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

Abstract

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 μg/L for chromium, cobalt, and molybdenum and 0.30 μg/L for nickel. Base concentrations of 0.22, 0.17, 0.62, and 0.99 μg/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.

Inductively Coupled Plasma Mass Spectrometry: Introduction to Analytical Aspects

“…ammonium hydroxide, tetramethylammonium hydroxide). [4][5][6][7][8] Deionised water has been used as a diluent, however some elements are unstable in pure water, therefore acidic or alkaline diluents are preferred in most cases. 9,10 The isoelectric point of many proteins is approximately 5-6, therefore the addition of an acidic diluent to a highly proteinaceous sample such as blood Table 1.…”

“…Several different types of mass analyser have been used for ICP-MS; these include quadrupole, magnetic sector and (rarely) time-of-flight (TOF). 7,28 By far the most common type used for routine clinical biochemistry applications is the quadrupole mass analyser.…”

“…An internal standard is often incorporated into the diluent used for sample preparation (usually at a concentration of 50-100 µg/L), however it may also be added via a T-piece in the sample introduction system. 7 For methods which employ internal standards, the accuracy of the measured result is clearly dependent on the suitability of the internal standard.…”

“…The resolution required to separate these ions is approximately 2376, hence a magnetic sector mass analyser is able to distinguish these ions. 7 In fact, these ions have been successfully resolved using a doublefocusing magnetic sector ICP-MS in medium-resolution mode (resolution 3400). 7 High-resolution instruments are significantly more expensive than quadrupole instruments, however, and are therefore mainly used for research purposes.…”

Clinical usefulness of blood metal measurements to assess the failure of metal-on-metal hip implants

“…High resolution ICPMS, using a double focusing magnetic sector mass spectrometer, is available in a few laboratories and overcomes the uncertainties of interference reduction with collision/reaction cells. 35 – 37 The interferences can usually be completely resolved, but the expense of the hardware will preclude the use of this technique in all but a few specialist and research laboratories. Krachler et al .…”