Thermal Desorption Electrospray Ionization Research Articles

Rapid screening of 15 highly toxic pesticide residues in Angelica sinensis decoctions by thermal desorption electrospray ionization mass spectrometry

ABSTRACT A decoction is the most common form of Chinese herbal medicine dosing. An Angelica sinensis decoction was qualitatively and semi-quantitatively analyzed for 15 highly toxic pesticide residues by thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) with a triple quadrupole mass spectrometer in multiple reaction monitoring mode without pretreatment. The instrument response was optimal and sensitivity was highest with the following parameters: thermal desorption temperature, 300 °C; 0.1% formic acid aqueous solution-methanol (1:1,V:V) solvent; syringe pump flow rate, 150 μL/h; and sampler length, 5 cm. Good linearity was attained within the appropriate linear range with the detection limits ranging from 0.01–0.05 mg/L. The same positive sample was verified for QuEChERS pretreatment coupled with liquid chromatography tandem mass spectrometry, showing good agreement with TD-ESI/MS. The newly developed method was demonstrated to be a rapid, green, and efficient analytical method for screening 15 highly toxic pesticide residues in Angelica sinensis decoctions.

Rapid Identification of Illicit Drugs Using Portable Thermal Desorption – Electrospray Ionization (TD-ESI) Ion Trap – Mass Spectrometry (IT-MS) with Two-Step Scanning

With the increasing prevalence of illicit drugs, social security and human health are at serious risk. However, traditional detection techniques require a lengthy pretreatment process to eliminate matrix interference and do not allow rapid, in situ analysis. Ambient ionization is a powerful tool for the rapid determination of illicit drugs in different matrices because it usually eliminates the need for sample pretreatment, and the portable mass spectrometer brings convenience to in situ detection. This study employed a thermal desorption-electrospray ionization (TD-ESI) source combined with a portable mass spectrometer to rapidly characterize illicit drugs in drinks, instant powders, and solid food surfaces. Air was utilized instead of nitrogen as the carrier gas for TD-ESI/MS in order to save space and cost together with rapid on-site analysis. A full-scan waveform combined with a qualitative pre-scan waveform (QPSW) was employed to form a two-step scanning mode to accurately identify the drugs. The results showed that the limits of detection (LODs) for the analytes were 100–200 ppb in drinks, 700–1000 ppb in instant powders, and 1 ng/cm2 on solid food surfaces. The complete TD-ESI/MS analysis time was less than 1 min.

Rapid Screening of β-Agonists in Animal Hair by Thermal Desorption Electrospray Ionization Mass Spectrometry

Even though the use of β-agonists in livestock has been banned in many countries, β-agonists abuse is still out of control owing to time-consuming and complicated determination techniques. This study applied ambient thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) as a new strategy for rapidly screening seven β-agonists. As it does not require pretreatment, this method allows on-site and real-time detection. Samples were collected directly using a simple metal probe. Analytes on the probe were desorbed and ionized by TD-ESI, after which analyte ions were detected using a triple quadrupole mass analyser. The results showed that a thermal desorption temperature of 320°C and nebulizer pressure of 3 psi demonstrated the highest sensitivity. Excellent linear relationships were obtained in concentrations ranging from 10 to 400 μg/kg. The limit of detection of the method was 1-10 μg/kg with RSDs of 7.2-14.6%. A positive sample was verified using HPLC coupled with triple quadrupole tandem mass spectrometry, consistent with the results from TD-ESI/MS. This method was the first to apply TD-ESI/MS to rapid analyse β-agonists in livestock hair and was proven to be accurate, fast, and environmentally friendly. Because qualitative screening for each analysis was completed within approximately 1 min, the method could contribute to preventing non-compliance in the flow of animal-derived food to the market. This method was a promising method for the rapid screening of β-agonists in livestock hair at any time of breeding without imposing any harm to animal which proven to be a rapid, in situ, and non-destructive detection technique without any pretreatment.

Hand-Held Diode Laser for On-Site Analysis Using Transportable Mass Spectrometry.

