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1.
Composite diazotization-coupling reagents containing sulfanilamide (SAM), sulfapyridine (SP) or sulfathiazole (ST) as the diazotizable aromatic amines and sodium 1-naphthol-4-sulfonate (NS) as the coupling agent using column preconcentration on naphthalene-tetradecyldimethylbenzylammonium(TDBA)-iodide adsorbent have been used for the spectrometric determination of trace nitrate and nitrite in soil and water samples. Nitrite ion reacts with SAM in the pH range 2.0–5.0, SP in the pH range 2.0–2.5 and ST in the pH range 2.0–3.3 in HCl medium to form water-soluble colourless diazonium cations. These cations were coupled with NS in the pH range 9.0–12.0 for the SAM system, 9.6–12.0 for the SP system and 8.5–12.0 for the ST system to be retained on naphthalene-TDBA-I material packed in a column. The solid mass is dissolved from the column with 5 ml of dimethylformamide and the absorbance is measured spectrometerically at 543 nm for SAM-NS, 533 nm for SP-NS and 535 nm for ST-NS. Nitrate is reduced to nitrite by a copper-coated cadmium reductor column and the nitrite is then treated with the diazotization-coupling reagent by column preconcentration. The absorbance due to the sum of nitrate and nitrite is measured and nitrate is determined by difference. The calibration graph was linear over the range 2–40 ng NO2−-N ml−1 and 1.5–30 ng NO3−-N ml−1 in aqueous samples for the SAM and ST systems and 2–48 ng NO2−-N ml−1 and 1.5–36 ng NO3−-N ml−1 in aqueous samples for the SP system, respectively. The sensitivity, accuracy and precision of the systems decreased in the order STSAMSP. The detection limits were 1.4 ng NO2−-N ml−1 and 1.1 ng NO3−-N ml−1 for SAM, 1.6 ng NO2−-N ml−1 and 1.2 ng NO3−-N ml−1 for SP, and 1.0 ng NO2−-N ml−1 and 0.75 ng NO3−-N ml−1 for ST, respectively. The preconcentration factors are 8, 5 and 6 for SAM-NS, SP-NS and ST-NS, respectively. Interferences from various foreign ions have been studied and the methods have been applied to the determination of ng ml−1 levels of nitrite and nitrate in soil and water samples. The mean recovery was 95–102% for all three systems. 相似文献
2.
Spectrophotometric determination of nitrite based on its catalytic effect on the oxidation of carminic acid by bromate 总被引:4,自引:0,他引:4
A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8×10−1 mol l−1 H2SO4, 3.8×10−3 mol l−1 KBrO3, and 1.2×10−4 mol l−1 carminic acid at 30°C. By using the recommended procedure, the calibration graph was linear from 0.2 to 14 ng ml−1 of nitrite; the detection limit was 0.04 ng ml−1; the R.S.D. for six replicate determinations of 6 ng ml−1 was 1.7%. The method is mostly free from interference, especially from large amounts of nitrate and ammonium ions. The proposed method was applied to the determination of nitrite in rain and river water. 相似文献
3.
This is the first report on the determination of proteins with tetra-substituted sulphonated aluminum phthalocyanine (AlS4Pc) by resonance light-scattering (RLS). At pH 3.0, the weak RLS of AlS4Pc can be enhanced by the addition of proteins. Based on this, a novel quantitative method has been developed for the determination of proteins in aqueous solutions. Under optimal conditions, the linear ranges of the calibration curves were 0.050–2.0 μg ml−1 for both human serum albumin (HSA) and human r-IgG. The detection limits were 12.7 ng ml−1 for HSA and 16.1 ng ml−1 for human r-IgG. The method has been applied to the analysis of total protein in human serum samples collected from the hospital and the results were in good agreement with those reported by the hospital, which indicates that the method presented here is not only sensitive, simple, but also reliable and suitable for practical applications. 相似文献
4.
