共查询到20条相似文献,搜索用时 218 毫秒
1.
Pawel Pohl Israel Jimenéz Zapata Edgar Voges Nicolas H. Bings José A. C. Broekaert 《Mikrochimica acta》2008,161(1-2):175-184
A 2.45 GHz low power microwave microstrip plasma (MSP) exiting the wafer and operated with Ar at atmospheric pressure was
used for the optical emission spectrometric determination of Hg with the aid of a miniaturized optical fiber spectrometer
with a CCD detector and the cold vapor (CV) generation technique using NaBH4 and SnCl2 as reductants. The experimental conditions were optimized with respect to the relative intensity of the Hg I 253.6 nm line
and its signal-to-background intensity ratio (SBR). So as to understand the results of the optimization experiments, the excitation
temperatures as measured from Ar I lines (T
exc) and the electron number densities (n
e) for the Ar MSP loaded with Hg vapors were determined and found to be in the range from 5500 to 6300 K and from 1.4 to 2.0
× 1014 cm−3, respectively. Under the optimized conditions, the detection limit for Hg of the CV-MSP-OES using SnCl2 as the reducing agent was found to be much lower (0.11 ng mL−1) than in the case where NaBH4 was used (9 ng mL−1). The linearity range was found to be up to 1 μg mL−1 while the precision was of the order of 0.7–5%. The procedure with SnCl2 as reductant was used for the determination of Hg at a concentration of 0.2 μg mL−1 in synthetic water samples containing 1 to 4% (m/v) of NaCl with an accuracy of 3% as well as in a solution of the domestic
sludge standard reference material (NIST SRM 2781) with a certified concentration for Hg of 3.64 ± 0.25 μg g−1 for which 3.55 ± 0.41 μg g−1 was found.
Correspondence: J. A. C. Broekaert, Institut für Anorganische und Angewandte Chemie, Universit?t Hamburg, 20146 Hamburg, Germany 相似文献
2.
The chemiluminescence (CL) system K2MnO4-luminol is shown to be useful for the determination of lead(II). The method is based on the catalytic effect of Pb(II) on
the CL reaction. The linear range was 3 × 10−3–9 × 10−1 mg L−1 (r = 0.9971) and the relative standard deviation (R.S.D.) for 5 × 10−2 mg L−1 Pb(II) measurement was 0.7% (n = 11). The detection limit was 3 × 10−4 mg L−1 (3σ) Pb(II). Based on this, an in vivo, on-line, real-time analytical system for monitoring the metabolism of free lead(II)
in rabbit blood was developed. A microdialysis probe, implanted in the vein of a rabbit, was perfused with perfusate at a
flow rate of 5 μL min−1. The concentration of free lead(II) in the dialysate was determined on-line with a flow-injection CL system. This system
included microdialysis sampling, on-line separation and chemiluminescence detection. The concentration-time curve of lead(II)
was in accordance with the one-compartmental open model, T1/2 (elimination half-life), Tmax (peak time) and Cmax (peak concentration) were 37.77 min, 85.20 min and 0.137 mg L−1, respectively. 相似文献
3.
Victoria F. Samanidou Emmanouil D. Tsochatzis Ioannis N. Papadoyannis 《Mikrochimica acta》2008,160(4):471-475
An HPLC method was developed and validated for the determination of the cephalosporins cefotaxime and cephalexine in skimmed
bovine milk. The analytical column, Kromasil C18 (250 mm × 4.0 mm, 5 μm) was operated at ambient temperature. Mobile phase consisted of CH3OH-acetate buffer (pH = 4.0) and it was delivered isocratically at a flow rate of 1.0 mL · min−1. Total analysis time was less than 5 min. Caffeine was used as internal standard (5 ng · μL−1). UV detection was performed at 265 nm. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. Limits of detection (LOD) and limits of quantification (LOQ) were 0.1 and 0.3 ng · μL−1, respectively. The method was applied to the analysis of a veterinary drug (CEPOREX) containing cephalexine. The results
were quite accurate with the relative error varying from −8.0 to −3.5%. Solid-phase extraction was applied to remove all matrix
interference from milk samples. High extraction recoveries (average 84–121%) were achieved by using Abselut NEXUS cartridges
with acetonitrile as eluent and a rinsing step with water and n-butanol. A pre-concentration step was necessary in a 1/10
level to reach the EU MRL concentration level (100 μg · kg−1). RSD values were less than 7% for both cephalosporins.
