Uncertainties of mercury determinations in biological materials using an atomic absorption spectrometer - AMA 254

Abstract

The method is based on catalysed ignition of a sample portion in a flow of oxygen, capture of mercury by an amalgamator and measurement of the mercury vapour's absorbance after thermic release from the amalgamator. Three powdered food samples, a certified reference material (CRM) human hair and a reference material (RM) urine (liquid) were measured in the first range of the instrument (the possible contents determined according to our measurement procedure were 0.0003-0.5 ppm). The calibration function used was a line passing through the origin. The combined standard uncertainties of the mercury determinations were computed from uncertainty components of five quantities: absorbance of the sample, absorbance of the sample blank, slope of the calibration line, correction factor of the abscissa axis, and mass or volume of the sample. The most important uncertainty component is the uncertainty of the sample absorbance measurement which amounts to 52% of the determination uncertainty at the minimum (RM urine) and about 90% at the maximum (in our laboratory homogenized powdered food samples; analysis of variance showed their homogeneity to be insufficient). The results of the CRM and RM analyses do not indicate a significant systematic error for this determination. The relative expanded uncertainty (coefficient was 2) of the determination increases from 9 to 13% for the insufficiently homogenized samples with decreasing mercury content (range of 0.004-0.03 ppm); higher homogeneity of samples results in a decrease of the expanded uncertainty, e.g. 4.6% for the liquid sample (RM urine).

Determination of Mercury and Methylmercury in Hair of the Czech Children’s Population

“…Results for Hgtot were compared with those reported for the "step-by-step" method using the same matrix and the same instrument [24]. The obtained values of 6.7 and 6.5% agreed well together.…”

Mercury determination in solid phases from application of the modified BCR-sequential extraction procedure: a valuable tool for assessing its mobility in sediments

“…However, the average uncertainty reported in the literature in the analysis of solid biological materials by this technique was 3.31% [22,23]. Values ranging from 9 to 13% were only found in the case of insufficiently homogenised samples [24] or in a series of different complex geological samples [25]. The relatively high results obtained in the present work on liquid matrices can be attributed to the high salt contents in all extracts which also have an effect on the catalyser and on sample boat lives.…”

Quantifying uncertainty in measurement of mercury in suspended particulate matter by cold vapor technique using atomic absorption spectrometry with hydride generator

“…The mercury concentrations in ambient air in different various fractions of PM 10 were found to be in the range of 3.13 ng m -3 (26%) – 22.96 ng m -3 (15%) with respective expanded relative uncertainty. Synek et al 2000 estimated uncertainties in mercury determinations in biological materials by atomic absorption spectrometer – AMA 254 and suggested major uncertainty (52%) is due to sample absorbance measurement.…”

“…In this regard ISO has published, “Guide to the expression of uncertainty in measurement (GUM)” in 1995 in collaboration with BIPM, IEC, IFCC, IUPAC, and OIML, which recently was revised as VIM: JCGM 200:2008, Evaluation of measurement data-Guide to the expression of uncertainty in measurement. In last several years the uncertainty estimations for Hg in different matrixes (Kayal et al 2009; & Kayal and Singh 2010 Synek et al 2000; Kumar and Riyazuddin, 2007) have been carried out by various authors. However, determination of mercury in suspended particulate matter (SPM) and evaluating the uncertainty value of the result is a difficult task as there are many parameters involved from sampling to final value, which influence the result.…”