instrumentation Flashcards
mass spectrometer
used to analyse blood of race horses for drugs, identify substances
Atomic Absorption Spectroscopy (AAS)
used to analyse water samples for heavy metals (Cd, Hg, Pb)
GC
used with MS in drug testing also blood alcohol levels
HPLC
used to separate less volatile mixtures eg. growth promoters in meat
IR spec
used to identify functional groups + identify drugs
UV spec
quantitative used to find amount of organic substances
eg. drugs
instruments
gas chromatograph mass spectrometer atomic absorption spectrometer high-performance liquid chromatograph infrared spectrometer ultraviolet absorption spectrometer
Gas Chromatograph - principles
different components of a mixture have diff interactions w/ the stationary + mobile phases
Gas Chromatograph - processes
- injection
- transport of sample along column
- separation in column
- detection
Mass Spectrometer - principles
positively charged ions are separated on basis of their relative masses in a magnetic field
Mass Spectrometer - processes
- vaporisation
- ionisation
- acceleration
- separation
- detection
Atomic Absorption Spectrometer - principles
ground state atoms of an element absorb light characteristic of that element. Absorbance is directly proportional to concentration
Atomic Absorption Spectrometer - processes
- Sample soln sprayed into a flame + sample element converted into atoms of that element
- Ground state atoms absorb radiation from source made from element
- Absorbance measured
High-performance liquid chromatograph - principles
Different components of mixture have different tendencies to absorb onto v. fine particles of a solid in the HPLC column
High-performance liquid chromatograph - processes
- injection
- transport of sample along column
- separation in column
- detection
infrared spectrometer - principles
- Molecules of a substance absorb infrared light of different frequencies.
- The combination of frequencies absorbed is peculiar to the molecules of that substance
infrared spectrometer - processes
- IR radiation passes thru sample
- sample absorbs IR radiation at specific wavelengths which are detected
- absorption spectrum is obtained
ultraviolet absorption spectrometer - principles
- Absorption of UV radiation by molecules results in the promotion of electrons from their ground state energy levels to higher energy states
- Absorbance is directly proportional to concentration
ultraviolet absorption spectrometer - processes
- UV light passed through sample and a blank
- absorption spectrum is obtained
use of thin-layer chromatography in forensic science
the separation of dyes taken from fibres
procedure: separate components in a mixture of indicators using paper chromatography
- add solvent to bottom of tank. Cover, allow to stand for a few hours - become saturated w/ solvent vapour
- draw line near top of rectangular sheet of chrom. paper and just above eluent
- place small spot of each indicator + mixtures at diff points on line near bottom of paper using capillary tube. Allow to dry
- place in tank, ensuring solvent level is below line spots of indicators
- run the chromatogram until solvent reaches line near top of paper
(diagram in sheet)
procedure: separate components in a mixture of indicators using thin-layer chromatography
- using capillary tube, place small spot of each sample near bottom of plate just above eluent. Allow to dry.
- stand plate in tank with eluent, ensuring samples are above the surface of the liquid
- Cover tank, allow solvent front to rise up to plate near top.
(diagram in sheet)
How to purify impure copper by electrolysis
-incl diagram
- battery used as power supply
- copper sulfate electrolyte
- impure copper acts as anode, is oxidised
- pure copper acts as cathode
- copper ions (Cu²⁺) in soln reduced, pure copper plates out on cathode
Copper electrolysis - equation for reactions that take place at electrodes
Cu²⁺ + 2e⁻ –> Cu
Cu –> Cu²⁺ + 2e⁻
