Analytical Instrument Documents

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.

The AccuTOF-DART™ was recently applied to an unusual analytical problem: finding the cause of oily stains on freshly laundered shirts (Figure 1). No cutting or extraction was required. Stained and unstained regions of the shirt were placed in the DART gas stream and the mass spectra were acquired.  The DART parameters were: helium gas, flow 3-4 LPM, gas heater set to 175 degrees C, positive-ion mode, PEG 600 exact mass reference standard. These conditions did not damage the shirt.

Drug counterfeiting is becoming a serious and widespread public health problem. The number of FDA open investigations into drug counterfeiting rose sharply from 2000 to 2001 and has remained high in recent years. Counterfeit drugs are not only illegal, but dangerous; they may contain little or no actual drug content, or they may contain completely different drugs with potentially toxic consequences. The problem is worldwide; it has been reported that nearly 50% of all anti-malarial drugs in Africa are thought to be counterfeit. Direct Analysis in Real Time (DART™) offers a simple solution to screening for counterfeit drugs. DART can detect the presence or absence of drugs in medicines within seconds by simply placing the pill or medicine in front of the mass spectrometer. In combination with the AccuTOF, DART provides exact masses and accurate isotopic patterns that provide elemental compositions for known and unknown substances.

Gamma hydroxybutyrate (GHB) is a fast-acting central nervous system depressant. Prior to its ban by the FDA in 1990, GHB was sold in bodybuilding formulas. It has been abused as a euphoriant. Because it is colorless and odorless, it can be added to alcoholic drinks of unsuspecting victims. An overdose can result in serious consequences, including respiratory depression and coma. GHB was classified as a Schedule I Controlled Substance in March, 2000. Detection of GHB is problematic. GC/MS and LC/ MS methods are time consuming. A rapid colorimetric assay for GHB has been developed, but this assay suffers from some limitations. For example, ethanol produces the same colorimetric response as GHB. The AccuTOF™ mass spectrometer equipped with Direct Analysis in Real Time (DART™) can rapidly detect GHB anion (C4H7O3 -, m/z 103.0395) on surfaces, in urine, and in ethanol. No solvent extraction, wipes, or chromatography are required. Examples are shown in the figures below.

Poppy seed is a common flavoring ingredient that is known to contain small amounts of opiates. Maximum morphine and codeine concentrations are estimated to be about 33 and 14 micrograms respectively per gram of seed. Consumption of typical amounts of baked goods containing poppy seeds has not been shown to cause any ill effects. However, ingestion of poppy seeds may result in false positives from drug tests. Single poppy seeds from different sources were analyzed independently in two different laboratories by using the DART™/AccuTOF™ combination. The resulting mass spectra were nearly identical.

The widespread presence of illicit drugs on currency is an indication of the extent of the worldwide substance abuse problem. Remarkably, cocaine can be found on virtually all one-dollar bills in the United States — the upper limit for the general background level of cocaine is estimated to be 13 ng per bill. The Direct Analysis in Real Time (DART™) ion source, combined with the AccuTOF™ mass spectrometer can be used to sample drugs on currency within seconds. No sample preparation (extraction, wipes, etc.) or chromatography is required. The bill is placed in front of the DART and the presence of drugs can be detected immediately. Only a small portion of the bill is sampled at any given time. This allows the analyst to view the distribution of drugs on the surface of a bill, and allows the bill to be retained for reexamination at a later time.

The detection of explosives is of vital importance in forensic applications and in preventing criminal or terrorist activity. The analytical detection of explosives on surfaces is normally done by using solvent extractions or wipes and chromatography or chromatography combined with mass spectrometry. This is inefficient because solvent extractions and wipes only result in a partial transfer of material from the surface into the sampling material. Furthermore, the chromatographic analysis can be time-consuming and requires the use of disposable solvents (an environmental concern). The JEOL AccuTOF™ with Direct Analysis in Real Time (DART™) has demonstrated the capability to detect both volatile and involatile explosives on surfaces such as plastic, cloth, concrete, glass, cardboard, metal, and more. No wipes or solvent extractions are required. The method is instantaneous, environmentally friendly, and does not require solvents. An example is shown in this application note.