Carbon Fiber Ionizer Research Articles

Combating Pathogens Using Carbon-Fiber Ionizers (CFIs) for Air Purification: A Narrative Review

Airborne pathogens, though a minor fraction of airborne particles, can cause infections, intoxications, or allergic reactions through respiration, dermal contact, or ingestion. The SARS-CoV-2 pandemic has underscored the significance of mitigating airborne microbial threats. Traditional air ionization methods, such as dielectric barrier discharge and metal tip corona discharge, produce ozone, a reactive and potentially harmful byproduct. However, carbon-fiber ionizers (CFIs) generate high concentrations of ions with minimal ozone production, making them a safer alternative. Operating at voltages below 5 kV, CFIs are more efficient than their metallic counterparts. This review focuses on the antimicrobial efficacy of CFIs, which produce unipolar ions that can disrupt microbial membranes, leading to cell death. Compared to ultraviolet light sterilization, CFIs are cost-effective and suitable for small spaces. The literature review highlights the need for comprehensive studies to evaluate the real-world application and effectiveness of CFIs. Many existing studies are limited by small-scale testing and insufficient data reporting, complicating comparative analyses. Our work aims to provide a detailed perspective on CFIs, examining their impact on various microorganisms, ion efficacy, ionization outcomes, and ozone generation levels. By addressing these aspects, the review seeks to offer an updated understanding of CFIs’ antimicrobial capabilities and to identify limitations in current research, paving the way for more informed and effective air purification strategies.

Using Magnetic Micelles Combined with Carbon Fiber Ionization Mass Spectrometry for the Screening of Trace Triazine Herbicides from Aqueous Samples.

Triazine herbicides are commonly used in agriculture to eliminate weeds. However, they can persist in the environment. In this study, we explored a new method for detecting triazine herbicides in aqueous samples. We selected two triazine herbicides, namely, prometryn and ametryn, as model herbicides. To generate magnetic probes, we mixed aqueous Gd3+ with aqueous sodium dodecyl sulfate (SDS), which created magnetic probes made of Gd3+-SDS micelles. These probes showed a trapping capacity for the model herbicides. Results indicated that the trapping capacities of our magnetic probes for ametryn and prometryn were approximately 466 and 468 nmol mg-1, respectively. The dissociation constants of our probes toward ametryn and prometryn were 2.92 × 10-5 and 1.27 × 10-5, respectively. This is the first report that the developed magnetic probes can be used to trap triazine herbicides. For detection, we used carbon fiber ionization mass spectrometry (CFI-MS), which can be used to directly detect semi-volatiles from the samples in the condensed phase. Because of the semi-volatility of triazine herbicides, the herbicides trapped by the magnetic probes can be directly analyzed by CFI-MS without any elution steps. In addition, we also demonstrated the feasibility of using our approach for detecting triazine herbicides in lake water and drinking water.

Quantitative Analysis of Three Synthetic Cannabinoids MDMB-4en-PINACA, ADB-BUTINACA, and ADB-4en-PINACA by Thermal-Assisted Carbon Fiber Ionization Mass Spectrometry.

Recently, synthetic cannabinoids (SCs) have emerged as new psychoactive substances (NPS) and have been frequently added to e-liquids, leading to their abuse. In order to detect SCs in e-liquids quickly and accurately, a thermal-assisted carbon fiber ionization mass spectrometry technique has been developed. The introduction of a heat source helps to reduce the matrix effects. The results indicate that the ratio of the slope of the matrix curve (e-liquids matrix) and the standard curve (methanol solution) for SCs analysis is close to 1, indicating a minimized matrix effect of this method. Furthermore, this method exhibits good quantitative ability when applied to real samples. It does not require sample pretreatment and is sensitive enough to directly quantify SCs in e-liquids. Our method is characterized by the ability to achieve rapid and direct quantitative analysis with minimized matrix effects. It provides a rapid and simple method for analyzing SCs in e-liquids.