Correspondence: Ioannis N. Papadoyannis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University
of Thessaloniki, GR-54124 Thessaloniki, Greece 相似文献
4.
The efficiency of hydrogen selenide generation by HCl, HBr, H2SO4, HClO4 and HNO3 was studied with varying NaBH4 concentrations by continuous flow hydride generation AAS. HBr showed higher efficiency (≈20%) than the conventionally used
HCl. The optimum concentration of reagents were 5 M HBr, with 0.5% NaBH4 and 6 M HCl with 1% NaBH4. The efficiency followed the order HBr>HCl>HClO4>H2SO4>HNO3. The sensitivity and detection limits were 0.16 μg L−1 and 0.15 μg L−1 with HBr, and, 0.19 μg L−1 and 0.17 μg L−1 with HCl. The calibration graphs were linear in the range of 2–25 μg L−1 for both the acids. Se6+ was reduced to Se4+ in 1 M HCl with the addition of solid KBr (4% final solution) with 60 minutes heating at 70 °C and compared to the commonly
used 6 M HCl with 15 minutes boiling. Pre-reduction with KBr showed signal enhancement by 5 to 10% in the range 2–25 μg L−1 of Se4+. The application of the method to SRM 1640 demonstrated that results were in good agreement with the certified values. Groundwater
samples from a suburban area were analyzed and reported. 相似文献
5.
In the configuration of an electrode-separated piezoelectric sensor (ESPS), the quartz crystal surface is in a direct contact
with the liquid phase. With the pre-adsorption of Ca2+ as the ionic bridge, anionic surfactant can adsorb on the negatively charged quartz surface (pH > 2.0). The adsorption process
of sodium dodecyl benzenesulfonate (SDBS) was monitored in real time with the ESPS method. It was shown that the adsorption
of SDBS on quartz surface by Ca2+ inducement was reversible with respective to the dilution of solution phase. The adsorption behavior can be analyzed using
Langmuir model. The adsorption and desorption rate constants were estimated to be k
a
= (108.4 ± 6.4) mol−1L s−1 and k
d
= (2.57 ± 0.32) × 10−3 s−1, respectively. The observed adsorption densities in the ESPS method were significantly greater than the true ones. The influence
on surface roughness of the quartz disc on adsorption densities should be corrected by adding a calibration coefficient in
the Sauerbrey equation. The saturation adsorption density is 0.223 μg/cm2 for SDBS on quartz surface. Double layer occurs for the adsorption of SDBS on quartz surface.
Received July 25, 2001. Revision September 17, 2001. 相似文献
6.
A novel chemiluminescence (CL) detection scheme for the simultaneous determination of vitamin B1 and vitamin B2 has been developed.
After being separated by capillary electrophoresis (CE), the analytes were determined by direct CL of vitamin B1 and vitamin
B2-potassium hexacyanoferrate(III) (K3[Fe(CN)6]) in alkaline aqueous solution. Parameters affecting CE-CL separation and detection, such as the pH value and the concentration
of electrolyte and K3[Fe(CN)6] were optimized. Vitamin B1 and vitamin B2 are completely resolved with migration times shorter than 5 min. Under the optimal
conditions, a linear range from 0.04 to 50, 0.08 to 90 μg mL−1 and a detection limit of 0.01, 0.03 μg mL−1 (signal-to-noise ratio = 3) for vitamin B1 and vitamin B2 respectively, were achieved. The relative standard deviations (R.S.D.)
for 0.5 μg mL−1 of vitamin B1 and 0.8 μg mL−1 of vitamin B2 (n = 11) were 2.9 and 3.7%, respectively. The applicability of the method was examined for the analysis of pharmaceutical tablets.
Correspondence: Juan Bai, Physical Education and Human Kinesiology Department, University of Science and Technology of Qingdao,
Qingdao 266042, China 相似文献
7.
