LECTURE2ERT 207

ANALYTICAL CHEMISTRY

QUANTITATIVE ANALYSIS & BASIC TOOLS

MISS NOORULNAJWA DIYANA YAACOB

School of Bioprocess Engineering

University Malaysia Perlis

02600, Kangar

Perlis

email: noorulnajwa@unimap.edu.my

6 January 2011

Several steps and operations whichdepend on

•the particular problem • your expertise • the apparatus or equipment

available. The analyst should be involved in

every step.

STEPS IN QUANTITATIVE ANALYSIS

1. Defining the problem Before we begin defining the

problem for an analysis procedure, we must have some information:

1)Who is the client (EPA, engineers)2)The purpose of analysis3)What type of sample to be analyzed

Once the problem is defined, next question:

1) How sample is to be obtained2) How much is needed3) What separation may be required to

eliminate interference

2. Select the method Accuracy/precision needed Economic factor Speed Complexity of the sample and the

number of component in the sample

3. Obtaining a representive Sample

The material to be analyzed- solids, liquids and gases

Homogeneous or heterogeneous in composition

Usually , in analysis, a simple “grab sample” will taken at random.

If the sample is large, the gross sampling is needed

The gross sample must be reduced in sized to obtain laboratory sample

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil

1kg

Soil sample for laboratory testSoil sample for laboratory test

50gram50gram

50gram50gram 50gram50gram

50gram50gram

GROSS SAMPLING

Some precautions should be taken during handling and storing samples to prevent or minimize contamination, loss, decomposition or matrix change

We must prevent contamination or alteration of the sample by

1)Light2)Atmosphere3)Container

4.Prepare the sample for analysis

Step1: Measure the amount being analyzed…Replicate samples are taken for analysis (WHY??)

1)to obtain statistical data on the precision of the analysis

2)to provide more reliable results

Step2: Sample pretreatmentExample:The organic materials sample are

analyzed for inorganic constituentsThe organic constituent may be

destroyed by dry ashingHOW??

The organic materials is slowly combusted in a furnace at 400-700 degrees

Organic material escape out, leaving behind an inorganic residue which is soluble in dilute acid

Aim of unwanted constituent that make up the whole sample

Step3: Optimizing sample condition Aim of step 3 is to prepare sample for

the next stage of analysis (the separation or measurement step)

The solution condition is optimized..HOW???

For example, the pH may have to adjusted or reagent is added to mask interference from other constituent

The analyte may have to be reacted with a reagent to convert it to a form suitable for measurement or separation

5.Perform Any Necessary Chemical Separation

Why conduct chemical separation?1)To eliminate interference2)To provide suitable selectivity in the

measurement3)To preconcentrate the analyte for

more sensitive or accurate measurement

6. Perform the Measurement Methods of carrying out the

measurements:1)Gravimetric analysis2)Volumetric analysis3)Instrumental analysis

7. Calculate the results and Report

Calibration and measurement • y = mx + b • y – measured signal • x – concentration Calculations • Calculate x from value of y for

analyte Statistics

Basic tools in Analytical Chemistry

Modern balances are electronic. They still compare one mass against another since they are calibrated with a known mass. Common balances are sensitive to 0.1 mg.

Modern balances are electronic. They still compare one mass against another since they are calibrated with a known mass. Common balances are sensitive to 0.1 mg.

Fig. 2.1. Electronic analytical balance.

Fig. 2.2 Volumetric flask.

Volumetric flasks are calibrated to contain an accurate volume. See the inside back cover of the text for tolerances of Class A volumetric glassware.

Volumetric flasks are calibrated to contain an accurate volume. See the inside back cover of the text for tolerances of Class A volumetric glassware.

Erlemenyer flask.

Fig. 2.3. Transfer or volumetric pipettes.

Volumetric pipettes accurately deliver a fixed volume. Volumetric pipettes accurately deliver a fixed volume.

Fig. 2.4. Measuring pipets.

Measuring pipets are straight-bore pipets marked at different volumes.

They are less accurate than volumetric pipets.

Measuring pipets are straight-bore pipets marked at different volumes.

They are less accurate than volumetric pipets.

Fig. 2.5. Hamilton microliter syringe.

Syringe precisely deliver microliter volumes.

They are commonly used to introduce samples into a gas chromatograph.

Syringe precisely deliver microliter volumes.

They are commonly used to introduce samples into a gas chromatograph.

Fig. 2.6 Single-channel and multichannel digital displacement pipets and microwell plates.

These syringe pipets can reproducibly deliver a selected volume.

They come in fixed and variable volumes. The plastic tips are disposable.

These syringe pipets can reproducibly deliver a selected volume.

They come in fixed and variable volumes. The plastic tips are disposable.

Fig. 2.7. Measuring cylinder.

Fig. 2.8. Wash botltles: (a) polyethylene, squeeze type; (b) glass, blow type.

Use these for quantitative transfer of precipitates and solutions,

and for washing precipitates.

Use these for quantitative transfer of precipitates and solutions,

and for washing precipitates.

Next topic: Basic statistics

Thank you

QUIZ...

1.What is quantitative analysis 2. State the phases of carrying out

tests using instrumentation for quantitative analysis in the right order