ICPMS Trace elements and cannibis Flashcards
What is the proccess of ICP-MS
- Sample introduction
- ICP torch and RF coil
- Interface
- Vacuum
- Universal Cell
- Mass spec
- Detector
What happens in sample introduction
nebulizer and spray chamber - only small droplets enter torch
what happens in the ICP torch and RF coil
argon plasma turns liquid into dried solid, then heated to gas - releasing one electron
What are interferences that can happen in the universal cell
ions generated from the plasma or sample carry the same m:c as the analyte ion
what are ways we fix interferences in the universal cell
chloride correction (math) or collision/reaction cell
what are the 3 modes in the universal cell
Standard, collision, reaction cells
what does a collision cell aka Kinetic Energy Discrimination do
removal based on size using inert gas
cons; background decreases BUT analyte signal decreases too
what does a reaction cell do
removal based on chemical reactions using reactive gas
interferent -exothermic rxn
analyte - endothermic rxn
(better than collision cell bc background decreases and anaylte presernved)
what is the pathway of atomic absorption
light -> chopper -> cuvette/sample -> Detector
another name for the light source in atomic absorption
HOLLOW CATHODE LAMP
- specific for each element being tested
-filled w argon or neon
-quartz glass
what is the principle of the light source
Current applied to cathode will cause ionization = causes sputtering (release metal atoms)
sputtering increases atomic vapor -> collision with inert gas = excitation of atoms = radiant energy and return ground state
what is the principle of sample introduction in atomic
nebulization -> evaporation -> atomization
what is atomization
element attracts e- and produces ground state metal atom
what is emission interference and how to counter it
Light emitted from light source will reach detector - use a chopper bt the lamp and flame
what does the chopper do
pulse beam of incident light to distunguish background and true analyte
what are the two flameless atomic absorption methods
cold vapor and
graphite furnace
both converted into atomic vapor by atomization
princple of cold vapor generation assembly
limited to mercury analysis at RT
uses digestion with acids and sodium borohydride then
quartz window in optical beam
princple of graphite furnace
sample placed on solid support;partition tube
electrical resistance to dry, charr, and atomize
temperatures of graphite furnace stages
dry = 100-120
ashing = 400-800
atomization = 2600
purpose of photomultiplier tubes
detector to measure intensity of signal from monochromator
principle of PMT tubes
crescent shapred dynodes create secondary emission of e- that amplifies signal
main pros and cons of ICP MS
pro = multianalyte analysis with less sample and prep
con = cost
difference of trivalent and hexavalent chromium
3 = essential for human fxn
6 = non essential
where is a source for selenium
soil - animals will have feed w selenium if soil does not contain