A hand-held laser diode thermal desorption electrospray ionization (LDTD-ESI) mass spectrometry (MS) method was developed for rapid screening of illegal substances in solid samples. To achieve that, a simple, inexpensive, battery-powered surgical laser diode at 940 nm was employed to ablate the solid samples. The potential of using a black polytetrafluoroethylene substrate to enhance the analytes’ desorption to the gas phase was investigated and demonstrated. Among the optimized ESI parameters, the solvent (methanol/water, 50:50, v/v) and the flow rate (50 μL h–1) were critical to obtain the best sensitivity. The applicability was demonstrated for the rapid identification of selective androgen receptor modulators (SARMs) in pills and powders based on accurate mass measurements by time-of-flight MS. Also, the hand-held LDTD-ESI was combined with a transportable single quadrupole MS. The same SARMs samples were analyzed, and identifications were based on in-source cone voltage fragmentation patterns observed. These initial results demonstrate the applicability of the developed simplified LDTD-ESI MS method for future on-site testing of organic compounds in solid samples.

Solvent-free, Noncontact Electrostatic Sampling for Rapid Analysis with Mass Spectrometry: Application to Drugs and Explosives.

A hand-held Van de Graaf generator is used to apply a high voltage, negligible current electrostatic potential to a wire mesh positioned in close proximity to a particle-laden surface in order to collect those particles for analysis. The electrostatic field effects transfer particles to the mesh without a requirement for mechanical contact between mesh and surface. Analysis of chemicals present in the sampled particles is completed by thermal desorption electrospray ionization. The utility of the method for noncontact sampling is demonstrated using solid drug powder samples, and inorganic explosives dispersed either on solid surfaces or in sand/soil in order to simulate common interfering matrices that might be encountered in the forensic environment. A metal mesh sampling substrate is utilized instead of traditional polymer-based swabs in order to permit thermal desorption at higher temperatures. The method leaves no visible trace of sampling leaving details such as a fingerprint image unperturbed, as demonstrated using fluorescence photography. Direct sampling of trace particles from hard surfaces and skin documents flexibility in the choice of sampling substrates, desorption temperatures, and sampling times. The potential of the device for use in forensic analyses is detailed.

Rapid identification of organophosphorus pesticides on contaminated skin and confirmation of adequate decontamination by ambient mass spectrometry in emergency settings.

Dermal exposure to pesticides may cause severe intoxication and even result in a fatal outcome. To expedite rescue in the emergency department, it is mandatory to develop a point-of-care analytical method for immediate identification of pesticides on the skin of exposed personnel, and to perform immediate dermal decontamination to prevent further harm and optimize the chance for full clinical recovery. Four of the most commonly used highly toxic pesticides that contaminate the skin were rapidly characterized by thermal desorption electrospray ionization mass spectrometry. The technique was also applied to confirm the completeness of pesticide decontamination from the skin. Pesticide sampling, desorption, ionization, and detection altogether took less than 30 s. In addition, different fabrics of protective garments worn by farmers were assessed with this efficient ambient mass spectrometric technique for their protective capabilities against dermal exposure to pesticides, and scanning electron microscopy was used to observe their different microstructures. The decontaminating efficacies of different cleansing agents for these skin contaminants were also evaluated by this technical platform. The repeatability of this method had a low relative standard deviation (<22%) for the detection of pesticides on the surface of swine skin. The detection limits of the pesticides in solution were found to be in the range of 3-20 ng/mL. Linearity was observed between the signal intensities and the concentrations of the four pesticides in solution within the range of 50 ng/mL to 50 μg/mL (R2 between 0.9921 and 0.9966). In addition, it was found that PVC fabric is optimal in preventing skin contamination by fenthion and detergent had the best efficiency for fenthion decontamination. Since the whole analytical process is extremely fast, this technique allows early point-of-care identification of contaminating pesticides on the skin of exposed patients in the emergency room, as well as rapid assessment of the adequacy of decontamination.

