Quantitative analysis of crude plasma extracts by ion trap tandem mass spectrometry

The ion trap mass spectrometer is a tandem-in-time instrument that has promise as an extremely sensitive device for practical tandem mass spectrometry assays. An approach for the quantitative analysis of unknown drug levels in crude extracts, using combined capillary gas chromatography and the ion trap mass spectrometer in the tandem mode, is described. One-gram plasma samples were spiked with an anti-inflammatory drug at levels of 1–100 ng, and with 50 ng of a chemical analog internal standard. Crude extracts of the plasma samples are analyzed by using scan functions that utilize combined radiofrequency (rf) and de voltages. The need for combined rf- and de-voltage sequences for analysis of such extracts is demonstrated by comparison to attempted analyses using only rf voltages. Limitations of the method are: (1) the need for accurate calibration of ionization times to obtain linear calibration lines, and (2) the lack of automatic gain control for scans using combined rf and dc voltages to control and optimize parent ion populations and to allow a simpler analysis of “unknowns. ”     

Trace Determination of Organic Compounds in Water by Direct Enrichment in Multichannel Thick Film Silicone Rubber Traps with Capillary Gas Chromatography

The application of Multichannel Silicone Rubber Traps for the direct analysis of organic compounds in water was studied. The optimum collection flow rate for a 10 mL sample was found to be ca. 150 μL·min^–1. The effect of methanol on the retention power of the trap was evaluated. The addition of a methanol fraction of up to 40% to the water standards did not show any loss in collection efficiency. It was shown that the extraction of organic compounds from water with the multichannel trap is uncomplicated, i. e. methanol is not required to achieve accurate analyses, concentration of the sample onto the trap is by gravity flow, and excess water remaining in the multichannel trap after water extraction is removed by centrifugation. With the use of the multichannel silicone rubber trap a wide boiling point range of compounds were analyzed from aqueous samples at levels of 1–4 μg·L^–1.     

On-line analysis of volatile chlorinated hydrocarbons in air by gas chromatography–mass spectrometry: Improvements in preconcentration and injection steps

An analytical system composed of a cryofocusing trap injector device coupled to a gas chromatograph with mass spectrometric detection (CTI-GC–MS) specific for the on-line analysis in air of volatile chlorinated hydrocarbons (VCHCs) (dichloromethane; chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) was developed. The cryofocusing trap injector was the result of appropriate low cost modifications to an original purge-and-trap device to make it suitable for direct air analysis even in the case of only slightly contaminated air samples, such as those from remote zones. The CTI device can rapidly and easily be rearranged into the purge-and-trap allowing water and air analysis with the same apparatus. Air samples, collected in stainless steel canisters, were introduced directly into the CTI-GC–MS system to realize cryo-concentration (at −120 °C), thermal desorption (at 200 °C) and for the subsequent analysis of volatiles. The operating phases and conditions were customised and optimized. Recovery efficiency was optimized in terms of moisture removal, cold trap temperature and sampling mass flow. The injection of entrapped volatiles was realized through a direct transfer with high chromatographic reliability (capillary column–capillary column). These improvements allowed obtaining limits of detection (LODs) at least one order of magnitude lower than current LODs for the investigated substances. The method was successfully employed on real samples: air from urban and rural areas and air from remote zones such as Antarctica.     

Organic analysis of the headspace of hanford waste tank 241-C-103

Organic species from the headspace of one Hanford radioactive waste tank are described. Samples were collected either using a sorbent trap or a SUMMA^TM canister and were analyzed by gas chromatograph and mass spectrometry. The headspace contained several organic components, including alkanes, alkenes, ketones, aldehydes, organic nitriles, and chlorinated hydrocarbons. Sorbent trap samples were designed to collect only normal paraffin hydrocarbons (NPHs). A comparison of NPH data from sorbent traps and SUMMA^TM cans revealed results of 693 and 1320 mg/m³, NPH respectively. Significant differences were observed in NPH values when samples were collected at different times, or at different locations in the tank. These data suggest either the time of collection, or the position of the sampling device are important variables in the analysis of organic species from Hanford tanks.     

