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1.
A novel flow-injection irreversible biamperometric method is described for the determination of ethamsylate. The proposed method is based on the oxidation of ethamsylate at one platinum electrode and the reduction of permanganate at another to form an irreversible biamperometric detection system. Ethamsylate can be determined over the range 1.0×10−6-1.0×10−4 mol l−1 with a sample measurement frequency of 180 samples h−1. The detection limit for ethamsylate is 4.0×10−7 mol l−1. The stability of the proposed method is shown by a RSD of 0.52% for 11 replicate determinations of 2.0×10−5 mol l−1 ethamsylate. The proposed method was applied to the determination of ethamsylate in pharmaceutical preparations. 相似文献
2.
A biamperometric method for the direct determination of pyrogallol compounds has been designed for flow-injection analysis. The method is based on the electrocatalytic oxidation of pyrogallol compounds at one pretreated platinum electrode and the reduction of platinum oxide at the other pretreated platinum electrode to form a biamperometric detection system with the applied potential difference of 10 mV. Three important compounds, pyrogallol, gallic acid and tannic acid, have been detected by the method. The linear relationships between currents and the concentrations of pyrogallol, gallic acid and tannic acid are obtained over the range 1.0×10−6-1.0×10−4, 1.0×10−6-1.0×10−4 and 1.0×10−6-2.0×10−4 mol l−1 with the detection limit of 6.0×10−7, 6.0×10−7 and 8.0×10−7 mol l−1 (S/N=2), respectively. The R.S.D. observed for 30 successive determinations of 5.0×10−5 mol l−1 pyrogallol, gallic acid and tannic acid are 1.9, 2.5 and 2.0%, respectively. Most ions and organic compounds tested are found not to cause significant interference in the determinations. The method is simple, selective and efficient (180 h−1), performing well as a routine assay, and has been validated by the determination of pyrogallol compounds in tea and Chinese gall. 相似文献
3.
Chen SL Ding F Liu Y Zhao HC 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(1):130-135
The electrochemiluminescence (ECL) of Tb3+-enoxacin-Na2SO3 system (ENX system) and Tb3+-ofloxacin-Na2SO3 system (OFLX system) in aqueous solution is reported. ECL is generated by the oxidation of Na2SO3, which is enhanced by Tb3+-fluoroquinolone (FQ) complex. The ECL intensity peak versus potential corresponds to oxidation of Na2SO3, and the ECL emission spectra (the peaks are at 490, 545, 585 and 620 nm) match the characteristic emission spectrum of Tb3+, indicating that the emission is from the excited state of Tb3+. The mechanism of ECL is proposed and the difference of ECL intensity between ENX system and OFLX system is explained. Conditions for ECL emission were optimized. The linear range of ECL intensity versus concentrations of pharmaceuticals is 2.0 x 10(-10) -8.0 x 10(-7)mol l(-1) for ENX and 6.0 x 10(-10) -6.0 x 10(-7)mol l(-1) for OFLX, respectively. A theoretical limit of detection is 5.4 x 10(-11)mol l(-1) for ENX and 1.6 x 10(-10)mol l(-1) for OFLX, respectively. The ECL was satisfactorily applied to the determination of the two FQs in dosage form and urine sample. 相似文献
4.
A voltammetric procedure in the flow system for determination of traces of Cr(VI) in the presence of Cr(III) and humic acid is presented. The calibration graph is linear from 5×10−10 to 1×10−7 mol l−1 for an accumulation time of 120 s. The R.S.D. for 1×10−8 mol l−1 Cr(VI) is 5.3% (n=5). The detection limit estimated from 3σ for a low concentration of Cr(VI) and accumulation time of 120 s is 2×10−10 mol l−1. The method can be used for Cr(VI) determination in the presence of up to 50 mg l−1 of humic acid. The validation of the method was carried out by studying the recovery of Cr(VI) from spiked river water and by the comparison of the results of determination of Cr(VI) in a soil sample. The method cannot be used for analysis of samples containing high concentrations of chloride ions such as seawater and estuarine water. 相似文献
5.
