INSTRUMENTAL ANALYSIS ACS EXAMINATION SCRIPT 2025/2026
QUESTIONS AND ANSWERS GUARANTEE A+
✔✔how to find the detection limit for method? - ✔✔3.3*SD(blank)/calibration sensitivity
✔✔voltage in a series - ✔✔Vt = Vc + Vb + Va
✔✔Voltage in a parallel circuit - ✔✔1/Veff = 1/Va + 1/Vb
✔✔Capacitance in a series - ✔✔1/Ceff = 1/Ca + 1/Cb
✔✔capacitance equals - ✔✔Q/V
✔✔if a spectrum is the result of a single scan while another is the result of multiple
scans, how man individual spectra were summed to increase S/N from 4.2 to 43?
a) formula?
b) answer - ✔✔a) (S/N)a = sqrt(n) (S/N)b
b) 105
✔✔what type of noise can be reduced by decreasing the temperature of a
measurement - ✔✔thermal noise
✔✔what type of noise can be reduced by decreasing the frequency used for the
measurement - ✔✔flicker noise
✔✔what type of noise can be reduced by decreasing the bandwidth of the
measurement - ✔✔environmental noise
✔✔What would be an appropriate source and detector to determine the emission lines
for lithium from 200 to 780 nm? - ✔✔flame and photo multiplier tube (PMT)
✔✔you've been asked to measure the UV absorbance of a sample containing poly
cyclic aromatic hydrocarbons, a byproduct of the incomplete combustion of organic
matter. What would be an appropriate material for the sample container? - ✔✔fused
silica or quartz
✔✔which of the following changes will result in a decreased effective bandwidth?
a) increasing the number of blazes in the monochromatic grating
b) switching from a short-pass filter to a long-pass filter
c) increasing sample concentration
d) decreasing the amount of stray light - ✔✔a
,✔✔what would be the distance between blazes for a grating where the first order
diffraction line for 600 nm light is reflected at 10 degrees and the angle of incidence light
is 45 degrees?
a) formula
b) answer - ✔✔a) n(wavelength) = distance*(sin(i)+sin(r))
b) 680 nm
✔✔which of the following would be considered a discontinuous wavelength selector?
a) quartz prism
b) Czerny-Turner Grating (monochormator)
c)interference filter
d)glass prism - ✔✔c
✔✔which characteristics are desirable for a radiation transducer?
a) high sensitivity to short wavelength light
b) low S/N ratio
c) consistent high output when not illuminated
d) constant response over large wavelength range
e) all of the above - ✔✔d
✔✔what is the appropriate process for atomization for AAS and AES? (3 steps) -
✔✔desolvation, vaporization, atomization
✔✔the doppler effect is one reason for line broadening in atomic spectroscopy. What is
the effect on a measured signal? - ✔✔movement of excited atoms toward the detector
causes a shortening in the wavelength of the emitted light
✔✔it is better to select an excitation source for AAS with ____bandwidth - ✔✔smaller
✔✔what is the general layout for AES? - ✔✔sample --> source --> wavelength selector -
-> detector
✔✔a)name the electrical signals that are considered analog?
b) how is the information encoded in an analog signal? - ✔✔a) current, voltage, charge,
and power
b) an analog signal is a signal where the amplitude of the signal changes with time, so
the information is encoded either through the amplitude or frequency of the signal (and
the signal can be wavelength, magnetic field strength, T,etc)
✔✔what is a figure of merit? - ✔✔it is a numerical value characterizing the quantitative
instrument performance and include precision, bias, sensitivity, detection limit, dynamic
range and selectivity
, ✔✔How long would it take to discharge a 0.015 microF capacitor to 1% of its full charge
through a resistance of 10 mega Ohms?
a) formula
b) answer - ✔✔a) vc= Vc e^(-t/RC)
b) t = 0.69 seconds
✔✔select the type of ionization technique used in MS that would result in significant
fragmentation
a) MALDI
b) electron impact
c) high performance
d) chemical ionization - ✔✔c
✔✔which is true for chemical ionization?
a) considered a "hard ionization" technique
b) analyte reacts with electron beam
c) compared to other ionization techniques, less fragmentation occurs
d)compared to other ionization techniques, results in the most repeatable small
fragments - ✔✔c
✔✔true or false
formation of ions in electrospray occurs by spraying the sample through a capillary,
where it is exposed to a high voltage source, then charged sample undergoes
desolvation. Once the Rayleigh limit is achieved, coulombic repulsions overcome any
surface tension of the liquid resulting in small, multiply charged species - ✔✔true
✔✔which of the following detectors would be appropriate for measuring the Raman
Spectra for samples irradiated with 455 nm light?
a)thermocouple
b)bolometer
c)photographic plate
d)charge-coupled device array (CCD) - ✔✔D
✔✔which of the following detectors would be appropriate for measuring the IR spectra?
a) CCD array
b) photographic plate
c) photomultiplier tube
d) pyroelectric detector - ✔✔d
✔✔which of the following sources would be appropriate excitation source for collecting
IR spectra?
