WorksheetsForensic Chemistry Instrumentation
Total questions: 30
Worksheet time: 30mins
Choose the INCORRECT terms in HPLC.
Elution is the process of washing substances through a chromatographic column with the mobile phase.
The mobile phase in chromatography is the one that moves over or through an immobilized phase in a column or on the surface of a plate.
The stationary phase in a chromatographic column is a solid that is fixed in place.
The retention time (tR) for an analyte is the time between t0 and the appearance of its peak as it elutes from the column.
The eluent in the chromatography is the fresh mobile phase that carries the sample through the column.
Regarding HPLC,
it is an analytical technique to separate identify or quantify each component in a volatile mixture.
the pump in HPLC should be able to provide a consistent pressure at any condition and a controllable and reproducible flow rate.
the separation in HPLC is performed on the detector used.
only UV-VIS detector can be used in.
the calibration curve is plotted as peak height versus concentration.
Regarding HPLC, the variables that lead to increased zone broadening include:
I. Large column diameter
II. Very high or very low flow rates
III. Low viscosity mobile phase
IV. Low introduction of sample onto column
I, II
I, II, IV
II, III, IV
I, II, III
I, II, III, IV
Regarding HPLC, the variable that improve band separation include:
I. decreased column length.
II. variation on mobile phase composition, including changes in pH.
III. choices of optimum temperature.
IV. Use of a stationary phase that selectively complexes certain analytes.
I, II
I, II, IV
II, III, IV
III, IV
I, II, III, IV
Regarding HPLC, the common reasons for retention time drift include:
I. HPLC column temperature fluctuations
II. Inadequate mobile phase degassing
III. System leaks or flow rate instability
IV. Column fouling
I, II
I, II, IV
II, III, IV
III, IV
I, II, III, IV
UV/visible wavelengths cover the region within
1200 to 1500 nm.
180-380 nm.
180-780 nm.
2500 to 50000 nm.
The complementary colour for orange is
red.
blue.
green.
yellow.
UV/Visible spectroscopy
is a qualitative method.
is similar to emission spectroscopy.
is a non-destructive method.
requires blank analysis.
Sample pre-treatments for UV/Visible spectroscopic analysis include
wet acid digestion.
ashing in furnace.
solvent dissolution.
KBr pellet preparation.
Regarding UV/Visible spectroscopy, colourless sample solution normally absorbs radiation within
180-380 nm.
380-500 nm.
500-700 nm.
700-800 nm.
Regarding atomic absorption spectroscopy (AAS), an “excited state” is
the highest energy state of an atom.
any level higher than the ground state.
the lowest energy state of an atom.
The level when an atom loss an electron.
The element which can be best analysed by AAS is
silicone.
nitrogen.
iron.
xenon.
Determine the type of result that can be produced by AAS.
Qualitative.
Quantitative.
Neither qualitative nor quantitative.
Both qualitative and quantitative.
The key advantage of Graphite Furnace AAS over Flame AAS is
lower detection limit.
allowing quantification of elements.
portable in nature.
providing faster response.
In a Flame AAS, the gas(es) required to ignite the flame are(is)
air + acetylene.
air + nitrogen.
air only.
nitrogen + nitrous oxide.
The following are gases used as mobile phases in Gas Chromatography, EXCEPT
helium.
oxygen.
hydrogen.
nitrogen.
The function of gas chromatography syringe is
to keep liquid and gas.
to transfer solution into vial.
to inject sample into the inlet.
to introduce the mobile phase into the GC system.
Temperature programming allows the _______ temperature to increase at a pre-set rate during the analysis of a sample.
detector.
oven.
column.
injector.
Chromatography is a
process by which particles move from a region of higher concentration to lower concentration.
process by which a mixture is purified.
method through which solutes are separated.
method through a mixture of solutions is separated.
A substance in the mixture that has the greatest affinity for the stationary phase will
travel fastest.
travel slowest.
give low retention time.
retain in the origin.
The output of a voltammetric analysis of an electroactive analyte is
Current time curve
Current potential curve
Charge time curve
Charge temperature curve
An experiment involves the scan of a range of potential voltages while measuring current.
Cyclic voltammetry
Electrode
Electrode potential
Electromotive force
Which of the following items is not the electrode in voltammetry?
Auxiliary electrode
Auxiliary electrode
Conducting electrode
Reference electrode
Which of the following voltammetric techniques enhances the sensitivity through improving the faradaic current?
Differential pulse voltammetry
Cyclic voltammetry
Square wave voltammetry
Stripping voltammetry
Polarography is a technique which deals with ______.
Polarization of light
saturated KCl solution
Dropping mercury electrode
carbon electrode
The name of the FTIR instrument used in the catch-up laboratory experiment.
Nimbus 2000
Lumos
Tensor-27
Shimadzu 350
The broad peak in IR spectrum between the region of 3300 cm-1 to 2500 cm-1 indicates the presence of
OH group
C=O group
CH3
N-H group
The range of FTIR spectrum when using ATR attachment.
4000 cm-1 to 400 cm-1
6000 cm-1 to 600 cm-1
6000 cm-1 to 200 cm-1
4000 cm-1 to 600 cm-1
The crystals that are commonly used for ATR attachment
Zinc selenide, germanium, diamond.
Zirconia selenide, titanium oxide, mercury telluride.
Platinum, gold plated germanium, sapphire.
Zinc sulphite, cadmium telluride, graphite oxide.
Choose the correct range of the following IR regions (in cm-1)
NIR (near IR): 2500 cm-1 to 4000 cm-1
MIR (mid IR): 4000 cm-1 to 400 cm-1
FIR (far IR): 400 cm-1 to 20 cm-1
