Page 34 - Vogel's TEXTBOOK OF QUANTITATIVE CHEMICAL ANALYSIS

1 INTRODUCTION
With the development of increasingly sophisticated analytical techniques it has
become possible to determine substances present in quantities much lower than
the 0.01 per cent upper level set for trace constituents. It is therefore necessary to
make further subdivisions: trace corresponds to 10'-104 .~g per gram, or
IO2-104 parts per million (ppm), microtrace to 10'-IO-' pg per gram,
(10-4-10-7 ppm), nanotrace to 10'-IO-' fm per gram (10-7-10-'0 PP~).
When the sample weight is small (0.1-1.0 mg), the determination of a trace
component at the 0.01 per cent level rnay be referred to as subtrace analysis. If the
trace component is at the microtrace level, the analysis is termed sub-
microtrace. With a still smaller sample (not larger than 0.1 mg) the determination
of a component at the trace level is referred to as ultratrace analysis, whilst
with a component at the microtrace level, the analysis is referred to as
ultra-microtrace.
The purpose for which the analytical data are required rnay perhaps be
related to process control and quality control. In such circumstances the
objective is checking that raw materials and finished products conform to
specification, and it rnay also be concerned with monitoring various stages in
a manufacturing process. For this kind of determination methods must be
employed which are quick and which can be readily adapted for routine work:
in this area instrumental methods have an important role to play, and in certain
cases rnay lend themselves to automation. On the other hand, the problem rnay
be one which requires detailed consideration and which rnay be regarded as
being more in the nature of a research topic.

1.5 USE OF LITERATURE
Faced with a research-style problem, the analyst will frequently be dealing with
a situation which is outside his normal experience and it will be necessary to
seek guidance from published data. This will involve consultation of multi-
volume reference works such as Kolthoff and Elving, Treatise on Analytical
Chemistry; Wilson and Wilson, Comprehensioe Analytical Chemistry; Fresenius
and Jander, Handbuch der analytischen Chemie; of a compendium of methods
such as Meites, Handbook of Analytical Chemistry; or of specialised monographs
dealing with particular techniques or types of material. Details of recognised
procedures for the analysis of many materials are published by various officia1
bodies, as for example the American Society for Testing Materials (ASTM), the
British Standards Institution and the Commission of European Communities.
It rnay be necessary to seek more up-to-date information than that available
in the books which have been consulted and this will necessitate making use
of review publications (e.g. Annual Reports of the Chemical Society; reviews in
The Analyst and Analytical Chemistry), and of abstracts (e.g. Analytical
Abstracts; Chemical Abstracts), and referring to journals devoted to analytical
chemistry and to specific techniques: see Section 1.7.*
Such a literature survey rnay lead to the compilation of a list of possible
procedures and the ultimate selection must then be made in the light of the
criteria previously enunciated, and with special consideration being given to
questions of possible interferences and to the equipment available.

* Selected Bibliographies and References are given at the end of each part of the book; for Part A,
see Sections 3.38 and 3.39.