FISHERIES AND MARINE SERVICE Translation Series No. 4511
The use of high-pressure liquid chromatography in
inorganic analysis. III. Determination of
selenium in drinking-, surface- and waste water
by G. Sèhwedti and A. Schwarz
Original title: Zur Anwendung der Hochdruck-Flussigkeits-Chromatog-raphie in der anorganischen Analyse III. Bestimmung von Selen in Tripk-, Oberflachen- und Abwasser.
From: J. Chromatogn160: 309-312, 1978
Translated by the Translation Bureau (KMF) Multilingual Services Division
Department of the Secretary of Stete of Canada
Department of the Environment Fisheries and Marine Service Maritimes Regional Library
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DATE OF PUBLICATION DATE DE PUBLICATION
309 - 312
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DIVISION MULTILINGUES AUTHOR - AUTEURG. Schwedt and A. Schwarz
TITRE ANGLAIS
The use of high-pressure liquid chromatography in inorganic analysis. III. Determination of selenium in drinking-, surface- and waste water.
TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN CARACTÈRES ROMAINS)
Zur Anwendung der Hochdruck-Fliissigkeits-Chromatographie in der anorganischen Analyse III. Bestiinmung von Selen in Trink-, Oberflâchen- und Abwasser.
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Journal of Chromatography
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Journal of Chromatography
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Journal of Chromatography 160 (1978) pp. 309 - 312
The use of high-pressure liquid chromatography
in inorganic analysis.
III. Determination of selenium in drinking-,
surface- and waste water
G. Schwedt and A. Schwarz
(University of Siegen, Department 8 - Analytical Chemistry, Adolf-Reichwein Str. 2, D-5900 Siegen 21
Federal Republic of Germany) Submitted June 14, 1978
Piazine selenate compounds and selenium diethyldithiocarbamate (309) have proven suitable for the high-pressure liquid chromatographic
analysis (HPLC) of selenium with reversed-phase column materials 1-3 . In the following we report on the applicability of these methods for the determination of selenium in drinking-, surface- and waste water.
Experimental part
Instruments for HPLC
HPLC pump type 52.00 (Knauer, Oberursel/Taunus, Federal Republic of Germany), Rheodyne 6-way universal valve with 50 mm3
UNFMTI:r.)
For Inf,,rmation only
TRADUCTPC:IN NON REVE
Information seulernen-?
2 sample loop (Knauer), spectrophotometer type 81.00 (Knauer): single-beam instrument with grid monochromator (8 mm 3 flow-through cell,
10 mm sample thickness), ready-to-use column (Knauer) of alloy steel,
packed with LiChrosorb RP-8 (grain size 10 m), 250 x 4.6 mm inside diameter.
Chemicals
4-chloro-1,2-diaminobenzene tech. grade (Fluka, Buchs, Switzerland); 1,2-phenylenediamine, reagent grade (Merck-Schuchardt,
Munich, FRG); sodiumdiethyldithiocarbamate (trihydrate) analytical
grade (Merck, Darmstadt, FRG); selenium dioxide analytical grade
(Merck); Titriplex III analytical grade (Merck); 98% formic acid analytical grade (Merck).
Solutions
Selenium stock solution: 140.35 mg selenium dioxide is dissolved in 100 ml twice dist. water (= 1 mg Se/ml); 4-chloro-1,2- phenylenediamine solution: 0.1% in 0.1 N hydrochloric acid (dissolve
while heating, filter hot); EDTA solution: 0.1 M Titriplex III;
citrate buffer pH 2.5 : 0.1 M.
(310) Analytical method
After filtering of the water sample (drinking-, surface- or
waste water) 100 ml each is purified by 5 minutes shaking with 30 ml chloroform each. After the addition of 10 ml citrate buffer, 2 ml 98% formic acid and 5 ml EDTA solution, the aqueous phase is reacted with 4 ml freshly prepared 4-chloro-1,2-phenylenediamine solution for
3 10 minutes in a sealed Erlenmeyer flask in a waterbath of 40 ° C. After
cooling we extracted twice for 1 minute each with 10 ml chloroform,
filtered the organic phase through a folded filter into a 10-ml pear-shaped flask and removed the filtrate under reduced pressure at room
temperature. The residue is dissolved in 1 ml methanol for
chromato-graphic analysis.
High-pressure liquid chromatographic analysis
Column: c.f. instruments for HPLC; mobile phase:
methanol-water (80:20); flow rate: 1.5 cm3 /min-1 ; pressure: 75 bar; sample
volume: 50 mm3 ; detector: c.f. instruments for HPLC; detector
sensitivity: E = 1/32; uncorrected wavelength adjustment: 320 nm.
Results and Discussion
Piazine selenates
The temperature dependence of the reaction of selenic acid
with the diamines 1,2-phenylenediamine and 4-chloro-diaminobenzene as
well as the enrichment of the formed piazine selenates were examined
and optimized. Increasing the reaction temperature to 40 ° C permitted
a reduction of the reaction time from 90 to 10 minutes in both cases. If the sample volume of 14 ml (c.f. analytical method in Ref. 1) is
increased to 100 ml enrichment by a factor of 3.5 can be achieved.
