Improved detection of drugs of abuse using high-performance ion mobility spectrometry with electrospray ionization (ESI-HPIMS) for urine matrices

Reliable Detection of Chemical Warfare Agents Using High Kinetic Energy Ion Mobility Spectrometry

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) ionize and separate ions at reduced pressures of 10-40 mbar and over a wide range of reduced electric field strengths E/N of up to 120 Td. Their reduced operating pressure is distinct from that of conventional drift tube ion mobility spectrometers that operate at ambient pressure for trace compound detection. High E/N can lead to a field-induced fragmentation pattern that provides more specific structural information about the analytes. In addition, operation at high E/N values adds the field dependence of ion mobility as an additional separation dimension to low-field ion mobility, making interfering compounds less likely to cause a false positive alarm. In this work, we study the chemical warfare agents tabun (GA), sarin (GB), soman (GD), cyclosarin (GF) and sulfur mustard (HD) in a HiKE-IMS at variable E/N in both the reaction and the drift region. The results show that varying E/N can lead to specific fragmentation patterns at high E/N values combined with molecular signals at low E/N. Compared to the operation at a single E/N value in the drift region, the variation of E/N in the drift region also provides the analyte-specific field dependence of ion mobility as additional information. The accumulated data establish a unique fingerprint for each analyte that allows for reliable detection of chemical warfare agents even in the presence of interfering compounds with similar low-field ion mobilities, thus reducing false positives.

Opioid cutting agents for use as internal standards in ion mobility spectrometry (IMS)

Opioids have become a serious public health concern over the last decade. These compounds are commonly found mixed, or cut, with safer compounds to make the opioids appear unadulterated while also enhancing the psychoactive effect on the user. Commercial benchtop and handheld IMS devices are capable of detection but published reduced ion mobility (K₀) values, used to identify the target analytes with IMS instrumentation, have shown variability. This lack of agreement, even for compounds used for calibration, is often due to the effects of drift tube temperature, drift gas water vapor levels and the use in-house built instrumentation rather than commercial equipment. Multiple reports exist on assessment of IMS reference standards but a single, consensus universal standard does not exist. Assessment of opioid cutting agents as internal standards is a worthwhile pursuit if precise and accurate K₀ values are obtained. The effects of drift gas water vapor content and drift tube temperature were used to evaluate the cutting agents. The K₀ values of papaverine, a representative opioid with a similar K₀ value to heroin and fentanyl, were calculated with respect to quinine and were in agreement with literature data. The use of quinine as an internal standard also improved precision relative to the instrument standard and shows promise in the application presented here.

How to Improve the Resolving Power of Compact Electrospray Ionization Ion Mobility Spectrometers

Every drift tube ion mobility spectrometer (IMS) has an optimum drift voltage to reach maximum resolving power. This optimum depends, among other things, on the temporal and spatial width of the injected ion packet and the pressure within the IMS. A reduction of the spatial width of the injected ion packet leads to improved resolving power, higher peak amplitudes when operating the IMS at optimum resolving power, and thus a better signal-to-noise ratio despite the reduced number of injected ions. Hereby, the performance of electrospray ionization (ESI)-IMS can be considerably improved. By setting the ion shutter opening time to just 5 μs and slightly increasing the pressure, a high resolving power R_P > 150 can be achieved with a given drift length of just 75 mm. At such high resolving power, even a mixture of the herbicides isoproturon and chlortoluron having similar ion mobility can be well separated despite short drift length.

A High-Throughput Ion Mobility Spectrometry-Mass Spectrometry Screening Method for Opioid Profiling

In 2017, the United States Department of Health and Human Services declared the widespread misuse and abuse of prescription and illicit opioids an epidemic. However, this epidemic dates back to the 1990s when opioids were extensively prescribed for pain management. Currently, opioids are still recommended for pain management, and given their abuse potential, rapid screening is imperative for patient treatment. Of particular importance is assessing pain management patient compliance, where evaluating drug use is crucial for preventing opioid abuse and potential overdoses. In this work, we utilized drift tube ion mobility spectrometry coupled with mass spectrometry (DTIMS-MS) to develop a rapid screening method for 33 target opioids and opioid urinary metabolites. Collision cross section values were determined for all target molecules using a flow-injection DTIMS-MS method, and clear differentiation of 27 out of the 33 opioids without prior chromatographic separation was observed when utilizing a high resolution demultiplexing screening approach. An automated solid phase extraction (SPE) platform was then coupled to DTIMS-MS for 10 s sample-to-sample analyses. This SPE-IMS-MS approach enabled the rapid screening of urine samples for opioids and presents a major improvement in sample throughput compared to traditional chromatographic analyses coupled with MS, which routinely take several minutes per sample. Overall, this vast reduction in analysis time facilitates a faster turn-around for patient samples, providing great benefits to clinical applications.

