Practical Inductively Coupled Plasma Spectroscopy - Softcover

Dean, John R.

Softcover

ISBN 10: 0470093498 ISBN 13: 9780470093498

Publisher: Wiley, 2005

Synopsis

The book provides an up-to-date account of inductively coupled plasmas and their use in atomic emission spectroscopy and mass spectrometry. Specific applications of the use of these techniques are highlighted including applications in environmental, food and industrial analysis. It is written in a distance learning / open learning style; suitable for self study applications. It contains contain self-assessment and discussion questions, worked examples and case studies that  allow the reader to test their understanding of the presented material.

About this title

About the Author

John R. Dean took his first degree in Chemistry at UMIST, followed by an M.Sc. in Analytical Chemistry and Instrumentation at Loughborough University of Technology and finally a Ph.D. and D.I.C. in Physical Chemistry at Imperial College. He then spent 2 years as a postdoctoral research fellow at the Food Science Laboratory of the Ministry of Agriculture, Fisheries and Food in Norwich in conjunction with Polytechnic South West in Plymouth. The work was focused on the development of directly coupled high performance liquid chromatography inductively coupled plasma mass spectrometry methods for trace element speciation in foodstuffs. This was followed by a temporary lectureship in Inorganic Chemistry at Huddersfield Polytechnic. In 1988 he was appointed to a lectureship in Inorganic/Analytical Chemistry at Newcastle Polytechnic (now Northumbria University). This was followed by promotion to Senior Lecturer (1990), Reader (1994) and Principal Lecturer (1998). In 1998 he was awarded a D.Sc. (London) in Analytical and Environmental Science and was the recipient of the 23rd SAC Silver Medal in 1995. He has published extensively in analytical and environmental science. He is an active member of the Royal Society of Chemistry Analytical Division having served as a member of the atomic spectroscopy group for 15 years (10 as honorary secretary) as well as a past chairman (1997-99). He has served on Analytical Division council for three terms and is currently its vice-president (2002-04) as well as chairman of the North East Region (2001-03).

From the Back Cover

This text provides a valuable and readily accessible, practical introduction to inductively coupled plasma spectroscopy, serving both as a basic textbook for taught courses and also as a ‘self-study’ resource for those pursuing ‘open learning/distance learning’ forms of study.

Topics covered within this essential text include:

• Methodology for trace elemental analysis
• Sample preparation techniques for inductively coupled plasma spectroscopy, including those used for aqueous and solid samples, plus details of the various extraction procedures that can be used to prepare samples
• Sample introduction procedures for plasma sources
• The inductively coupled plasma and other sources used for atomic emission spectroscopy and mass spectrometry
• Fundamental aspects of atomic emission spectroscopy and mass spectrometry
• Spectrometers and detectors used for plasma spectroscopy
• Interferences in atomic emission spectroscopy
• Principles of inductively coupled plasma–mass spectrometry (ICP–MS)
• Types of mass spectrometers used for ICP–MS
• Interferences in ICP–MS and their remedies, including collision/reaction cells
• Isotope dilution analysis
• A range of applications for this technique, including forensic science, industrial analysis, clinical/biological analysis, materials analysis, environmental analysis, food analysis and pharmaceutical analysis
• Sample data sheets that can be used to record information in the laboratory
• A comprehensive bibliography, providing information on how to keep up-to-date with the latest developments in this field, guiding the reader to more specialized texts and sources, including books, journals and recommended web sites

Practical Inductively Coupled Plasma Spectroscopy will be invaluable to those students studying at Foundation and BTEC (HNC and HND) levels, and for those pursuing BSc, MChem, MSc and MRes courses in analytical chemistry, as well as subsidiary courses in life, environmental and food science. In addition, it will be a useful guide to those using ICP, and related techniques, in applied research and analysis.

Topics covered within this essential text include:

• Methodology for trace elemental analysis
• Sample preparation techniques for inductively coupled plasma spectroscopy, including those used for aqueous and solid samples, plus details of the various extraction procedures that can be used to prepare samples
• Sample introduction procedures for plasma sources
• The inductively coupled plasma and other sources used for atomic emission spectroscopy and mass spectrometry
• Fundamental aspects of atomic emission spectroscopy and mass spectrometry
• Spectrometers and detectors used for plasma spectroscopy
• Interferences in atomic emission spectroscopy
• Principles of inductively coupled plasma–mass spectrometry (ICP–MS)
• Types of mass spectrometers used for ICP–MS
• Interferences in ICP–MS and their remedies, including collision/reaction cells
• Isotope dilution analysis
• A range of applications for this technique, including forensic science, industrial analysis, clinical/biological analysis, materials analysis, environmental analysis, food analysis and pharmaceutical analysis
• Sample data sheets that can be used to record information in the laboratory
• A comprehensive bibliography, providing information on how to keep up-to-date with the latest developments in this field, guiding the reader to more specialized texts and sources, including books, journals and recommended  web sites

