deviations were less than 5%. The proposed method was successfully applied to
the determination of NO levels in some rat tissue samples including heart, kidney, and liver with recoveries varying from
87.1 to 95.2%. 相似文献
13.
Summary Capillary electrophoresis with amperometric detection has been evaluated for the simultaneous determination of rutin and quercetin.
The cyclic voltammogram, hydrodynamic voltammogram, and the effects of pH, concentration of buffer and sodium dodecyl sulfate
(SDS), and amount of organic modifier on the separation and the detection were studied. The optimized conditions were: detection
potential 1.2V, separation at 12 kV, 5 s at 15 kV for sample injection, running electrolyte 20 mmol L−1 borate buffer, pH 8.8, containing 40 mmol L−1 SDS and 10% acetonitrile. The detection limit of the method was low, 0.001 and 0.0005 mg mL−1, for rutin and quercetin, respectively; the linear ranges were wide −0.005–0.5 and 0.005–0.4 mg mL−1, respectively. The variations in peak current and migration time for eight consecutive injections of a standard solution
containing 0.1 mg mL−1 of each compound were 4.78 and 3.63%, and 6.50 and 2.59% for rutin and quercetin, respectively. The levels of the two compounds
in traditional Chinese herbal drugs were easily determined. 相似文献
14.
Jinzhang Gao Jing Liu Jie Ren Xiuli Niu Yingying Zhang Wu Yang 《Central European Journal of Chemistry》2009,7(3):298-302
This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn2+-KBrO3-H2SO4. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed
a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L−1 tartrate, 4.0 mL 0.7 mol L−1 H2SO4, 1.5 mL 1.5×10−4 mol L−1 MnSO4, 4.0 mL 0.4 mol L−1 acetone and 7.0 mL 0.05 mol L−1 KBrO3 was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative
logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10−7∼3.75×10−5 mol L−1 with a lower detection limit of 2.50×10−8 mol L−1.
相似文献
15.
J. L. Bernal M. J. Nozal L. Toribio M. L. Serna F. Borrull R. M. Marcé E. Pocurull 《Chromatographia》1997,46(5-6):295-300
Summary The eleven Environmental Protection Agency (EPA) priority phenolic compounds have been determined by solid-phase extraction
(SPE) coupled on-line to supercritical-fluid chromatography (SFC) with diodearray detection. The variables affecting chromatographic
separation were optimized and the analytes were separated at 40 °C in two diol columns connected in series; a gradient of
methanol, as modifier, and CO2 was used as mobile phase. Under these conditions, all the compounds studied were separated to baseline in less than 13 min.
PLRP-S and LiChrolut EN were tested as sorbents in a 10×3 mm i.d. laboratory-packed precolumn for solid-phase extraction.
An ion-pair reagent, tetrabutylammonium bromide (TBA), was used in the extraction process to increase break-through volumes.
The performance of the method was checked with tap and river waters and the pre-concentration of 20 mL of sample in a PLRP-S
pre-column enabled phenolic compounds to be determined at low μg L−1 levels with limits of detection ranging between 0.4 and 2 μg L−1. The repeatability and reproducibility between days (n=3) for real samples spiked at 10 μg L−1 were lower than 10%. 相似文献
16.
Silva Daniel Pereira Pessoa Adalberto Roberto Inês-Conceição Vitolo Michele 《Applied biochemistry and biotechnology》2001,91(1-9):605-613
A batch culture of Saccharomyces cerevisiae for the production of hexokinase was carried out in a 5-L fermentor containing 3 L of culture medium, which was in oculated
with cell suspension (about 0.7 g/L), and left ferm entingat 35°C and pH 4.0. The aeration and agitation were adjusted to
attain k
La values of 15, 60, 135, and 230 h−1. The highest hexokinase productivity (754.6 U/[L h]) and substrate-cell conversion yield (0.21 g/g) occurred for a k
La of 60 h−1. Moreover, the formation of hexokinase and cell growth are coupled events, which is in accordance with the constitutive character
of this enzyme. Hexokinase formation for k
La>60 h−1 was not enhanced probably owing to saturation of the respiratory pathway by oxygen. 相似文献
17.
