Online and Offline Prioritization of Chemicals of Interest in Suspect Screening and Non-targeted Screening with High-Resolution Mass Spectrometry.

Recent advances in high-resolution mass spectrometry (HRMS) have enabled the detection of thousands of chemicals from a single sample, while computational methods have improved the identification and quantification of these chemicals in the absence of reference standards typically required in targeted analysis. However, to determine the presence of chemicals of interest that may pose an overall impact on ecological and human health, prioritization strategies must be used to effectively and efficiently highlight chemicals for further investigation. Prioritization can be based on a chemical's physicochemical properties, structure, exposure, and toxicity, in addition to its regulatory status. This Perspective aims to provide a framework for the strategies used for chemical prioritization that can be implemented to facilitate high-quality research and communication of results. These strategies are categorized as either "online" or "offline" prioritization techniques. Online prioritization techniques trigger the isolation and fragmentation of ions from the low-energy mass spectra in real time, with user-defined parameters. Offline prioritization techniques, in contrast, highlight chemicals of interest after the data has been acquired; detected features can be filtered and ranked based on the relative abundance or the predicted structure, toxicity, and concentration imputed from the tandem mass spectrum (MS2). Here we provide an overview of these prioritization techniques and how they have been successfully implemented and reported in the literature to find chemicals of elevated risk to human and ecological environments. A complete list of software and tools is available from https://nontargetedanalysis.org/.

Combining trapped ion mobility spectrometry with liquid chromatography and tandem mass spectrometry for analysis of isomeric PDE-5 inhibitor analogs.

The detection and identification of phosphodiesterase type 5 enzyme (PDE-5) inhibitors in dietary supplements poses an analytical challenge due to the large number of analogs and isomers currently available and the continued introduction of novel analogs. The use of trapped ion mobility spectrometry (TIMS) in conjunction with liquid chromatography (LC) and electrospray ionization tandem mass spectrometry (MS/MS) was explored for the analysis of two groups of isomeric PDE-5 inhibitor analogs using a 5-minute method. Of the eight compounds studied, six were resolved by a combination of LC and TIMS; the two remaining isomers were distinguished by one or more unique product ions in the MS/MS spectrum. The results revealed that separation by LC corresponded to differences in substitution on the piperazine moiety of the PDE-5 inhibitors, while separation by TIMS corresponded to the position of a nitrogen atom in the fused ring region of the molecules. Samples prepared by spiking mixtures of varying amounts of the Group 2 isomers into a representative dietary supplement matrix were analyzed and concentrations determined from the mobility-adjusted extracted ion chromatograms exhibited relative standard deviations of 6.0 % or less for 17 of 20 measurements and recoveries between 80 % and 120 % for all measurements. Quantitative measurements from a short LC gradient were possible due to the reduced chemical background associated with the TIMS separation of co-eluting matrix compounds, which enabled acquisition of rapid and qualitatively relevant broadband collision induced dissociation spectra that didn't require precursor ion isolation; the reduced chemical background permits non-targeted detection of novel analogs and eliminates the need for a separate method for quantitative measurement.

Rapid Screening of Vaping Liquids by DART-MS.

BACKGROUND: E-cigarette, or vaping, product use-associated lung injury was reported in over 2800 cases from August 2019 to February 2020. Samples of vaping products were submitted for laboratory analysis in conjunction with investigation of the outbreak. A rapid screening method that was selective and sensitive for multiple analytes was required to aid in the investigation. OBJECTIVE: To develop a multi-analyte method capable of screening vaping liquid samples that consumed small amounts of sample, required minimal sample preparation and analysis time, employed automated data processing, and provided the necessary sensitivity and selectivity. METHODS: Vaping liquids were dissolved in acetonitrile and sampled with DIP-it® tips. The tips were analyzed by direct analysis in real-time mass spectrometry (DART-MS) and the resulting data processed with TraceFinder™ software. Laboratory-fortified samples consisting of various analytes and matrixes were evaluated prior to the analysis of submitted samples. RESULTS: The method was successful at detecting all target analytes in all matrixes evaluated, although the method detection limits varied by analyte/matrix combination: from 0.1% nicotine in poly(propylene glycol) average Mn 1000 (the lowest level evaluated) to 5.0% poly(ethylene glycol) average Mn 400 in cannabis concentrate. Results for the analysis of submitted samples by this method compared favorably to GC-MS and FTIR results. CONCLUSION: The DART-MS method met the objective of speed, sensitivity, and selectivity (although certain cannabinoid isomers could not be distinguished). The method may be easily adapted or expanded for additional analytes. HIGHLIGHTS: This is a simple DART-MS method for screening vaping liquids for substances of concern in less than 2 min per sample.

