Mass Spectrometry | A-level Chemistry | OCR, AQA, Edexcel

Mass Spectrometry in a Snap!

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The key points covered in this video include:
1. What is Mass Spectrometry?
2. TOF Mass Spectrometry
3. Low Resolution Mass Spec
4. Analysing Spectra

What is Mass Spectrometry?

Mass Spectrometry is a form of molecular chemical analysis. There are many different types of mass spectrometer. All work on the same principle: 1. Form ions from sample, 2. Ions separated, According to Mass to Charge ratio, 3. Ions detected. Mass Spectrometry can be used to: Provide structural information, Identify an unknown compound, Determine the relative abundance of each isotope of an element.

Time of Flight Mass Spectrometry

Apparatus under Vacuum. This excludes air, Prevents the ions from colliding with air. Step 1. Ionisation. The sample is dissolved in a volatile solvent, The vaporised solvent is forced through a hollow needle. This is connected to the +ve terminal of a high voltage supply, This produces tiny positively charged droplets. These tiny droplets have lost electrons, The solvent then evaporates, As a result of this, the droplets reduce in size. They are reduced single positively charged ion. Step 2. Acceleration. The positive ions are attracted towards an electric plate. This plate is negatively charged and causes the ions to accelerate, The ions accelerate towards the plate so that all ions have the same kinetic energy. Therefore the larger, heavier particles will have a lower speed. Speed 3. Ion Drift. The ions pass through a hole in the negatively charged plate. This forms a beam, The beam of ions travels along a tube. This is the Flight Tube. Step 4. Detections. When the ions arrive at the detector, their flight times are recorded. At the detector, the positive ions pick up an electron, This causes a current to flow. Step 5. Data Analysis. The detector passes a signal to the computer. This generates a mass spectrum.

Low Resolution Mass Spectrometry

Chlorine has 2 isotopes. Isotopes are atoms with the same number of protons and different numbers of neutrons. Each isotope has a slightly different mass. Cl35, CCl37. As a result, the isotopes will have a different m/z ratio. They will be detected separately. Mass spectrometry can be carried out to a high level of precision. Up to 5 decimal places. When done to 1 decimal place, the process can be called Low Resolution Mass Spec.

[apolloscharm]

It feels like Hermoine Granger is teaching it

[ブランドン-hb]

Our caribbean exams are really similar to yours and honestly you are a godsend

[bishrbourghli]

you whizzed through how it works and then spent 5 minutes explaining relative abundance and that there is 25% and 75%, thats not the bit i was struggling with xD

[ramenyoun]

Good luck for the Autumn session lads!

[horlarlexy]

Sorry Lads





But it gets wayyy more difficult and confusing

[shajalal]

Love your explanation. Seriously no doubt now in this topic.

[CHANELLEPLAYS]

I seriously don't understand anything here

[ellieellieellie-]

So is deflection the same as ion drift for question 2? It seemed in your explanation that acceleration caused the ions to separate, is that incorrect?

[madlaz]

Why is she going so fast? We come here because we don’t get it...yet she’s whizzing through it

[subhanm]

How do you calculate time of flight? When you are given kinetic energy and velocity????

[tomlefish]

where do you mention deflection? did you mean detection coz I'm confused

[aidaeshraghi]

Hello I love these helpful videos but like the pace at which the explanations are being said are too fast for hearing and understanding at the same time. I would be grateful if you could lower the pace of speech in the future videos. Thank you

[kma]

To find the relative atomic mass, why do we need to divide it by 100??

[izziecarter]

On which video do we swap from AS to A level ?

[peterdrake]

Mass spectrometers produce a mass spectrum not a mass spectra. Spectra is plural.

[amanullah]

What software you used to make this slide presentation?

[mlyka]

The lip smacking noises are low-key annoying 😂😂😂

[libbyharris]

In electrospray ionisation, are the particles ionised by gaining a proton from the solvent or by the large positive charge of the needle? I've read both and I'm not how to reconcile the two. I'm doing AQA A Level Chem btw :)

[arifmammadov]

Why are the relative atomic masses of many isotopes decimals and not whole numbers?

[Lopooop]

she talks way to fast maybe talk a little bit slower 😁