Sub-ppt level voltammetric sensor for Hg2+ detection based on nafion stabilized l-cysteine-capped Au@Ag core-shell nanoparticles

Journal of Solid State Electrochemistry - Bimetallic nanoparticles (BMNPs) have received considerable attention due to their distinctive properties when compared to the corresponding monometallic...     

Simple gas chromatographic method for the quantification of total cholesterol in fish meats

Six fish species-Cirrhinus mrigala (Morakhi), Labeo rohita (Danbhro), Catla catla (Thalli), Wallago attu (Jarko), Ctenopharyngodon idella (Grass), and Cyprimus carpio (Gulfam)--commonly found in the Pakistani Indus river, were selected for fat and cholesterol evaluation. Fat content was quantified by the Folch method and cholesterol content was determined by a simple GC method. The application of the proposed method to quantify cholesterol content revealed variations among the six breeds evaluated. The breeds studied contained 0.80-1.95% fat, indicating that all investigated fishes were lean; significant variation was found in cholesterol content, and ranged between 72 and 392 mg/100 g. Standard addition analyses showed that the method was accurate, as the recovery of cholesterol varied from 95 to 103%, with a coefficient of variance not more than 5.6%. The results showed that, after the development of suitable calibration, within 11 min, the cholesterol could be accurately determined by GC.     

A simplified UV spectrometric method for determination of peroxide value in thermally oxidized canola oil

The aim of present study was to develop a simple method on UV spectrometer for the determination of peroxide value (PV) of the frying oil. The basis of the PV determination was the stoichiometric reaction of triphenylphosphine (TPP) with the hydroperoxides present in frying oil to produce triphenylphosphine oxide (TPPO), which exhibits a readily measurable absorption band at 240 nm by ultraviolet region. The PV ranged between 0.15 and 11.66 meq. of active oxygen per kilogram of oil as the canola oil was heated from 0 to 12 h in the fryer at 180 °C. The proposed method was correlated with official AOCS titration method and best correlation coefficient (R² = 0.99525) was achieved, proving that there is no significant difference in the results. Therefore, developed method could serve as an alternative to the titration method, for the determination of PV in frying oils.     

Main fatty acid classes in vegetable oils by SB-ATR-Fourier transform infrared (FTIR) spectroscopy

The prospect of using single bounce attenuated total reflectance (SB-ATR)-Fourier transform infrared (FTIR) spectroscopy as a rapid quantitative tool to determine the main fatty acid groups present in different edible oils was investigated. Partial least squares (PLS) calibrations were developed using SB-ATR-FTIR spectra which were associated with fatty acid groups (saturated, trans, mono- and polyunsaturated) using quantitative data obtained by gas chromatography (GC). Good calibrations were obtained for all main four fat groups (saturated, mono, trans and polyunsaturated) with excellent precision. The coefficient of determination (R²), root mean square error of prediction (RMSEP) and bias for validation set were obtained as 0.999, 2.43 and 0.998 for saturated; 0.999, 1.850 and 0.003 for mono; 0.999, 0.625 and −0.001 for trans while for poly the values were 0.999, 1.170 and 0.003, respectively. The results of 13 validation samples for total saturated, mono, trans and polyunsaturated fats by FI-IR were found in the range of 8.16-55.16, 37.62-74.75, 0.20-18.16 and 1.36-62.35%, respectively. The present study shows that it may well be possible to expand the utility of SB-ATR-FTIR spectroscopy not only to provide isolated trans data, but also serve as a simple, rapid and quantitative means of categorizing the main groups present in the edible oils. The information obtained would be useful for meeting the new lipid nutritional labeling requirements.     

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

The synthesis of two [4]‐dendralene compounds incorporating thiophene‐(p‐nitrophenyl) donor–acceptor units is presented. The dendralenes adopt two different conformers in solution and solid state and the transformation between the structures can be controlled by light and heat. The electron‐donating components of the dendralenes are represented by bromothienyl (in 13 ) and ethylenedioxythiophene(EDOT)‐thienyl (in 15 ) end‐groups. The most facile transformation involves the isomerisation of donor–acceptor conjugated systems ( a conformers) into structures in which only the thiophenes are conjugated ( b conformers), and this process is driven by ambient light. The structures of the two conformers of compound 13 are confirmed by single‐crystal X‐ray diffraction studies and the structural changes in both compounds have been monitored by ¹H NMR spectroscopy and absorption studies. The transformations were found to be first‐order processes with rate constants of k=0.0027 s^?1 and k=0.00022 s^?1 for 13 and 15 , respectively. Density functional theory calculations at the B3LYP/6‐31G* level give credence to the proposed mechanism for the a → b conversion, which involves photoinduced intramolecular charge transfer (ICT) as the key step. The EDOT derivative ( 15 ) can be polymerised by electrochemical oxidation and a combination of cyclic voltammetry and UV/Vis spectroelectrochemical experiments indicate that the a conformer can be trapped and stabilised in the solid state.     

Evaluation of important fatty acid ratios in poultry feed lipids by ATR FTIR spectroscopy

A rapid, simple and reproducible single bounce attenuated total reflectance (SB-ATR) Fourier transform infrared (FTIR) spectroscopic method was developed for determination of the n − 6, n − 3 and ratio of n − 6:n − 3 polyunsaturated fatty acids (PUFAs) in poultry feed lipids using partial least squares (PLS) regression. Data for n − 6, n − 3 and ratio of n − 6:n − 3 was acquired by gas chromatography (GC) and used as a standard values for FTIR calibration. The best regression results were achieved using first derivatives of the 1475–650 cm⁻¹ spectral region for n − 6, n − 3 and ratio of n − 6:n − 3 with high regression coefficients (R²) of 0.999, 0.994 and 0.998, respectively and low RMSEP values of 1, 0.06 and 0.83, respectively. The results of the present study revealed that FTIR could be used for rapid and accurate determination of n − 6, n − 3 and ratio of n − 6:n − 3 PUFAs present in poultry feed lipids.     

CROSSING TIME AND RENEWAL NUMBERS OF TWO PH-RENEWAL PROCESSES

This paper considers how to find some joint distributions and their marginal distributions of crossing time and renewal numbers related to two PH-renewal processes by constructing an absorbing Markov proems.