A needle trap device packed with MIL-100(Fe) metal organic frameworks for efficient headspace sampling and analysis of urinary BTEXs

The aim of this study was to develop a new method for the determination of benzene, toluene, ethylbenzene and xylene isomers (BTEXs) in urine samples. In this method, MIL-100(Fe)@Fe₃O₄@SiO₂ metal–organic framework was synthesized, characterized and packed inside a needle trap device (NTD) as a sorbent for headspace extraction of unmetabolized BTEXs from urine samples followed by gas chromatography (GC) analysis. The GC device was equipped with a flame ionization detector (FID). The results showed that the optimal extraction time, extraction temperature and salt content were 60 min, 30°C and 5%, respectively. Also, the optimal desorption time and temperature were determined to be 1 min and 250°C, respectively. The limits of detection and quantification of the analytes of interest were in the ranges 0.0001–0.0005 and 0.0003–0.0014 μg ml⁻¹, respectively. The intra- and inter-day repeatability were <7.6%. The accuracy of the measurements in urine samples was in the range 7.1–11.4%. The results also demonstrated that the proposed NTD offered various advantages such as having high sensitivity and being inexpensive, reusable, user friendly, environmentally friendly and compatible for use with the GC device. Therefore, it can be efficiently used as a MIL–NTD for the extraction and analysis of unmetabolized BTEXs from urine samples.     

Quantitative analysis of the three-dimensional trap stiffness of a dielectrophoretic corral trap

Dielectrophoresis is a robust approach for the manipulation and separation of (bio)particles using microfluidic platforms. We developed a dielectrophoretic corral trap in a microfluidic device that utilizes negative dielectrophoresis to capture single spherical polystyrene particles. Circular-shaped micron-size traps were employed inside the device and the three-dimensional trap stiffness (restoring trapping force from equilibrium trapping location) was analyzed using 4.42 μm particles and 1 MHz of an alternating electric field from 6 V_P-P to 10 V_P-P. The trap stiffness increased exponentially in the x- and y-direction, and linearly in the z-direction. Image analysis of the trapped particle movements revealed that the trap stiffness is increased 608.4, 539.3, and 79.7% by increasing the voltage from 6 V_P-P to 10 V_P-P in the x-, y-, and z-direction, respectively. The trap stiffness calculated from a finite element simulation of the device confirmed the experimental results. This analysis provides important insights to predict the trapping location, strength of the trapping, and optimum geometry for single particle trapping and its applications such as single-molecule analysis and drug discovery.     

Method development for the analysis of polybrominated dibenzo-p-dioxins, dibenzofurans and diphenyl ethers in sediment samples

A column chromatography procedure was developed for the clean-up of solvent-extracted sediment samples for the fractionation of polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs). The procedure included multiple column chromatography steps for clean-up for the separation of PBDEs from PBDD/Fs. The separation of the two chemical groups overcame the mutual interfering problem during the GC-ion trap MS analysis. The method was validated with the analysis of quality control samples. The method accuracy represented with relative error was less than 16% for all targeted PBDEs and PBDD/Fs congeners. Recoveries of the ¹³C-labeled standards ranged from 64% to 117% with relative standard deviation from 7.3% to 15%. Results from the analysis of environmental sediment samples collected in the vicinity of a recycling site for electronic wastes showed high levels of PBDEs (1.5-12 ng/g, dry weight), trace levels of PBDFs (0.025-0.92 ng/g, dry weight) and non-detectable PBDDs.     

CuInS2量子点阻变效应

采用改进的热分解法制备了具有半导体效应的CuInS₂量子点,量子点尺寸均匀、大小为4.2 nm。组装的Au/CuInS₂/FTO阻变存储器件表现出典型的双极性阻变特点,其开态电压为-3.8 V,关态电压为4 V,ON/OFF开关比约为10³。对器件的I-V特性曲线线性拟合发现,器件的阻变机制在高阻态时表现为空间限制电荷（SCLC）传导机制,在低阻态时表现为欧姆传导机制。器件的阻变特性主要是由于电荷被CuInS₂薄膜中的缺陷产生的势阱捕获导致。通过调节陷阱势垒高度引起电荷在陷阱中移动,导致导电通路的产生和断裂,使器件处于高阻态和低阻态。     

Comprehensive analysis by liquid chromatography Q‐Orbitrap mass spectrometry: Fast screening of peptides and organic molecules