The determination of cadmium using a carbon paste electrode modified with organofunctionalized amorphous silica with 2-benzothiazolethiol was investigated. The Cd(II) oxidation peak was observed around −0.80 V (vs. SCE) in phosphate buffer (pH 4.0) in differential pulse anodic stripping voltammetry. The best results were obtained under the following optimized conditions: 1 min accumulation time, 50 mV pulse amplitude, 20 mV s−1 scan rate in phosphate buffer pH 4.0. Using such parameters a linear dynamic range from 5.6×10−7 to 3.5×10−5 mol l−1 Cd(II) was observed with a sensitivity of 2.83 μA mol−1 l, limit of detection 1.0×10−7 mol l−1. Cd(II) spiked in a natural water sample was determined with 99% mean recovery at 10−7 mol l−1 level. Interference were also evaluated. 相似文献
6.
Ofloxacin (OFLX) exhibited strong electrogenerated chemiluminescence (ECL) in NaNO3 solution with a dual-electrode system when constant current was exerted. Based on this observation, a sensitive direct ECL method coupled with high-performance liquid chromatography (HPLC) separation was developed for determination of OFLX in human serum. Factors affected the ECL emission were investigated. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of OFLX in the range of 1.0 × 10−8 to 4.0 × 10−6 g mL−1 and the detection limit was 4 × 10−9 g mL−1 (S/N = 3). The proposed method was sensitive, simple and convenient to operate. 相似文献
7.
A novel flow injection (FI) system for the spectrophotometric determination of diethyl stilbestrol diphosphate (fosfestrol) in pharmaceutical formulations is described. On-line thermal induced digestion of the analyte by peroxodisulfate ion was performed and the orthophosphate ion generated was determined spectrophotometrically (λmax=690 nm) using a molybdenum blue based FI approach. As the achieved conversion of the analyte was quantitative, an orthophosphate calibration graph can be used for its determination as well. The chemical and FI variables affecting the digestion were investigated. A linear calibration graph was obtained in the range 5.0×10−7-1.0×10−4 mol l−1 fosfestrol. The relative standard deviation was very good (sr=0.8% at 5.0×10−5 mol l−1 fosfestrol, n=12) and the 3σ detection limit was 2.5×10−7 mol l−1. The sampling rate was 60 injections h−1. The average accuracies for the determination of the analyte in a pharmaceutical formulation evaluated by comparison of the results with those obtained by the supplier (Asta Medica) and the method recommended by the US Pharmacopoeia were also very good (er of +0.8 and −0.3%, respectively). Average recoveries of known amounts of the analyte ranging between 97.9 and 100.8% were also obtained. 相似文献
8.
Yongjun MaMin Zhou Xiaoyong JinBaozhu Zhang Hui Chen Naiyun Guo 《Analytica chimica acta》2002,464(2):289-293
A highly sensitive flow-injection (FI) method with chemiluminescence (CL) detection is used for the determination of l-ascorbic acid. The method is based on the CL reaction of Rhodamine B with cerium(IV) in sulfuric acid media. l-Ascorbic acid is suggested to be a catalyst utilized in the energy-transferred excitation process. The proposed procedure allows quantitation of l-ascorbic acid in the range 3.8×10−13 to 1.0×10−10 mol l−1 with a correlation coefficient of 0.9998 (n=5) and relative standard deviation (R.S.D.) of 0.92% (n=11) at 1.0×10−11 mol l−1. The detection limit (3×blank) was 1.0×10−13 mol l−1. The method is successfully used to determine l-ascorbic acid in fresh vegetables. The possible mechanism of the chemiluminescence in the system is discussed. 相似文献
9.
