To p or not to p: the use of p-values in analytical science
This article explains what a p-value is and the pros and cons of using them. Concluding that they are a useful method of interpreting data.
The edge of reason: reporting and inference near the detection limit
This Technical Brief describes the principal internationally recognised approach to decision and detection limits.
Laser-induced breakdown spectroscopy (LIBS) in cultural heritage
This Technical Brief describes the basic concepts of laser-induced breakdown spectroscopy, presents relevant aspects of instrumentation and discusses how the technique is applied in the context of cultural heritage studies.
The role of accreditation in ensuring sampling quality
This Technical Brief explains how accreditation and certification of sampling is already in place in certain application sectors, and the potential benefits it can bring as it is applied to new sectors. Accreditations provides the framework within which both samplers and analytical chemists can demonstrate appropriate quality.
Hand-held X-ray fluorescence spectrometry
This Technical Brief provides an overview and describes the evolution of hand-held X-ray fluorescence instrumentation designed for inorganic elemental analysis and how it can be used for in situ analysis and on-site decision making.
Why do we need the uncertainty factor?
This Technical Brief describes a new way to define and express measurement uncertainty in analytical methods using the uncertainty factor.
The correlation between regression coefficients: combined significance testing for calibration and quantitation of bias
Analytical sciences regression methods are important for instrumental analysis and method comparison studies, this technical brief discusses the importance and correlation of coefficient values.
Revision of the International System of Units (Background paper)
This technical brief explains why four of the International System of Units’ seven base units – the mole, the ampere, the kelvin, and the kilogram – have been re-defined.
Analytical pyrolysis in cultural heritage
Analytical pyrolysis (Py), especially when coupled with gas chromatography and mass spectrometry (Py-GC-MS), is a powerful technique for the characterisation and identification of organic materials used in artwork.
Beam sampling: taking samples at the micro-scale
Beam sampling occurs in most micro-analytical measurements, such as those by Secondary Ion Mass Spectrometry. The uncertainty of such measurements must therefore include the uncertainty arising from this sampling process.
Identification of plastics in cultural heritage collections by Fourier transform infrared spectroscopy (FTIR)
This Technical Brief focuses on the application of FTIR spectroscopy and outlines the different types of materials commonly found in museum collections. The different types of attachments and techniques are also described here.
Are my data normal?
The normal distribution is the expected outcome when a result stems from numerous stages of the measurement process, each of which introduces a small independent error. Sometimes we need to test whether a dataset complies with that expectation.
A ‘Periodic Table’ of mass spectrometry instrumentation and acronyms
An overview of mass spectrometry instrumentation is combined with a novel presentation of the techniques and components which aids in decoding their acronyms.
Surface-enhanced Raman spectroscopy (SERS) in cultural heritage
Surface-enhanced Raman spectroscopy (SERS) has been increasingly used in the last decade for the identification of organic colourants in works of art. This technical brief focuses on the practical aspects of SERS in its application to the analysis of cultural heritage material.
dPCR – the digital polymerase chain reaction
The digital polymerase chain reaction provides an important step forwards in the quantitative study of DNA.
Proficiency testing of sampling
General guidelines for the proficiency testing of sampling are required to handle the special complications involved.
X-ray fluorescence (XRF) analysis of porcelain: Background paper
X-ray fluorescence is used for a wide variety of purposes in the examination of heritage objects made from porcelain.
This technical brief aims to dispel the mythology of metrology, explain important aspects and demonstrate the value of metrology to chemical measurements.
UV-visible-NIR reflectance spectrophotometry in cultural heritage: Background paper
Diffuse reflectance spectrophotometry in the ultraviolet, visible and near-infrared spectral range is becoming a widely-used tool for the non-invasive analysis of cultural heritage objects.
z-Scores and other scores in chemical proficiency testing—their meanings, and some common misconceptions
ISO 13528 (2015) describes several types of score suitable for interlaboratory studies, but only the simple z-score based on fitness for purpose is recommended here for chemical proficiency tests.
Representative sampling? Views from a regulator and a measurement scientist
The term ‘representative sample’ has been redefined many times and become ambiguous. The recommended alternative is ‘appropriate sample’, implying an uncertainty the is fit for purpose.
AMC Datasets—a resource for analytical scientists
The datasets provide opportunities for the analyst to try out a variety of statistical procedures for investigating the outcome of chemical measurements.
Sampling theory and sampling uncertainty
The strengths and limitations of two approaches to the uncertainty derived from sampling (UfS) are compared. Quantitatively, the experimental approach for estimating UfS is more reliable.
An analyst's guide to precision
Precision, quantified as its inverse, is strongly dependent on the conditions of measurement, and is importantly related to uncertainty.
