Traditional measures of molecular mass (and the standards
derived from them) have been either absolute, but applicable
to only one moment of a distribution (e.g. light scattering,
osmometry), or relative, but applicable to the entire distribution
(e.g. chromatography). What is needed is a method (and standards
derived from it) for absolute molecular mass distribution determination.
Objective
Mass spectrometry is being developed as a method to create
absolute molecular mass distribution polymer standards. Although
methods exist to calibrate the mass axis with high precision
and accuracy, the ion-intensity axis is extremely difficult
to calibrate. This leads to large uncertainties in quantifying
the content of mixtures, whether the mixture is composed of
different oligomeric species of the same polymer (molecular
mass distribution), of polymers of the same repeat unit but
having different end groups (especially pre-polymers with reactive
end-groups), or polymers having different repeat units (blends).
We aim to calibrate the ion intensity axis. This means determining
an uncertainty budget including both Type A (“random”)
and Type B (“systematic”) uncertainties.
NIST’s Role
NIST has a national mandate to produce measurement standards
NIST has the expertise in classical methods, as well as in mass
spectrometry, that no other institution possesses
NIST has the visibility in the polymer mass spectrometry industrial
research community to ensure that standard methods and materials
are internationally visible and universally adopted
Outreach
Polymer MS Workshops in 2002, 2003, 2004 to build, sharpen,
and lead our research community
Our web page has over 250 MALDI methods taken from the literature,
a valuable public resource
MassSpectator, our on-line program, serves as a focal point
for data analysis outreach effort
We sponsor international interlaboratory comparisons
Standards setting activities: VAMAS, ISO, ASTM, etc.
Customers and Impact
Customers: producers and users of synthetic polymers, analytical
laboratories, and standards developing organizations
Sponsored workshops feature popular problem-solving sessions
to aid users of MS
Project web page, www.nist.gov/maldi, and its sub-pages have
over 5000 hits in three years
Web tools highlighted in Science, JACS, Analytical Chemistry,
C&ENews
Contributors:
Project Leader: William E. Wallace
Senior Scientist: Charles M. Guttman
Project Team:
Mark A. Arnould
Barry J. Bauer
William R. Blair
H. C. Michelle Byrd
Bruno M. Fanconi
Kathleen M. Flynn
David L. Vanderhart
Stephanie J. Wetzel
Characterization and Measurement Group
Polymers Division
Materials Science and Engineering Laboratory