Accelerating prototyping experiments for traveling wave structures for lossless ion manipulations

Traveling wave structures for lossless ion manipulation (TW-SLIM) has proven a valuable tool for the separation and study of gas-phase ions. Unfortunately, many of the traditional components of TW-SLIM experiments manifest practical and financial barriers to the technique's broad implementation. To this end, a series of technological innovations and methodologies are presented which enable for simplified SLIM experimentation and more rapid TW-SLIM prototyping. In addition to the use of multiple independent board sets that comprise the present SLIM system, we introduce a low-cost, multifunctional traveling wave generator to produce TW within the TW-SLIM. This square-wave producing unit proved effective in realizing TW-SLIM separations compared to traditional approaches. Maintaining a focus on lowering barriers to implementation, the present set of experiments explores the use of on-board injection (OBI) methods, which offer potential alternatives to ion funnel traps. These OBI techniques proved feasible and the ability of this simplified TW-SLIM platform to enhance ion accumulation was established. Further experimentation regarding ion accumulation revealed a complexity to ion accumulation within TW-SLIM that has yet to be expounded upon. Lastly, the ability of the presented TW-SLIM platform to store ions for extended periods (1 s) without significant loss (<10%) was demonstrated. The aforementioned experiments clearly establish the efficacy of a simplified TW-SLIM platform which promises to expand adoption and experimentation of the technique.

Development of a high-throughput differential mobility separation-tandem mass spectrometry (DMS-MS/MS) method for clinical urine drug testing

INTRODUCTION

Differential mobility separation (DMS) is an analytical technique used for rapid separation of ions and isomers based on gas phase mobility prior to entering a mass spectrometer for analysis. The entire DMS process is accomplished in fewer than 20 ms and can be used as a rapid alternative to chromatographic separation.

OBJECTIVE

The primary objective was to evaluate the utility of DMS-tandem mass spectrometry (DMS-MS/MS) as a replacement for immunoassay-based clinical toxicology testing.

METHODS

A sensitive DMS-MS/MS method was developed and validated for simultaneous identification of 33 drugs and metabolites in human urine samples. After DMS optimization, the method was validated and used to screen 56 clinical urine samples. These results were compared to results obtained by immunoassay.

RESULTS

The DMS-MS/MS method achieved limits of detection ranging from 5 to 100 ng/mL. Moreover, the total analysis time was 2 min per sample. For the method performance evaluation, DMS-MS/MS results were compared with previously obtained urine toxicology immunoassay results. DMS-MS/MS showed higher sensitivity and identified 20% more drugs in urine, which were confirmed by LC-MS/MS.

CONCLUSION

The DMS-MS/MS as applied in our lab demonstrated the capability for rapid drug screening and provided better analytical performance than immunoassay.

Development of a sample pretreatment device integrating ultrasonication, centrifugation and ultrafiltration, its application on rapid on-site screening of illegally added chemical components in heat-clearing, detoxicating Chinese patent medicines followed by electrospray ionization-ion mobility spectrometry

In this paper, a simple and rapid sample pretreatment device integrating ultrasonication, centrifugation and ultrafiltration (UCU) was reported for preparation of trace analytes in complex matrices. The UCU device was composed of two parts, A and B. The sample and extraction solvent were put into Part B for ultrasonic extraction. Subsequently, Part A and Part B were integrated and sealed for centrifugation and ultrafiltration. Finally, the ultrafiltrate in Part A was taken out for subsequent detection. After optimization, the device was applied to rapid on-site screening of five illegally added chemical components in heat-clearing and detoxicating Chinese patent medicines by combining with electrospray ionization-ion mobility spectrometry (ESI-IMS). The method showed good performance in terms of linearity with correlation coefficients (R²) above 0.9976 and limits of detection (LODs) in the range of 0.049-0.391 μg mL^-1. The recoveries were from 96.5 % to 100.8 %. The whole analysis process was within 11 min. The proposed method was further compared with other methods reported in the literature and the advantages and considerations were also explored. The results demonstrated that it was a simple, fast and accurate technique. The establishment of this method not only greatly improved the experimental efficiency but also avoided potential sample pollution brought by multiple sample transfer, and could provide a powerful means for rapid on-site analysis of trace analytes in complex matrices.

