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1.
Hui-Ling Cheng Shyh-Shin Chiou Yu-Mei Liao Chi-Yu Lu Yen-Ling Chen Shou-Mei Wu 《Analytical and bioanalytical chemistry》2010,398(5):2183-2190
We establish a triple-stacking capillary electrophoresis (CE) separation method to monitor methotrexate (MTX) and its eight
metabolites in cerebrospinal fluid (CSF). Three stacking methods with different mechanisms were combined and incorporated
into CE separation. Complete stacking and sharp peaks were achieved. Firstly, the optimized buffer (60 mM phosphate containing
15% THF and 100 mM SDS) was filled into the capillary, which was followed by the higher conductivity buffer (100 mM phosphate,
2 psi for 45 s). The analytes extracted from CSF were injected at 2 psi for 99.9 s, which provided long sample zones and pH
junction for focusing. Finally, the stacking step was performed by sweeping, and separation was achieved by micellar electrokinetic
chromatography. The results of the linear regression equations indicated high linearity (r ≥ 0.9981) over the range of 0.5–7 μM. In intra- and inter-batch results, all data of RSD and RE were below 11%, indicating
good precision and accuracy of this method. The LODs (S/N = 3) were 0.1 μM for MTX, 7-hydroxymethotrexate (7-OHMTX) and MTX-polyglutamates (MTX-(Glu)
n, n = 2–5), 0.2 μM for MTX-(Glu)6, and 0.3 μM for 2,4-diamino-N
10-methylpteroic acid (DAMPA) and MTX-(Glu)7. Our method was implemented for analysis of MTX and its metabolites in the CSF, and could be used for evaluation of its curative
effects of acute lymphoblastic leukemia patients. The data were also confirmed by matrix-assisted laser desorption ionization
time-of-flight mass spectrometry. The results showed good coincidence. 相似文献
2.
Direct analysis of methamphetamine, amphetamine, and p-hydroxymethamphetamine in urine was achieved by cation-selective exhaustive injection and sweeping micellar EKC. A bare fused-silica capillary (40 cm, 50 microm id) was filled with phosphate buffer (80 mM, pH 3, containing 20% ACN). Then a high-conductivity buffer (100 mM phosphate, pH 3; 6.9 kPa for 2.5 min) was injected. Samples were loaded using electrokinetic injection (10 kV, 600 s) which created long zones of cationic analytes. To enhance sensitivity by sweeping, the stacking step was performed using a phosphate buffer (50 mM, pH 3, containing 20% ACN and 100 mM SDS) at -20 kV before separation by MEKC. This method was capable of detecting the analytes at ppb levels. The calibration plots were linear (r(2) >or= 0.9948) over a range of 100-5000 ng/mL for methamphetamine, and 100-2000 ng/mL for amphetamine and p-hydroxymethamphetamine. The LODs (S/N = 3) were 20 ng/mL for methamphetamine, and 15 ng/mL for amphetamine and p-hydroxymethamphetamine. The method was applied to analysis of 14 urine samples of addicts and is suitable for screening suspected samples for forensic purposes. The results showed good agreement with fluorescence polarization immunoassay and GC-MS. 相似文献
3.
Chong Sun Xiao-Di Yang Liu-Yin Fan Wei Zhang Yu-Quan Xu Cheng-Xi Cao 《Analytical and bioanalytical chemistry》2011,399(10):3441-3450
As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor
stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by
its low pK
a. To stack the PCA with low pK
a efficiently, a novel stacking system of MRB was developed, which was formed by an alkaline buffer and double acidic buffers
(viz., acidic sample and blank buffers). With the novel system, the PCA leaking into the blank buffer from the sample buffer
could be well stacked by the prolonged MRB formed between the alkaline buffer and blank buffer. The relevant mechanism of
stacking was discussed briefly. The stacking system, coupled with sample pretreatment, could achieve a 214-fold increase of
PCA sensitivity under the optimal conditions (15 mM (pH 11.5) Gly-NaOH as the alkaline buffer, 15 mM (pH 3.0) Gly-HCl-acetonitrile
(20%, v/v) as the acidic sample buffer, 15 mM (pH 3.0) Gly-HCl as the blank buffer, 3 min 13 mbar injection of double acidic buffers,
benzoic acid as the internal standard, 75 μm i.d. × 53 cm (44 cm effective length) capillary, 25 kV and 248 nm). The limit
of detection of PCA in soil was decreased to 17 ng/g, the intra-day and inter-day precision values (expressed as relative
standard deviations) were 3.17–4.24% and 4.17–4.87%, respectively, and the recoveries of PCA at three concentration levels
changed from 52.20% to 102.61%. The developed method could be used for the detection of PCA in soil at trace level. 相似文献
4.
