A d.c. polarographic method was developed for the determination of nitrofurazone in pharmaceutical formulations using individually four different buffer systems, namely acetate ( pH 3.60-5.601, Mcllvaine (pH 2.20-8-00), borate (pH 7.80-10.00) and Britton -Robinson (pH 2.00-12.00). The substance was extracted from the dosage forms with 40% methanol, an appropriate buffer of selected pH was added to an aliquot and the solution then polarographed a t a dropping-mercury electrode versus S.C.E. The two-step reduction waves observed were found to be irreversible and diffusion controlled. The standard additions technique provided results as satisfactory as those obtained with the use of a calibration graph.

A simple, rapid, d.c. polarographic method has been developed for the determination of nitrazepam in its pharmaceutical formulations. Ethanol was employed as the solvent for extracting the drug from the formulations and five different buffer systems, namely hydrochloride (pH 1.0-2-21, Mcllvaine (pH 2.2-8.0), acetate (pH 36-56), borate (pH 7.8-10.0) and Britton -Robinson (pH 2.0-12.0), were used individually as the supporting electrolyte. Nitrazepam is reduced in two-step, irreversible, diffusion-controlled and pHdependent waves. Results obtained by the proposed method are in excellent agreement with those given in the British Pharmacopoeia. Commonly used tablet excipients were found not to interfere. A comparison was also made with different batches of nitrazepam tablets and capsules by the proposed method.

No abstract

Engineering efforts need to be organized as per the rock mechanic conditions of the site for efficient underground extraction of a thick coal seam. Geo-mining conditions of Indian coalfields have favoured development of thick coal seams on Bord and Pillar (B&P) method, where single lift depillaring of total thickness (SLDTT) is vital for their final extraction. Competency of heightened pillar is an important factor for uncontrolled roof-pillar interaction during caving of the hard and massive overlying strata. An increase in extraction height by underwinning of roof coal band of the thick coal seam during retreat, developed along its floor horizon, is found to be the main reason for the strength deterioration. Conducted field studies also showed that the presence of competent overlying strata caused caving after a large overhang inside the goaf varying from 6000 m2 to 12500 m2. An attempt was made to control the roof caving by a proportional increase in width of the heightened pillars and it worked well but caused the issue of resource conservation. However, another field study with SLDTT working below laminated and weak overlying strata experienced a smooth strata control condition. This fortifies the idea of strength reduction of the competent overlying strata by fracturing for a controlled strata behaviour. This paper presents the result of the field investigations to demonstrate the role of strength reduction of overlying strata for underground extraction of total thickness of a thick coal seam in single lift.

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation.