Timely expression of PGAM5 and its cleavage control mitochondrial homeostasis during neurite re-growth after traumatic brain injury.

BACKGROUND: Patients suffered from severe traumatic brain injury (TBI) have twice the risk of developing into neurodegenerative diseases later in their life. Thus, early intervention is needed not only to treat TBI but also to reduce neurodegenerative diseases in the future. Physiological functions of neurons highly depend on mitochondria. Thus, when mitochondrial integrity is compromised by injury, neurons would initiate a cascade of events to maintain homeostasis of mitochondria. However, what protein senses mitochondrial dysfunction and how mitochondrial homeostasis is maintained during regeneration remains unclear. RESULTS: We found that TBI-increased transcription of a mitochondrial protein, phosphoglycerate mutase 5 (PGAM5), during acute phase was via topological remodeling of a novel enhancer-promoter interaction. This up-regulated PGAM5 correlated with mitophagy, whereas presenilins-associated rhomboid-like protein (PARL)-dependent PGAM5 cleavage at a later stage of TBI enhanced mitochondrial transcription factor A (TFAM) expression and mitochondrial mass. To test whether PGAM5 cleavage and TFAM expression were sufficient for functional recovery, mitochondrial oxidative phosphorylation uncoupler carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) was used to uncouple electron transport chain and reduce mitochondrial function. As a result, FCCP triggered PGAM5 cleavage, TFAM expression and recovery of motor function deficits of CCI mice. CONCLUSIONS: Findings from this study implicate that PGAM5 may act as a mitochondrial sensor for brain injury to activate its own transcription at acute phase, serving to remove damaged mitochondria through mitophagy. Subsequently, PGAM5 is cleaved by PARL, and TFAM expression is increased for mitochondrial biogenesis at a later stage after TBI. Taken together, this study concludes that timely regulation of PGAM5 expression and its own cleavage are required for neurite re-growth and functional recovery.

Thermal desorption ambient ionization mass spectrometry for emergency toxicology.

In the emergency department, it is important to rapidly identify the toxic substances that have led to acute poisoning because different toxicants or toxins cause poisoning through different mechanisms, requiring disparate therapeutic strategies and precautions against contraindicating actions, and diverse directions of clinical course monitoring and prediction of prognosis. Ambient ionization mass spectrometry, a state-of-the-art technology, has been proved to be a fast, accurate, and user-friendly tool for rapidly identifying toxicants like residual pesticides on fruits and vegetables. In view of this, developing an analytical platform that explores the application of such a cutting-edge technology in a novel direction has been initiated a research program, namely, the rapid identification of toxic substances which might have caused acute poisoning in patients who visit the emergency department and requires an accurate diagnosis for correct clinical decision-making to bring about corresponding data-guided management. This review includes (i) a narrative account of the breakthrough in emergency toxicology brought about by the advent of ambient ionization mass spectrometry and (ii) a thorough discussion about the clinical implications and technical limitations of such a promising innovation for promoting toxicological tests from tier two-level to tier one level.

Thin layer chromatography/desorption flame-induced atmospheric pressure chemical ionization/mass spectrometry for the analysis of volatile and semi-volatile mixtures.

Flame-induced atmospheric pressure chemical ionization (FAPCI) has been used to directly characterize chemical compounds on a glass rod and drug tablet surfaces. In this study, FAPCI was further applied to interface thin layer chromatography (TLC) and mass spectrometry (MS) for mixture analysis. METHODS: A micro-sized oxyacetylene flame was generated using a small concentric tube system. Hot gas flow and primary reactive species from the micro-flame were directed toward a developed TLC gel plate to thermally desorb and ionize analytes on the gel surface. The resulting analyte ions subsequently entered the MS inlet for detection. RESULTS: A 1-1.5-mm-wide light-brown line was observed on the TLC plate after the desorption FAPCI/MS (DFAPCI/MS) analysis, revealing that the gel surface withstood a high temperature from the impact of the micro-flame. Volatile and semi-volatile chemical compounds, including amine and amide standards, drugs, and aromatherapy oils, were successfully desorbed, ionized, and detected using this TLC/DFAPCI/MS. The limit of detection of TLC-DFAPCI/MS was determined to be 5 ng/spot for dibenzylamine and ethenzamide. CONCLUSIONS: TLC/DFAPCI/MS is one of the simplest TLC-MS interfaces showing the advantages such as low costs and an easy set up. The technique is useful for characterizing thermally stable volatile and semi-volatile compounds in a mixture.

