01 - INSTRUMENTAL METHODS OF ANALYSIS

• Classical / Wet-Chemical Method

• Instrumental Method

Two types of analytical method

Classical method

measurement depends on the chemical properties of the sample

classical method

reagent is made to react completely with the analyte

chemical stoichiometry

relationship between the measured signal and the analyte concentration is determined by ?

• precipitation

• extraction

• distillation

classical method: separation

• color

• solubility

• MP and BP

• odor

• optical activity

• refractive index

classical method: qualitative

• gravimetric

• volumetric

classical method: quantitative

classical method

• used to certify analytical standards

• generally cheaper

• more accurate and precise

• more robust and less susceptible to environmental fluctuations

• more suitable for analysis of major constituents

instrumental method

measurement of physical and chemical properties of the analyte

• chromatography

• electrophoretic technique

instrumental: separation

• conductivity

• electrode

• potential light absorption or emission

• mass-to-charge ratio

• fluorescence

instrumental: quantitative

instrumental method

• ability to perform trace analysis

• most are multi-channel techniques

• shorter analysis time

• automation

• more samples may be analyzed quickly

• less skill and training required

(SECM)

• Spectrometric method

• Electrochemical method

• Chromatographic method

• Miscellaneous method

4 types of instrumental method

(EASRDR)

• emission

• absorption

• scattering

• refraction

• diffraction

• rotation

type of spectrometric methods

emission

• emission spectroscopy

• fluorescence

• phosphorescence & luminescence

absorption

• spectrophotometry and photometry

• photoacoustic spectroscopy

• nuclear magnetic resonance & electron spin resonance spectroscopy

scattering

• turbidimetry

• nephelometry

• raman spectroscopy

refraction

• refractometry

• interferometry

diffraction

• xray

• electron diffraction methods

rotation

• polarimetry

• optical rotary dispersion

• circular dichroism

• GC (Gas chromatography)

• HPLC (High Performance Liquid Chromatography)

2 types of chromatographic methods

(CCPP)

• Conductometry

• Coulometry

• Polarography / Amperometry

• Potentiometry

4 types of electrochemical methods

resistance

conductometry

charge

coulometry

current

polarography

potential

potentiometry

• mass-to-charge ratio

• thermal characteristics

• radioactivity

3 types of miscellaneous methods

mass-to-charge ratio

mass spectrometry

• thermal gravimetry & titrimetry

• differential scanning calorimetry

• different thermal analyses

• thermal conductometric methods

thermal characteristics

activation and isotope dilution methods

radioactivity

analytical instruments

converts information about the physical or chemical characteristics of the analyte to information that can be manipulated and interpreted by man

analytical instruments

it is a communication device between the system under study and investigator

signal generator

• consists of the chemical system interacting with the stimulus from the energy source

• produces analytical signal reflecting the presence & usually the concentration of the analyte

transducer or detector

• transforms the analytical signal produce by the signal generator into electrical signal

signal processor

modifies and cleans up the electrical signal to make it more convenient to interpret

• amplification

• attenuation

• filtration

3 purpose of signal processor

analytical signal

energy source + chemical system

read out device

converts electrical signal to a form of usable to the analyst

calibration

determines the relationship between the analytical response and the analyte concentration

use of chemical standards

how is calibration determined?

(CESI)

Comparison with standards

External standard

Standard addition method

Internal standard

4 types of calibration

• direct comparison

• titration

2 types of comparison with standards

direct comparison

property of analyte is compared with standards

conc. of analyte = conc. of std after dilution

titration

most accurate analytical procedure

analyte reacts with the standardize reagent

used to calibrate instruments and procedures when there are no interference effect from matrix

standard addition method

useful for analyzing complex samples in which the likelihood of matrix effects is substantial adding one or more increments of std soln

spiking

adding of std in analyte

internal standard

substance that is added in constant amount to all samples, blanks, and calibration std in an analysis

• signal

• noise

two components of analytical measurement

signal

carries information about the analyte

noise

extraneous information that is unwanted and degrades the accuracy and precision of an analysis

chemical noise and instrumental noise

two types of noise

chemical noise

• uncontrollable variables that affect the chemistry system

instrumental noise

• associated with each component of an instrument

signal-to-noise ratio

equation that indicates the magnitude of an experimental effect above the effect of experimental error due to chance fluctuations

international council for harmonisation (ICH)

an international non-profit organization that aims to develop guidelines via a process of scientific consensus w/ regulatory and industry experts working together

out-of-control process

a process in which variations among the observed sampling result cannot be attributed to a constant system of chance

out-of-specification result

a result that falls outside established acceptance criteria

out-of-trend result

a time-dependent result which falls outside a prediction interval or fails a statistical process control

standard

outputs of process are compared and declared acceptable / unacceptable

specification

established the set of criteria to which a meterial should conform to be considered acceptable

system suitability test

used to verify that the test system will perform in accordance with the criteria set forth