Elemental analysis of soil samples for forensic purposes by inductively coupled plasma spectrometry - precision considerations

Major and trace elemental composition provides a powerful basis for forensic comparison of soils, sediments and rocks. However, it is important that the potential 'errors' associated with the procedures are fully understood and quantified, and that standard protocols are applied for sample preparation and analysis. This paper describes such a standard procedure and reports results both for instrumental measurement precision (repeatability) and overall 'method' precision (reproducibility). Results obtained both for certified reference materials and example soils show that the instrumental measurement precision (defined by the coefficient of variation, CV) for most elements is better than 2-3%. When different solutions were prepared from the same sample powder, and from different sub-sample powders prepared from the same parent sample, the CV increased to c. 5-6% for many elements. The largest variation was found in results for certified reference materials generated from 23 instrument runs over an 18 month period (mean CV=c. 11%). Some elements were more variable than others. W was found to be the most variable and the elements V, Cr, Co, Cu, Ni and Pb also showed higher than average variability. SiO2, CaO, Al2O3 and Fe2O3, Rb, Sr, La, Ce, Nd and Sm generally showed lower than average variability, and therefore provided the most reliable basis for inter-sample comparison. It is recommended that, whenever possible, samples relating to the same investigation should be analysed in the same sample run, or at least sequential runs.

Public sector pay in the UK: has the historic pattern of public/private sector pay movements been broken?

The historic pattern of public sector pay movements in the UK has been counter-cyclical with private sector pay growth. Periods of relative decline in public sector pay against private sector movements have been followed by periods of ‘catch-up’ as Government controls are eased to remedy skill shortages or deal with industrial unrest among public servants. Public sector ‘catch up’ increases have therefore come at awkward times for Government, often coinciding with economic downturn in the private sector (Trinder 1994, White 1996, Bach 2002). Several such epochs of public sector pay policy can be identified since the 1970s. The question is whether the current limits on public sector pay being imposed by the UK Government fit this historic pattern or whether the pattern has been broken and, if so, how and why? This paper takes a historical approach in considering the context to public sector pay determination in the UK. In particular the paper seeks to review the period since Labour came into office (White and Hatchett 2003) and the various pay ‘modernisation’ exercises that have been in process over the last decade (White 2004). The paper draws on national statistics on public sector employment and pay levels to chart changes in public sector pay policy and draws on secondary literature to consider both Government policy intentions and the impact of these policies for public servants.