1-Liter Degassed
DI Water.
Reagent 1:
Indicator solution.
250 mL
of 0.02 M Ammonium Molybdate solution.
750 mL
Degassed DI Water.
A volume of
~1 M Hydrochloric Acid corresponding to
0.33 mol acid equivalents. For example,
330 mL of 1.000 N HCl, or 333 mL of
0.990 N HCl.
0.02 M Ammonium
Molybdate solution:
25.0 grams
Ammonium
molybdate tetra-hydrate [1235.81 FW].
Dissolve in water under gentle warming
and dilute to 250 mL. Filter. Make sure
the filter is free of silica (do not use
glass filters). Adjust pH to 7-8
with silica-free NaOH (approx. 7-8 mL of
50% NaOH). Store in a plastic container.
Reagent 2:
Reducing Agent & Phosphate Suppressant
solution.
250 mL
of 0.15 M Oxalic Acid solution.
750 mL
of [0.23 M ascorbic acid solution with
1.3 mL sodium dodecyl sulfate] solution.
0.15 M Oxalic Acid
solution: 18.75 grams
Oxalic acid dihydrate [126.07 FW].
Dissolve in water and dilute to 250 mL.
Store in a plastic container.
0.23 M Ascorbic Acid with 1.3 g/L Sodium
Dodecyl Sulfate: 30 grams
Ascorbic acid
[176.12 FW] plus
1
grams Sodium dodecyl sulfate
[288.38 FW] surfactant
(Sigma-Aldrich 436143-25G)
0.75 Liter Degassed DI Water. Place
the ascorbic acid into a 1-liter
container and mix with 500 cc of DI
water until dissolved.
Add the sodium dodecyl sulfate
and mix slowly (prevent foaming) until
dissolved.
Fill the container to 750 mL.
Transfer solution into an
airtight light sensitive glass bottle
for maximum longevity.
Minimize exposure to air and
prepare fresh weekly since this solution
is unstable.