Mass Spectroscopy – Pharmacognosy & Phytochemistry
1.Which of the following statementisfalse for mass spectroscopy?
A. Mass spectroscopy is used to identify unknown compounds within a sample, and to elucidate the structure and chemical properties of different molecules
B. Particle are characterized by their massto charge ratios(m/z) and relative abundances
C. This technique basically studies the effect of ionizing energy on molecules
D. This technique can be used on allstate of matter
Explaination: A massspectrum measuresthe masses within a sample. Particles are characterized by their massto charge ratios(m/z) and relative abundances. This technique basically studies the effect of ionizing energy on molecules and is applied to pure samples as well ascomplex mixtures. This technique is only possible to perform in the gaseous state.
2.Which of the following main component of mass spectroscopy deal with resolving the ionsinto their characteristics mass components according to their mass-to-charge ratio?
A. Ion Source
C. Detector System
Explaination: The complete process involves the conversion ofthe sample into gaseousions, with or without fragmentation, which isthen characterized by their massto charge ratios(m/z) by an analyser. Eventually, the second analyzer will analyse fragment the selected ions and detect the ions emerging from the last analyzer and measure their and relative abundances
with the detector that converts the ionsin to electrical signals.
3.Who discovered the mass spectrometer?
C. ErnestO. Lawrence
Explaination: The mass spectrometer wasinvented by JJ THOMSON.He performed a series of experimentsin 1897 designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. Further modified by F.W.Aston shortly after World WarI. He constructs the first velocity focusing masss pectrograph which has massre solving power of 130.
4. In which state of matter mass spectroscopy is being performed?
Explaination: In the mass spectrometric analysis of compound sisfirstly done by production of gas phase ions of the
compound, basically by electron ionization. This molecularion under goes fragmentation.
5.APMR spectrometer operates at 300 MHz. Find the value of magnetic field.Given: g = 5.585 and B = 5.05 x 10 JT .
A. 7.05 T
B. 6.38 T
C. 7.58 T
D. 5.93 T
6.What are the main criteria on which mass spectrometer used for?
A. Composition in sample
B. Relative mass of atoms
C. Concentration of elementsin the sample
D. Properties of sample
Explaination: A mass spectrometer generates multiple ionsfrom the sample under investigation, it then separates them according to their specific mass-to-charge ratio (m/z) or we can say on relative mass of atoms, and then recordsthe relative abundance of each ion type
7.Acompound of molecular formula C H ClO shows a prominent band in itsIR spectrum at 1690 cm . HNMR spectrum
revealed only two major types of protonsin the ratio of 5: 2.Which one of the following structures best fitst he above data?
8.Which species of the following is used to bombard with the sample for which mass spectroscopy has been performed?
Explaination: In the mass spectrometer,the sample which isto be analysed is bombarded with electrons, which leadsto the formation of the ions. The ions are sorted out by accelerating them through electric and magnetic field.Arecord of the number of different kinds of ionsis called massspectrum.
11. Separation of ionsin mass spectro metertake place on the basis of which of the following?
C. Molecular weight
D. Massto charge ratio
Explaination: Mass spectrometer separatesions on the basis of massto charge ratio i.e. m/z. In the spectrum of a pure compound,the molecularion, if present, appears atthe highest value of m/z (followed by ionscontaining heavierisotopes) and givesthe molecular mass ofthe compound. Most ofthe ions are singly charged.Hence,the massto charge ratio is equal to the mass.
12.Which type of ionicspecies are allowed to pass through the slit and reach the collecting plate?
A.Negative ions of all masses
B. positive ions ofthe specific mass
C. Negative ions ofthe specific mass
D. Positive ions of all masses
Explaination: Positive ions ofspecific mass pass through the slit and reach the collecting plate. The ion currents are measured using sensitive electrometer tube. The ionsreaching the collecting plate are measured.