A catalytic flow-injection (FI) method was developed for the determination of 10−9 mol l−1 levels of vanadium(IV, V). The method is based on the catalytic effect of vanadium(V) on oxidation of N-(3-sulfopropyl)-3,3′,5,5′-tetramethylbenzidine (TMBZ·PS) using bromate as oxidant to form a yellow dye (λmax=460 nm). The use of 5-sulfosalicylic acid (SSA) as an activator enhanced the sensitivity of the method. The calibration graphs with a working range 0.05–8.0 ng ml−1 were obtained for vanadium(V). Vanadium(IV) was also determined, being oxidized by bromate. The detection limit (signal/noise, S/N=3) was 0.01 ng ml−1 (ca. 2×10−10 mol l−1) vanadium. The relative standard deviations (R.S.D.) for 15 determinations of 0.5 ng ml−1 vanadium, and for ten determinations of 0.1 and 1.0 ng ml−1 vanadium were 0.41, 2.6 and 0.25%, respectively, with a sampling rate of 15 samples h−1. The proposed method was successfully applied to the determination of vanadium in natural waters. 相似文献
5.
Simple flow-injection system for the simultaneous determination of nitrite and nitrate in water samples 总被引:5,自引:0,他引:5
A novel spectrophotometric reaction system was developed for the determination of nitrite as well as nitrate in water samples, and was applied to a flow-injection analysis (FIA). The spectrophotometric flow-injection system coupled with a copperised cadmium reductor column was proposed. The detection was based on the nitrosation reaction between nitrite ion and phloroglucinol (1,3,5-trihydroxybenzene), a commercially available phenolic compound. Sample injected into a carrier stream was split into two streams at the Y-shaped connector. One of the streams merged directly and reacted with the reagent stream: nitrite ion in the samples was detected. The other stream was passed through the copperised cadmium reductor column, where the reduction of nitrate to nitrite occurred, and the sample zone was then mixed with the reagent stream and passed through the detector: the sum of nitrate and nitrite was detected. The optimised conditions allow a linear calibration range of 0.03–0.30 μg NO2−-N ml−1 and 0.10–1.00 μg NO3−-N ml−1. The detection limits for nitrite and nitrate, defined as three times the standard deviation of measured blanks are 2.9 ng NO2−-N ml−1 and 2.3 ng NO3−-N ml−1, respectively. Up to 20 samples can be analyzed per hour with a relative standard deviation of less than 1.5%. The proposed method could be applied successfully to the simultaneous determination of nitrite and nitrate in water samples. 相似文献
6.
By designing a novel flow-through electrolytic cell (FEC), bromine was produced near to the surface of the platinum electrode by electrochemical oxidation of acidic KBr. The fast and weak chemiluminescence signal produced by the chemical reaction of the electrogenerated bromine with H2O2 was greatly enhanced by tetracyclines Based on these observations, a new, sensitive and simple electrogenerated chemiluminescence (ECL) method for the determination of tetracyclines was developed. Under the optimum experimental conditions, the calibration graphs are linear over the range 3.0×10−8 to 5.0×10−5 g ml−1 for tetracycline, 2.0×10−7 to 2.4×10−5 g ml−1 for oxytetracycline and 1.0×10−7 to 5.0×10−5 g ml−1 for chlortetracycline. The limits of detection (S/N=3) are 1.0×10−8 g ml−1 for tetracycline, 7.0×10−8 g ml−1 for oxytetracycline and 1.5×10−7 g ml−1 for chlortetracycline. For the determination 5.0×10−7 g ml−1 tetracycline, the relative standard deviation was <5%. The proposed method was used to determine tetracyclines in pharmaceutical formulations. 相似文献
7.
