CHAPTER 1
Introduction
The main groups of substances that a chemist is likely to want to determine in solids
derived from water are metals and metalloids, non-metals (nitrogen, phosphorus,
sulphur etc), organometallic compounds and organic substances. The types of procedures used to determine each of these groups of substances in environmental sediment and living solid matter derived from water are discussed below under separate
headings.
1.1
Determination of Metals
Single acid digestions in open tubes include (i) dilute or concentrated hydrochloric acid
used to digest sediments, fish and crustacea preparatory to the determination of copper,
lead, cobalt, zinc, nickel, chromium, cobalt, manganese, iron, aluminium, silver and
cadmium by atomic absorption spectrometry or inductively coupled plasma atomic
emission spectrometry (ICP AES), and arsenic and selenium preparatory to hydrogen
generation atomic absorption spectrometry or inductivly coupled plasma atomic emission spectrometry, (ii) concentrated nitric acid digestion for the determination of the
same elements, and (iii) hydrofluoric acid for the digestion of samples preparatory to
the determination of elements such as cobalt, beryllium and chromium by atomic
absorption or ICP AES techniques.
An extension of the single acid digestion technique devised to complete digestions
of sediments, fish and crustacea in shorter times and perhaps more completely
includes (i) digestion with nitric acid under pressure and at an elevated temperature
in a microwave oven using a PTFE-lined bomb to determine copper, lead, cobalt, zinc,
nickel, chromium, cobalt, manganese, iron, aluminium, silver and cadmium or digestion with hydrochloric acid to determine calcium, iron, chromium, manganese, lead
and zinc, or (ii) autoclaving with concentrated nitric acid to determine iron, manganese, zinc, copper, chromium and lead.
A further method of speeding up the digestion of solid samples which has been
applied to sediments is to digest the sample with a mixture of mineral acids (nitric,
sulphuric, or hydrochloric acids) and hydrogen peroxide to determine chromium,
copper, zinc, cadmium, nickel, lead and mercury.
Aqua regia, or other mixtures of nitric and hydrochloric acids, is a powerful means
of breaking down sediments preparatory to the atomic absorption spectrometric
Introduction
The main groups of substances that a chemist is likely to want to determine in solids
derived from water are metals and metalloids, non-metals (nitrogen, phosphorus,
sulphur etc), organometallic compounds and organic substances. The types of procedures used to determine each of these groups of substances in environmental sediment and living solid matter derived from water are discussed below under separate
headings.
1.1
Determination of Metals
Single acid digestions in open tubes include (i) dilute or concentrated hydrochloric acid
used to digest sediments, fish and crustacea preparatory to the determination of copper,
lead, cobalt, zinc, nickel, chromium, cobalt, manganese, iron, aluminium, silver and
cadmium by atomic absorption spectrometry or inductively coupled plasma atomic
emission spectrometry (ICP AES), and arsenic and selenium preparatory to hydrogen
generation atomic absorption spectrometry or inductivly coupled plasma atomic emission spectrometry, (ii) concentrated nitric acid digestion for the determination of the
same elements, and (iii) hydrofluoric acid for the digestion of samples preparatory to
the determination of elements such as cobalt, beryllium and chromium by atomic
absorption or ICP AES techniques.
An extension of the single acid digestion technique devised to complete digestions
of sediments, fish and crustacea in shorter times and perhaps more completely
includes (i) digestion with nitric acid under pressure and at an elevated temperature
in a microwave oven using a PTFE-lined bomb to determine copper, lead, cobalt, zinc,
nickel, chromium, cobalt, manganese, iron, aluminium, silver and cadmium or digestion with hydrochloric acid to determine calcium, iron, chromium, manganese, lead
and zinc, or (ii) autoclaving with concentrated nitric acid to determine iron, manganese, zinc, copper, chromium and lead.
A further method of speeding up the digestion of solid samples which has been
applied to sediments is to digest the sample with a mixture of mineral acids (nitric,
sulphuric, or hydrochloric acids) and hydrogen peroxide to determine chromium,
copper, zinc, cadmium, nickel, lead and mercury.
Aqua regia, or other mixtures of nitric and hydrochloric acids, is a powerful means
of breaking down sediments preparatory to the atomic absorption spectrometric