共查询到20条相似文献,搜索用时 171 毫秒
1.
A simple, sensitive and continuous on-line stacking technique using head-column (HC)-field amplified sample injection (FASI)
and sweeping was developed by combination of flow injection with micellar electrokinetic chromatography. Berberine, palmatine
and jatrorrhizine were selected as model mixture to demonstrate this stacking method. Based on the characteristic of a 16-way
injection valve (16-V), a sample was injected electrokinetically into a capillary after the introduction of a plug of water.
Under optimum conditions, 64–86-fold improvement in the detection sensitivity was obtained for the analytes and the sample
throughput can reach up to 24 h−1 using the background electrolyte containing 240 mM ammonium acetate (pH 4.7), 30% (v/v) ethanol, and 2% (v/v) polyoxyethylene
sorbitan monolaurate (Tween 20). The repeatabilities (n = 4) reached relative standard deviation values of 1.2, 2.7 and 3.1% for the peak areas and 1.6, 3.3 and 3.8% for peak heights
of berberine, palmatine and jatrorrhizine, respectively. The limit of detection for the berberine, palmatine and jatrorrhizine
was found to be 27, 26, 22 ng mL−1 (S/N = 3). 相似文献
2.
Enantioseparations of racemic nonsteroidal anti-inflammatory drugs (naproxen, ibuprofen, ketoprofen, flurbiprofen, suprofen,
indoprofen, cicloprofen, and carprofen) were performed by nano-liquid chromatography, employing achiral capillary columns
and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) or hydroxylpropyl-β-cyclodextrin (HP-β-CD) as a chiral mobile phase additive (CMPA). Working
under the same experimental conditions (in terms of mobile phase and linear velocity), the performance of a RP-C18 monolithic
column was compared with that of a RP-C18 packed column of the same dimensions (100 μm i.d. × 10 cm). Utilizing a mobile phase
composed of 30% ACN (v/v) buffered with 50 mM sodium acetate at pH 3, and containing 30 mM TM-β-CD, the monolithic column
provided faster analysis but lower resolution than the packed column. This behavior was ascribed to the high permeability
of the monolithic column, as well as to its minor selectivity. HP-β-CD was chosen as an alternative to TM-β-CD. Employing
the monolithic column, the effects of different parameters such as HP-β-CD concentration, mobile phase composition, and pH
on the retention factor and the chiral resolution of the analytes were studied. For the most of the analytes, enantioresolution
(which ranged from R
s = 1.80 for naproxen to R
s = 0.86 for flurbiprofen) was obtained with a mobile phase consisting of sodium acetate buffer (25 mM, pH 3), 10% MeOH, and
15 mM HP-β-CD. When the same experimental conditions were used with the packed column, no compound eluted within 1 h. Upon
increasing the percentage of organic modifier to favor analyte elution, only suprofen eluted within 30 min, with an R
s value of 1.14 (20% MeOH). Replacing MeOH with ACN resulted in a loss of enantioresolution, except for naproxen (R
s = 0.89). 相似文献
3.
Alaa S. Amin 《Mikrochimica acta》2000,134(1-2):89-94
A simple, rapid, accurate and sensitive spectrophotometric method for the determination of norfloxacin (NRF), ofloxacin (OFL)
and ciprofloxacin (CPF) is described. This method is based on the formation of an ion pair with sudan III in aqueous-acetone
medium [40% (v/v) acetone]. The coloured products are measured at 567, 565 and 566 nm for NRF, OFL and CPF, respectively.
The optimization of various experimental conditions is described. Beer’s law is obeyed in the range 0.4–12.0, 0.4–8.8 and
0.4–10.4 ;μg mL−1 of NRF, OFL and CPF, respectively. For more accurate results, Ringbom optimum concentration ranges were 0.8–11.2, 0.6–8.5
and 0.8–10.0 μg mL−1, respectively. The results obtained showed good recoveries of ±1.2, ±1.5 and ±1.7% with relative standard deviations of 0.67,
0.83 and 1.08% for NRF, OFL, and CPF, respectively. The molar absorptivity and Sandell sensitivity were also calculated. Applications
of the proposed method to representative pharmaceutical formulations are successfully presented.
