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Solid-phase microextraction (SPME) directly coupled to MS is a widespread technique for determining small molecules in different matrices in many application fields. Here we present a modified microfluidic open interface (MOI) connected to a passive-flow-splitter device (PFS) for the direct coupling of SPME to a liquid-electron ionization (LEI) interface in a tandem mass spectrometer for the analysis of complex biological samples. No chromatographic separation is involved. The new MOI-PFS configuration was designed to speed up the sample transfer to MS, improving the signal-to-noise ratio and peak shape and leading to fast and sensitive results. MOI-PFS-LEI-MS/MS experiments were conducted using fentanyl as a model compound in water and blood serum. The method uses a C18 Bio-SPME fiber by direct immersion (3 min) in 300 µL of the sample followed by rapid desorption (1 min) in a flow isolated volume (MOI chamber, 2.5 µL) filled with 100% acetonitrile. The PFS permits the rapid transfer of a fraction of the sample into the MS via the LEI interface. The optimal conditions were obtained at a flow rate of 10 µL·min

This review article traces the history of the use of liquid chromatography coupled with mass spectrometry (LC-MS) using electron ionization (EI) from the first attempts up to the present day. At the time of the first efforts to couple LC to MS, 70 eV EI was the most common ionization technique, typically used in gas chromatography-mass spectrometry (GC-MS) and providing highly reproducible mass spectra that could be collated in libraries. Therefore, it was obvious to transport this dominant approach to the early LC-MS coupling attempts. The use of LC coupled to EI-MS is challenging mainly due to restrictions related to high-vacuum and high-temperature conditions required for the operation of EI and the need to remove the eluent carrying the analyte before entering the ion source. The authors will take readers through a journey of about 50 years, showing how through the succession of different attempts it has been possible to successfully couple LC with EI-MS, which in principle appear to be incompatible.

Mass spectrometry has been the "gold standard" for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography-mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future. © 2020 Periodicals, Inc. Mass Spec Rev.

Liquid Electron Ionization (LEI), is an innovative liquid chromatography-mass spectrometry (LC-MS) interface that converts liquid HPLC eluent to the gas-phase in a mass spectrometer equipped with an electron ionization (EI) source. LEI extends the electronic spectra libraries access to liquid chromatography, providing a powerful tool in the untargeted approacssh. Negligible matrix effects allow accurate quantitative information. The purpose of this research was to evaluate the main aspects concerning the interfacing process. These fundamental studies were necessary to understand the mechanism of LEI in details, and improve the interfacing process, especially regarding robustness and sensitivity. Hardware components were installed to prevent analytes precipitation, reduce thermal decomposition of sensitive compounds, and to stabilize the nano-flow delivery with different mobile-phase compositions. Particular attention was devoted to insulating the heated vaporization area from the LC part of the system. Experiments were performed to optimize the interface inner capillary dimensions, and other operative parameters, including temperature, gas and liquid flow rates. Test compounds of environmental interest were selected based on molecular weight, thermal stability, volatility, and polarity. Robustness was evaluated with a set of replicated injections and calibration experiments using a soil matrix as a test sample. MRM detection limits in the low-picogram range were obtained for five pesticides belonging to different classes in a soil sample. High-quality electron ionization mass spectra of a mixture of pesticides were also obtained.

Buprenorphine and its metabolites are routinely monitored to assess patient compliance with drug detoxification programs or as pain killers. A rapid method for the simultaneous analysis of buprenorphine, norbuprenorphine, and glucuronides in urine using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed. Urine samples were diluted in water containing formic acid 0.1% and directly injected into the UHPLC-MS/MS system without any sample pretreatment. Quality control (QC) samples, prepared using 20 different urine matrices, fortified at 3 concentration levels, were quantified using four deuterated internal standards. The accuracy values obtained spanned from 90 to 114% with repeatability lower than 10% also in the inter-day between batch experiments. Matrix effects (ME), evaluated before correction with internal standards using Matuszewski procedure, mainly affected the analysis of buprenorphine glucuronide. The use of deuterated internal standards (IS) for each analyte was necessary to compensate for ME and was essential in the determination of glucuronides. The method was applied to 30 real urine samples from patients under a detoxification therapy. Duplicate analyses were performed with the presented method and compared with another method which involves a standard hydrolysis procedure. Real sample results were compared showing a good performance agreement, with differences between the two methods lower than ±20% in the quantification results.

