Analytical Notes
66 Agilent Vapor Generation Accessory VGA 77 and VGA 77P User’s Guide
NOTE
To prepare the SnCl
2
solution, add SnCl
2
crystals to concentrated HCl and warm
the mixture on a hot plate to complete dissolution before adding the water. A
piece of granulated tin added to the mixture will reduce any Sn
IV
to Sn
II
and
produce a clear solution
NOTE
Mercury suffers from memory effects as it adheres to plastic. Keep
concentrations low to minimize these memory effects.
An alternative method for mercury determination with AA uses the
NaBH
4
reduction procedure. In this method, it is preferable to use a
lower concentration of sodium borohydride than would normally be
used for the hydride-forming elements. The concentration of acid
pumped through the VGA 77 system is generally not critical.
For ICP analysis, ensure the spray chamber drain is clamped to avoid
loss of the mercury analyte.
Reductant container: NaBH
4
0.3% w/v
NaOH 0.5% w/v
Acid container: 5 M HCl
A lower analytical signal may be obtained with this method than with
the stannous chloride method.
Selenium
NOTE
If arsenic and selenium are both to be determined see Page 69 ‘Additional Notes’
at the end of this section.
The selenium in the sample must be in the inorganic form, otherwise
digestion will be necessary.
If digestion is necessary, use acid digestion, or ashing with an
appropriate ashing aid. Simple dry ashing is not recommended
because selenium is highly volatile and recovery will be poor.
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