Another side of ensuring that our results are valid is correct sampling. In the latest Sampling Column on “Sampling quality criteria (SQC)” Kim Esbensen and Claas Wagner continue our education in the use of the Theory of Sampling. The fundamental step in ensuring representative sampling is sampling quality criteria, and the authors describe why and how.
Articles and Columns
“Is your spectrometer in calibration?” ask Chris Burgess and John Hammond. The answer may not be as straightforward as you might think. However, Chris and John explain all.
In the Tony Davies Column, Tony is getting jealous of chromatographers in “Central spectroscopic data systems: why are chromatographers so much better equipped?”. Replicating the power of chromatography data systems for spectroscopic data is not that easy.
Much of the exterior surface of plants is covered by the cuticle. This plays a vital role in protecting the plant from water loss, attack by pests and pathogens and damage from UV radiation. Infrared spectroscopy is very useful in characterising cuticles, as we learn in “Infrared spectroscopy as a tool to study plant cuticles” by José Heredia-Guerrero, José Benítez, Eva Domínguez, Ilker Bayer, Roberto Cingolani, Athanassia Athanassioua and Antonio Heredia. The authors point out that, whilst still in its early stages, infrared spectroscopy has provided valuable information about the functional groups, chemical structure and arrangement and interactions of plant cuticle components.
Research into climate change takes many directions, but storing carbon or understanding its release from stores is extremely important. Pyrogenic carbon comes from the incomplete burning of biomass, and can be natural, e.g. wild fires, or man-made, e.g. the production of charcoal. The authors describe the uses of a range of spectroscopy techniques to understand the molecular structure of pyrogenic carbon and its role in the global carbon cycle.
Peter Jenks looks back to the BERM 14 conference on biological and environmental reference materials in the Quality Matters Column. The next conference in the series returns to Europe: Berlin in June 2018.
The bio theme moves to mass spectrometry in “Solid mixed matrices and their advantages in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry” by Marek Šebela. Getting the most from various matrices for use in matrix-assisted laser desorption/ionisation (MALDI) has always been a bit of an art, and the introduction of mixed matrices may increase the number of possible combinations but may improve reproducibility and so simplify analysis in the end. The author describes mixed matrices for a range of samples including proteins, peptides, oligosaccharides, oligonucleotides, lipids, polymers and even intact microbial cells!
As you will have noticed from this issue’s cover, we are making a colourful start to 2016. In the first article on “The analytical niche for Raman spectroscopy in biological pigment research”, Daniel Thomas and Cushla McGoverin suggest that Raman spectroscopy may have a particularly valuable role in pigment biology research. Pigments are almost universal in biology and are the basis of much of what we find attractive in flowers, birds and sea life, such as the fan corals on the cover. The authors show how Raman spectroscopy can be used to quickly confirm the presence of a pigment as well as providing more detailed knowledge about unknown pigments.
“Spectroscopic data handling at petabyte scale” shows how one institute is dealing with truly huge amounts of data, both in its collection and in its distribution to scientists for interpretation and analysis. At the same time, the institute has been able to incorporate best practice around the FAIR Data Stewardship of scientific information.
In the Sampling Column, Kim Esbensen and Claas Wagner continue our education about representative sampling. In “Sampling quality assessment: the replication experiment”, they provide an overview of the issue of replication, which may not be as straightforward as might be expected at first.
In the Quality Matters Column, Peter Jenks, Paul Boother and Annette Marshall are concerned about “The proper use of certified reference materials for analytical instrumentation qualification”. There are many aspects to consider in ensuring the validity of an analytical system, from before any instrumentation is installed, before it is used and during its use. Readers interested in the chemicals and reference material field may be interested in the news that, as this issue was being prepared, Merck completed its $17-billion acquisition of Sigma-Aldrich.
Another surface problem is tackled by Richard Pilkington, Stuart Astin and John Cowpe: “Application of laser-induced breakdown spectroscopy for surface hardness measurements”. Measuring the hardness of materials is not entirely straightforward, and the authors show that laser-induced breakdown spectroscopy offers the potential for in situ hardness measurements, without prior sample preparation.
This article tells us about another: “Fast and versatile ambient surface analysis by plasma-assisted desorption/ionisation mass spectrometry”. They show that surface analysis can greatly benefit from approaches using surface–plasma interactions and that PADI shows significant promise to become a valuable and versatile tool for this.
Kim Esbensen and Claas Wagner’s Sampling Column also addresses issues around ensuring valid results, from the sampling perspective. “Composite sampling II: lot dimensionality transformation” continues to address the problem of heterogeneity and how to overcome it. If you can find a time when your bulk (3D) sample becomes a 1D sample, the job is possible. Interesting examples from unloading a grain ship to emptying a fishing boat hold are described.
In the Tony Davies Column, Tony looks at “Raman imaging of difficult surfaces”. He looks at a number of different approaches to dealing with uneven samples, as well as reviewing instrumental improvements that have made Raman imaging a viable analytical and diagnostic tool.
To ensure that the removal and treatment of our sewerage meets increasingly high standards, it is important to be able to monitor the water online both to provide timely information and also to establish changing patterns over days, weeks and seasons. In their article “On-line monitoring for improved wastewater system management: applications of ultraviolet/visible spectroscopy”, Rita Brito, Rita Ribeiro, Tatiana Arriaga, Catarina Leitão, Nìdia Lourenço, Filipa Ferreira and Helena Pinheiro demonstrate the value of on-line UV/vis spectroscopy for wastewater quality monitoring in decentralised wastewater treatment and for spectral on-line monitoring of key quality parameters at the inlet to wastewater treatment plants.
Graphene has been receiving a large amount of interest as its commercial possibilities begin to be realised. Now, with hundreds of companies offering commercial graphene production, analytical measures of graphene quality are required. Raman spectroscopy can be used to “understand the number of layers, strain, doping and importantly the level of disorder present in graphene”, which is described in this article: “Graphene characterisation and standardisation via Raman spectroscopy” by Andrew Pollard and Debdulal Roy.
In the “The analysis of poly aromatic compounds: a never-ending story?”, Peter Jenks reports from the 25th International Symposium on Poly Aromatic Compounds. He concludes that “data from the academic and research community often acts as a stimulus for government concern and the data may ultimately result in legislation. It concerns me that legislation may be driven by bad data”.
In this column, Tony describes “A new approach to identifying unknown trace level analytes by tandem mass spectrometry without reference spectroscopic database support: CSI:FingerID”. This allows for tandem mass spectrometry data to be used to identify unknown analytes from common molecular structure databases where reference spectroscopic data is unavailable.
Fine sediments, often due to run-off from the land, can clog the surface and sub-surface spaces in gravel beds used by spawning fish to lay their eggs and by aquatic insects. Without an adequate flow of oxygenated water, the eggs and insects die. Heather Haynes, Susithra Lakshmanan, Anne-Marie Ockelford, Elisa Vignaga and William Holmes tells us about this in “The emerging use of magnetic resonance imaging to study river bed dynamics”. They have studied the infiltration of various sediments into model gravel beds both outside and flowing through a MRI instrument! They conclude that MRI “provides an exciting opportunity to unravel a plethora of processes relevant to wider environmental science”.