Question

Briefly explain the following giving all relevant equations, where necessary. Your answer for the whole question should not be more than 2 pages. You may need to review the information in relevant textbooks and/or papers in the literature.

1. Sensitivity and Selectivity

Explain the following:

i) calibration sensitivity

ii) analytical sensitivity

iii) selectivity
iv) the difference(s) between sensitivity and selectivity

Answer 1

a,Calibration sensitivity:

Sensitivity can be termed as the ability to set apart even the small differences between the concentration of analytes present in the system.

The slope of the calibration curve is the calibration sensitivity. The slope at the concentration of interest will give the calibration sensitivity. Slope is mentioned in the image.

The selectivity coefficient k_B,A = m_B / m_A

b,Analytical sensitivity:

The ability of a test to statistically detect the concentration of analyte(with very low concentration) in a system by finding the concentration at which the mean response is beyond noise limits is called as analytical sensitivity.

Analytical sensitivity in weight percentage Delta C = C - C'

Where C' is the concentration to compare and C is the actual concentration in weight percentage.

c,Selectivity:

The extent to which a method can determine the concentration of a solute,without any interference from other compounds present in the system is called as selectivity.

The detectors ability to filter out the interfering signals is termed as selectivity.

The selectivity coefficient K_A,I = k_I / k_A

Where kI is the interference selectivity and k_A is analyte's selectivity.

d,Difference between sensitivity and selectivity:

Sensitivity is nothing but finding out the true signals even if in low concentration from the system.

Selectivity is nothing but finding out the false signals in the system caused due to the interference of compounds,eliminating them and then finding out the true signal from that.

The term selectivity is not the popular method used to determine the concentration of an analyte ina system in analytical chemistry because,it has the determination of many false signals and all the false signals should be filtered out. Hence sensitivity is more often used in the analytical chemistry.