Analytical Chemistry

Introduction

Chemistry is a branch of science.

There are different branches to Chemistry:• Organic Chemistry• Inorganic Chemistry• Physical Chemistry• Analytical Chemistry

Chemical Analysis: is the determination of the quality and quantity of the substance.

Analytical Chemistry: is concerned with the chemical characterization of matter, both qualitative and quantitative.

Science

Organic

Inorganic

Physical

Analytical

Chemistry

Analytical Chemistry and Other Fields

Analytical chemistry plays an important role in nearly all aspects of chemistry.There are many fields that depend on analytical chemistry. For ex.,

• Medicine; analytical chemistry is the basis for clinical laboratory tests which help physicians diagnose disease.

• Industry; analytical chemistry provides the means of testing raw material. For ex., fuels and clothes.

• Environmental quality; the air in the cities must be analyzed for carbon monoxide.

• The nutritional value of food is determined by chemical analysis for major components such as protein and carbohydrates.

Comparing Between Qualitative Analysis and Quantitative Analysis

Qualitative Analysis Deals with the identification of elements, ions and compounds in a sample (we

may be interested in whether only a given substance is present). Ex.

1. Elemental Analysis

2. Identification of sample structure to be analyzed

Quantitative Analysis Deals with the determination of how much of one or more constituent is

present. There are two kinds of quantitative analysis:

1.Chemical Analysis

y + x = p

2. Instrumental Analysis

1. Define the problem2. Obtain a representive sample3. Prepare the sample for analysis4. Select a method

Analysis Steps

Step 1: Define the Problem

The analyst should have the right information about the sample.

For example: size, type.

Step 2: Obtain a Representive Sample

1. A chemical analysis is usually performed on only a small portion of the materiel to be characterized.

2. The material to be characterized can be:

* In the case of biological fluids, the condition which the collected sample must undergo are very important. For ex., the patient should fast for a number of hours before a blood test.

* Blood samples may be analyzed as whole blood or separated to yield plasma and serum. Serum: is the fluid separated from the clotted blood.Plasma: is the fluid separated from the unclotted blood.The difference is that plasma contains fibrinogen.

3. Handling and storing samples: Certain precautions must be taken to prevent alternation or contamination of the sample. For ex., storing the sample in the proper light, temperature and container.

* The stability of samples must be considered. For ex., preservations added to the blood must not interfere with the sample.

a. Homogeneousb. Heterogeneous Two quarters

1. Sample measurement:

- Measure the size of the sample to be analyzed. For ex., volume and weight of sample. It is important that a level of accuracy and precision is required.

- Solid samples are often analyzed on a dry basis and must be dried in an oven (110 – ْ 120 ْ) for 1-2 hours.

- To measure the sample we weigh the crucible containing the sample after weighing the crucible alone. Then we subtract the second from the first.

2. Dissolving the sample:

- Solid samples must be dissolved.

- Inorganic materials can be dissolved in various acids or in water.

- Organic materials must be dissolved in organic solvent.

3. Fusing the sample: - The sample must be fused with a compound to

obtain a mixture.- Basic materials are fused with organic materials.

Ex., perosolphate potassium. And vice versa.- Organic materials that are to be analyzed for

inorganic constituents may be destroyed or separated by:

- a. Dry ashing: (oven)- b. Wet ashing: (heating with oxidizing acids.

Ex., mixture of nitric and surface acids.

4. Chemical separation/ Masking of interference:- In this step it is required to separate chemicals by

selective methods or specific methods.- Selective methods can occur with other

substances but exhibits a degree of preference for the substance of interest.

- Specific methods can occur only with the substance of interest.

- Chemical separations - Electro deposition- Chromatographic methods- Solvent extraction

Step 3: Prepare the Sample for Analysis

After separating the interferences from the substance meaning to be estimated, the analysis method that has been selected may be applied in which it is the most suitable for answering the specific request.

1. Speed:

A child who has been poisoned by a substance cannot wait long enough until the nature of the poison has been detected. That is why a high level of speed must be required in a method.

2. Accuracy and precision needed:

Finding the amount of sugar in a soda drink does not require a method of high accuracy and precision. Unlike analyzing toxic constituents such as lead and mercury that require accurate and precise methods.

Accuracy: is the degree of agreement between a measured value and a true value.

Precision: is the degree of agreement between replicate measurement of the same quantity and does not necessarily imply accuracy.

3. Tools/ Instruments available.

Step 4: Select a Method