Search

A new simple, accurate, precise, highly sensitive and reproducible difference spectrophotometric method for the determination of leflunomide in bulk and pharmaceutical dosage form is described. The difference spectroscopic method is based on the principle that leflunomide exhibit two different forms; in acidic and basic medium which differs in their absorption spectra. The difference spectra were obtained by reading the absorbance of leflunomide in 0.1 N HCl in the reference cell and the absorbance of leflunomide in 0.1 N NaOH in the sample cell and vice versa; in the difference spectrum maxima and minima were seen at 293.5 and 261.5 nm, respectively. The amplitude values were calculated, which was plotted against concentration. The method is found to be linear in the concentration range of 2-12 μg/ml. The percentage recovery was found to be between the ranges from 98.92 to 99.08%. The proposed method was statistically validated and successfully applied for analysis of tablet dosage forms. [ABSTRACT FROM AUTHOR]

Waves and currents recorded off Chavara, southwest coast of India, over a period of 2 years are used to understand the wave-current regime of this monsoon dominated coast. The waves during monsoon are characterised by higher heights, shorter periods, and are confined to westerly directions. The wave characteristics indicate nearby generation. The premonsoon and postmonsoon waves are characterised by lower heights and higher periods with the direction being more southerly. Waves arrive from a wider range of generating areas during the fair weather periods, particularly during the premonsoon months. The wave heights exhibit yearly variations, but the periods and directions remain relatively constant. Like the waves, the currents also show seasonal changes with stronger currents during monsoon and weaker currents during fair weather. The alongshore components of the currents are mostly much stronger than the cross-shore flows and the pattern is mostly diurnal although a semidiurnal signal is also readily apparent, the latter associated with tidal currents. The diurnal activity is mostly wind-induced. In the monsoon season, the dominant direction is southerly to southwesterly, whereas during the premonsoon and postmonsoon it varies between northwest and southeast. Notable deviations to the generally understood pattern of southerly currents during monsoon and northerly currents during fair weather are observed. This could be attributed to the reported occurrence of a cyclonic eddy during monsoon and anticyclonic eddy during fair weather in the Lakshadweep Sea. [ABSTRACT FROM AUTHOR]

The beaches of Chavara and Manavalakuruchi of the southwest coast of India have rich heavy mineral concentrations with distinctive spatial and temporal distributions. Both locations exhibit high concentrations of heavy minerals on the northern sides of the headlands, with practically no concentration on the southern sides. Cross-shore, the sediments become less rich in the heavy minerals offshore. During the rough monsoon when the winds are onshore the concentration of heavy minerals along the mid-tide line of the beaches is considerably higher than during the calm non-monsoon when swell prevails. The concentrations of heavy minerals alongshore were highest in zones where the beach with relict sediments of high mineral content is eroding. We find that the patterns observed in the heavy minerals along the Chavara coast can be explained by a single hypothesis dependent on the presence of a source and the winnowing of the more easily entrained low-density fractions. The pattern appears to be slightly different for Manavalakuruchi coast where the zone of hundred percent enrichment is adjacent to the river mouth, indicating an additional source of river input. Analysis of wave and current data showed the dominant role of waves over coastal currents in the transport of these sediments and the wave-induced thresholds for initiation of motion indicated that the heavy component is less easily moved than the white sand (quartz) constituent. We suggest that the patterns can be explained by winnowing of the white sands from the eroded beach sediments during the stormy monsoon leaving higher enrichment at the beach. In the swell period of the post-monsoon, the erosion ceases as the asymmetric swells re-establish the beach, bringing proportionally more of the more-easily entrained white sediment shorewards, thereby explaining the reduced enrichment at this time. The cross-shore reduction in heavy minerals may be simply explained as an inverse relationship to distance from the beach source. The longshore distribution is a response to the presence of the source of black sands on the northern sides of the headlands. The headlands may simply act to isolate the source, thereby explaining the tendency for high concentrations on one side only. [ABSTRACT FROM AUTHOR]