Validation of an inductively coupled plasma-mass spectrometry method to quantify tungsten in human plasma. Determination of percentage binding to plasma proteins

Background: The aim of this paper was to validate an inductively coupled plasma-mass spectrometry (ICP-MS) method to quantify tungsten in human plasma and to study its percentage binding to plasma proteins. Methods: This method was validated with respect to accuracy, precision, selectivity and limits of quantification and of detection according to Good Laboratory Practice Guidelines. Calibration curves were obtained in the range 10–500 ng/ml. The extent of plasma protein binding was determined by ultrafiltration in the range 40–2000 ng/ml. Results: A significant matrix effect was observed. The linearity of this method was statistically proven. Precision ranged from 0.76% to 6.49%, and accuracy from 97% to 102%. The lower limit of quantification (LLOQ) was 10 ng/ml. The mean percentage of unbound fraction was 89%. Conclusions: The results obtained indicate that the method described fulfills the accuracy and precision requirements necessary to carry out pharmacokinetic studies in man.