Received April 30, 1999. Revision November 25, 1999. 相似文献
4.
Chang-Ching Lin Chien-Wen Kuo Li-Heng Pao 《Analytical and bioanalytical chemistry》2010,398(2):857-865
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
5.
A liquid chromatography–chemiluminescence detection method was developed and validated for the determination of catecholamines
(norepinephrine, epinephrine, and dopamine) in mouse brains. Chromatography was performed on a strong cation exchange column
(150 × 2.0-mm id) using an isocratic mobile phase of 65 mM potassium acetate/75 mM potassium phosphate (95:5, pH 3.5) at a
flow rate of 0.2 mL/min following post-column fluorescence derivatization of catecholamines with ethylenediamine and peroxyoxalate
chemiluminescence reaction detection. The recovery of catecholamines added to mouse brain samples was more than 95.0%, while
intra- and inter-day precision of the assay were <4.8%. The validated method was used to determine norepinephrine and dopamine
concentrations in mouse brains without prior sample purification. 相似文献
6.
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
7.
Fathalla Belal Saadia M. El-Ashry Ihsan M. Shehata Magda A. El-Sherbeny Dina T. El-Sherbeny 《Mikrochimica acta》2000,135(3-4):147-154
A highly sensitive differential-pulse (DPP) polarographic method is described for the determination of three N-substituted
phenothiazine derivatives, chlorpromazine (CZ), promazine (PZ) and promethazine (PMZ). The method involves the use of nitrous
acid as an oxidant. Polarographically-active sulphoxides with diffusion-current constants (Id) of 2.53, 3.05 and 3.37 were
obtained for CZ, PZ and PMZ, respectively. The polarographic waves were characterized as being diffusion-controlled, irreversible
and partly affected by adsorption phenomena. All parameters affecting the oxidation process and polarographic behaviour were
optimized and incorporated into the procedure. The limiting current-concentration plots in the DPP mode were rectilinear over
the range: 0.006–0.1 mM, 0.005–0.08 mM and 0.008–0.1 mM for CZ, PZ and PMZ, respectively, with minimum detectability (S/N=3)
of 3 × 10−7 M for CZ and PZ, and 4 × 10−7 M for PMZ, respectively. The kinetic parameters of the electrode reaction, including rate constant, free energy of activation
ΔG and effect of temperature on both parameters were studied. The proposed method was successfully applied to the determination
of phenothiazines in dosage forms; the results obtained were in agreement with those given with the official methods. The
method was further applied to the determination of promazine in spiked human urine. The percentage recovery was 96.86 ± 0.30.
The advantages of the proposed method over other reported methods were discussed. A proposal of the electrode reaction was
made.
Received June 1, 1999. Revision March 10, 2000. 相似文献
8.
A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol (40–60 °C) states at various
concentrations (0.5, 1, 5, 10 and 15 mM) of anionic surfactant, sodium dodecyl sulfate (SDS). The in-phase collective stretching
mode vibration of hydrogen-bonded -OH oscillators, centered around 3250 cm−1 in a tetrahedral network of water molecules, was observed to be significantly affected by temperature and the presence of
SDS. According to our observation this may be due to the thinning of the hydration water around the gelatin molecules due
to strong thermal agitation. The peak center of the collective bands of water decreased linearly with SDS concentration in
the gel state which implied that with the increase in concentration of SDS, the -OH oscillators gradually lost their attachment
to gelatin chains and were replaced by SDS molecules. Ultimately this resulted in a thinning of the hydration layer around
the gelatin and the oscillation frequency of -OH oscillators moved towards 3250 cm−1 at 1 mM SDS concentration resulting in increased coupling of -OH oscillators to form the tetrahedral network at the critical
micelle concentration (cmc) of SDS. The variation in the peak amplitudes and the systematic reversal of their trend about
the cmc axis was surprising. At 40 °C the amplitude of the peak at 3250 cm−1 increased drastically due to a possible coil expansion by about 7–8% which accommodated more interstitial water into the
pseudonetwork leading to an increase in the number of nearest neighbors and for about 6% increase in the C value. However, at the cmc the peak amplitude was observed to be independent of temperature. Continuous shifting of the peak
center and full width at half-maxima towards lower values was observed with increasing SDS concentrations in the gel state.
