Analytical Instrument Documents

The Direct Insertion Probe (DIP) option permits rapid analysis of solid or liquid samples without gas chromatography. Samples contained in a disposable glass capillary are introduced with the DIP directly into the Q1500 ion source through a vacuum lock. The DIP temperature can be programmed for fast or slow heating to desorb or pyrolyze samples for analysis. In this example, we use the DIP to detect additives in a low-density polyethylene storage bag.

Fermenters used for home beer brewing are fitted with an airlock consisting of a liquid barrier that permits the fermentation gases to escape while preventing contamination from atmospheric microbes. Large volumes of carbon dioxide are produced during the most vigorous stages of fermentation, which can occur as early as the first 24 hour period after an ale yeast is added (pitched) to the sweet liquid (wort) produced from barley during the initial mashing step. The gases emitted from the airlock can have a pleasant aroma that can be quite distinctive during the initial stages of fermentation. Solid-phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MS) was used to determine the volatile components contained in the fermentation gas.

Electron ionization (EI), a hard-ionization technique that generates many fragment ions, is the most widely used ionization technique in gas chromatography–mass spectrometry (GC-MS). Since EI mass spectra have good reproducibility, qualitative analysis is possible by comparing an EI mass spectrum of a sample with that of the known compound recorded in the database. However, sometimes EI mass spectra lack molecular ions, which are of key importance to molecular-weight (MW) determination and correct compound assignment. Soft ionization is a useful way to determine MW. The JEOL JMS-Q1500GC offers two soft-ionization techniques: chemical ionization (CI) and photoionization (PI). In this application note, the MW information of diethyl phthalate and n-tetradecane were estimated from measurement results using both of these soft-ionization techniques.