Simulating, Predicting, and Minimizing False Peaks for Hadamard Transform Ion Mobility Spectrometry

Multiplexing techniques, including the Hadamard transform, are widely used in the recovery of weak signals from high-level noise. Hadamard transform ion mobility spectrometry (HT-IMS), however, can suffer serious drawbacks due to false peaks. False peaks in HT-IMS are generally attributed to nonperfect gating behavior. This paper confirmed that the origin of false peaks in HT-IMS is not generally due to ion gating but rather to peak shifts by Coulombic repulsion of the ion packets inside the drift tube. The amplitudes of these false peaks are determined by the number of ions inside the ion packets. This phenomenon is simulated and confirmed by the convolution of the spectrum with a shifted s-sequence to reproduce the artifact peaks with the exact position, amplitude, and profile. Two approaches, including preoffset sequence modulation and post-data processing, were evaluated to mitigate the false peaks in HT-IMS, and both methods can work effectively.

Quantitative analysis of flavonols, flavonol glycoside and homoisoflavonoids in Polygonatum verticillatum using UHPLC-DAD-QTOF-IMS and evaluation of their antioxidant potential

INTRODUCTION

Polygonatum is widely used as a part of food in different regions of the world which covers five main categories such as drinks, vegetables, snacks, staple and seasoning foods. Presently, no analytical method is available for the quality control of Polygonatum.

OBJECTIVE

Development and validation of a method using ultrahigh-performance liquid chromatography diode array detector quadrupole time-of-flight (UHPLC-DAD/QTOF) technique for the estimation of six compounds including a flavonol glycoside [rutin (1)], two flavonols [quercetin (2) and kaempherol (3)] and three homoisoflavonoids [5,7-dihydroxy-3-(2-hydroxy-4-methoxybenzyl)-chroman-4-one (4), 5,7-dihydroxy-3-(2-hydroxy-4-methoxybenzyl)-8-methylchroman-4-one (5) and 5,7-dihydroxy-3-(4-methoxybenzyl)-8-methylchroman-4-one (6)]. In addition, screening of extract, fractions and compounds of P. verticillatum for antioxidant activity was also determined.

METHODOLOGY

The separation was achieved on C-18 column using acetonitrile and water containing 0.1% formic acid. The method was validated as per ICH (International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use) guidelines. The validated method was applied for the simultaneous identification and quantification of compounds 1-6 in extract (E) and fractions (F1-F4) of P. verticillatum. Furthermore, antioxidant potential of E, F1 and F2 and compounds was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) assay.

RESULTS

The method was within the linear range (r² ) of 0.982 to 0.999, precise (intra- and inter-day percentage relative standard deviations < 2.72 and 2.26) and accurate with recoveries (89.1-98.3%). The limit of detection and limit of quantification were in the ranges 0.02-0.16 and 0.06-0.48 ng/mL, respectively. Compounds 1-6 were quantified in all the samples. Compounds 1, 2 and 5 showed higher activity with half maximal inhibitory concentration (IC₅₀ ) values 0.41, 0.39, 0.72 at 10, 20 and 30 μg/mL, respectively.

CONCLUSION

Developed method will be helpful to assess the quality of P. verticillatum raw material and their derived products.

Combined secondary electrospray and corona discharge ionization (SECDI) for improved detection of explosive vapors using drift tube ion mobility spectrometry

Secondary electrospray corona discharge ionization (SECDI) combines the principles of secondary electrospray ionization (SESI) and corona discharge (CD) to achieve higher sensitivity, which is demonstrated through the detection of 2,4,6-trinitrotoluene (TNT) and 2,6-dinitrotoluene (2,6-DNT) vapors using ion mobility spectrometry (IMS). Using SECDI, enhancements in the IMS signal for TNT and 2,6-DNT vapors at trace concentrations are as much as 2-26 times that observed with CD or SESI alone. The enhancement in sensitivity is hypothesized to result from an increase in ionization efficiency driven by a higher number of reactant ions associated with SECDI compared to either technique individually. The ability of SECDI to achieve higher sensitivity without the aid of dopant molecules demonstrates its merit as an alternative ionization technique.

Synthetic Small Molecule Characterization and Isomer Discrimination Using Gas-Phase Hydrogen-Deuterium Exchange IMS-MS

