Environmental Trace Analysis: Techniques and Applications

By John R. Dean

This book covers all aspects of environmental trace analysis from sampling through to preparation of the sample to the analytical techniques used to quantify the level of trace metals or organic compounds. The book is divided into two areas: sample preparation for inorganic analysis and sample preparation for organic analysis. This allows the reader to focus on key aspects related to the preparation of samples for their subsequent analysis. Selected case studies provide the reader with the opportunity to consider how the sample preparation approach can be optimized for their own area of expertise.

• Language: English
• Publisher: Wiley
• Release date: Oct 10, 2013
• ISBN: 9781118682845

Book preview

About the Author

John R. Dean D.Sc., Ph.D., D.I.C., M.Sc., B.Sc., FRSC, C.Chem., CSci. Cert.Ed.

John R. Dean took his first degree in Chemistry at the University of Manchester Institute of Science and Technology (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 of Science and Technology, London. He then spent two 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. 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), Principal Lecturer (1998) and Associate Dean (Research) (2004). In 2004 he was appointed as Professor of Analytical and Environmental Science. Since 2008 he has held dual responsibility as Head of the Graduate School and Research Professor in the Department of Applied Sciences.

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 (RSC/AD) 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 been a member of the North East Region RSC/AD since 1992 serving as chairman (2001–03; 2013-present) and Honorary Secretary (2011 onwards). He has served on Analytical Division Council for four terms as well as being Vice-President (2002–04).

He is an active member of Tyne Valley Canoe Club and can be found most weekends on a river, lake or the sea. He has achieved BCU personal performance awards in white water kayaking (4 star leader), sea kayaking (4 star) and open canoe (5 star leader trainee). He holds BCU Level 3 coach status in white water kayaking and sea kayaking and is moderate water endorsed in open canoe. In addition, he is a UKCC Level 3 coach in white water kayaking and a UKCC Level 3 open canoe trainee.

Preface

The field of environmental trace analysis continues to develop and expand both in terms of its application and in the range of analytical techniques that are applied. While this book is not a direct update of a previous publication by the author (Methods for Environmental Trace Analysis, John R. Dean, AnTS, Wiley, 2003: ISBN 0-470-84421-3) it does build upon the knowledge presented. By taking a different style and format to the original text, by updating where appropriate and by adding new areas of investigation that have developed over the intervening 10 years a new text has emerged.

The book is arranged into 14 chapters covering the essentials of good laboratory housekeeping, making and recording practical results, principles of quantitative analysis, through to sampling protocols and sample storage. The book is sub-divided to allow the specific techniques that are used to prepare solid, liquid and, where appropriate, volatile samples for inorganic and organic analyses to be described. Emphasis is also placed on the use of pre-concentration techniques and clean-up procedures for organic samples. Chapter 12 focuses briefly on the wide range of analytical techniques that are applied to environmental trace elemental and organic analyses as well as a consideration of portable techniques for field measurements. Chapter 13 looks at some selected case studies used to highlight the application of the techniques in environmental trace analysis.

Finally, a special mention to all the students (past and present) who have helped to contribute to my interest in the field of environmental trace analysis. Our achievements have been many and varied across a broad area of environmental trace analysis – and mostly enjoyable!

John R. Dean

April 2013

Acknowledgements

Thank you to Lynne Dean for drawing Figures 4.2, 4.3, 4.4, 8.4, 12.11, 12.15(b), 12.16 and 13.8.

Thank you to Naomi Dean for drawing Figure 4.5.

Thank you to Dr Pinpong Kongchana for drawing Figures 8.2 and 8.7 as well as Figures in Box 6.1 illustrating conventional and microwave heating.

Thank you to Edwin Ludkin for drawing Figures 12.15a and 12.19.

Thank you to Thermo Fisher Scientific for permission to publish Figure 12.22; to Geotechnical Services for permission to publish Figure 12.23; to Spectral International, Inc. for permission to publish Figure 12.24; to InPhotonics, Inc. for permission to publish Figure 12.25; to RAE Systems for permission to publish Figure 12.26; and, to Smiths Detection for permission to publish Figure 12.27.

Thank you to Dr Jane Entwistle for Figure 13.1.

Thank you to Dr Nwabueze Elom for Figure 13.2.

