Dual-signal fenamithion probe by combining fluorescence with colorimetry based on Rhodamine B modified silver nanoparticles

A versatile yet simple strategy for the fabrication of a highly selective and sensitive fenamithion probe based on Rhodamine B (RB) modified silver nanoparticles (RB-Ag NPs) was developed. The advantage of our system over classical assays is that it combined fluorescence with colorimetry which can realize the prompt on-site and real-time detection of fenamithion with high sensitivity (0.1 nM) in aqueous solution. Moreover, the detection system presents excellent anti-disturbance ability when exposed to a series of interfering ionic/pesticides mixtures and can be applied to the determination of fenamithion in real vegetables and different water samples with the limit of detection (LOD) as low as 10 nM (0.0026 mg L(-1)), which is in accord with the maximum contamination level of 0.001～0.25 mg L(-1) for organophosphorus pesticides as defined by the U.S. Environmental Protection Agency (EPA). Advantage is taken of the fact that RB would be displaced from the surface of the Ag NPs because of the stronger coordination ability of Ag NPs with fenamithion, an amino-containing organophosphorus pesticide, accompanying the clustered Ag NPs (9 nm) dissipating into smaller individual particles (7 nm). Based on this phenomenon, a novel analyte-induced etching mechanism was proposed.     

Reversed-phase partition high-pressure liquid chromatography of trace amounts of inorganic and organic mercury with silver diethyldithiocarbamate

Inorganic and organic mercury diethyldithiocarbamates have been separated by reversedphase partition high-pressure liquid chromatography. The mercury chelates were formed by an exchange reaction with silver diethyldithiocarbamate in chloroform, in the presence of acetate buffer (pH 5.0). The inorganic and organic mercury chelates in the extract were separated within 30 min on a 3.9 x 300 mm mu-Bondapak C(18) column. EDTA (10(-4)M) in methanol-water mixture (78:22 v v ) was used as eluent at a flow-rate of 0.5 ml min .     

Electrochemical study and voltammetric determination of sodium diethyldithiocarbamate using silver nanoparticles solid amalgam electrode

We report in this work, for the first time, the voltammetric study and the development of an electroanalytical method for the determination of sodium diethyldithiocarbamate (Na-DDC) using solid amalgam electrode fabricated with silver nanoparticles. The experimental parameters were studied and the best voltammetric response was reached when using 0.02 mol L^–1 Britton–Robinson buffer (pH = 5.5). Cyclic voltammograms of the substance presented two voltammetric signals: one cathodic peak at E_p = – 0.55 V and one anodic peak at E_p = – 0.49 V. The redox process of Na-DDC showed itself as an adsorption-controlled and quasi-reversible system. A mechanism for this electrochemical reaction was proposed. The analytical studies employed square-wave adsorptive stripping voltammetry (SWAdSV) and were based on the cathodic signal given by Na-DDC. Good linearity was observed in the concentration range from 2.83 × 10^–7 mol L^–1 to 6.89 × 10^–6 mol L^–1. The obtained limit of detection was 7.26 × 10^–8 mol L^–1. The electroanalytical approach described here was successfully employed for the determination of Na-DDC in river water at levels of concentration from 1.46 × 10^–7 mol L^–1 to 1.46 × 10^–6 mol L^–1 with good repeatability and reproducibility (RSD values of 4.2% and 5.9%, respectively). The values found during these determinations presented good concordance when compared with the expected values. According to the data presented here, the solid amalgam electrode fabricated with silver nanoparticles may be seen as an effective and green tool for the electrochemical analysis of Na-DDC and also other reducible compounds that usually require mercury-based electrode surfaces.     

Digital image colorimetry method for determination of glucose using silver nanoparticles immobilized into polymethacrylate matrix

We suggest Ag⁰ nanoparticles immobilized into transparent polymethacrylate matrix (PMM–Ag⁰) as a simple colorimetric sensor for determination of glucose. We demonstrate the capabilities of a smartphone to process the images and further analyze the information obtained by determination of glucose using PMM–Ag⁰ sensor. The method can be employed for glucose concentrations of 0.1–4.3 mmol dm⁻³, while its detection limit is 0.05 mmol dm⁻³.     

Evaluation of electrochemical hydride generation for spectrophotometric determination of As(III) by silver diethyldithiocarbamate

A batch electrochemical hydride generation system was developed for the spectrophotometric determination of inorganic As(III) by silver diethyldithiocarbamate. This method is based on electrochemical reduction of As to Arsine (AsH₃) in acidic media and on the subsequent reaction of AsH₃ with silver diethyldithiocarbamate to give an absorbing complex at 525 nm. The electrochemical generator consisted of a cathode cell separated from the anode cell by a porous glass frit and was operated with a constant direct current. A pre-activated graphite rod was used as cathode material for the production of AsH₃. The parameters related to the electrochemical hydride generation were investigated. Under optimized conditions, only As(III) can be converted to AsH₃ and a pre-reducing stage is required for total inorganic As analysis. The characteristic data of the electrochemical hydride generation and common hydride generation by NaBH₄ were compared. Also, the effects of interferences and their elimination were investigated. An absolute detection limit of 0.5 μg (3s_b) and a concentration detection limit of 0.05 μg/ml were obtained using a 10 ml sample volume. The relative standard deviation for five replicate analysis of 30 μg As(III) was 1.2%. The accuracy and recovery of the method were demonstrated by analysing spiked artificial sea water and tap water.     

Micro-heterometric determination of cadmium with sodium diethyldithiocarbamate

0.5 mg of Cadmium in 20 ml aqueous solution can be determined heterometrically at 20°C with sodium diethyldithiocarbamate. The solution may contain 99–99.9% of Ca, Ba, Mg, Zn, Mn, Al, Cr(lll), Fe(III), Sb(III) or Pb. Titration time: 10–15 min. Error generally 0–1%.     

