A new application of thermal ionization ion mobility spectrometry (TI–IMS) was presented for the fast determination of lithium ion (Li+) in serum samples. This research aims to provide a selective approach to facilitate lithium monitoring for bipolar patients. The method is based on an initial step of quick–burning the organic content of the diluted serum sample on a hot filament followed by the emission of alkali ions remained in the ash. The drift tube temperature was optimized to maximize the separation of signal from the other existing alkali ions, sodium (Na+) and potassium (K+). The filament temperature and the dilution ratio were also optimized for best observation of the Li+ signal among the excess amount of Na+ and K+. The best peak resolution was obtained at 1:200 dilution ratio and drift tube temperature of 160 °C. TI–IMS demonstrated high sensitivity in both diluted standard and serum sample solution (0.21 μM for LOD and 1.50 μM for LOQ). The Relative standard deviation of the lithium determination was obtained to be 5.4%. Method validation was conducted by comparing the results with those obtained through the inductively coupled plasma optical emission spectrometry (ICP–OES) method. A good agreement between the results was observed indicating that the TI–IMS method can be potentially applied to routine analysis of biological samples. Rapidity, ease of operation and low–cost analysis are superior features of the proposed technique over the traditional approaches.
Crown ethers with different ring sizes and substituents (18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, a chiral tetracarboxylic acid-18-crown-6 ether, dibenzo-21-crown-7, and dibenzo-30-crown-10) were evaluated as shift reagents to differentiate epimeric model peptides (tri-and tetrapeptides) using ion mobility mass spectrometry (IM-MS). The stable associates of peptide epimers with crown ethers were detected and examined using traveling-wave ion mobility time-of-flight mass spectrometer (Synapt G2-S HDMS) equipped with an electrospray ion source. The overall decrease of the epimer separation upon crown ether complexation was observed. The increase of the effectiveness of the microsolvation of a basic moiety - guanidine or ammonium group in the peptide had no or little effect on the epimer discrimination. Any increase of the epimer separation, which referred to the specific association mode between crown substituents and a given peptide sequence, was drastically reduced for the longer peptide sequence (tetrapeptide). The obtained results suggest that the application of the crown ethers as shift reagents in ion mobility mass spectrometry is limited to the formation of complexes differing in stoichiometry rather than it refers to a specific coordination mode between a crown ether and a peptide molecule.
In this study, first time a novel slug-flow microextraction (SFME) procedure named two-side SFME was developed and followed by ion mobility spectrometry equipped with corona discharge source (CD-IMS) for quantification of two abused drugs (amphetamine (AM) and methamphetamine (ME)) in urine samples. Regarding technique workflow, the organic extraction solvent (10 μL) was sandwiched between two portions of aqueous sample solution (the volume of each portion of sample solution was 5 μL) into a disposable glass capillary tube. The extraction of analytes was performed via the slug flows induced by the movements of the three liquids, which was conducted by tilting the glass capillary tube for several cycles. Finally, the extraction solvent was collected by a microsyringe and then injected (5 μL) into the CD-IMS. The effects of the effective parameters, including type of extraction solvent, number of tilting the glass capillary tube, and concentration of salt in sample solution were investigated. Under the optimized extraction condition (organic solvent: toluene; number of tilting the glass capillary tube: 10 times; concentration of salt: 5% (w/v)), the proposed two-side SFME/CD-IMS provided good linearity with coefficients of determination ≥0.993 over a concentration range of 25.0–2000.0 ng mL−1. Accordingly, acceptable limits of detection (S/N = 3) were 10.0 and 2.5 ng mL−1 for AM and ME, respectively. Furthermore, acceptable recoveries were ≥ 81.5, and ≥ 88.0% for AM and ME in a human urine sample, respectively, while repeatability and reproducibility ranged from 6.7 to 14.7% (n = 3).
An experimental study and comparison of spatial distributions of charged particles for conventional electrospray (ESI) and for dropless electrospray with a dynamic flow splitter of analyzed solution at atmospheric pressure and room temperature was carried out. Comparison of distributions shows that the characteristic regions of ion formation differ significantly. The obtained dropless electrospay spatial distributions are matched with inlet parameters of optimized transfer system of an ion mobility spectrometer (IMS) based on electrostatic focusing of the charged particles.