Ion mobility spectrometry-mass spectrometry (IMS-MS) combined with gas-phase hydrogen-deuterium exchange has been used to characterize novel psychoactive substances (NPSs) which are small synthetic compounds designed to mimic the effects of other illicit substances. Here, NPSs containing labile heteroatom hydrogens were evaluated for HDX reactivity in the presence of either deuterated water (D₂O) or ammonia (ND₃) within the drift tube. An initial evaluation of exchange propensity was performed for six NPSs. Five compounds exchanged in the presence of ND₃ while only one NPS (benzyl piperazine) exchanged with D₂O. The exchange mechanism of D₂O requires stabilization with a nearby charged site; the diamine ring of benzyl piperazine provided this charge site at a fixed length. Three disubstituted benzene isomers ( o-, m-, and p-fluorophenyl piperazine) containing the diamine ring structure and a fluorine atom were subsequently analyzed. Having identical isotopic composition and nearly identical drift time distributions, these isomers could not be distinguished by IMS-MS alone. However, upon undergoing HDX in the drift tube, a t test of means (α = 0.05) showed that discrimination was possible if the exchange data from both reagent gases were included. Molecular dynamics simulations show that the proximity of the fluorine to the diamine ring hinders the dihedral angle rotation between the benzene and the diamine ring; this may partially account for the observed exchange differences.

Fabric-phase sorptive extraction coupled with ion mobility spectrometry for on-site rapid detection of PAHs in aquatic environment

The contamination of water is a high risk to human health, so there is an urgent need to rapidly detect water pollution in the field. Ion mobility spectrometry (IMS) is suitable for on-site analysis with the merit of rapid analysis and compact size. In this study, we developed a new method which coupled fabric phase sorptive extraction (FPSE) with IMS for rapid detection of polycyclic aromatic hydrocarbons (PAHs) in water present in the field. Polydimethylsiloxane (PDMS) was coated on the glass fiber cloth through a sol-gel reaction. After extracting the PAHs in water, the fabric coated PDMS could be directly put into the inlet of IMS instrument for thermal desorption. The PAHs were analyzed by the IMS instrument operated in the positive ion mode with a corona discharge (CD) ionization source. The primary parameters affecting extraction efficiency such as extraction time, extraction temperature, and ionic strength were investigated and optimized by using phenanthrene (Phe), benzo[a]anthracene (BaA) and benzo[a]pyrene (BaP) as model compounds. Under the optimal conditions, the FPSE-IMS detection limits were 5 ng ml^-1,8 ng ml^-1 and 10 ng ml^-1 respectively. Satisfactory recoveries were obtained in the range from 80.5% to 100.5% by testing the spiked real water samples and validated by the standard method（HJ487-2009）. Based on the results, the method of FPSE-IMS could be feasibly applied for monitoring the water quality on-site and providing early warning in the field.

New Advances in Toxicological Forensic Analysis Using Mass Spectrometry Techniques

This article reviews mass spectrometry methods in forensic toxicology for the identification and quantification of drugs of abuse in biological fluids, tissues, and synthetic samples, focusing on the methodologies most commonly used; it also discusses new methodologies in screening and target forensic analyses, as well as the evolution of instrumentation in mass spectrometry.

Determination of E/N Influence on K0 Values within the Low Field Region of Ion Mobility Spectrometry

The established theory of ion motion within weak electric fields predicts that reduced ion mobility (K₀) remains constant as a function of the ratio of electric field strength to drift gas number density (E/N). However, upon increasing the accuracy and precision of K₀ value measurements during a previous study, a new relationship was seen in which the K₀ values of ions decreased as a function of increasing E/N at field strengths below 4 Td. Here the effect of E/N on the K₀ value of an ion has been investigated in order to validate the reality of the phenomenon and determine its cause. The pertinent measurements of voltage and drift time were verified in order to ensure the authenticity of the trend and that it was not a result of a systematic error in parametric measurements. The trend was also replicated on a separate ion mobility spectrometer drift tube in order to further validate its authenticity. As a result, the theory of ion motion within weak electric fields should be revised to reflect the behavior seen here.

Study on Mobility, Distribution and Rapid Ion Mobility Spectrometry Detection of Seven Pesticide Residues in Cucumber, Apple, and Cherry Tomato

This research explores the mobility and distribution rules of simazine, acetamiprid, hexazinone, paclobutrazol, amitraz, clofentezine, and boscalid in the pulp and peel of apple, cucumber, and cherry tomato. A laboratory test was carried out by treating the matrices with standard solution for different periods of time. The percentage sorption of pesticides ranged from 0.02 to 89.3% for the three matrices. The pesticides' distribution was also determined, and all pesticides showed ratio values (Q) between pulp and peel concentrations in the three matrices of <0.8, which proved that the highest pesticides' content was found in the peel. In addition, a rapid and simple process combining a surface swab capture method and pulse glow discharge-ion mobility spectrometry (PGD-IMS) detection was established for the detection of pesticides on matrix surfaces. In the swab method, the whole matrix surface was swabbed manually by swab sticks, and swab sticks were agitated in acetonitrile to release the pesticides. The releasing factors of pesticides in the three matrices were calculated. The linearity, LOD, LOQ, and matrix effect were investigated to assess the applicability of the swab-IMS process in practical analysis. The swab-IMS method is rapid, sensitive, and quantitative and can be achieved in the field.