EVALI Vaping Liquids Part 2: Mass Spectrometric Identification of Diluents and Additives.

The vaping liquid additive vitamin E acetate (VEA) was strongly linked to the 2019 United States nationwide outbreak of pulmonary lung illness (EVALI) associated with e-cigarettes or vaping liquids. Our laboratory received over 1,000 vaping liquid products for identification of the vaping liquid additives, including hundreds of vaping products from EVALI patients. In this work, we present results obtained for the GC-MS identification of numerous vaping liquid additives in a large subset of ca. 300 Cannabis vaping liquids, including vitamin E acetate, medium chain triglycerides oil (MCT oil), polyethylene glycols, squalane, triethyl citrate, dipropylene glycol dibenzoate (DPG dibenzoate), pine rosin acids, pine rosin methyl esters, and sucrose acetate isobutyrate (SAIB). Confirmation of DPG dibenzoate and SAIB using LC-HRMS is also presented. GC-MS analysis for additives identified as the parent compounds was conducted after separation on a commercial 5% phenyl phase. GC-MS analysis for additives identified as the trimethylsilyl derivatives was conducted after separation on a commercial 35% silphenylene phase. LC-HRMS analysis was conducted using gradient elution with either C18 or phenyl-hexyl phases and determination of exact masses for the target compounds. In addition to providing rapid methods for the identification of vaping liquid additives, this work highlights the variety of Cannabis vaping liquid additives in current use.

Simultaneous Temperature Measurements and Aerosol Collection During Vaping for the Analysis of Δ9-Tetrahydrocannabinol and Vitamin E Acetate Mixtures in Ceramic Coil Style Cartridges.

Incidence of e-cigarette, or vaping, product use-associated lung injury (EVALI) has been linked to the vaping of tetrahydrocannabinol (THC) products to which vitamin E acetate (VEA) has been added. In this work we vaped THC/VEA mixtures at elevated power levels using a variety of ceramic coil vaping cartridges and a commercially available vaping device, while simultaneously measuring temperature and collecting the vaporized condensate. The collected vapor condensate was analyzed for evidence of VEA decomposition by GC/MS, GC/FT-IR/MS, and LC-APCI-HRMS/MS. Mean temperature maxima for all examined cartridges at the selected power exceeded 430°C, with a range of 375-569°C, well beyond that required for thermal decomposition of VEA. The percent recovery of VEA and Δ9-THC from the vaporized mixture in six cartridges ranged from 71.5 to 101% and from 56.4 to 88.0%, respectively. Analysis of the condensed vaporized material identified VEA decomposition products duroquinone (DQ), 1-pristene, and durohydroquinone monoacetate (DHQMA); a compound consistent with 4-acetoxy-2,3,5-trimethyl-6-methylene-2,4-cyclohexadienone (ATMMC) was also detected. The concentration of DQ produced from vaporization of the THC/VEA mixture in one cartridge was found to be 4.16 ± 0.07 µg per mg of vapor condensate.

Evaluation of "Toolkit" consisting of handheld and portable analytical devices for detecting active pharmaceutical ingredients in drug products collected during a simultaneous nation-wide mail blitz.

A "toolkit" consisting of a handheld Raman spectrometer equipped with a 1064 nm laser, a portable Fourier transform infrared (FT-IR) spectrometer and a portable direct analysis in real-time mass spectrometer (DART-MS) was employed in a laboratory setting to examine 82 representative products collected during a nationwide mail blitz for the presence of APIs. These results were compared to those obtained using laboratory-based methods; 8 of the products were not found to contain APIs and 74 of the products were found to contain a total of 88 APIs (65 of the 88 APIs were unique). The individual performance of each device and combined performance of the three-device toolkit were evaluated with regard to true positives, true negatives, false positives and false negatives. Using this toolkit, 81 (92.0 %) of the APIs were detected by at least one technique and 47 (64.8 %) of the APIs were detected by at least two techniques. Seven false negatives (8.0 %) were encountered and while the toolkit yielded 12 false positives, no false positives were detected by more than one technique. Overall, this study demonstrated that when the toolkit detects an API using two or more devices, the results are as reliable as those generated by a full-service laboratory.

