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XRF cannot, namely carbon, which enables distinguish-
ing low and high grades of stainless steel, and very low
concentrations of sulfur and phosphorus in steel. OES
determines the nitrogen content and thereby identifies
duplex steels. However, this technique is less portable,
requires more calibration maintenance, typically uses an
argon gas purge, and sometimes requires additional sam-
ple preparation.
Handheld LIBS features the benefits of both tech-
niques—it can measure lighter elements than XRF (e.g.,
beryllium in copper alloys), minimal sample preparation is
required, and operation is rapid and does not require a ra-
diation source or gas purge. Depending on the application,
XRF and OES can make it difficult to measure small or
awkwardly shaped samples such as turnings and granules.
LIBS systems are capable of measuring large or small sam-
ples because the laser is focused to a smaller area (on the
order of 1 mm). For the handheld LIBS instruments, the
laser is focused at the leading edge of the analyzer such that
the sample should be in contact with the instrument. The
only limitation to the sample size is the user’s ability to con-
veniently hold and position the analyzer to the sample. Op-
erators only need to touch the instrument outlet to the
desired sample area and squeeze the trigger. Typical analy-
sis lasts approximately one second and measurement re-
sults are shown on the screen.
Conclusions
Mobile OES and handheld XRF analyzers have been
around for decades, and the core components have vastly
improved in performance and accuracy, putting them on
par with laboratory versions of the same technology.
These instruments can be used in new applications due
to user interface improvements and minimal mainte-
nance requirements.
LIBS is just now entering a new handheld format,
which presents both obstacles and opportunities for con-
tinued development. As LIBS continues to mature, manu-
facturers will go through similar learning curves to XRF
and OES technologies. They will continue to offer the abil-
ity to measure a wider range of elements and materials, an-
alyze many different sample types such as powders and
liquids, measure materials at longer distances from the
sample, and implement new accessories that facilitate op-
eration and analysis. As LIBS components continue to get
smaller and become more capable, there is hope that hand-
held LIBS units will approach the performance of their lab-
oratory counterparts.
For more information:
Matt Kreiner is business development
manager, Oxford Instruments Industrial Analysis, 300 Baker
Ave., Suite 150, Concord, MA 01742, 978/369-9933,
matthew.kreiner@oxinst.com,
www.oxford-instruments.com.