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Electron ionization (EI) mass spectra of 46 compounds from several different compound classes were measured. Their molecular ion abundances were compared as obtained with 70-eV EI, with low eV EI (such as 14 eV), and with EI mass spectra of vibrationally cold molecules in supersonic molecular beams (Cold EI). We further compared these mass spectra in their National Institute of Standards and Technology (NIST) library identification probabilities. We found that 1. Low eV EI is not a soft ionization method, and it has little or no influence on the molecular ion relative abundances for large molecules and those with weak or no molecular ions. 2. Low eV EI for compounds with abundant or dominant molecular ions in their 70 eV mass spectra results in the reduction of low mass fragment ions abundances thereby reducing their NIST library identification probabilities thus rarely justifies its use in real-world applications. 3. Cold EI significantly enhances the relative abundance of the molecular ions particularly for large compounds; yet, it retains the low mass fragment ions; hence, Cold EI mass spectra can be effectively identified by the NIST library. 4. Different standard EI ion sources provide different 70 eV EI mass spectra. Among the Agilent technologies ion sources, the "Extractor" exhibits relatively abundant molecular ions compared with the "Inert" ion source, while the "High efficiency source" (HES) provides mass spectra with depleted molecular ions compared with the "Inert" ion source or NIST library mass spectra. These conclusions are demonstrated and supported by experimental data in nine figures and two tables. [ABSTRACT FROM AUTHOR]

Pharmaceuticals require careful and precise determination of their impurities that might harm the user upon consumption. Although today, the most common technique for impurities identification is liquid chromatography-mass spectrometry (LC-MS/MS), it has several downsides due to the nature of the ionization method. Also, the analyses in many cases are targeted thus despite being present, some of the compounds will not be revealed. In this paper, we propose and show a new method for untargeted analysis and identification of impurities in active pharmaceutical ingredients (APIs). The instrument used for these analyses is a novel electron ionization (EI) LC-MS with supersonic molecular beams (SMB). The EI-LC-MS-SMB was implemented for analyses of several drug samples spiked with an impurity. The instrument provides EI mass spectra with enhanced molecular ions, named Cold EI, which increases the identification probabilities when the compound is identified with the aid of an EI library like National Institute of Standards and Technology (NIST). We analyzed ibuprofen and its impurities, and both the API and the expected impurity were identified with names and structures by the NIST library. Moreover, other unexpected impurities were found and identified proving the ability of the EI-LC-MS-SMB system for truly untargeted analysis. The results show a broad dynamic range of four orders of magnitude at the same run with a signal-to-noise ratio of over 10 000 for the API and almost uniform response. [ABSTRACT FROM AUTHOR]

The heavy petroleum fractions produced during refining processes need to be upgraded to useable products to increase their value. Hydrogenated heavy paraffinic fractions can be oxidised to produce high value products that contain a variety of oxygenates. These heavy oxygenated paraffinic fractions need to be characterised to enable the control of oxidation processes and to understand product properties. The accurate identification of the oxygenates present in these fractions by electron ionisation (EI) mass spectrometry is challenging due to the complexity of these heavy fractions. Adding to this challenge is the limited applicability of EI mass spectral libraries due to the absence of molecular ions from the EI mass spectra of many oxygenates. The separation of oxygenates from the complex hydrocarbon matrix prior to high temperature GC-MS (HT-GC-MS) analysis reduces the complexity of these fractions and assists in the accurate identification of these oxygenates. Solid phase extraction (SPE) and supercritical fluid chromatography (SFC) were employed as prefractionation techniques. GC-MS with supersonic molecular beams (SMBs) (also named GC-MS with cold-EI) utilises a SMB interface with which EI is done with vibrationally cold sample compounds in a fly-through ion source (cold-EI) resulting in a substantial increase in the molecular ion signal intensity in the mass spectrum. This greatly enhances the accurate identification of the oxygenates in these fractions. This study investigated the ionisation behaviour of oxygenated compounds using cold-EI. The prefractionation by SPE and SFC and the subsequent analysis with GCMS with cold-EI were applied to an oxygenated heavy paraffinic fraction. [ABSTRACT FROM AUTHOR]

We explored the use of pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GCxGC) mass spectrometry with supersonic molecular beams (SMB) (also named Cold electron ionization (EI)) for achieving universal pesticide analysis in agricultural products. The use of GCxGC serves as an alternative to MS-MS in the needed reduction of matrix interference while enabling full-scan MS operation for universal pesticide analysis with reduced number of false negatives. Matrix interference is further reduced with Cold EI in view of the enhancement of the molecular ions. Pulsed flow modulation is a simple GCxGC modulator that does not consume cryogenic gases while providing tuneable second GCxGC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. PFM-GCxGC-MS with Cold EI combines improved separation of GCxGC with Cold EI benefits of tailing-free ultra-fast ion source response time and enhanced molecular ions for the provision of increased sample identification information and reduced matrix interference. Consequently, PFM GCxGC-MS with Cold EI also improved NIST library identification probabilities of the spiked pesticides. PFM GCxGC is further characterized by largely increased second column sample and matrix capacity that as a result performs much better than thermal modulation GCxGC-MS with standard EI in the suppression of matrix interference. In a comparison with standard GC-MS, we measured with PFM GCxGC-MS with Cold EI an average total ion count matrix interference reduction factor of 32 for 12 pesticides in two matrices of baby leaves mixture and lettuce. In addition, Cold EI further increases the range of pesticides amenable for GC-MS analysis and its response is relatively uniform hence with it the need for pesticides specific calibration is reduced.Pulsed flow modulation GCxGC-MS with Cold EI significantly reduces matrix interference and improves sample identification. [ABSTRACT FROM AUTHOR]