A poly(vinyl chloride) membrane based on glyoxal bis(2-hydroxyanil) as membrane carrier was prepared and investigated as a Cr(III)-selective electrode. The electrode has a linear dynamic range of 3.0×10−6-1.0×10−2 mol l−1, with a Nernstian slope of 19.8±0.5 mV per decade and a detection limit of 6.3×10−7 mol l−1. It has a fast response time of <20 s and can be used for at least 3 months without any considerable divergence in potential. The proposed electrode revealed good sensitivities for Cr(III) over a wide variety of metal ions and could be used in a pH range of 2.7-6.5. Above all, the membrane sensor has been used very successfully for the analysis of some food materials and alloys for the determination of Cr(III) ion. 相似文献
10.
The electroanalytical determination of isoprenaline in pharmaceutical preparations of a homemade carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) was studied by cyclic voltammetry. Several parameters were studied for the optimization of the sensor such as electrode composition, electrolytic solution, pH effect, potential scan rate and interferences in potential. The optimum conditions were found in an electrode composition (in mass) of 15% CuHCF, 60% graphite and 25% mineral oil in 0.5 mol l−1 acetate buffer solution at pH 6.0. The analytical curve for isoprenaline was linear in the concentration range from 1.96×10−4 to 1.07×10−3 mol l−1 with a detection limit of 8.0×10−5 mol l−1. The relative standard deviation was 1.2% for 1.96×10−4 mol l−1 isoprenaline solution (n=5). The procedure was successfully applied to the determination of isoprenaline in pharmaceutical preparations; the CuHCF modified carbon paste electrode gave comparable results to those results obtained using a UV spectrophotometric method. 相似文献
11.
Spectrofluorimetric determination of aliphatic amines using a new fluorigenic reagent: 2,6-dimethylquinoline-4-(N-succinimidyl)-formate 总被引:1,自引:0,他引:1
A new amino fluorescence probe, 2,6-dimethylquinoline-4-(N-succinimidyl) formate (DMQF-OSu) has been synthesized. Based on the selective reaction of DMQF-OSu with primary and secondary aliphatic amines to yield strong fluorescence, a new spectrofluorimetric method for the determination of total aliphatic amines has been developed. At λex/λem=324.4/416 nm, the linear calibration range was 6×10−8-6×10−6 mol l−1 with the detection limit (3σ) of 1.94×10−10 mol l−1 for the determination of aliphatic amines in weak basic media. The proposed method has been applied to the determination of aliphatic amines in tap water and lake water with the recoveries of 99-104%. Compared with the reported methods, the method presented here is rapid, simple, sensitive and feasible. 相似文献
12.
In this paper, pressurized CEC was used for the separation and determination of seven fluoroquinolones (FQs). The effect of different experimental conditions, such as the concentration and pH of the buffer, the organic modifier concentration, the surfactant and ion-paring agents added to the electrolyte, and applied voltage were studied. All the seven FQs were baseline separated using mobile phase containing 27% v/v ACN, 5 mmol/L Na2HPO4 buffer (pH 4.0 adjusted using citric acid), 11 mmol/L SDS, and 0.01% TEA v/v at detection wavelength of 287 nm and at an applied voltage of -10 kV. The calibration curves were linear (r>0.9991) over a concentration range of 1.0-50.0 mg/L for norfloxacin (NFLX); 2.5-50.0 mg/L for fleroxacin (FLX), ciprofloxacin (CPFX), and lomefloxacin (LMX); and 5.0-50.0 mg/L for enoxacin (ENX), ofloxacin (OFLX), and gatifloxacin (GFLX). The detection limits (S/N = 3) for ENX, OFLX, FLX, NFLX, CPFX, LMX, and GFLX were 0.5, 0.8, 0.4, 0.2, 0.4, 0.5, and 1.0 mg/L, respectively. The method is simple, rapid, and reproducible. It was successfully applied to the analysis of fish muscle samples spiked with FQs. Mean recoveries ranged from 81.6 to 97.6%. 相似文献
13.