Evaluation of four field portable devices for the rapid detection of mitragynine in suspected kratom products.

The development of a method for the rapid screening of food and drug products for constituents such as mitragynine, the most abundant alkaloid found in Mitragyna speciosa (kratom) plant leaves, has become increasingly important. The use of kratom is said to produce stimulant or narcotic effects and poses risks of addiction, abuse, and dependence, much like other opioids. Direct Analysis in Real Time with thermal desorption mass spectrometry (DART-TD-MS), hand-held mass spectrometry, portable ion mobility spectrometry (IMS), and portable Fourier-transform infrared spectroscopy (FT-IR) were each evaluated as field-deployable screening techniques for the detection of mitragynine in food and drug products. These devices offer the potential for rapid, early detection of mitragynine in suspect products entering the United States through international mail facilities and other ports of entry. Ninety-six kratom products, including capsules, bulk powder, and bulk plant material, were analyzed by either direct sampling of the solid material or by solvent extraction. True and false positive and negative results are reported, based on comparison to results from qualitative screening using gas chromatography with mass spectral detection (GC-MS), liquid chromatography with mass spectral detection (LC-MS), and/or quantitative screening using high-performance liquid chromatography with ultraviolet detection (HPLC-UV), with a discussion of the assessment of each technique for use in the field. Each device demonstrated attributes that would be favorable for use in screening of suspected mitragynine-containing products at places like ports of entry, and simultaneous deployment of two or more of these devices as part of a workflow would be the most effective for rapid screening of these products. This combination of rapid screening orthogonal techniques suited to a non-laboratory environment will allow onsite destruction of products found to contain mitragynine.

The bicipital groove as a landmark for humeral version reference during shoulder arthroplasty: a computed tomography study of normal humeral rotation.

BACKGROUND: Accurate reproduction of humeral version is important in shoulder arthroplasty. Traditional referencing relative to the transepicondylar axis (TEA) is prone to error as it is absent on preoperative imaging and inaccurately reproduced intraoperatively. The bicipital groove is present on preoperative imaging and in the operative field and thus may be a useful landmark for accurate reproduction of humeral version. MATERIALS AND METHODS: Two trained observers analyzed 101 full-humerus computed tomography scans of patients undergoing a myeloma screening protocol. Measurements of humeral retroversion relative to the TEA (angle A), humeral articular axis retroversion relative to the bicipital groove (angle B), and the bicipital groove axis relative to the TEA (angle C) were made with comparison of the measurement properties of each. RESULTS: Humeral retroversion relative to the TEA was 23.7° ± 8° (range, 0.2°-48.7°; 95% confidence interval, 22°-26°). The humeral articular axis was retroverted to the bicipital groove axis (angle B) by 33.5° ± 9.4° (range, 15.5°-61.7°; 95% confidence interval, 32°-35°). Overall inter-rater reliability was 0.88. DISCUSSION: Measurement of humeral head retroversion relative to the bicipital groove is not inferior to the gold-standard measurement. The bicipital groove is present both on preoperative imaging and in the operative field, making it a potential reference landmark for accurate reproduction of humeral version in shoulder arthroplasty.

Fatal 3-Nitropropionic Acid Poisoning after Consuming Coconut Water.

We describe the fatal course of a patient with initial symptoms of vomiting and nausea who developed symptoms of dystonia, encephalopathy, and coma. The cause of death was poisoning with 3-nitropropionic acid from coconut water spoiled with the fungus Arthrinium saccharicola. We present the clinical findings and forensic analysis.

Hydrogen Bonding between Tetrahydrocannabinol and Vitamin E Acetate in Unvaped, Aerosolized, and Condensed Aerosol e-Liquids.

Vitamin E acetate (VEA) has recently been identified as a potential chemical of concern in the investigation of e-cigarette, or vaping, product use associated lung injury (EVALI). According to the Centers for Disease Control and Prevention (CDC), most patients report a history of using tetrahydrocannabinol (THC)-containing e-cigarette or vaping products; approximately 50% of the THC-containing vaping products examined by the Food and Drug Administration (FDA) in this investigation have been found to contain VEA. This letter demonstrates that THC and VEA exist in the unvaped e-liquids, vaped e-liquids, and the aerosol produced from vaporizing the mixture, as a hydrogen bonded THC/VEA complex linked by the THC hydroxyl and VEA carbonyl groups. Additional work should therefore be considered to investigate what happens to this complex in the lungs.