Ion Mobility Spectroscopy (IMS) is commonly used for in-situ rapid online detection of trace substances at atmospheric pressure. By selecting four types of Phthalic acid Ester (PAE) compounds as the quantitative research objects, studying the effects of the temperature of the mobility tube, the temperature of the sample desorbed heater and the electric field strength of the mobility region on the detection, analysing the microscopic process of ion reaction after the addition of reagent molecules using the Rectilinear Ion Trap Mass Spectrometer (RIT-MS), the paper preliminary studies the product ions of phthalic acid ester, and establish a method for rapid measurement of phthalic acid ester-like environmental hormones with ion mobility spectrometry. With the addition of ammonia reagent molecules, the detection limits of dimethyl phthalate, diethyl phthalate, dibutyl phthalate and butyl benzyl phthalate were 0.08 and 0.1, 0.09, 0.70 ng, respectively, and relative standard deviation RSD of 6 parallel measurements <6.3%. When used for the detection of phthalates in plastics, this method can quickly and easily screen products containing trace PAE-like contaminants.
Common challenge in gas analyzers such as Ion Mobility Spectrometers (IMS) integrated into a measurement system is the reduced analysis speed that is partially limited by the temporal carry-over of sample molecules. It is caused by adsorption and absorption of the molecules into the gas tubes of the analyzer. We studied the recovery times of common tube materials: polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyethylene (PE), steel 316 L, parylene C coated steel and Silconert® coated steel from organic combustion products. The tests were performed in two temperatures, at 25 °C and at 70 °C. In addition, detailed analysis was performed for PTFE tube material at 33, 50, 70 and 100 °C to observe the temperature relation of desorption. Uncoated steel was found to have the best performance in increased temperature applications due lack of absorption. Major advantages from coatings compared to plane steel were not found. Plastics were found suitable materials in lower temperatures where adsorption exceeds absorption.
The determination of ethylene with a field asymmetric ion mobility spectrometer, which can easily be constructed in-house, is described. The device makes use of a Krypton lamp for ionization. A rectangular pulse of 500 V(pp)at 1 MHz was employed as separation waveform in the drift tube rather than the commonly used less efficient bisinusoidal waveform. The calibration curve for the range from 670 ppb((V/V))to 67 ppm((V/V))was found to be highly linear with a correlation coefficient of r = 0.9999. The limit of detection was determined as 200 ppb((V/V)). The reproducibility was 4% (relative standard deviation). The device was found to be suitable for the determination of ethylene given off by fruit; 6 types of climacteric fruit were tested, namely apples, bananas, kiwi fruit, nectarines, pears and plums.
Ion mobility spectrometers (IMS) are able to detect ppt V -level concentrations of substances in gasses and in liquids within seconds. Due to the continuous increase in analytical performance and reduction of the instrument size, IMS are established nowadays in a variety of analytical field applications. In order to reduce the manufacturing effort and further enhance their widespread use, we have developed a simple manufacturing process for drift tubes based on a composite material. This composite material consists of alternating layers of metal sheets and insulator material, which are connected to each other in a mechanically stable and gastight manner. Furthermore, this approach allows the production of ion drift tubes in just a few steps from a single piece of material, thus reducing the manufacturing costs and efforts. Here, a drift tube ion mobility spectrometer based on such a composite material is presented. Although its outer dimensions are just 15 mm × 15 mm in cross section and 57 mm in length, it has high resolving power of R p = 62 and detection limits in the ppt V -range, demonstrated for ethanol and 1,2,3-trichloropropane.
Mefenamic acid (MFA), (2- [2, 3-dimethylphenyl amino] benzoic acid) is an acidic nonsteroidal anti-inflammatory drug (NSAID) that is widely used in veterinary medicine. Because of entering residue of mefenamic acid in drinking water, food products and indeed in the food chains, the potential risk on customer’s health increases. Therefore, the development of test methods for monitoring of this drug in animal tissue and food samples is needed. In this study, a combination of ultrasound metal-organic framework dispersive solid-phase extraction with ion mobility spectrometry was used for selective, sensitive and rapid determination of MFA residues in food samples. HKUST-1 (copper (II) benzene- 1, 3, 5- tricarboxylate) metal-organic framework (MOF) was synthesized in a green route and used as solid phase for extraction of MFA residues of real samples. Effective parameters such as extraction time, amount of sorbent, pH and were optimized to achieve the best extraction process. The Effect of ultrasonic waves on the desorption step in extraction was studied and results show using ultrasound waves causes an increase in extraction recovery from 68 to 97%. Under optimum conditions, the method exhibits the linear range of 2.0–150.0 μg L−1 (R2 = 0.9989) with a detection limit of 0.4 μg L−1 and a low relative standard deviation (˂ 5%). The proposed method was applied for the extraction and determination of trace amounts of MFA in real samples such as drinking water, milk, baby food, and body supplement powder.