a) hollow cathode tube
b) nernst glower
c) Xenon lamp
QUESTIONS AND ANSWERS GUARANTEE A+
✔✔how to find the detection limit for method? - ✔✔3.3*SD(blank)/calibration sensitivity
✔✔voltage in a series - ✔✔Vt = Vc + Vb + Va
✔✔Voltage in a parallel circuit - ✔✔1/Veff = 1/Va + 1/Vb
✔✔Capacitance in a series - ✔✔1/Ceff = 1/Ca + 1/Cb
✔✔capacitance equals - ✔✔Q/V
✔✔if a spectrum is the result of a single scan while another is the result of multiple
scans, how man individual spectra were summed to increase S/N from 4.2 to 43?
a) formula?
b) answer - ✔✔a) (S/N)a = sqrt(n) (S/N)b
b) 105
✔✔what type of noise can be reduced by decreasing the temperature of a
measurement - ✔✔thermal noise
✔✔what type of noise can be reduced by decreasing the frequency used for the
measurement - ✔✔flicker noise
✔✔what type of noise can be reduced by decreasing the bandwidth of the
measurement - ✔✔environmental noise
✔✔What would be an appropriate source and detector to determine the emission lines
for lithium from 200 to 780 nm? - ✔✔flame and photo multiplier tube (PMT)
✔✔you've been asked to measure the UV absorbance of a sample containing poly
cyclic aromatic hydrocarbons, a byproduct of the incomplete combustion of organic
matter. What would be an appropriate material for the sample container? - ✔✔fused
silica or quartz
✔✔which of the following changes will result in a decreased effective bandwidth?
a) increasing the number of blazes in the monochromatic grating
b) switching from a short-pass filter to a long-pass filter
c) increasing sample concentration
d) decreasing the amount of stray light - ✔✔a
,✔✔what would be the distance between blazes for a grating where the first order
diffraction line for 600 nm light is reflected at 10 degrees and the angle of incidence light
is 45 degrees?
a) formula
b) answer - ✔✔a) n(wavelength) = distance*(sin(i)+sin(r))
b) 680 nm
✔✔which of the following would be considered a discontinuous wavelength selector?
a) quartz prism
b) Czerny-Turner Grating (monochormator)
c)interference filter
d)glass prism - ✔✔c
✔✔which characteristics are desirable for a radiation transducer?
a) high sensitivity to short wavelength light
b) low S/N ratio
c) consistent high output when not illuminated
d) constant response over large wavelength range
e) all of the above - ✔✔d
✔✔what is the appropriate process for atomization for AAS and AES? (3 steps) -
✔✔desolvation, vaporization, atomization
✔✔the doppler effect is one reason for line broadening in atomic spectroscopy. What is
the effect on a measured signal? - ✔✔movement of excited atoms toward the detector
causes a shortening in the wavelength of the emitted light
✔✔it is better to select an excitation source for AAS with ____bandwidth - ✔✔smaller
✔✔what is the general layout for AES? - ✔✔sample --> source --> wavelength selector -
-> detector
✔✔a)name the electrical signals that are considered analog?
b) how is the information encoded in an analog signal? - ✔✔a) current, voltage, charge,
and power
b) an analog signal is a signal where the amplitude of the signal changes with time, so
the information is encoded either through the amplitude or frequency of the signal (and
the signal can be wavelength, magnetic field strength, T,etc)
✔✔what is a figure of merit? - ✔✔it is a numerical value characterizing the quantitative
instrument performance and include precision, bias, sensitivity, detection limit, dynamic
range and selectivity
, ✔✔How long would it take to discharge a 0.015 microF capacitor to 1% of its full charge
through a resistance of 10 mega Ohms?
a) formula
b) answer - ✔✔a) vc= Vc e^(-t/RC)
b) t = 0.69 seconds
✔✔select the type of ionization technique used in MS that would result in significant
fragmentation
a) MALDI
b) electron impact
c) high performance
d) chemical ionization - ✔✔c
✔✔which is true for chemical ionization?
a) considered a "hard ionization" technique
b) analyte reacts with electron beam
c) compared to other ionization techniques, less fragmentation occurs
d)compared to other ionization techniques, results in the most repeatable small
fragments - ✔✔c
✔✔true or false
formation of ions in electrospray occurs by spraying the sample through a capillary,
where it is exposed to a high voltage source, then charged sample undergoes
desolvation. Once the Rayleigh limit is achieved, coulombic repulsions overcome any
surface tension of the liquid resulting in small, multiply charged species - ✔✔true
✔✔which of the following detectors would be appropriate for measuring the Raman
Spectra for samples irradiated with 455 nm light?
a)thermocouple
b)bolometer
c)photographic plate
d)charge-coupled device array (CCD) - ✔✔D
✔✔which of the following detectors would be appropriate for measuring the IR spectra?
a) CCD array
b) photographic plate
c) photomultiplier tube
d) pyroelectric detector - ✔✔d
✔✔which of the following sources would be appropriate excitation source for collecting
IR spectra?
a) hollow cathode tube
b) nernst glower
c) Xenon lamp
