Scribd
Upload
91 views2 pages

Silica Gel Emitter Prep Guide

This document provides a procedure for preparing a silica gel emitter for use in mass spectrometry. Colloidal silicic acid is weighed and diluted with phosphoric acid in a specific ratio. The resulting silica gel solution can be sonicated regularly to keep the silica dispersed. If blanks are too high, the solution can be cleaned by adding anion exchange resin and shaking in a hydrobromic acid solution, which should reduce blanks by at least 50%. The prepared silica gel emitter should yield low lead blanks below 200 fg and ion currents over 10,000 cps per pg.

Uploaded by

Boulos Nassar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
91 views2 pages

Silica Gel Emitter Prep Guide

This document provides a procedure for preparing a silica gel emitter for use in mass spectrometry. Colloidal silicic acid is weighed and diluted with phosphoric acid in a specific ratio. The resulting silica gel solution can be sonicated regularly to keep the silica dispersed. If blanks are too high, the solution can be cleaned by adding anion exchange resin and shaking in a hydrobromic acid solution, which should reduce blanks by at least 50%. The prepared silica gel emitter should yield low lead blanks below 200 fg and ion currents over 10,000 cps per pg.

Uploaded by

Boulos Nassar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
You are on page 1/ 2

Silica gel emitter preparation

Procedure modified from Gerstenburger and Haase, 1997, Chem. Geol.

Materials
0.2 g colloidal silicic acid (Merck)
19.6 g 0.035M H3PO4 (diluted from concentrated orthophosphoric acid)

Method
Using an acid-washed 250µl pipet tip and a clean pipettor, draw
approximately 200 µl of colloidal silicic acid from the very top of the
undisturbed 30 ml bottle of stock solution, and weigh into a tared,
empty, clean 7 ml Savillex beaker.
Dilute the colloidal silicic acid with 0.035M H3PO4 (make sure the
molarity of the dilute phosphoric acid is accurate by titration) in the
weight ratio, 0.2 g silicic acid : 19.6 g 0.035M H3PO4. To do so, weigh
the appropriate amount of 0.035M H3PO4 into a 30ml spaghetti tube-
tipped dropper bottle, and place it in an ultrasonic bath. With your
clean pipet tip, pipet the weighed colloidal silicic acid from your
beaker into the bottle dropwise, allowing the silicic to disperse under
sonication.
The resulting dilute silica gel emitter should yield loading blanks less
than 200 fg Pb, and ion currents of greater than 10,000 cps per pg
(measured on 205Pb spiked loading blanks).
It is recommended to sonicate the bottle of silica gel solution regularly
to maintain the dispersed silica in solution.
If the silica gel solution yields anomalously high blanks, then it can be
cleaned by treatment with coarse anion exchange resin in a dilute HBr
medium as follows:
1) To the ~20 ml of silica gel solution mixed above, add 1.11 mL (1.65
g) of conc. (9M HBr) to yield a 0.5M HBr solution.
2) Starting with dry AG1-X8 20-50 mesh resin, immerse a batch in
MQH2O in a small bottle (e.g. 250 mL), shake and let the coarsest
resin settle before decanting the fines. Repeat the filling, shaking
and decanting of the fines until you have a well-sized coarse resin
fraction.
3) Add enough clean 6M HCl to the bottle to cover the resin, let
equilibrate for an hour, the decant the 6M HCl. Repeat this process
several times, alternating MQH2O and 6M HCl. Finish this
procedure with several rinses of MQH2O prior to storing the resin in
MQH2O.
4) Add approximately 2 mL of wet, sized, clean resin to the silica gel
mixture in 0.5M HBr and recap. Shake this bottle occasionally over
the course of a day and let sit overnight, or place in a automatic
shaker for 24 hours.
5) The next day, decant the silica-gel mixture into a new dropper
bottle, being careful not to transfer any resin to the new bottle. The
cleaned silica gel should have loading blanks reduced by at least
50% compared to the starting composition.

You might also like