Dian-Lei Wang Yan Liang Lin Xie Tong Xie X. T. Wang Sen Yu Guang-Ji Wang Xiao-Dong Liu 《Chromatographia》2008,67(3-4):219-224
To evaluate the pharmacokinetics of a novel analogue of ginkgolide B, 10-O-dimethylaminoethylginkgolide B (XQ-1) in rat plasma in pre-clinical studies, a sensitive and specific liquid chromatographic
method with electrospray ionization mass spectrometry detection (LC–ESI–MS) was developed and validated. After a simple extraction
with ethyl acetate, XQ-1 was analyzed on a Shim-pack C18 column with a mobile phase of a mixture of 1 μmol L−1 ammonium acetate containing 0.02% formic acid and methanol (55:45, v/v) at a flowrate of 0.3 mL min−1. Detection was performed in selected ion monitoring (SIM) mode using target ions at [M + H]+
m/z 496.05 for XQ-1 and m/z 432.10 for the internal standard (lafutidine). Linearity was established for the concentration range from 2 to 1,000 ng mL−1 . The extraction recoveries ranged from 86.0 to 89.9% in plasma at concentrations of 5, 50, and 500 ng mL−1. The lower limit of quantification was 2 ng mL−1 with 100 μL plasma. The validated method was successfully applied to a pharmacokinetic study after intragastic administration
of XQ-1 mesylate in rats at a dose of 20 mg kg−1. 相似文献
18.
Vega D Agüí L González-Cortés A Yáñez-Sedeño P Pingarrón JM 《Analytical and bioanalytical chemistry》2007,389(3):951-958
The voltammetric behaviour and amperometric detection of tetracycline (TC) antibiotics at multi-wall carbon nanotube modified
glassy carbon electrodes (MWCNT-GCE) are reported. Cyclic voltammograms of TCs showed enhanced oxidation responses at the
MWCNT-GCE with respect to the bare GCE, attributable to the increased active electrode surface area. Hydrodynamic voltammograms
obtained by flow-injection with amperometric detection at the MWCNT-GCE led us to select a potential value E
det = +1.20 V. The repeatability of the amperometric responses was much better than that achieved with bare GCE (RSD ranged from
7 to 12%), with RSD values for i
p of around 3%, thus demonstrating the antifouling capability of MWCNT modified electrodes. An HPLC method with amperometric
electrochemical detection (ED) at the MWCNT-GCE was developed for tetracycline, oxytetracycline (OTC), chlortetracycline and
doxycycline (DC). A mobile phase consisting of 18:82 acetonitrile/0.05 mol L−1 phosphate buffer of pH 2.5 was selected. The limits of detection ranged from 0.09 μmol L−1 for OTC to 0.44 μmol L−1 for DC. The possibility to carry out multiresidue analysis is demonstrated. The HPLC-ED/MWCNT-GCE method was applied to the
analysis of fish farm pool water and underground well water samples spiked with the four TCs at 2.0 × 10−7 mol L−1. Solid-phase extraction was accomplished for the preconcentration of the analytes and clean-up of the samples. Recoveries
ranged from 87 ± 6 to 99 ± 3%. Under preconcentration conditions, limits of detection in the water samples were between 0.50
and 3.10 ng mL−1. 相似文献
19.
By alternate use of two different extraction solvents, n-hexadecane and benzyl alcohol, a headspace-solvent microextraction (HSME)–GC–FID/MS method has been established for characterization
of the volatile components of an orange juice beverage. The method avoids two disadvantages of conventional HSME—difficulty
identifying components obscured by the solvent peak and inefficient extraction of some of the compounds if one solvent only
is used. The optimum conditions (droplet volume, equilibration temperature and time, extraction time, and ionic strength)
were determined by the factor-rotation method. The volatile components of the beverage were mainly terpenes, terpenols, fatty
acids, and alcohols, for example limonene (114.71 mg L−1), phellandrene (4.50 mg L−1), terpineol (p-menth-1-en-8-ol; 3.12 mg L−1), α-pinene (0.33 mg L−1), n-hexadecanoic acid (0.28 mg L−1), and terpinol (0.13 mg L−1). 相似文献
20.
Hollow fibre based liquid phase microextraction (HF-LPME) with high performance liquid chromatography (HPLC) was developed
for the determination of alkaloids in Corydalis yanhusuo. Three alkaloids (protopine, tetrahydropalmatine, tetrahydroberberine) were extracted from a 10 mL alkaline sample (donor
phase) to an organic phase impregnated in the pores of the hollow fibre, and then, they were extracted to an acidic solution
(acceptor phase) in the lumen of the fibre. The extract was determined directly by HPLC. Parameters affecting the HF-LPME
include the organic solvent, pH of the donor and the acceptor phase, the extraction time and the stirring speed were investigated
systematically. To minimize the error of the injection, palmatine was added as an internal standard (I.S.). Under optimal
conditions, calibration curves were obtained in the range of 0.1–1.0 mg L−1 with a reasonable linearity (r
2 > 0.993) and the limits of detection (LODs) ranged between 10.0 × 10−3 mg L−1 and 13.7 × 10−3 mg L−1. Additionally, enrichment factors with 100 to 184-fold were obtained. The method was then applied to the crude extract of
Corydalis yanhusuo successfully. 相似文献