chromatography

analytical technique used to separate and identify compounds/components in a mixture based on the Rf values (TLC) or retention times (GC/CC) thin layer chromatography gas chromatography column chromatography

Rf is the retention factor. it is the ratio of the distance travelled by spot : distance travelled by solvent front on the plastic plate in TLC therefore eq is Rf = distance travelled by spot / distance travelled by solvent front greatest it can be is 1 it identifies compounds because each one has a unique one the Rf value changes based on temperature, what solvent is used, different plate types in TLC, different type of chromatography. so any comparison must be made under same conditions

time it takes for a compound to travel through a chromatography column and be removed at detector by being washed with a solvent (eluted)

verb - elute it is the process of extracting one material from another (separating a component from a mixture) by washing with a solvent. its the whole process of the chromatography, the compounds moving through the solvent and hence being separated by their differential solubility in the mobile phase and retention in the stationary phase the fluid used to elute a substance = solvent = eluent

aka, what about chromatography separates the components of a mixture? separation depends on the balance between solubility in the moving phase and retention by the stationary phase so all chromatography includes an s phase and m phase so can eparate compounds based on their solubility… and retention… .

substances are separated according to relative affinity to stationary and mobile phase. if they are more attracted to, soluble in, stationary phase, their retention time will be longer/ their Rf value will be smaller if they are more attracted to, soluble in, mobile phase, their retention time will be shorter/ their Rf value will be larger

solvent molecules can move through it if you have a greater affinity for, solubility in, solvent you will move further/faster

solid (CC) or liquid on solid support (GC) molecules can’t move through. they adsorb? if there is higher retention by stationary phase, then compounds will travel less distance

TLC plate coated with solid of SiO2 or Al2O3 COLUMN C solid powder of SiO2 or Al2O3. GAS C high bp liquid on solid. on the inside of the column, the liquid is immobilised inside the column.

glass or plastic plate coated with solid SiO2 or Al2O3 powder. s phase = solid m phase = solvent the sample is dissolved in

• revealed by UV light. shine it on it. (because component of s phase is normally fluorescent) the sample spots will be unfluroesced therefore visible • amino acid chromatagrams shown by ninhydrin. gives them colour • iodine vapour. shows up as browny spots

compounds that have greater affinity, higher solubility in it, so large Rf value, are (likely to be) non polar and vv; if a solvent is polar and theres high Rf value, that means there was high attraction and compound is polar and vvvv; applies to s phase i think

glass column/tube packed with stationary phase of solid SiO2 or Al2O3 powder. non polar organic solvent as m phase,, is added to cover powder theres a plug at the bottom to prevent stuff leaking out sample, dissolved in minimal solvent, is poured into top. and the retentin time is recorded, time taken to reach bottom. not analysing how far but how long it takes to reach same point.

preparative it separates compounds out so can get pure sample

column packed with a solid OR packed with a solid coated by a liquid that is immobilised ^^the s phase options the m phase is an inert gas that is passed through the column. under pressure at high temps. the samples analyses partition between the gaseous mobile and the liquid stationary phase. a detector transmits signals to a display processor, where peaks represent a compound in the mixture passing through a detector. area under peaks shows relative quantities of compounds present

TLC dissolved in solvent GAS C dissolved in solvent and vaporised COLUMN C dissolved in minimal solvent

TLC solvent front is used to calculate Rf, so its movement is required GAS C solvent would make a reading on display and in MS afterwards, but because solvent is carefully chosen, they know what it is and can ignore it. it is chosen to be volatile so you can ignore its peak in the display of the GC, and acts almost like a solvent front COLUMN C ?

• analytical technique used to identify and quantify chemical substances by measuring the mass-to-charge ratio of ions. • involves sorting gaseous ions in electric fields, so can determine a sample’s chemical composition. • results are typically presented as a mass spectrum, which plots current intensity against mass-to-charge ratio

• vaporisation • ionisation. this is so can be accelerated by magnetic field and be discharged at detector plate a. it is done by either electron impact: b. or electrospray ionisation • accelerated using electric field towards detector plate. • drift - they are accelerated so all have same KE, but bc different atomic masses (bc isotopes/different elements), have different velocities. • detection - so they reach detector plate at different times • data - relative abundance on y and m/z on x

dissolved in polar solvent led though capillary needle needle is surrounded by an electrode so a high voltage is applied to a sample in a polar solvent sample molecule gains proton. M + H+ –> MH+

it is a powerful analytical technique to identify compounds but the sample must be pure, you can’t just put the mixture in it so by associating it with GC, compounds are separated using the chromatography and then analysed using mass spec

polar