Sodium Borohydride Solution Make-up

1. Weigh 5 g of Sodium Borohydride and 2.5 g of KOH into a glass funnel inserted into 250 mL volumetric flask. Add distilled water to rinse the Sodium Borohydride / KOH into the flask. (If you are making a 10 g batch, dissolve the reagents in a beaker prior to transferring to the 500 mL flask.). Bulk and mix thoroughly. Fill the Borohydride reductant reservoir to the max. line. Attach the reductant reservoir to the MHS-10 stand and turn on the Argon gas. Ensure the flow rate does not exceed the bare minimum (flow rate ball should be barely vibrating on the bottom of the scale) otherwise the hydrogen will ignite and burn out of the ends of the quartz cell.
2. Push the plunger and hold for a few seconds to let a little NaBH4 solution run through line into an empty flask. Once the plunger is released, the argon gas should be bubbling in the reductant reservoir and flowing through the cell. If no bubbles appear in the reductant reservoir, remove the reaction flask and plug the end of the reaction tip briefly. Reattach the reaction flask and check for bubbles. This is critical.
3. Let the cell stabilize for 10 minutes with Argon flowing through it.

Sample Preparation

1. Briefly remix the samples and standard. Allow to settle for 5 minutes. Place two reaction flasks in front of each sample flask and arrange an appropriate number of flasks for standards and blanks off to the side.
2. Discard any old HCL left in the burette. Add 10 mL of 25 % v/v HCL into the reaction flask.
3. Add the appropriate aliquot of sample to each reaction flask.

Heads 100 uL Knelson 100 uL
Zn Conc. 50 uL – 100 uL Core 100 uL
Cu Conc. 50 uL Stds. 25 uL, 50 uL