Rapid and Direct Assessment of Asphalt Volatile Organic Compound Emission Based on Carbon Fiber Ionization Mass Spectrometry.

Due to the complicacy of asphalt fumes, the analytical methods for investigating volatile organic compounds (VOCs) are very limited. In this study, a direct and real-time analysis method based on carbon fiber ionization mass spectrometry (CFI-MS), an ambient mass spectrometric technique, was established and successfully applied in the analysis of asphalt VOCs. The asphalt VOCs can be directly detected in the open atmosphere without the collection step of asphalt fumes, and the mass spectra of one asphalt sample can be obtained in a few seconds in both positive and negative ion modes. By investigating the mass spectral changes of asphalt fumes at different heating temperatures ranging from 50 to 200 °C, the temperature factor of asphalt fume emission was demonstrated in this work. The research results demonstrate that the complexity of asphalt fumes is positively related to the applied temperature. Moreover, the VOCs of saturates, aromatics, resins, and asphaltenes fractions were also analyzed by the direct analysis method. The result shows that aromatics contribute most to the emission of VOCs. In addition, the obtained mass spectra combined with the principal component analysis method show the great potential to quickly screen VOC inhibitors of asphalt materials.

A Study on the Particle Removal Efficiency and Durability According to the Material of the Ionizer of the Fiber Brush Type Electric Precipitator

In this study, we investigated the particulate matter (PM) removal efficiency and durability of the two-stage electrostatic precipitator (ESP) different materials of brush-typed ionizers (non-metal: carbon fiber/metal: stainless steel (SUS) fiber). The PM removal efficiency was reduced when the average diameter and number of fibers of the brush-typed ionizer increased due to thin and multi-edge in a large number of fibers, which decreased the average electric field, resulting in lower PM removal efficiencies. In contrast with the carbon fiber ionizer, when the SUS fiber ionizer was used, the PM removal efficiency was maintained for a long time, due to its lower electrical resistivity (∼6.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−7</sup> Ω * m) of the SUS fiber compared with the carbon fiber (∼5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> Ω * m), which prevents the positive ions to be stacked on the fiber. Therefore, the present research showed the potential use to apply SUS fiber ionizers as two-stage ESPs for a future air pollution control technology with high PM removal efficiency and durability without ozone emission and additional maintenance.

An online derivatization strategy targeting carbon–carbon double bonds by laser-ablation carbon fiber ionization mass spectrometry imaging: Unraveling the spatial characteristic in mountain-cultivated ginseng and garden-cultivated ginseng with different ages

Serving as a world-renowned tonic, ginseng contains various types of bioactive metabolites. The comprehensive profiling of these metabolites may help explore the nutritional value of ginseng. Due to high variety in chemical structures, simultaneous monitoring of these metabolites remains a challenge. Herein, a high-throughput and high-selectivity online derivatization mass spectrometry imaging strategy targeting CC was developed. As a widely existed chemical group, CC acts like a bridge connecting different kinds of metabolites. [d0]/[d10]-Bis(pyridine) iodine tetrafluoroboride reagent was chosen for the derivatization of CC, the detection sensitivity of which increased about 3 magnitudes after derivatization. Assisted by laser ablation carbon fiber ionization mass spectrometry, the spatial distribution of bioactive metabolites in mountain-cultivated and garden-cultivated ginseng were visualized. The correlation heatmap results revealed that metabolites in mountain-cultivated ginseng hold higher correlation than those in garden-cultivated ginseng. The proposed method showed potential in providing comprehensive information on the nutrient content of foods.

Improvement of an In-Duct Two-Stage Electrostatic Precipitator via Diffusion Charging.

