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a)
Interpretation:
The working of solid-phase microextraction technique along with the necessity of cold trapping during injection with solid-phase microextraction and also the extraction of an analyte into the fibre in solid-phase micro extraction has to be explained.
Concept Introduction:
Solid-phase microextraction:
The extraction of compounds from liquids, air or sludge without any solvent is called as solid-phase microextraction. The major component is the fused-silica fibre coated with 10-100μm thickness in film of stationary phase exactly to those used in gas chromatography.
The mass of analyte absorbed in the coated fibre is calculated using the formula,
m=KVfc0VsKVf+Vs
Where Vf = volume of film on the fibre
Vs = volume of solution that is extracted
c0 = initial concentration of analyte in the solution that is extracted
K = partition coefficient for solute between film and solution.
Cold trapping:
Cold trapping is one of the alternative method for the condensation of solute in narrow band at the starting of the column.
To explain the working of solid-phase microextraction technique along with the necessity of cold trapping during injection with solid-phase microextraction and also the extraction of an analyte into the fibre in solid-phase microextraction
b)
Interpretation:
The differences between stir-bar sorptive extraction and solid phase microextraction has the explained. The one is which is sensitive and reason has to be given.
Solid-phase microextraction:
The extraction of compounds from liquids, air or sludge without any solvent is called as solid-phase microextraction. The major component is the fused-silica fibre coated with 10-100μm thickness in film of stationary phase exactly to those used in gas chromatography.
The mass of analyte absorbed in the coated fibre is calculated using the formula,
m=KVfc0VsKVf+Vs
Where Vf = volume of film on the fibre
Vs = volume of solution that is extracted
c0 = initial concentration of analyte in the solution that is extracted
K = partition coefficient for solute between film and solution.
Stir-bar sorptive extraction:
Stir-bar asorptive extraction is closely related with solid-phase microextraction but is found to be ∼100 ~times more sensitive for trace analysis.
The mass of analyte that is extracted is given as,
m=KVfc0VsKVf+Vs
Where Vf = volume of film on the fibre
Vs = volume of solution that is extracted
c0 = initial concentration of analyte in the solution that is extracted
K = partition coefficient for solute between film and solution.
But there is raise in the volume of sorbent ( Vf) from ∼0.5μL in solid-phase microextraction to 25-125μL in stir-bar asorptive extraction. Hence, the analyte is 50-250 times more extracted with stir bar.
To explain differences between stir-bar sorptive extraction and solid phase microextraction and to give the most sensitive technique with reason
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Chapter 24 Solutions
Quantitative Chemical Analysis
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