Environmental Engineering Reference
In-Depth Information
10.5 Metals and Inorganics: Opportunities for
Next-Generation Instruments
Traditional methods struggle to measure metals at the ppb level, requiring complicated pre-
concentration steps that vex even experienced laboratory operators. The US Environmental
Protection Agency (EPA) lists some 24 so-called “heavy metals” of interest, and acceptable
levels for discharge or drinking water for many of these tighten irregularly but inexorably
throughout the developed world.
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The predictable if strict measurement range and the limited number of analytes make
metals an ideal target for next-generation technologies, and a number are under develop-
ment or currently deployed.
• Most metals require measurement at the ppb level. With the exception of tradi-
tional high-level metals, such as copper, which commonly appears at ppm concen-
trations, most metals and inorganics of concern hover in the range of a few ppb for
most applications. This is in the range of next-generation online instruments and
handheld tests.
• Metal analysis contains a limited number of analytes. A cursory glance at the peri-
odic table shows there are only so many metals one could ever measure. Inorganic
ions are likewise simple and small in number. This is a bit of an oversimpliica-
tion: many metal species exist in a number of oxidation states, only one or a few
of which may be of interest. Highly toxic organometallic species such as organic
tin and dimethyl mercury also have the potential to broaden the list. Nevertheless,
metal and inorganic analysis is relatively concrete and deinable, a market with
clear delineation that developers can target as a whole or in part.
• Traditional metal analyses do not translate to online instruments. Online instru-
ments for metals are generally ion-selective electrodes, which are subject to inter-
ferences and require fairly frequent calibration, although they retain the potential
for miniaturization and other improvements.
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A number of quantitative labora-
tory methods for metals also exist, most notably atomic emission spectroscopy
and a range of mass spectrometer-related methods.
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Laboratory techniques involving mass spectrometry and high-energy methods such as
inductively coupled plasmas do not translate well to online instruments.
This leaves the door open to online instruments with advanced technologies that can
both quantitate and speciate metals at the 1-10 ppb level. One start-up of particular note is
ANDalyze, which uses short lengths of DNA to bond with and luoresce in the presence of
a metal.
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The technique is more stable than other biologically derived reagents. The com-
pany has a ield method and is developing an online system.
Based in the Netherlands, Capilix uses microchip capillary electrophoresis sensors to
monitor water quality.
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Early customers include greenhouse growers. The sensors can
read a wide range of agriculturally relevant parameters, including ammonium, nitrate,
phosphate, potassium, iron, and manganese. The company is also targeting the anaerobic
digestor market. Metrohm acquired the company in late 2012, showing that the industry
has an appetite for next-generation analytics.
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OndaVia, another start-up, uses enhanced Raman spectroscopy employing coated gold
nanoparticles in disposable cartridges. The method could, in theory, measure a wide range of
