Operation
HS 55 (Batch Mode)
36
¡
If possible, treat standards and samples identically. When arsenic standards age,
As(+V) ions form in the solution due to reaction with atmospheric oxygen.
Suggestion for preparing the solutions
Reduction agent
Solution
Preparation
Shelf life, comments
Master solution
3.0 % NaBH
4
+ 1.0 % NaOH
Dissolve 7.5 g NaBH
4
+
2.5 g NaOH (pellets) +
250 ml H
2
O (dist.)
in an ultrasonic bath
Approx. 4 …6 weeks (refrig-
erated at ≤7 °C)
Reduction agent
1.0 % NaBH
4
+ 0.3 % NaOH
100 ml of the master solu-
tion +
200 ml H
2
O (dist.)
Approx. 1 …2 weeks (refrig-
erated at ≤7 °C)
Hydride method standards
Solution
Preparation
Shelf life, comments
Solution 1 (commercial
standard solution)
1000 mg/l As
See manufacturer specifica-
tions
Solution 2
1 mg/l As
100 µl of solution 1 +
7 ml HCl (37 %, p. a.)
Fill up with H
2
O (dist.) to
100 ml.
Stable for several days.
Prepare standards by means
of a dilution series.
Standards
0 / 2.0 / 4.0 / 6.0 / 8.0 /
10.0 µg/l As
Example: 10 µg/l As stan-
dard
1 ml of solution 2 +
7 ml HCl (37 %, p. a.) +
1 ml KI/ascorbic acid solu-
tion
After 45 minutes, fill up with
H
2
O (dist.) to 100 ml.
Prepare the standards fresh
on a daily basis.
HydrEA method standards
Solution
Preparation
Shelf life, comments
Solution 1 (commercial
standard solution)
1000 mg/l As
See manufacturer specifica-
tions
Solution 2
10 mg/l As
1 ml of solution 1 +
7 ml HCl (37 %, p. a.)
Fill up with H
2
O (dist.) to
100 ml.
Prepare standards by means
of a dilution series.
Solution 3
100 µg/l As
1 ml of solution 2 +
7 ml HCl (37 %, p. a.)
Fill up with H
2
O (dist.) to
100 ml.
4 … 5 days
