ABSTRACT
Magnetic covalent organic frameworks are new emerging materials which, besides many other applications, have found unique applications in analytical chemistry as separating media and adsorbents. They have outstanding features such as special morphology, chemical and thermal stability, high adsorption capacity, good magnetic response, high specific surface area, uniform pore size distribution, strong π-π interactions with analytes and high reusability that makes reported studies on their properties and applications increased in the recent years. After discussing the methods of synthesis of MCOFs with different geometries that cause their special physic-chemical properties, this review focuses on their high potential which has been exhibited in various applications in extraction and pre-concentration of different analytes such as organic compounds, heavy metal ions and biological samples. The article also highlights the applications of magnetic covalent organic frameworks in other chemical analysis such as adsorbent and being used in sensors.
ABSTRACT
In this paper, a low cost and portable smartphone-based spectrophotometer with the purpose of measuring trace levels of two important anions, chlorine and nitrite ions in water samples, is introduced. This home-made spectrophotometer is made of Plexiglas, equipped with two LEDs as a light source, and a piece of DVD is acted as light dispersing element. Battery of smartphone was used as its power supply and spectral analysis was performed by a free software downloadable from Google Playstore. By using this lightweight spectrophotometer, various environmental samples were analyzed for their NO2- and Cl2 content in field. Good detection limits of 5.00â¯×â¯10-2â¯mgâ¯L-1 and 8.60â¯×â¯10-3â¯mgâ¯L-1 were obtained for chlorine and nitrite, respectively. The linear range for chlorine was 1.00-4.00â¯mgâ¯L-1 and this range for nitrite was 0.05-1.20â¯mgâ¯L-1. Reproducibility as relative standard deviation for both chlorine and nitrite was better than 8.75%. In order to investigate validity of data, results were compared to standard methods of measuring chlorine and nitrite, using both spectrophotometry and commercial kits which showed no difference between results obtained. This very simple to use and inexpensive device can be used many times, so can be considered as a low-cost alternative to the detection device of commercial kits.
ABSTRACT
Nearing 130 years since their introduction, liquid crystals (LCs) have found diverse applications in different fields of science, including chemical analysis. This review encompasses the history of LCs, reviews various types of them, and presents their current applications in analytical chemistry. Since most applications of LCs in analytical chemistry are for the fabrication of biosensors, these applications are discussed first. The high sensitivity of LCs to changes in their environment makes them ideal for such sensors. Using them, analyte concentrations as low as 1 pM have been detected. Another major application of LCs is in gas chromatography (GC) as stationary phases, which is described in the second part of this review. Using LCs in GC leads to better separations, higher sensitivity, and improved selectivity. Such phases provide higher stability in elevated temperatures and increased column life times. Finally, applications of LCs in electro-analytical chemistry will be described briefly.
Subject(s)
Biosensing Techniques , Chemistry Techniques, Analytical/methods , Liquid Crystals/chemistry , Humans , TemperatureABSTRACT
The purpose of this study was to investigate the feasibility of simultaneous optimization and removal of dyes, Malachite green (MG), Rhodamine B (RhB) and Cresol Red (CR) from aqueous solutions by using Sistan sand as an extremely low cost adsorbent. Factors affecting adsorption of the analytes on the sorbent were investigated experimentally and by using Taguchi and Plackett-Burman experimental design methods. In most cases, the results of these two models were in agreement with each other and with experimental data obtained. Taguchi method was capable to predict results with accuracies better than 97.89%, 95.43%, and 97.79% for MG, RhB, and CR, respectively. Under the optimum conditions, the sorbent could remove simultaneously more than 83% of the dyes with the amount of adsorbed dyes of 0.132, 0.109, and 0.120 mg g-1 for MG, RhB and CR on sand, respectively. Kinetic studies showed that pseudo second order is the best model of adsorption for all analytes. Thermodynamic parameters revealed that this process is spontaneous and endothermic.
ABSTRACT
Two new, rapid methodologies have been developed and applied successfully for the determination of trace levels of iodide in real water samples. Both techniques are based on a combination of in-syringe dispersive liquid-liquid microextraction (IS-DLLME) and micro-volume UV-Vis spectrophotometry. In the first technique, iodide is oxidized with nitrous acid to the colorless anion of ICl2(-) at high concentration of hydrochloric acid. Rhodamine B is added and by means of one step IS-DLLME, the ion-pair formed was extracted into toluene and measured spectrophotometrically. Acetone is used as dispersive solvent. The second method is based on the IS-DLLME microextraction of iodide as iodide/1, 10-phenanthroline-iron((II)) chelate cation ion-pair (colored) into nitrobenzene. Methanol was selected as dispersive solvent. Optimal conditions for iodide extraction were determined for both approaches. Methods are compared in terms of analytical parameters such as precision, accuracy, speed and limit of detection. Both methods were successfully applied to determining iodide in tap and river water samples.
