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Subject Code : ALU8002
Country : Australia
Assignment Task

ALU8002 - Advanced Analytical Tools for Food Security

Question 1. Briefly summarise the fundamental principles of the technique Inductively Coupled Plasma Mass Spectroscopy (ICP-MS).

 

Question 2. An ICP-MS iCAP Qs can be considered as 4 distinct functional units, for optimum performance, each of the units must be optimized by the operator. What is the correct order of these units in terms of sample progression through the system?
a - injection of the ions into the vacuum system > mass filtering by quadrupole > mass filtering by hexapole > amplification + measurement
b - sample introduction > injection of the ions into the vacuum system > mass filtering by quadrupole > signal amplification + measurement.
c - sample introduction > injection of the ions into the vacuum system > mass filtering by hexapole > signal amplification + measurement.
d - injection of the ions into the vacuum system > separation of the ions by mass/charge > focusing of the ion beam by the electrostatic lenses > signal amplification + measurement.
e - sample introduction > injection of electrons into the vacuum system > mass filtering by quadrupole > signal measurement + amplification.

Describe how you might begin to troubleshoot a sensitivity problem?


Question 3.  A concentric nebulizer is a free aspirating nebulizer that generates a sample aerosol with a wide range of droplet sizes. What is the mean droplet size that ICP works efficiently with? and what percentage of the original sample aerosol actually has the correct size and travels to the plasma for ionization? 
a -  1 mm, 5% 
b - 100 µm, 1%   
c -  20 µm, 10%   
d - 10 µm, 1% 
e - 1  µm, 0.1% 
How might you know that there is a sample aspiration problem?


Q4. The functions of the Peltier-cooled Spray Chamber are to: 
a  -  stabilize the spray chamber temperature to reduce the effects of room temperature changes and reduce water vapor pressure in the spray chamber resulting in lower water loading of the plasma and lower oxide interferences
b  - stabilize the spray chamber temperature to reduce the effects of room temperature changes and increase water vapor pressure in the spray chamber resulting in lower water loading of the plasma and lower oxide interferences
c  - stabilize the spray chamber temperature to reduce the effects of room temperature changes and reduce signal noise levels associated with peristaltic pump pulsation 
d  - increase water vapor pressure in the spray chamber resulting in lower water loading of the plasma and lower oxide interferences and reduce signal noise levels associated with a peristaltic pump 
e - increase the viscosity of the sample to increase the amount of sample reaching the plasma


Q5.  A characteristic of the argon ICP is that the great majority of the elements form mainly: 
a - double charged, negative ions
b - double charged, positive ions 
c - single charged, negative ions
d - single charged, positive ions
e - electrons 

What is the benefit of forming one ion species when it comes to ion quantification?


Q6.  Select the correct gas flow labeling 
Gas Flow Labling
a -  (i) Cool Gas (ii) Auxiliary Gas (iii) Nebuliser Gas (iv) Auxiliary Gas (v) Cool Gas (vi) Nebuliser Gas  
b -  (i) Cool Gas (ii) Auxiliary Gas (iii) Nebuliser Gas (iv) Cool Gas (v) Auxiliary Gas (vi) Nebuliser Gas  
c - (i) Auxiliary Gas (ii) Cool Gas (iii) Nebuliser Gas (iv) Cool Gas (v) Auxiliary Gas (vi) Nebuliser Gas  
d - (i) Nebuliser Gas (ii) Cool Gas (iii) Auxiliary Gas (iv) Auxiliary Gas (v) Cool Gas (vi) Nebuliser Gas  

What can happen to the plasma if the gas regime is not set-up correctly? 


Q7.  The first ionization potential of argon is 15.8eV and most elements achieve their first ionization potential at a temperature of approximately 7500K. This temperature is achieved at approximately 12-14mm from the load coil. What percentage of the elements in the periodic table are more than 75% ionized in an argon plasma? 


Q8. Monoisotopic elements require special consideration because of ion inferences. In which of the following lists do all the elements only have one stable isotope.