Using ambient mass spectrometry to explore the origins of phthalate contamination in a mass spectrometry laboratory

Phthalates are known endocrine disruptors that can have adverse effects on human hormonal balance and development. Phthalates are semi-volatile chemical compounds, thus they can continuously leach from phthalate-containing objects and pollute the environments such as offices or laboratories, where workers in these spaces can inhale potentially harmful amounts of phthalates. Identifying and removing phthalate-contaminated objects from these indoor environments can effectively eliminate exposure to these environmental hormones. However, as of now, it is highly impractical to perform a large-scale screening of phthalate-containing objects using conventional analytical techniques which are usually time- and labor-intensive. In this study, thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) combined with probe sampling was used to screen phthalates on all non-metallic objects in a mass spectrometry (MS) laboratory. Due to sample pre-treatment was unnecessary and there was no limitation of sampling on sample's shape, size, and material, screening of phthalates on an object using this ambient mass spectrometric approach was completed within 30s, which enable sufficient and high-throughput screening. Phthalate signals of di(2-ethylhexyl)phthalate (DEHP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) were qualitatively detected on the surfaces of the filters of air conditioners and air purifiers and laboratory door, indicating there was a possibility of phthalates contamination in the studying area. Other screened objects in the laboratory included the ceiling, wall, floor, chairs, benches, pipes, mechanical vacuum pump tubes, and some personal belongings, all of which contained phthalates. Among them, floor and mechanical vacuum pump tubes contained high concentration of DEHP, DINP and DIDP, suggesting they were the main sources of phthalate contamination in the MS laboratory.

Fast screening of trace multiresidue pesticides on fruit and vegetable surfaces using ambient ionization tandem mass spectrometry

An ambient ionization tandem mass spectrometric approach was developed to rapidly screen multiresidue pesticides on fruits and vegetables without sample preparation and chromatographic separation. The residual pesticides on fruits and vegetables were collected by sweeping a metallic probe across the sample surface for 2 cm. The analytes collected on the probe were desorbed and ionized in a thermal desorption electrospray ionization (TD-ESI) source, after which analyte ions were detected by a triple quadruple mass analyzer (QqQ) operated in multiple reaction monitoring (MRM) mode. With this TD-ESI/MS/MS approach, 308 pesticides were monitored, where a mixture containing 15 pesticide standards was successfully identified to demonstrate the capability of this approach to screen trace multiresidue pesticides. The approach had reasonable detection limits (<50 ppb) and reproducibility (RSD: 8.43%, n = 9) from the analysis of a benthiazole standard solution. Real samples including a tomato and bell pepper were analyzed using this TD-ESI/MS/MS approach. After TD-ESI/MS/MS analysis, the organic solvent extracts from the same samples were subjected to TD-ESI/MS/MS, gas chromatography mass spectrometry (GC-MS), and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for validation.

Direct and rapid characterization of illicit drugs in adulterated samples using thermal desorption electrospray ionization mass spectrometry

Foods and drinks have been adulterated with illicit drugs to facilitate criminal activities. Unfortunately, conventional analytical methods are incapable of rapidly characterizing these drugs in samples, as serious interferences from sample matrices must be removed through tedious and time-consuming pretreatment. Ambient ionization mass spectrometry (AMS) generally does not require sample pretreatment and is thus a suitable tool for directly and rapidly detecting illicit drugs in samples in different physical states. In this study, thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS), an AMS technique, was utilized to efficiently characterize illicit drugs spiked in samples including drinks, powders, and jelly candies. To perform sensitive analysis, the mass analyzer was operated in multiple reaction monitoring mode to monitor the molecular and fragment ions of the target analytes. The time required to complete a typical TD-ESI/MS analysis was less than 30 s. The limits of detection (LODs) for illicit drugs were found to be 100 ppb in drinks, 100–1000 ppb in instant powders, and 1.3–6.5 ng/mm2 on stamp surfaces. FM2 and nitrazepam laced in the inner layer of a jelly candy were detected by TD-ESI/MS, showcasing the advantage of the technique for direct and rapid analysis as opposed to conventional methods.

Rapid characterization of organic UV filters and their photoproducts in sunscreens by thermal desorption electrospray ionization mass spectrometry for the photostability study

UV filters and their photoproducts in sunscreen formulations are directly characterized by TD-ESI/MS. This is a highly viable strategy to study the photostability of highly complex and diverse sunscreen formulations in the market.