An in-duct two-stage electrostatic precipitator (ESP) improved by ion diffusion effect was studied. We increased the collection efficiency of a two-stage electrostatic precipitator without additional energy input by adjusting the space arrangement of the charger and the collector, which increased the particle diffusion charging time. The collection efficiency and the particle charge were systematically investigated according to the occurrence of diffusion charging and electric field charging in the charger as generated by the negative ions. The collection efficiency of the separated two-stage ESP was 39% higher, on average, than the theoretical efficiency at the same power consumption. Through simulation, it was verified that the ions generated in the carbon fiber ionizer penetrated the charger. We proposed a modified charging mechanism assuming that the penetrated ions cause additional particle charge. The optimal separation distance between the charger and the collector, which showed the maximum collection efficiency, was derived through the modified charging model. Therefore, the in-duct two-stage ESP developed in this study is a promising energy-efficient and cost-saving design for indoor air management.

Carbon fiber paper spray ionization mass spectrometry

Carbon fiber paper (CFP) is commonly used as a proton exchange membrane in fuel cells due to its prominent areal electrosorption capacity, exceptional conductivity and excellent chemical stability. In this paper, we first explored the feasibility of carbon fiber paper as a specific paper substrate in paper spray ionization mass spectrometry (PSI-MS). The results demonstrated that CFPSI-MS combines the merits of PSI and carbon fiber ionization (CFI) and exhibits better performance of various compound analyses than either of these techniques alone. The application of CFP can highly enhance the signal stability and detection sensitivity of a diverse array of analytes, especially in negative ionization mode. The ion intensity of target analytes such as saccharides and flavonoids was improved 2-90-fold. Many nonpolar/low-polarity analytes, such as polycyclic aromatic hydrocarbons, which are difficult to ionize by traditional PSI-MS, were successfully detected by CFPSI-MS with a 2.5 kV high voltage. Moreover, CFPSI-MS presents high sensitivity in semiquantitative analysis, and the limits of detection (LODs) of cyclic adenosine monophosphate (CAMP), naringin and tivantinib in whole blood were improved 2-100-fold compared to those in traditional PSI-MS. In real sample analysis, CFPSI-MS also exhibits excellent capability in human breath analysis and blood metabolomic profiling.

Using Solid-Phase Microextraction Coupled with Reactive Carbon Fiber Ionization-Mass Spectrometry for the Detection of Aflatoxin B1 from Complex Samples

Aflatoxin B1 (AFB1) is a common mycotoxin present in agricultural and food products. Therefore, rapid screening methods must be developed for AFB1 detection with high sensitivity and good selectivity. In this study, we developed an analytical method based on the combination of solid-phase microextraction (SPME) with carbon fiber ionization (CFI)-mass spectrometry (MS) to detect the presence of trace AFB1 from complex samples. A pencil lead (type 2B, length: ~2.5 cm) with a sharp end (diameter: ~150 μm) was used as the SPME fiber and the ionization emitter in CFI-MS analysis. Owing to the graphite structure of the pencil lead, AFB1 can be trapped on the pencil lead through π–π interactions. After adsorbing AFB1, the pencil lead was directly introduced in a pipette tip (length: ~0.7 cm; tip inner diameter: ~0.6 mm), placed close (~1 mm) to the inlet of the mass spectrometer, and applied with a high voltage (−4.5 kV) for in situ AFB1 elution and CFI-MS analysis. A direct electric contact on the SPME-CFI setup was not required. Followed by the introduction of an elution solvent (10 μL) (acetonitrile/ethanol/deionized water, 2:2:1 (v/v/v)) to the pipette tip, electrospray ionization was generated from the elution solvent containing AFB1 for CFI-MS analysis. A reactive SPME-CFI-MS strategy was employed to further identify AFB1 and improve elution capacity using our approach. Butylamine was added to the elution solvent, which was then introduced to the pipette tip inserted with the SPME fiber. Butylamine-derivatized AFB1 was readily generated and appeared in the resultant SPME-CFI mass spectrum. The lowest detectable concentration against AFB1 using our approach was ~1.25 nM. Our method can distinguish AFB1 from AFG1 in a mixture and can be used for the detection of trace AFB1 in complex peanut extract samples.