A simple and sensitive flow injection micelle-mediated method was developed for the determination of trace Pb by electrothermal
atomic absorption spectrometric (ET-AAS). The formation of the analyte-entrapped surfactant micelles by online merging of
the analyte solution with O,O-diethyldithiophosphate solution and Triton X-114 solution sequentially, the adsorption of the resultant analyte-entrapped
surfactant micelles onto a microcolumn packed with silica gel. The adsorbed analyte was then eluted with methanol and determined
by ET-AAS. With consumption of 6.0 mL sample solution, a detection limit of 0.016 μg L−1, and a concentration factor of 21.6 were obtained at a sample throughput of 20 h−1. The relative standard deviation was 5.1% (c = 2.0 ng mL−1, n = 7). The method has been successfully applied to the analysis of trace Pb in water sample with recoveries ranging from 94.0
to 99.0%. The certified reference material was also analyzed for validation, and the determined value obtained was in good
agreement with the certified value. 相似文献
8.
An analytical method using alumina modified with water-soluble polyacrylic acid polymer for the simultaneous separation and
preconcentration of trace Cu and Cd in a column system, and their determination by flame atomic absorption spectrometry was
developed. The conditions for coating Al2O3 with polyacrylic acid were optimized, then the column was packed with 50 mg of this sorbent. Cd and Cu solution was passed
through a glass column at pH 4.5, and elution was carried out with 5 mL of 0.05 M HCl at a flow rate of 1 mL min−1. A sorption capacity of 10 mg Cu and 12 mg Cd was obtained for 1 g sorbent. The detection limit was calculated as 4.5 μg L−1 for Cu and 1.54 μg L−1 for Cd in the final solution. Enrichment factors of 300 for Cd and 400 for Cu were obtained. 相似文献
9.
Ahmed T. Mubarak Ashraf A. Mohamed Khalid F. Fawy Ayed S. Al-Shihry 《Mikrochimica acta》2007,157(1-2):99-105
An extremely sensitive and selective kinetic method was developed for the determination of trace levels of nitrite based on
its catalytic effect on the oxidation of perphenazine (PPZ) with bromate in a phosphoric acid medium. The reaction rate was
monitored spectrophotometrically by tracing the formation of the red-colored oxidized product of PPZ at 525 nm within 30 sec
of mixing. The optimum reaction conditions were 4.0 μmol L−1 PPZ, 0.4 mol L−1 H3PO4 and 30 mmol L−1 bromate at 25 °C. Using the recommended procedure, nitrite could be determined with a linear calibration graph up to 4.50 ng mL−1 and a detection limit of 0.07 ng mL−1. The method was conveniently applied to the determination of nitrite in samples of rain, polluted well and formulated waste
waters. Moreover, the published kinetic spectrophotometric methods for nitrite determination are reviewed. 相似文献
10.
An alternative and simple flow injection spectrophotometric analysis method for the determination of iodide in environmental
samples is reported. The method is based on the catalytic destruction of the colour of the Fe(III)–SCN−–CP+–nBPy quarternary complex. The complex shows maximum absorption at 495 nm. The apparent molar absorptivity of the complex in terms
of iodide is (6.22) × 105 l mol−1 cm−1. The detection limit of the method is 0.1 ng ml−1 of iodide. The method obeys Beer’s law up to 120 μg l−1 with slope, intercept and correlation coefficient of 0.11, − 0.52 and + 0.99, respectively. Various flow injection analysis
parameters for the determination of iodide in the environmental samples were optimized. The sample throughput of the method
is 60 samples h−1. The method was successfully useful for the determination of trace level of iodide in environmental samples i.e. ground,
surface water.
Received November 12, 2001; accepted April 2, 2002; published online July 22, 2002 相似文献
11.
Jia-Ming Liu Liang-Yun Xu Shi-Rong Hu Lan Wei Tian-Long Yang Guo-Hui Zhu Xiao-Mei Huang Zhi-Ming Li Xiao-Hua Chen 《Mikrochimica acta》2008,161(1-2):217-224
In the presence of the heavy atom perturber Pb(Ac)2, fluorescein (HFin) can emit strong and stable room temperature phosphorescence (RTP) on the surface of a nitrocellulose
membrane (NCM) at λex
max/λem
max = 480/648 nm. It can be spiked with the 1.5-generation polyamidoamine dendrimers (abbreviated: D-1.5) to emit stronger RTP.
