An enhanced method for the removal of methyl violet dye using magnetite nanoparticles as an adsorbent: Isotherm, kinetic and thermodynamic study.

A green method has been developed using Gilloy (Tinospora Cordifolia) shoot extract to synthesize magnetic nanoparticles (MNPs). A further modification of MNPs was performed using anionic surfactant sodium dodecyl sulphate (SDS), to remove cationic dye methyl violet (MV) efficiently from the solution. As an adsorbent, SDS modified MNPs (SDS-MNPs) were tested for their ability to remove MV dye. Synthesized MNPs were characterized by ultra violet-visible spectroscopy (UV-VIS), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). In batch adsorption experiments, the effect of adsorbent dosage, initial dye concentration, time, and pH was evaluated. The maximum adsorption capacity of the adsorbent for MV dye was found to be 174.2 mg g-1. The adsorption of dye onto the adsorbent followed Langmuir's isotherm. It was shown that the adsorption kinetics of dyes obeyed pseudo-second-order kinetics. Using thermodynamic parameters, spontaneous and exothermic adsorption was determined. As synthesized nanoparticles are magnetic in nature, regeneration and reusability of MNPs were investigated.

Selective Fluorometric Analysis of Hg(II) in Industrial Waste Water Samples.

The highly selective and sensitive fluorometric method has been developed for trace level determination of Hg(II) is based on photo-induced electron transfer between rhodamine-6G dye and metal complex. Quenching in fluorescence intensity by fluorescence resonance energy transfer (FRET) is due to interaction between metal ion complex and dye. The fluorescence emitted was measured at 510 and 550 nm, for excitation and emission wavelengths respectively. Possible interferences present in water samples, which could affect the analytical response are studied and determined. The calibration graph was dynamically linear from 0.002 to 0.05 mgL-1 of Hg(II) with limit of detection 7 × 10-4 mgL-1 and limit of quantitation 1.9 × 10-3 mgL-1. The Stern-Volmer constant (KSV) calculated for the quenching of R-6G with Hg (II) was 8.47 Lmg-1 s-1 at optimized reaction conditions. The proposed FRET based fluorometric method was applied successfully in different industrial wastewater samples with satisfactory outcome.

Casting of carbon cloth enrobed polypyrrole electrode for high electrochemical performances.

The present investigation deals with the fabrication of a novel flexible and highly conductive PPy electrode. This was made by festooning PPy nanoparticles on carbon cloth (CC) by using chemical liquid process. The developed porous PPy@CC composite have good flexibility with low weight (1.1 mg) and high electrical conductivity (89 Ω-1cm-1). Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction spectroscopy (XRD) confirmed the formation of PPy on carbon cloth. Scanning electron micrographs (SEM) reveals that the PPy nanoparticles are encapsulated in carbon cloth. The fabricated carbon cloth has been used for solid-state symmetrical supercapacitors (SC) and low-cost material for electrode in potential energy storage devices. These film electrodes showed much superior electrochemical performance i.e. high stability under different current density, encouraging energy density, lower internal resistivity and higher specific capacitance. Synthesized flexible PPy@CC composite electrodes have brilliant applications in various kinds of electrochemical energy storage devices.

Convenient and ultra-sensitive fluorescence detection of bovine serum albumin by using Rhodamine-6G modified gold nanoparticles in biological samples.

This study comprises a convenient, rapid and very sensitive method for the determination of bovine serum albumin (BSA). The technique is based on fluorescence resonance energy transfer (FRET) between Rhodamine-6G (R6G) acting as donor and gold nanoparticles (AuNPs) acting as acceptors. This method takes advantage of AuNPs that have high quenching efficiency, therefore the absorption spectra range shifts from 521 to 635 nm when aggregation of the AuNPs takes place. Furthermore, when R6G was electrostatically self-adsorbed to the citrate-stabilized AuNPs surface the fluorescence intensity was quenched. After addition of BSA, the fluorescence intensity of the R6G recovered as BSA induced aggregation of the AuNPs and the adsorbed R6G was released to the solution. The recovery of intensity displays a linear relationship with BSA concentration over the range from 0.8 × 10-11  M to 5.6 × 10-11  M. The detection limit for BSA was found to be 4.58 × 10-11  M. The proposed method exhibited rapid analysis with high selectivity for BSA determination in human urine, blood and serum samples.

Pharmacokinetic determination and analysis of nortriptyline based on GC-MS coupled with hollow-fiber drop-to-drop solvent microextraction technique.

