Ultraviolet photolysis assisted mineralization and determination of trace levels of Cr, Cd, Cu, Sn, and Pb in isosulfan blue by ICP-MS

Isosulfan blue dye is used in sentinel node mapping technique to evaluate breast cancer patients where determination of different trace elements is required. A UV-photolysis assisted mineralization of isosulfan blue is described here for the determination of trace elements (Cr, Cd, Cu, Sn and Pb) by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In the present study advanced oxidation processes such as UV, UV/H₂O₂, and UV/H₂O₂/HNO₃ have been assessed and compared for the degradation and mineralization of isosulfan blue dye. The extent of mineralization was determined on the basis of total organic carbon (TOC) measurement. The adopted procedure (UV/HNO₃/H₂O₂) provided very low TOC content (0.5%), corresponding to a mineralization efficiency of > 99%. With the present procedure, the use of dynamic reaction cell (DRC) or collision cell was not required for chromium determination which suffers interference from the presence of carbon. Method detection limits were 0.0028, 0.0021, 0.016, 0.007, and 0.005 μg g^? 1 for Cr, Cd, Cu, Sn and Pb respectively. The values obtained by the proposed method were cross-validated by those obtained by ETAAS analysis. The expanded uncertainties in the measurement at 95% confidence level (coverage factor 2) are in the range of 13.7–25.8%.     

Preparation and characterization of nanocrystalline CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> deposited on SiO<Subscript>2</Subscript>: in situ sol–gel process

In situ base catalyst assisted sol–gel process is used for the synthesis of nanocrystalline CoFe₂O₄ deposition on SiO₂ particles. The SiO₂ particles were prepared using base catalyst assisted sol–gel process and the consecutive formation and deposition of nanocrystalline CoFe₂O₄ on SiO₂ particles was monitored using Powder X ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric And Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy (SEM–EDS) and High Resolution Transmission Electron Microscopy (HRTEM). The crystallite size of CoFe₂O₄ is calculated using Scherrer’s formula and it is found to be 8 nm. The HRTEM images and selective area electron diffraction (SAED) results confirmed the formation of nanocrystalline CoFe₂O₄ particles deposited over SiO₂ spheres.     

First stereoselective total synthesis of pectinolide H

The stereoselective total synthesis of bio-active pectinolide H (1) is described. Midland’s asymmetric reduction, Sharpless dihydroxylation reactions are involved in generating the stereogenic centers at C-4′, C-5 and C-1′. Other key steps in the synthesis are Sonogashira cross coupling, Z-selective Still–Gennari olefination, one-pot acetonide deprotection–lactonization, and Lindlar’s reaction. This offers a distinctive strategy for the synthesis of γ-lactones.     

LC-PDA and LC-ESI-MS separation and determination of process-related substances arising from stilbene-type fluorescent whitening agents. Application to monitoring of their photodegradation products in industrial effluents and aqueous environmental systems

A simple and rapid gradient elution high-performance liquid chromatographic method using photodiode array and electrospray ionization mass spectrometric detectors was developed for separation and determination of the process-related substances and photodegradation products of stilbenesulfonic acids, viz. 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNSDA), 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSDA), and 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDA) in industrial waste waters. Gradient elution was carried out using ammonium acetate and acetonitrile as mobile phase and an Inertsil-ODS 3V column for separation. The negative-ion electrospray ionization mass spectra containing [M-H]- ions of sulfonic acids allowed molecular mass determination of unknowns and the structures were proposed on the basis of the fragment ions in the MS/MS spectra.     

Organic reactions in water: an efficient one-pot synthesis of acyloxiranes from Baylis-Hillman adducts using hypervalent iodine

Treatment of Baylis-Hillman adducts with iodosobenzene (PhIO) in the presence of a catalytic amount of KBr in water at room temperature afforded the corresponding acyloxiranes in good yields.     

