The Atomic Absorption Spectrometer RA-915+ was
originally designed as a portable instrument to pin point sources of Mercury
spills and accumulations. The high
sensitivity of the instrument (several ng / m3) is provided by a built in
10-meter multi-pass cell. This instrument does not require any amalgamation or
pre-concentration steps and, therefore, generates real time Mercury values. The
selectivity of the instrument to Mercury is assured by using a single Mercury
isotope lamp along with Zeeman correction. The instrument is also equipped with
a 6-centimeter single pass cell to address high level Mercury contamination.
The instrument also has a built in cell for instant
QC check in the field. It can be operated via its own hand held controller /
reader or using a notebook PC.
This
paper describes the use of this instrument as a detector for continuous
emission Mercury monitoring (CEM). Examples will demonstrate the determination
of trace levels of Mercury in the presence of SO2. It is shown that Zeeman
correction eliminates the effect of SO2 and other UV absorbing gases which can
act as interferences for Mercury determination.
The
instrument can differentiate between elemental and oxidized Mercury by
measuring gases as is and after their passage through a chemical converter,
respectively.
Matrix
Independent Headspace Techniques in the Analysis of Polymeric Compositions
The trace analysis of residual monomers in a variety of polymeric
compositions will be demonstrated using automated headspace dual needle
sampling technique. This methodology was developed and successfully used for
the analysis of Acrylonitrile, 1,3- Butadiene, Butylenes, Vinylcyclohexene,
Isoprene, Phenylcyclohexene and Styrene in several food grade polymers at low
ppb and ppm levels.
It was shown that small variations
in polymeric compositions affect the equilibrium partitioning significantly and
a matrix independent technique has to be used for quantification.
Several techniques were evaluated
and compared, such as Full Evaporation Technique (FET), Variable Volume
Technique (VVT), Multiple Headspace Extraction (MHE) and Method of Standard
Additions (MSA).
The theoretical treatment of the
dual needle sampling as well as several configurations of an automated
headspace instrument will be also presented.
Comparison
of Capillary Electrophoresis with GC and HPLC Methods for the Determination of
Organic Acids in a Variety of Matrices
Tatiana
Besschetnova 1 , Olga Bershevits 2 , Michael
Markelov 2
1Laboratory of Capillary
Electrophoresis (LUMEX), Scientific-Research Institute of Metrology, Moskovsky
pr.19, St.Petersburg 198005, Russia. 2 OhioLumex Co., 5405 E.Schaaf Rd , Independence, Ohio 44131.
While the analysis of organic acids in standard
solutions rarely presents a challenge, the analysis of real matrices, especially
biological ones are associated with a variety of problems. One of the major
problems in the analysis of biological substances by GC is carry over from
sample to sample. Also associated with
biological analysis are instrument problems, such as: the plugging of the
column, the plugging of the injection liner, the absorption of acids on glass,
metal, 2 and connecting
lines of the analytical system.
Analytical methods involving some extraction
procedures are often not applicable due to the limited amount of biological
sample. Limited sample size is also a
problem for HPLC analysis.
Some of these difficulties can be solved using
Capillary Electrophoresis (CE) technique.
This
paper describes the direct and indirect UV detections of Acetic, Propanoic and
Formic Acids at low ppm levels using two CE " Capel-103 " and
"Capel-105" systems.
It
will be demonstrated that good separation of acetic and propanoic acids can be
achieved even with a high background of inorganic anions ( Cl-) which are
usually present in saline solution.
The methodology for the analysis of organic acids by capillary
electrophoresis was developed and evaluated using both electrokinetical and
pneumatic sample injections. The
comparison of the results obtained by CE, GC and HPLC will be presented.
Capillary
electrophoresis for the analysis of inorganic anions in natural and waste water
samples with enormously high concentration of iron.
Tatiana Besschetnova1, Vadim M. Okun2, Jaroslav.S.Kamencev.1, Anatoliy.A.
Krasheninnikov 1
1Laboratory of Capillary
Electrophoresis (LUMEX), Scientific-Research Institute of Metrology, Moskovsky
pr.19, St.Petersburg 198005, Russia. 2 Institute of Analytical
Chemistry, University of Vienna, Waehringerstr.38, A-1090 Vienna, Austria.
High
concentration of iron in aqueous samples can hamper significantly CE analysis
of inorganic anions present in these samples. This is due to the formation of
iron-anion complexes in background electrolyte (BGE), especially in case of fluoride
and phosphate anions. It leads not only to noticeable underestimation of anions
concentration and non-reproducible EOF, but potentially can block the capillary
during analysis.
We propose to
use sample pre-treatment with EDTA which binds iron, thus preventing complex
formation with anions of interest. For the indirect CE mode performed on a
"Capel-103RT" CE system, method development resulted in a BGE, which
was CrO3 titrated by dietanolamine up to pH 9.2 and contained 1.65 mM
cetyltrimethylammonium bromide (CTAB) as an EOF modifier. Proposed sample
pre-treatment for both standard mixture and natural samples provided correct
estimation of all inorganic anions of interest (chloride, nitrite, nitrate,
sulphate, fluoride, phosphate) even when iron concentration was raised up to 50
ppm. Recovery for the most problematic anions (phosphate and fluoride) was
about 98% with the peak area reproducibility not higher than 2.4% RSD.
Suggested
method seems to be a very simple and reliable way to mask the interference of
high iron concentration when using indirect UV detection and basic BGE.