How do you calculate how much metal scavenger to use?

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To get an effective metal removal, the amount of SiliaMetS Metal Scavenger used is very important. You can determine by two different ways how much scavenger will be needed:

• from the residual concentration (more accurate method)
• from the amount of metal catalyst used (when the residual metal concentration is unknown)

From residual metal concentration (ppm)

Knowing the palladium (Pd) level in 800 g of material is 500 ppm, (the oxidation state does not affect the calculation).

Data needed:

• Loading of the scavenger (SiliaMetS Thiol): 1.2 mmol/g
• Metal molecular weight: Ex. Pd = 106.42 g/mol
• Amount of product to be treated containing the Pd: Ex. 800 g
• Residual concentration of metal: Ex. 500 ppm of Pd

1. Determine the amount of palladium to be scavenged

2. Calculate the amount of scavenger (SiliaMetS Thiol) to use (1 equivalent)

To scavenge 400 mg of palladium, 3.13 g of SiliaMetS Thiol is needed if ­using only one equivalent. However, it is highly recommend trying a minimum of 4 equivalents at first. In this case, the amount of SiliaMetS Thiol will be 4 times higher (4 x 3.13 g = 12.40 g).
Sometimes, the metal residual concentration is unknown. In such a case, the amount (g) of palladium to be scavenged can be replaced by the amount of metal catalyst used for the ­reaction.

From amount of metal catalyst used

Data needed:

• Amount of metal catalyst used: Ex. 10 g of Pd(PPh₃)₄
• Metal catalyst molecular weight: Pd(PPh₃)₄ = 1155.56 g/mol

1. Determine the amount of palladium to be scavenged

The amount of SiliaMetS Thiol to be used can then be determined as stated above (see point 2. above). In this particular case, one equivalent of SiliaMetS Thiol ­corresponds to 7.20 g.­