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1.
R. Rahnama Kozani Y. Assadi F. Shemirani M. R. Milani Hosseini M. R. Jamali 《Chromatographia》2007,66(1-2):81-86
Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking
water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL
acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation
by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture
detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume
of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment
factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L−1. The linear range was 0.01–50 μg L−1 (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L−1 THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that
total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L−1. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L−1 were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple
and rapid (less than 2 min) method which requires a small volume of sample (5 mL). 相似文献
2.
Summary An ion-chromatographic procedure is described for the determination of selenium (VI) at μg L−1 level in the presence of anions and heavy metal ions. Maximum permissible concentrations and effects from each interfering
substance were investigated for the Se concentration range 12.5–1,000 μg L−1. The method, optimized for the detection of SeO
4
2−
, gives results suitable for speciation analysis. Total selenium can be determined after complete conversion to selenate ion
by oxidation with KMnO4. The detection limit of selenium is 4.8 μg L−1 (0.96 ng for 200 μL sample).
Paper presented at the 41st Pittsburgh Conference, New York, March 5–9, 1990. 相似文献
3.
A highly sensitive high-performance liquid chromatographic method with fluorescence detection has been developed for determination
of vitamin B1. Vitamin B1 was converted into a fluorescent compound by treatment with hydrogen peroxide–horseradish peroxidase and the derivative was
subsequently analyzed by HPLC on a Waters Spherisorb ODS2 column (250 mm×4.6 mm ID, 5 μm) with 40:60 methanol–pH 8.5 acetate
buffer solution as mobile phase and fluorescence detection at 440 nm (with excitation at 375 nm). The calibration graph was
linear from 5.00×10−10 mol L−1 to 5.00×10−7 mol L−1 for vitamin B1 with a correlation coefficient of 0.9991 (n=9). The detection limit was 1.0×10−10 mol L−1. The method was successfully used for determination of vitamin B1 at pg mL−1 levels in microalgal fermentation media and seawater after solid-phase extraction. Recovery was from 89 to 110% and the relative
standard deviation was in the range 1.1 to 4.3%. 相似文献
4.
Summary Elevated plasma homocysteine is, a known risk factor in arteriosclerotic vascular disease. To measure homocysteine in a large
number of samples, we have developed a rapid, simple, robust and inexpensive reversed-phase HPLC method for routine analysis.
Mercaptopro-pionylglycine was used as the internal standard and an external calibration in plasma was performed. Improvement
was achieved by the use of gradient elution (using a sodium acetate buffer and methanol) resulting in a higher number of samples
analyzed per day. Plasma samples were reduced with tributylphosphine and the proteins were precipitated with perchloric acid
before addition of internal standard. The analytes were derivatized by use of 7-fluorobenzofurazone-4-sulfonic acid ammonium
salt. For calibration human plasma was spiked with nine different concentrations of homocysteine (range 2–50 μmol L−1). The inter-assay precision of replicate (n=29) analysis of the concentration of homocysteine in a sample of pooled plasma was 3.0%. The limit of detection, defined
as three times the signal-to-noise ratio, was 0.25 μmol L−1. The linearity of the assay was confirmed for a plasma concentration range of 2–2000 μmol L−1. The variation of duplicate analyses of 842 plasma samples was 2.6±1.7%. 相似文献
5.
Karadjova IB Lampugnani L D'Ulivo A Onor M Tsalev DL 《Analytical and bioanalytical chemistry》2007,388(4):801-807
A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation
atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct
plumbane generation in the presence of 0.1 mol L−1 HCl and 1% m/v K3[Fe(CN)6] with 1% m/v NaBH4 as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method
provides a limit of detection and a limit of quantification of 0.3 μg L−1 and 1 μg L−1, respectively. The relative standard deviation varies between 2–6% (within-run) and 4–11% (between-run) at 3–30 μg L−1 Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic
absorption spectrometry in analyses of red and white wines within the concentration range of 9.2–25.8 μg L−1 Pb. 相似文献
6.
A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed.
Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An
emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used
was 2 × 10−6 mol L−1 salicylic acid in 0.1 mol L−1 NH4+/NH3 buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L−1 iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection
was 0.3 μg L−1 and the sampling rate was 60 h−1. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully
applied to the determination of low levels of iron in real samples (river, sea, and spring waters). 相似文献
7.