Avatar-like body imaging of dermal exposure to melamine in factory workers analyzed by ambient mass spectrometry.

Ambient mass spectrometry thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) can rapidly identify chemicals without pretreatment of biological samples. This study used a rapid semi-quantitative TD-ESI/MS screening technique for the probe skin sampling of melamine workers occupationally exposed to different ambient melamine concentrations to create avatar-like body images, which were then used to study temporal and dynamic changes in nephrotoxic melamine exposure. We enrolled four voluntary melamine workers from one factory, each from one of four worksites. Melamine exposure was highest in manufacturing and molding, followed by grinding and polishing, packing, and administration, the lowest. Skin samples were collected Friday (end-of-shift) and Monday (pre-shift). Early morning one-spot urine samples were also collected right after skin sampling. 2198 probe skin samples were collected and subjected to semi-quantitative TD-ESI/MS analyses of melamine chemical within 40 h. After normalization, converted body image scores revealed exposure to be highest in the manufacturing worker on Friday and lowest in the administrative worker on Monday. The absolute differences (Friday minus Monday) of normalized body image scores were all significantly positive in each individual worker and across all four workers (permutation test, all p-values < 0.002). The slope estimates of the linear regression line between body image scores and urinary melamine levels were 0.81 (p-value = 0.008). We concluded that this fast and non-invasive technique can potentially be used to study temporal and dynamic changes in exposure to occupational hazards. A future study of developing an automatic and reproducible TD-ESI/MS sampling platform is needed.

Gas chromatography combined with flame-induced atmospheric pressure chemical ionization mass spectrometry for the analysis of fatty acid methyl esters and saturated hydrocarbons.

A simple flame-induced atmospheric pressure chemical ionization (FAPCI) source was developed to couple a gas chromatograph (GC) with a mass spectrometer (MS). The interface consisted of a heated transfer line and a high voltage-free ambient FAPCI source. Nitrogen gas flowing through the heated transfer line was utilized to deliver the analytes eluted from a GC column to the ionization region. A micro oxyacetylene flame was positioned under the exit of heated transfer line, which generated primary charged species in the ionization region. Since the temperature at the ionization region was below 200 °C, the analytes were not thermally decomposed. Protonated analytes were formed by reacting the analytes with flame-induced charged species through ion-molecule reactions (IMRs). The simple GC-FAPCI/MS was used to characterize a series of fatty acid methyl esters (FAMEs) and long-chain normal alkanes, which showed protonated FAME and oxidized n-alkane ions on the mass spectra. The limits of detection (LODs) for C15:0 to C25:0 FAMEs were 1-2.5 pg. A calibration curve ranging from 2.5 to 500 pg, with a R2 value of 0.9821, was obtained.

Molecular Mapping of Sebaceous Squalene by Ambient Mass Spectrometry.

Squalene (SQ), a highly unsaturated sebaceous lipid, plays an important role in protecting human skin. To better understand the role of SQ in clinical medicine, an efficient analytical approach is needed to comprehensively study the distribution of SQ on different parts of the skin. In this study, sebaceous lipids were collected from different epidermal areas of a volunteer with sampling probes. Thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) was then used to characterize the lipid species on the probes, and each TD-ESI/MS analysis was completed within a few seconds without any sample pretreatment. The molecular mapping of epidermal squalene on whole-body skin was rendered by scaling the peak area of the extracted ion current (EIC) of SQ based on a temperature color gradient, where colors were assigned to the 1357 sampling locations on a 3D map of the volunteer. The image showed a higher SQ distribution on the face than any other area of the body, indicating the role of SQ in protecting facial skin. The results were in agreement with previous studies using SQ as a marker to explore sebaceous activity. The novelty and significance of this work are concluded as two points: (1) direct and rapid detection of all major classes of sebaceous lipids, including the unsaturated hydrocarbons (SQ) and nonpolar lipids (e.g., cholesterol). The results are unique compared to other conventional and ambient ionization mass spectrometry methods and (2) this is the first study to analyze SQ distribution on the whole-body skin by a high-throughput approach.