Detection of target and non-target substances and their characterization in complex samples is a challenging task. Here we demonstrate that coating the electron ionization (EI) ion source of an LC-MS system with a sol-gel ceramic film can drastically improve the detection of high-molecular weight and high-boiling analytes. A new ion source coated with a ceramic material was developed and tested with a mixture of polycyclic aromatic hydrocarbons (PAH) with an increasing number of rings. Comparison of the results obtained with those for an uncoated stainless steel (SS) ion source shows a dramatic improvement in the MS signals, with a nearly 40-fold increase of the signal-to-noise ratio. We also demonstrate the ability of the new system to produce excellent chromatographic profiles for hard-to-detect hormones.

This is the first application based on electron ionization (EI) using a Direct-EI LC interface and MS/MS to detect unequivocally target compounds in a very small real sample. The determination and quantification of benzodiazepines (BDZ) in very small residues of beverages, collected at the scene of drug-facilitated crimes (DFC) are mandatory in legal procedures. A specific and sensitive analytical instrumentation is needed, involving little or no sample preparation. Here, a direct flow injection analysis (FIA) of alcoholic beverages spiked with commercially available drugs containing diazepam and flunitrazepam is presented. The method proposed is very fast and requires neither sample preparation nor chromatographic separation. Linearity (R(2) ) was between 0.9977 and 0.9992; LOD and LOQ spanned from 0.01 to 0.02 ng/μL and from 0.1 to 0.5 ng/μL, respectively; intra- and inter-day repeatabilities were between 1 and 8%. No matrix effects (ME) were observed from the comparison of the linear regression curves obtained in real fortified samples and in pure ethanol. Vodka, whisky and white wine specimens were fortified with commercial drugs, Valium(®) and Rohypnol(®) , at two different concentrations (20 and 50 ng/μL) to simulate the typical amounts found in adulterated real samples and analyzed to demonstrate the method applicability to forensic analyses. This article is protected by copyright. All rights reserved.

This article describes a nano-scale method for the determination and quantification of five benzodiazepines (BDZ) in an alcoholic grappa drink (chlordiazepoxide; lorazepam; diazepam; oxazepam; medazepam). BDZ are typically used in drug-facilitated crimes (DFC) for their accessibility and synergistic effects with alcohol. Specimens collected on the crime scene must be rapidly analyzed to prove the crime, though, in most cases, a very small amount is available. Off-line MEPS extraction of diluted grappa samples proved to be an efficient and reliable method for the recovery of the selected compounds. Requiring a very small amount of extraction solvents, MEPS is an environment-friendly technique. LC separation with UV detection was used as the analytical technique because it is simple, robust, relatively economic and easy-to-find in most laboratories. The method was validated in terms of precision, accuracy and recovery. Limits of detection and quantitation were in the range of 0.5-2ng/μL. Linearity (R(2)) spanned from 0.9994 and 1.0000. Intra- and inter-day repeatabilities were lower than 12% at any concentration. Recovery percentages of an equivalent-to-real sample at three different concentrations were between 70.7 and 74.1%.