Muñoz de la Peña A Espinosa Mansilla A Murillo Pulgarín JA Alañón Molina A Fernández López P 《Talanta》1999,48(5):1042-1073
The stopped flow mixing technique has been used to study the kinetic determination of dipyridamole by means of micellar-stabilized room temperature phosphorescence (RTP). This mixing system diminishes the time required for the deoxygenation of the micellar medium by sodium sulfite. The phosphorescence enhancers thallium (I) nitrate, sodium dodecyl sulfate (SDS), and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 10.6 was selected as adequate for phosphorescence development. The kinetic curve of dipyridamole phosphorescence was scanned at λex=303 nm and λem=616 nm. Then, the intensity at 10 s, and the maximum slope of phosphorescence development, for an interval time of 1 s, were measured. Two determination approaches: intensity and rate methods, were proposed. The calibration graphs were linear for the concentration range from 50 to 400 ng ml−1. The detection limits, according to Clayton et al., Anal. Chem. 59 (1987) 2506, were 21.5 and 37.5 ng ml−1, for intensity and initial rate measurements, respectively. By applying the error propagation theory, the detection limits were 19.0 and 33.0 ng ml−1, for intensity and initial rate measurements, respectively. Two commercial formulations (persantin and asasantin) were analyzed by both proposed methodologies. Adequate recovery values were obtained in both cases. 相似文献
8.
It was found that the weak chemiluminescence produced from the reaction of polyhydroxy phenols with luminol in alkaline solution could be strongly enhanced by ferricyanide and ferrocyanide. Based on this found, a new flow injection chemiluminescence method is proposed for the determination of four polyhydroxy phenols: pyrogallol, phlorglucinol, quinol and resorcinol. The detection limits of the method are 0.03 μg ml−1 pyrogallol, 0.03 μg ml−1 phlorglucinol, 0.04 μg ml−1 quinol, and 0.02 μg ml−1 resorcinol. The possible mechanism of CL reactions is also discussed briefly. 相似文献
9.
A catalytic photometric method was developed for the determination of sub-nanogram levels of cobalt. The method is based on the catalytic effect of cobalt(II) on the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline (DAOS) to form a colored dye (λmax=525 nm) in the presence of hydrogen peroxide. In this reaction system, 1,2-dihydroxybenzene-3,5-disulfonate (Tiron) acted as an effective activator for the catalysis of cobalt(II). Variation of reaction time between 5 and 10 min allows the determination range to be extended from 0.01 to 1.0 ng ml−1. The reaction system can also be successfully adapted to flow-injection analysis (FIA). The dynamic range of the proposed flow-injection method was 0.01–1.0 ng ml−1 and detection limit (signal/noise, S/N=3) was 5 pg ml−1 at a sampling rate of 30 h−1. Manual and flow-injection methods were applied to the direct determination of cobalt in pepperbush as a standard material. 相似文献
10.
The very sensitive, fairly selective direct spectrophotometric method for the determination of trace amount of vanadium (V) with 1,5-diphenylcarbohydrazide (1,5-diphenylcarbazide) has been developed. 1,5-diphenylcarbohydrazide (DPCH) reacts in slightly acidic (0.0001–0.001 M H2SO4 or pH 4.0–5.5) 50% acetonic media with vanadium (V) to give a red–violet chelate which has an absorption maximum at 531 nm. The average molar absorption coefficient and Sandell’s sensitivity were found to be 4.23×104 l mol−1 cm−1 and 10 ng cm−2 of Vv, respectively. Linear calibration graph were obtained for 0.1–30 μg ml−1 of Vv: the stoichiometric composition of the chelate is 1:3 (V: DPCH). The reaction is instantaneous and absorbance remain stable for 48 h. The interference from over 50 cations, anions and complexing agents has been studied at 1 μg ml−1 of Vv. The method was successfully used in the determination of vanadium in several standard reference materials (alloys and steels), environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, solution containing both vanadium (V) and vanadium (IV) and complex synthetic mixtures. The method has high precision and accuracy (s=±0.01 for 0.5 μg ml−1). 相似文献
11.