Received: 28 September 1998 Accepted in revised form: 8 March 1999 相似文献
9.
A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco LC-8, LC-18, LC-SCX, and LC-WCX, as well as Strata-X and X-C). DOX was determined on a 56 cm (effective length 50 cm) x 50 microm id fused-silica capillary. The BGE was 20 mM borate buffer, pH 9.3, containing 80 mM SDS and 7.5% v/v of methanol (30 sx50 mbar), and the temperature and voltage were 25 degrees C and 30 kV, respectively. The analytical wavelength was set at 210 nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1 microg/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80 mM of SDS, 10% v/v of methanol and 40 mM borate buffer (pH 9.3; 30 s x 50 mbar; 25 degrees C; 30 kV; 350 nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition. 相似文献
10.
Mário A. P. Nunes Hélder Vila-Real Pedro C. B. Fernandes Maria H. L. Ribeiro 《Applied biochemistry and biotechnology》2010,160(7):2129-2147
A synthetic polymer, polyvinyl alcohol (PVA), a cheap and nontoxic synthetic polymer to organism, has been ascribed for biocatalyst
immobilization. In this work PVA–alginate beads were developed with thermal, mechanical, and chemical stability to high temperatures
(<80 °C). The combination of alginate and bead treatment with sodium sulfate not only prevented agglomeration but produced
beads of high gel strength and conferred enzyme protection from inactivation by boric acid. Naringinase from Penicillium decumbens was immobilized in PVA (10%)–alginate beads with three different sizes (1–3 mm), at three different alginate concentrations
(0.2–1.0%), and these features were investigated in terms of swelling ratio within the beads, enzyme activity, and immobilization
yield during hydrolysis of naringin. The pH and temperature optimum were 4.0 and 70 °C for the PVA–alginate-immobilized naringinase.
The highest naringinase activity yield in PVA (10%)–alginate (1%) beads of 2 mm was 80%, at pH 4.0 and 70 °C. The Michaelis
constant (K
Mapp) and the maximum reaction velocity (V
maxapp) were evaluated for both free (K
Mapp = 0.233 mM; V
maxapp = 0.13 mM min−1) and immobilized naringinase (K
Mapp = 0.349 mM; V
maxapp = 0.08 mM min−1). The residual activity of the immobilized enzyme was followed in eight consecutive batch runs with a retention activity
of 70%. After 6 weeks, upon storage in acetate buffer pH 4 at 4 °C, the immobilized biocatalyst retained 90% of the initial
activity. These promising results are illustrative of the potential of this immobilization strategy for the system evaluated
and suggest that its application may be effectively performed for the entrapment of other biocatalysts. 相似文献
11.
Tsai IL Liu HY Kuo PH Wang JY Shen LJ Kuo CH 《Analytical and bioanalytical chemistry》2011,401(7):2205-2214
Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis, infects approximately one third of the current world population. Isoniazid is one of the most frequently used first-line
anti-TB drugs. In this study, we developed a sensitive cation-selective exhaustive injection–sweeping–micellar electrokinetic
chromatography method (CSEI-Sweep-MEKC) for analyzing isoniazid in human plasma. Parameters including acetonitrile (ACN) percentage
in the separation buffer; the injection time, and concentration of the high-conductivity buffer; sodium dodecyl sulfate (SDS)
concentration; phosphate concentration in the sample matrix; and the sample injection time were all optimized to obtain the
best analytical performance. The optimal background electrolyte comprised 50 mM phosphate buffer, 100 mM SDS, and 15% ACN.
