Targeting Metal Impurities for the Detection and Quantification of Carbon Black Particles in Water via spICP-MS

Carbon black (CB) is a nanomaterial with numerous industrial
applications
and high potential for integration into nano-enabled water treatment
devices. However, few analytical techniques are capable of measuring
CB in water at environmentally relevant concentrations. Therefore,
we intended to establish a quantification method for CB with lower
detection limits through utilization of trace metal impurities as
analytical tracers. Various metal impurities were investigated in
six commercial CB materials, and the Monarch 1000 CB was chosen as
a model for further testing. The La impurity was chosen as a tracer
for spICP-MS analysis based on measured concentration, low detection
limits, and lack of polyatomic interferences. CB stability in water
and adhesion to the spICP-MS introduction system presented a challenge
that was mitigated by the addition of a nonionic surfactant to the
matrix. Following optimization, the limit of detection (64 μg/L)
and quantification (122 μg/L) for Monarch 1000 CB demonstrated
the applicability of this approach to samples expected to contain
trace amounts of CB. When compared against gravimetric analysis and
UV–visible absorption spectroscopy, spICP-MS quantification
exhibited similar sensitivity but with the ability to detect concentrations
an order of magnitude lower. Method detection and sensitivity was
unaffected when dissolved La was spiked into CB samples at environmentally
relevant concentrations. Additionally, a more complex synthetic matrix
representative of drinking water caused no appreciable impact to CB
quantification. In comparison to existing quantification techniques,
this method has achieved competitive sensitivity, a wide working range
for quantification, and high selectivity for tracing possible release
of CB materials with known metal contents.