Summary A capillary zone electrophoretic method for the analysis of phenolic acids in soil and plant extracts was developed with direct
UV detection using a phosphate electrolyte solution. The electrophoretic separation required the phenolic acids to be charged
at a pH above their pKa in order to achieve their migration towards the anode. Electroosmotic flow (EOF) was reversed in direction by adding tetradecyltrimethylammonium
bromide (TTAB). Factors affecting the separation selectivity, including the buffer pH and EOF modifiers, were investigated
systematically. Eight phenolic acids were separated and detected in 10 min using an electrolyte containing 25 mM phosphate,
0.5 mM TTAB and 15% acetonitrile (v/v) at pH of 7.20. Linear plots for the test phenolic acids were obtained in a concentration range of 0.01–1 mM with detection
limits in the range of 1.0–7.0 μM. The recoveries ranged from 92.8 to 102.3% in soil and plant tissues samples spiked at 100
μM and the relative standard deviation based on the peak area were ranged 2.0 to 4.5%. The proposed method was used for the
determination of phenolic acids in plant tissue and soil extracts with direct injection. 相似文献
5.
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
6.
Dhanaji S. Dalavi Meenatai J. Suryavanshi Sawanta S. Mali Dipali S. Patil Pramod S. Patil 《Journal of Solid State Electrochemistry》2012,16(1):253-263
In this paper, we report on the nickel oxide (NiO) thin films potentiostatically electrodeposited onto indium-doped tin oxide-coated
glass substrates by using two types of organic surfactants: (1) non-ionic: polyethylene glycol (PEG), polyvinylpyrrolidone
(PVP) and (2) anionic: sodium dodecyl sulfate (SDS). An aqueous solution containing nickel sulfate precursor and potassium
hydroxide buffer was used to grow the samples. The effect of organic surfactants on its structural, morphological, wettability,
optical, electrochromic, and in situ colorimetry were studied using X-ray diffraction, scanning electron microscopy, contact
angle, FT-IR spectroscopy, optical transmittance, cyclic voltammetry, and CIE system of colorimetry. X-ray diffraction patterns
show that the films are polycrystalline, consisting of NiO cubic phase. A nanoporous structure with pore diameter of about
150–200 nm was observed for pure NiO. The films deposited with the aid of organic surfactants exhibits various surface morphological
feature. PVP-mediated NiO thin film shows noodle-like morphology with well-defined surface area whereas, an ordered pore structure
composed of channels of uniform diameter of about 60–80 nm was observed for PEG. A compact and smooth surface with nanoporous
structure stem from SDS helps for improved electrochromic performance compared with that of NiO deposits from surfactant-free
solution. Wetting behavior shows, transformation from hydrophilic to superhydrophilic nature of NiO thin films deposited with
organic surfactant, which helps for much more paths for electrolyte access. The surfactant-mediated NiO produce high color/bleach
transmittance difference up to 57% at 630 nm. On oxidation of NiO/SDS, the CIELAB 1931 2° color space coordinates show the
transition from colorless to the deep brown state (L* = 84.41, a* = −0.33, b* = 4.41, and L* = 43.78, a* = 7.15, b* = 13.69), with steady decrease in relative luminance. The highest coloration efficiency of 54 cm2 C−1 with an excellent reversibility of 97% was observed for NiO/SDS thin films. 相似文献
7.
Micellar electrokinetic capillary chromatography (MEKC) was performed at 25 °C and 30 kV (under a pressure of 15 mbar), using
30 mM borate buffer containing 60 mM sodium dodecysulfate (SDS) and 5% (v/v) methanol as background electrolyte (pH 9.0) to
determine doxycycline. UV detection was at 350 nm. The method was shown to be specific, accurate (recovery was 100.3 ± 1.0%),
linear over the tested range (correlation coefficient 0.9995) and precise (RSD <1.9%). The method was used to determine doxycycline
in tablets, capsules and human urine after oral application. 相似文献
8.
A cation-selective exhaustive injection and sweeping micellar EKC (CSEI-Sweep-MEKC) was established to analyze morphine and its four metabolites, including codeine, normorphine (NM), morphine-3-glucuronide (M3G), and morphine-6-glucuronide (M6G). After SPE, the urine samples were analyzed by this CE method. The phosphate buffer (75 mM, pH 2.5) containing 30% methanol was first filled into an uncoated fused-silica capillary (40 cm, 50 microm id), then a high-conductivity buffer (120 mM phosphate, 10.3 kPa for 99.9 s) followed. The pretreated urine sample was loaded by electrokinetic injection (10 kV, 600 s). The stacking and separation were performed by using phosphate buffer (25 mM, pH 2.5) containing 22% methanol and 100 mM SDS at -20 kV, and detected at 200 nm. During method validation, calibration plots were linear (r > or = 0.998) over a range of 30-3000 ng/mL for morphine, NM, and codeine, 100-2000 ng/mL for M6G, and 80-3200 ng/mL for M3G. The LODs (S/N = 5, sampling 600 s at 10 kV) were 10 ng/mL for morphine, NM, and codeine, 35 ng/mL for M6G, and 25 ng/mL for M3G. This stacking CE method could increase 2500-fold sensitivity of codeine, when comparing with CZE. Five addicts' urine specimens were analyzed. Their results were compared with those of LC-MS-MS, and showed good coincidence. This method could be feasible for monitoring morphine and its metabolites in forensic interest and pharmacokinetic investigations. 相似文献
9.
