ABSTRACT
In recent decades, metal-containing nanocomposites have attracted considerable attention from researchers. In this work, for the first time, a detailed analysis of the preparation of reactive indicator papers (RIPs) based on silver-containing nanocomposites derived from silver fumarate was carried out. Thermolysis products are silver-containing nanocomposites containing silver nanoparticles uniformly distributed in a stabilizing carbon matrix. The study of the optical properties of silver-containing nanocomposites made it possible to outline the prospects for their application in chemical analysis. RIPs were made by impregnating a cellulose carrier with synthesized silver fumarate-derived nanocomposites, which change their color when interacting with chlorine vapor. This made it possible to propose a method for the determination of chloride ions with preliminary oxidation to molecular chlorine, which is then separated from the solution by gas extraction. The subsequent detection of the active zone of RIPs using colorimetry makes it possible to identify mathematical dependences of color coordinates on the concentration of chloride ions. The red (R) color coordinate in the RGB (red-green-blue) system was chosen as the most sensitive and promising analytical signal. Calibration plots of exponential and linear form and their equations are presented. The limit of detection is 0.036 mg/L, the limits of quantification are 0.15-2.4 mg/L, and the time of a single determination is 25 min. The prospects of the developed technique have been successfully shown in the example of the analysis of the natural waters of the Don River, pharmaceuticals, and food products.
ABSTRACT
At present, conjugated thermolysis of metal-containing monomers is widely used as single-source precursors to obtain new metal- and metal oxide-containing nanocomposites. In this study, a detailed analysis of the main stages of conjugated thermolysis of silver itaconate was carried out. The obtained nanocomposites containing silver nanoparticles are evenly distributed in a stabilizing carbon matrix. The structural characteristics and properties of the resulting nanomaterials were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). We have developed a method of test analysis of chlorides using paper modified with the obtained silver-containing nanocomposites. The analysis technique is based on the in situ conversion of chlorides to molecular chlorine, its dynamic release, and colorimetric detection using NP-modified paper test strips. A simple installation device is described that allows this combination to be realized. The proposed approach seems promising for nanoparticle-based determinations of other analytes that can be converted into volatile derivatives.
ABSTRACT
An improved step-by-step colorimetric method for determination of halides has been developed. The method is based on successive selective oxidation of iodide, bromide and chloride into corresponding free halogens, their extraction by airflow and colorimetric detection with different paper test-strips. This procedure can be performed in a single analyzed solution and possesses high selectivity and good sensitivity due to the extraction step. Three types of paper test-strips were examined: paper modified with tetramethylammonium iodide and starch, paper modified with methyl orange and paper modified with silver triangular nanoplates. Limits of detection for iodide, bromide and chloride are 0.01, 0.02, and 0.04 mg L-1 respectively in case of the last mentioned paper. The method was applied to the analysis of samples having complex matrices, such as various seafood, preserves, bread, and natural waters, showing good accuracy of the analysis with recoveries of 95-105% and relative standard deviations not higher than 6%.
ABSTRACT
A new chemosensor in the form of indicator paper, which is sensitive to chlorine and bromine concentrations, is proposed. A simple technique of sensor preparation in a laboratory without expensive reagents is described. The method provides uniform and reproducible distribution of the reagent. A possibility to use the sensor for chemical analysis when combining with dynamic gas extraction with the application of scanner technologies and color image processing is demonstrated. Sensitive and selective techniques of chlorine, bromine, chloride, and bromide determination have been developed. The limits of detection of bromine, chlorine, bromide, and chloride have been found to be 0.06, 0.28, 0.5 and 1.4⯵molâ¯L-1 respectively. A scheme of successive determination of these analytes in the same sample including selective halides oxidation is proposed. In the simple and available set-up used for dynamic gas extraction, sample decomposition, oxidation of halide-ions and extraction of the formed halogen take place simultaneously while the color reaction of halogen interaction with the sensor is conducted out of the analyzed solution with reagents. This approach provides high selectivity and good analytical characteristics of analysis of such complex samples as foods, pharmaceutical formulations, and different water objects. The method is easy-to-use, cost-effective, time-efficient and promising for determination of other volatile compounds.
ABSTRACT
A method is described for sensitive and selective detection of iodine by using a paper strip modified with silver triangular nanoplates (AgTNPs). It is based on the extraction of iodine from a solution into a flow of air via dynamic gas extraction and transferring it through a reactive paper modified with AgTNPs. The interaction of AgTNPs with iodine results in a color change from blue to white. This can be visually detected and monitored by digital colorimetry. The dynamic gas extraction is highly selective for volatile compounds so that a sample pretreatment is minimal. Due to the sensitivity of AgTNPs for iodine, the limit of its detection is as low as 7 µg L-1, and the analytical range is of 20-200 µg L-1. The method also was applied in a new approach for determination of organic compounds that can interact with iodine. The organic compound is exposed to an excess of iodine, and this is followed by detection of residual iodine as described above. The method was applied to the determination of ascorbic acid, caffeine and the drug metamizole. Graphical abstract Schematic representation of a procedure of organic iodine-interacting compounds (Org.) determination. It is based on their iodination followed by gas extraction of the residual iodine, its interaction with silver triangular nanoplates and colorimetric detection with a scanner.
ABSTRACT
The article describes a novel approach towards improving selectivity of volatile compounds detection using metal nanoparticles. It is based on combination of sensitive optical detection using convenient nanoparticle-modified paper test strips and dynamic gas extraction improving selectivity to volatile compounds. A simple and inexpensive setup allowing for realization of this combination is described. Analytical prospects of the approach are shown by the example of chlorine determination in highly salted aqueous solutions using silver triangular nanoplates and digital colorimetry. The limit of detection is equal to 0.03mgL-1 and the determination range is 0.1-2mgL-1. This determination can be successfully carried out in solutions containing at least 2·105 greater molar amounts of Na+, K+, Zn2+, Cl-, SO42-, and H2PO4- with no sample pretreatment. The approach seems to be compatible with different types of nanoparticles with respect to detection of various analytes, thus having good opportunities for further development.
