by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : June 2009
TECHNOLOGIES & TECHNIQUES FIGURE 3. Manual headspace vial heater. Today, instead of canning jars, we use much easier-to-handle 20ml headspace vials with aluminum-crimp seals, and smaller fi lm sections (typically 100sq. cm.). The operator, however, still must control sample heating temperature and time, withdraw an accurate sample from the heated vial, and inject it into the GC. The main advantage of the manual headspace technique is that it costs less and requires relatively simple hardware. All that is needed are headspace sample vials and septum seals, a gas-tight syringe and a way to heat the sample. One of the disadvantages of manual headspace is that the technique is not very precise. In addition, it is operator intensive, requiring the operator to be involved in the entire process. Additionally, he/she must also handle the hot sample vial and gas-tight syringe. The vaporized solvents in the heated headspace gas sample will condense onto the inner wall of the gas-tight syringe if the syringe is not heated. They will also condense out of the headspace if the operator takes gloves, removed the heated jar from the lab oven and using a gas-tight syringe removed a known amount of the headspace vapor from the heated jar. The heated sample of typically 1 to 2ml was immediately injected into the GC injection port and the GC analysis started. too much time in getting the hot sample from the headspace vial injected into the GC. Reuse of the glass sample vials can also lead to sample carryover problems. The manual headspace technique is, however, used extensively where cost is an issue and where only a small number www. f le xography. org JUNE 2009 FLEXO 27
Sustainable Spring 2009