Mitochondrial Protein PGAM5 Emerges as a New Regulator in Neurological Diseases.

As mitochondrial dysfunction has increasingly been implicated in neurological diseases, much of the investigation focuses on the response of the mitochondria. It appears that mitochondria can respond to external stimuli speedy fast, in seconds. Understanding how mitochondria sense the signal and communicate with cytosolic pathways are keys to understand mitochondrial regulation in diseases or in response to trauma. It was not until recently that a novel mitochondrial protein, phosphoglycerate mutase family member 5 (PGAM5) has emerged to be a new regulator of mitochondrial homeostasis. Although controversial results reveal beneficial as well as detrimental roles of PGAM5 in cancers, these findings also suggest PGAM5 may have diverse regulation on cellular physiology. Roles of PGAM5 in neuronal tissues remain to be uncovered. This review discusses current knowledge of PGAM5 in neurological diseases and provides future perspectives.

Multiple solid phase microextraction combined with ambient mass spectrometry for rapid and sensitive detection of trace chemical compounds in aqueous solution.

Multiple solid phase microextraction (mSPME) combined with thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) was developed to rapidly characterize trace analytes in aqueous solution. A number of commercial available SPME fibers (from 2 to 10 fibers) were simultaneously used for extracting the analytes in solution. The fibers were then bundled together on a holder and subjected for the ambient mass spectrometric analysis. Good linearity for calibration (R2 = 0.9995) and low limit of quantification (<1 ppb) were achieved by using 10 SPME fibers coated with polyacrylate (PA) to extract bisphenol A. It was also found that the analyte signals increased with the number of SPME fibers for extraction. Uncontroversial, a shorter extraction time was required by using mSPME to reach the same level of analyte signal as that by using single SPME fiber for a longer extraction time. Trace bisphenol A (4-20 ppb) in the polycarbonate (PC) baby milk bottles was rapidly detected using mSPME-TD-ESI/MS and the analysis was completed within 1 min. The use of multiple SPME fibers coated with different materials enable the concentration of different type of analytes in the solution. Ibuprofen, bisphenol A (BPA), and 4-n-nonylphenol (4-n-NP) were simultaneously detected by using PA and polydimethylsiloxane (PDMS) coated fibers for extraction.

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 30 s, 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.

WNT3A Promotes Neuronal Regeneration upon Traumatic Brain Injury.

The treatment of traumatic brain injury (TBI) remains a challenge due to limited knowledge about the mechanisms underlying neuronal regeneration. This current study compared the expression of WNT genes during regeneration of injured cortical neurons. Recombinant WNT3A showed positive effect in promoting neuronal regeneration via in vitro, ex vivo, and in vivo TBI models. Intranasal administration of WNT3A protein to TBI mice increased the number of NeuN+ neurons without affecting GFAP+ glial cells, compared to control mice, as well as retained motor function based on functional behavior analysis. Our findings demonstrated that WNT3A, 8A, 9B, and 10A promote regeneration of injured cortical neurons. Among these WNTs, WNT3A showed the most promising regenerative potential in vivo, ex vivo, and in vitro.