Practical Inductively Coupled Plasma Spectroscopy will be invaluable to those students studying at Foundation and BTEC (HNC and HND) levels, and for those pursuing BSc, MChem, MSc and MRes courses in analytical chemistry, as well as subsidiary courses in life, environmental and food science. In addition, it will be a useful guide to those using ICP, and related techniques, in applied research and analysis.

Excerpt. © Reprinted by permission. All rights reserved.

Practical Inductively Coupled Plasma Spectroscopy

By John R. Dean

John Wiley & Sons

Copyright © 2005 John R. Dean
All right reserved.
ISBN: 9780470093498

Chapter One

Methodology for Trace Elemental Analysis

Learning Objectives

To be aware of the different types of contamination that can cause problems in trace elemental analysis.

To be aware of a whole range of terms and definitions as used in analytical chemistry.

To appreciate the range of units used in analytical chemistry.

To be able to present numerical data with correct units, and be able to interchange the units as required.

To be able to present data in the form of a table.

To be able to present data in the form of a graph.

To be able to determine the concentration of an element from a straight line graph using the equation y = mx + c.

To be able to calculate the dilution factor for a liquid sample and a solid sample, and hence determine the concentration of the element in the original sample.

To appreciate the concept of quality assurance in the analytical laboratory.

To be aware of the significance of certified reference materials in elemental analysis.

1.1 Introduction

Trace elemental analysis requires more than just knowledge of the analytical technique to be used - in this case, inductively coupled plasma spectroscopy. This requires knowledge of a whole range of disciplines that need to come together to create the final result. The disciplines required can be described as follows:

sampling, sample storage and preservation, and sample preparation methodologies

analytical technique

data control, including calibration strategies and the use of certified reference materials for quality control

data management, including reporting of results and their meaning

While most of these are covered to some extent in this book, the reader should also consult other resources, e.g. books. Suggestions for further study are given in Chapter 8.

The perspective that is required when faced with trace element analysis are the additional precautions required in terms of management of contamination, choice of reagents and acids, and cleanliness of the workspace. For example, the grade of chemical used to prepare calibration standards is a major concern when working at trace element analysis levels (sub-?g [ml.sup.-1]). Chemicals are available in a range of grades from 'GPR - general purpose reagent' through to, for example, 'AnalaRR - analytical reagent'. However, the descriptor does not identify that the chemical is any purer (the purity is often given on the bottle, e.g. 99.8%), but identifies the amount of effort that the manufacturer has gone to in the preparation of the chemical. For 'AnalaRR' grade materials, the manufacturer has characterized the chemical by subjecting it to chemical analysis. This additional effort is then passed on to the customer in the form of a higher price. The use of sample blanks in the analytical procedure is essential to identify 'problem elements'.

The risk of contamination is a major problem in trace element analysis. Apart from the analytical reagent used to prepare standards, as discussed above, contamination can also be experienced from sample containers, e.g. volumetric flasks, pipettes, etc. For example, metal ions can adsorb onto glass containers and then leach into the solution under acidic conditions, thereby causing contamination. This can be minimized by cleaning the glassware prior to use by soaking for at least 24 h in a 10% nitric acid solution, followed by rinsing with 'clean' deionized water (three times).

DQ 1.1 What type of water would you consider to be clean?

Answer

Drinking water, commercially bottled drinking water or laboratory distilled water. The actual answer depends to some extent on the work to be carried out. For trace element analysis, it is possible to purchase commercial systems that filter (distilled) water through a combination of ion-exchange columns to remove trace element impurities.

The cleaned vessels should then either be stored upside down or covered with ClingfilmR to prevent dust contamination.

The individual working in the laboratory is also a major source of contamination. Therefore, as well as the normal laboratory safety associated with wearing a laboratory coat and safety glasses, it may be necessary to take additional steps such as the wearing of 'contaminant-free' gloves and a close-fitting hat.

1.2 Analytical Terms and their Definitions

The following is an alphabetical list of the most important analytical terms of use in practical inductively coupled plasma spectroscopy.

Accuracy A quantity referring to the difference between the mean of a set of results or an individual result and the value which is accepted as the true or correct value for the quantity being measured.

