Analytical Instrument Documents

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.

The AccuTOF time-of-flight mass spectrometer equipped with Direct Analysis in Real Time (DART™) has been used to detect a wide variety of explosives in or on a variety of materials ranging from solutions to samples deposited on surfaces ranging from ABS plastic to metal, clothing and cardboard. Detection is rapid, specific, and sensitive.

Please see the following publication: “Versatile New Ion Source for the Analysis of Materials in Open Air under Ambient Conditions” Robert B. Cody, James A. Laramee and H. Dupont Durst, Analytical Chemistry 77 (8), 2297- 2302, 2005

DART provides very simple mass spectra that are free of multiple charging and alkali metal cation adducts such as [M+Na]+  and [M+K]. This facilitates identification of target compounds in mixtures and simplifies assignment of elemental compositions for unknowns.