Arvind K. Gupta

Application of Central Composite Design approach for removal of chromium (VI) from aqueous solution using weakly anionic resin: Modeling, optimization, and study of interactive variables

In this paper, response surface methodology (RSM) approach using Central Composite Design (CCD) is applied to develop mathematical model and optimize process parameters for Cr (VI) removal from aqueous streams using weakly anionic resin Amberlite IRA 96. The individual and combined effect of four process parameters, i.e. contact time, initial solution pH, initial Cr (VI) concentration and resin dose on Cr adsorption were studied. Analysis of variance (ANOVA) showed the relative significance of process parameters in removal process. Initial solution pH and resin dose were found to be more significant than contact time and initial Cr (VI) concentration. The second-order regression model was developed to predict the removal efficiency using Design Expert software. The optimal conditions to remove Cr from aqueous solution at constant temperature of 30°C and stirring speed of 250 rpm were found to be contact time 62.5 min, pH 1.96, initial Cr (VI) concentration 145.4 mg/L, and resin dose 8.51 g/L. At these conditions, high removal efficiency (93.26%) was achieved. FTIR and EDX analysis were conducted to interpret the functional groups involved during the Cr-resin interaction.

Kinetics of adsorptive removal of DEClP and GB on impregnated Al2O3 nanoparticles

Nanoparticles of AP-Al(2)O(3) (aero-gel produced alumina) have been produced by an alkoxide based synthesis involving aluminum powder, methanol, toluene and water. Thus produced alumina nanoparticles were characterized and the data indicated the formation of nanoparticles of alumina in the size range of 2-30 nm with high surface area (375 m(2)/g). Thereafter, these nanoparticles were impregnated with reactive chemicals. Adsorptive removal kinetics for DEClP (diethylchlorophosphate) and GB (isopropylmethylphosphonofluoridate, sarin) was monitored by GC-FID (gas chromatograph coupled with flame ionization detector) technique and found to be following pseudo first order reaction kinetics. Among impregnated AP-Al(2)O(3) nanoparticles based sorbent systems AP-Al(2)O(3) impregnated with 9-molybdo-3-vanadophosphoric acid (10%, w/w) was found to be the most reactive with least half-life values of 7 and 30 min for the removal of DEClP and GB, respectively, whereas unimpregnated AP-Al(2)O(3) nanoparticles showed the best adsorption potential among all studied systems. In addition to this, hydrolysis reaction {identified using GC/MS (gas chromatograph coupled with mass spectrometer) technique} was found to be the route of degradation of DEClP and GB on impregnated alumina nanoparticles.

Cardiovascular and respiratory changes following exposure to a synthetic toxin of Ptychodiscus brevis

The present study demonstrated cardiorespiratory effects of a synthetic phosphorus-containing ichthyotoxic metabolite elaborated by the marine dinoflagellate Ptychodiscus brevis in anaesthetised cats. The metabolite at a dose of 0.25-1.5 mg/kg i.v., resulted in a dose-dependent fall in blood pressure and such vasodepressor effect was associated with bradycardia. There is initial respiratory apnoea followed by increased rate and depth of respiration (hyperapnoea) following the administration of the toxin. The hypotensive response was accompanied by a decrease in aortic baroreceptor activity. The ECG showed atrioventricular conduction block, arrhythmia and depression of S-T segment and T wave which indicated coronary insufficiency. Vasodepressive property of the toxin is presumably muscarinic in nature as atropine counteracted the vasodepression.

Surface-mediated solid phase reactions : a simple, efficient and base-free synthesis of phosphonates and phosphates on Al2O3

Al2O3-supported solvent free condensation of alkylphosphonic dichlorides with alcohols at room temperature yielded phosphorus esters in excellent yields.

Efficient and Convenient One‐Pot Synthesis of Phosphoramidates and Phosphates

Abstract A simple and efficient one‐pot method is described for the synthesis of phosphoramidates/phosphates in excellent yields from dialkylphosphites and trichloroisocyanuric acid in acetonitrile and subsequent treatment with dialkyl amines/alcohols. The procedure is operationally simple, has reduced reaction times, and uses a one‐pot procedure.

Dichlorodimethyl Hydantoin: An Efficient Reagent for One-Pot Synthesis of CWC-Related O,O-dialkyl, N,N-dialkyl Phosphoramidates

A simple, rapid, economical, and efficient one-pot synthetic method for preparation of O,O-dialkyl, N,N-dialkylphosphoramidates (DADAPs) and phosphates has been developed.

p-Toluenesulfonic acid-Celite as a reagent for synthesis of esters of alkylphosphonic acids under solvent-free conditions

The coupling reaction of alkylphosphonic acids and alcohols on the surface of p-toluenesulfonic acid–Celite under mild and solvent-free conditions gave the corresponding phosphonates in excellent yields. This method provides a useful rapid synthesis of phosphonates for use in the unambiguous identification of chemical warfare agents.

Chromogenic and fluorogenic multianalyte detection with a tuned receptor: refining selectivity for toxic anions and nerve agents

In the present study, a chemical probe was finely tuned for the highly selective and sensitive chromogenic and fluorogenic detection of toxic anions and a nerve agent. Studies on the binding sites, signaling units and spacers led to a receptor molecule, i.e., 2,7-bis-[3-(4-cyanophenyl)thiourea] fluorene 2, which detected multiple analytes such as fluoride, cyanide, and a tabun mimic. The optical responses obtained from all the three analytes were quite distinct from one another. More importantly, we have been successful in demonstrating the highly specific chromo-fluorogenic detection of a tabun mimic over other chemical warfare agents and reactive and non-reactive electrophilic interferents. In an attempt to mimic real-life scenarios, the applicability of our protocol was further extended to demonstrate the presence of a tabun mimic on solid surfaces, in the gas phase and in a spiked soil sample.

Microwave Induced Synthesis of O,O-Dialkyl Dialkylpyrophosphonates under Solvent Free Conditions: Markers of Nerve Agents

This article describes a one pot, solvent free, microwave assisted synthesis of O,O-dialkyl dialkylpyrophosphonates (DADAPP) from O-alkyl alkylphosphonic chlorides 2a–j with 4-dimethylaminopyridine (DMAP) in the presence of water under microwave irradiation. The reaction takes place by the phosphonium salts, which are converted into the DADAPPs 4a–j. These DADAPPs are important markers of chemical warfare agents sarin, soman, and VX and their analogues. The method has several advantages over the conventional methods such as operational simplicity, high yield, and reduced reaction time.

Rapid Synthesis of O,O-Dialkyl Alkylphosphonates on TLC with Analytical Purity for the Verification Analysis of Chemical Weapons Convention

Reaction parameters for the rapid synthesis of O,O′-dialkyl alkylphosphonates and O-alkyl hydrogen alkylphosphonates were optimized using thin-layer chromatographic plates as a solid-supported platform under microwave irradiation. Immediate synthesis of these compounds with analytical purity is of paramount importance for the verification analysis of the Chemical Weapons Convention.