It was found that a quantitative specific affinity adsorption (AA) reaction between concanavalin agglutinin (abbreviated:
Con A) labeled with D-1.5-HFin and N-acetylglucosamine (G) could be carried out on the surface of NCM. The product of the
reaction (D-1.5-HFin- Con A-G) could emit strong and stable RTP, and the ΔIp was proportional to the content of G. According to the above facts, a new method for determination of G by affinity adsorption
solid substrate-room temperature phosphorimetry (AA-SS-RTP) was established, based on Con A labeled with fluorescein using
D-1.5 dendrimers molecules as sensitizer. The linear range of the sandwich method was 0.040–60 pg G spot−1 (corresponding concentration range: 0.10–150 ng mL−1; sample volume: 0.40 μL spot−1). The regression equation of the working curve was ΔIp = 6.880 + 5.610 mG pg spot−1, r = 0.9987. The working solutions containing 0.10 and 150 ng mL−1 G were determined repeatedly 11 times, respectively. The corresponding RSDs were 2.9 and 3.8%. The detection limit of this
method calculated by 3Sb/k was 0.021 pg spot−1 (5.2 × 10−11 g mL−1). Compared with the direct method (detection limit: 0.078 pg spot−1, linear range: 0.40–40 pg G spot−1), the sensitivity was obviously improved and the linear range was wider. This method has been successfully applied to the
determination of G in human plasma, as well as to the supervision and forecast of human diseases, for it is of good sensitivity,
accuracy and precision.
Correspondence: Jia-Ming Liu, Department of Chemistry and Environmental Science, Zhangzhou Normal College, Zhangzhou 363000,
P.R. China 相似文献
12.
A room-temperature ionic liquid N-butylpyridinium hexafluorophosphate was used as a binder to construct an ionic liquid modified carbon paste electrode, which
was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The ionic liquid carbon paste
electrode (IL-CPE) showed enhanced electrochemical response and strong analytical activity towards the electrochemical oxidation
of dopamine (DA). A pair of well-defined quasireversible redox peaks of DA appeared, with the redox peaks located at 215 mV
(E
pa) and 151 mV (E
pc) (vs. the saturated calomel electrode, SCE) in pH 6.0 phosphate buffer solution. The formal potential (E
0′) was calculated as 183 mV (vs. SCE) and the peak-to-peak separation as 64 mV. The electrochemical behavior of DA on the IL-CPE
was carefully investigated. Under the optimal conditions, the anodic peak currents increased linearly with the concentration
of DA in the range 1.0 × 10−6–8.0 × 10−4 mol/L and the detection limit was calculated as 7.0 × 10−7 mol/L (3σ). The interferences of foreign substances were investigated and the proposed method was successfully applied to the determination
of DA injection samples. The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting
ascorbic acid and uric acid. 相似文献
13.
Ashraf A. Mohamed Saleh A. Ahmed Mohamed F. El-Shahat 《Monatshefte für Chemie / Chemical Monthly》2002,133(1):31-40
Summary. A highly selective, sensitive, and simple catalytic method for the determination of molybdenum in natural and waste waters
was developed. It is based on the catalytic effect of Mo(VI) on the oxidation of 2-aminophenol with H2O2. The reaction is monitored spectrophotometrically by tracing the oxidation product at 430 nm after 10 min of mixing the reagents.
Addition of 800 μg · cm−3
EDTA conferred high selectivity; however, interfering effects of Au(III), Cr(III), Cr(VI), and Fe(III) had to be eliminated by
a reduction and co-precipitation procedure with SnCl2 and Al(OH)3. Mo(VI) shows a linear calibration graph up to 11.0 ng · cm−3; the detection limit, based on the 3S
b-criterion, is 0.10 ng · cm−3. The unique selectivity and sensitivity of the new method allowed its direct application to the determination of Mo(VI) in
natural and waste waters.
Received April 11, 2001. Accepted (revised) June 18, 2001 相似文献
14.