Summary A capillary electrophoresis method for the separation and determination of five synthetic dyes used in pharmaceutical preparations,
cosmetics and as food additives is described. The dyes, fluorescein, dichlorofluorescein, Rose Bengal erythrosine and eosine
are well separated in less than 12 min using an electrolyte of 50 mM phosphate buffer (pH 7.5), 10 mM β-cyclodextrin and 5%
(v/v) methanol. A linear relationship between concentration and peak area for each dye was obtained in the concentration range
0.3–500 μg mL−1, with a correlation coefficient greater than 0.999. Intra- and inter-day precision of about 0.2–2.6% RSD (n=11) and 4.9–9.7%
RSD (n=30), respectively, were obtained. The method has been used for determining the purity of fluorescein and erythrosine
in practical samples. 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.
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
12.
《Electrophoresis》2018,39(16):2099-2106
A method consisting of cation‐selective exhaustive injection and sweeping (CSEI‐sweeping) as online preconcentration followed by a cyclodextrin modified electrokinetic chromatography (CDEKC) enantioseparation has been developed for the simultaneous determination of two brompheniramine enantiomers in rat plasma. In this method, analytes were electrokinetically injected at a voltage of 8 kV for 80 s in a fused‐silica capillary. Prior to the injection, the capillary was rinsed with 50 mM phosphate buffer of pH 3.5, followed by a plug of a higher conductivity buffer (150 mM phosphate pH 3.5, 20 psi, 6 min) and a plug of water (0.5 psi, 5 s). Separation was carried out applying –20 kV in 50 mM phosphate buffer, pH 3.5, containing 10% v/v ACN and 30 mg/mL sulfated‐β‐cyclodextrin (S‐β‐CD). Analytical signals were monitored at 210 nm. The detection sensitivity of brompheniramine enantiomers was enhanced by about 2400‐fold compared to the normal injection mode (hydrodynamic injection for 3 s at 0.5 psi, with a BGE of 50 mM phosphate buffer containing 20 mg/mL S‐β‐CD at pH 3.5), and LLOQ of two enantiomers were both 0.0100 μg/mL. In addition, this method had fairly good repeatability and showed promising capabilities in the application of stereoselective pharmacokinetic investigations for brompheniramine enantiomers in rat. 相似文献
13.
Aysel Berkkan Ali İhsan Seçkin Kadir Pekmez Uğur Tamer 《Journal of Solid State Electrochemistry》2010,14(6):975-980
Polymerization of pyrrole and 2-aminobenzoic acid has been investigated, and a functionalized stable film of poly(pyrrole-2-aminobenzoic
acid) (PP2ABA) has been obtained electrochemically onto platinum electrode. Different cyclic voltammetric behavior is obtained
for polypyrrole and PP2ABA during electrosynthesis. Fourier-transformed infrared spectrometry and surface-enhanced Raman spectrometry
measurements on the two films have confirmed the presence of carboxylate group in the films. The enzyme, glucose oxidase,
was covalently immobilized on a conducting PP2ABA film, and amperometric response was measured as a function of concentration
of glucose at a potential of 0.7 V vs Ag/AgCl in 0.1 M phosphate buffer at pH 6.2. The effect of polymeric film thickness,
pH, and possible interferents were investigated. The linear range of the calibration curve is from 3 to 40 mM with a sensitivity
of 0.058 μA mM−1 cm−2 and a limit of detection of 0.5 mM. The apperent Mishaelis–Menten constant K
M is calculated to be 1 × 10−2 mM, and the response time is 5 s. 相似文献
14.
Maria Addolorata Saracino Chiara Marcheselli Lorenzo Somaini Gilberto Gerra Francesco De Stefano Maria Chiara Pieri Maria Augusta Raggi 《Analytical and bioanalytical chemistry》2010,398(5):2155-2161
An isocratic high-performance liquid-chromatographic method has been developed for the simultaneous determination of disulfiram
and bupropion in human plasma samples. Analyses were carried out on a C8 reversed-phase column using a mobile phase composed of 50% acetonitrile and 50% aqueous phosphate buffer, containing triethylamine.