Non-micelle background electrolyte, containing 75 mM phosphate buffer and 15% ACN, was first injected into the capillary,
followed by a short plug of 200 mM phosphate (high-conductivity buffer). Run-to-run repeatability (n = 3) and intermediate precision (n = 3) of peak area ratios were found to be lower than 8.7% and 11.4% RSD, respectively. The accuracy of the method was within
98.1–106.9%. The limit of detection of isoniazod in human plasma was 9 ng mL−1. Compared with conventional MEKC, the enhancement factor of the CSEI-Sweep-MEKC method was 85 in plasma samples. The developed
method was successfully used to determine isoniazid concentration in patient plasma. The results demonstrated that CSEI-Sweep-MEKC
has the potential to analyze isoniazid in human plasma for therapeutic drug monitoring and clinical research. 相似文献
12.
Lottmann A Cadé E Geagea ML Delhomme O Grand C Veilleraud C Rizet AL Mirabel P Millet M 《Analytical and bioanalytical chemistry》2007,387(5):1855-1861
In to order increase sensitivity and to reduce the background induced by matrix effects, a method was developed that uses
flash chromatography to separate various compounds present in atmospheric aerosol samples prior to their analysis with different
analytical techniques (GC–MS, GC–FID, HPLC). For this purpose, flash chromatography using a 4 g silica gel column crossed
by eluent at a flow rate of 20 mL min−1 was used. An eluent with enhanced polarity is needed to separate nonpolar (linear and branched alkanes), semipolar (PAH,
nitro-PAH and cholesterol) and polar (methoxyphenols, alkanoic acids, and levoglucosan) compounds. Three combinations of solvents
were used: hexane for the nonpolar fraction (F1), toluene/hexane for the semipolar fraction (F2) and dimethylformamide for
the polar fraction (F3). The use of different eluents for each fraction allows separation of the sample to be accomplished
with good repeatability and satisfying yields [85 ± 5% for F1, 81 ± 8% (PAHs), 89 ± 6% (nitro-PAHs) and 74 ± 7% (cholesterol)
for F2 and 79 ± 7% (n-alkanoic acids), 40 ± 11% (methoxyphenols) and 77 ± 6% (levoglucosan) for F3]. The methoxyphenol yields were low due to losses
during the concentration/evaporation step. This method was then applied to analyse the organic composition of particles collected
at an urban site in Strasbourg (France). 相似文献
13.
Femina Rauf Yiding Huang Thusitha P. Muhandiramlage Craig A. Aspinwall 《Analytical and bioanalytical chemistry》2010,397(8):3359-3367
A cell-penetrating, fluorescent protein substrate was developed to monitor intracellular protein kinase A (PKA) activity in
cells without the need for cellular transfection. The PKA substrate (PKAS) was prepared with a 6×histidine purification tag,
an enhanced green fluorescent protein (EGFP) reporter, an HIV-TAT protein transduction domain for cellular translocation and
a pentaphosphorylation motif specific for PKA. PKAS was expressed in Escherichia coli and purified by metal affinity chromatography. Incubation of PKAS in the extracellular media facilitated translocation into
the intracellular milieu in HeLa cells, βTC-3 cells and pancreatic islets with minimal toxicity in a time and concentration
dependent manner. Upon cellular loading, glucose-dependent phosphorylation of PKAS was observed in both βTC-3 cells and pancreatic
islets via capillary zone electrophoresis. In pancreatic islets, maximal PKAS phosphorylation (83 ± 6%) was observed at 12 mM
glucose, whereas maximal PKAS phosphorylation (86 ± 4%) in βTC-3 cells was observed at 3 mM glucose indicating a left-shifted
glucose sensitivity. Increased PKAS phosphorylation was observed in the presence of PKA stimulators forskolin and 8-Br-cAMP
(33% and 16%, respectively), with corresponding decreases in PKAS phosphorylation observed in the presence of PKA inhibitors
staurosporine and H-89 (40% and 54%, respectively). 相似文献
14.
Sheng-da Qi Shun-lian Tian Hong-xi Xu Joseph J. Y. Sung Zhao-xiang Bian 《Analytical and bioanalytical chemistry》2009,393(8):2059-2066
Serotonin (5-hydroxytryptamine, 5-HT) plays vital roles in regulating gastrointestinal functions. Thus, the detection of 5-HT
in the gastrointestinal tract is of great importance for biomedical research, medical diagnosis, and pharmaceutical therapy.