A simple and effective chemically modified carbon paste electrode (CMCPE) for the simultaneous determination of lead(II) and cadmium(II) was developed in this work. The electrode was prepared by the addition of diacetyldioxime into a carbon paste mixture. Pb2+ and Cd2+ were preconcentrated on the surface of the modified electrode by complexing with diacetyldioxime and reduced at a negative potential (−1.10 V). Then the reduced products were oxidized by differential pulse stripping. The fact that two stripping peaks appeared on the voltammograms at the potentials of −0.65 V (Cd2+) and −0.91 V (Pb2+) demonstrates the possibility of simultaneous determination of Pb2+ and Cd2+. Under the optimized working conditions, calibration graphs were linear in the concentration ranges of 1.0×10−7-1.5×10−5 mol l−1 (Pb2+) and 2.5×10−7-2.5×10−5 mol l−1 (Cd2+), respectively. For 5 min preconcentration, detection limits of 1×10−8 mol l−1 (Pb2+) and 4×10−8 mol l−1 (Cd2+) were obtained at the signal noise ratio (SNR) of 3. To evaluate the reproducibility of the newly developed electrode, the measurements of 5×10−7 mol l−1 Pb2+ and Cd2+ were parallel carried out for six times at different electrodes and the relative standard deviations were 2.9% (Pb2+) and 3.2% (Cd2+), respectively. Interferences by some metals were investigated. Only Ni2+ and Hg2+ apparently affected the peak currents of Pb2+ and Cd2+. The diacetyldioxime modified carbon paste electrode was applied to the determination of Pb2+ and Cd2+ in water samples. The results indicate that this electrode is sensitive and effective for the simultaneous determination of Pb2+ and Cd2+. 相似文献
14.
Flow-injection chemiluminescence determination of fluoroquinolones by enhancement of weak chemiluminescence from peroxynitrous acid 总被引:1,自引:0,他引:1
A flow-injection chemiluminescence (CL) method is described for the determination of fluoroquinolones including ciprofloxacin, norfloxacin and ofloxacin. The method is based on the enhancement by these compounds of the weak CL from peroxynitrous acid. The linear ranges are 1.0×10−7 to 1.0×10−5 mol l−1 for ciprofloxacin and norfloxacin, and 3.0×10−7 to 3.0×10−5 mol l−1 for ofloxacin, respectively. The detection limits (S/N=3) are 4.5×10−8 mol l−1 ciprofloxacin, 5.9×10−8 mol l−1 norfloxacin and 1.1×10−7 mol l−1 ofloxacin, respectively. The proposed method was applied to the determination of fluoroquinolones in pharmaceutical preparations. 相似文献
15.
In this paper, multi-wall carbon nanotubes fuctionalized with carboxylic groups modified electrode (MWNT-COOH CME) was fabricated. This chemically modified electrode (CME) can be used as the working electrode in the liquid chromatography for the determination of 6-mercaptopurine (6-MP). The results indicate that the CME exhibits efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP are linear to its concentrations ranging from 4.0×10−7 to 1.0×10−4 mol l−1 with the calculated detection limit (S/N=3) of 2.0×10−7 mol l−1. Coupled with microdialysis, the method has been successfully applied to the pharmacokinetic study of 6-MP in rabbit blood. This method provides a fast, sensible and simple technique for the pharmacokinetic study of 6-MP in vivo. 相似文献
16.
A new flow-injection chemiluminescence (CL) method for determination of chloroquine is proposed based on a stronger chemiluminescence of chloroquine in hydrogen peroxide-nitrite-sulfuric acid medium. The proposed method allows the measurement of chloroquine over the range of 3.0×10−7 to 1.0×10−5 mol l−1. The detection limit is 8.6×10−8 mol l−1, and the relative standard deviation for 1.0×10−6 mol l−1 chloroquine (n=11) is 1.6%. The CL mechanism is also discussed. 相似文献
17.