An investigation of short physical performance battery score and its influencing factors among the elderly in communities of Shanghai / 中华老年医学杂志

Objective:To explore the main influencing factors for physical performance assessed by the short physical performance battery(SPPB)in the elderly in communities in Shanghai.Methods:A total of 500 elderly subjects from four communities in Shanghai who met the inclusion criteria with 165 males and 335 females aged 60-95 years(70.5±7.8)years were enrolled.A questionnaire was used to assess the general situation.International Physical Activity Questionnaire-Short Form(IPAQ-SF)was used to assess physical activity(PA). The appendicular skeletal muscle mass(ASM)was measured by bioelectrical impedance analysis, and the relative skeletal muscle mass index(RSMI). The lower extremity muscle strength(quadriceps strength, QS)was measured by a hand-held dynamometer.Lower body muscle quality(LB-MQ) was ascertained by taking the ratio of strength to muscle mass for lower extremity.SPPB score was used to assess physical activity, including full tandem test, 4-meter walking speed test and five timed chair stands test.Results:The age, RSMI, ASM and quadriceps strength were higher, and the body fat content was lower in males than in females(all P<0.001). There were no significant differences in BMI, SPPB scores, LBMQ, and PA between males and females( P>0.05). Pearson correlation analysis showed that SPPB score was negatively correlated with age( r=-0.615, P<0.001)and body fat content( r=-0.103, P=0.022), but SPPB score was positively correlated with quadriceps strength( r=0.351, P<0.001), RSMI( r=0.134, P=0.003), LBMQ( r=0.268, P<0.001)and amount of PA( r=0.204, P<0.001), however, SPPB score had no relationship with gender( r=0.068, P=0.132). Conclusions:Aging and frailty are the main factors for the decline of physical performance in the elderly.Participating physical activity, reducing body fat, maintaining muscle mass, and especially increasing muscle quality, may be the main interventions to prevent the further deterioration of physical performance in the elderly.

Role of calf circumference in the evaluation and diagnosis of sarcopenia in the elderly in Shanghai / 中华临床营养杂志

Objective:To investigate the relationship between calf circumference and appendicular skeletal muscle mass (ASM) index, handgrip strength and gait speed in the elderly in Shanghai, and to explore the optimal cut-off point of calf circumference as a simple proxy marker of skeletal muscle mass, strength and function.Methods:A total of 2 294 participants were recruited from physical examination centers in Huadong Hospital Affiliated to Fudan University and 4 communities (954 males and 1 340 females) with an average age of (71.6±8.7) years. Appendicular skeletal muscle mass (ASM), Upper (UMM) and lower (LMM) limbs skeletal muscle mass were measured by bioelectrical impedance analysis (BIA). The ASM index (ASM/height 2) were calculated.Gait speed was measured.Muscle strength was measured by handgrip strength using an electronic hand dynamometer.Height, weight, right calf circumference and waist circumference were measured. Results:The age, body mass index (BMI), waist circumference and gait speed were not statistically different (all P>0.05) between both genders. Height, weight, ASM, ASM/height 2, UMM, LMM, handgrip strength, calf circumference were significantly higher in men than in women (all P<0.05). The calf circumference of the elderly with age ≥ 80 was significantly lower than that of the 70-79 age group and 60-69 age group ( P<0.05). The calf circumference of older women (age≥80) was significantly lower than that of the elderly women in the 70-79 age group and 60-69 age group ( P<0.05). Calf circumference was correlated negatively with age( P<0.01) and positively with ASM/height 2, height, weight, BMI, handgrip strength, UMM and LMM( P<0.01). There was no correlation between calf circumference and gait speed ( P>0.05). In the receiver operating characteristic curve (ROC), the cut-off value of calf circumference for low muscle mass was 35.1 cm for male(specificity, 0.721; sensitivity, 0.803, ROC, 0.809) and 33.6 cm for female(specificity, 0.774; sensitivity, 0.778; ROC, 0.827). Conclusions:Calf circumference decreases with ageing in the elderly. The optimal cut-off value of calf circumference for low muscle mass is 35.1 cm for males and 33.6 cm for females. We should pay attention to the importance of calf circumference in evaluation and diagnosis of sarcopenia.

Current progress of mitochondrial transplantation that promotes neuronal regeneration.