A new competitive enzyme-linked immunosorbent assay (ELISA) for determination of estrogenic bisphenols 总被引:8,自引:0,他引:8
Bisphenol A and other hydroxylated diphenylalkanes (generally known as bisphenols) have been identified as potential estrogenic substances. In this paper, a specific polyclonal antibody was produced against these compounds by immunization of rabbits with a conjugate of 4,4-bis (4-hydroxyphenyl) valeric acid and bovine serum albumin (BHPVA-BSA). The polyclonal antibody showed specific recognition of the bisphenol structure, while the cross reactions of other common phenolic compounds such as phenol, hydroquinol and p-hydroxybenzoic acid were all lower than 1%. The linear range of bisphenol A calibration curve was 1–10 000 ng ml−1. Real water samples and mouse serum samples were spiked with known amount of bisphenol A and measured by the competitive ELISA. Recoveries were between 92 and 105%. The detection limits were found to be 0.1 ng ml−1 for real water samples and 2 ng ml−1 for serum samples. The method is very useful for monitoring bisphenol compounds in environmental and biological samples. 相似文献
12.
A rapid and sensitive method for the trace level determination of beryllium based on the formation of a 1:2 complex (λmax 560 nm) with 1,4-dihydroxy-9,10-anthracenedione in an aqueous medium containing Triton X-100 is reported. Beer’s law is followed in the range 3.60–360 ng ml−1 of Be(II). The molar absorptivity and Sandell’s sensitivity are 1.68×104 l mol−1cm−1 and 0.54 ng cm−2, respectively; detection limit is 0.23 ng ml−1 of Be(II). Analysis of synthetic mixtures of composition similar to that of alloys and spiked samples of distilled water, gave results that are in agreement with their beryllium content. 相似文献
13.
A simple and highly selective isocratic reverse-phase high performance liquid chromatography (RP-LC) method at room temperature is developed in order to determination of Cyclosporine A (CyA) and its major metabolite (AM1) in serum samples of kidney transplanted patients. The method uses a phenyl column stationary phase, acetonitrile–water–methanol 47:50:3 as mobile phase and 215 nm detector wavelength, at room temperature. The solid phase extraction procedure using cyano disposable extraction column was carried out to separtate the CyA and AM1 with recovery 99±6 and 98±10, respectively. A linear correlation was found at the range of 40–1000 ng ml−1 for CyA and 25–500 ng ml−1 for AM1. The average intra and inter-day variations were 5.03 and 7.89% for CyA, 5.92 and 8.12% for AM1, respectively. The detection limit of 20 ng ml−1 was found for CyA and 12.5 ng ml−1 for AM1. Also, the clinical application of the method using serum concentration against time profile from kidney transplantated patients is reported. 相似文献
14.
A new sensitive colour reaction for nitrite determination is presented. In acidic medium, nitrite was reacted with safranine to form a diazonium salt which caused the reddish-orange dye colour of the solution to change to blue. The carrier stream, into which the sample solution was injected, was doubly distilled water. The reagent solution stream, which contained safranine dye, hydrochloric acid and potassium chloride, was mixed with the carrier in a 3-m length of silicon tubing (bore 0.5 mm) maintained at 30°C in a thermostatic bath. The absorbance intensity was measured at 520 nm. The detection limit was 20 ng ml−1 and the RSD% of 20 injections of 1 μg ml−1 of nitrite was 0.65%. Analysis can be done at a rate of up to 30 h−1. Under the optimum conditions in the concentration range of 30–4000 ng ml−1 of nitrite ion, a linear calibration graph was obtained (r=0.9999). The method was applied successfully to the determination of nitrite in sausages. 相似文献
15.
A spectrofluorimetric method to determine levofloxacin is proposed and applied to determine the substance in tablets and spiked human urine and serum. The fluorimetric method allow the determination of 20–3000 ng ml−1 of levofloxacin in aqueous solution containing acetic acid–sodium acetate buffer (pH 4) with λexc=292 and λem=494 nm, respectively. Micelle enhanced fluorescence improves the sensibility and allows levofloxacin direct measurement in spiked Human serum (5 μg ml−1) and urine (420 μg ml−1), in 8 mM sodium dodecyl sulphate solutions at pH 5. 相似文献
16.