Maria A FotopoulouPenelope C Ioannou 《Analytica chimica acta》2002,462(2):179-185
Terbium sensitized fluorescence was used as a post-column detection system to develop a simple, sensitive and rapid high-performance liquid chromatographic method for the simultaneous determination of catecholamines norepinephrine (NE), epinephrine (E) and dopamine (DA).Catecholamines were separated by an ion-pair reversed-phase chromatography on a BDS-Hypersil analytical column with a mobile phase of methanol and 50 mmol l−1 acetate buffer (pH 4.7) containing 1.1 mmol l−1 SOS and 0.11 mmol l−1 EDTA (15+85 v/v).Catecholamines and the internal standard (3,4-dihydroxybenzylamine, DHBA) were post-column derivatized by the addition to the eluent of an alkaline solution containing a stoichiometric mixture of terbium(III) chloride and EDTA. Fluorescence detection (λex=300 nm, λem=545 nm) is based on the sensitization of terbium ion fluorescence after complexation with catecholamines.The chemical compatibility between the eluent and the post-column reagent was studied and the analytical characteristics of the method were established. Detection limits found were 1.0×10−8, 4.0×10−8 and 7.0×10−8 mol l−1 for NE, E and DA, respectively. The method has been successfully applied to the determination of catecholamines in urine samples after solid-phase extraction (SPE) pre-treatment. Recoveries from urine spiked with NE (4.0×10−7, 2.0×10−6 and 4.0×10−6 mol l−1), E (8.2×10−8, 4.1×10−7 and 8.2×10−7 mol l−1) and DA (1.0×10−6, 5.0×10−6 and 1.0×10−5 mol l−1) varied from 98 to 100% (mean=99.3%), from 106 to 107% (mean=106.3%) and from 98 to 101% (mean=99.3%), respectively. The between-run precision (relative standard deviation, R.S.D.) for the method for three urine samples at different concentration levels of each catecholamine varied from 3.6 to 7.0%. 相似文献
18.
A single-wall carbon nanotubes (SWNT)-Nafion film coated glassy carbon electrode (GCE) was described for the determination of 4-aminophenol. In pH 3.0 sodium citrate-HCl buffer, the oxidation peak current of 4-aminophenol increases greatly at the SWNT-Nafion film coated GCE in contrast to that at both bare GCE and Nafion-film coated GCE. Moreover, the oxidation peak potential shifts to more negative potential. All the experimental parameters were optimized for the determination of 4-aminophenol. The oxidation peak current is proportional to the concentration of 4-aminophenol over the range from 5×10−9 to 2×10−6 mol l−1. The detection limit is 8×10−10 mol l−1 at 4 min of accumulation. Using the proposed method, 4-aminophenol in water samples was determined. 相似文献
19.
A simple, accurate, sensitive and reliable method for the selective extraction and spectrophotometric determination of Bi(III) was developed. Bi(III) was collected on activated carbon after complexation with thiourea and bromide ion in acidic media. The complex retained on activated carbon was then desorbed with the bromide solution in N,N-dimethylformamide (DMF) and determined spectrophotometrically at 375 nm. The linear calibration ranges and limit of detection for the proposed method was 1.00×10−9-1.50×10−7 and 8.00×10−10 mol l−1, respectively. The influence of the interfering cations and anions on the determination of bismuth was investigated. The method was successfully applied to the extraction and determination of bismuth in natural water samples. 相似文献
20.
The suitability of colloidal-gold cysteamine-modified carbon paste electrodes (nAu-Cyst-CPE) for the electrochemical determination of sulphur-containing compounds is illustrated in this work by determining the amino acid methionine in real samples, as well as a methionine-based peptide. Voltammograms from methionine solutions at nAu-Cyst-CPE exhibited improved electroanalytical characteristics when compared with colloidal-gold cysteamine-modified Au disk electrodes (nAu-Cyst-AuE). Differential pulse voltammetry in phosphate buffer of pH 7.0 was used for the determination of methionine, with a range of linearity of (1.0-100) × 10−6 mol l−1 and a detection limit of 5.9 × 10−7 mol l−1. This detection limit is remarkably lower than those reported previously using other modified electrodes or amperometric detection. Methionine peptides also exhibited anodic peaks suitable to detect this kind of molecules. Methionine was determined with good results in a pharmaceutical product containing several vitamins, amino acids and other compounds, and in spiked meat peptone, a complex sample containing enzimatically digested protein. 相似文献