Procedure: spICP-MS for analysis of ENM dissolution over time

University of Birmingham utilises a PerkinElmer NexION 300D spICP-MS instrument. The protocol described here has been applied to assess the dissolution of ENMs in a range of environmental media and matrices, including following uptake into organisms

  1. Selected ENMs are incubated in exposure medium for fixed times (e.g. 4 hours, 24 hours, 48 hours etc.), with or without shaking and with temperature control and light/dark cycles to mimic the realistic exposure conditions.
  2. At selected timepoints, samples are diluted with MilliQ water to concentrations of around 50,000 particles mL-1 which is within the range of detection of the NexION 300D.
  3. ENMs are analysed for the selected element(s) and the amount of ENMs versus ions at each timepoint is determined.  The ENM size can also be determined to assess loss of particles over time.
  4. From the quantification of the increase in the ionic fraction over time, the rate of ENM dissolution can be determined.  Note that there can also be re-precipitation of ENMs in environmental media / matrices, so the ENM size information is a useful additional piece of information to help interpret the data.

Mechanisms & Methods

Used for

In many previous dissolution studies, e.g. using ICP-MS, it was necessary to separate the intact ENMs from the dissolved ions at each timepoint, using for example, filtration or centrifugation.  These processes can lead to loss of material or influence the dissolution kinetics, leading to artefacts.  Typically, both the total metal and the dissolved fraction were measured separately.

When spICP-MS is applied, no separation step is needed, and a single measurement on each sample quantifies the amount of particles, their sizes / size distribution, and the amount of ions in the background, increasing the accuracy of the results.

For each ENM type, it is essential to include relevant ENM controls to assess the transport efficiency of the instrument, and to include elemental standards to build the calibration curve. Typically, calibration of the NexION 300D is performed using NIST ICP-MS standards at several concentrations, e.g. 1, 2, and 3 parts per billion (1 ppb is equivalent to 1 mg/L), and 2 sizes of ENMs of equivalent composition. 





       NanoFASE Case study:
ENM uptake and dissolution in isopods




Benjamin Fryer

University of Birmingham




Iseult Lynch

University of Birmingham