A novel method for DNA detection is proposed that is based on the enhancement of resonance light scattering (RLS) of Ru(bpy)2PIP(V)2+ at pH 2.7. Under optimum conditions, good linear relationships were obtained in the wide concentration range of 16–5120 ng mL−1. The linear equation is I
RLS = 13.15 + 171.4 c (μg mL−1), the correlation coefficient (r) is 0.9999. The detection limit of calf thymus DNA is 5.02 ng mL−1. Plasmid DNA extracted from bacillus subtilis was determined by the method with satisfactory results. 相似文献
15.
Fabio de S. Dias Walter N. L. dos Santos Antônio C. S. Costa Bernhard Welz Maria Goreti R. Vale Sérgio L. C. Ferreira 《Mikrochimica acta》2007,158(3-4):321-326
A direct method is proposed for the determination of lead in naphtha and petroleum condensate by electrothermal atomic absorption
spectrometry (ET AAS) using palladium as a permanent modifier. The procedure includes the dilution of 3 mL of sample (naphtha
or petroleum condensate) to a final volume of 10 mL with xylene, and direct injection of 30 μL of this solution into the graphite
furnace. The optimization of the instrumental conditions was performed using multivariate techniques. Firstly, a 23 full factorial design was performed for preliminary evaluation of the factors: pyrolysis time, pyrolysis temperature and
atomization temperature. This experiment showed that in the studied levels only the factors pyrolysis time and atomization
temperature were significant. Then, a 32 full factorial design was performed for the determination of the critical conditions of these variables. The method allows
the determination of lead using the standard calibration technique with a calibration curve from 2.6 to 30 μg L−1 (correlation coefficient higher than 0.998). A limit of detection (3σ) of 0.8 μg L−1 and a characteristic mass of 35 pg were obtained in the presence of palladium as modifier. The precision expressed as relative
standard deviation (RSD) was 1.5 and 0.8% for lead concentrations of 3.0 and 30 μg L−1 (n = 10). Recovery studies demonstrate that lead can be determined in naphtha and petroleum condensate using calibration with
organic standard solutions. This method was applied for the determination of lead in three petroleum condensate and two naphtha
samples. The concentrations found for the petroleum condensate was between 2.7 and 5.7 μg L−1, while the naphtha samples did not contain any detectable lead. 相似文献
16.
Cyclic voltammetry, impedance and chronocoulometry have been employed for the quantitative study of 1-pentanol (n-PenOH) adsorption at the bismuth single-crystal plane | aqueous Na2SO4 solution interface. The adsorption isotherms, Gibbs energies of adsorption ΔG
A
∘, the limiting surface excess Γmax and other adsorption parameters, dependent on the crystallographic structure of the electrodes, have been determined. The
adsorption of n-PenOH on Bi single-crystal planes is mainly physical and is limited by the rate of diffusion of organic molecules to the
electrode surface. Comparison of the adsorption data for n-PenOH with 1-propanol (n-PrOH), 1-butanol (n-BuOH), cyclohexanol (CH) and 1-hexanol (n-HexOH) shows that the adsorption characteristics depend on the structure of the hydrocarbon group. The adsorption activity
of adsorbates at the bismuth | solution interface increases in the sequence n-PrOH < n-BuOH < CH ≤ n-PenOH < n-HA as the adsorption activity at the air | solution interface increases. For all the compounds studied, the adsorption activity
increases in the sequence of planes (111)<(001)<(011ˉ).
Received: 1 July 1998 / Accepted: 2 October 1998 相似文献
17.
Shoujun Lai Xijun Chang Lei Tian Sui Wang Yuanyuan Bai Yunhui Zhai 《Mikrochimica acta》2006,156(3-4):225-230
A sensitive fluorometric method for the determination of ctDNA (calf thymus DNA) is presented. It has good selectivity and
sensitivity and uses nano-SiO2 particles as an effective dispersant and stabilizer for acridine orange (AO). Compared to resonance light scattering (RLS)
and the conventional method that uses organic dyes as fluorescence probe, the new method is more tolerant towards coexisting
foreign substances and also more stable. With 20 mg nano-SiO2 particles, 10 μmol L−1 AO, at pH 8.01 and an ionic strength of 0.02 mol L−1, the interaction of AO with nano-SiO2 and ctDNA results in fluorescent signal enhancement. The extent of enhancement was in good proportion to the concentration
of ctDNA at excitation/emission wavelengths of 490/523 nm, respectively. The calibration curve was linear over 0.66–55.60 μg mL−1. The determination limit (3σ) was 15 μg mL−1. The method was applied to the determination of ctDNA in synthetic samples with satisfactory results. 相似文献
18.