It has been found that gold nanoparticles (nano-Au) enhance the chemiluminescence (CL) of the luminol–hydrogen peroxide system
and that estrogens inhibit these CL signals in alkaline solution. CL spectra, UV–visible spectra, X-ray photoelectron spectra
(XPS), and transmission electron microscopy (TEM) were used to investigate the mechanism of the CL enhancement. On the basis
of the inhibition, a flow-injection CL method has been established for determination of three natural estrogens. Under the
optimized conditions, the linear range for determination of the estrogens was 0.07 to 7.0 μmol L−1 for estrone, 0.04 to 10 μmol L−1 for estradiol, and 0.1 to 10 μmol L−1 for estriol. The detection limits were 3.2 nmol L−1 for estrone, 7.7 nmol L−1 for estradiol, and 49 nmol L−1 for estriol, with RSD of 2.9, 2.6, and 1.8%, respectively. This method has been used for analysis of estrogens in commercial
tablets and in urine samples from pregnant women. 相似文献
8.
Zenovia Moldovan 《Chemical Papers》2009,63(4):385-390
A simple, selective and sensitive kinetic method for the determination of nitrite in water was developed. The method is based
on the catalytic effect of nitrite on the oxidation of methylene blue (MB) with bromate in a sulfuric acid medium. During
the oxidation process, absorbance of the reaction mixture decreases with the increasing time, inversely proportional to the
nitrite concentration. The reaction rate was monitored spectrophotometrically at λ = 666 nm within 30 s of mixing. Linear
calibration graph was obtained in the range of 0.005–0.5 μg mL−1 with a relative standard deviation of 2.09 % for six measurements at 0.5 μg mL−1. The detection limit was found to be 0.0015 μg mL−1. The effect of different factors such as acidity, time, bromate concentration, MB concentration, ionic strength, and order
of reactants additions is reported. Interference of the most common foreign ions was also investigated. The optimum experimental
conditions were: 0.38 mol L−1 H2SO4, 5 × 10.4 mol L−1 KBrO3, 1.25 × 10.5 mol L−1 MB, 0.3 mol L−1 sodium nitrate, and 25°C. The proposed method was conveniently applied for the determination of nitrite in spiked drinking
water samples. 相似文献
9.
Summary Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the
determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC)
has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV
injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase
extraction.
A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L−1. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were <30 ngL−1 from 200-μL injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated
solid-phase extraction with C18 cartridges has been applied to water samples (50 mL) spiked at 0.01, 0.1 and 1 μg L−1. The overall procedure was satisfactory (recoveries >80% and coefficients of variation <12%) and the limits of detection
ranged from 1 to 9 ng L−1.
Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2
μg L−1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2
μL. 相似文献
10.
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
11.
Th. Hankemeier J. Rozenbrand M. Abhadur J. J. Vreuls U. A. Th. Brinkman 《Chromatographia》1998,48(3-4):273-283
Summary A procedure is described for the (non-target) screening of hetero-atom-containing compounds in tap and waste water by correlating
data obtained by gas chromatography (GC) using atomic emission (AED) and mass selective (MS) detection. Solid-phase extraction
(SPE) was coupled on-line to both GC systems to enable the determination of microcontaminants at the 0.02–1 μg L−1 level in 7–50 mL of aqueous sample. The screening was limited to compounds present in at least one heteroatom-selective GC-AED
trace above a predetermined concentration level. These compounds were identified by their partial formulae (AED) and the corresponding
mass spectra, which were obtained from the GC-MS chromatogram via the retention index concept. The potential of the approach
was demonstrated by the identification of target compounds as well as all unknowns present in tap and waste water above the
predetermined threshold of 0.05 μg L−1 (tap water) or 0.5 μg L−1 (waste water). 相似文献
12.
Murillo Pulgarín JA Fernández López P Hoyas Nuño P 《Analytical and bioanalytical chemistry》2006,384(2):423-430
A new analytical method is proposed for determination of hydralazine (HZ) in pharmaceuticals—measurement of the chemiluminescence
(CL) emitted after reaction with phosphoric-acidified KMnO4. The novelty of this method is the recording of the whole CL–time profile. Such a recording is possible by use of a CL-detector
operating in tandem which enables the reactants to be mixed in the measurement cell only and, therefore, the CL is reaction
monitored from beginning. At the precise time the pump is stopped signal recording is triggered and so CL evolution is recorded
completely. The optimum chemical conditions for the determination were 0.8 mol L−1 formaldehyde, 0.3 mmol L−1 KMnO4, 4.0 mol L−1 H3PO4, and a total flow of 0.37 mL s−1. Two calibration graphs were plotted, CL intensity and area under the profile curve against HZ concentration. Exhaustive
statistical analysis provided very interesting results, for example, accordance with Clayton’s theory, detection limit below
0.2 μg mL−1, and linear calibration ranges from 0.2 to 5.0 μg mL−1. This method was successfully applied to the determination of HZ in pharmaceuticals. Because they are usually formulated
in association with diuretics and β-blockers, the method was used for analysis of HZ in pharmaceuticals that contained either HZ only or HZ with other hypotensive
substances. Obtained and nominal content were approximately the same and experimental Student t values indicated there were no significant differences between the values. 相似文献
13.
