Pharma Analysis

How will you ascertain purity of sample by DSC? Discuss its principle

Q.5. (b)How will you ascertain purity of sample by DSC? Discuss its principle.  
Ans.5. (b) Principle

In DSC the heat flow is measure and plotted against temperature of furnace or time to get a thermo gram. This is the basis of Differential Scanning Calorimetry (DSC). The curve obtained in DSC is between dH/dtinmJ s-1 ormcal s-1 as a function of time or temperature. A typical DSC curve is shown in Fig. 1.19. The deviation observed above the base (zero) line is called exothermic transition and below is called endothermic transition. The area under the peak is directly proportional to the heat evolved or absorbed by the reaction, and the height of the curve is directly proportional to the rate of reaction. Therefore Eq. 11.1 is equally valid for DSC scheme also. The only difference is the calibration factor K in case of DSC is independent of temperature. This is a major advantage of DSC over DTA.
Peak area (A) = ± _ H m K …(1.7)

Discuss factors affecting DTA results

Q.5. (a) Draw diagram of apparatus and give methodology of DTA. Discuss factors affecting DTA results.
Ans.5. (a) Differential Thermal Analysis

In differential thermal analysis (DTA), a sample and a thermally inert reference material differencebetween the sample and the reference is measured as a function of the temperature applied. Because, during transition, the sample may either absorb or evolve heat, the difference in the temperature between the sample and the standard is equivalent to the temperature of transition and can indicate if the transition is endothermic or exothermic. Usually, ΔT is plotted against the temperature, T, or as a function of time (t).
DTA data are probably the most accurate of all thermal techniques, because the thermocouple is insert     into the sample; however, only the temperature of a transition and not the amount of heat can be measured from a DTA curve, as the area under the peak is not proportional to the amount of energy transferred into or out of the sample.
Factors affecting the DTA curve

Elaborate factors affecting electrophoretic mobility

Q.4.(c) Elaborate factors affecting electrophoretic mobility.
Ans.4. (c) Electrophoretic Mobility
    
The migration rate ʋ of an ion (cm/s) in an electric field is equal to the product of the field strength E (V cm-1) and the electrophoretic mobility µe (cm2V-1s-1). That is,
ʋ = µeE
Electrophoretic mobility, µe = E/ʋ
The electrophoretic mobility is in turn proportional to the ionic charge on the analytic and inversely proportional to frictional retarding factors.
Factors affecting Electrophoretic Mobility:

Give difference stationary phases used in different modes of HPLC

Q.4.(a) Give difference stationary phases used in different modes of HPLC.
Ans.4. (a)Types of Stationary Phases used in HPLC:
Various stationary phases available for HPLC are  Polystyrene/Divinylbenzene- Based Resins   In ion chromatography, the support material is polystyrene/ divinylbenzene (PS/DVB) based resin that is relatively stable with respect to pH.

Differentiate between PMR and 13 CNMR

Q.3. (b) How will you simplify complicated splitting pattern in PMR? Differentiate between PMR and 13 CNMR.
Ans.3. (b)Introduction:

The complete analysis of a compound is frequently made difficult, when signals overlap and as a result, useful information is often buried due to complexity of the spectrum. In a spectrum several signals may overlap as is the case, e.g., of closely related methylene groups in a molecule. In such a situation an intense, broad and compulsory unresolved signal, termed the methylene envelope may appears between δ 1-2. Another cause of complexity is where a coupling constant is comparable with the chemical shift different between the coupled protons. For these problems following techniques may use to solve them.

How will you differentiate between first order and non-first order PMR spectra

Q.3.(a) How will you differentiate between first order and non-first order PMR spectra
Ans.3. (a)First order spectra:

For a spectrum to be first order, the frequency difference (∆v, in Hz) between any two coupled resonances must be significantly larger than the coupling constant that relates them. A first-order spectrum has ∆v/J >  -63.
First-order resonances have a number of helpful characteristic, some of which are related to the number individual coupling, n:

Explain frequency shift due to inductive and mesomeric effects in IR spectroscopy

Q.2. (b) Explain frequency shift due to inductive and mesomeric effects in IR spectroscopy
(b)Frequency shift due to inductive:
The inductive effects solely depends upon the ‘intrinsic’ tendency of a substituent to either release or withdraw electrons- by definition, its electronegativity acting either through the molecular chain or through space. This effect usually weakens steadily with increasing distance from the substituent

Pharma Analysis

Pharmaceutical Analysis

INTRODUCTION
Pharmaceutical analysis is a branch of practical chemistry that involves a series of process for identification, determination, quantification and purification of a substance, separation of the components of a solution or mixture, or determination of structure of chemical compounds.

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