BACKGROUND: Mitochondria are the major source of intracellular adenosine triphosphate (ATP) and play an essential role in a plethora of physiological functions, including the regulation of metabolism and the maintenance of cellular homeostasis. Mutations of mitochondrial DNA, proteins and impaired mitochondrial function have been implicated in the neurodegenerative diseases, stroke and injury of the central nervous system (CNS). The dynamic feature of mitochondrial fusion, fission, trafficking and turnover have also been documented in these diseases. PERSPECTIVES: A major bottleneck of traditional approach to correct mitochondria-related disorders is the difficulty of drugs or gene targeting agents to arrive at specific sub-compartments of mitochondria. Moreover, the diverse nature of mitochondrial mutations among patients makes it impossible to develop one drug for one disease. To this end, mitochondrial transplantation presents a new paradigm of therapeutic intervention that benefits neuronal survival and regeneration for neurodegenerative diseases, stroke, and CNS injury. Supplement of healthy mitochondria to damaged neurons has been reported to promote neuronal viability, activity and neurite re-growth. In this review, we provide an overview of the recent advance and development on mitochondrial therapy. CONCLUSION: Key parameters for the success of mitochondrial transplantation depend on the source and quality of isolated mitochondria, delivery protocol, and cellular uptake of supplemented mitochondria. To expedite clinical application of the mitochondrial transplantation, current isolation protocol needs optimization to obtain high percentage of functional mitochondria, isolated mitochondria may be packaged by biomaterials for successful delivery to brain allowing for efficient neuronal uptake.

High-throughput screening of phthalate-containing objects in the kindergartens by ambient mass spectrometry.

High-throughput screening of plastic products in children's living environment is necessary to identify phthalate-containing objects for the concern of public health and safety. A novel strategy of probe collecting technique combined with ambient mass spectrometry was developed to carry out the large-scale sample analysis. Analytes from the surface of approximately 500 objects each in two kindergartens in Taiwan were collected using the same number of the metallic probes. After being delivered to laboratory, the analytes on the probes were analyzed with thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS). As sample pretreatment was unnecessary, the analysis of phthalates on a probe was completed within 30 s enabling high-throughput screening of a large number of objects. All procedure including sampling and TD-ESI/MS analysis together with report writing for a kindergarten was completed in one day. A reasonable relative standard deviation (<15.6%) was obtained from replicate analyses of phthalate standards. Single-point calibration was used to perform semi-quantitative analysis, and results were validated by liquid chromatography/mass spectrometry (LC/MS). It was found that 20-40% of the objects in two kindergartens contained greater than low-level (>2 ng) of phthalates and 40-60% of the objects in the kindergartens contained more than one kind of phthalate.

Mitochondrial therapy promotes regeneration of injured hippocampal neurons.

Due to the inhibitory microenvironment and reduced intrinsic growth capacity of neurons, neuronal regeneration of central nervous system remains challenging. Neurons are highly energy demanding and require sufficient mitochondria to support cellular activities. In response to stimuli, mitochondria undergo fusion/fission cycles to adapt to environment. It is thus logical to hypothesize that the plasticity of mitochondrial dynamics is required for neuronal regeneration. In this study, we examined the role of mitochondrial dynamics during regeneration of rat hippocampal neurons. Quantitative analysis showed that injury induced mitochondrial fission. As mitochondrial dysfunction has been implicated in neurodegenerative diseases, we tested the possibility that the mitochondrial therapy may promote neuronal regeneration. Supplying freshly isolated mitochondria to the injured hippocampal neurons not only significantly increased neurite re-growth but also restored membrane potential of injured hippocampal neurons. Together, our findings support the importance of mitochondrial dynamics during regeneration of injured hippocampal neurons and highlight the therapeutic prospect of mitochondria to the injured central nervous system.

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.