Diazinon and phosalone are two pesticides widely used in agriculture and gardening. Because the residues of these pesticides in fruits, vegetable, and environment are dangerous for human and domestic animal health, their determination in different samples is of importance. In this work, ion mobility spectrometry in positive mode was used for determination of residues of diazinon and phosalone in pistachio. The calibration curves for these pesticides were obtained using standard solutions. The detection limits of diazinon and phosalone measured by ion mobility were 0.1 and 0.5 ppm, respectively. The pistachio samples were prepared from market and a garden near Qazvin (Iran). The measurements showed that there is no detectable phosalone in the samples, however, diazinon was detected in the pistachio of the garden. The diazinon residues in the opened- and closed-shell pistachios one day after spraying were 0.071 and 0.008 mg/kg, respectively. After 5 days, the diazinon residues reach 0.004 and 0.006 mg/kg, respectively.
Using Fourier-Transform ion gate modulation technique, we compare the ability of the tri-state ion shutter (3S-IS) to the two-state ion shutter (2S-IS) in separating three pairs of isomeric peptide including 1.Gly-Arg-Gly-Asp-Ser (GRGDS) / Ser-Asp-Gly-Arg-Gly (SDGRG); 2.Sar-Arg-Gly-Asp-Ser-Pro (SRGDSP) / Gly-Arg-Gly-Asp-Thr-Pro (GRGTP); 3.Kemptide / (Val(6), Ala(7))-Kemptide using electrospray ionization and ion mobility spectrometry. Mobility separation was evaluated for peptide individually and as simple mixtures. Baseline resolution of both singly and doubly charged ions of the isomeric pentapeptide mixture of GRGDS / SDGRG was attainable with the described IMS system using the 3S-IS configuration, illustrating the capacity of the present instrument to resolve isomeric compounds with differences in ion neutral collision cross section (CCS) of less than 1% for the singly charged ions. However, with the 2S-IS, both singly and doubly charged ions of the same peptide mixture were unresolved in the mobility domain. To our knowledge, this is the first-time baseline separation has been reported for the singly charged ions of the isomeric reversed sequence pentapeptide mixture using Fourier transformed drift tube IMS with nitrogen as the drift gas. For all the peptide mixtures, the ion counts for the ion mixture recorded with the 3S-IS were substantially higher (> 50%) in comparison to the 2S-IS. The resolving power of the instrument ranged between 82 to 128 for the target analyte ions analyzed in a mixture using the 3S-IS. Whereas, the resolving power of the 2S-IS ranged between 60 and 100 for the target analytes. Overall, a 20% increase in resolving power was obtained with the 3S-IS in comparison to the 2S-IS. Separation of the different isomeric peptide ion mixture depicted in this present study clearly shows the unique size-to-charge separation ability of IMS that complements the mass-to-charge ratio measurement capacity of mass spectrometry.
The drift voltage required for operating ion mobility spectrometers implies high voltage isolation of either the ion source or the detector. Typically, the detector is grounded due to the sensitivity of the small ion currents to interferences and thus higher requirements for signal integrity than the ion source. However, for certain ion sources, such as non-radioactive electron emitters or electrospray ionization sources, or for coupling with other instruments, such as gas or liquid chromatographs, a grounded ion source is beneficial. In this paper, we present an isolated data acquisition interface using a 16 bit, 250 kilosamples per second analog to digital converter and fiber optic transmitters and receivers. All spectra recorded via this new data acquisition interface and with a grounded ion source show the same peak shapes and noise when compared with a grounded detector, allowing additional freedom in design.
