Articles and Columns

LC/MS/MS analysis of PFAS at ultra-trace levels requires mitigation to both liquid chromatograph and mass spectrometer to eliminate the leaching of fluorochemicals from components within the systems. Manual SPE configurations also require mitigative steps to eliminate any components constructed of PTFE to minimise or eliminate any PFAS contamination.

“Error” and “uncertainty” are being used interchangeably and confusingly. This is “a scientific flaw of the first order”! However, Kim and Francis will put you right.

Non-linear spectroscopy can have various applications in different fields due to the accuracy and resolution it provides. This article describes a few possible applications that show the importance of non-linear spectroscopy.

Sampling and Vikings seems to be the next unexpected connection within Kim Esbensen’s Sampling Column. Kim has been exploring an area of Southern Norway from where the founder of the Theory of Sampling, Pierre Gy, believed his ancestors originated. You will have to read the column to find the “smoking axe”! Oh, and there is an interesting report on the 10th World Conference on Sampling and Blending.

John Hammond has taken a break from his Four Generations magnum opus and reports on the recent meeting of the ISO technical committee on reference materials (ISO TC 334).

This article describes the use of synchrotron X-ray fluorescence and absorption spectroscopies to image metals in the brain.

This article looks at three related spectroscopic techniques/tools in the toolbox, namely, Fluorescence, near infrared (NIR) and Raman; and discuss the “what”, “where” and “how” of these techniques are being used to improve the quality of the measurement processes associated with them.

Despite a multitude of chemical and physical methods capable of detecting fingerprint residues, there are substantial challenges with fingerprint recovery. Spectroscopic methods have played a critical role in the analysis of fingerprints, used to identify the chemical constituents present, examine their degradation over time and compare the chemical variation between donors.

Sampling is nothing more than the practical application of statistics. If statistics were not available, then one would have to sample every portion of an entire population to determine one or more parameters of interest. There are many potential statistical tests that could be employed in sampling, but many statistical tests are useful only if certain assumptions about the population are valid. Prior to any sampling event, the operative Decision Unit (DU) must be established. The Decision Unit is the material object that an analytical result makes inference to. In many cases, there is more than one Decision Unit in a population. A lot is a collection (population) of individual Decision Units that will be treated as a whole (accepted or rejected), depending on the analytical results for individual Decision Units. The application of the Theory of Sampling (TOS) is critical for sampling the material within a Decision Unit. However, knowledge of the analytical concentration of interest within a Decision Unit may not provide information on unsampled Decision Units; especially for a hyper-heterogenous lot where a Decision Unit can be of a completely different characteristic than an adjacent Decision Unit. In cases where every Decision Unit cannot be sampled, application of non-parametric statistics can be used to make inference from sampled Decision Units to Decision Units that are not sampled. The combination of the TOS for sampling of individual Decision Units along with non-parametric statistics offers the best possible inference for situations where there are more Decision Units than can practically be sampled.

Tony Davies marks the passing of Svante Wold, who gave us “chemometrics”. It all started with a grant application!