Point-of-care identification of organophosphates in gastric juice by ambient mass spectrometry in emergency settings

BackgroundFor emergency management, it is important to promptly identify the organophosphate ingested by self-poisoning patients since different organophosphates cause intoxication through different mechanisms and require different therapeutic strategies. This study aimed at the development of a point-of-care ambient mass spectrometric approach for rapid identification of organophosphate(s) in gastric juice for emergency management. MethodsSix organophosphate insecticides that are commonly ingested by self-poisoning patients in Taiwan were examined. The sample solutions were prepared and diluted with human gastric juice. A direct metallic probe was dipped and removed immediately from the sample solution. The probe was then inserted into the thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) to detect the analyte on the probe. ResultsSince no pretreatment of the specimen was required, the sampling processes followed by thermal desorption-electrospray ionization and mass spectrometric analysis of the organophosphate in the gastric juice were completed within 30 s. The detection limit of the organophosphates is at the 10–100 parts per billion level. Good linearity was observed between the corresponding changes in mass spectrometric signal intensities and the changes of organophosphate concentrations within the range of 5–1000 parts per billion. The high efficiency of this ambient mass spectrometric platform was further confirmed when a real sample of the drained gastric lavage fluid of a patient who suffered from ingestion of chlorpyrifos was collected in the emergency room and tested with this cutting-edge technique. ConclusionsThe results suggested that TD-ESI/MS is promising in promptly providing toxicological information to assist succeeding medical management in an emergency room.

Solid phase microextraction combined with thermal-desorption electrospray ionization mass spectrometry for high-throughput pharmacokinetics assays

Labor- and time-intensive sample preparation and liquid chromatography mass spectrometry (LC-MS) analysis are required for traditional pharmacokinetics (PK) studies. In order to simplify and accelerate the analytical process of the PK study, solid phase microextraction (SPME) combined with thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) was developed for rapid characterization of trace drug in biological fluids. Methylphenidate in plasma was extracted and concentrated by direct immersion SPME using fused-silica fibers coated with polydimethylsiloxane. The analytes on the SPME fiber were then characterized by TD-ESI/MS. Matrix-matched calibration with multiple reaction monitoring analysis was conducted to quantify methylphenidate. A linear calibration curve was constructed over a concentration range of 0.2–25 ng mL−1 (r = 0.997). The quantitative results obtained by SPME-TD-ESI/MS were validated by LC-MS/MS. The average relative error for both methods was found to be −5.3%. As a viable alternative to LC-MS, SPME-TD-ESI/MS enables simple, rapid, and high-throughput analysis of drugs in plasma. The developed approach is particularly beneficial to PK studies for a very small sample volume (10 μL) is needed, the extraction time is as short as 3 min, and the detection time is less than 30 s.

Rapid screening of basic colorants in processed vegetables through mass spectrometry using an interchangeable thermal desorption electrospray ionization source

Thermal desorption electrospray ionization/mass spectrometry (TD–ESI–MS) employing a quickly interchangeable ionization source is a relatively new ambient ionization mass spectrometric technique that has had, to date, only a limited number of applications related to food safety control. With reallocation of resources, this direct-analysis technique has had wider use in food analysis when operated in dual-working mode (pretreatment-free qualitative screening and conventional quantitative confirmation) after switching to an ambient ionization source from a traditional atmospheric pressure ionization source. Herein, we describe the benefits and challenges associated with the use of a TD–ESI source to detect adulterants in processed vegetables (PVs), as a proof-of-concept for the detection of basic colorants. While TD–ESI can offer direct qualitative screening analyses for PVs with detection capabilities lower than those provided with liquid chromatography/UV detection within 30 s, the use of TD–ESI for semi-quantification is applicable only for homogeneous food matrices.