Tertiary Butyl Nitrite Triggered Nitration of Phenols: Solvent‐ and Structure‐Dependent Kinetic Study

Nitration of phenols with tertiary butyl nitrite (TBN) obeyed second‐order kinetics with a first‐order dependence on [TBN] and [phenol] under acid‐free conditions. Reaction rates were significantly altered by a change in the dielectric constant and other physical properties of solvent. The rate of nitration increased with an increase in temperature (303–323 K) in different solvent media (acetonitrile, dichloroethane, CCl₄, dimethyl formamide (DMF), and toluene). The rates of nitration (log k) could not fit into either Amis or Kirkwood plots [log k’ vs. (1/D) or [(D – 1)/(2D + 1)], but the trends were better explained by the basic form of multivariate linear solvent energy relationships (MLSER) suggested by the Koppel and Palm approach on the one hand and the Kamlet and Taft approach on the other hand. These observations probably substantiate that cumulative contributions of basic solvent parameters (equilibrium as well as frictional solvent effects) and solvent–solute interactions for solvation of transition state during nitration of phenols. Reaction rates accelerated with the introduction of electron‐donating groups and retarded with electron‐withdrawing groups. Accordingly, the reactivity of structurally different phenols was found to follow the following sequence: p‐OH > p‐MeO > p‐Me > H > m‐Me > p‐Cl > p‐Br > m‐Cl > p‐NO₂ > m‐OH. The results are interpreted by Hammett's theory of linear free energy relationship. The reaction constant (Hammett's ρ) is a measure of the sensitivity of the reaction toward the electronic effects of the substituent. The rho (ρ) values obtained from the present experiments are fairly large negative values (ρ < 0), indicating attack of an electrophile on the aromatic ring. An increase in temperature decreases the reaction constant (ρ) values. According to Exner, ρ values for a given reaction are influenced by the temperature according to the following relation: ρ = A [1 – β/T]. Obtained “isokinetic temperature (β)” values are in the range of 225–290. These values are far below the experimental temperature range (303–323 K), indicating that the entropy factors are probably more important in controlling the reaction. This point can be seen from the negative entropy values and linearity of multiple linear regression analysis (MLRA). Furthermore, in the present study, rate constants for TBN nitration of ortho‐substituted phenols could not fit into Taft's plots of log(k/k_CH3) versus σ* or, E_s or combined Taft's relationship. However, Charton's MLRA of the log k with polar, resonance, steric, hydrophobicity, and molar refractivity showing a very good linear relationship was obtained. It is of interest to note that when log k_exp values are correlated with log k_cal a perfect linearity is obtained with a correlation coefficient of unity, indicating the consonance between experimental and calculated rate constants in the present work.     

Tautomeric equilibria in 8-oxopurines: Implications for mutagenicity

Free-radical-induced DNA damage by ionizing radiation leads to a number of oxidized purines, of which 7H-8-oxoguanine (8OG) and 7H-8-oxoadenine (8OA) are predominant and known to cause an appreciable amount of cellular damage. A detailed quantum mechanical study at various levels of theory in both the gas phase and in an aqueous solution has been carried out in order to assess the tautomeric preferences of the bases. The calculated energies of various plausible tautomers suggest that at higher levels of ab initio theory with inclusion of electron correlation, the 8-keto-6-enolic form of 8-oxoguanine (8OG2) would predominate over the 6,8-diketo form (8OG1) in the gas phase whereas the 6-amino-8-keto form (8OA1) predominates over the other possible tautomers of 8-oxoadenine. Aqueous solvation, however, changes the gas-phase order for 8-oxoguanine, 8OG1 turning out to be the major tautomeric species in an aqueous medium. The estimated free energies of hydration by polarized continuum models are indicative that the mutagenically significant amounts of minor tautomeric forms of 8-oxoguanine and 8-oxoadenine exist in the aqueous phase and might be held responsible for inducing transversional as well as transitional mutations.