PNNL-13501 - Pacific Northwest National Laboratory

Study Control Number: PN0004/1411
Advanced Methodology for the Analysis of Organic Components
James A. Campbell, Eric W. Hoppe, Joe W. Brothers
Faster and cheaper methods for the analysis of organic components in tank wastes and other environmental samples are
required for cleanup efforts at DOE sites. Matrix-assisted laser desorption ionization/time-of-flight mass spectrometry is
a promising technique that requires minimal sample preparation, provides rapid analysis, reduces personnel exposure, and
minimizes waste.
Project Description
Analytical techniques for the analysis of chelators,
chelator fragments, and organic acids in radioactive
wastes typically involve derivatization and gas
chromatography/mass spectrometry, which is a timeconsuming
and labor-intensive approach. Derivatization
techniques also produce artifacts related to production of
nitroso compounds. Alternatively, liquid chromatography
has been used for analyis of these constituents in
radioactive wastes but chromatography is hindered by
additional waste generation and by co-elution problems in
complex matrices. In addition, the analytical procedures
for regulatory compounds (semivolatiles, polychlorinated
biphenyls, pesticides) are time-consuming and require
considerable sample preparation methodologies.
The matrix-assisted laser desorption ionization (MALDI)
technique, in combination with time-of-flight mass
spectrometry (TOFMS) allows an entire mass spectrum to
be measured in a single analytical step. Since the MALDI
process produces positive and negative ions directly with
very little sample, MALDI is an efficient micro-sampling
technique that requires minimal sample preparation.
MALDI offers additional advantages including reduced
personnel radiation exposure and minimal waste
production.
We have used MALDI/TOF to examine anions, organic
acids, and chelators that are known to be present in
storage tank wastes. Samples of ethylenediaminetetracetic
acid, N-(2-hydroxyethyl)ethylenediametriacetic
acid, citric acid, nitrilotriacetic acid, and several inorganic
anions including sulfate, nitrate, and nitrite (Goheen et al.
1997) were analyzed using MALDI/TOF. This project
focused on developing MALDI/TOF as a quantitative tool
for analyzing organic components of regulatory interest.
Mixtures of analytes also were analyzed. This research
provides a method that reduces the cost and time required
to perform chemical analyses.
Introduction
We developed analytical techniques for organic
constituents, including phosphate-related components
(tributyl phosphate, dibutyl butyl phosphonate, and bis-
(2-ethylhexyl)phosphoric acid) and chelators in tank
waste. These techniques involve derivatization gas
chromatography/mass spectrometry for the analysis of
chelators and chelator fragments. We also developed ion
chromatography for low molecular weight acids, such as
oxalate, formate, and acetate. With these and other
analytical techniques, we were able to account for 80% to
95% of the total organic carbon in most tank waste
samples.
The above techniques, although providing important
analytical data, are labor-intensive and time-consuming.
We have shown that MALDI/TOF can identify low
molecular mass solids including chelators, low molecular
weight acids, and nitrites. Mass spectra were observed
for the chelator compounds in the positive ion mode and
for the low molecular weight acids in the negative ion
mode. Because of its inherent advantages of limited
sample preparation and minimal waste production,
MALDI/TOF represents an attractive technique for the
analysis of organics in tank waste matrices. The results of
this study will provide the opportunity for a substantial
savings in the cost and time required to perform chemical
analyses.
Approach
Standard solutions of phosphate-related compounds
known to be present in Hanford tank wastes were
analyzed using MALDI/TOFMS. Standard solutions of
the regulatory compounds were also analyzed using
MALDI. We evaluated the efficiency and costeffectiveness
of the MALDI/TOFMS technique for
analyzing these solutions.
Analytical and Physical Chemistry 1