Analytical Instrument Documents

Solid phase microextraction (SPME) is a well established sampling technique that is often used to isolate volatile organic components in gaseous mixtures. Once the compounds have been collected, the SPME fibers are typically placed into a heated GC inlet which thermally desorbs these components into a GC-MS system for analysis. Normally, this analysis can take between 10 and 30 minutes to complete depending on the complexity of the samples. In this work, the Direct Analysis in Real Time (DART™) heated gas stream is used to desorb and directly introduce a SPME sample into a high-resolution mass spectrometer. This methodology produces comparable information to the traditional GC-MS technique but streamlines the results into only a few seconds of analysis time.

Direct control of solid materials for pesticide residues is a challenging task enabling fast contamination screening. In our study, we investigated direct analysis of strobilurin fungicides in milled wheat grains. Strobilurins, systemic pesticides originated from natural fungicidal derivatives, play an important role in control of various plant pathogens. Because of their unique protective properties, significant yield enhancements and longer retention of green leaf tissue, strobilurins have been widely used in agriculture since their introduction on the market in 1992. As other pesticides, these compounds are involved in control and monitoring surveys underta

Smokeless powders are often used in improvised explosive devices. The formulations for smokeless powders vary between manufacturers and between brands from a given manufacturer; ingredients include energetics, stabilizers, plasticizers and deterrents. Both chemical composition and morphology are important in characterizing smokeless powders. Chemical analysis of smokeless powders can provide valuable forensic evidence. Observation with the SEM can reveal morphological information to help with identification. Here we show how SEM-EDS analysis can be used to identify inorganic components, and how the AccuTOF-DART mass spectrometer can rapidly identify the organic components and provide a chemical fingerprint that can be used to identify individual powder particles.

Recent events have led to the recall of both pet food and dairy food products from international consumer markets. In both cases, melamine was added to these products to show a higher chemical signature for proteins, which in turn would increase the reported quality of the food. Unfortunately, the effect of this melamine addition caused the death of both pets and babies that consumed these tainted products. As a result, there is growing government and consumer concern towards the presence of melamine in food products. Because of this concern, there is a need for a rapid and accurate test to quickly determine the presence of melamine in these food products. Previously, the JEOL AccuTOF-DART was shown to be an effective technique for determining the presence of melamine in pet food. In this work, we extend the application of AccuTOF-DART to show that melamine can be rapidly detected when it is present in dry nonfat milk.

Thiabendazole is an anthelmintic and a highly persistent systematic benzimidazole fungicide that is widely used for controlling spoilage in citrus fruit. It is considered a General Use Pesticide (GUP) in EPA Toxicity Class III – Slight Toxicity. A small piece of orange peel (a few square millimeters in size) from a Florida orange was placed in the DART sampling region. Compounds present in the peel were detected within seconds. Among these were the familiar orange-oil flavor components such as limonene and sinensal as well as polymethoxylated flavones that are attributed with antioxidant and cholesterol-reducing properties.

Analytical chemists are often asked to identify trace components in manufactured compounds such as drugs, consumer products, and agricultural chemicals. A common approach to the identification of minor components is to use gas or liquid chromatography coupled with high-resolution mass spectrometry. Although this approach is effective, it may be time consuming and difficult to set up. The AccuTOF with Direct Analysis in Real Time (DART™) provides a rapid solution. The high dynamic range of both source and detector permit the determination of minor components in the presence of a major component. The AccuTOF always provides high resolution data with exact mass measurements and accurate isotope ratios that can provide elemental composition assignments for unknown compounds.

p-Phenylenediamine (PPD) and derivative compounds are commonly used as antioxidants and antiozonants in black rubber. These compounds can cause sensitization leading to contact dermatitis in susceptible individuals. Detection of additives in polymers such as rubber can be important for clinical, forensic, and manufacturing applications. Here we show that DART can be used to identify the presence of these compounds within seconds without requiring any solvents or sample preparation.

DART™ can be used to analyze polymers, cements, resins, and glues by increasing the gas temperature to 450-550°C to induce pyrolysis. This has been applied to a variety of glues and resins, including epoxies, polyimide resins, PVD cement, and cyanoacrylates. Examples are shown here for cured and uncured epoxy resin and cyanoacrylate glues. The DART was operated with helium in positive-ion mode. The gas heater was set to 475°C. Resins were cured in an oven for several hours before analysis; some resin samples had been cured for longer periods of time (months or years). Exact masses and accurate isotopic abundances were used to assign elemental compositions for peaks in the mass spectra. Nominal-mass spectra were exported into a library database in NIST format to facilitate identification of unknowns.

Samples and a polar solvent such as methanol are deposited onto a porous substrate such as filter paper or chromatography paper cut into a triangle. When a high voltage (typically ~3000V) is applied, Electrospray Ionization (ESI) occurs at the tip of the paper triangle. PaperSpray is simpler than ESI and does not require a pump, spray needle, desolvating gas or precise alignment.

Dietary fats are categorized according to the level of unsaturation. Oils are a mixture of triglycerides and free fatty acids. Olive oil contains a high concentration of monounsaturated fatty acids, while other oils such as Canola and safflower oil contain larger amounts of polyunsaturated fatty acids. Characterizing the type of lipids present is important for quality control and for detecting adulteration of more expensive oils (e.g. olive oil) with cheaper products. Analysis by HPLC is time consuming and requires solvents and consumables. DART provides a convenient alternative: no solvents are required and the analysis can be completed in seconds.


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