The azo coupling reaction with 2-aminonaphthalene-4,8-disulfonic acid (I) was used to develop a new cheap and rapid method of triclosan (II) determination in hygiene products. The calibration graph was linear in the range of 2.0−100 × 10−6 mol L−1. The detection limit was 2.0 μmol L−1. 相似文献
14.
There is an increasing need to assess the harmful effects of heavy-metal-ion pollution on the environment. The ability to
detect and measure toxic contaminants on site using simple, cost effective, and field-portable sensors is an important aspect
of environmental protection and facilitating rapid decision making. A screen-printed gold sensor in a three-electrode configuration
has been developed for analysis of lead(II) by square-wave stripping voltammetry (SWSV). The working electrode was fabricated
with gold ink deposited by use of thick-film technology. Conditions affecting the lead stripping response were characterised
and optimized. Experimental data indicated that chloride ions are important in lead deposition and subsequent analysis with
this type of sensor. A linear concentration range of 10–50 μg L−1 and 25–300 μg L−1 with detection limits of 2 μg L−1 and 5.8 μg L−1 were obtained for lead(II) for measurement times of four and two minutes, respectively. The electrodes can be reused up to
20 times after cleaning with 0.5 mol L−1 sulfuric acid. Interference of other metals with the response to lead were also examined to optimize the sensor response
for analysis of environmental samples. The analytical utility of the sensor was demonstrated by applying the system to a variety
of wastewater and soil sample extracts from polluted sites. The results are sufficient evidence of the feasibility of using
these screen-printed gold electrodes for the determination of lead(II) in wastewater and soil extracts. For comparison purposes
a mercury-film electrode and ICP–MS were used for validation. 相似文献
15.
Arizaga Rodríguez S Blanco González E Alvarez Llamas G Montes-Bayón M Sanz-Medel A 《Analytical and bioanalytical chemistry》2005,383(3):390-397
Two methods for separation of transferrin (Tf) sialoforms, capillary electrophoresis (CE) and high performance liquid chromatography
(HPLC) with conventional UV absorbance detection, have been investigated and compared. First, conditions affecting the separation
of the Tf isoforms by capillary zone electrophoresis and HPLC were carefully optimized. The use of 15 mmol L−1 borate buffer (pH 8.4) containing 3 mmol L−1 diaminobutane (DAB) as additive enabled good separation of the Tf isoforms by CE (75 cm×50 μm i.d. fused silica capillary)
at 25 kV. In HPLC, a gradient of ammonium acetate (from 0 to 250 mmol L−1 in 45 min) buffered at pH 6 (Tris-HCl) proved suitable for separation of Tf isoforms on a Mono-Q HR 5/5 anion-exchange column.
On-line specific detection of the iron associated with the different Tf isoforms, after Fe saturation, by inductively coupled
plasma mass spectrometry (ICP–MS) was studied in detail to compare its analytical performance with UV detection. For both
CE and HPLC an octapole reaction system (ORS) ICP–MS instrument was used to minimize polyatomic interferences on the 56Fe major isotope. Limits of detection of the different isoforms were in the range of 0.02–0.04 μmol L−1 Tf for HPLC–ICP (ORS)–MS. This hybrid technique proved more selective and reliable detection of transferrin isoforms with
2, 3, 4, 5, and 6 sialic acid residues (S2, S3, S4, S5, and S6) in real serum samples. Interesting results from iron speciation of Tf in serum from healthy individuals and from pregnant
women are given. 相似文献
16.
The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor’s linear response range for nicotine was between 1–25 μmol L−1, with a detection limit of 0.5 μmol L−1. The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis. 相似文献
17.
Determination of norfloxacin in human urine by capillary electrophoresis with electrochemiluminescence detection 总被引:3,自引:0,他引:3
A fast and sensitive approach that can be used to detect norfloxacin in human urine using capillary electrophoresis with end-column
electrochemiluminescence (ECL) detection of is described. The separation column was a 75-μm i.d. capillary. The running buffer was 15 mmol L−1 sodium phosphate (pH 8.2). The solution in the detection cell was 50 mmol L−1 sodium phosphate (pH 8.0) and 5 mmol L−1
The ECL intensity varied linearly with norfloxacin concentration from 0.05 to 10 μmol L−1. The detection limit (S/N=3) was 0.0048 μmol L−1, and the relative standard deviations of the ECL intensity and the migration time for eleven consecutive injections of 1.0 μmol L−1 norfloxacin (n=11) were 2.6% and 0.8%, respectively. The method was successfully applied to the determination of norfloxacin spiked in human
urine without sample pretreatment. The recoveries were 92.7–97.9%.
