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SiliaMetS Metal Scavengers Leaching & Stability Studies

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To address the end users concerns for potential leaching of impurities into reaction mixtures using SiliaMetS, we have performed three typical metal containing reactions. We then investigated the detection, identification, and quantification of possible impurities resulting from the scavengers used.

Transition metal catalyzed reactions performed

The following three transition metal catalyzed reactions were performed:


Experimental Procedure

Crude reaction mixtures (8 mL) were placed in a standard polypropylene tube equipped with a 20 µm frit and filled with 1 g of the appropriate SiliaMetS Metal Scavenger and mixed for 4 h at either room temperature or 80°C. Solutions were then filtered through a 0.02 µm filter prior to analysis.


Leaching Analysis

For each SiliaMetS, silanes leaching was analyzed by ICP-OES which has proven to be very sensitive for silicon quantification (detection limit in solution is 0.125 ppm). Traces of non-silicon containing impurities were also analyzed by GC-MS and 1H NMR Analysis. Only results for SiliaMetS Thiol and DMT are shown. However, no evidence of any impurities was found for allSiliaMetS. Contact us to get the complete study.


Gel Purity Calculation Example


Silanes Leaching Analysis by ICP-OES

Results shown in the table below for SiliaMetS Thiol & DMT confirm that minimal leaching occurs with SiliCycle SiliaMetS.

Note: concentration given are in ppm and represent mg of silicon leached per kg of SiliaMetS.

Stability of SiliaMetS in Suzuki, Stille and Ring-Closing Metathesis reactions
Reaction (solvent) Temperature SiliaMetS Thiol SiliaMetS DMT
[Silicon] Gel Purity [Silicon] Gel Purity
Suzuki (Toluene) 22°C 2 ppm 99.9998 % 1 ppm 99.9999 %
80°C 2 ppm 99.9998 % 2 ppm 99.9998 %
Stille (1,4-Dioxane) 22°C 2 ppm 99.9998 % 1 ppm 99.9999 %
80°C 1 ppm 99.9999 % 3 ppm 99.9997 %
Ring-Closing Met (DCM) 22°C 2 ppm 99.9998 % 2 ppm 99.9998 %
Note: Very low levels of silicon were detected in most experiments, giving products purity higher than 99.995 %.

Non-Silicon Leaching Analysis

Gas chromatography-mass spectrometry (GC-MS) 1H NMR Analysis (d6-dmso)
leaching-study-gc-ms leaching-study-d6-dmso

Compared to the silica blank spectrum (bare silica in solvent), neither experiment showed evidence of any impurities for either SiliaMetS Thiol or DMT.

Note: each experiment was ran on a 1 g aliquote of SiliaMetS and was shaken for one hour at room temperature. In GC-MS spectrum, peak at 8.5 minutes is the internal standard (1-fluoronaphthalene, 100 ppm). In NMR spectrum, peaks at 2.4 and 3.4 ppm are, respectively, d6-dmso and water contained in deuterated solvent.

Stability Study (Shelf Life)

SiliCycle certifies that SiliaMetS Metal Scavengers stored under recommended conditions in an undamaged container are guaranteed to perform for over two years from the manufacturing date without loss of performance, prouved by results at right.

SiliaMetS Thiol after Two Years
Lot # QC Date Scavenging
11577 January 2008 > 99.9 %
October 2010 99.6 %
12218 February 2008 99.9 %
October 2010 99.1 %
Scavenging: 1 000 ppm of Pd(OAc)2 in DMF.
Conditions: 2 eq. of SiliaMetS Thiol, 1 h, 22°C.

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