K. K. Purohit

Trace element estimation in soils: An appraisal of ED-XRF technique using group analysis scheme

ABSTRACT The nondestructive nature, easier sample preparation and simultaneous multi-element analysis capability of the Energy Dispersive X-ray Fluorescence (ED-XRF) Spectrometry, makes it an attractive technique for the elemental analysis of a wide range of materials. Optimised operating conditions enhance the detection efficiency and improve the minimum detection limits for several elements analysed in a group. The present study shows the performance of an ED-XRF system in analysing 15 important trace elements (V, Cr, Co, Ni, Cu, Zn, Ga, Pb, Th, Rb, U, Sr, Y, Zr, and Nb) in soils and sediment samples. These elements were divided into two groups and were analysed at different operating conditions suitably optimized for each group. The grouping of the elements was done keeping in view the optimum excitation and detection condition requirement for each group of elements. The medium-Z elements (V, Cr, Co, Ni, Cu, Zn, and Ga) were called as group “A” elements, while the rest were taken into group “B.” Well characterised soil and sediment reference samples were used to estimate the quality (precision and accuracy) of the analysis data produced by ED-XRF. Optimisation of the analysis procedure and achievable Minimum Detection Limits were studied. The analysis scheme may prove useful when a large number of soil and sediment samples are required to be analysed.

Trace element characteristics of a new silicate reference material from Himachal Himalaya (India)

ABSTRACT Geological rocks and soils involve complex matrix compositions and their characterization is very difficult. Analysis of trace elements in soils and other silicate rocks seriously suffer due to the lack of availability of suitable silicate reference materials. Environmentally sensitive elements are of particular concern. In this paper, we discuss the procedures for characterization of the 27 trace elemental abundance in a new silicate reference sample of granitic composition (named as DG-H). A total number of about 2500 units of data for more than 50 trace elements were received from as many as 44 laboratories. The element wise data sets were subjected to rigorous statistical treatment to identify the outliers and subsequent rejection. Rest of the data, called “qualified data,” are therefore, used to estimate five estimators of central tendency, robust, as well as non-robust, viz., Mean, Median, Geometric Mean, Gastwirth Median, and Trimean. The arithmetic mean, called Preferred Mean (PM) of the above five estimates is assigned as Working Value or Recommended Value. As many as 23 elements are assigned recommended values, whereas rest four elements are found marginally less characterized. This reference sample would benefit the potential analytical community engaged in analysis of trace elements silicate in materials like rocks and soils.