Development of Electrostatic-Precipitator-Type Air Conditioner for Reduction of Fine Particulate Matter in Subway

This study developed a highly efficient electrostatic precipitator (ESP) type air conditioner to reduce the particulate matter (PM) concentration in a subway station. A polyethylene terephthalate film coated carbon sheet nonmetallic electrode was used as a collection plate to reduce the weight instead of the metallic collection plate, and the carbon fiber ionizer was used to minimize the ozone generation. When the flow velocity in a duct was 1 m/s with −5.0 kV applied to the ionizer and −5.0 kV to the collection plates, the 0.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> removal efficiency increased up to 97.47%. Holes in the collection plates were used to attach connecting tubes to maintain a constant distance. The strength and shape of the electric field were analyzed using COMSOL. The electric field quickly dissipated in the hole areas, and the field strength converged to 0. The collection plates were extended to compensate for the reduced collection area due to the holes. As a result, when the flow rate in the duct was 1 m/s, −5.0 kV was applied to the ionizer, and the electric field strength was up to −1.5 kV/mm, the PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> removal efficiency was increased to 99.08%. This behavior resembled that of conventional collection plates. The ESP developed in this study corresponds to a higher MERV13 grade than the MERV10 grade filter currently installed in the air conditioner of the subway station and has almost no pressure drop, so it is expected to contribute to the improvement of air quality and energy efficiency of subway stations.

Online Quaternized Derivatization Mapping and Glycerides Profiling of Cancer Tissues by Laser Ablation Carbon Fiber Ionization Mass Spectrometry.

Mass spectrometry imaging has become a hot research field owing to its ability to reflect the distribution of multiple metabolites in tissue. However, not all kinds of metabolites have great ionization efficiency in mass spectrometry imaging. The mass signals of low polar metabolites like monoglycerides and diglycerides may be seriously suppressed. Many strategies have been proposed to fix the problem, such as on-tissue derivatization and online derivatization. Also, some challenges were encountered when implementing these approaches. Herein, a platform coupled online quaternized derivatization and laser ablation carbon fiber ionization mass spectrometry imaging has been developed. The mass signals of monoglycerides and diglycerides were drastically increased in the platform, and high-quality mass images of these metabolites could be acquired readily. In the platform, metabolites were first desorbed by a laser and then reacted online with a derivatization reagent transmitted by carbon fiber ionization, which also undertook the postionization of derivatization products. Pyridine acted as the main derivatization reagent to target metabolites with hydroxyl groups. Remarkably, the derivatization reaction proceeded rapidly without any catalyst owing to the high energy provided by the laser. The mass images of eight monoglycerides and 21 diglycerides were achieved after applying the platform into human ovarian cancer tissues. Notably, a higher mass intensity of these glycerides was captured in cancerous tissues than in para-cancerous tissues, which might infer aberrations in glyceride metabolisms of cancerous tissues.

Rapid Characterization of Drugs in Biological Fluid and Seized Material Using Thermal-Assisted Carbon Fiber Ionization Mass Spectrometry.

Developing a rapid, simple, and sensitive method to analyze drugs is critical to forensic research study because of the widespread occurrence of the matrix effect. Herein, we develop a method using thermal-assisted carbon fiber ionization mass spectrometry that can be used to directly analyze drugs in biological fluid. The key feature of this technique is that the biological samples such as urine and blood can be achieved online as precipitated protein on the carbon fiber tip and thermally desorbed by the metal ceramics heater, which can reduce the matrix effects and improve the sensitivity. Analytes including raw urine, blood, oral fluid, drink, tobacco tar, drug tablets, and paper cards can be rapidly identified and analyzed within a few minutes regardless of their physical variations. Due to its simplicity and noninvasive analysis, this method can be used for drugged driving analysis and to achieve point-of-care drug testing in clinical and forensic chemistry.

