1. Introduction to Analytical Chemistry
B.Sc.
Sneha S. Mule
Assistant Professor
Department of Chemistry,
S. M. Joshi College, Hadapsar

2. Introduction to Analytical Chemistry
Background
A.) ANALYTICAL CHEMISTRY: The Science of Chemical Measurements.
B.) ANALYTE: The compound or chemical species to be measured, separated or studied
C.) TYPES of ANALYTICAL METHODS:
1.) Classical Methods (Earliest Techniques)
a.) Separations: precipitation, extraction, distillation
b.) Qualitative: boiling points, melting points, refractive index, color,
odor, solubilities
c.) Quantitative: titrations, gravimetric analysis
2.) Instrumental Methods (~post-1930’s)
a.) separations: chromatography, electrophoresis, etc.
b.) Qualitative or Quantitative: spectroscopy, electrochemical methods,
mass spectrometry, NMR,
radiochemical methods, etc.

3. Two types of error: random or systematic
CHARACTERISTICS OF AN ANALYTICAL METHODS
Accuracy: The degree to which an experimental result approaches the true or accepted answer.
Ways to Describe Accuracy:
Error: An experimental measure of accuracy. The difference between the result obtained by a method and the true or accepted value.
Absolute Error = (X – m)
Relative Error (%) = 100(X – m)/m
where: X = The experimental result
m = The true result
All Methods, except counting, contain errors – don’t know “true” value
Two types of error: random or systematic

4. CHARACTERISTICS OF AN ANALYTICAL METHODS
Random Error: results in a scatter of results centered on the true value for repeated measurements on a single sample.
Systematic Error: results in all measurements exhibiting a definite difference from the true value
Systematic Error
Random Error
plot of the number of occurrences or population of each
measurement (Gaussian curve)

5. CHARACTERISTICS OF AN ANALYTICAL METHODS
Precision: The reproducibility of results. The degree to which an experimental result varies from one determination to the next.
Precision is related to random error and Accuracy is related to systematic error.
Illustrating the difference between “accuracy” and “precision”
Low accuracy, high precision
Low accuracy, low precision
High accuracy, low precision
High accuracy, high precision

6. CHARACTERISTICS OF AN ANALYTICAL METHODS
Ways to Describe Precision:
Range: the high to low values measured in a repeat series of experiments.
Standard Deviation: describes the distribution of the measured results about the mean or average value.
Absolute Standard Deviation (SD):
Relative Standard Deviation (RSD) or
Coefficient of Variation (CV):
where: n = total number of measurements
Xi = measurement made for the ith trial
= mean result for the data sample

7. CHARACTERISTICS OF AN ANALYTICAL METHODS
Response: The way in which the result or signal of a method varies with the amount of compound or property being measured.
Ways to Describe Response:
Calibration Curve: A plot of the result or signal vs. the known amount of a known compound or property (standard) being measured.

8. CHARACTERISTICS OF AN ANALYTICAL METHODS
Parameters used to Describe a Calibration Curve: S = mc + Sbl
S – measured signal
c – analyte concentration
Sbl – instrument signal for blank
Sensitivity: calibration sensitivity = slope (m) of calibration curve.
analytical sensitivity (g) = slope (m)/standard deviation (Ss)
ability to discriminate between small
differences in analyte concentration.
Slope and reproducibility of the
calibration curve.
Method A
Method B

9. Limits of Detection (cm ): (minimum analyte signal (Sm) - mean blank signal( ))/slope(m)
minimum/maximum concentration or mass of analyte that can be detected at a known confidence level.
Signal-to-noise Ratio (S/N):
Noise: random variation in signal or background
Signal: net response recorded by a method for a sample
(Note: a value of S/N = 2 or better is considered to be the minimum ratio needed for the reliable detection of a true signal from a sample.)
Estimate S/N:
Multiple determination of blank samples.
Estimation of best-fit to calibration curves

10. THANK YOU