The number of substances nominally listed in the prohibited list of the World Anti‐Doping Agency increases each year. Moreover, many of these substances do not have a single analytical target and must be monitored through different metabolites, artifacts, degradation products, or biomarkers. A new analytical method was developed and validated for the simultaneous analysis of peptides and organic molecules using a single sample preparation and LC‐Q‐HRMS detection. The simultaneous analysis of 450 target molecules was performed after cleanup on a mixed‐mode solid‐phase extraction cartridge, combined with untreated urine. The cleanup solvent and reconstitution solvent were the most important parameters for achieving a comprehensive sample preparation approach. A fast chromatographic run based on a multistep gradient was optimized under different flows; the detection of all substances without isomeric coelution was achieved in 11 minutes, and the chromatographic resolution was considered a critical parameter, even in high‐resolution mass spectrometry detection. The mass spectrometer was set to operate by switching between positive and negative ionization mode for FULL‐MS, all‐ion fragmentation, and FULL‐MS/MS². The suitable parameters for the curved linear trap (c‐trap) conditions were determined and found to be the most important factors for the development of the method. Only FULL‐MS/MS² enables the detection of steroids and peptides at concentrations lower than the minimum required performance levels set by World Anti‐Doping Agency (1 ng mL⁻¹). The combination of the maximum injection time of the ions into the c‐trap, multiplexing experiments, and loop count under optimized conditions enabled the method to be applied to over 10 000 samples in only 2 months during the 2016 Rio Summer Olympic and Paralympic Games. The procedure details all aspects, from sample preparation to mass spectrometry detection. FULL‐MS data acquisition is performed in positive and negative ion mode simultaneously and can be applied to untargeted approaches.     

Ultratrace determination of tin by hydride generation in-atomizer trapping atomic absorption spectrometry

A quartz multiatomizer with its inlet arm modified to serve as a trap (trap-and-atomizer device) was employed to trap tin hydride and subsequently to volatilize collected analyte species with atomic absorption spectrometric detection. Generation, atomization and preconcentration conditions were optimized and analytical figures of merit of both on-line atomization as well as preconcentration modes were quantified. Preconcentration efficiency of 95 ± 5% was found. The detection limits reached were 0.029 and 0.14 ng mL⁻¹ Sn, respectively, for 120 s preconcentration period and on-line atomization mode without any preconcentration. The interference extent of other hydride forming elements (As, Se, Sb and Bi) on tin determination was found negligible in both modes of operation. The applicability of the developed preconcentration method was verified by Sn determination in a certified reference material as well as by analysis of real samples.     

Simultaneous screening and confirmation of multiple classes of drug residues in fish by liquid chromatography-ion trap mass spectrometry

LC-ion trap mass spectrometry was used to screen and confirm 38 compounds from a variety of drug classes in four species of fish: trout, salmon, catfish, and tilapia. Samples were extracted with acetonitrile and hexane. The acetonitrile phase was evaporated, redissolved in water and acetonitrile, and analyzed by gradient chromatography on a phenyl column. MS² or MS³ spectra were monitored for each compound. Qualitative method performance was evaluated by the analysis over several days of replicate samples of control fish, fish fortified with a drug mixture at 1 ppm, 0.1 ppm and 0.01 ppm, and fish dosed with a representative from each drug class. Half of the 38 drugs were confirmed at 0.01 ppm, the lowest fortification level. This included all of the quinolones and fluoroquinolones, the macrolides, malachite green, and most of the imidazoles. Florfenicol amine, metronidazole, sulfonamides, tetracyclines, and most of the betalactams were confirmed at 0.1 ppm. Ivermectin and penicillin G were only detectable in the 1 ppm fortified samples. With the exception of amoxicillin, emamectin, metronidazole, and tylosin, residue presence was confirmed in all the dosed fish.     

Determination of polybrominated diphenyl ethers in soil from e-waste recycling site

Soil samples collected from an electronic waste recycling site were prepared by using Soxhlet extraction and multiple-step column chromatographic clean-up. Gas chromatography/ion trap mass spectrometry method was developed to determine polybrominated diphenyl ethers (PBDEs) in the sample extracts. The method performance was evaluated by the recovery of ¹³C-labeled internal standards and by analyzing quality assurance and quality control samples. Relative error and relative standard deviation obtained from the analysis of duplicated samples and spiked matrix were better than 10%. PBDEs were detected in the field soil samples collected from an e-wastes disposal site at levels from low parts-per-billions to 600 parts-per-billions.     