Ultrasonic extraction and nebulization in real-time coupled with carbon fiber ionization mass spectrometry for rapid screening of the synthetic drugs adulterated into herbal products

Ultrasonic extraction and nebulization in real-time/carbon fiber ionization mass spectrometry (UEN/CFI-MS) was developed to screen the synthetic drugs adulterated into herbal products such as antidiabetic drug, antihypertensive drug, and hypolipidemic drug. Recently, ambient ionization MS techniques have achieved great advance for rapid analysis of sample surface. However, direct analysis of the analytes inside samples remains a challenge due to a lack of effective online sample extraction procedures. Owing to disappointing desorption efficiency, analytes inside the sample suffer from low detecting sensitivity when applying ambient ionization MS techniques. In this study, online ultrasonic extraction combined with carbon fiber ionization was used for real-time extraction, nebulization and detection of the analytes inside samples. The ultrasonic atomizer could produce a high-frequency vibration to realize online extraction and nebulization of sample. Then, the produced sample droplets could be immediately ionized by the carbon fiber ionization mass spectrometry. UEN/CFI-MS has shown great compatibility to solvents and compounds with a wide range of polarity and has few limitations for the shape of sample. UEN/CFI-MS was successfully applied for the rapid screening of synthetic drugs adulterated into herbal products. Among 37 batches of herbal products, 1 batch of Chinese patent medicine and 6 batches of dietary supplements were detected to be adulterated with the synthetic chemicals without labeling.

Reactive carbon fiber ionization-mass spectrometry for characterization of unsaturated hydrocarbons from plant aroma.

Carbon fiber ionization (CFI)-mass spectrometry (MS) is an ambient technique that can be used to detect samples in gas, liquid, and solid forms simply by using a piece of carbon fiber as the ionization emitter. Reactive MS can be performed to selectively detect target analytes by conducting fast reactions during ionization. Most ambient ionization MS techniques used to monitor chemical reactions are limited to liquid-phase reactions. Herein, we develop reactive CFI-MS to be a suitable tool for monitoring of reaction products derived from volatile unsaturated hydrocarbons in the gas phase. Hydroamination is a fast reaction that can form a carbon-nitrogen bond through the addition of an amine to unsaturated hydrocarbons. In this study, reactive CFI-MS was used to selectively characterize aroma molecules, which are unsaturated hydrocarbons derived from plants, through hydroamination. A piece of carbon fiber was placed close (~ 1mm) to the inlet of the mass spectrometer and deposited with dried methylamine. The sample in either liquid or solid form was placed underneath the carbon fiber. The volatiles derived from the sample reacted with amine on the carbon fiber were simultaneously determined once the mass spectrometer was switched on. For proof of concept, ethylene glycol dimethacrylate, which has double bonds and is highly volatile, was initially selected as the model sample to demonstrate the feasibility of using reactive CFI-MS to detect its hydroamination derivative. Banana, garlic, and ginger, which possess aroma molecules with unsaturated hydrocarbons, were selected as real-world samples. Graphical abstract.

Effect of Bipolar Charging of SiH4 on the Growth Rate and Crystallinity of Silicon Films Grown in the Atmospheric Pressure Chemical Vapor Deposition Process

Increasing the growth rate of thin films and enhancing the film quality have been an issue in the semiconductor manufacturing process. To improve those properties, conventionally the deposition temperature in reactor was increased or a catalyst was added to decompose precursors at low temperature. Here, a new technology utilizing a bipolar carbon fiber ionizer (CFI) was used to achieve a high growth rate and quality of silicon films. The deposition behavior of atmospheric pressure chemical vapor deposition silicon films deposited with and without the bipolar CFI system was compared. The growth rate of silicon films deposited at 450 °C, 500 °C, 700 °C, 900 °C and 1100 °C with the bipolar CFI system was 3.4, 5.6, 3.2, 3.3 and 1.3 times higher than deposited silicon film without the bipolar CFI system. The bipolar CFI system could also improve the crystallinity of the silicon film deposited at 900 °C.