Acid digestion Use of acid (and often heat) to destroy the organic matrix of a sample to liberate the metal content.

Aliquot A known amount of a homogenous material assumed to be taken with negligible sampling error.

Analyte The component of a sample which is ultimately determined directly or indirectly.

Bias Characterizes the systematic error in a given analytical procedure and is the (positive or negative) deviation of the mean analytical result from the (known or assumed) true value.

Calibration The set of operations which establish, under specified conditions, the relationship between values indicated by a measuring instrument or measuring system and the corresponding known values of the measurand.

Calibration curve Graphical representation of a measuring signal as a function of quantity of analyte.

Certified Reference Material (CRM) Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realization of the units in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence.

Complexing agent The chemical species (an ion or a compound) which will bond to a metal ion using lone pairs of electrons.

Confidence interval Range of values that contains the true value at a given level of probability. The latter is known as the confidence level.

Confidence limit The extreme values or 'end-values' in a confidence interval.

Contamination In trace analysis this is the unintentional introduction of analyte(s) or other species which are not present in the original sample and which may cause an error in the determination. This can occur at any stage in the analysis. Quality assurance procedures, such as analyses of blanks or of reference materials, are used to check for contamination problems.

Control of Substances Hazardous to Health (COSHH) Regulations that impose specific legal requirements for risk assessment wherever hazardous chemicals or biological agents are used.

Co-precipitation The inclusion of otherwise soluble ions during the precipitation of lower-solubility species.

Dilution factor The mathematical factor applied to the determined value (data obtained from a calibration graph) which allows the concentration in the original sample to be determined. Frequently, for solid samples, this will involve a sample weight and a volume to which the digested/extracted sample is made up to prior to analysis. For liquid samples, this will involve an initial sample volume and a volume to which the digested/extracted sample is made up to prior to analysis.

Dissolved Material that will pass through a 0.45?m membrane filter assembly prior to sample acidification.

Dry ashing Use of heat to destroy the organic matrix of a sample to liberate the metal content.

Error The error of an analytical result is the difference between the result and a 'true' value:

Random error Result of a measurement minus the mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions.

Systematic error Mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions, minus the true value of the measurand.

Extraction The removal of a soluble material from a solid mixture by means of a solvent or the removal of one or more components from a liquid mixture by use of a solvent with which the liquid is immiscible or nearly so.

Figure of merit A parameter that describes the quality of performance of an instrument or an analytical procedure.

'Fitness for purpose' The degree to which data produced by a measurement process enables a user to make technically and administratively correct decisions for a stated purpose.

Heterogeneity The degree to which a property or a constituent is randomly distributed throughout a quantity of material. The degree of heterogeneity is the determining factor of sampling error.

Homogeneity The degree to which a property or a constituent is uniformly distributed throughout a quantity of material. A material may be homogenous with respect to one analyte but heterogeneous with respect to another.

Interferent Any component of the sample affecting the final measurement.

Limit of detection The detection limit of an individual analytical procedure is the lowest amount of an analyte in a sample which can be detected but not necessarily quantified as an exact value. The limit of detection, expressed as either the concentration [c.sub.L] or the quantity [q.sub.L], is derived from the smallest measure, [x.sub.L], that can be detected with reasonable certainty for a given procedure. The value [x.sub.L] is given by the following equation:

[x.sub.L] = [x.sub.bl] + [ks.sub.bl]

where [x.sub.bl] is the mean of the blank measures, [s.sub.bl] is the standard deviation of the blank measures and k is a numerical factor chosen according to the confidence level required. For many purposes, the limit of detection is taken to be [3s.sub.bl] or 3 x 'the signal-to-noise ratio', assuming a zero blank.

Limit of quantitation For an individual analytical procedure, this is the lowest amount of an analyte in a sample which can be quantitatively determined with suitable uncertainty. It may also be referred to as the limit of determination. The limit of quantitation can be taken as 10 x 'the signal-to-noise ratio', assuming a zero blank.

Linear dynamic range (LDR) The concentration range over which the analytical working calibration curve remains linear.

Linearity This defines the ability of the method to obtain test results proportional to the concentration of analyte.

Liquid-liquid extraction A method of extracting a desired component from a liquid mixture by bringing the solution into contact with a second liquid, the solvent, in which the component is also soluble, and which is immiscible with the first liquid or nearly so.

Matrix The carrier of the test component (analyte), all of the constituents of the material except the analyte, or the material with as low a concentration of the analyte as it is possible to obtain.

Measurand A particular quantity subject to measurement.