Identification of the designer steroid Androsta-3,5-diene-7,17-dione in a dietary supplement.

A liquid chromatography-mass spectrometry (LC-MS) screen for known anabolic-androgenic steroids in a dietary supplement product marketed for "performance enhancement" detected an unknown compound having steroid-like spectral characteristics. The compound was isolated using high performance liquid chromatography with ultraviolet detection (HPLC-UV) coupled with an analytical scale fraction collector. After the compound was isolated, it was then characterized using gas chromatography with simultaneous Fourier Transform infrared detection and mass spectrometry (GC-FT-IR-MS), liquid chromatography-high resolution accurate mass-mass spectrometry (LC-HRAM-MS) and nuclear magnetic resonance (NMR). The steroid had an accurate mass of m/z 285.1847 (error-0.57 ppm) for the protonated species [M + H]+ , corresponding to a molecular formula of C19 H24 O2 . Based on the GC-FT-IR-MS data, NMR data, and accurate mass, the compound was identified as androsta-3,5-diene-7,17-dione. Although this is not the first reported identification of this designer steroid in a dietary supplement, the data provided adds information for identification of this compound not previously reported. This compound was subsequently detected in another dietary supplement product, which contained three additional active ingredients.

Identification of the anabolic steroid 6ß-chlorotestosterone in a dietary supplement.

Capsules that were labeled to be performance-enhancing dietary supplements obtained during an investigation were found to contain an unrecognized steroid-like substance. This compound was isolated by liquid chromatography (LC) fraction collection and characterized using several qualitative analytical techniques, including ultraviolet (UV) spectroscopy, gas chromatography-mass spectrometry (GC-MS), liquid chromatography-high resolution accurate mass-mass spectrometry (LC-HRAM-MS), as well as 1 H, 13 C, and two-dimensional nuclear magnetic resonance (NMR) spectrometry. This multi-technique analytical approach was used to identify the designer steroid as 6ß-chloro-4-androsten-17ß-ol-3-one (6ß-chlorotestosterone), an analog of testosterone about which little has been published.

Forensic Drug Identification, Confirmation, and Quantification Using Fully Integrated Gas Chromatography with Fourier Transform Infrared and Mass Spectrometric Detection (GC-FT-IR-MS).

This manuscript is a continuation of a recent study that described the use of fully integrated gas chromatography with direct deposition Fourier transform infrared detection and mass spectrometric detection (GC-FT-IR-MS) to identify and confirm the presence of sibutramine and AB-FUBINACA. The purpose of the current study was to employ the GC-FT-IR portion of the same instrument to quantify these compounds, thereby demonstrating the ability to identify, confirm, and quantify drug substances using a single GC-FT-IR-MS unit. The performance of the instrument was evaluated by comparing quantitative analytical figures of merit to those measured using an established, widely employed method for quantifying drug substances, high performance liquid chromatography with ultraviolet detection (HPLC-UV). The results demonstrated that GC-FT-IR was outperformed by HPLC-UV with regard to sensitivity, precision, and linear dynamic range (LDR). However, sibutramine and AB-FUBINACA concentrations measured using GC-FT-IR were not significantly different at the 95% confidence interval compared to those measured using HPLC-UV, which demonstrates promise for using GC-FT-IR as a semi-quantitative tool at the very least. The most significant advantage of GC-FT-IR compared to HPLC-UV is selectivity; a higher level of confidence regarding the identity of the analyte being quantified is achieved using GC-FT-IR. Additional advantages of using a single GC-FT-IR-MS instrument for identification, confirmation, and quantification are efficiency, increased sample throughput, decreased consumption of laboratory resources (solvents, chemicals, consumables, etc.), and thus cost.

Description of a Mass Poisoning in a Rural District in Mozambique: The First Documented Bongkrekic Acid Poisoning in Africa.