Two different spectrofluorimetric methods for the determination of piroxicam (PX) in serum are presented and discussed. One of them is based on the use of three-way fluorescence data and multivariate calibration performed with parallel factor analysis (PARAFAC) and self-weighted alternating trilinear decomposition (SWATLD). This methodology exploits the so-called second-order advantage of the three-way data, allowing to obtain the concentration of the studied analyte in the presence of any number of uncalibrated (serum) components. The method was developed following two different procedures: internal standard addition and external calibration with standard solutions, which were compared and discussed. The second approach investigated is based on the combination of solid-phase extraction (SPE) and room temperature fluorimetry. Both methods here presented yield satisfactory results. The concentration range in which PX could be determined in serum was 1–10 μg ml−1. The limits of quantification for the experimental solutions using the chemometric approach were 0.09 μg ml−1 for the standard addition mode and 0.12 μg ml−1 using external calibration (both for PARAFAC and SWATLD algorithms). In the solid-surface fluorimetric method, the calibration graph was linear up to 0.22 μg ml−1 and the limit of quantification was 0.02 μg ml−1. 相似文献
17.
Trace amounts of germanium can be determined by atomic spectrometry by utilizing the vaporization of germanium tetrachloride at ambient temperature. Using an intermittent or continuous flow reactor, the sample solution was mixed with concentrated hydrochloric acid to form volatile germanium tetrachloride which can subsequently be determined by atomic spectrometry. The conditions for the volatilization of germanium chloride were investigated in detail and rapid method for the determination of trace amounts of germanium in real samples was proposed. A detection limit of 0.5 ng ml−1 (3σn−1) was obtained by using atomic fluorescence spectrometric detection and the precision found was 0.8% for a germanium concentration of l00 ng ml−1. Atomic emission and absorption spectrometric methods were also tested. Owing to the high selectivity of the reaction, no interference was found in the determination. The method was applied to the determination of germanium in several standard and certified reference materials; the results obtained were in good agreement with the certified values. 相似文献
18.
L. L pez-Martí nez F. J. Luna V zquez P. L. L pez-de-Alba 《Analytica chimica acta》1997,340(1-3):241-244
A simple and rapid spectrophotometric method for the determination of tinidazole is presented. This method is based on the measurement of the absorbance of the signal at 368 nm yielded by bathochromic shift during alkaline hydrolysis of tinidazole in 0.1 N NaOH. The method is linear within the range of 1–30 μg ml−1, and the detection and quantification limits are 0.07 and 0.25 μg ml−1, respectively. The precision of the method, expressed as the relative standard deviation, is 0.19% for a tinidazole concentration of 15 (μg ml−1. The method was applied to the analysis of tinidazole in pharmaceutical formulations and serum. 相似文献
19.
A sensitive flow-injection spectrophotometric procedure is proposed for the determination of manganese(II), based on its catalytic effect on the oxidation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with periodate. By monitoring the change in absorbance of the oxidation product of ABTS at 415 nm, manganese(II) in the range 0.05–1.0 ng ml−1 can be determined with a sampling frequency of 30 h−1. A relative standard deviation (R.S.D.) (n=10) is 1.6% at the 0.5 ng ml−1 level. The proposed method suffers from few interferences and has been successfully applied to the determination of manganese in river, lake and seashore water samples. 相似文献
20.
M. Gracia Bagur D. Gzquez Evangelista M. Sanchez Vias 《Journal of chromatography. A》1996,730(1-2):241-246
A normal-phase high-performance liquid chromatographic method for the selective simultaneous determination of vanadium and molybdenum with N-benzoyl-N-phenylhydroxylamine (BPHA) is described. The V(V)-BPHA and Mo(Vl)-BPHA complexes were preconcentrated by solvent extraction into chloroform and injected on to a nitrile-bonded column for chromatography. The mobile phase was a 5.9· 10−4 M solution of BPHA in chloroform (stabilized with amylene). The detection limits for vanadium and molybdenum were 2.1 and 3.3 ng ml−1, respectively, for an aqueous to organic phase-volume ratio of 20:1. The procedure, applied to the analysis of a synthetic water, showed satisfactory accuracy and precision. 相似文献