Evaluating Prognosis of Multiple Myeloma by Different Infiltrative Patterns on Whole-body MRI / 中国医学影像学杂志

Purpose To investigate the prognostic value of whole-body magnetic resonance imaging (WB-MRI) for patients with multiple myeloma (MM).Materials and Methods Sixty-two newly diagnosed patients with MM confirmed by pathology during January 2010 and December 2016 were enrolled in this study.The patients were divided into five groups according to the infiltrative patterns on MRI:normal pattern,micro-nodular pattern,macronodular pattern,mixed pattern and diffuse pattern,and their overall survival were compared.Results Of all the patients,micro-nodular infiltrative pattern was found in 20 patients,macro-nodular pattern in 13 patients,mixed pattern in 7 patients and diffuse pattern in 17 patients,while 5 patients were normal.During the follow-up for a median of 39 months (ranged 30.9-47.1 months),overall survival with the mixed MM infiltrative pattern (median 17 months,95％ CI 12.6-21.3 months) was statistically shorter than those with other patterns (median 43 months,95％ CI 33.7-52.3 months;P＜0.05).Additionally,the clinical DurieSalmon (DS) and International Staging System (ISS) were applied to evaluate the stage of MM patients.DS system showed that 6 patients were at stage I,another 6 patients were at stage Ⅱ and the other 50 patients were at stage Ⅲ.While based on ISS system,15 patients were found at stage Ⅰ,22 patients were at stage Ⅱ and the rest 25 patients were at stage Ⅲ.Meanwhile,the correlation between the WB-MRI infiltrative pattems and DS system as well as ISS system had no significant correlation (P＞0.05).Conclusion Different infiltrative patterns in WB-MRI can predict the prognosis in patients with MM at the time of diagnosis.

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

RATIONALE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Simultaneous detection of polar and nonpolar compounds by ambient mass spectrometry with a dual electrospray and atmospheric pressure chemical ionization source.

A dual ionization source combining electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) was developed to simultaneously ionize both polar and nonpolar compounds. The source was constructed by inserting a fused silica capillary into a stainless steel column enclosed in a glass tube. A high dc voltage was applied to a methanol solution flowing in the fused silica capillary to generate an ESI plume at the capillary tip. A high ac voltage was applied to a ring electrode attached to the glass tube to generate plasma from the nitrogen gas flowing between the glass tube and the stainless steel column. The concentric arrangement of the ESI plume and the APCI plasma in the source ensured that analytes entering the ionization region interacted with both ESI and APCI primary ion species generated in the source. Because the high voltages required for ESI and APCI were independently applied and controlled, the dual ion source could be operated in ESI-only, APCI-only, or ESI+APCI modes. Analytes were introduced into the ESI and/or APCI plumes by irradiating sample surfaces with a continuous-wavelength laser or a pulsed laser beam. Analyte ions could also be produced by directing the dual ESI+APCI source toward sample surfaces for desorption and ionization. The ionization mechanisms involved in the dual ion source include Penning ionization, ion molecule reactions, and fused-droplet electrospray ionization. Standards of polycyclic aromatic hydrocarbons, angiotensin I, lidocaine, ferrocene, diesel, and rosemary oils were used for testing. Protonated analyte ions were detected in ESI-only mode, radical cations were detected in APCI-only mode, and both types of ions were detected in ESI+APCI mode.

Electrospray laser desorption ionization (ELDI) mass spectrometry for molecular imaging of small molecules on tissues.

The use of an ambient ionization mass spectrometry technique known as electrospray laser desorption ionization mass spectrometry (ELDI/MS) for molecular imaging is described in this section. The technique requires little or no sample pretreatment and the application of matrix on sample surfaces is unnecessary. In addition, the technique is highly suitable for the analysis of hard and thick tissues compared to other molecular imaging methods because it does not require production of thin tissue slices via microtomes, which greatly simplifies the overall sample preparation procedure and prevents the redistribution of analytes during matrix desorption. In this section, the ELDI/MS technique was applied to the profiling and imaging of chemical compounds on the surfaces of dry plant slices. Analyte distribution on plant slices was obtained by moving the sample relative to a pulsed laser and an ESI capillary for analyte desorption and post-ionization, respectively. Images of specific ions on sample surfaces with resolutions of 250 µm were typically created within 4.2 h for tissues with sizes of approximately 57 mm × 10 mm.