Direct analysis of volatile components from intact jujube by carbon fiber ionization mass spectrometry

In situ analysis of odor is an important approach to connect odor with chemical composition. However, it is difficult to conduct a rapid direct analysis of the odor sample because of low analyte concentration and sampling. To achieve the direct analysis, a carbon fiber ionization mass spectrometry (CFI-MS) method has been developed and applied to measure volatile components releasing from intact jujube. To build the CFI source, a 2.0-cm long carbon fiber bundle was integrated on the pin of a commercial corona discharge needle by mean of a 1.3-cm long stainless hollow tube. Odor sample driven by N2 gas can be directly introduced to the carbon fiber bundle to complete the ionization of analytes. Acetic acid, ethyl acetate, ethyl caproate, octyl acetate, and damascone present in jujube were selected to evaluate the performance of the CFI-MS method on quantitative analysis of the gaseous sample. Good lineary was obtained (R2 ≥ 0.9946) between 5.0 and 500.0 ng/L with limits of detection (LOD) ranging from 0.5 to 1.5 ng/L. Recoveries of five volatile compounds for the spiked jujube samples were between 94.36 and 106.74% with relative standard deviations (RSDs) less than 7.27% (n = 5). Jujube of different varieties can be distinguished by principal components analysis based on the analytical results of volatile compounds. The developed method demonstrated obvious advantages such as simplicity, high throughput, good sensitivity and wide range of applicability, which will be an alternative way for in situ analysis of the odor sample.

Ultrafine particle cleaning performance of an ion spray electrostatic air cleaner emitting zero ozone with diffusion charging by carbon fiber

A novel electrostatic precipitator (ESP)-type small air cleaner with an ion spray charger was developed and evaluated. Unlike conventional ESP air cleaners, the charger is located at the rear of the collection stage. Ions are emitted into ambient space by the fan of the air cleaner, and airborne particles are charged by nearby ions through a diffusion charging mechanism. A carbon fiber ionizer without a grounded metal plate was installed as the charger to minimize ozone emission. The novel air cleaner had a particle clean air delivery rate (CADR) for 0.3-μm particles of 0.863 m3/min at a fan flow rate of 2.0 m3/min and applied voltages of – 5 kV to the ionizer and collection plate. As the size of the particles increased from 0.25 to 1 μm, particle CADR increased from 0.6 to 1.6 m3/min. Near-zero ozone emission was generated in a closed chamber (30.4 m3), and the concentration decreased from an initial background level of 2.39 ppb–1.29 ppb after 12 h of continuous operation. Our study showed a close relationship between particle CADR and the number of charges per particle, and the number of charges per particle matched well with theoretical predictions based on diffusion charging theory. The particle CADR of ion spray ESPs was 3.63 times higher than that of a high-efficiency particulate air (HEPA) filter air cleaner of similar volume. In an actual environment (56.43 m3), the particle CADR was 0.798 m3/min, similar to the chamber test.

Detection of pesticide residues on intact tomatoes by carbon fiber ionization mass spectrometry.

Trace and toxic pesticide residues may still remain on crops after harvest. Thus, maximum residual levels (MRLs) of pesticides on crops have been regulated. To determine whether the remaining pesticide residue level is below MRL, time-consuming sample pretreatment is needed prior to analysis of crop samples by suitable analytical tools. By elimination of sample pretreatment steps, a high-throughput method can be developed to determine the presence of pesticide residues directly on intact crops. Carbon fiber ionization mass spectrometry (CFI-MS) is effective in determining analytes with different polarities in solid, liquid, and vapor phases in open air. Moreover, the vapor derived from solid or liquid samples possessing high vapor pressure can be readily detected by CFI-MS. The setup of CFI-MS is straightforward. A carbon fiber (diameter of ~ 10μm and length of ~ 1cm) is placed close (~ 1mm) to the inlet of the mass spectrometer applied with a high voltage (- 4.5kV). No direct electrical contact applied on the carbon fiber is required. When placing the sample with certain vapor pressure underneath the carbon fiber, analyte ions derived from the sample can be readily detected by the mass spectrometer. Given that most pesticides possess a certain vapor pressure (~ 1.33 × 10-5-~ 1.33 × 10-4Pa), we herein develop a qualitative and quantitative analysis method to determine pesticide residues on intact fruits such as tomato based on CFI-MS without requiring any sample pretreatment. Atrazine, ametryn, carbofuran, chlorpyrifos, isoprocarb, and methomyl were selected as model samples. Low limits of detection (at nM range) were achieved for the model pesticides using the current approach. Moreover, we demonstrated that the precision and accuracy of quantitative analysis of ~ 5% and ~ 2%, respectively, could be achieved using this approach. Graphical Abstract ᅟ.