In this study, a new method based on electromembrane extraction (EME) followed by corona discharge ion mobility spectrometry (CD-IMS) was used for preconcentration and quantification of malachite green in water samples. In the EME procedure, the charged malachite green migrated into the supported liquid membrane (SLM) under an applied potential. The extraction efficiency of malachite green was assessed based on two phase EME under effective parameters including applied voltage, extraction time, pH of the sample solution, stirring rate, and salt addition in the sample solution. The analytical performance of the developed EME method was studied under the optimum extraction condition. The dynamic linear range and low limit of detection of the EME method were 5–250 ng mL−1 and 1.5 ng mL−1, respectively. The preconcentration factor of 150 and the RSD% of 3.8–7.6% were also achieved using EME method. Finally, the proposed method was successfully tested for the extraction and analysis of malachite green in different water samples.
It has recently been shown that accurate theoretical calculations can be used to calibrate a drift-tube mass spectrometer (DTMS) to measure gaseous ion mobilities accurate to within 0.6%. Here we present a new method for calibrating a DTMS instrument to obtain diffusion coefficients parallel to the electric field which are accurate to within 8%. This method is developed and verified by consideration of He+ (2S1/2) ions in He. We apply these techniques to determine transport coefficients for Ar+(2P3/2) and Ar2+ (3P2,1,0) ions in Ar gas at 300 K, with results given as a function of E/N, the ratio of electrostatic field strength to gas number density, in the range 30–210 Td. The measured mobilities are accurate within 0.8%; for Ar+ they agree within 1.5% with Monte Carlo simulations, and for both the cations and dications they are in excellent agreement with previous measurements. Our method gives new diffusion coefficients that agree within 5% with quantum Monte Carlo calculations.
In small planar differential mobility spectrometers with ambient pressure ion sources, both ions and neutral vapors of sample commonly flow from the ion source directly into and through the analyzer region. Although simple and convenient both for fabrication and operation, product ions derived from sample in this design may form clusters with neutral unreacted sample or matrix constituents particularly at vapor levels of 50 ppm or greater. Uncontrolled and changing levels of such neutrals cause concentration dependent formation of ion clusters with variations in compensation voltages of DMS spectra. Stable compensation voltages were achieved for product ions by extracting ions into a counter flow of purified gas excluding neutral vapors from ppm to percent levels. An interface with electric fields and purified air was placed between ion source and analyzer region and operated with both on-axis and orthogonal extraction of ions. Effectiveness of removal of neutrals was determined using variations in peak position for protonated monomers and proton bound dimers of dimethylmethylphosphate, significantly avoiding complications of ionization chemistry with high vapor concentrations of methylene chloride, iso-propanol, water, and methanol. In-silico modeling using COMSOL and SIMION clarified the flow of ions and gases in two modes of operation. Findings anticipate the development of multiple stages of DMS analyzers where vapors may be intentionally added as modifiers in one stage and removed before entering a subsequent stage.
The weaponization of organophosphorus compounds (OPCs) as nerve agents changed the needs in methods and technology for chemical warfare agent detection. Soldiers needed high-speed, on-site instruments to detect (OPCs) at the levels of parts per billion. First generation instrumentation used wet chemistry and suffered detrimental supply-line issues. Researchers sought dry chemistry solutions. The Chemical Agent Monitor (CAM) arose from discoveries in gas phase ion chemistry fundamentals and technology advances in mass spectrometry and ion mobility spectrometry. Ionization detectors were being widely developed for military purposes and resulted in kit for detecting human beings, exhaust fumes, explosives and nerve agents. The first ever portable analyser based on ion mobility spectrometry, CAM was capable of responding to both nerve and blister agent with little more than pushing a button to change polarity. It was legacy technology of ionization filtration and electron capture detection from the United States and Great Britain and was a joint US-UK development. The success of CAM promoted IMS research in academic fields, arguably contributing to the success of IMS as a viable field of research in North America and Britain. This article sets the foundations and history of the developments of early ionization detectors such as the Surface Potential Detector, Honeywell Ionization Detector, Detection by Ion Combination Effect (DICE), leading to the definitions of requirements for CAM, the scientists involved/instrumental in these developments, and the final field trials in 1978 which motivated the move into ion mobility spectrometry.
