AAS Microcredentials for UiTM Students

What is the fundamental principle underlying Atomic Absorption Spectroscopy (AAS)?

• Absorption of electromagnetic radiation by ground-state atoms

• Emission of photons by excited-state atoms

• Ionization of atoms in the sample solution

• Scattering of light by suspended particles in the sample

What component of an Atomic Absorption Spectrometer (AAS) is responsible for selecting the specific wavelength of light for analysis?

• Detector

• Sample introduction system

• Monochromator

• Lamp source

The following are the disadvantages of using an electrothermal atomizer in AAS, EXCEPT;

• Slow method

• Low precision

• Small sample volume is required

• Narrow analytical ranges

Select the appropriate description for the secondary combustion zone in the AAS flame.

• Thermal equilibrium is not achieved.

• The products of the inner core are converted into molecular oxides then dispersed into the surrounding.

• Made up by hydrocarbon fuel.

• The most widely used part of the flame because free atoms are prevalent.

The following are the processes that occur during atomization, EXCEPT;

• Nebulization

• Desolvation

• Volatilization

• Dehydration

Find the variable that influences the width of the atomic line spectra.

• Doppler effect

• Temperature effect

• Atomization effect

• Dissolution effect

Choose the appropriate sample introduction method for solution or slurry samples.

• Ultrasonic nebulization

• Electrothermal vaporization

• Pneumatic nebulization

• Hydride generation

The following are techniques that commonly used for decomposition and dissolution of samples during sample preparation, EXCEPT;

• Treatment with hot acid

• Combustion in oxygen bomb

• Microwave assisted acid digestion

• Low temperature fusion with reagents

At a maximum absorbance of 250 nm (with a molar absorptivity of 6500 M^-1 cm^-1) and a path length of 1 cm, the spectrophotometer records an absorbance of 0.95 for bisphenol-A. Determine the concentration of bisphenol-A.

• 1.46 × 10^-4

• 2.50 × 10^-5

• 3.1 × 10^-4

• 3.5 × 10^-4

Dr. Ahmad Husaini is tasked with determining the lead concentration in a water sample from a river near a metal piping factory. To analyze the sample via atomic absorbance spectroscopy (AAS), he prepares six samples (numbered 0-5) by adding 10.00 mL of river water to a 50.00 mL volumetric flask and then mixing in varying volumes of a 25.00 ppm lead solution, topping off each mixture to 50.00 mL with 0.1 M HNO₃. After conducting AAS analysis, a calibration curve of absorbance versus ppm of lead is derived, showing a best-fit line of y = 0.0428x + 0.0487. Determine the ppm of lead in the river water sample based on this information.

• 3.68 ppm lead

• 4.32 ppm lead

• 5.69 ppm lead

• 6.47 ppm lead