Effects of storage conditions on the stability and distribution of clinical trace elements in whole blood and plasma: Application of ICP-MS.

BACKGROUND: Knowledge of trace element stability during sample handling and preservation is a prerequisite to produce reliable test results in clinical trace element analysis. METHOD: An alkaline dissolution method has been developed using inductively coupled plasma mass spectrometry to quantify eighteen trace element concentrations: vanadium, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, selenium, bromine, molybdenum, cadmium, antimony, iodine, mercury, thallium, lead, and bismuth in human blood, using a small sample volume of 0.1 mL. The study evaluated the comparative effects of storage conditions on the stability of nutritionally essential and non-essential elements in human blood and plasma samples stored at three different temperatures (4 °C, -20 °C and -80 °C) over a one-year period, and analysed at multiple time points. The distribution of these elements between whole blood and plasma and their distribution relationships are illustrated using blood samples from 66 adult donors in Queensland. RESULTS: The refrigeration and freezing of blood and plasma specimens proved to be suitable storage conditions for many of the trace elements for periods up to six months, with essentially unchanged concentrations. Substantially consistent recoveries were obtained by preserving specimens at -20 °C for up to one year. Ultra-freezing of the specimens at -80 °C did not improve stability; but appeared to result in adsorption and/or precipitation of some elements, accompanied by a longer sample thawing time. A population sample study revealed significant differences between the blood and plasma concentrations of six essential elements and their relationships also varied significantly for different elements. CONCLUSION: Blood and plasma specimens can be reliably stored at 4 °C for six months or kept frozen at -20 °C up to one year to obtain high quality test results of trace elements.

Development and Validation of an ICP-MS Method and Its Application to Determine Multiple Trace Elements in Small Volumes of Whole Blood and Plasma.

Essential and nonessential element concentrations in human blood provide important information on the nutritional status of individuals and can assist in the screening or diagnosis of certain disorders and their association with other causative factors. A simple and sensitive method, suitable for use with small sample volumes, for quantification of multiple trace element concentrations in whole blood and plasma has been developed using inductively coupled plasma-mass spectrometry. Method validation was performed using standard reference materials of whole blood and serum using varying sample treatments with nitric acid, water and hydrogen peroxide. The method was applied to quantify the trace element concentrations in whole blood and plasma samples (0.1 mL) from 50 adult blood donors in Queensland. The whole blood sample (5 mL) was collected in Vacutainer tubes with K2EDTA as anticoagulant. The developed method was able to quantify, in blood and plasma samples over a wide range of concentrations, several essential elements: cobalt, copper, zinc, iron, manganese and selenium; the nutritionally probably essential elements vanadium and strontium; and nonessential elements including lead, cadmium, arsenic, caesium, barium, thallium and uranium. Significant differences (P < 0.0001) were observed between whole blood and plasma concentrations for 13 elements; 5 of the measured elements, cobalt (0.49 vs. 0.36 µg/L), copper (1.0 vs. 0.75 mg/L), strontium (28 vs. 16 µg/L), barium (1.5 vs. 0.64 µg/L) and thallium (0.06 vs. 0.03 µg/L), had higher mean concentrations in plasma than in blood. Whole blood concentrations of nine trace elements were significantly correlated (P < 0.0001) with plasma concentrations. The distribution of the trace elements between human blood and plasma varied considerably for the different elements. These results indicate that, using a small sample volume, this assay is suitable for the evaluation of nutritional status as well as in monitoring human toxic elemental exposures.