Rapid detection of illegal colorants on traditional Chinese pastries through mass spectrometry with an interchangeable thermal desorption electrospray ionization source

Ambient mass spectrometry using an interchangeable thermal desorption/electrospray ionization source (TD–ESI) is a relatively new technique that has had only a limited number of applications to date. Nevertheless, this direct-analysis technique has potential for wider use in analytical chemistry (e.g., in the rapid direct detection of contaminants, residues, and adulterants on and in food) when operated in dual-working mode (pretreatment-free qualitative screening and conventional quantitative confirmation) after switching to a TD–ESI source from a conventional ESI source. Herein, we describe the benefits and challenges associated with the use of a TD–ESI source to detect adulterants on traditional Chinese pastries (TCPs), as a proof-of-concept for the detection of illegal colorants. While TD–ESI can offer direct (i.e., without any sample preparation) qualitative screening analyses for TCPs with adequate sensitivity within 30 s, the use of TD–ESI for semi-quantification is applicable only for homogeneous matrices (e.g., tang yuan).

Rapid Identification of Psychoactive Drugs in Drained Gastric Lavage Fluid and Whole Blood Specimens of Drug Overdose Patients Using Ambient Mass Spectrometry.

Psychoactive drug overdoses are life-threatening and require prompt and proper treatment in the emergency room to minimize morbidity and mortality. Prompt identification of the ingested psychoactive drugs is challenging, since witness recall is unreliable and patients' symptoms do not necessarily explain their loss of consciousness. Gas and liquid chromatography mass spectrometric analyses have been the traditionally employed methods to detect and identify abused substances; however, these techniques are time-consuming and labor-intensive. In this study, thermal desorption electrospray ionization mass spectrometry, an ambient mass spectrometric technique, was applied to rapidly characterize flunitrazepam, lysergic acid diethylamide, and 3,4-methylenedioxy-methamphetamine in drained gastric lavage fluid, and ketamine, cocaine, amphetamine and norketamine in whole blood samples. No pretreatment of the gastric lavage fluid specimens was required and the entire analytical process took less than 30 s per specimen. Liquid-liquid extraction, followed by centrifugation, was performed on the whole blood samples. The corresponding compounds were identified through matching the obtained mass spectrometric data with those provided by commercial databases. The limits-of-detection of the tested drugs in both drained gastric lavage fluid and whole blood samples are at sub ppm levels. This is sensitive enough for emergency medical application, since the quantities of medications ingested by overdosed abusers are much higher than the amounts that were tested.

Using thermal desorption electrospray ionization mass spectrometry to rapidly determine antimicrobial preservatives in cosmetics.

Characterization and quantification of permitted preservatives are important inspections to prevent the overuse of preservatives in authentic formulations. However, the complexity of sample matrices makes preservative determination in cosmetics a tedious process. A rapid analytical strategy to identify preservatives would insure large numbers of products are in compliance with government regulations. Thermal desorption electrospray ionization mass spectrometry (TD-ESI-MS) was used to directly detect preservative compounds in authentic formulations without sample pretreatment. The technique employs a metal probe, which was configured for sampling cosmetics in their original states and was inserted in a closed preheated oven to thermally desorb analytes. The desorbed analytes were then carried by a nitrogen gas stream into an ESI plume, where the formed ions were subsequently detected by the mass analyzer. The TD-ESI mass and tandem mass spectra of different classes of preservative standards were rapidly obtained, and the limits of detection were far below the legal limit of their respective concentrations. The preservatives were also directly detected in different types of authentic formulations in the absence of sample preparation, and within a few seconds per sample. Calibration curves for preservatives in four common formulations yielded good linearity in the regulation-allowed range. Due to its sensitivity, short analysis time, repeatability, and quantitative ability, TD-ESI-MS may serve as a suitable tool for large-scale screening of cosmetic preservatives to assure product safety. Copyright © 2016 John Wiley & Sons, Ltd.

Rapid point-of-care identification of oral medications in gastric lavage content by ambient mass spectrometry in the emergency room.