A simple, fast and reliable graphene oxide nanosheets based dispersive solid-phase microextraction methodology was described for the quantification of trace amount of ethambutol. The determination of ethambutol quantified with the aim of ion mobility spectroscopy as a sensitive, rapid, inexpensive and environmentally friendly instrument. Effects of relevant experimental parameters on the method efficiency such as pH, type of buffer and its volume, amount of absorbent, desorption solvent and extract time were investigated to reach the maximum efficiency of the proposed method. Under the optimum conditions, the calibration curve was linear in the range of 1 to 120 μg L−1 with the R-squared (R2) of 0.9990. The limit of detection for proposed method (n = 8) was 0.4 μg L−1 and the relative standard deviations were obtained (n = 8) 3.3% and 1.6% for 10 and 100 μg L−1, respectively. The proposed method was successfully applied for the preconcentration and determination of ethambutol in the different biological samples such as plasma, saliva, breast milk and artificial tear.
A Porous Aromatic Framework-48 with the nitro functional groups (PAF-48-NO2) has been introduced as a new porous structure for boosting electromembrane extraction efficiency followed by ion mobility spectrometer. We developed this method by immobilizing PAF-48-NO2 into the microporous polypropylene hollow fibers for the extraction of three model basic drugs including Ketamine, Methylphenidate and Tramadol with different polarities (log P: 3.35, 2.25, and 2.45, respectively). The best extraction condition was obtained as following: 2-nitro phenyl octyl ether as organic solvent containing 3.0 mg mL−1 of PAF-48-NO2 as sorbent, driving force of 180 V, extraction time of 20 min, pH of sample and acceptor solutions of 4.0 and 1.0, respectively, and stirring rate of 1000 rpm without any use of salt. The proposed PAF-48-NO2-electromembrane extraction method was found to be sensitive for the extraction of the model drugs in the optimized condition with good linearties (>0.998), limit of detection (1.5–3.6 ng mL−1), and high repeatability relative standard deviation 2.5–3.9%. In addition, the extraction efficiency of the proposed PAF-48-NO2-electromembrane extraction method was higher than the classical electromembrane extraction method. Finally, the proposed method was successfully applied for the determination of Ketamine, Methylphenidate, and Tramadol in various spiked samples such as urine and wastewater samples.
Differential Mobility Spectrometry (DMS), also called as FAIMS is a variation of atmospheric pressure ion mobility measurement techniques and is capable of providing information about the electric field - mobility dependence of ions. In this method, a combined electric field is used. This field consists of asymmetric oscillating electric field of high intensity and low static field component. Analytical information in DMS is 2-dimensional dependence of ionic current on oscillating field amplitude and the value of static field intensity. The measurement of DMS signal for whole ranges of both variables is time consuming and also generates lot of data. It is a disadvantage of DMS method, which limits the use of this otherwise powerful technology in real time applications that require a response time of few seconds. This paper presents a way to limit measurement time by heuristic knowledge of the properties of the data space and another method based on the concept of Shannon Entropy to find operating parameters satisfying both separation and signal to noise ratio requirements.
In the absence of high vacuum, the mobility of ions in an electric field is dependent on the charge, mass, shape and size of the ions. To achieve accurate calibration for ion mobility measurements, it is important to select calibrants with comparable physical properties to the molecular ions of interest. The size of an ion is often referred as its collision cross section (CCS). Currently, the information on the CCS values of various types of molecular ions are limited, thus representing a challenge to the calibration of ion mobility spectrometry. In this study, instead of finding a way to improve the calibration of ion mobility measurements, the intrinsic by-products of the conventional matrix-assisted laser desorption/ionization (MALDI) technique, namely MALDI matrix cluster (MAC) ions, are being used as internal references for ion mobility measurements. The standard MALDI matrix and sample preparation method are used. During the MALDI ionization process, MAC ions are generated and co-exist with the molecular ions of interest within the ion source. Our results indicate the MAC ions do possess suitable ion mobility characteristics, thus allowing the MAC ions to serve as internal reference for ion mobility measurements. The MAC ions cannot be used as internal standard or calibrants for ion mobility measurements, because their molecular structures as well as their CCS are unknown. However, the detection of MAC ions can allow us to determine whether the normal operation as well as the expected performance on the sensitivity and resolution of ion mobility spectrometry are achievable and reproducible. The MAC ions can also facilitate the transfer of specific experimental protocols between ion mobility instruments and/or laboratories. No extra materials, equipment or procedure are required for using MAC ions. For the proof of concept, all experimental work in this study was carried out on a traveling wave ion mobility mass spectrometry platform.