Benzodiazepines (BDZs) are widely used as tranquilizers and anti-depressive drugs in common clinical practice. However, their ready availability and their synergistic effects with alcohol make them attractive for criminal intentions. To prove criminal action for legal reasons, it is often necessary to analyze beverage residues from a crime scene. Milk-based alcoholic drinks (whiskey creams) are gaining popularity due to their lower alcohol content pleasant taste. However, the complexity of this sample, containing proteins and fatty acids, can mask the presence of drugs or other substances in standard analysis methods. These characteristics make whiskey creams highly suitable for illicit purposes. In this study, eight BDZs, including diazepam, chlordiazepoxide, clobazam, flunitrazepam, bromazepam, flurazepam, nitrazepam and clonazepam, were extracted from whiskey cream using the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method and analyzed using GC-MS. The QuEChERS protocol can efficiently separate most of the matrix from the target compounds while maintaining acceptable recoveries. The presented method is simple and rapid and has been validated in terms of precision, accuracy and recoveries. Limits of detection and limits of quantitation were in the range of 0.02-0.1 and 0.1-0.5 µg/mL, respectively. Whiskey cream beverages, fortified with commercial drugs at 20 µg/mL, were extracted and analyzed demonstrating the applicability of the method in forensic analysis.

The purpose of this article is to underline the possibility of efficiently using electron ionization (EI) in liquid chromatography (LC) and mass spectrometry (MS). From a historical perspective, EI accompanied the first attempts in LC-MS but, owing to several technical shortcomings, it was soon outshined by soft, atmospheric pressure ionization (API) techniques. Nowadays, two modern approaches, supersonic molecular beam LC-MS and direct-EI LC-MS, offer a valid alterative to API, and preserve the advantages of EI also in LC-MS applications. These advantages can be summarized in three crucial aspects: automated library identification; identification of unknown compounds, owing to EI extensive fragment information; inertness to coeluted matrix interferences owing to very unlikely ion–ion and ion–molecule interactions in the EI gas-phase environment. The direct-EI LC-MS interface is a simple and efficient solution able to produce high-quality, interpretable EI spectra from a wide range of low molecular weight molecules of different polarity. Because of the low operative flow rates, this interface relies on a nano-LC technology that helps in reducing the impact of the mobile phase on the gas-phase environment of EI. This review provides an extensive discussion on the role of EI in LC-MS interfacing, and presents in detail several performance aspects of the direct-EI LC-MS interface, especially in terms of response, mass-spectral quality, and matrix effects. In addition, several key applications are also reported.

Produced formation waters (PFWs) represent the largest aqueous wastes that are normally discharged into the marine environment during the offshore gas production processes. The chemical additive diethylene glycol (DEG) is widely used in the gas production line and therefore can be found in the PFW, becoming of environmental concern. In this study, a new method has been developed for trace determination of DEG in sea water samples collected around offshore gas platforms. The method is based on liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS). Prior to analysis, water samples were derivatized using the Schotten-Baumann method for the benzoylation of glycols. The derivatization procedure allowed us to maximize the ESI-MS response of DEG and minimize the influence of interfering compounds. The method was validated and allowed a quantification of DEG in sea water samples with a method LOD of 0.4 ng/mL. The applicability of the procedure was demonstrated by analyzing sea water samples collected around eight gas platforms located in the Adriatic Sea (Italy).

Water pollution by organochlorine pesticides (OCPs) is considered as an analytical challenge, since these persistent and nonbiodegradable pollutants are not amenable by liquid chromatography coupled to atmospheric pressure ionization mass spectrometry (LC/API-MS). This represents a significant constraint in multiresidue analysis of real samples, when high polar, poorly volatile compounds are present as well. This paper reports the development of an innovative single-step method for the simultaneous determination of OCPs and polar pesticides belonging to the class of phenoxy acids in water samples. The method is based on an off-line solid-phase extraction (SPE) procedure with Carbograph 4 followed by liquid chromatography coupled to a direct electron ionization mass spectrometer (LC/direct-EI-MS). The direct-EI capability of acquiring high-quality EI spectra and operation in selected ion monitoring mode allowed a precise quantification of OCPs and phenoxy acids in a single chromatographic run without derivatization. The instrumental response was characterized by excellent sensitivity, linearity, and precision. The SPE recovery rates in river water gave values equal or better than 80% for most of the compounds. The method limits of detection (LODs) span from 0.002 to 0.052 microg/L, allowing the detection of the selected pesticides at the limits required by the European Union (EU) legislation for drinking water.