Q9. Sample and skimmer cones 
Skimmer Cones
Which of the following statements correctly describes the physical/chemical processes at the sample interface. 
a- A reduction in pressure as the plasma gas passes through the sample cone causes rapid gas expansion. This causes the gases to reach supersonic speeds. The resulting jet-flow makes it easier for the ion lenses to focus the beam. 
b- A reduction in pressure as the plasma gas passes through the sample cone causes rapid gas expansion. This causes the gases to reach supersonic speeds. This produces more positive ions and enhances the signal. 
c- An increase in pressure as the hot plasma gases pass through the sample cone causes the gas flow to rapidly condense. Beam narrowing insures the sample is more effectively transported through the cone and lens system.
d- An increase in pressure as the hot plasma gases passes through the sample cone causes the gas flow to rapidly condense. This causes the gases to reach supersonic speeds. The resulting jet-flow makes it easier for the ion lenses to focus the beam. 

What is the approximate cost of a Ni cone set? What is the cost of a Pt cone set? State a scenario where a Pt cone set would be an advantage? 


Q10.  We apply very specific voltages on the DC and RF rods so that at any one time, only one ion has the …… I…….. to cycle all the way through the ……ii……...
a - i) correction stability, ii) mass filter 
b - i) correction acceleration, ii) ion lens
c – i) correction acceleration, ii) electron multiplier 
d – i) size, ii) electron multiplier


Q11. Interferences can be defined on the basis of spectral and non-spectral. Examples of spectral interferences include ‘polyatomic’ and ‘isobaric’. Non-spectral inferences arise due to signal suppression and enhancement effects. Which of the following is not commonly used to overcome these interferences? 
a – Reduction in the sample (volume or concentration)
b – Internal standards     
c – Sample/standard matrix matching approaches 
d – Selection of a different isotope 
Explain the function of a CRM material? 


Q12. Mass spectrometry, and especially ICP-MS, suffers heavily from mass bias, or instrumental mass discrimination. The net result of this is the preferential transmission, most often of …i… ions through the mass spectrometer. This is a key problem for  ….ii….. 
a – i) heavier  ii) isobaric interference equations 
b – i) heavier  ii) internal standards 
c – i) lighter   ii) isobaric interference equations 
d – i) lighter   ii) internal standards


Q13. Abundance sensitivity is calculated as the ratio between the area associated with the analyte mass M and the area of the tail from the mass either above it or below it (M+1 or M-1). Typical abundance sensitivity figures with standard plasma are:


Q14. You are presented with an unknown water sample that your client wishes you to analyze for both major and minor elements on ICP-MS. What method from the ones listed below would be the most appropriate, given that you don’t know the elemental make-up of the sample? 


Q15. Detectors
Complete this statement. “An ion striking the first dynode……..? 
a – releases more positive ions 
b – releases electrons 
c – triggers a small negative voltage to be applied to a grid located behind the dynode
d -  triggers a small positive voltage to be applied to a grid located behind the dynode


Q16. i) Doubly charged ions are commonly monitored by which element and why?  ii) Oxide interferences are commonly monitored by which element and why? 


Q17. The tripping point for the pulse to analog detector mode is around? 
a – 2 million CPS 
b – 2 million ppb 
c – 2 million ppm 
d – depends on the number of elements in the sample run

Briefly explain the concept behind pulse and analog modes? What is the purpose of having these two modes? 


Q18. Find a paper published in 2018 or 2019 that used ICP-MS. Describe briefly how the instrument was used? What was measured? And what was discovered? List the title, journal, year of publication and associated volume and page numbers.

 

Q19. Correctly name the two process (x & y) below:

a – (x) Coulombic Fission     (y) Solvent evaporation  
b – (x) MALDI ionization (y) Coulombic Fission
c – (x) Solvent evaporation   (y) Coulombic Fission 
d – (x) Solvent evaporation   (y) MALDI ionization   

Q20. Find a paper published in 2018 or 2019 that employed Triple Quadrupole Mass Spectrometry? Describe briefly how the instrument was used? What was measured? And what was discovered? List the title, journal, year of publication and associated volume and page numbers. 


Q21. Below is a schematic of a PMT detector. Label the following: 

 

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  • Posted on : December 09th, 2018
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