Volume 51, Issue 6

A new method to determine glass corrosion/etching is presented. The method enables a rapid screening of formulations in terms of their glass etching tendency as well as identification of the main components responsible for giving rise to the etching. Up to four formulations can be evaluated during one day. The high sensitivity of the QCM-D instrument enables measuring the etching of thicknesses less than one nm. Therefore, the technique can be used efficiently to screen components in the formulations and aid in the development phase of new optimised dishwash detergent formulations. In a planned work we will investigate the correlation between the etching rate of thin sputtered glass films at the surface of QCM-D crystals and good performance in a standardized dishwasher test using melt-quenched glasses.

Simple, sensitive and economic spectrofluorimetric method has been described for the determination of chloroquine phosphate in pure form, pharmaceutical formulations and spiked human plasma. In the developed method, fluorescence intensity of chloroquine phosphate was enhanced with 0.4 M sodium dodecyl sulfate in basic media of pH 10 at room temperature. The excitation and emission wavelengths of the fluorescent chloroquine phosphate are 330 nm and 369 nm respectively. The developed approach has a broad linear range (0.03–5 μg mL −1 ) with a correlation coefficient of 0.9976. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 3.38 × 10 −3 μg mL −1 and 1.12 × 10 −2 μg mL −1 respectively. The common additives and co-administered medications were investigated for their interferences effect in the assay. The method was validated statistically through recovery studies and successfully applied to chloroquine phosphate determination in bulk powder, pharmaceutical preparation and spiked human plasma samples. The percent recoveries were found to be in the range of 99.42–100.46 % for bulk powder, 97.48–101.21 % for pharmaceutical formulations and 96.49–98.48 % for spiked human plasma.

Cationic surfactants are mainly used for fabric softening in laundry applications. Esterquats are one class of cationic surfactants and are superseding other existing cationic surfactants on account of their excellent biodegradability. However, indigenous and cost-effective production of esterquats poses new challenges for the researchers. The availability of rice bran fatty acids and its price structure in Indian scenario makes this fatty feedstock quite lucrative for cost-effective synthesis of cationic surfactants. In the present study, esterquats based on rice bran fatty acids (RBFAs) were synthesized by using different alkanolamines i. e. diethanolamine (DEA) and triethanolamine (TEA) and dimethyl sulphate (DMS) for obtaining cationic surfactants which was used as active softener ingredient. For this purpose, esterquats have been synthesized by esterification of RBFAs and alkanolamines to recover diesters followed by the subsequent quaternization of diesters by DMS. It was found that the optimum reaction conditions for esterification of RBFAs and DEA was 140 °C and 3 h of duration. However, for RBFAs and TEA, it was found to be 140 °C and 4 h of duration. The chemical structures of diesters and esterquats were confirmed by FT-IR and NMR spectra. Studies of surface active and performance properties of these surfactants showed that esterquats based on TEA had better surface active and performance properties as compared to DEA based esterquats. The synthesized cationic surfactants when mixed with nonionic surfactant showed better performance properties as compared to the nonionic surfactant alone.

Guerbet hexadecyl sulfate (C 16 GS) was synthesized by sulfating Guerbet hexadecyl alcohol (C 16 GA) with SO 3 as the sulfating agent and dichloroethane as the solvent. The structure of C 16 GS and C 16 GA was confirmed by IR and NMR. Their surface tension, wetting, emulsifying and foaming properties were tested and compared with that of sodium dodecyl sulfate (SDS). It is found that C 16 GS shows better surface activity than SDS, with both the critical micelle concentration (CMC) and surface tension at CMC (γ CMC ) of C 16 GS lower than that of SDS. Contact angle data demonstrated that C 16 GS exhibits better wetting ability on Teflon surface than SDS. As concentration increases, both the contact angle of C 16 GS and SDS decreases first and then remains constant. The only exception is the 0 s contact angle of C 16 GS decreases first and then increases. The contact angle of SDS becomes the smallest and reaches a plateau at the concentration of CMC. However, the contact angle of C 16 GS reaches the smallest and levels off at the concentration of 2.5 g/L which is much higher than the CMC of C 16 GS. C 16 GS also has a better performance of emulsifying soybean oil and paraffin than SDS. As for the foaming property, C 16 GS has a similar foamability to SDS, but shows worse foam stability than SDS.