Extraction of formic and acetic acids from aqueous solution by dynamic headspace-needle trap extraction temperature and pH optimization

A combined method of dynamic headspace-needle trap sample preparation and gas chromatography for the determination of formic and acetic acids in aqueous solution was developed in this study. A needle extraction device coupled with a gas aspirating pump was intended to perform sampling and preconcentration of target compounds from aqueous sample before gas chromatographic analysis. The needle trap extraction (NTE) technique allows for the successful sampling of short chain fatty acids under dynamic conditions while keeping the headspace (HS) volume constant. Two important parameters, including extraction temperature and effect of acidification, have been optimized and evaluated using the needle trap device. The method detection limits for the compounds estimated were 87.2microg/L for acetic acid and 234.8microg/L for formic acid in spite of the low flame ionization detection response for formic acid and its low Henry's law constant in aqueous solution. Precision was determined based on the two real samples and ranged between 4.7 and 10.7%. The validated headspace-needle trap extraction method was also successfully applied to several environmental samples.     

A novel needle trap sorbent based on carbon nanotube-sol-gel for microextraction of polycyclic aromatic hydrocarbons from aquatic media

A new type of composite material based on carbon nanotubes (CNTs) and sol–gel chemistry was prepared and used as sorbent for needle trap device (NTD). The synthesized composite was prepared in a way to disperse CNTs molecules in a sol–gel polymeric network. CNT/silica composites with different CNT doping levels were successfully prepared, and the extraction capability of each composite was evaluated. Effects of surfactant and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were also investigated. The applicability of the synthesized sorbent was examined by developing a method based on needle trap extraction (NTE) and gas chromatography mass spectrometry detection (GC–MS) for the determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Important parameters influencing the extraction process were optimized and an extraction time of 30 min at 50 °C and sampling flow rate of 2.5 mL min⁻¹ gave maximum peak area, when NaCl (15%, w/v) was added to the aqueous sample. The linearity for acenaphthene, acenaphthylene and fluorene was in the concentration range of 0.01–20 ng mL⁻¹ and for naphthalene and anthracene was in the range of 0.1–50 ng mL⁻¹. Limits of detection was 0.001 ng mL⁻¹, for acenaphthene, acenaphthylene and fluorene, and 0.01 ng mL⁻¹, for naphthalene and anthracene using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values (n = 3) were all below 11.2% at the 1 ng mL⁻¹ level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 73.8 to 113.8%.     

Gas chromatography analysis of benzene, toluene, ethylbenzene and xylenes using newly designed needle trap device in aqueous samples

A newly designed needle trap device with Carbopack X as a sorbent material is used for sampling, preconcentration and injection of volatile analytes benzene, toluene, ethylbenzene and xylenes (BTEX) into gas chromatograph. The closed system of stripping the analytes from water samples was used. An injection port with a modified metal liner was used to desorb analytes trapped in needle trap device. The main advantage of needle trap device consists in the simple methodology and easiness and rapidity of the analysis. Needle trap device is suitable for sampling in field. The experimental parameters as breakthrough volume of stripping gas, linearity, repeatability and limit of detection (LOD) and quantification (LOQ) were investigated. LOD ranges from 0.05 to 0.07 microgL(-1) and relative standard deviation ranges from 0.5% to 11.6% at concentrations 5 and 0.1 microgL(-1), respectively.     

Comparison of Needle Concentrator with SPME for GC Determination of Benzene, Toluene, Ethylbenzene, and Xylenes in Aqueous Samples

A method of solventless extraction of volatile organic compounds from aqueous samples has been developed and validated. A new arrangement in which the internal volume of a needle capillary adsorption trap is completely filled with Porapak Q, as adsorbent material, and wet alumina, as a source of desorptive water vapor flow, is presented. The device has been used for head-space sampling of benzene, toluene, ethylbenzene, and xylenes (BTEX) from water samples and compared with solid-phase microextraction. Under the same sampling conditions the analytical characteristics of the device for the BTEX compounds are better than those of solid-phase microextraction. Limits of detection and quantification are below 0.5 μ g L⁻¹.     