Acute poisoning should be handled with high efficiency in order to minimize morbidity and mortality in the emergency room. Unfortunately, history-taking and physical examination are not always reliable. Mis-swallowing of oral medications is common in the pediatric group. This study aimed at developing a rapid point-of-care ambient mass spectrometric method for the early identification of ingested oral medications in gastric lavage content. Four different types of oral medications that are most commonly mis-swallowed by children were diluted to different concentrations. Each of these chemical solutions was mixed with human gastric lavage content. A direct metallic sampling probe was dipped into the solution. It was then inserted promptly into the thermal desorption electrospray ionization source to carry out ionization and subsequent mass spectrometric analysis of the medications. The corresponding compounds were identified through matching of the obtained mass spectrometric data with those provided by well-established databases. Since no pretreatment of the specimen was required, the sampling step, and the subsequent thermal desorption electrospray ionization and mass spectrometric detection of the medications were completed within 30s. Mass spectra were obtained for four different kinds of oral medication. The limit-of-detection of the four tested oral medications in gastric lavage content is at sub-ppm level, which is sensitive enough for emergency medicine applications since the quantities of medications ingested by pediatric patients are usually much higher. Thermal desorption electrospray ionization mass spectrometry, with informational support provided by an online mass spectral database, allows for early point-of-care identification of mis-swallowed oral medications in the evacuated gastric lavage contents obtained from gastric lavage of patients in the emergency room, and it is promising in providing important toxicological information to ensure the appropriateness of the subsequent medical management. Copyright © 2016 John Wiley & Sons, Ltd.

Rapid screening of residual pesticides on fruits and vegetables using thermal desorption electrospray ionization mass spectrometry.

Conventional mass spectrometry is encumbered by laborious and inconvenient sample pretreatment. Ambient thermal desorption electrospray ionization mass spectrometry (TD-ESI-MS) is most noted for its rapid, simple, and sensitive detection capabilities. In this study, TD-ESI-MS was used to rapidly characterize residual pesticides on the surfaces of fruits and vegetables. A direct sampling probe was used to obtain analytes from sample surfaces. MS and MS/MS analyses were performed on fruits and vegetables via TD-ESI-MS. External calibration curves and reproducibility tests were performed using liquid pesticide standards. Pesticide decay and distribution on samples was studied, as well as the removal of residual pesticides via soaking in water or detergent baths. Since sample pretreatment was unnecessary, an analysis was completed in approximately 15 s or less, with no visible sample damage. Mass spectra were obtained for 22 pesticides. Linear calibrations (R(2) from 0.9414-0.999) had limits of detection as low as 0.5 µg·L(-1), with satisfactory reproducibilities for liquids and solids. Pesticides on sample surfaces decayed over 2 weeks under ambient conditions. Residual pesticides localized at the fruit peel. Detergent baths removed more pesticide than water baths. TD-ESI-MS was used to rapidly screen residual pesticides in liquids and solids. Pesticides were found on fruits and vegetables, where the decay, distribution, and removal of pesticides on samples were also explored. Due to short analysis times, the technique allows for high-throughput analyses for applications in food and environmental safety.

Rapid Characterization of Chemical Compounds in Liquid and Solid States Using Thermal Desorption Electrospray Ionization Mass Spectrometry

Rapid characterization of thermally stable chemical compounds in solid or liquid states is achieved through thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS). A feature of this technique is that sampling, desorption, ionization, and mass spectrometric detection are four separate events with respect to time and location. A metal probe was used to sample analytes in their solid or liquid states. The probe was then inserted in a preheated oven to thermally desorb the analytes on the probe. The desorbed analytes were carried by a nitrogen gas stream into an ESI plume, where analyte ions were formed via interactions with charged solvent species generated in the ESI plume. The analyte ions were subsequently detected by a mass analyzer attached to the TD-ESI source. Quantification of acetaminophen in aqueous solutions using TD-ESI/MS was also performed in which a linear response for acetaminophen was obtained between 25 and 500 ppb (R(2) = 0.9978). The standard deviation for a reproducibility test for ten liquid samples was 9.6%. Since sample preparation for TD-ESI/MS is unnecessary, a typical analysis can be completed in less than 10 s. Analytes such as the active ingredients in over-the-counter drugs were rapidly characterized regardless of the different physical properties of said drugs, which included liquid eye drops, viscous cold syrup solution, ointment cream, and a drug tablet. This approach was also used to detect trace chemical compounds in illicit drugs and explosives, in which samples were obtained from the surfaces of a cell phone, piece of luggage made from hard plastic, business card, and wooden desk.