Design and application of potentiometric sensors for the determination of mefenamic and phenylanthranilic acids.

Characteristics, performance and applications of potentiometric membrane sensors are described for the determination of mefenamic and phenylanthranilic ions. Ion associates of mefenamic, ClO4-, and phenylanthranilic ions with crystal violet (counter-cation) as ion exchange sites have been used as ionophores in the plasticized one- and two-layer membrane ion-selective electrodes. The LOD is reported to be 8.4 × 10-5 M for mefenamic acid, and 5.1 × 10-5 M for phenylanthranilic acid. The cations of basic dyes (crystal violet) are characterized by significant delocalization of the positive charge and polarizability. This may explain the better selectivity of the developed sensors. These sensors were used for the direct assay of mefenamic and N-phenylanthranilic acids in model solutions and applications studied in commercial pharmaceutical preparations.

Sunlight driven photocatalytic degradation of organic pollutants using a MnV2O6/BiVO4 heterojunction: mechanistic perception and degradation pathways.

In the field of photocatalysis, fabrication of a heterojunction structure with effective charge separation at the interface and charge shift to enhance the photocatalytic activity has acquired extensive consideration. In the present investigation, MnV2O6/BiVO4 heterojunction samples with excellent photocatalytic performance under sunlight irradiation were conveniently synthesized by a hydrothermal technique, and characterized by UV-Vis, FTIR, XRD, FESEM, HRTEM, PL, BET and XPS techniques. The prepared samples were investigated as photocatalysts for degrading MB and RhB dyes under sunlight. Among various samples of MnV2O6/BiVO4, the S-V hetero-junction sample exhibited maximum photocatalytic activity with 98% and 96% degradation of MB and RhB dyes, respectively, in 6 and 35 min. The high photocatalytic activity of MnV2O6/BiVO4 may be due to the successful generation and shift of charges in the presence of visible light. The average reduction of chemical oxygen demand (COD) was found to be 75% after irradiation with direct sunlight. In the degradation process of dyes, superoxide anion radicals were the main responsive species, as revealed by trapping experiments. The degradation efficiency of MnV2O6/BiVO4 heterojunction did not diminish even after four cycles. In addition, the catalytic performance of the fabricated heterojunction was also explored for reducing 4-nitrophenols (4-NP) by using NaBH4. Absolute conversion of 4-NP to 4-aminophenol (4-AP) occurred without the production of intermediate byproducts.

A voltammetric method for Fe(iii) in blood serum using a screen-printed electrode modified with a Schiff base ionophore.

Herein, a potent electrochemical ionophore (SMS-2) based on a Schiff base has been used for the modification of a screen-printed electrode (SPE). The modified disposable electrode can selectively detect ferric ions in an aqueous medium. Redox behavior of the proposed strip was characterized using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Incorporation of the ligand in the ink of the SPE enhanced the analytical performance of the electrode, and its surface modification was confirmed by SEM and EDX analysis. Shifting/quenching of the cathodic peak potential of the ionophore after binding with Fe(iii) ions was used to detect and measure the ferric ion concentration. This sensor can identify Fe(iii) in the detection range from 0.625 µM to 7.5 µM. The modified SPE can selectively detect ferric ions in the presence of many other interfering ions and has been successfully used to determine the Fe(iii) content in blood serum samples. The metal-ionophore complex structure was optimized using DFT calculations to study the energetics of the metal-ionophore interactions.

Selectivity enhancement of Arsenazo(III) reagent towards heavier lanthanides using polyaminocarboxylic acids: a spectrophotometric study.

