This document provides a protocol for measuring the electrolytic conductivity (κ) of nanoparticle suspensions of composition similar to NIST Reference Materials (RMs) 8011, 8012, and 8013, which contain gold nanoparticles in a dilute electrolyte solution.  The κ value is measured by dip cell calibrated with two κ standards.  Traceability is to the κ values of the respective standards.  The measurement as described may be applied to small volumes (4 mL to 5 mL) and is therefore applicable to the contents of a single ampoule of each of the above RMs.

To minimize consumption of the nanoparticle suspension, the protocol for pH measurement (see procedure PCC-13) may be performed following this measurement of κ of the same sample, provided that κ is measured according to the below protocol.  However, seepage of KCl from the reference junction of the pH electrode during the measurement of pH contaminates the sample with K⁺ and Cl⁻ ions, thereby increasing any κ value obtained subsequently.  For this reason, in a serial measurement of pH and κ on a single sample, the κ measurement must be performed first.

Nanoparticle suspensions of significantly different composition from NIST RMs 8011, 8012, and 8013 may require substitution of different κ standards to account for κ values outside the range 100 µS/cm to 500 µS/cm.  If such a substitution is performed, the two conductivity standards selected should bracket the value of the sample being measured.

• NCL_Method_PCC-12.pdf(PDF | 330 KB)

Researchers should cite this work as follows:

• Pratt, K. (2020). NIST - NCL Joint Assay Protocol, PCC-12. NCI Hub. doi:10.17917/9Q5G-G245

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