ASTM E3269 PDF

1.1”This test method describes the use of inductively coupled plasma optical emission spectrometry (ICP-OES; also includes ICP-AES, where AES is atomic emission spectrometry) or inductively coupled plasma mass spectrometry (ICP-MS) for the determination of the mass fraction of particle bound gold (Au) in colloidal Au suspensions. Particle bound Au is defined as the mass of Au associated with the nanoparticle (NP) fraction and strongly adsorbed to the particle surface. Unbound Au is the fraction of Au in the native suspension not associated with the Au nanoparticle fraction that is, the dissolved Au existing in solution as a complex or free ion. The mass fraction of particle bound Au is determined by subtracting the mass fraction of unbound Au measured in acidified subsamples of the particle-free supernatant from the total Au mass fraction measured in acid-digested subsamples of the colloidal Au suspension. The particle-free supernatant is obtained after centrifugation of the colloidal Au suspension. This standard prescribes the use of an appropriate internal standard and calibration using either external standardization or single-point standard additions.