This paper presents a simple, sensitive, and fast method for the quantification of luminally released serotonin in the feces
and tissues of the rat proximal colon by means of capillary electrophoresis with laser-induced fluorescence detection. 5-Carboxyfluorescein
N-succinimidyl ester was used for precolumn derivatization of serotonin. The optimal separation and detection conditions were
obtained with an electrophoretic buffer containing 60 mM borate (pH 8.90) and an air-cooled argon-ion laser (excitation at
488 nm, emission at 520 nm). The serotonin concentrations in the feces and tissues of proximal colons were analyzed with this
method, and the average values of serotonin in the feces samples were 1.951 ± 0.446 ng/mg (male) and 2.095 ± 0.533 ng/mg (female)
and 1.397 ± 0.267 ng/mg in rat proximal colon tissues. The results demonstrate that this method can accurately determine luminally
released 5-HT in rats. 相似文献
15.
I. López-García E. Navarro P. Viñas M. Hernández-Córdoba 《Analytical and bioanalytical chemistry》1997,357(6):642-646
A method is proposed for the determination of Pb, Cd and Tl in cements by ETAAS. The samples are suspended in a medium containing
10% v/v ethanol and 1% v/v both conc. nitric and hydrofluoric acids and are directly introduced into the electrothermal atomizer.
The drying stage is performed by programming a 400 °C temperature, a ramp time of 5 s and a hold time of 30 s on the power
supply to the atomizer. No ashing step is used. Atomization is carried out at 2100, 1800 and 1700 °C for Pb, Cd and Tl, respectively.
For Cd determination, ammonium dihydrogen phosphate is added to the suspension medium. No modifier other than hydrofluoric
acid is required for the Pb and Tl determination. It is shown that the results obtained by using direct calibration with aqueous
standards for five commercial samples agree with those found by means of the standard additions method.
Received: 29 March 1996/Revised: 24 May 1996/Accepted: 30 May 1996 相似文献
16.
A simple, sensitive, and useful concentration method for lovastatin (Lvt) in urine has been developed based on the transient
moving chemical reaction boundary method (tMCRBM) in capillary electrophoresis. The MCRB is formed with acidic sample buffer
(Gly-HCl) and alkaline running buffer (Gly-NaOH). The following optimal conditions were determined for stacking and separation:
electrophoretic buffer of 100 mM Gly- NaOH (pH 11.52), sample buffer of 20 mM Gly-HCl (pH 4.93), fused-silica capillary of
76 cm × 75-μm i.d (67 cm from detector), sample injection at 14 mbar for 3 min. A 21- to 26-fold increase in peak height was
achieved for detection of Lvt in urine under the optimal conditions compared with normal capillary zone electrophoresis. By
combining the sample pretreatment procedure with the stacking method, the sensitivity of Lvt in urine was increased by 105-
to 130-fold. The limits of detection (LOD) and quantification (LOQ) for Lvt in urine were decreased to 8.8 ng/mL and 29.2 ng/mL,
respectively. The intra-day and inter-day precision values (expressed as RSD) were 2.23–3.61% and 4.03–5.05%, respectively.
The recoveries of the analyte at three concentration levels changed from 82.65 to 100.49%. 相似文献
17.
A capillary electrophoresis laser-induced fluorescence detection method (CE-LIF) was developed for the separation of eight
neurotransmitters tagged on their amino function with 6-oxy-(N-succinimidyl acetate)-9-(2′-methoxycarbonyl) fluorescein (SAMF), a new fluorescent reagent synthesized in our lab. Derivatization
was performed in boric acid buffer (pH = 7.75) at 37 °C over 15 min. The pH-independent fluorescence of SAMF (pH 4–9) permits
background buffers over a wide range of pH. It was demonstrated that an acidic running buffer offers a better resolution compared
to basic medium in terms of resolution and peak shapes. Employing Cu2+ as the additive, the molecules were baseline-separated using a running buffer consisting of 40 mM sodium acetate and 2 mM
Cu2+ (pH 6.0). The detection limits ranged from 1 to 2 × 10−10 M. The method has been validated for the characterization of lymphocyte samples. The results obtained illustrate the advantages
of combining SAMF derivatization with CE-LIF for determining neurotransmitters. 相似文献
18.
