Chemical Science International Journal

Gradient elution is widely applied in analytical chromatography to reduce separation time and improve selectivity. However, the development and optimization of high-performance liquid chromatography (HPLC) gradient methods is arduous and time-consuming. In this paper, we demonstrate a solvatic sorption model to predict the retention time for phenylisothiocyanate derivatives of amino acids in a multi-step gradient reversed-phase HPLC. This model uses zero approximation level predictions. Rather, we use structural formulae and column and mobile phase properties as a “first guess” to develop the HPLC method before further optimization and prediction of the best multi-step gradient profile. The gradient elution mode with mobile phases modified with methanol and acetonitrile was used and verified the efficiency of different stationary phases. This approach provides good predictions of retention time values achieved after the first approximation step—this uses the data from only one experimental run.

Earlier efforts have been concerned with the association of Ruthenium octahedral complexes with DNA. Since the positively charged ruthenium species has been found to associate with the electron rich major groove of double-stranded DNA, it was proposed the addition of cationic sites on the ligands attached to ruthenium would facilitate such association. Thus, we have synthesized several series of octahedral ruthenium complexes bearing ligands having within themselves cationic sites. These have been investigated in their interaction with calf thymus DNA using fluorescence titration analysis. The introduction of the cationic ligands has been found to exhibit enhanced association of the ruthenium (II) species with the DNA as compared to those without such ligands, in keeping with the original concept. This work leads us to conclude that this line of investigation can lead to useful pharmaceutical agents.

In this work, micro-fibrillated cellulose (MFC) was prepared from sawdust and characterized by FTIR, WAXRD, and TGA. The MFC was synthesized by several steps such as alkali treatment, followed by NaClO₂ bleaching and acid hydrolysis. The acid hydrolysis was performed by three different H₂SO₄ concentrations (1N, 3N and 5N) whereas other conditions were remained unchanged. MFC were exhibited the identical peaks in FTIR spectra. The oxidation reaction took place during the MFC preparation by using high concentrations of acid which was detected by FTIR spectra. The crystallinity index of prepared MFC was measured by peaks at 16.2º and 22.2º (2θ angles) of WAXRD curves. The crystallinity index was increased with acid concentration up to 1N H₂SO₄ and thereafter decreased. The TGA results showed that the MFC degrade earlier temperature compare to the bleached pulp. The peaks of differential thermo-gravimetric curves (DTG) were shifted to lower temperature with the increase of acid concentration during hydrolysis of bleached pulp.

The mechanism of iodate oxidation by methylthioninum chloride in acidic medium was investigated at 29±1ºC. The oxidation reaction is first order in both oxidant and reductant. The rate of reaction was unaffected by increase in ionic strength, dielectric constant, added cations and anion. The reaction rate showed positive acid dependence and obeys the rate law of

-d[MB] =  a + b[H⁺][MB]            

    dt

where a =  1.19  dm³ mol^-1 s^-1, b = 0.628  dm³ mol^-1 s^-1 at 29±1°C, [H⁺] = 0.10 mol dm^-3, 1.0 mol dm^-3  (NaClO₄) ionic strength and λ_max = 663 nm. Investigation of spectroscopic test did not indicate the formation of intermediate complex during the course of the reaction. In line with the data obtained, plausible mechanism in favour of outer-sphere mechanism has been proposed.

Undried coir cellulose was prepared by chlorite bleaching method and hydrolyzed by 50% sulphuric acid to obtain highly crystalline nanocellulose. The proximate analysis of the coir fibre such as; moisture, ash, crude fibre, protein and its mineral composition were investigated using the AOAC standard protocol. The effect of hydrolysis on coir cellulose morphology was investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). SEM, TEM and AFM images revealed that the nanocellulose dispersion consists of individual nanocellulose whiskers of about 200 nm in length and 10-30 nm in width. This study showed that cellulose nanocrystals (CNC) will be appropriate templates for surface nanostructures particularly in applications aimed at incorporating bio-materials in materials fabrication.

The adsorption behaviour of starch on silica surface, which is mimic active sites existing on the surface of kaolinite, was investigated by a combination of spectrophotometry and turbidity techniques. It was demonstrated that the conformational behaviour of starch chain in aqueous solution is temperature and pH sensitive. Starch solution showed a rapid in­crease in turbidity, with decreasing temperature. This suggested that collapse is occurring causing the biopolymer chains to aggregate. The decrease in turbidity indicated that an open coil starch was formed at higher temperature. The starch with negatively charged alkoxides (R-O^-), due to the deprotonating of hydroxyl groups at mild basic pH values, showed a larger decrease in turbidity than the starch at low pH values, which indicates that chain aggregation is favored by a neutral starch chain and that the formation of an expanded shape is fa­vored by charged starch macromolecules. The point of zero charge results suggested that electrostatic interactions are mainly responsible for the adsorption of starch on SiO₂ suspension molecules. The UV-absorption spectra of anthracene labelled-starch proposed that the adsorption density of starch on silica is pH dependent. Starch adsorption on silica is extensively increased by decreasing pH to 7, as the electrostatic attraction between the R-C-OH₂⁺ groups in starch and the negatively charged silica (-Si-O^-) was enhanced. The flocculation of silica suspensions by starch chains depends on the adsorption behaviour of starch on the silica particles. The bridging flocculation of silica particles by starch is rather weak at pH 11, since starch shows extremely low affinity towards silica. When starch shows high affinity towards silica at pH 9 and 7, it starts to play a significant role in the flocculation of silica particles.