However, compared to a volume of 14 ml the recovery rate drops to
approx. 50%).
Under these extraction and reaction conditions the limits of
detection for selenium were determined, with 1/20 of the total amount
4 Analytical method Detection limit Method in mg/1 (ppb) ng in column/ml chloroform Photometric determination as piazine selenate HPLC determination as piazine selenate HPLC determination as 5-chloropiazine selenate HPLC determination as carbamate 5.3 x 10 -3 (5.3) 530 6.8 x 10 -4 (0.68) 6.8 3.2 x 10 -4 (0.32) 1.6 5 x 10-3 (5.0) 25 Table I
Detection limits of various methods of
selenium determination
In 1974 Wheeler and Lott 3 reported on the determination
of selenium after reaction with 2,3-diaminonaphthalin with the aid of
HPLC. The detection range was stated as 10 - 100 ppb for the
detection with a UV photometer or a fluorimeter after reversed-phase
or partition chromatography with carbowa as the stationary phase. The
method with chloro-piazine selenate described here affords a detection (311)
limit of 0.32 ppb (corresponding to 1.6 ng in the HPLC column) for
measurements in the near UV range (340 nm).
Selenium carbamate
In previous examinationsl) we obtained for the determination
of selenium as diethyldithiocarbamate the highest measuring sensitivity
at 30 pg for 1% stylus deflection at 0.005 a.u.f.s.* despite two
5 signals in the reversed-phase HPLC (filter photometer: 254 nm). This
sensitivity could not be achieved with the spectrophotometer used by
us (c.f. experimental part): it lay at 0.56 ng and 0.0156 a.u.f.s. 4 ).
For a more detailed examination of the reaction of selenic acid with sodium diethyldithiocarbamate the two reaction products indicated in the chromatogram were collected in separate fractions and examined for selenium after reaction with concentrated nitric
acid. Approximately 78% of the total selenium was determined in the
first fraction. Even with thin-layer chromatography on silica gel
with benzene as the solvent, two spots were detected after reaction
of selenium to carbamate (RF values: 0.24 and 0.56); these probably
correspond to the different valencies of selenium (II and IV). In the further course of the examinations it also became apparent that
the signal ratio is not constant. Depending on the time of sample
injection measured from the dissolving of the residue of the
chloroform extraction, the second signal increases with respect to
the first although the sum of the areas under both signals remains approximately constant. In order to obtain reproducible results the
samples must therefore be injected immediately after dissolving the
residue.
In contract to the piazine selenates, enrichment of the
selenium carbamate from solution by increasing the sample from 5 to 100 ml aqueous phase causes only a 10% reduction in the recovery rate.
However, very short retention times, i.e. a low retarding effect of the chromatographic system on the first selenium compound
6 in the nanogram range through unspecific absorptions from the
decomposition of the reagent which can not be quantitatively
separated by reversed-phase chromatography. Despite good measuring
sensitivity a more unfavourable detection limit was therefore
obtained with this method than with the determination of selenium as
piazine selenate (see Table I).
Water analyses
The chloro-piazine selenate method with the lowest detection
limit was used for the examination of various water samples.
The drinking water regulation of the Federal Republic of
Germany dated February 15, 1975 5 ) stipulates a permissible limit of concentration of 0.1 mmol/m 3 (i.e. 0.0079 mg/litre or 7.9 ppb). 0.03 mmol/m 3 (i.e. 0.0024 mg/litre or 2.4 ppb) is listed as
permissible error of the measured value 5 ). The prescribed
photometric analytical method as piazine selenate is just able to
detect this limit value with its detection limit of 0.0053 mg per
litre, However, the described method for the determination of
selenium as chloro-piazine selenate with the HPLC exhibits a
detection limit of 0.0003 mg/litre (i.e. 0.32 ppb) which is lower by
a factor of almost 20.
No selenium could be detected in the examined drinking-water
samples. In one sample of surface- and waste water each, selenium
contents of 0.8 and 2.1 ppb were determined (see Table II). For the
determination in waste water a relative standard deviation of 5.5%
was established (c.f. Fig. 1).
7
Water sample Result (ppb)
Drinking water
River water Waste water
Not detectable (below 0.32 ppb) (Peak 1 (2))
0.80 ppb (Peak 1 (3))
2.10 + 0.116 ppb, n = 11 (Peak 1 (4))
Table II
Results of analyses ("5-chloro-piazine selenate method")
Fig. 1
Chromatograms of HPLC determination of selenium as 5-chloro-piazine selenate. For conditions see
experimental part. (1) Blank value; (2) drinking
water; (3) surface water (river water), 0.8 ppb Se;
•I
Literature
d'::,Sciiwedt, Fresenias Z. Anal. Chem., 288 (1 977) 30. 2 G. Schwedt, Chromatographia, 11 (1978) 145.
3 G. L. Wheeler und P. F. Lott, Microchem. J., 19 (1974) 390.
A. Schwarz, Dip/omarbeit, Gesamthochschule Siegen, Siegen, Juni 1978. 5 Bundesgesetzblatt 1975 (B.R.D.), Tell I, 15.2.1975. S. 459ff.
4. Thesis