mark p barrow mass spec

what does mass spec measure

analyse sample : single or mixture

need gas phase ions

measures mass to charge ratio (m/z) not mass

what is m/z

m is mass measured in daltons or unified atomic mass (u),

1 uor Da is 1.6 × 10^-27kg. no need to rmbr

z is charge of ratio

q is total charge in coloumb.

q= z x e

where e is elementary charge

what does mass spectra shhow or measure

intensity or abundance as function of m/z

what is zeroeth order

dont call it mass spec, spec involves absorption of electromagnetic radiation

difference between relative intensity and absolute intensity and whats molecular ion and base peak

intesntiy: how many ions reached detector

absolute This is the actual number of ions detected.

Relative intensity

Mass spectra are never usually plotted using absolute intensity.

Instead, the tallest peak is set equal to 100%

Everything else is compared to that.

3) base peak

assigned to 100 percent of intensity

molecular ion: original molecule losing one electron

components of mass spectrometer

sample inlet

ionisation method

analyser

detection

data system

how do you combine LC and mass spec

why are vacuum systems needed in mass spec

vacuum needed for ions to pass thru mass spec, need to avoid collision between ions and gas

atmospheric (1 atm)

what are isotopes

same number electron, different neutron so will have diff mass to charge ratio. often called isotopologues

whats shown here

monoiso= no heavy isotope

isotopologues = isotopes

different ways of c5 shwon

whats mass error and its equation

mass observed- mass calculated/m calc x 1,000,000

its a figure of merit, better mass allows to have higher confidence in assignment

llower values are better (ppm)

whats resolving power and its equation

m/ change in m m being width

allows to observe closely spaced peaks

higher values are better (narrow)

theres 6 types of sampling in mass spec what is it

sample collection

sample preperation

ionisation

mass spec

structure / siomers

data

for archaelogist samples, what to need to be wary of

value of samples

contamination

ethical consideration

limted sample amount

destructive sampling

pro and con of grab sampling

pro:simple

considers heterogeny

con: specific location depth

time to ravel

scope of citizen science

represents snapshot

pro and con of environmental monitoring : passive sampling

pro:

easy to deploy , useful to remote location

power not required

less labour

con:

using membrane?

hours days week requried

samples over period of time but suitable for low level

how to get core samples in envrionemtnal sampling

use plastic tube extract sediment core,

whats soxhlet extraction and its key features

solid sample in thimble, cycles of washing and repeated vaporisation, high exctraction efficacy

whats the concentration of electrospray ionization

0.01 uM for single compounds

0.01-0.1 um for complex mistures

you need to consider different additives for different ionisation methods

what can help with ESI

MALDI

acid for positive ion elecropsray esi

and base for negative ion electrospray esi

matrix for maxtrix assisted laser desorption MALDI

DOPANT such as toluene for atmosphereic pressure photoionisation

steps for SPE solid phase exctraction

conditioning

loading

washing

elution

method to extract sodium out

what happens in LLE liquid liquid extraction

extract liquids from eachother by adding immiscible solvent and seperate layers and get the one you need

When would these methods be needed

ESI

APPI

LDI

MALD

EI

EI ionisation for hard gas phase

Atmospheric pressure photoionisation for intact large molecules

laser desorption ldi for soft condensed phase

maldi for soft

and ESI

what does electron ionisation look like and its formula

typically operated at 70eV

EI is not suitable for what type

peptides, proteins and other biomolecules

whats maldis key features

soft ionisation technique

uses laser

ions observed are typically protonated

[M+H}+

maldi uses either CHC, SA, DHB, when do we use what for what

CHC is forsmall peptides

SA for large proteins

DHB for proteins or carbohydrates

how do we prepare maldi target for analysis

you put them in a spot tray

number average and weight average formula

ESI key features

soft ionisation,

useful for many biomolecular

good snesibility

can multiply charges

mechanism of ESI

Needle.

syringe

soltuion then needle

entrance of mass spec

dry if gas

what are the 3 models for production of ions by ESI

Why does isotope spacing change?

Mass spectrometers measure mass-to-charge ratio (m/z), not mass.

Each isotope (e.g. one ¹³C instead of ¹²C) increases the mass by about 1 Da.

That 1 Da increase is divided by the charge:

Δ(m/z)=1z\Delta(m/z)=\frac{1}{z}Δ(m/z)=z1​

Therefore:

• 1+ ion → spacing = 1.0 m/z

• 2+ ion → spacing = 0.5 m/z

How can you determine the charge state from isotope peak spacing?

Measure the distance between two neighbouring isotope peaks.

z=1/change over M

Peak spacing	Charge
1.0	1+
0.5	2+
0.33	3+

whats it showing

This means:

• M = protein (ubiquitin)

• +10H = ten protons added

• Overall charge = 10+

So the mass spectrometer measures

protein mass+10H

instead of just the protein mass.

The same protein can gain different numbers of protons (e.g. 7+, 8+, 9+, 10+), giving different m/z values and therefore multiple peaks.

how would you determine n

key features of APPI

soft ionisation

include UV lamp

higher flow rates than ESI

can form radicals