Total cobalt determination in human blood and synovial fluid using inductively coupled plasma-mass spectrometry: method validation and evaluation of performance variables affecting metal hip implant patient samples

Abstract

Inductively coupled plasma with mass spectrometric detection (ICP-MS) has been used for clinical analysis of cobalt (Co) due to its sensitivity and specificity; however, media-specific validation studies are lacking. This study provides data on performance variables affecting differences between selected analytical platforms (Perkin Elmer and Agilent), tissue sample preparation, storage, and interferences affecting measurements in whole blood, serum, and synovial fluid. The limits of detection (LOD) range from 0.2–0.5 µg/L in serum and synovial fluid, and 0.6–1.7 µg Co/L in whole blood. The Agilent platform with collision reaction cell is more sensitive, while the Perkin Elmer platform with dynamic reaction cell demonstrates more polyatomic interferences near the LOD for serum and whole blood. Split sample analysis showed good accuracy, precision, and reproducibility between serum Co measurements using acid digestion or detergent dilution preparations for persons with metal hip implants or following supplement intake. The results demonstrated reliability of the ICP-MS methodology across the two analytical platforms and between two commercial laboratories for Co concentrations above 5 µg Co/L, but digestion procedures and polyatomic interferences may affect measurements in some media at lower concentrations. These studies validate the described ICP-MS methodology for clinical purposes with precautions at low cobalt concentrations (<5 µg Co/L).

Keywords:

• metal-on-metal hip implant
• cobalt-chromium-molybdenum alloy implant
• polyatomic interference
• collision reaction cell
• dynamic reaction cell
• analytical method
• blood cobalt
• synovial fluid
• triple quadrupole

Acknowledgments

The authors would like to acknowledge Ken Unice, Brooke Tvermoes, and Monty Liong for their helpful input and peer review of the manuscript, and Chris Ronk for his assistance with the statistical analyses. Funding for this paper and for the analytical work and method development was primarily provided by DePuy Orthopedics, Inc., with additional funding provided by the three firms (Cardno ChemRisk, Exponent and Applied Speciation and Consulting) that employ the authors.

Disclosure statement

Two of the authors (RG, HG) are employed by Applied Speciation and Consulting, an analytical laboratory and metals chemistry consulting firm. Three authors (AU, DP, BK) were employed by Cardno ChemRisk at the time the manuscript was prepared (BK is currently employed by Exponent, Inc). Cardno ChemRisk is a consulting firm that provides scientific advice to the government, corporations, law firms, and various scientific/professional organizations. This work was funded by DePuy Orthopedics, Inc., a manufacturer of prosthetic devices, some of which contain cobalt. This paper was prepared and written exclusively by the authors without review or comment by DePuy Orthopedics, Inc. employees or counsel. It is likely that this work will be relied upon in medical research, nutrition research, and litigation. Some of the authors may be called upon to serve as expert witnesses.

Additional information

Funding

DePuy Orthopedics, Inc.; Cardno ChemRisk; Exponent; Applied Speciation and Consulting.