The synthesis and structural analysis of glucosamide surfactants of the general formula C n H 2n+1 NH(CH 2 ) 6 NHCO(CHOH) 4 CH 2 OH (n = 8, 10, 12) were described, and the surface activity properties of the surfactants were studied, and the interfacial tensions between n -octane and the aqueous surfactant solution were measured. N -alkylhexanediamines were synthesized by the alkylation of the 1,6-hexanediamine with alkyl bromide. The glucosamide surfactants, N -alkyl- N ′-glucosylhexanediamine (C n GA), were prepared by amidation of the precursor diamine with D-gluconic acid δ-lactone. They were structurally characterized by IR, 1 H NMR and MS. They reduced the surface tension of water to approximately 28–33 mN · m −1 at concentration levels of (0.2–1.0) × 10 −3 mol · L −1 , and reduced the interfacial tensions between n -octane and the aqueous surfactant solution to approximately 1–2 mN · m −1 at concentration levels of (0.3–4.2) × 10 −3 mol · L −1 .

The purpose of this paper is to describe a more efficient catalyst for the synthesis of lauraldehyde glycerol acetal. Catalytic effect of methane sulfonic acid and p -toluenesulfonic acid were compared. With a mixture of 0.67 wt.% methanesulfonic acid in relation to lauraldehyde, equimolar amounts of glycerol and lauraldehyde being stirred at 110 °C for 2.5 h, the yield of the product was 76.32 %. When p -toluenesulfonic acid was used, the amount of the catalyst was 0.91 wt.% and the yield of the product was 62.91 % after reacting for 2.5 h at 120 °C. The result reveals that methane sulfonic acid is more efficient. Surface tension measurements showed that critical micelle concentration of the product catalyzed by methanesulfonic acid was 5.33 × 10 −5 mol · L −1 , and at this point the surface tension could achieve about 24 mN m −1 .

Cr(VI) is introduced into environment as a byproduct of industries. It is highly toxic. Biosorption of hexavalent chromium by various types of sawdust appears as a very cost-effective alternative for decontamination of Cr(VI) bearing effluents. In this work water extract of siris sawdust is used for the bioremediation of hexavalent chromium. Cr(VI) ions were reduced to Cr(III) ions as a result of oxidation of organic components present in the water extract of siris sawdust. Formation of Cr(III) is proved by UV-VIS spectroscopy. Functional groups involved in the reduction of Cr(VI) are characterized by FTIR spectroscopy. Bioremediation rate is increased by the use of anionic surfactant sodium dodecylsulphate (SDS) and neutral surfactant Triton-X-100 (TX-100). Here they act as micellar catalyst. Formation of micelles which is responsible for the catalysis of the process is proved by SEM and optical images of the solution. In absence of surfactants 39 % of the total chromium(VI) is reduced within 531 h whereas removal percentage increases upto 54 % in presence of TX-100. Again in presence of SDS the reduction process is almost 99 % complete within 531 h.

The synergic effect between cationic Gemini imidazolium surfactant [C 12 (Bim) 2 -2Br] and anionic surfactant sodium dodecyl sulfate (SDS) on the physicochemical properties of the W/O microemulsions was studied. The properties include the molar fraction of the alcohol at the interfacial layer (X a i ), the molar fraction of the alcohol in the oil phase (X a o ), and the Gibbs free energy change (−Δ G o → i o ) of transferring alcohol from the continuous oil phase to the interfacial layer. The W/O microemulsion systems contain C 12 (Bim) 2 -2Br-SDS/butan-1-ol/octane/5 % NaCl solution. The values of X a i and X a o obtained from the W/O microemulsions containing the mixed surfactants are smaller than that of the microemulsion systems containing the single surfactant C 12 (Bim) 2 -2Br or SDS, while the values of −Δ G o → i o are larger. This showed the existence of synergism between [C 12 (Bim) 2 -2Br] and SDS. The effects of alcohols, alkanes and NaCl concentrations on the values of X a i , X a o and −Δ G o → i o , in the W/O microemulsions stabilized by C 12 (Bim) 2 -2Br and SDS were also investigated and discussed.

A series of models, based on artificial neural networks, of the percolative behaviour of AOT microemulsions in the presence of crown ethers as additives have been developed. Input variables, related to the chemical structure of crown ethers and their packing with surfactant film, have been selected. As a result, a model has been chosen with a good forecast capability for percolation threshold of such microemulsions.

A junction of emeraldine salt (ES [BF 4 − ]) doped by [BMIM] [BF 4 ] may be preferred over the other junctions due to its low ideality factor and maximum rectification ratio. Schottky barrier diode based on composite of polyaniline (ES [BF 4 − ]) with polystyrene has been created and characterized using aluminium as Schottky contact and argent as an ohmic contact. The observed current–voltage characteristics can be satisfactorily fitted using the modified Schottky equation. Capacitance–voltage (C–V) in reverse bias and current–voltage (I–V) plots indicates a rectification. Various junction parameters were calculated from the temperature dependent I – V and C – V data and discussed. These results indicate that the composite materials have better mechanical strength and diode quality compared to the pure semiconducting polymer.