topic 4 atomic absorption spectroscopy

what is atomic absorption spectroscopy?

a technique used to determine the concentration of inorganic elements in samples

what kind of analysis is AAS?

quantitative analysis

why do we need to perform sample preparation?

remove organic components present in the sample

what is wet ashing? (2)

uses strong acid and heat to destroy the organic matter

only inorganic elements will remain in the acid solution

what is dry ashing? (4)

involves heating of the sample in a electrical furnace

destroys organic compound by oxidation

inorganic elements will remain in the ash

ash is dissolved in acid to form a solution for analysis

what are the interferences in AAS?

matrix chemical ionization

what is the matrix interference/effect?

differences in physical and chemical characteristics of the standard and sample solutions

how to minimize matrix effect? (3)

ensure same matrix for standard and sample solutions

ensure that the sample and standard are the same temperature

employs the standard addition method

what is chemical interference?

formation of stable compounds

absorbance decrease

ways to minimize chemical interference? (3)

use a higher flame temperature

use releasing agents

use protective agents (EDTA)

what is ionization interference?

removal of electron from the atoms as a result of high flame temperature

absorbance will decrease

ways to minimize ionization interference? (2)

add easily ionizable elements (sodium potassium)

use a lower flame temperature

what could be the interference of overestimated result in AAS?

matrix effect