Using the Grubbs and Cochran tests to identify outliers
The Grubbs test can be used to identify outliers in the results of replicated measurements. The Cochran test is used to identify groups of results with outlying variance in analysis of variance.
Fitness for purpose: the key feature in analytical proficiency testing
Scoring in proficiency testing of analytical laboratories should be based on a fitness-for-purpose criterion.
Raman spectroscopy in cultural heritage: Background paper
This Technical Brief outlines the advantages and limitations of Raman spectroscopy in cultural heritage research, what the technique can be used for and what type of information can be gathered. The different types of equipment, lasers and experimental set-ups are also discussed.
Heritage Science – an introduction
Heritage Science is the scientific study of cultural and historic artefacts to assist their conservation and preservation.
Sample stability studies for environmental analysis
Ensuring the stability of the test material between sampling and analysis is an essential aspect of chemical measurement.
Unbalanced robust ANOVA for the estimation of measurement uncertainty at reduced cost
For the estimation of uncertainty from sampling, an unbalanced design combined with a robust analysis of variance provides an economic experiment that is not sensitive to a small proportion of outlying results. Software is provided.
Meat and poultry nitrogen factors
The determination of nitrogen as a quantitative marker for meat fat-free protein and the calculation of meat content of compound foods is the established official chemical method to enforce labelling declarations of meat content in food products.
Seafood nitrogen factors
The determination of nitrogen as a quantitative marker for fat-free protein is the official chemical enforcement method for the calculation of seafood content of seafood products.
The “Phase-of-the-Moon” paradox in uncertainty estimation
Many extraneous factors can affect an analytical result. Analysts preparing an uncertainty budget should use judgement in deciding whether to include uncertainty resulting from empirical tests of implausible influences.
A representative sample must be unbiased and with an associated between-sample standard deviation that is smaller than that regarded as fit for purpose in the application.
PCR – the polymerase chain reaction
The polymerase chain reaction (PCR) has widespread analytical applications in the food, environmental, medical and forensic fields. This Technical Brief covers the basics of PCR and some of its variations.
Estimating sampling uncertainty – how many duplicate samples are needed?
Uncertainty from sampling can be estimated by using a hierarchical experiment, but the quality of the uncertainty estimates has to be balanced against the size (and cost) of the experiment.
An introduction to non-parametric statistics
Non-parametric statistical methods for significance testing make few assumptions about the distribution of results and are often simple to use.
What causes most errors in chemical analysis?
Errors in chemical analysis are often discussed but seldom reliably attributed to specific causes. Feedback from participants in proficiency tests is an ideal source of information, however, and a recent study has shown that simple human error is by far the main culprit.
Experimental design and optimisation (4): Plackett–Burman designs
Good experimental design is important in many analytical and other chemical studies. The Plackett–Burman method is a popular and economical approach that gives information, in a manageable number of experiments, on the effects of many factors that might influence a chemical measurement.
Checking the quality of contracted-out analysis
Contracted-out analysis is normally conducted against a specification of the maximum uncertainty acceptable in the results. This Technical Brief outlines some methods by which customers can check whether the specification is being fulfilled.
Analysts following the GUM method for expressing the uncertainty of their results have a strong tendency to underestimate. This stems from the difficulty of expressing as a measurement model procedures as complex as chemical measurement. The discrepancy is referred to as ‘dark uncertainty’.
Bayesian statistics in action
This Technical Brief outlines some examples of the importance of Bayesian statistical methods in a variety of areas of applied analytical science.
Quality control of routine sampling in chemical analysis
Samples from one target differ in composition from the target and from each other. Randomised duplication provides a basis for quality control of sampling and indicates when sampling uncertainty exceeds expectations.
Robust regression: An introduction
The latest Technical Brief from the Analytical Methods Committee examines applications of regression methods for calibration and comparison.
About this collection
The Analytical Methods Committee (AMC) is the Committee of the Royal society of Chemistry Analytical Division that handles matters of technical importance to the Analytical Science Community. The broad aim of the AMC is to participate in national and international efforts to establish a comprehensive framework for appropriate quality in chemical measurement, and to keep the analytical science community informed of developments.
The AMC produce Technical Briefs carefully drafted by expert working groups and peer reviewed by the AMC to provide reliable and up-to-date information on a wide range of analytical topics.
The AMC Technical Briefs have been collated in this online collection and new Technical Briefs will be added as they are published.
When citing these articles please cite the number of the AMCTB e.g. Analytical Methods Committee AMCTB No. 82 as the “authors” of the article.
For more information about the AMC and to access Technical Briefs published before 2012 please visit their website