Contamination of water resources by organochlorine pesticides (OCPs) continues to receive widespread attention because of the increasing concern regarding their high persistence and bioaccumulation. These organic pollutants are not amenable by liquid chromatography (LC) coupled to atmospheric pressure ionization-mass spectrometry, which represents the method of choice for the characterization of pesticide residues in water. Gas chromatography-mass spectrometry provides excellent response for OCPs, but it falls short when complex, multiresidue analyses are required. As recently demonstrated, an efficient EI-based LC-MS interface can generate very good spectra for an extremely wide range of small-medium molecular weight molecules of different polarity and can represent a valid tool in solving the analytical challenge of analyzing OCPs by LC-MS. Based on this assumption, we present a new approach for the determination of 12 OCPs in water samples. The method requires a solid-phase extraction preconcentration step followed by nanoscale liquid chromatography coupled to a direct-electron ionization direct interface (Direct-EI). Direct-EI is a miniaturized interface for efficiently coupling a liquid chromatograph with an EI mass spectrometer. The capability to acquire high-quality EI spectra in a wide range of concentrations, and to operate in selected ion monitoring mode during analyses, allowed a precise quantification of the OCPs. Without sample injection enrichment, limits of detection of the method span from 0.044 to 0.33 microg/L, corresponding to an instrumental detection limit of 120-850 pg. In addition, a careful evaluation of the matrix effect showed that the response of the Direct-EI interface was never affected by sample interferences. From our knowledge, the proposed method represents the first application of LC-MS in the analysis of organochlorine pesticides.

Major progress in interfacing liquid chromatography and electron ionization mass spectrometry is presented. The minimalism of the first prototype, called the Direct-EI interface, has been widely refined, improved, and applied to modern instrumentation. The simple interfacing principle is based on the straight connection between a nanoHPLC system and a mass spectrometer equipped with an EI source forming a solid and reliable unicum resembling the immediacy and straightforwardness of GC/MS. The interface shows a superior performance in the analysis of small-medium molecular weight compounds, especially when compared to its predecessors, and a unique trait that excels particularly in the following aspects: (1) It delivers high-quality, fully library matchable mass spectra of most sub-1 kDa molecules amenable by HPLC. (2) It is a chemical ionization free interface (unless operated intentionally) with accurate reproduction of the expected isotope ion abundances. (3) Response is never influenced by matrix components in the sample or in the mobile phase (nonvolatile salts are also well accepted). A deep evaluation of these aspects is presented and discussed in detail. Other characteristics of the interface performance such as limits of detections, range of linear response, and intra- and interday signal stability were also considered. The usefulness of the interface has been tested in a few real-world applications where matrix components played a detrimental role with other LC/MS techniques.

A comprehensive evaluation and a thorough discussion of the fields of possible applications of the Direct-EI interface are described in this review. Direct-EI allows the direct introduction of the effluent from a capillary HPLC column into the electron ionization (EI) ion source of a mass spectrometer. Thanks to the reduced liquid intake and an in-source nebulizer, the interfacing process occurs smoothly and entirely into the ion source. No intermediate interfacing mechanisms of any sort are interposed between the column and the mass spectrometer, thus circumventing any undesired sample loss and minimizing the effort for instrument modification. Theoretically, any GC-MS system can be converted into an LC-MS for EI amenable compounds. Several parameters, crucial for a successful integration of liquid chromatography and mass spectrometry, have been considered in the evaluation of the functioning of such an interface: limit of detection, linearity of response, reproducibility, and chromatographic compatibility. Different mobile phases, also containing non-volatile buffers, were taken into account, demonstrating an outstanding separation flexibility. The entire set of experiments was carried out at different flow rates and temperatures of the ion source. The interface behavior was also tested in real world applications, with mixtures of pesticides, hormones, nitro-PAH, and endocrine-disrupting compounds, allowing picogram level detection and the possibility to record library-matchable, readily interpretable electron ionization mass spectra, for prompt compound characterization and confirmation. © 2005 Wiley Periodicals, Inc., Mass Spec Rev 24:978–989, 2005

