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61.
Nahid Haghnazari Abdolhamid Alizadeh Changiz Karami Zohreh Hamidi 《Mikrochimica acta》2013,180(3-4):287-294
We describe a method for the modification of gold nanoparticles (Au-NPs) with benzo-15-crown-5 that led to the development of a colorimetric assay for Ag(I) ion. The brown color of a solution of the modified Au-NPs turns to purple on addition of Ag(I) ion. The ratio of the UV–vis absorption at 600 nm and 525 nm is proportional to the concentration of Ag(I) ions in the range from 20 to 950 nM, and the detection limit is 12.5 nM. Other metal ions do not interfere if present in up to millimolar concentrations. The method enables a rapid determination of Ag(I) in lake and drinking water and is amenable to bare-eye readout. Figure
The selective colorimetric detection of Ag+ ion using gold nanoparticles modified with benzo crown ether is reported with a color detection limit ~50 nM by naked-eye. The feasibility and simplicity of this cost-effective sensing system demonstrates great potential for the detection of sliver ion in real samples. 相似文献
62.
63.
Nahid Mashkouri Najafi Ahmadi Seyed Hamid Rajabi Khorrami Afshin 《Microchemical Journal》2003,75(3):151-158
A simple and fast analytical procedure was developed for the determination of caffeine in black tea leaves. The method is based on multiple linear regression treatment of Fourier transform infrared spectrometric data obtained in the wave number range 1800–1300 cm−1 after extraction of caffeine in CHCl3 from tea samples, wetted with an aqueous solution of NH3 (0.1 M). The procedure requires no complex sample preparation. It provided a limit of detection of 0.035 mg/ml, a sampling frequency of 6 h−1 and a coefficient of variation of 0.8% for five independent measurements of a tea sample with 3.68% w/w caffeine content. This procedure provides a drastic reduction in the consuming organic solvent for each sample compare to that of the reference chromatographic determination. The accuracy of technique is evaluated by comparing the obtained results with those of a reference HPLC technique. An average value of 3.60±0.07% w/w was obtained by HPLC for a powdered tea sample which is compromising when is compared to 3.68±0.03% (w/w) obtained by this FTIR technique. 相似文献
64.
1-azacarbazole hydrogen-bonded dimers undergo photoinduced double proton transfer reaction in their lowest excited singlet state. A second emission band with a maximum at 510 nm arises from a tautomer formed in the excited singlet state as a result of the double proton transfer process. 相似文献
65.
Aniline‐formaldehyde resin modified by adding piperazine (AFP) was prepared in alkaline medium, and its metal polychelates have also been prepared with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) metal ions. The synthesized compounds were characterized by elemental, spectral (UV–Vis, IR, 1H‐NMR and 13C‐NMR), thermogravimetric analysis (TGA), and magnetic moment measurements. The percentage of metal in all of the polychelates was found to be consistent with 1:1 (metal/resin) stoichiometry. The thermal behaviors of these coordination polymers were studied by TGA in a nitrogen atmosphere up to 750°C. The TGA results revealed that all the metal polychelates had higher thermal‐resistance property compared to the common resin (AFP). The magnetic moment measurements and UV–Vis spectra confirmed the geometry of the central metal ion in all the polychelates. All the synthesized metal polychelates showed excellent antibacterial activities against the selected bacteria. The antibacterial activities were determined using the shaking flask method, where 25 mg/ml concentrations of each compound were tested against 105 CFU/ml bacteria solutions. The number of viable bacteria was calculated by using the spread plate method, where 100 µl of the incubated antibacterial agent in bacteria solutions was spread on agar plates, and the number of bacteria was counted after 24 hr of incubation period at 37°C. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
66.
Naseri NG Baldock SJ Economou A Goddard NJ Fielden PR 《Analytical and bioanalytical chemistry》2008,391(4):1283-1292
Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded
electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting
grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl
reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst
was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes
were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating
flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions
selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over
the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic
flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field
applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required. 相似文献
67.