New Grafted Nanosilica-Based Sorbent for Needle Trap Extraction of Polycyclic Aromatic Hydrocarbons from Water Samples Followed by GC/MS

In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes from aqueous samples, the prepared needle trap device (NTD) was placed in the headspace of the sample and another needle was also inserted into the sample solution to purge the circulating headspace into the sample. For increasing the extraction efficiency, influencing parameters including extraction time and temperature, flow rate of analyte through the needle trap, the ionic strength, desorption temperature, and time were optimized. The limit of detection (LOD) and relative standard deviation (RSD) values of the method under optimized conditions were 2?C5 ng L^?1 and 1.1?C4.8%, respectively. The RSD% for fluorene was somewhat higher and a value of 16.8% at 40 ng L^?1 was achieved. Finally the developed method was applied to the analysis of tap water and Zayandeh-roud river samples and the relative recovery (RR %) values were found to be in the range of 77?C109%, under the optimized conditions.     

MS<Superscript>M</Superscript>, an Efficient Workflow for Metabolite Identification Using Hybrid Linear Ion Trap Orbitrap Mass Spectrometer

Identification of drug metabolites can often yield important information regarding clearance mechanism, pharmacologic activity, or toxicity for drug candidate molecules. Additionally, the identification of metabolites can provide beneficial structure-activity insight to help guide lead optimization efforts towards molecules with optimal metabolic profiles. There are challenges associated with detecting and identifying metabolites in the presence of complex biological matrices, and new LC-MS technologies have been developed to meet these challenges. In this report, we describe the development of an experimental approach that applies unique features of the hybrid linear ion trap Orbitrap mass spectrometer to streamline in vitro and in vivo metabolite identification experiments. The approach, referred to as MS^M, utilizes multiple collision cells, dissociation methods, mass analyzers, and detectors. With multiple scan types and different dissociation modes built into one experimental method, along with flexible post-acquisition analysis options, the MS^M workflow offers an attractive option to fast and reliable identification of metabolites in different kinds of in vitro and in vivo samples. The MS^M workflow was successfully applied to metabolite identification analysis of verapamil in both in vitro rat hepatocyte incubations and in vivo rat bile samples.     

Imaging of small molecules in tissue sections with a new intermediate-pressure MALDI linear ion trap mass spectrometer

We describe a new intermediate-pressure MALDI linear ion trap mass spectrometer and its capabilities for imaging mass spectrometry. The instrument design is described and is characterized in terms of four performance issues (1) MALDI performance at intermediate pressure; (2) analysis of samples on non-conductive and conductive glass slides; (3) critical importance of tandem mass spectrometry (both MS² and MS³) for identification of analyte species and imaging of isobaric species; (4) capability for repeated analysis of the same tissue section. Application of the new instrument to imaging phospholipids in rat brain sections is described in detail.     

Development of a needle trap device packed with titanium‐based metal‐organic framework sorbent for extraction of phenolic derivatives in air

We developed a novel method of needle trap device packed with titanium‐based metal‐organic framework for the extraction of phenolic derivatives in air followed by gas chromatography‐flame ionization detector analysis. The synthetized adsorbent was packed inside a 22‐gauge spinal needle. This method was first tested at laboratory scale, and then was used for field sampling of phenolic derivatives in air. A glass chamber placed on a heater at 60°C was used to provide different concentrations of phenolic derivatives. The desorption conditions and breakthrough volume were optimized using response surface methodology. The limit of detection and limit of quantitation of the proposed method were estimated to be in the range of 0.001–0.12 and 0.003–0.62 ng/mL, respectively, indicating a high sensitivity for the suggested sampler. Storing the packed needle trap device in a refrigerator at 4?C for 60 days did not dramatically affect the storage stability. Our findings indicated that there was a high correlation coefficient (R² = 0.99) between the measurement results of this method and the NIOSH recommended method (XAD‐7 sorbent tube). Therefore, it can be concluded that the needle trap device packed with titanium‐based metal‐organic framework can be used as a efficient method for extraction of phenolic derivatives in air.