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M. S. Ansari ¹, S. V. G. Ravindranath ², M. S. Bhatia ³, R. K. Patidar ⁴, C.P. Navathe ⁵

Affiliations
1 Laser Electronics Support Division Raja Ramanna Centre for Advanced Technology, Indore 452013
2 A&MPD, BARC
3 L&PTD, BARC, Mumbai 400085, IN
4 LPD, RRCAT, Indore-13
5 Laser Electronics Support Division Raja Ramanna Centre for Advanced Technology, Indore 452013, IN

Abstract

This paper reports the wavelet transform based time-frequency-intensity analysis of radiated electromagnetic noise generated by a flash lamp pumped terawatt class of high power pulsed laser. High power pulsed solid state lasers are widely used for research and industrial applications. Main electrical components of these lasers are flash lamp power supplies, electro-optic switches, timing and synchronization circuits, and control system. These sub-systems operate at different instants of time during the laser operation cycle. Range of the time delays between switching of various blocks in the system vary from 100 ns to hundreds of microseconds. The electromagnetic noise generated by the laser is pulsed type single shot event, which is measured in time domain. The conventional technique of Fourier transform generate frequency spectrum of the electromagnetic interference (EMI), however, it loses the time information and does not reveal the noise contributions by each of the sources and subsystem localized in time. In this work, wavelet transformations are applied on the measured signals to estimate frequency content of the noise contribution by each source and to generate the time-frequencyinformation. This technique helps in better identification and characterization of the electromagnetic noise sources in a high power laser chain and to achieve the growing demands for electromagnetic compatibility (EMC).

Keywords

Wavelet Transform, Flash Lamp Pumped Solid State Laser, Electromagnetic Interference (EMI)

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Neela M. Bhatia , M. S. Bhatia , P. B. Choudhari , K. B. Ingale

Abstract

Two new simple, sensitive, rapid, accurate and reproducible methods (UV-spectrophotometric and ion pair chromatography) have been developed for simultaneous estimation of valsartan (VAL) and hydrochlrothiazide (HCTZ) from their tablet dosage form. The first method involves multiwavelength spectrophotometric method (Method 1) in which interference of HCTZ at 245nm (wavelength for estimation of VAL) was removed by recording absorbance difference at 245nm and 301 nm whereas HCTZ was estimated directly from its absorbance at 316 nm at which VAL shows no absorbance. Linearity of the response was demonstrated by VAL in the concentration range of 5-45 μg/ml with a square correlation coefficient (r²) of 0.9998. Linearity of the response was demonstrated by HCTZ in the concentration range of 2-18 μg/ml with a square correlation coefficient (r²) of 0.9994. The second method utilizes ion pair chromatography (Method 2) on a HIQ sil ODS column (250 mm* 4.6 mm i.d.) using methanol: 0.0025 M orthophosphoric acid: (70:30 by volume) having pH 4.6: 0.1% hexane sulphonic acid as mobile phase with UV detection at 259nm over concentration range for VAL is 240-0 μg/ml, and for HCTZ is 75-0μg/ml. Losartan potassium was used as the internal standard. The suggested procedures were checked using laboratory prepared mixtures and were applied successfully for the analysis of their tablet dosage form. The results of analysis were statistically analysed. Both the methods were validated as per ICH Q2B guidelines.

Keywords

Valsartan, Hydrochlrothiazide, Losartan Potassium Ultraviolet Spectrophotometry, Multiwavelength Method, RP - HPLC, Validation.

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S. D. Jadhav ¹, M. S. Bhatia ², S. L. Thamake ², S. A. Pishawikar ²

Affiliations
1 Department of Pharmaceutical Chemistry, Tatyasaheb Kore College of Pharmacy, Warananagar-416113 (M.S.), IN
2 Department of Pharmaceutical Chemistry, Bharati Vidyapeeth College of Pharmacy, Morewadi, Kolhapur-416013 (M.S.), IN

Abstract

Lamivudine (LMV), Zidovudine (ZDV) and Nevirapine (NVR) are used in combination for treatment of HIV I. The present work deals with method development for simultaneous estimation of these drugs in tablet dosage form by UV spectrophotometry. A new simple, accurate and sensitive method for simultaneous estimation of lamivudine, zidovudine and nevirapine from tablet formulation has been developed. The method employs combination of zero order and first order derivative spectroscopy. Estimation of nevirapine was done in zero order derivative mode at 310 nm where zidovudine and lamivudine do not show any interference. Estimation of zidovudine was done in first order derivative mode at 270 nm where lamivudine and nevirapine shows zero crossing points. Estimation of lamivudine is done in zero order derivative mode at 271 nm by correcting the absorbance interferences due to zidovudine and nevirapine. Absorbance interferences of zidovudine and nevirapine calculated from their absorptivities. The results of analysis validated statistically and recovery studies showed satisfactory results. Thus the method is accurate and reproducible and can be employed for routine analysis of these drugs from tablet dosage forms.

Keywords

Lamivudine, Zidovudine, Nevirapine, Absorbance Interferences.

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