PHU11103 - Short Q answers

isocractic elution

the mobile phase composition remains constant throughout the column

gradient elution

the composition of the mobile phase changes throuhgout the column during separation to imrpove resolution (ensure no components maintain totally retained at start of column)

limit of detection

amount of sample which gives signal equal to 3 times that of the baseline noise

limit of quantification

signal from analyte must be equal to 10 times that of baseline noise.

linearity range

range of analyte concentrations that give a linear response

4 limitations of beers law

the incident ratio is monochromatic / incident ratio is not sufficient to significantly alter the ground state population of the absorbing molecules / sample must be homogenous / absorbing species must behave as independent moieties

chemical interference

any chemical process that increases or decreases absorption or emission of the analyte (potential reactions)

5 types of detector

flame ionisation / universal / thermal conductivity / mass spectrometer / electron capture

normal phase chromatography

stationary phase is polar / mobile phase in non polar

reverse phase chromatography

stationary phase is non polar / mobile phase is polar

3 detectors used in HPLC

mass spectrometer / UV VIS absorbance detector / fluoresence detector

5 limitations of gas chromatography

limited to low molecular weight compounds / compound must be volatile or capable of derivitisation to be made volatile / only 15% of organic compounds can be analysed / cannot be used to prepare compounds for further use / limited number of separation methods compared to HPLC

5 Advantages of HPLC

rapid development / shorter distance / higher resolution / detection limited increased times ten / 3 times the number of theoretical plates

split injection

sample rapildy injected through septum and vapourised in injection port / most of sample goes to waste and only small percentage goes through the column / non vapourised components remain in injector

splitless injection

most of sample vapourised and transferred to column / used for dilute samples and trace analysis / larger volume so injection speed slow / more time required so temperature must be kept low enough to prevent decomposition

on column injection

sample introduced directly to column and not vapourised

6 properties of an internal standard

similar physical and chemical properties to analyte / stable / does not react with analyte / not present in the sample / good resolution / give reproducible peaks when analyte concentration changed

ion pair chromatograpghy

reserve phase, stationary phase and mobile phase with ion pairing component / long alkyl chain with positive or negative ion at the terminus

resolution

how well 2 elution peaks can be differentiated in chromatographic separation

spectrophotometer

light splitter passes light through a reference cuvette and sample cuvette which allows immediate comparison of results / mirror adjusted so only one frequency of light bounces into exit slit so only one frequency of light studied

packed vs capillary tube (capillary is ... for all)

better resolution / require smaller sample volumes / lower internal diameter / longer columns

ion exchange chromatography

involves ions of opposite charge which have columbic interactions / may cause ion induced dipoles / resin is positive or negative as has affinity for charged parts of molecules

applications of TLC x5

analysis of plant products / pharmacopoeial tests / kinetic studies / separate biochemical metabolites / determine purity of sample

columbic interactions

electrostatic interactions between electrical charges and follows columbs law

structure eludication

process of determining the chemical structure of a compound / used during chemical research or product development to confirm structural identity of a chemical compound

3 processes used in structure eludication

mass spectrometry / xray crystallography / infrared spectroscopy

test for identification definition

verify the identity of the API in a product and discriminate between products of nearly related structures

A in beers law stands for

absorbance

L in Beers law stands for

length of sample cell (always 1)

E in beers law stands for

absorbance of 1M solution at 1cm - molar absorptivity

C in Beers law stands for

molar concentration

Io in beers law stands for

incident ratio

A1% 1cm in beers law stands for

specific absorbance - absorbance of 1% solution at 1cm

is specific absorbance = molar absorptivity in beers law

no

5 applications of UV-VIS spectrometry

qualitative analysis - test for purity, determine structural components and identity / quantitative analysis / pka value / reaction kinetics / partition coefficients and solubility

size exclusion chromatography

microporous polymeric beads used and big things do not get stuck but small things do so big things come out first

application of size exclusion chromatography

antibody analysis

what to do if substance not volatile enough for GC x3

make it an ester / amide / ether

what is used as the mobile phase in gas chromatography / function of mobile phase

inert gas like helium or nitrogen / carry analyte molecules through the column

does the mobile phase in GC have a role in separation

no

is their gradient elution in gc / what type of elution is there

no / temperature

what plays a role in separation in GC

temperature

retention time

time taken for the substance to travel through the column from the time of injection to the time of detection

4 factors affecting retention time

column length / flow rate of gas / operating temperature / proportion of the stationary phase

symbol for molar absorptivity

E

4 factors affect molar absorptivity

size of absorbing system / probability of transition / wavelength / solvent

atomic emission spectrometry (AES)

atoms are thermally excited and emit light that is quantified

3 advantages of atomic emission spectroscopy

robust / cheap / selective for quantification of metals

what is AES only applicable to

alkali and alkali earth metals

atomic absorption spectroscopy AAS

absorption of electromagnetic radiation by an atom in its ground state and it is promoted to the excited state / higher state unstable and temporary / atoms return to ground state with emission of radiation that is measured

3 components of spectrophotometer

light source / monochromator / sample compartment

what is the visible spectrum of radiation in AAS

400 - 800 nanometres

why are very small silica particles used in HPLC

increases number of barriers to be crossed so increased separation

standardisation og herbal medicines def

process of developing and aggressing upon technical standards which is done using chromatography

why are herbal drugs standardised

must be free from impurities like soil and dirt and contaminants like fungi and insects

chemical standard

substance where exact composition is known

complex tissues

2 or more different types of cell

3 examples of complex tissues

xylem / phloem / epidermis

what herbal plant was an alkaloid used to treat malaria for 3 centuries

quinine

artemisia annua L

ancient chinese herb used to treat fever

artemether

derivative of artemisia annua l developed to treat malaria

atroponine

anticholinergic drug extracted from atropa belladona - causes pupil dilation

simple tissue

same type of cell throughout whole tissue

4 points on parenchyma

most abundant cell type / large vacuoles / thin walls / sphere shaped

chlorenchyma

parenchyma tissues with chloroplasts / used in photosynthesis

aerenchyma

parenchyma tissues with connected air spaces

ray parenchyma

transport laterally in woody stems

collenchyma x3 points

thick walls / beneath epidermis / contains living cytoplasm

sclerenchyma x4 points

thick tough walls with lignin / dead at maturity / function for structure support and protection / 2 types

2 types of sclerenchyma

sclereids / fibres

5 steps in production of herbal drugs

cultivation / harvest / drying / fragmentation / storage

function of drying herbal plants x2

prevents microbial growth / prevents plant enzymes altering chemical composition