Micro-heterometric determination of bismuth with sodium diethyldithiocarbamate

The reaction between bismuth(III) and sodium diethyldithiocarbamate was investigated. The conditions necessary for the heterometric determination of small amounts ot bismuth in other metals were studied. Various complexing agents were used. Methods and conditions are presented for the direct determination of bismuth (~2%) in salts of the following cations: Ca⁺², Ba⁺², Mg⁺², Zn⁺², Mn⁺², Co⁺², Ni⁺², Al⁺², Cr⁺³, Fe⁺³, Cd⁺², Pb⁺², Hg⁺² and Ag⁺. A titration lasted 10–15 minutes, and the error in most cases was close to zero.     

A heterometric micro-determination of lead with sodium diethyldithiocarbamate

The reaction between lead and sodium diethyldithiocarbamate is studied hcterometrically. The influence of the milieu, conditions of acidity and of different complexing agents, was studied. 0.02–0.04 mg lead per ml of solution can be determined either alone or in the presence of large excesses of other metals. A titration is carried out at 20°C in 8–15 minutes with an error of 0.0–1.0%. The analysed solution may contain ~ 99.5% of the following cations: Ca⁺². Sr⁺², Ba⁺², Mg⁺² Zn⁺², Mn⁺², Ni⁺², Co⁺², Al⁺³, Cr⁺³, Fe⁺³, Cd⁺². Cu⁺², Sb⁺³, Hg⁺², Ag⁺.     

The diethyldithiocarbamate of titanium

The diethyldithiocarbamate complex of titanium has not been previously reported, in the literature. Conditions for its formation and extraction have been examined, together with some interferences. An absorption spectrum has been plotted, and the possibility of determining titanium by means of this reaction investigated.     

Coordination behavior of erbium chloride hydrate with diethylammonium diethyldithiocarbamate

The complex of erbium chloride lower hydrate with diethylammonium diethyldithiocarbamate (D-DDC) has been synthesized conveniently in absolute alcohol and dry N₂ atmosphere. The title complex was identified as Et₂NH₂[Er(S₂CNEt₂)₄] by chemical and elemental analyses, the bonding characteristics of which was characterized by IR. The enthalpies of solution of erbium chloride hydrate and D-DDC in absolute alcohol at 298.15 K and the enthalpies change of liquid-phase reaction of formation for Et₂NH₂[Er(S₂CNEt₂)₄] at different temperatures were determined by microcalorimetry. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of liquid phase reaction of formation were obtained. The enthalpy change of the solid-phase title reaction at 298.15 K was calculated by a thermochemical cycle. This revised version was published online in July 2006 with corrections to the Cover Date.     

A light-modulated chemosensor for methanol with ratiometry and colorimetry

A light-modulated chemosensor for methanol has been developed by using a photochromic spirophenanthoxazine as an indicator. In such a sensor, methanol can be detected easily by colorimetric recognition with high selectivity and anti-interference. Moreover, the concentration of indicator can be modulated and manipulated by light, which provides a simple way for the detection of methanol in a wide range of detectable limit that would be useful in different detection cases.     

Spectrophotometric determination of mercury(II) and silver(I) with copper(II) and diethyldithiocarbamate in the presence of triton X-100

Procedures for the determination of mercury and silver by displacement of diethyldithiocarbamate (DDTC) from its copper complex in the presence of 1% Triton X-100, and measurement of the decrease in the Cu(DDTC)(2) absorbance, are described. The use of the surfactant avoids the need for an extraction step. Reproducibility within 1% and detection limits of 0.25 ppm Hg(II) and 0.45 ppm Ag(I) have been obtained, and linear calibration ranges up to 13 ppm Hg(II) and 15 ppm Ag(I). In the presence of 0.1M EDTA very good selectivity is achieved.     

Extraction-spectrofluorimetric determination of cadmium with diethyldithiocarbamate and calcein in non-aqueous media

Cadmium (7–80 ng ml^?1) is extracted with diethyldithiocarbamate into chloroform from aqueous media, at pH 11–12 and the fluorescent complex is developed by addition of a calcein solution in dimethylformamide. The method is applied to the determination of cadmium in waste waters, high-purity metals and zinc ores.     

Microdetermination of vanadium by ion-exchanger colorimetry

A microdetermination method for vanadium by ion-exchanger colorimetry has been developed. Vanadium is sorbed on the anion-exchanger Dowex 1-X8 as vanadium-benzohydroxamic acid complex in 3 M HCl medium. The resin-phase absorbance at 516 and 800 nm is measured directly. The detection limit is 0.28 μg/liter and the distribution ratio is 340. It is possible to enhance the sensitivity by increasing the sample volume.     

Reaction of halogens with copper(II) bis(diethyldithiocarbamate)

Conclusions It was established by EPR spectroscopy that the reaction of halogens with Cu(dtc)₂ has redox character in polar and nonpolar solvents. However, the ligand is oxidized in a polar solvent, and new complexes of copper(II), the coordination sphere of which is formed via different combinations of solvent molecules, halide ions, and dtc^–, are formed as a result of intraspheral transformations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2484–2488, November, 1988.     

Basic aspects and applications of tristimulus colorimetry

A detailed account of the specification of colour using the 1931 Commission International de L'Eclairage tristimulus coordinates and subsequent colour spaces for the measurement of small differences in colour is provided along with a review of the application of quantitative parameters for the evaluation of colour changes of acid-base and complexometric indicators. The development of screened indicators to improve the quality of colour changes at the equivalence point is discussed. Various computer programs proposed to calculate the different parameters by different algorithms are reviewed.