Background: On 9 January 2015, in a rural town in Mozambique, >230 persons became sick and 75 died of an illness linked to drinking pombe, a traditional alcoholic beverage. Methods: An investigation was conducted to identify case patients and determine the cause of the outbreak. A case patient was defined as any resident of Chitima who developed any new or unexplained neurologic, gastrointestinal, or cardiovascular symptom from 9 January at 6:00 am through 12 January at 11:59 pm. We conducted medical record reviews, healthcare worker and community surveys, anthropologic and toxicologic investigations of local medicinal plants and commercial pesticides, and laboratory testing of the suspect and control pombe. Results: We identified 234 case patients; 75 (32%) died and 159 recovered. Overall, 61% of case patients were female (n = 142), and ages ranged from 1 to 87 years (median, 30 years). Signs and symptoms included abdominal pain, diarrhea, vomiting, and generalized malaise. Death was preceded by psychomotor agitation and abnormal posturing. The median interval from pombe consumption to symptom onset was 16 hours. Toxic levels of bongkrekic acid (BA) were detected in the suspect pombe but not the control pombe. Burkholderia gladioli pathovar cocovenenans, the bacteria that produces BA, was detected in the flour used to make the pombe. Conclusions: We report for the first time an outbreak of a highly lethal illness linked to BA, a deadly food-borne toxin in Africa. Given that no previous outbreaks have been recognized outside Asia, our investigation suggests that BA might be an unrecognized cause of toxic outbreaks globally.

Evaluation of selenium in dietary supplements using elemental speciation.

Selenium-enriched dietary supplements containing various selenium compounds are readily available to consumers. To ensure proper selenium intake and consumer confidence, these dietary supplements must be safe and have accurate label claims. Varying properties among selenium species requires information beyond total selenium concentration to fully evaluate health risk/benefits A LC-ICP-MS method was developed and multiple extraction methods were implemented for targeted analysis of common "seleno-amino acids" and related oxidation products, selenate, selenite, and other species relatable to the quality and/or accuracy of the labeled selenium ingredients. Ultimately, a heated water extraction was applied to recover selenium species from non-selenized yeast supplements in capsule, tablet, and liquid forms. For selenized yeast supplements, inorganic selenium was monitored as a means of assessing selenium yeast quality. A variety of commercially available selenium supplements were evaluated and discrepancies between labeled ingredients and detected species were noted.

Identification of the potent toxin bongkrekic acid in a traditional African beverage linked to a fatal outbreak.

In January 2015, 75 people died and 177 were hospitalized in the Mozambique village of Chitima after attending a funeral. The deaths were linked to the consumption of a traditional African beverage called pombe. Samples of the suspect pombe were subjected to myriad analyses and compared to a control sample. Ultimately, non-targeted liquid chromatography-mass spectrometry screening revealed the presence of the potent toxin bongkrekic acid, and its structural isomer, isobongkrekic acid. Quantitative analysis found potentially fatal levels of these toxins in the suspect pombe samples. Bongkrekic acid is known to be produced by the bacterium Burkholderia gladioli pv. cocovenenans. This bacterium could not be isolated from the suspect pombe, but bacteria identified as B. gladioli were isolated from corn flour, a starting ingredient in the production of pombe, obtained from the brewer's home. When the bacteria were co-plated with the fungus Rhizopus oryzae, which was also isolated from the corn flour, synergistic production of bongkrekic acid was observed. The results suggest a mechanism for bongkrekic acid intoxication, a phenomenon previously thought to be restricted to specific regions of Indonesia and China.

Contamination of the Surgical Field with Propionibacterium acnes in Primary Shoulder Arthroplasty.

BACKGROUND: Propionibacterium acnes is a common pathogen identified in postoperative shoulder infection. It has been shown to be present in culture specimens during primary shoulder arthroplasty; however, recent work has suggested that it is most likely to be a contaminant. Our aim was to identify the potential sources of contamination in shoulder arthroplasty. METHODS: Tissue swabs were obtained for microbiological analysis from consecutive patients undergoing primary shoulder arthroplasty. Routine surgical technique was maintained, and 5 specimens were taken from different sites: (1) the subdermal layer, (2) the tip of the surgeon's glove, (3) the inside scalpel blade (used for deeper incision), (4) the forceps, and (5) the outside scalpel blade (used for the skin incision). RESULTS: Forty patients (25 female patients and 15 male patients) were included. Thirteen (33%) of the 40 patients had at least 1 culture specimen positive for P. acnes. Two (8%) of the 25 female patients and 11 (73%) of the 15 male patients had ≥1 culture specimen positive for P. acnes. The most common site of growth of P. acnes was the subdermal layer (12 positive samples), followed by the forceps (7 positive samples), the tip of the surgeon's glove (7 positive samples), the outside scalpel blade (4 positive samples), and the inside scalpel blade (1 positive sample). There were 27 of 75 swabs that were positive on culture for P. acnes in male patients compared with 4 of 125 swabs in female patients. Male patients had 66 times (95% confidence interval, 6 to 680 times) higher odds of having a positive culture indicating subdermal colonization compared with female patients (p < 0.001). CONCLUSIONS: P. acnes is a common contaminant of the surgical field in primary shoulder arthroplasty. The subdermal layer may be the source of this contamination, and the prevalence of P. acnes in the surgical wound may be due to the surgeon's manipulation with gloves and instruments. Our findings are consistent with those regarding the increased rates of P. acnes bacterial load and intraoperative growth in male patients compared with female patients. CLINICAL RELEVANCE: P. acnes is likely to be spread throughout the surgical field from the subdermal layer via soft-tissue handling by the surgeon and instruments. Strategies need to be utilized to minimize this contact and to reduce the chance of colonization.