A new study has been conducted to quantify lanthanide(III) ions using Arsenazo III-polyaminocarboxylic acid (PACA) system. The study disclosed two different analytically important information: (i) λmax of lanthanide-Arsenazo III complexes for lighter lanthanides like Ce(III) and Nd(III) did not shift from its original position on addition of PACA and (ii) for heavier lanthanides like Dy(III), Tm(III) and Lu(III) a new λmax at 538 nm was observed, while wavelengths at 610 nm and 654 nm were disappeared in presence of ethylenediaminetertracetic acid (EDTA) and trans-1,2-Diaminocyclohexane-N,N,N',N'-tetraacetic acid (DCTA), further the intensity of peak decreased with increase in lanthanide(III) ion concentration. Effect of ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) and N-(2-hydroxyethyl) ethylenediamine-N,N',N'-triacetic acid (EDTA-OH) on Arsenzo(III)-Ln(III) complex is very weak and there is no analytically importance of such interaction. Moreover, this work confirms that Nd(III) and heavy lanthanides can be successfully determined with high accuracy in the working range of concentration of these metal ions.

Epidemiological study on healthy subjects affected by agriculture crop-residue burning episodes and its relation with their pulmonary function tests.

Impact of agriculture crop-residue burning (ACRB) was studied on pulmonary function tests (PFTs) of 50 healthy subjects (13-53 years). Human subjects with no previous history of lung disease were residents of five sampling sites. Investigations were carried out from February 2007 to January 2010 using spirometry. Simultaneously, concentration levels of suspended particulate matter (PM) and fine particulates (PM2.5 and PM10) were monitored using high volume sampler and Anderson Cascade Impactor, respectively. The PFTs show a significant (p < 0.05) decrease, while PM shows momentous increase during exhaustive burning of wheat and rice crop residues. Effect of ACRB on the peak expiratory flow rate (PEF) is more than that on force expiratory flow (FEF25-75%). The PEF and FEF25-75% recovered to some extent on completion of burning period, while PFTs like force vital capacity and force expiratory volume did not show a significant improvement. Due to greater concentration of fine particulates during rice crop-residue burning (CRB) than wheat CRB, there was a greater effect on pulmonary functions. The ACRB, in general, poses more effect on the lower and upper age groups in comparison to the middle age group subjects. All the analyses are well supported with large significant levels (p < 0.05) obtained by using the paired t-test.

Effects of exposure to rice-crop residue burning smoke on pulmonary functions and oxygen saturation level of human beings in Patiala (India).

Pulmonary Function Tests (PFTs) like Force Vital Capacity (FVC), Force Expiratory Volume in one second (FEV1), Peak Expiratory Flow (PEF) and Force Expiratory Flow between 25 and 75% of FVC (FEF(25-75%)) and Oxygen Saturation (SpO2) level of 50 healthy inhabitants with respect to rice crop residue burning were investigated for three rice cultivation periods from 2007 to 2009. The subjects were residents of five sampling sites selected in Patiala city. Concentration of Suspended Particulate Matter (SPM), Sulfur dioxide (SO2), Nitrogen dioxide (NO2) and Particulate Matter (PM) of size less than 10 and 2.5 µm (PM10 and PM2.5) were measured by using High Volume Sampler (HVS) and Cascade Anderson Impactor. Results show that rice crop residue burning increases the pollution level in the ambient air, and PFTs undergo a significant decrease in their respective values. No significant change was seen in SpO2 level during rice crop residue burning. In 2008, an increase of 10 µg m⁻³ in PM2.5, PM10, SPM and NO2 was associated significantly with decrease in FVC in percentages predicted -1.541, -1.002, -1.178, -0.232%, respectively. The decrease in air quality due to open rice crop residue burning has sub acute effect on pulmonary functions of healthy subjects and that SO2 and NO2 have less adverse effects on pulmonary functions than with different size Particulate Matter.

Study of size and mass distribution of particulate matter due to crop residue burning with seasonal variation in rural area of Punjab, India.

