The Pharmacopeia and analysis. Introduction to spectroscopy

Question 1

qualitative analysis

Answer 1

primarily to identify the substance

Question 2

quantitative analysis

Answer 2

to accurately determine the amount of a substance

Is based on the establishment of a linear relationship between the amount of a substance and some measurable physical, chemical, or biological property of that substance.

Question 3

Volumetric Analysis (Titrations)

Answer 3

Is a quantitative method.

Is used for about 80% of the substances in the BP.

Acid/Base & Redox titrations appear within the BP

Question 4

Spectrophotometric Methods

Answer 4

Utilise the interaction of substances with electromagnetic radiation.

Are mainly applicable to pure substances.

Infrared Spectroscopy (IR)
Ultraviolet Spectroscopy (UV)

Question 5

Infrared Spectroscopy

Answer 5

Is a qualitative method (never quantitative).

Provides a “Fingerprint”.

Is used in many monographs as an identification technique.

Question 6

Ultraviolet / Visible Spectroscopy

Answer 6

Provides both quantitative and qualitative information.

Is widely used as a quantitative method.

Question 7

Chromatographic Methods

Answer 7

Separate mixtures of substances by virtue of their differing affinities for a stationary phase and a mobile phase.

Thin Layer Chromatography (TLC)
High Pressure Liquid Chromatography (HPLC)
Gas Liquid Chromatography (GLC)

Question 8

Thin Layer Chromatography

Answer 8

Is mainly qualitative or semi-quantitative.

Is used by the BP to monitor impurities.

Is used in a semi-quantitative manner in limit tests for impurities.

Question 9

High Performance Liquid Chromatography (HPLC)

Answer 9

Is used for both qualitative and quantitative analysis.

Is most suitable for substances soluble in mixtures of water and polar organic solvents.

Question 10

Gas Liquid Chromatography (GLC)

Answer 10

Is qualitative and quantitative.

Is suitable for relatively volatile and heat stable organic compounds.

Question 11

Validation of Quantitative Analyses

Answer 11

Selectivity
Linearity of Response
Accuracy
Precision
Limit of Detection
Limit of Determination

Question 12

Selectivity

Answer 12

The analyte must be detected and quantified without interference from other substances that might be present.

Tested by carrying out the analysis in the presence of expected contaminants.

Question 13

Linearity of Response

Answer 13

Must be proved using pure standards, generally five concentration levels covering the concentration range required.

These data can be plotted as a Calibration Curve.

Question 14

Accuracy can be affected by

Answer 14

Other compounds in the mixture.

Necessary manipulation of the sample during analysis.

The complexity of the overall analysis process.

Repeating the calibration series in the presence of all the other components in the mixture and following the complete analysis procedure and then:

Plotting a curve and calculating Linear Regression statistics as for Linearity.

Question 15

Recovery

Answer 15

A rough measure of accuracy is provided by calculating the recovery from:

% Recovery = Sample Slope x 100
			  Standard Slope

Question 16

Precision - Repeatability

Answer 16

Multiple analyses of the same material by the same person using the same equipment over a short period of time.

Calculate:
the Mean.
the Standard Deviation.
The Relative Standard Deviation = SD x 100 Mean

Question 17

Precision - Reproducibility

Answer 17

Multiple analyses of different samples by different persons using other equipment in other laboratories over a longer period of time.

A standardised form of statistical analysis is carried out to determine Mean, Standard Deviation and Relative Standard Deviation

Question 18

Limit of Detection

Answer 18

Is a measure of the absolute lower limit of analyte that the method can detect.

Generally, the analyte response minus the blank response should be more than 3 x the Standard Deviation of the blank response.