Sample Preparation

Sample Preparation
The entire process of material characterization can be divided into three areas: (1) selecting a representative sample, (2) the analytical process and (3) extracting meaningful information from the analytical data.

The Frontier pyrolyzer utilizes a deactivated stainless steel sample cup to hold the sample. Using a cup simplifies the process and enables the analyst to employ more advanced techniques, such a Reactive pyrolysis, to extract information about the sample. However, many analysts seem to be unaware of the many variables inherent in the use of a sample cup. Factors such as the physicality of the samples (i.e. thin film, thin slice, sphere, pellet, “chunk”, etc.) and the volatility of the target compounds play a significant role in the ultimate usefulness of the data.

Selecting a representative sample
Micrograms of material are normally needed for an analysis. Because of the small sample size, the importance of how the sample is selected is of great importance. If the sample is not homogeneous (e.g., recycled paper), it may be necessary to analyze aliquots from different areas of the sample.

The physicality of the sample
As a general rule the higher the surface area (SA) to sample weight (SW) ratio, the higher the data quality. This minimizes the time necessary to transport molecules to the surface; thus, minimizing any unwanted or unexpected change in the sample as it is heated. Solid samples can be powdered, cryo-milled or ground into small particles in order to improve the SA/SW ratio.

Volatile additives and residual solvents, monomers, etc. require the opposite approach. The goal is to minimize the SA/SW ratio in order to minimize losses due to evaporation prior to analysis. Thus, chunks are better than slices, which are better than thin films.

The art of the technique, when using the Frontier pyrolyzer and the sample cups, lies on the sample prep side of the equation. As is often the case, it comes down to the nature of the sample, the chemical and physical characteristics of the target compounds and ultimately: Why is the sample being analyzed and what are the data quality objectives (DQO)


Magic Chemisorber Solid Phase Extraction Element (SPEE)
The Magic Chemisorber is used in conjunction with the multi-functional pyrolyzer, model 2020iD, to analyze trace-level organics in air or aqueous solutions. It can also be used to concentrate organics in the headspace of solids and liquids. The pyrolyzer is operated in the thermal desorption mode. The Chemisorber is available in two lengths, 6mm and 30mm. The 6mm tube is used with the standard 80 L sample cup; the 30mm tube requires a special sample cup.
The Magic Chemisorber is a 6mm titanium tube (1.6mm o.d., 1.4mm id) whose surfaces have been deactivated using the same technology used in Frontier Laboratories’ high performance Ultra ALLOY capillary columns. Dimethylpolysiloxane is bonded directly to the deactivated surface of the tube. The outer diameter film thickness is 500 or 100 m and inner diameter thickness is 1 m. A 30mm Chemisorber has five times the capacity of the 6mm tube. This longer tube is especially useful for trace analysis.
Magic Chemisorber
Solid phase extraction element bounded thick dimethylpolysiloxane onto outer surface of a stainless tube.

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