Diode-array detection was used, operating at a wavelength of 250 nm. For the clean-up of plasma samples, a solid phase extraction
procedure, based on C2 cartridges, was implemented. Extraction yields of the analytes were satisfactory, being always higher than 84%. The calibration
curve was linear over the 5–500 ng mL-1 plasma concentration range for both disulfiram and bupropion. The method showed a high sensitivity (limit of detection of
1.5 ng mL-1) and satisfactory precision, selectivity and accuracy. The application to human plasma samples obtained from some alcohol
and nicotine abusers also gave good results. 相似文献
15.
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
16.
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
17.
H. M. Lee C. K. Jeong S. J. Choi B. M. Yoon D. H. Na K. C. Lee H. S. Lee 《Chromatographia》2000,51(5-6):353-356
Summary An automated microbore, liquid chromatographic method with column-switching was developed for the determination of clomipramine
from human plasma samples. After direct injection of samples (60 μL), plasma proteins and clomipramine were separated in size-exclusion
mode using 20% acetonitrile in 20 mM phosphate buffer (pH 7.0) on Capcell Pak MF Ph-1 precolumn (10×4 mm I.D.). By valve switching,
a fraction containing clomipramine was directed to an intermediate column for subsequent main separation on a microbore C18 column (250×1.5 mm I.D.) using 50% acetonitrile in 20 mM phosphate buffer (pH 2.5) at 0.1 mL min−1. The method was advantageous for rapidity (total analysis time: 15 min), reproducibility (C.V.<4.8%), and increased sensitivity
(1 ng mL−1). The linearity of response was good (r
2≥0.999) over the concentration range 1–250 ng mL−1. 相似文献
18.
Ai-Lin Liu Jia-Dong Wang Wei Chen Xing-Hua Xia Yuan-Zhong Chen Xin-Hua Lin 《Journal of Solid State Electrochemistry》2012,16(4):1343-1351
A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite
(p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste
electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak
separation of 155 mV at a scan rate of 100 mV s−1. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine
them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10−7–5.0 × 10−5 M for procaine and 5.0 × 10−7–2.0 × 10−5 M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10−8 M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its
concentration ranging from 1.0 × 10−6 to 5.0 × 10−5 M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10−7 M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after
an intravenous administration of procaine hydrochloride injection. 相似文献
19.
A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled
carbon nanotubes (MWNTs)–chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized
Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E
θ′) of −22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k
s) in the Chit–MWNTs film was evaluated as 2.58 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive Hb in the Chit–MWNTs film was estimated to be (2.48 ± 0.25) × 10−9 mol cm−2. Meanwhile, the Chit–MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis–Menten constant (K
Mapp) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 × 10−6 to 9.30 × 10−5 mol L−1 with a detection limit of 3.47 × 10−7 mol L−1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility. 相似文献
20.
A. Mancha de Llanos M. M. De Zan M. J. Culzoni A. Espinosa-Mansilla F. Cañada-Cañada A. Muñoz de la Peña H. C. Goicoechea 《Analytical and bioanalytical chemistry》2011,399(6):2123-2135
A liquid chromatographic method has been developed, in combination with the multivariate curve resolution-alternating least
squares algorithm (MCR-ALS), for the simultaneous determination of marker pteridines in urine samples. A central composite
design has been applied to optimize the factors influencing the separation (buffer concentration, buffer pH, flow rate, oven
temperature, mobile-phase composition). A set of 15 calibration samples were randomly prepared, in a concentration range of
0.5–10.5 ng mL−1 for neopterin, biopterin, and pterin; 4.0–8.0 ng mL−1 for xanthopterin; and 0.5–4.5 ng mL−1 for isoxanthopterin. The validation was carried out with fortified urine samples from healthy adults. The optimized conditions
were a mobile-phase composition of 10 mM citric buffer at pH 5.44 and acetonitrile (94.5/5.5, v/v), a flow rate of 1.0 mL min−1, and an oven temperature of 25 °C. The detection system consisted of a fast-scanning spectrofluorimeter, which allows obtaining
of second-order data matrices containing the fluorescence intensity as a function of retention time and emission wavelength.
In this work, MCR-ALS was used to cope with coeluting interferences, on account of the second-order advantage inherent to
this algorithm which, in addition, is able to handle data sets deviating from trilinearity, like the high-performance liquid
chromatography data analyzed in the present report. The developed approach enabled us to determine five pteridines, some of
them with overlapped profiles, reducing the experimental time and reagent consumption. Ratio values for pteridines/creatinine
in urine, for infected children with different pathologies, are reported in this work. 相似文献