Two simple and sensitive methods for the determination of indapamide in pure and in dosage forms are developed. These methods
are based on the oxidation of indapamide with iron(III) in acidic medium. The liberated iron(II) reacts with 1,10-phenanthroline
(Method A) and the ferroin complex is colorimetrically measured at λmax 509 nm against reagent blank. Method B is based on the reduction of Fe(III) by the drug. Iron(II) forms a colored complex
(λmax 522 nm) with 2,2′-bipyridyl. Optimization of the experimental conditions is described. Beer’s law is obeyed in the concentration
range 1.0–12 μg ml−1 and 4.0–18 μ g ml−1 for A and B, respectively. The apparent molar absorptivity and Sandell sensitivity for method A is 3 × 104 L mol−1 cm−1 and 0.0188 μ g cm−2, while for method B is 2.3 × 104 L mol−1 cm−1 and 0.0159 μg cm−2. The detection and quantification limits are calculated. The developed methods are applied successfully for the determination
of indapamide in pure and in tablet form without interference from common excepients.
Received November 10, 2000. Revision April 6, 2001. 相似文献
19.
A resonance light scattering technique has been developed in order to determine potassium ion in serum. Potassium ion was
found to bind the tetraphenylboronate anion [(C6H5)4B]− in acetate buffer (pH 8.0) in the presence of sodium dodecyl benzene sulfonate as a stabilizer, forming the B(C6H5)4-K aggregate which produces intense resonance scattering light. Effects of factors such as acidity, ionic strength and interferents
on the RLS of B(C6H5)4-K were investigated. The solution pH close to neutral facilitates the production of RLS, and few biologically relevant species
interfere in the determination of potassium ion. The resonance scattering light intensity at the maximum peak of 567 nm was
linear to the concentration of potassium ion in the range of 0.2–2.0 μg mL−1 with a detection limit of 20.0 ng mL−1. The method was applied to determine trace amounts of potassium ion in serum and showed high sensitivity and accuracy compared
with the clinically used ion-selective electrode method. 相似文献
20.
Gian Paulo G. Freschi Carolina D. Freschi José A. Gomes Neto 《Mikrochimica acta》2008,161(1-2):129-135
Different kinds of modifiers and coatings on the integrated platform of transversely heated graphite atomizer (THGA) have
been tested for the simultaneous determination of two group of elements: the first, the more volatile, formed by arsenic,
bismuth, lead, antimony and selenium; the second, the less volatile, formed by cobalt, chromium, cupper, iron and manganese
in milk by electrothermal atomic absorption spectrometry. Different Rh-modifiers were studied, such as Rh-coated platforms
(Rh), carbide plus rhodium coated platforms (W-Rh, Zr-Rh), carbide-coated platforms (W and Zr) with co-injection of RhCl3, solutions and uncoated platforms with injection of solutions of Pd(NO3)2, Mg(NO3)2, and RhCl3. Milk samples were diluted 1:10 in 1.0% HNO3 and injected into the tube. The mass of modifier deposited and co-injected in the tube and the use of end capped tubes were
also evaluated in order to improve the electrothermal behavior of analytes. Integrated platform pretreated with W plus co-injection
RhCl3 for first group and pretreated with W-Rh for second group were elected. For 20 μL injected samples the analytical curves
in the 5.0–20.0 μg L−1 concentration range have good linear correlation coefficients (r > 0.998). Relative standard deviations (n = 12) are <6% and the calculated characteristic masses are between 5 pg and 62 pg.
Correspondence: Gian Paulo G. Freschi, Faculdade de Ciências Exatas e Tecnologia, Universidade Federal da Grande Dourados,
PO Box 332, 79.804-970, Dourados-MS, Brazil; Instituto de Química, Universidade Estadual Paulista, PO Box 355, 14801-970 Araraquara-SP,
Brazil 相似文献