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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 in very small residues of beverages, collected at the scene of drug-facilitated crimes 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 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 interday repeatabilities were between 1 and 8%. No matrix effects 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.

An LC-MS method for the analysis of personal care and household products without sample preparation is presented. The method takes advantage of the Direct-electron ionization (EI) LC-MS interface for the quantitation of principal components, as well as for the identification of unknown or undeclared ingredients. The technique has proven its inertness toward matrix effects and the electron ionization allows quantitation and library identification. Commercially available products (shower gel, perfume, and hand cream) were diluted with methanol and injected directly into a nano-LC column. Limonene, linalool, and citral were selected as target compounds because of their use as fragrances in toiletry and detergent products. These and all other fragrances are commonly determined with GC-MS analysis, prior to sample cleanup, a procedure that can lead to analytes loss. The selected compounds are not detected with ESI because of their poor or very low response. Figures of merit and validation studies were executed and special attention was devoted to matrix-effects evaluation, because a sample preparation procedure is not involved. No matrix effects were observed, and the repeatability was excellent even after several weeks of operation. Products composition was investigated in full scan mode to determine the presence of unknown or not listed ingredients.

We investigated the effect of temperature on the packing procedure of nano-LC columns (up to 50 cm) and on their performance. Several slurries of stationary phase were prepared using different solvent mixtures. Their stability was evaluated at several temperatures: 70°C, 50°C, and room temperature. At the higher temperature (70°C) the suspensions resulted to be stable for a longer time. For each slurry, we compared nano-LC columns packed with ultrasounds at 70°C and at room temperature. All the columns were tested with a standard mixture at 70°C, to reduce the solvent viscosity and the backpressure. Main chromatographic parameters such as the asymmetry factor, As, the reduced plate high, h, pattern in a Van Deemter plot, the total porosity, e(t), and the permeability, k, were calculated and discussed. One of the nano-LC columns was used to separate a mixture of pesticides in a LC-MS system with an electron ionization LC-MS interface (Direct-EI). From our knowledge, this is the first study on the role of temperature in the efficiency of slurry-packing procedure.

DiSTeVA, Universita` degli Studi di Urbino ‘‘Carlo Bo,’’Piazza Rinascimento, 6, 61029 Urbino, ItalyReceived 13 July 2010; received (revised) 22 November 2010; accepted 22 November 2010Published online 8 March 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mas.20329This review article will give an up-to-date and exhaustiveoverview on the efficient use of electron ionization (EI) tocouple liquid chromatography and mass spectrometry (LC–MS) with an innovative interface called Direct-EI. EI is basedon thegas-phase ionization of the analytes, and it is suitable formany applications in a wide range of LC-amenable compounds.In addition, thanks to its operating principles, it preventsunwelcome matrix effects (ME). In fact, although atmosphericpressure ionization (API) methodologies have boosted the use ofLC–MS, the related analytical methods are sometime affectedby inaccurate quantitative results, due to unavoidable andunpredictable ME. In addition, API’s soft ionization spectraalways demand for costly and complex tandem mass spectrom-etry (MS/MS) instruments, which are essential to acquire an‘‘information-rich’’ spectrum and to obtain accurate quantita-tive information. In EI a one-stage analyzer is sufficient for aqualitative investigation and MS/MS detection is only used toimprove sensitivity and to cut chemical noise. The technologyillustrated here provides a robust and straightforward accessto classical, well-characterized EI data for a variety ofLC applications, and readily interpretable spectra for a widerange of areas of research. The Direct-EI interface canrepresent the basis for a forthcoming universal LC–MSdetector for small molecules. # 2011 Wiley Periodicals, Inc.,Mass Spec Rev 30:1242–1255, 2011Keywords: LC–MS; nano-HPLC; electron ionization; Direct-EI interface; matrix effects

Matrix-dependent signal suppression or enhancement represents a major drawback in quantitative analysis with liquid chromatography coupled to atmospheric pressure ionization mass spectrometry (LC-API-MS). Because matrix effects (ME) might exert a detrimental impact on important method parameters (limit of detection, limit of quantification, linearity, accuracy, and precision), they have to be tested and evaluated during validation procedure. This review gives a detailed description on when these phenomena might be expected, and how they can be evaluated. The major sources of ME are discussed and illustrated with examples from bioanalytical, pharmaceutical, environmental, and food analysis. Because there is no universal solution for ME, the main strategies to overcome these phenomena are described in detail. Special emphasis is devoted to the sample-preparation procedures as well as to the recent improvements on chromatographic and mass spectrometric conditions. An overview of the main calibration techniques to compensate for ME is also presented. All these solutions can be used alone or in combination to retrieve the performance of the LC-MS for a particular matrix-analyte combination.

A conspicuous fraction of the water soluble organic compounds (WSOC) in fog and fine aerosol samples is composed by monosaccharide anhydrides, such as levoglucosan and its stereoisomers, galactosan and mannosan. Levoglucosan is produced exclusively during wood combustion processes, making it a very useful tracer for plant combustion emissions in the atmosphere. This paper describes a new experimental approach, based on electrospray-tandem mass spectrometry (ESI-MS/MS), for the identification of levoglucosan in fog water samples. The analytical method proposed allows to identify the specific sugar anhydrides directly in the liquid phase without the need of any derivatization process.

Permission to reproduce this table online was not granted by the copyright holder. Readers are kindly asked to refer to the printed version. Two recent approaches for coupling capillary scale liquid chromatography and electron ionization mass spectrometry are reviewed and discussed. The first one, Cap-EI, is the latest evolution of the micro-scale particle beam interface, in which the nebulizer has been optimized to overcome the limitations of the former approach, in terms of sensitivity and linearity. It can be easily hosted in pre-existing instruments without major modifications and can use helium and the less-expensive nitrogen to generate library-matchable electron ionization spectra. The second one is a miniaturized interface for nano- and micro-HPLC, in which the interfacing process takes place into a suitably modified ion source. Because the eluate from the column is completely transferred into the ion source for ionization, superior sensitivity, linearity, and reproducibility are obtained. No signs of chemical ionization are observed at flow rates up to 1.5 μL/min. These two interfaces demonstrate that electron ionization can be successfully used for the analysis of small—medium molecules of various polarities, and also at the trace level. The possibility to record library-matchable electron ionization spectra offers the analyst a powerful tool that can be particularly useful in real-world applications.© 2001 John Wiley & Sons, Inc., Mass Spec Rev 20: 88–104, 2001