Analysis of trace amounts of adulterants found in powders/supplements utilizing Raman spectroscopy coupled to direct analyte-probed nanoextraction-nanospray ionization-mass spectrometry.

In the United States, all food products have to be regulated to inform the consumers of the ingredients contained within. Some ingredients are not included on the label and yet are still found in the products. Presented is a Raman imaging technique for rapid, nondestructive, and spatially relevant localization of adulterants in powders. Raman spectroscopy followed by direct analyte-probed nanoextraction coupled to nanospray ionization-mass spectrometry allows rapid determination of the presence of each adulterant, leading to positive identifications such as melamine. The location and identification of these trace particles can then be extracted using a nanomanipulator. The nanomanipulation technique uses a solvent filled capillary tip which can be positioned on the particle of interest. Direct mass spectrometric analysis via nanospray of the particulate of interest eliminates time consuming chromatographic techniques prior to mass spectrometry analysis. This coupled technique combines rapid Raman spectroscopy techniques with direct mass spectrometry to confirm the presence of an adulterant. This technique was applied to an FDA supplied test sample, in which sibutramine, phenolphthalein, and melamine were confirmed to be present.

Serial MRI and clinical assessment of cyclops lesions.

PURPOSE: 'Clinical cyclops syndrome' is associated with pain and a palpable 'clunk' at terminal extension with the loss of full extension. The aims of this prospective controlled study were: (1) to assess whether the minimal debridement of the ACL stump and notch is associated with an increased incidence of clinical cyclops lesions, (2) to look at the incidence and natural history of 'MRI cyclops' lesions using serial MRI's and (3) to assess whether 'MRI cyclops' lesions are associated with the loss of extension. METHODS: Forty-eight patients were randomized for ACL reconstruction into standard (23) and minimal debridement (24) techniques. One patient was excluded from the study. All patients underwent MR scanning postoperatively at 2, 6 and 12 months, together with the clinical assessment using a KT-1000 arthrometer and International Knee Documentation Committee evaluation. All observations were made by investigators blinded to the surgical technique. RESULTS: There was no statistical difference in the incidence of cyclops lesions between the two groups (n.s.). The overall incidence of cyclops lesions was 46.8% (22 of 47). The natural history is variable with some getting larger, smaller or remaining static in size. Of patients with cyclops lesions, 17 patients (77%) had cyclops lesions in the setting of full extension. Five patients (23%) had loss of extension at 12 months with no MRI cyclops detected at 2 months. CONCLUSIONS: The natural history is variable; although once present, the majority of cyclops remain static or regress in size. The onset of cyclops lesions is usually between 6- and 12-month post-ACL reconstruction. Minimal debridement does not lead to an increased incidence of clinical cyclops lesions. The authors conclude that loss of extension is multi-factorial, and there is a discrepancy between what we term 'MRI cyclops' and true 'clinical cyclops'. LEVEL OF EVIDENCE: Case-control study, Level II.

Formation of cold ion-neutral clusters using superfluid helium nanodroplets.

A strategy for forming and detecting cold ion-neutral clusters using superfluid helium nanodroplets is described. Sodium cations generated via thermionic emission are directed toward a beam of helium droplets that can also pick up neutral molecules and form a cluster with the captured Na(+). The composition of the clusters is determined by mass spectrometric analysis following a desolvation step. It is shown that the polar molecules H(2)O and HCN are picked up and form ion-neutral clusters with sizes and relative abundances that are in good agreement with those predicted by the statistics used to describe neutral cluster formation in helium droplets. [Na(H(2)O)(n)](+) clusters containing six to 43 water molecules were observed, a size range of sodiated water clusters difficult to access in the gas phase. Clusters containing N(2) were in lower abundance than expected, suggesting that the desolvation process heats the clusters sufficiently to dissociate those containing nonpolar molecules.