Ellison S.L.R.,LCG Group
The developments that led to the third edition of the Eurachem Guide 'Quantifying Uncertainty in Analytical Measurement' are reviewed. Particular attention is given to the rationale for early use of spreadsheet methods, the incorporation of method performance data in the second edition, and the third edition's provisions on uncertainties near zero and Monte Carlo methods. The development of uncertainty concepts in chemistry is reviewed briefly and some of the challenges found in early implementation of measurement uncertainty in chemistry are recalled. Problems arising from uncertainty evaluation for reference measurements with limited data are discussed. © 2014 BIPM & IOP Publishing Ltd. Source
Pritchard C.,LCG Group
To ensure comparability of results in clinical proteomics, methods for accurate and traceable quantification of proteins are required. Typically this is done for recombinant proteins using isotopically labeled peptides as internal standards (IS). However, in order to perform quantification in complex matrices such as human serum, isotopically labeled protein standards have been suggested for use as IS to account for losses in sample preparation. The isotopic diluent must be chemically and physically identical to the analyte of interest, having the same amino acid sequence, post-translational modifications, secondary and tertiary structure. It must not be assumed but rather proven that the isotopic diluent is a true mimic, and here we consider both the advantages and potential pitfalls encountered when using isotopically labeled protein IS. Source
Santamaria-Fernandez R.,LCG Group
Analytical and Bioanalytical Chemistry
This article reviews recent developments in the use of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) to provide high-precision carbon isotope ratio measurements. MC-ICP-MS could become an alternative method to isotope ratio mass spectrometry (IRMS) for rapid carbon isotope ratio determinations in organic compounds and characterisation and certification of isotopic reference materials. In this overview, the advantages, drawbacks and potential of the method for future applications are critically discussed. Furthermore, suggestions for future improvements in terms of precision and sensitivity are made. No doubt, this is an exciting analytical challenge and, as such, hurdles will need to be cleared. © UKCrown: LGC 2010. Source
LCG Group | Date: 2012-06-18
In many situations, particularly in forensic science, there is a need to consider one piece of evidence against one or more other pieces of evidence. For instance, it may be desirable to compare a sample collected from a crime scene with a sample collected from a person, with a view to linking the two by comparing the characteristics of their DNA, particularly by expressing the strength or likelihood of the comparison made, a so called likelihood ratio. The method provides a more accurate or robust method for establishing likelihood ratios through the definitions of the likelihood ratios used and the manner in which the probability distribution functions for use in establishing likelihood ratios are obtained The methods provide due consideration of stutter and/or dropout of alleles in DNA analysis, as well as taking into consideration one or more peak imbalance effects, such as degradation, amplification efficiency, sampling effects and the like.
LCG Group | Date: 2012-05-22
A method for comparing DNA containing test results and stored results is provided, including a) a stored result selection and plurality of stored result database creation stage; b) a test result against stored result comparison stage, including: 1) A test result selection and plurality of test result database creation sub-stage; 2) A single test result database against single stored result database search sub-stage, performed for the various pairs of test result databases and stored result databases, to establish matches; 3) An established match review sub-stage, to filter out established matches which do not feature as matches across the other test result against stored result databases; 4) A process outcome sub-stage which provides details of the matches which extend across all the database pairs.