A rapid method for the simultaneous determination of several non-steroidal anti-inflammatory drugs (NSAIDs) in human plasma
and urine was developed using transient pseudo-isotachophoresis (ITP) in capillary zone electrophoresis (CZE). The influence
of different parameters on resolution and preconcentration efficiency, such as background electrolyte (BGE) composition, sample
injection, sample matrix composition, and pH, were studied to optimize the transient pseudo-ITP performance. Optimized conditions
were a BGE consisting of 100 mM Na2B4O7 in 10% aqueous MeOH solution and hydrodynamic injection of the sample at 50 mbar for 90 s. The sample was prepared in a solution
mixture of 1% NaCl/ethanol (30:70 v/v) at pH 10. Our results show that this simple strategy offers improved sensitivity compared
to conventional CZE analysis, reaching a 45-fold preconcentration factor. The detection limits (LODs) were as low as 0.07 mg/L
for standard samples with good repeatability (values of relative standard deviation, %RSD < 11%). The method was applied to
the analysis of NSAIDs in biological samples. Validation for human plasma and urine samples demonstrated good linearity, low
detection limits, and satisfactory repeatability values. 相似文献
19.
A fast and sensitive liquid chromatography–mass spectrometry method was developed for the determination of ursolic acid (UA)
in rat plasma and tissues. Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was performed
on a 3.5 μm Zorbax SB-C18 column (30 mm × 2.1 mm) with a mobile phase consisting of methanol and aqueous 10 mM ammonium acetate
using gradient elution. Quantification was performed by selected ion monitoring with (m/z)− 455 for UA and (m/z)− 469 for the IS. The method was validated in the concentration range of 2.5 − 1470 ng mL−1 for plasma samples and 20 − 11760 ng g−1 for tissue homogenates. The intra- and inter-day assay of precision in plasma and tissues ranged from 1.6% to 7.1% and 3.7%
to 9.0%, respectively, and the intra- and inter-day assay accuracy was 84.2 − 106.9% and 82.1 − 108.1%, respectively. Recoveries
in plasma and tissues ranged from 83.2% to 106.2%. The limits of detections were 0.5 ng mL−1 or 4.0 ng g−1. The recoveries for all samples were >90%, except for liver, which indicated that ursolic acid may metabolize in liver. The
main pharmacokinetic parameters obtained were T
max = 0.42 ± 0.11 h, C
max = 1.10 ± 0.31 μg mL−1, AUC = 1.45 ± 0.21 μg h mL−1 and K
a = 5.64 ± 1.89 h−1. The concentrations of UA in rat lung, spleen, liver, heart, and cerebellum were studied for the first time. This method
is validated and could be applicable to the investigation of the pharmacokinetics and tissue distribution of UA in rats. 相似文献
20.
Mohamed S. Ibrahim Mohamed S. El-Maazawi Khaled M. Al-Magboul Moustafa M. Kamal 《Mikrochimica acta》2001,137(3-4):215-220
A sensitive method for the determination of amitraz pesticide at nanomolar level by adsorptive stripping voltammetry at a
hanging mercury drop electrode is described. The cyclic voltammograms demonstrate the adsorption of this compound on the mercury
electrode. A systematic study of the various experimental parameters, that affect the stripping response, was carried out
by differential pulse voltammetry. Using an accumulation potential of −0.50 V, and 30 s accumulation time, the limit of detection
was found to be 2.3 × 10−9 mol L−1 and the relative standard deviations (n = 5) was 2.2% at concentration level of 5.0 × 10−8 mol L−1 of amitraz. The influence of diverse ions and some other pesticides was investigated. Finally, the method was applied to
the determination of amitraz in spiked soil and water. The relative standard deviation is 4.5% for 5 determinations of amitraz
in water and 3.2% for 5 determinations in soil.
Received December 6, 2000. Revision March 1, 2001. 相似文献