LECTURE2ERT 207
ANALYTICAL CHEMISTRY
QUANTITATIVE ANALYSIS & BASIC TOOLS
MISS NOORULNAJWA DIYANA YAACOB
School of Bioprocess Engineering
University Malaysia Perlis
02600, Kangar
Perlis
email: [email protected]
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