QUANTITATIVE ANALYSIS &
MISS NOORULNAJWA DIYANA YAACOB
School of Bioprocess Engineering
University Malaysia Perlis
Perlis email: firstname.lastname@example.org
6 January 2011
•the particular problem
• your expertise
• the apparatus or equipment available.
The analyst should be involved in every step.
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 analysis
3)What type of sample to be analyzed
Once the problem is defined, next question:
How sample is to be obtained
How much is needed
What separation may be required to eliminate interference
Complexity of the sample and the number of component in the 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 sample for laboratory test
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
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 pretreatment
The organic materials sample are analyzed for inorganic constituents
The organic constituent may be destroyed by dry ashing
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..
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
Why conduct chemical separation?
1)To eliminate interference
2)To provide suitable selectivity in the measurement
3)To preconcentrate the analyte for more sensitive or accurate measurement
Methods of carrying out the measurements:
Calibration and measurement
• y = mx + b
• y – measured signal
• x – concentration
• Calculate x from value of y for analyte
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.
Volumetric flasks are calibrated to contain an accurate volume.
See the inside back cover of the text for tolerances of Class A volumetric glassware.
Fig. 2.2 Volumetric flask.
Volumetric pipettes accurately deliver a fixed volume.
Fig. 2.3. Transfer or volumetric pipettes.
Measuring pipets are straight-bore pipets marked at different volumes.
They are less accurate than volumetric pipets.
Fig. 2.4. Measuring pipets.
Syringe precisely deliver microliter volumes.
They are commonly used to introduce samples into a gas chromatograph.
Fig. 2.5. Hamilton microliter syringe.
These syringe pipets can reproducibly deliver a selected volume.
They come in fixed and variable volumes. The plastic tips are disposable.
Fig. 2.6 Single-channel and multichannel digital displacement pipets and microwell plates.
Fig. 2.7. Measuring cylinder.
Use these for quantitative transfer of precipitates and solutions, and for washing precipitates.
Fig. 2.8. Wash botltles: (a) polyethylene, squeeze type;
(b) glass, blow type.
Next topic: Basic statistics
1.What is quantitative analysis
2. State the phases of carrying out tests using instrumentation for quantitative analysis in the right order