AIM: A simple, sensitive and robust technique of hollow-fiber drop-to-drop solvent microextraction coupled with GC-MS has been successfully developed for the detection of antidepressant drug nortriptyline in human blood and urine samples. The recoveries of the drug from the spiked samples are found to be well within the range and appropriate to support the method. RESULTS: The LOD for the drug was obtained to be 0.007, 0.009 and 0.021 µg ml-1 in deionized water, urine and blood samples of human subjects, respectively. Linearity was obtained over the concentration range of 0.5-5.0 mg l-1 in deionized water with correlation coefficient 0.99672.

Determination of iron (III) in food, biological and environmental samples.

The nanodrop spectrophotometric (NDS) determination of iron (III) in water samples has been established. The proposed method is simple, selective and highly sensitive. The extraction of Fe (III)-thiocyanate complex was done by novel organic reagents such as N-phenylacetamide, N-alkylacetamide, (alkyl=butyl, hexyl and octyl group) in chloroform. The Fe (III) extract was examined in the strong acidic (HCl+H2SO4) solution. The maximum value of molar absorptivity was found to be 1.8×105Lmol-1cm-1 at λmax, 477nm (⩾9 fold enrichments) for N-octylacetamide (N-OAA). The method obeys the Beers Law within the range of 0.05µgmL-1-6.0µgmL-1. The detection limit and RSD value of the method were found to be 5ppb and 0.5906% respectively. The correlation coefficient, slope and intercept were calculated and found to be 0.9989, 0.1112, and 0.0048, respectively. The proposed method was successfully applied to the determination of trace amount of iron (III) in food, biological and environmental samples.

Kinetic and isotherm studies on adsorption of fluoride by limonite with batch technique.

Fluoride in drinking water has an intense effect on bones and teeth. The concentration of fluoride >1.5 mg l-1 in drinking water is harmful for human health. In the present study the naturally occurring geomaterial limonite (Iron Ore) has been used as the adsorbent for the investigation of defluoridation capacity by Batch adsorption technique in aqueous condition. Various parameters such as contact time, adsorbent dose, adsorbate concentration, adsorbent particle size and agitation speed at room temperature (298K) and pH (7?0.3), has been optimization for the adsorption of F- onto limonite. The initial rate of the adsorption was very fast and after 120 minutes it attained equilibrium. Three known Isotherm Models (Langmuir, Freundlich and Temkin) used to study the mechanism and nature of adsorption onto the surface of limonite. The experimental results are best fitted into the Langmuir and Temkin isotherm models (R2> 0.99). The average monolayer adsorption capacity (Qm) obtained for limonite is 0.269 mg g-1. The experimental data highlights that surface sites of adsorbent (limonite) are heterogeneous in nature and fits into a heterogeneous site binding model. The kinetic study revealed that the adsorption process followed Pseudo 2nd order model. The removal efficiency of limonite for the naturally high F- water sample (4.12 mg l-1) under optimized condition obtained 66.9%. The maximum adsorption capacity Qe (F- adsorbed) at equilibrium is calculated 2.208 mg g-1. The isotherm and kinetic studies reveal that limonite can be used as an adsorbent for fluoride removal. The OH-group of limonite acts as ion exchange with F- ion confirm by Fourier Transmission-IR spectroscopy analysis (FT-IR). XRD (X-ray Refraction Dispersive) peaks also give good evidence of surface adsorption onto limonite and surface morphology by Scanning electron microscopy (SEM) image. In the future we can use this technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly, minimal processing and easily available in the study area.

Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG < 0) and endothermic (ΔH > 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area.

Ionic liquid matrix-based dispersive liquid-liquid microextraction for enhanced MALDI-MS analysis of phospholipids in soybean.

Ionic liquid matrix (ILM) is found to be a very versatile substance for analysis of broad range of organic molecules in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) due to good solubility for a variety of analytes, formation of homogenous crystals and high vacuum stability of the matrix. In the present work, an ILM, cyno-4-hydroxycinnamic acid-butylamine (CHCAB) was employed in dispersive liquid-liquid microextraction (DLLME) as sample probe and matrix for extraction and ionization of phospholipids from food samples (soybean) prior to MALDI-MS analysis. With the employed technique, 8-125 fold improvement in signal intensity and limit of detection were achieved for the analysis of phospholipids. The best extraction efficiency of phospholipids in ILM-DLLME was obtained with 5min extraction time in presence 30mg/mL CHCAB and 1.2% NaCl using chloroform as an extracting solvent and methanol as a dispersing solvent. Further, the developed ILM-DLLME procedure has been successfully applied for the analysis of phospholipids in soybean samples in MALDI-MS.