Greatly Increasing Trapped Ion Populations for Mobility Separations Using Traveling Waves in Structures for Lossless Ion Manipulations

The initial use of traveling waves (TW) for ion mobility (IM) separations using structures for lossless ion manipulations (SLIM) employed an ion funnel trap (IFT) to accumulate ions from a continuous electrospray ionization source and was limited to injected ion populations of ∼106 charges due to the onset of space charge effects in the trapping region. Additional limitations arise due to the loss of resolution for the injection of ions over longer periods, such as in extended pulses. In this work a new SLIM "flat funnel" (FF) module has been developed and demonstrated to enable the accumulation of much larger ion populations and their injection for IM separations. Ion current measurements indicate a capacity of ∼3.2 × 108 charges for the extended trapping volume, over an order of magnitude greater than that of the IFT. The orthogonal ion injection into a funnel shaped separation region can greatly reduce space charge effects during the initial IM separation stage, and the gradually reduced width of the path allows the ion packet to be increasingly compressed in the lateral dimension as the separation progresses, allowing efficient transmission through conductance limits or compatibility with subsequent ion manipulations. This work examined the TW, rf, and dc confining field SLIM parameters involved in ion accumulation, injection, transmission, and IM separation in the FF module using both direct ion current and MS measurements. Wide m/z range ion transmission is demonstrated, along with significant increases in the signal-to-noise ratios (S/N) due to the larger ion populations injected. Additionally, we observed a reduction in the chemical background, which was attributed to more efficient desolvation of solvent related clusters over the extended ion accumulation periods. The TW SLIM FF IM module is anticipated to be especially effective as a front end for long path SLIM IM separation modules.

Ultra-High Resolution Ion Mobility Separations Utilizing Traveling Waves in a 13 m Serpentine Path Length Structures for Lossless Ion Manipulations Module

We report the development and initial evaluation of a 13 m path length Structures for Lossless Manipulations (SLIM) module for achieving high resolution separations using traveling waves (TW) with ion mobility (IM) spectrometry. The TW SLIM module was fabricated using two mirror-image printed circuit boards with appropriately configured RF, DC, and TW electrodes and positioned with a 2.75 mm intersurface gap. Ions were effectively confined in field-generated conduits between the surfaces by RF-generated pseudopotential fields and moved losslessly through a serpentine path including 44 "U" turns using TWs. The ion mobility resolution was characterized at different pressures, gaps between the SLIM surfaces, and TW and RF parameters. After initial optimization, the SLIM IM-MS module provided about 5-fold higher resolution separations than present commercially available drift tube or traveling wave IM-MS platforms. Peak capacity and peak generation rates achieved were 246 and 370 s(-1), respectively, at a TW speed of 148 m/s. The high resolution achieved in the TW SLIM IM-MS enabled, e.g., isomeric sugars (lacto-N-fucopentaose I and lacto-N-fucopentaose II) to be baseline resolved, and peptides from an albumin tryptic digest were much better resolved than with existing commercial IM-MS platforms. The present work also provides a foundation for the development of much higher resolution SLIM devices based upon both considerably longer path lengths and multipass designs.

Chemometrics for ion mobility spectrometry data: recent advances and future prospects

This is the first comprehensive review on chemometric techniques used in ion mobility spectrometry data analysis.

Direct drug analysis from oral fluid using medical swab touch spray mass spectrometry

Fourteen common drugs of abuse were identified in spiked oral fluid (ng mL(-1) levels), analyzed directly from medical swabs using touch spray mass spectrometry (TS-MS), exemplifying a rapid test for drug detection. Multiple stages of mass analysis (MS(2) and MS(3)) provided identification and detection limits sought by international forensic and toxicological societies, Δ(9)-THC and buprenorphine excluded. The measurements were made using a medical swab as both the sampling probe and means of ionization. The adaptation of medical swabs for TS-MS analysis allows non-invasive and direct sampling of neat oral fluid. Data acquisition was rapid, seconds per drug, and MS(3) ensured reliable identification of illicit drugs. The reported data were acquired to investigate (i) ionization of common drugs from commercial swabs, (ii) ion intensity over spray duration, and (iii) dynamic range, all as initial steps in development of a quantitative method. The approach outlined is intended for point-of-care drug testing using oral fluid in clinical applications as well as in situ settings, viz. in forensic applications. The proof-of-concept results presented will require extension to other controlled substances and refinement in analytical procedures to meet clinical/legal requirements.