相似文献
18.
The simultaneous determination of three isomers of phenylenediamines (o, m, and p-phenylenediamine) and two isomers of dihydroxybenzenes (catechol and resorcinol) in hair dyes was performed by capillary
zone electrophoresis coupled with amperometric detection (CZE–AD). The effects of working electrode potential, pH and concentration
of running buffer, separation voltage, and injection time on CZE–AD were investigated. Under the optimum conditions the five
analytes could be perfectly separated in 0.30 mol L−1 borate–0.40 mol L−1 phosphate buffer (pH 5.8) within 15 min. A 300 μm diameter platinum electrode had good responses at +0.85 V (versus SCE)
for the five analytes. Their linear ranges were from 1.0 × 10−6 to 1.0 × 10−4 mol L−1 and the detection limits were as low as 10−7 mol L−1 (S/N = 3). This working electrode was successfully used to analyze eight kinds of hair dye sample with recoveries in the range
91.0–108.0% and RSDs less than 5.0%. These results demonstrated that capillary zone electrophoresis coupled with electrochemical
detection using a platinum working electrode as detector was convenient, highly sensitive, highly repeatable and could be
used in the rapid determination of practical samples.
Figure Electropherograms obtained from 10 mg mL−1 hair dye sample solutions at a platinum working electrode under optimum CZE–AD conditions: (a) natural black (I), (b) golden: (1) p-phenylenediamine, (2) m-phenylenediamine, (3) o-phenylenediamine, (4) resorcinol, and (5) catechol 相似文献
19.
Guzmán-Vázquez de Prada A Loaiza OA Serra B Morales D Martínez-Ruiz P Reviejo AJ Pingarrón JM 《Analytical and bioanalytical chemistry》2007,388(1):227-234
A molecularly imprinted polymer was developed and used for solid-phase extraction (MISPE) of the antihelmintic fenbendazole
in beef liver samples. Detection of the analyte was accomplished using square wave voltammetry (SWV) at a cylindrical carbon
fibre microelectrode (CFME). A mixture of MeOH/HAc (9:1) was employed both as eluent in the MISPE system and as working medium
for electrochemical detection of fenbendazole. The limit of detection was 1.9 × 10−7 mol L−1 (57 μg L−1), which was appropriate for the determination of fenbendazole at the maximum residue level permitted by the European Commission
(500 μg kg−1 in liver). Given that the SW voltammetric analysis could not be directly performed in the sample extract as a consequence
of interference from some sample components, a sample clean-up with a MIP for selectively retaining fenbendazole was performed.
The MIP was synthesized using a 1:8:22 template/methacrylic acid/ethylene glycol dimethacrylate ratio. A Britton–Robinson
Buffer of pH 9.0 was selected for retaining fenbendazole in the MIP cartridges, and an eluent volume of 5.0 mL at a flow rate
of 2.0 mL min−1 was chosen in the elution step. Cross-reactivity with the MIP was observed for other benzimidazoles. The synthesized MIP
exhibited a good selectivity for benzimidazoles with respect to other veterinary drugs. The applicability of the MISPE-SWV
method was tested with beef liver samples, spiked with fenbendazole at 5,000 and 500 μg kg−1. Results obtained for ten different liver samples yielded mean recoveries of (95 ± 12)% and (96 ± 11)% for the upper and
lower concentration level, respectively. 相似文献
20.
Summary A method has been developed for separation and quantitation of midecamycin A1 and related impurities by high-performance liquid chromatography with evaporative light-scattering detection (ELSD). Chromatographic
conditions included use of a Diamonsil C18 column; the mobile phase was 52:48 acetonitrile −0.2 mol L−1 ammonium formate solution (adjusted to pH 7.3 with triethylamine) at a flow rate of 1 mL min−1. The column temperature was 35°C, the shift tube temperature of the ELSD was 105°C, and the gas flow rate of the ELSD was
3.0 L min−1. The response factors of midecamycins in HPLC-ELSD were the same; the linear equation wasy=599292.44x+2868618.04,r=0.9979, the linear range was 5–80 μg,RSD=0.21–1.54%, and theLOD andLOQ were 0.36 and 1.2 μg, respectively. The method was simple, quick, and precise and could be used to determine midecamycin
and its related impurities directly. 相似文献