Emission from field burning of agricultural crop residue is a common environmental hazard observed in northern India. It has a significant potential health risk for the rural population due to respirable suspended particulate matter (RSPM). A study on eight stage size segregated mass distribution of RSPM was done for 2 wheat and 3 rice crop seasons. The study was undertaken at rural and agricultural sites of Patiala (India) where the RSPM levels remained close to the National Ambient Air quality standards (NAAQS). Fine particulate matter (PM(2.5)) contributed almost 55% to 64% of the RSPM, showing that, in general, the smaller particles dominated during the whole study period with more contribution during the rice crop as compared to that of wheat crop residue burning. Fine particulate matter content in the total RSPM increased with decrease in temperature. Concentration levels of PM(10) and PM(2.5) were higher during the winter months as compared to that in the summer months. Background concentration levels of PM(10), PM(2.5) and PM(10-2.5) were found to be around 97 ± 21, 57 ± 15 and 40 ± 6 µg m(-3), respectively. The levels increased up to 66, 78 and 71% during rice season and 51, 43 and 61% during wheat crop residue burning, respectively. Extensive statistical analysis of the data was done by using pair t-test. Overall results show that the concentration levels of different size particulate matter are greatly affected by agricultural crop residue burning but the total distribution of the particulate matter remains almost constant.

8-hydroxyquinoline based neutral tripodal ionophore as a copper (II) selective electrode and the effect of remote substitutents on electrode properties.

New PVC membrane ion selective electrodes based on 1,3,5-Tris(8-quinolinoxymethyl)-2,4,6-trimethylbenzene (MO8HQ) are reported. The basic sensing material belongs to the group of tripodal ionophores. Also their derivatives prepared by placing suitable substitutents at fifth position of 8-oxine moiety, i.e, 1,3,5-Tris(5-chloro-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5CHQ), 1,3,5-Tris(5-benzoyl-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5BHQ) and 1,3,5-Tris[(5-phenylhydroxymethylene)-8-quinolinoxymethyl]-2,4,6-trimethylbenzene (HYD-8HQ) ionophores have also been used to make copper-selective membrane electrodes. Among all the four electrodes, MO8HQ and HYD-8HQ ionophores based electrodes show excellent response towards Cu (II) ions. The electrodes having composition 33% PVC, 4% MO8HQ and 63% dibutyl phthalate (DBP) and 33% PVC, 6% HYD-8HQ, 63% dibutyl phthalate (DBP) exhibit a good Nernstian response to Cu (II) ions in the range of 1.0 x 10(-6) to 1 x 10(-1) M. The electrode shows a reasonably fast response time of 15 s. The effect of pH and electrode response is also reported. It shows good selectivity for Cu (II) ions in comparison to heavy metal ions, transition metal ions and for alkali and alkaline earth metal ions. The electrode response and selectivity remains unchanged for at least 5 months. The electrode can be used as an indicator electrode in the potentiometric titration of Cu (II) ions with EDTA.

PVC-based dicyclohexano-18-crown-6 sensor for La(III) ions.

A new ion-selective electrode (ISE) based on dicyclohexano-18-crown-6 (DC18C6) as a neutral carrier is developed for lanthanum(III) ions. The electrode comprises of dicyclohexano-18-crown-6 (6%), PVC (33%), and ortho-nitrophenyl octyl ether (o-NPOE) (61%). The electrode shows a linear dynamic response in the concentration range of 10(-6) to 10(-1)M with a Nernstian slope of 19mV per decade and a detection limit as 5x10(-7)M. It has a response time of <30s and can be used for at least 5 months without any significant divergence in potentials. The selectivity coefficients for mono-, di-, and trivalent cations indicate good selectivity for La(III) ions over a large number of interfering cations. The sensor has been used as an indicator electrode in the potentiometric titrations of La(III) with EDTA. The membrane is successfully applied in partially non-aqueous medium. It can be used in the pH range 4-9.

Metal ion effect on BOD exertion at different temperatures.

The toxic effect of metal ions like chromium (Cr3+), cobalt (Co2+), nickel (Ni2+), copper (Cu2+), cadmium (Cd2+) and lead (Pb2+) on biochemical oxygen demand (BOD) of synthetic wastewater samples has been studied at different temperatures i.e., 15 degrees C, 20 degrees C, 25 degrees C and 30 degrees C. Experiments were conducted for BOD exertion in presence (10 ppm of each metal ion) and in the absence of metal ions at different temperatures. Transition metal ions like Cr3+, Co2+, Ni2+ and Cu2+ show an increase in relative percentage inhibition with increasing atomic number. BOD inhibition in presence of Cd2+ and Pb2+ is relatively large. The metal ions under study are found to be highly toxic to microbes.