FOR ANACHEM FINALS

Analytical Chemistry

A branch of chemistry that deals with the separation, identification and determination of analytes (components) in a sample

AREAS OF ANALYTICAL CHEMISTRY

• Industrial Quality Control

• Bioanalytical chemistry and analysis

• Environmental analysis

• Forensic analysis

• Clinical analysis

• Pharmaceutical analysis

Industrial Quality Control

requirements of companies for product quality

Bioanalytical chemistry and analysis

detection or analysis of biological components (ex: proteins, DNA, RNA, Carbohydrates)

Environmental Analysis

monitoring of pollutants, soil and water analysis, pesticides

Forensic Analysis

criminology, DNA finger printing, finger-print detection, blood analysis (crime detection and court testimonies)

Clinical analysis

analysis of blood, urine, feces, cellular fluids

Pharmaceutical Analysis

analysis of physical properties, toxicity, metabolites, quality control

Qualitative Analysis

an analysis to identify the materials present in a sample

Quantitative Analysis

An analysis to determine the amount of a material present in a sample

Sample

representative of the population or gross sample

Analyte

the substance to be identified, detected, or separated in some manner

Matrix

all other constituents except analyte

Interference

a specific component identified to be causing an effect

Complete Analysis under Quanti

amount of each constituent of the sample is determined

Partial Analysis under Quanti

amount of a certain selected constituent in a sample is determined

Major constituents

Greater than 1%

Minor Constituents

from 0.1 to 1%

Trace Constituents

less than 0.1%

Ultra trace

a few ppm or less

CLASSIFICATION OF ANALYTICAL METHODS

• Classical Methods

• Instrumental Methods

Two types of Chemical Analysis

• Quanti

• Quali

Methods under Classical Methods

• Gravimetric

• Volumetric

Gravimetric method

measure mass of the analyte or a compound chemically related to the analyte

Volumetric Methods

measure volume of a solution containing sufficient reagent to react with the analyte

Methods under Instrumental Methods

• Separation/Chromatograhic Methods

• Spectroscopic Methods

• Electroanalytical Methods

Separation or Chromatographic Methods

measure peak areas of the separated components of a sample

Spectroscopic Methods

measure the interaction between the analyte and electromagnetic radiation or the production of radiation by an analyte

Electroanalytical Methods

measure an electrical property (potential, current) which is chemically related to amount of analyte

Separation of analytes under classical

• extraction

• filtration

• distillation

• precipitation

  (simple physical procedures)

Separation of analytes under instrumental

• chromatography

• electrophoresis

• spectroscopic separation

quantitative analysis under classical

• titration

• gravimetric analysis

qualitative analysis under classical

• boiling and melting point

• color

• odor

• density

• reactivity

• refractive index

quantitative analysis under instrumental

• uv-vis spectrometry

• AAS

• AES

• conductivity

qualitative analysis under instrumental

• x-ray spectrometry

• IR spectrometry

• Mass spectrometry

• Nuclear Magnetic Resonance

Concentration

the amount of solute in a known amount of solution

Expressions of Concentration

• Molarity (M)

• Normality (N)

• PPT

• PPM

• PPB

• % Concentration

Normality

number of g eq of solute in grams over liters of solution

7 Steps of Analytical Process

1. Problem Definition

2. Literature review/search

3. Method Selection

4. Sampling

5. Sample Preparation

6. Analysis

7. Calculation and Reporting

Problem Definition

Step in analytical process that requires for the translation of general questions into specific questions - to be answered by chemical measurement

In house method

adopted from standard method with minor changes

Cookbook

analysis run by the instrument purchased

In-situ testing

tests conducted on or in the soil at the site

Sampling

the process to obtain a small representative and homogenous sample

Representative

content of analytical sample reflects content of bulk sample

Homogenous

content is the same throughout the whole sample

Sampling

the most critical step because it can limit the accuracy of measurements

Analytical Train

Mistakes in any step will affect validity of final results

Sampling

requires storage and preservation steps

Grab Sample

a portion of sample removed from the population

Composite Sample (Spatial or Temporal)

several grab samples combined to form a single sample

Heterogenous parent Samples

several samples have to be taken

Preservation to help minimize physical changes

• adsorption

• diffusion

• volatilisation

Preservation to help minimize chemical changes

• oxidation

• microbiological degradation

Sample Preparation

s step in chemical analysis where the sample is brought into the correct size or form for analysis

Replicates

samples analyzed in the same way, same size, at the same time

TRUE

Inorganic analyte and inorganic matrix remains after dissolution

Simple dissolution

solid is dissolved in solvent without chemical change

Dry Ashing

oxidize by slow heating in oxygen at very high temp

Wet Digestion (aka Acid Treatment)

heat sample with mineral acids in open/closed container or in a microwave digester

Fusion technique

heat with flux or acid until molten state

External Standard Calibration Method

the standard and the sample are analyzed separately under identical conditions. The blank must be subtracted from the readings obtained.

feasible if the standards and the sample’s MATRIX HAS NO EFFECT on the value of the slope of the calibration curve

Calculating and Reporting

In which step do you determine the concentration of the analyte in the analytical sample solution

use results to calculate the amount of analyte in the original bulk sample

Spectroscopy

the study of the properties of matter through its interaction with different frequency components of the electromagnetic radiation (EMR)

Optical properties

explained by describing light as waves which correspond to frequency and wavelength

v (s^-1 or Hz)

number of cycles passing a fixed point per unit time - frequency

equal to c/lambda

lambda (cm)

distance of one cycle - wavelength

c

velocity of light = 3 × 10^10 cm Hz

Interactions between radiation and matter

described by treating light as particles

Photons

have no mass yet carry a specific amount of energy

TRUE

EMR consists of quantum of energy (discrete packets of energy @ energy of photons)

Energy of a photon (E)

equals hv or hc/lambda

h

Planck’s constant = 6.62 × 10^-34 J.s

TRUE

The shorter lambda, the higher E

Interactions of Matter with EMR

• Absorption

• Emission

• Scattering

Absorption (to take up)

an excitation transition from a lower energy state to a higher state

Emission (to give off)

a relaxation transition from a higher energy state to a lower level

Scattering

redirection of light due to its interaction with matter

Molecular Spectroscopy

study of light interactions with molecules

Bonding electrons

enable molecules to absorb, emit, and scatter light

Atomic Spectroscopy

measurement of the wavelength or intensity of light that is emitted or absorbed by free atoms (absorbed by valence electrons)

Identity and Amount of Analyte

characteristics of wavelengths absorbed and emitted depends on?

Spectral Interferences

absorption or emission of other components of the matrix that occur at the same wavelength of use for analysis

Chemical Interferences

materials determined are not in the same chemical or suitable form

Instrumental Interferences

excess illumination due to imperfections in the instrument

Complement of Absorbed Light

what is transmitted?