Analytical Instrument Documents

We examined different parts of a hot pepper to determine which part of the pepper contains the highest concentration of capsaicin. Different sections of the pepper were placed between the DART and the AccuTOF orifice. Little capsaicin was found in the fleshy part of the pepper; higher concentrations were found in the pepper seeds. The highest concentration of capsaicin was found in the membrane inside the pepper pod onto which the seeds are attached.

Organometallic compounds play an important role in chemistry, as recently recognized by the awarding of the 2005 Nobel Prize in Chemistry to Chauvin, Schrock and Grubbs. Characterization of organometallic compounds by mass spectrometry can sometimes be complicated by problems with solubility and reactivity. Electron ionization can be used for some voltatile organometallics. Fast atom bombardment (FAB) and electrospray ionization (ESI) are useful provided suitable solvents can be used. Field desorption (FD) is often effective, but FD emitters can be fragile and the analysis should be carried out by an experienced operator. DART (Direct Analysis in Real Time) complements these methods and provides an alternative; it is fast and does not require solvents. The sampling area is purged with an inert gas, reducing the likelihood of undesirable reactions. Further, AccuTOF-DART permits exact mass measurements without requiring the presence of a reference standard during the sample measurement. DART is extremely robust and does not require special operator training.

The AccuTOF™ equipped with Direct Analysis in Real Time (DART™) is capable of analyzing drugs in pills and capsules with no sample preparation. In most cases, the pill can simply be placed in front of the DART and the active ingredients can be detected within seconds. This application note shows a wide variety of pills that have been analyzed by using DART. The examples include prescription drugs, over-the-counter medicines, and illicit drugs that were confiscated by a law-enforcement agency.

Caffeine (Figure 1), a xanthine alkaloid acting as psychoactive stimulant and mild diuretic in human, is an integral part of diet of many people. It is often found in natural products such as tea, coffee and cocoa beans, cola nuts and many others. Analysis of caffeine in various foods and beverages is an important task for analytical laboratories, as its content is considered in assessment of product quality (coffee, cocoa beans and tea). Due to its physiological effect, the amount of caffeine is regulated in selected foods in EU. Maximum limits are set for some soft drinks to which caffeine is added. HPLC methods employing UV detection are commonly used for its control. While for soft drinks and coffee/tea infusions, the sample preparation is not too much time demanding, LC separation of sample components becomes a limiting step in laboratory throughput. Employing AccuTOF-DART system offers straightforward examination of caffeine content in tens of samples per hour, thanks to omitting separation step. Isotope dilution is used for target analyte quantification.

DART can be used with a heated gas stream to rapidly pyrolyze and identify low-volatility materials such as adhesives and resins, directly on surfaces. Although these materials are not pure compounds, a library of DART mass spectra can be created and searched to identify materials, and exact mass measurements coupled with accurate isotopic abundances can be used to identify unknown components. Examples are shown here for cured and uncured epoxies and acrylate adhesives on metal and glass.

Every cook knows that chopping onions releases chemicals that cause eye irritation. The lachrymator released by chopped onions and related plants is formed by the action of a pair of enzymes on a cysteine derivative to ultimately form propanethial S-oxide (C3H6SO), the compound that causes eye irritation.

The explosive peroxide compounds triacetone triperoxide (TATP) and hexamethylenetriperoxide diamine (HMTD) are difficult to detect by conventional mass spectrometry methods. These compounds can be easily detected by the Direct Analysis in Real Time (DART™) ion source.

According to a recent report in Nature, freshly pressed extra-virgin olive oil contains a compound, oleocanthal, that has properties similar to the common anti-inflammatory drug, ibuprofen. We used DART to rapidly examine cooking oils for the presence of this compound. Fresh-pressed extra-virgin olive oil from a specialty food store was compared with a medium-quality grocery-store brand. Sesame oil and a low-quality spray-on cooking oil were also examined. No sample preparation was required.

Tomatoes are rich in lycopene, a hydrocarbon antioxidant that is the source of the red coloring in ripe tomatoes. The potential benefits of nutritional antioxidants such as lycopene have received a great deal of attention in the popular media. A piece of tomato skin was placed in front of the DART and the positive-ion mass spectrum was recorded.

There has been a recent trend in mass spectrometry towards the development of “open-air” ionization sources. These techniques allow for the rapid analysis of samples at atmospheric pressure with little or no sample preparation. The Direct Analysis in Real Time (DART™) ion source, which is ideal for the analysis of small molecules, represents the first and simplest of the open-air techniques.1 This source creates ions based on the interactions of long-lived excited state neutral atoms or molecules (“metastables”) with the sample and atmospheric gases.