Sample Digestion

Question 1

what are the real samples subjected to

Answer 1

several pre-treatment
steps (sample wash and digestion) to make
them fit for analysis.

Question 2

sample washing is to

Answer 2

remove dirt and any

exogenous contamination.

Question 3

the washing treatment may involve several steps using

Answer 3

buffers (e.g. 0.1% Triton-X),
deionised water and/or organic solvents
(e.g. as acetone).

Question 4

what might the washing process be conducted under

Answer 4

mechanical or ultrasonic agitation

Question 5

what is the digestion process

Answer 5

the conversion of
a solid matrix into a liquid matrix, i.e. the solid
sample is decomposed.

Question 6

what is the best common approach to digestion

Answer 6

use mineral acids and heat

• alternatively dry washing and fusion can be employed

Question 7

acid digestion involves

Answer 7

the use of mineral or oxidising acids and an external heat source

Question 8

what does the choice of acid depend on in acid digestion

Answer 8

the nature of the matrix to be decomposed

Question 9

what is a major problem when preparing solid samples for trace element analysis

Answer 9

the risk of contamination

Question 10

how can contamination arise

Answer 10

the grade reagents
the vessel
human involvement

Question 11

how to minimise the risk of contamination

Answer 11

• use highest purity reagents and acids including water
• use sample blanks in the analytical procedures
• soak overnight sample vessels in an acid leaching bath (10 % v/v nitric acid)
• store clean glassware (protected from dust)
• use clean and all necessary laboratory wearing.