Carbon fiber ionization mass spectrometry coupled with solid phase microextraction for analysis of Benzo[a]pyrene

Solid phase micro-extraction (SPME) is an effective technique that can be used to selectively enrich trace analytes of interest from complex samples. Owing to its high sensitivity and high selectivity, mass spectrometry (MS) has been widely used as the detection tool to confirm the analytes enriched on SPME fibers. Generally, thermal desorption or solvent desorption is used to desorb analytes from SPME fibers for MS analysis. A straightforward ionization method called carbon fiber ionization (CFI), which uses a single carbon fiber (diameter: ∼10 μm) as ionization emitter in MS, has been demonstrated lately. Analytes adsorbed on the carbon fiber, which is placed close (∼5 mm) to the inlet of a mass spectrometer, can be readily ionized through corona discharge and detected by the mass spectrometer. One unique feature regarding this approach over other existing ambient ionization methods is that no additional electric contact is applied directly on the carbon fiber. Nevertheless, on the basis of the electric field provided by the mass spectrometer, corona discharge can readily occur for ionizing analytes on the carbon fiber. Carbon fiber has high affinity toward polycyclic aromatic hydrocarbons due to its graphite-like surface structure. We herein explore a hyphenated-technique by combining carbon-fiber based SPME with CFI-MS for extraction of benzo[a]pyrene (BaP), a carcinogen, from aqueous samples. After BaP are adsorbed on a carbon fiber through SPME, the SPME carbon fiber can be readily placed in front of the mass spectrometer for MS analysis. The ions at m/z 252 derived from BaP adsorbed on the carbon fiber can be immediately acquired by the mass spectrometer without the requirement of applying heating or solvent. The limit of detection of BaP using the developed method was as low as ∼60 pM. It is also feasible to detect BaP from complex serum sample. The feasibility of using the approach for quantitative analysis of BaP was also demonstrated. The linear dynamic range toward BaP was 0.2–5 nM. The extraction efficiency using this approach for aqueous samples was ∼91%.

Rapid quantitative analysis with low matrix effects of capsaicin in various samples by thermal desorption carbon fiber ionization mass spectrometry

It is difficult to conduct rapid quantitative studies by direct analysis of mass spectrometry because of the matrix effects. In order to overcome the matrix effects in rapid quantitative analysis of complex sample and to find a rapid mass spectrometry method for capsaicin quantitation, the thermal desorption carbon fiber ionization mass spectrometry (TD-CFI-MS) was developed and optimized. TD-CFI-MS allows timesaving, less cost, less solvent consumption and no auxiliary gas. In this method the metal ceramics heater (MCH) was used for analyte desorption. The protonated water clusters in carbon fiber ion source provided proton for analytes through ion-molecular interactions. Desorption and ionization processes were separated in time and space so the analyte was less affected by the matrix during ionization, and the signal intensity of the analyte was enhanced. The matrix effects were investigated by the quantitative analysis of capsaicin in various samples using TD-CFI-MS, and the results were within 93.3–97.6% which indicated that almost no significant effects on the quantitation of capsaicin by this method. Finally, TD-CFI-MS was successfully applied for the quantitation of capsaicin in various real samples including foods and medicines indicating that this technique was a valuable strategy.