Hossein Akhlaghi Mahdi Ghorbani Nahid Afshar Lahoori Alireza Shams Orkideh Seyedin 《Journal of Analytical Chemistry》2016,71(7):641-647
A simple, sensitive and selective solid phase microextraction with hollow fiber-supported multi-walled carbon nanotube functionalization reinforced sol–gel combined HPLC method was proposed for the determination of naproxen in tap, well and river water samples. In this method, functionalized multi-walled carbon nanotubes (MWCNTs) were prepared and held in pores of hollow fiber with sol–gel technology by immersion of polypropylene hollow fiber segment into the sol of the functionalized MWCNTs/silica composite and ultrasonically treated at room temperature. Effect of main parameters such as volume of donor phase, pH, extraction time, desorption time, type of desorption solvent, sample ionic strength and stirring rate were studied. Under optimum conditions, linearity was observed in the range of 0.03–500 ng/mL, with correlation coefficients of 0.997. The relative standard deviation for three replicate determinations of 50 ng/mL of naproxen was 4.3%. Limit of detection and pre-concentration factor were 0.008 ng/mL and 198, respectively. In order to check the applicability of the proposed method, it was used to determine trace levels of naproxen in different water samples. 相似文献
68.
The dependence of the mobility of DNA molecules through an hexagonal array of micropillars on their length and the applied electric field was investigated and it was found that mobility is a nonmonotonic function of their length. Results also revealed that the size dependence of the DNA mobility depends on the applied electric field and there is a crossover around E approximately 25 V/cm for the mobility of lambda-DNA and T4-DNA. These observations are explained in terms of the diffusion process inside the structure affected by the solvent and are modeled using the Langevin and its corresponding Fokker-Planck equations. The phenomenon is generalized under three regimes in a phase diagram relating the electric field and the DNA lengths. The model and the associated phase diagram described here provide an explanation for the conflicting results reported by previous authors (Han et al. on the one hand, and Duong et al. and Inatomi et al. on the other) about the dependence of mobility on the DNA size in lattices near or below the radius of gyration. 相似文献
69.
The simultaneous determination of manganese(II) and iron(II) mixtures by using spectrophotometric methods is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used to remove the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for partial least squares calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 450-600 nm range for 21 different mixtures of manganese(II) and iron(II). Calibration matrices were containing 0.05-1.2 and 0.1-2.3 microg mL(-1) Mn(II) and Fe(II), respectively. The RMSEP for manganese(II) and iron(II) with OSC and without OSC were 0.0316, 0.0291, and 0.0907, 0.115, respectively. This procedure allows the simultaneous determination of manganese(II) and iron(II) in synthetic and real matrix samples with good reliability of the determination. 相似文献
70.
Ali Reza Ghiasvand Hadis Solaymani Nahid Heidari 《Journal of the Iranian Chemical Society》2017,14(5):1113-1118
Quercetin is a polyphenolic flavonoid found in many plants and is used as a nutritional supplement. It has been reported to have biological properties that may play an important role in the prevention of human diseases, such as cancer, cardiovascular diseases, diabetes, ulcer, cataract and allergies. In this research, solidified floating organic drop microextraction coupled to high-performance liquid chromatography was used to extract and determine quercetin in Rosa canina L., growing in different areas of Lorestan Province in Iran. The effect of important experimental variables such as type and volume of extracting organic solvent, extraction temperature and time, pH and effect of ionic strength on the extraction recovery was investigated and optimized. Under the optimum extraction conditions, a linear response was obtained over the range of 0.5–40 µg mL?1. Relative standard deviation (RSD%) and enrichment factor were found to be 3.4% and 230, respectively. The proposed method was applied successfully for the determination of quercetin in calycles and fruit of R. canina L. samples. The results showed good agreement compared with those obtained by a validated standard method. 相似文献