Sample Preparation; Coning And Quartering; Placing The Sample In An Xrf Sample Cup - Thermo Scientific XL2 User Manual

Sample Preparation

Coning and Quartering

Placing the Sample in an XRF Sample Cup

Thermo Scientific
Prior to analysis, the material should be dry and well homogenized. Ideally, the entire sample
should be dried to constant weight, sifted to remove gravel and debris, and ground or milled
to a fine powder. Dry the sample if it is moist and cohesive. The sample can be dried in any of
several ways. Choose one of the following:
• Oven dry the sample for approximately 2 hours at 150° C, until the sample reaches a
constant weight. Note: Oven drying is inappropriate when volatile compounds may
be present in the sample. For example, lead present as tetraethyl lead would be driven
off by the heat of drying. Some forms of mercury and arsenic are volatile. Air drying
will preserve more of these volatile substances.
• Air dry the sample overnight at room temperature in a shallow pan.
• Stir gently and warm the sample in a pan over a hot plate or burner.
You may need to divide your sample at various times during preparation. Coning and
quartering is a method for dividing the sample into homogenous quarters.
• Pour the dry material slowly and carefully onto a flat sheet or pan, forming a
symmetrical cone. Divide the cone into equal piles using a flat thin-bladed tool, such
as a knife or ruler. Divide these in half again.
• Now you have four samples, each one-quarter the size of the original and each more
homogenous than the original.
• Grind the sample to break up dirt clods and/or paint chips.
WARNING Grinding and sifting dried samples produces dust. Even clean soil contains silica,
which may be hazardous when airborne. Prepare all samples in a ventilated area; wear a mask,
gloves, and an apron; and spread a drop cloth.
Sift using the #10 (2mm) mesh and separate out the larger pieces (stones, organic matter,
metallic objects, etc. Examine the larger particles by eye but do not include in the sample.
Grind the sample again so its particles will be finer and more homogenous. Use mortar and
pestle, or an electrically powered grinding mill. Sift at least 10 grams of the sample through
#60 (250 ?m) and #120 (125 ?m) mesh. Re-grind the un-passed material until the entire
fraction is able to pass. Mix the resulting sample.
Note The sample container should be a sample cup of a type that can be filled from the rear;
that is, the side opposite the window (e.g. Thermo NITON Part Number 187-466). Thermo
recommends using a 1/4 mil Polypropylene film (e.g. Thermo NITON Part Number
187-461). A supply of cups and films are included.
5
Common Operations
Soil Sample Prep
Niton XL2 Analyzer User's Guide 61