Development of a routine method for the determination of trace metals in whole blood by magnetic sector inductively coupled plasma mass spectrometry with particular relevance to patients with total hip and knee arthroplasty.

BACKGROUND Joint-replacement surgery has revolutionized the treatment of osteoarthritis and is still the most effective therapy. A recent clinical trend reintroducing metal-on-metal bearing surfaces has in turn stimulated a requirement for accurate measurement of the concentrations of relevant metals in both pre- and postoperative patients. Thus, there is a need for cost-effective, multielement methods for trace metal analysis in whole blood to monitor possible increases in wear metal concentrations. METHODS A method was developed to allow routine analysis of whole blood samples for molybdenum, cobalt, chromium, and nickel. Sample preparation consisted of a simple 1:10 dilution of whole blood with a solution of 10 mL/L Triton X-100, 0.0002 mol/L EDTA, and 0.01 mol/L ammonium hydroxide. Final determination was performed by a double-focusing magnetic sector inductively coupled plasma mass spectrometer operated in medium-resolution mode (resolution, 3400). Online addition of rhodium was used for internal standardization. RESULTS Detection limits in whole blood were 0.06 microg/L for chromium, cobalt, and molybdenum and 0.30 microg/L for nickel. Base concentrations of 0.22, 0.17, 0.62, and 0.99 microg/L for chromium, cobalt, molybdenum, and nickel, respectively, in whole blood have been found. Polyatomic interferences on all four elements have been shown to be resolved from the analyte masses by use of a resolution of >3000. CONCLUSIONS The simple, rapid method of sample preparation is effective in minimizing potential contamination and enables 60 samples (run time, 8 h) to be analyzed before cleaning the instrument is necessary. A resolution >3000 was sufficient to separate polyatomic interferences from the masses of interest. The method was used to analyze a large number of blood samples taken from primary patients awaiting total hip arthroplasty. The method is sensitive enough to provide base concentrations for chromium, cobalt, and molybdenum in whole blood. The results for nickel were compromised by high signals for blank samples.