Method The overall, systematic procedure required to undertaken an analysis. This includes all stages of the analysis, and not just the (instrumental) end determination.

Microwave digestion A method of digesting an organic matrix to liberate metal content by using an acid at elevated temperature (and pressure) based on microwave radiation. Can be carried out in either open or sealed vessels.

Organometallic An organic compound in which a metal is covalently bonded to carbon.

Outlier This may be defined as an observation in a set of data that appears to be inconsistent with the remainder of that set.

Precision The closeness of agreement between independent test results obtained under stipulated conditions.

Qualitative analysis Chemical analysis designed to identify the components of a substance or mixture.

Quality assurance All those planned and systematic actions necessary to provide adequate confidence that a product or services will satisfy given requirements for quality.

Quality control The operational techniques and activities that are used to fulfill requirements of quality.

Quality control chart A graphical record of the monitoring of control samples which helps to determine the reliability of the results.

Quantitative analysis This is normally taken to mean the numerical measurement of one or more analytes to the required level of confidence.

Reagent A test substance that is added to a system in order to bring about a reaction or to see whether a reaction occurs (e.g. an analytical reagent).

Reagent blank A solution obtained by carrying out all steps of the analytical procedure in the absence of a sample.

Recovery The fraction of the total quantity of a substance recoverable following a chemical procedure.

Reference material This is a material or substance, one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials.

Repeatability Precision under repeatability conditions, i.e. conditions where independent test results are obtained with the same method on identical test items in the same laboratory, by the same operator, using the same equipment within short intervals of time.

Reproducibility Precision under reproducibility conditions, i.e. conditions where test results are obtained with the same method on identical test items in different laboratories, with different operators, using different equipment. Robustness For an analytical procedure, this is a measure of its capacity to remain unaffected by small, but deliberate variations in method parameters, and provides an indication of its reliability during normal usage. It is sometimes referred to as ruggedness.

Sample A portion of material selected from a larger quantity of material. The term needs to be qualified, e.g. representative sample, sub-sample, etc.

Selectivity (in analysis) Qualitative - the extent to which other substances interfere with the determination of a substance according to a given procedure. Quantitative - a term used in conjunction with another substantive (e.g. constant, coefficient, index, factor, number, etc.) for the quantitative characterization of interferences.

Signal-to-noise ratio A measure of the relative influence of noise on a control signal. Usually taken as the magnitude of the signal divided by the standard deviation of the background signal.

Solvent extraction The removal of a soluble material from a solid mixture by means of a solvent or the removal of one or more components from a liquid mixture by use of a solvent with which the liquid is immiscible or nearly so.

Speciation The process of identifying and quantifying the different defined species, forms or phases present in a material or the description of the amounts and types of these species, forms or phases present.

Standard (all types) A standard is an entity established by consensus and approved by a recognized body. It may refer to a material or solution (e.g. an organic compound of known purity or an aqueous solution of a metal of agreed concentration) or a document (e.g. a methodology for an analysis or a quality system). The relevant terms are as follows:

Analytical standard (also known as Standard solution) A solution or matrix containing the analyte which will be used to check the performance of the method/instrument.

Calibration standard The solution or matrix containing the analyte (measurand) at a known value with which to establish a corresponding response from the method/instrument.

External standard A measurand, usually identical with the analyte, analysed separately from the sample.

Internal standard A measurand, similar to but not identical with the analyte, which is combined with the sample.

Standard method A procedure for carrying out a chemical analysis which has been documented and approved by a recognized body.

Standard addition The addition of a known amount of analyte to the sample in order to determine the relative response of the detector to an analyte within the sample matrix. The relative response is then used to assess the sample analyte concentration.

Stock solution This is generally a standard or reagent solution of known accepted stability, which has been prepared in relatively large amounts of which portions are used as required. Frequently, such portions are used following further dilution.

Sub-sample This may be either (a) a portion of the sample obtained by selection or division, (b) an individual unit of the lot taken as part of the sample, or (c) the final unit of multi-stage sampling. True value A value consistent with the definition of a given particular quantity.

Uncertainty A parameter associated with the result of a measurement which characterizes the dispersion of the values that could reasonably be attributed to the measurand.

Continues...

Excerpted from Practical Inductively Coupled Plasma Spectroscopyby John R. Dean Copyright © 2005 by John R. Dean. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Edition details

• Publisher: Wiley
• Publication date: 2005
• ISBN 10: 0470093498
• ISBN 13: 9780470093498
• Binding: Paperback
• Language: English
• Edition number: 1
• Number of pages: 208