A new LC/MS method for the determination of organophosphorus pesticides in water, based on the use of direct-electron ionization (EI) interface, is presented. Direct-EI is a new device that, in a very simple fashion, couples a nano-HPLC system with a mass spectrometer equipped with electron ionization capability. The nanoscale liquid flow allows for a direct introduction of eluate into the ion source and, after nebulization, for its ionization under typical EI conditions. Library-matchable EI spectra are generated for a choice of full scan or SIM detection of the analytes. In our case, a selection of organophosphorus pesticides, commonly distributed in local sugar beet cultivation, were considered. The new interface permits a very sensitive detection of the analytes in a wide range of linear response (0.09-9 ng). When applied to a real sample, the method allowed detecting four different pesticides at a concentration level of approximately 3 ng x L(-1).

The use of a new LC-MS interface (cap-EI), part of a Waters Integrity system, capable of generating EI spectra at micro flow rates is presented. The cap-EI interface relies on the production of a fine aerosol by means of a nebulizer and supported by a nitrogen jet. Sensitivity, response linearity, reproducibility, and LC compatibility of the interface were thoroughly examined using testosterone, caffeine, a mixture of antiinflammatory drugs, and 3,4-dihydroxybenzoic acid as test compounds. The interface is fully compatible with LC requirements such as high-water- and/or -buffer-content mobile phases. Reproducibility, high sensitivity in scan mode, as well, to produce library-searchable EI spectra, 2 orders of magnitude linearity, together with an intrinsic simplicity of the entire system are the key features of cap-EI interface.

A comparison of the official EPA method 515.1 for determination of chlorinated acidic pesticides and a modification of it is illustrated. Extraction of the analytes from water and their determination and quantitation is by gas chromatography-electron capture detection (GC-ECD), liquid chromatography-UV detection and liquid chromatography-particle beam mass spectrometry. Although HPLC-PBMS was found to be less sensitive than the GC-ECD method, it was, nevertheless, more sensitive than HPLC-UV. The modified method is simpler, quicker and allows more accurate determination of pesticides in aqueous samples.

Plastic tubing of polyetheretherketone (PEEK) is used for the preparation of HPLC packed capillary columns. The polymer is rigid but not fragile, has great resistance to chemical and physical agents and comes in standard 1/16″ O.D. These features can extend the column lifetime and facilitate the overall employment of HPLC capillary columns. Serial connection of short columns is also possible with no increase in dead volume. A new, rapid and effective packing method has been developed to be compatible with the characteristics of the material. Several C8 and C18 columns have been prepared and tested and some applications are shown.

A miniaturized, aerosol based interface for directly coupling a liquid chromatograph with a mass spectrometer is presented. The interface is entirely within the electron ionization (EI) source of the mass spectrometer and no additional, external devices are needed. This simple and effective approach exploits micro-flow nebulization technology providing a new interface suitable for a variety of applications of environmental and biological interest. The new interface provides necessary linearity, ruggedness, sensitivity, and reproducibility of response for trace level analysis, and readily interpretable mass spectra for unambiguous identification of unknown compounds of small to medium molecular weight.

The use of graphitized carbon black (GCB) cartridges for the extraction of organic pollutants (pesticides, phthalates, herbicides and polynuclear aromatic hydrocarbons) from water is discussed. Recovery tests carried out by spiking either the adsorbent or the water showed that nearly 100% recoveries can be obtained in most instances with 1 ml of a suitable eluent using 50 mg of GCB (Carbopack B). Examples of analyses of actual samples by gas chromatography—mass spectrometry are also shown. Levesl as low as 10 ppt can be determined.

Thermodynamic data, such as the enthapy, entropy and free energy of sorption, were determined by adsorption gas chromatography on graphitized carbon blacks for C 3 C 6 n -alkanes and benzene. The data are compared with those available in the literature obtained by either gas chromatography or static methods. The adsorptive properties of graphitized carbon blacks were also evaluted by considering the changes in the isosteric heat of adsorption when a non-polar stationary phase (squalene) was added to the adsorbent.