quadrupole mass analyser Faiza hassan

quadrupole mass analyser

1. Topic: Quadrupole Mass Analyzer Course code: CHEM-421

2. Submitted To: Dr. Waseem Mumtaz

3. Submitted By: Faiza Hassan 11011507-023 Analytical chemistry majors Semester 8 th

4. Mass analyzers: It is component of mass spectrometer that receives ions and separates them on the basis of their mass to charge ratio. outputs them to the detector where they are detected and later converted to a digital output.

5. Quadrupole Mass analyzers: The type of analyzer which is used to separate the ions on the basis of specified charge to mass ratio. Or An instrument for measuring the relative amounts of different gases in a mixture. The gas could be atmospheric air, could be evolved from a chemical process, might be trapped inside a small mineral sample, or even be dissolved in a liquid such as sea water.

6. Specifications: Mass range 10–4000 daltons ( amu ) Resolution, typically 1000 Scan rate 5000 daltons /min Accuracy .1–.2 daltons

7. Principle: It consists of four cylindrical rods, set parallel to each other provided by AC and DC source . Lets one mass pass through at a time. Can scan through all masses or sit at one fixed mass.

8. Quadrupoles have variable ion transmission modes

9. Construction : It consists of three components The ion source Quadrupole mass filters The Detector

10. 1. The Ion Source Molecules from the gas sample are ionised by energetic electrons from a heated filament. 2. The Quadrupole Mass Filter A mixture of a.c . and d.c. voltages applied to opposite pairs of cylindrical metal rods allow ions of a chosen mass to pass from the ion source to the detector. All others are rejected. Varying these voltages allows different masses to pass in turn and a scanned spectrum is produced. 3. The Detector Chosen ions are detected and generate a measured current that is used to construct the mass spectrum.

11. The DC bias will cause all the charged molecules to accelerate and move away from the center line, the rate being proportional to their charge to mass ratio.  If their course goes off too far they will hit the metal rods or the sides of the container and be absorbed. So the DC bias acts like the magnetic field B of the mass spec and can be tuned to specific charge to mass ratios hitting the detector.

12. ‘ tripple quadrupole ’ arrangement Q1 Q2 collision Q3 We can characterize molecules via a number of MS/MS modes: Fragment Ion Scan : Q1 Fixed, Q2 Collide, Q3 Scan Precursor Ion Scan : Q1 Scan, Q2 Collide, Q3 Fixed Neutral Loss Scan : Q1 Scan, Q2 Collide, Q3 Scan - offset

13. Quadrupole Limits: m/z limit: Depends on the maximum RF potential that can be applied to the quadrupole rods. Normally goes to about 7000 V. The practical limit is about 10,000 – 15,000 V for electronic and arcing reasons. 7000 V translates into a limit of about 5000 m/z.

14. Benefits: Classical mass spectra Good reproducibility Relatively small and low-cost systems Low-energy collision-induced dissociation (CID) MS/MS spectra in triple quadrupole and hybrid mass spectrometers have efficient conversion of precursor to product

15. Quadrupole Limits Resolution: Not for high resolution mass spectra. in a quadrupole , higher resolution = lower sensitivity . Sensitivity : Inversely proportional to resolution Mass Accuracy: Partly depends on the precision with which you can control U and V… which is highly accurate. Around .1 Da on new instruments

16. Applications: Great for most organic chemistry applications. useful is in liquid chromatography-mass spectrometry Also used in gas chromatography-mass spectrometry where they serve as exceptionally high specificity detectors. Used for measuring the relative amounts of different gases in a mixture.