Thank you to Dr Katherine Stapleton for Figures 13.3, 13.4 and 13.5.

Thank you to Dr Michael Deary for Figures 13.6 and 13.7.

Acronyms and Abbreviations

1

Basic Laboratory Procedures

1.1 Introduction

Environmental analysis does not start in the laboratory but outside (e.g. in a field, river, lake, urban environment or industrial atmosphere). Nevertheless it is important to develop a good understanding of the underlying principles of good laboratory practice and apply them from the start to the end of the process. In the case of an undergraduate laboratory class, for example, this would include:

Read the laboratory script in advance [Practical point: it is important to establish that you understand the requirements of the experiment and the skills required to perform the tasks].

Identify the appropriate level of safety required to undertake the experiment [Practical point: perform the appropriate risk assessment prior to starting the laboratory].

Listen and understand any verbal instructions given by the demonstrator/lecturer.

Organise your workspace [Practical point: keep your workspace clean, tidy and organised].

Record the exact laboratory procedure that you have carried out in your laboratory notebook.

Identify and record any issues with the experiment [Key point: what solutions to the issues have been tried?].

Record and interpret the results.

Understand the relevance of the results.

All the above can be applied and the process followed outside the laboratory, that is in the sampling, collection and storage of environmental samples. For the postgraduate student it is likely that the formal laboratory script does not exist and that you are actually developing the methods/procedures as your research develops. Your supervision team will, of course, be providing guidance on the actual direction and line of thought to follow (and certainly at the start of any research project).

This chapter and the following four chapters all provide invaluable information on the processes and procedures to be developed and understood, prior to undertaking any environmental analyses.

1.2 Health and Safety Issues

In the UK the Health and Safety at Work Act (1974) provides the main framework for health and safety, however, it is the Control of Substances Hazardous to Health (COSHH) regulations of 2002 that impose strict legal requirements for risk assessment wherever chemicals are used. Whereas in the European Union (EU) the system for controlling chemicals is the Registration, Evaluation, Authorisation and restriction of CHemicals (REACH). While in the USA the Environmental Protection Agency (EPA) is responsible for chemical safety relating to human health and the environment.

In all cases, however, it is important to understand the definitions applied to hazard and risk.

A hazardous substance is one that has the ability to cause harm.

Whereas risk is about the likelihood that the substance may cause harm.

On that basis the widespread approach to safe working practice (whether in or outside the laboratory) is to undertake a risk assessment. By undertaking a risk assessment you are aiming to establish:

The intrinsic chemical, physical or biological hazards associated with the substances to be used [Practical point: manufacturers of the substances provide data sheets identifying the hazards associated with the handling and use of their substances].

The impact on yourself and other workers by considering the possible exposure routes, for example inhalation, ingestion and dermal absorption; alongside the amount of the substance intended to be used.

The steps to be taken to prevent or control any exposure. This would include the choice of personal protective equipment, where the experiment would take place (fume cupboard or open bench) as well as the safe and appropriate disposal route.

The risk assessment must be recorded and the safety procedures and precautions passed on to those at risk and the person in charge.

The basic generic rules for laboratory work (and as appropriate for associated work outside the laboratory using chemicals) are as follows:

Always wear appropriate protective clothing; typically, this involves a clean laboratory coat fastened up, eye protection in the form of safety glasses or goggles, appropriate footwear (open toed sandals or similar are inappropriate) and ensure long hair is tied back. In some circumstances it may be necessary to put on gloves, for example when using concentrated acids.

Never eat or drink in the laboratory.¹

Never work alone in a laboratory.²

Make yourself familiar with fire regulations in your laboratory and building.

Be aware of accident/emergency procedures in your laboratory and building.

Use appropriate devices for transferring liquids [Practical point: never mouth pipette].

Only use/take the minimum quantity of chemical required for your work [Practical point: this can prevent cross-contamination as well as reducing the amount to be disposed of].

Use a fume cupboard for hazardous chemicals, for example volatile organic compounds and concentrated acids [Practical point: check that the fume cupboard is functioning properly (i.e. has an air flow that takes fumes away from the worker) before starting your work].

Clear up spillages and breakages as they occur; for example, in the undergraduate laboratory notify the demonstrator/technician immediately to ensure that appropriate disposal takes place, such as broken glass in the glass bin.

Always work in a logical and systematic manner; it saves time and can prevent a waste of resources, for example only weighing out the amount of chemical required when it is required.

Always think ahead and plan your work accordingly; this involves reading the laboratory script before you enter the laboratory as well as checking that you are following the script while undertaking the experiment.

1.3 Sample Handling: Solid Samples

The main vessels used for weighing out solids (e.g. soils and biological materials) in environmental analyses are weighing bottles, plastic weighing dishes or weighing boats. These containers are used to accurately weigh the solid using a four decimal place balance [Practical point: accurate weighing in a container involves weighing by difference, that is the container is weighed prior to addition of sample; the sample plus container are weighed, and finally the emptied container is weighed]. The analyte to be investigated will determine the specific sample preparation technique to be applied to the solid. For example, a solid sample for metal analysis will often require acid digestion (see Chapter 6); while for organic compounds it will require some form of solvent extraction (see Chapter 8). Once the solid has been either dissolved or extracted the resultant solution will need to be quantitatively transferred to a volumetric flask and made to the graduation mark, that is meniscus, with solvent (e.g. 1% v/v nitric acid or an organic solvent) [Practical point: volumetric flasks are accurate for their specified volume when the solution itself is at a particular temperature, e.g. 20 °C].

1.4 Sample Handling: Liquid Samples

The main vessels used for measuring out liquids (e.g. river or estuarine water) in environmental analyses are volumetric flasks, burettes, pipettes and syringes.

The composition of the vessel may be important in some instances [Practical point: some plasticisers are known to leach from plastic vessels especially in the presence of organic solvent e.g. dichloromethane; this is particularly important in organic analyses]. In inorganic analyses, contamination risk is evident from glass vessels that may not have been cleaned effectively; for example, metal ions can adsorb to glass and then leach into solution under acidic conditions thereby causing contamination [Practical point: this can be remedied by cleaning the glassware prior to use by soaking for 24 hours in 10% nitric acid solution, followed by rinsing with de-ionised water (three times)]. The cleaned vessels should then either be stored upside down or covered with Clingfilm® to prevent dust contamination.

1.5 Sample Handling: Gases/Vapour Samples

In the case of gaseous samples, it is essential to ensure that the sample is effectively trapped (e.g. on a sorbent) and retained until required to be analysed. Gaseous samples can be introduced on to a trap by using, for example, a pump to transfer the sample from one location to the trap. It is important to know the rate of transfer of the gaseous sample and duration to allow an estimate of the volume of air sampled.

1.6 Summary

This chapter has introduced the reader to the importance of good laboratory practice, health and safety requirements and specifically risk assessments, as well as given some introductory comments on the sample handling basics associated with solids, liquids and gases.

Notes

1. Smoking is banned in public buildings in the UK.

2. This is strictly enforced with undergraduate students; however, postgraduate researchers often work in the proximity of others to ensure some safety cover is available. Universities will have procedures in place to allow such work to take place and it will always involve notifying others of your name and location. In the case of postgraduate researchers, the proximity of a (mobile) telephone is additionally beneficial to alert others.

Further Reading

Dean, J.R., Jones, A.M., Holmes, D., Reed, R., Jones, A. and Weyers, J. (2011) Practical Skills in Chemistry, 2nd edn, Pearson, Harlow, UK.

2

Investigative Approach for Environmental Analysis

2.1 Introduction

The effective recording of all relevant data and information at the time of obtaining the scientific information is essential [Key point: part of the skill in environmental analyses is realising that the data/information is important at that point in time]. Therefore a systematic and appropriate method of recording all information accurately is essential.

2.2 Recording of Practical Results

All experimental observations and data should be recorded in an A4 notebook. An example would include: the geographical location of the samples, the total weight of each individual sample obtained, the pre-treatment the sample has undergone, the sample preparation technique used and its operating conditions/parameters, the analytical technique used to determine the results and how it was calibrated, the nature of the quality assurance used to ensure that the data is fit for purpose, and the recording of the results and their initial interpretation.

[Practical point: remember to record all information/data at the point of obtaining the information/data; it is easy to forget it later if not written down].

Important factors to remember when recording information in your notebook:

Record data correctly and legibly (even you may not be able to read your own writing later).

Write in ink (and not pencil which fades with age).

Include the date and title of individual experiments and/or areas of investigation.

Briefly outline