Rationale Library-based compound identification with electron ionization (EI) mass spectrometry (MS) is a well-established identification method which provides the names and structures of sample compounds up to the isomer level. The library (such as NIST) search algorithm compares different EI mass spectra in the library's database with the measured EI mass spectrum, assigning each of them a similarity score called 'Match' and an overall identification probability. Cold EI, electron ionization of vibrationally cold molecules in supersonic molecular beams, provides mass spectra with all the standard EI fragment ions combined with enhanced Molecular Ions and high-mass fragments. As a result, Cold EI mass spectra differ from those provided by standard EI and tend to yield lower matching scores. However, in most cases, library identification actually improves with Cold EI, as library identification probabilities for the correct library mass spectra increase, despite the lower matching factors. Methods This research examined the way that enhanced molecular ion abundances affect library identification probability and the way that Cold EI mass spectra, which include enhanced molecular ions and high-mass fragment ions, typically improve library identification results. It involved several computer simulations, which incrementally modified the relative abundances of the various ions and analyzed the resulting mass spectra. Results The simulation results support previous measurements, showing that while enhanced molecular ion and high-mass fragment ions lower the matching factor of the correct library compound, the matching factors of the incorrect library candidates are lowered even more, resulting in a rise in the identification probability for the correct compound. Conclusions This behavior which was previously observed by analyzing Cold EI mass spectra can be explained by the fact that high-mass ions, and especially the molecular ion, characterize a compound more than low-mass ions and therefore carries more weight in library search identification algorithms. These ions are uniquely abundant in Cold EI, which therefore enables enhanced compound characterization along with improved NIST library based identification. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Rationale Cold EI is defined as electron ionization of cold molecules in supersonic molecular beams (SMB). Gas chromatography/mass spectrometry (GC/MS) with Cold EI provides informative mass spectra, which combine the usual library-searchable EI fragment ions with enhanced molecular ions for improved library-based identification probabilities. However, in some cases, such as in the analysis of complex petrochemical matrices, a soft ionization method that provides only molecular ions is desirable. Methods GC/MS with Cold EI was used with a fly-through ion source at selected electron energies, including at low electron energies, in an attempt to observe molecular ions alone. Results We explored low electron energy Cold EI and found that once the sample compound is cooled by the supersonic expansion it can be reheated via reflected scattered helium atoms near the skimmer. Furthermore, once a labile molecular ion is formed it can undergo undesirable collision-induced dissociation (CID) in the same way as in tandem mass spectrometry (MS/MS), and the magnitude of such CID can be significant for labile molecular ions such as those of hydrocarbons. In order to reduce these adverse effects we reduced the helium pressure at the ion source and MS vacuum chamber by increasing the nozzle-skimmer distance. Cold EI at low electron energies was explored with a squalane isomer (C30H62) and with n-C24H50. Conclusions It was found that an increased nozzle-skimmer distance resulted in a noticeable increase in the abundance ratio of molecular ions to low mass fragment ions. Consequently, Cold EI at low electron energies and a large nozzle-skimmer distance converts EI into Soft Cold EI while further approaching the ideal of a molecular ion only ionization method. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Several novel synthetic organic compounds were successfully analyzed with a unique type of GC–MS titled Supersonic GC–MS following a failure in their analysis with standard GC–MS. Supersonic GC–MS is based on interfacing GC and MS with a supersonic molecular beam (SMB) and on electron ionization of sample compounds as vibrationally cold molecules while in the SMB, or by cluster chemical ionization. The analyses of novel synthetic organic compounds significantly benefited from the extended range of compounds amenable to analyses with the Supersonic GC–MS. The Supersonic GC–MS enabled the analysis of thermally labile compounds that usually degrade in the GC injector, column and/or ion source. Due to the high carrier gas flow rate at the injector liner and column these compounds eluted without degradation at significantly lower elution temperatures and the use of fly-through EI ion source eliminated any sample degradation at the ion source. The cold EI feature of providing trustworthy enhanced molecular ion (M+), complemented by its optional further confirmation with cluster CI was highly valued by the synthetic organic chemists that were served by the Supersonic GC–MS. Furthermore, the provision of extended mass spectral structural, isomer and isotope information combined with short (a few minutes) GC–MS analysis times also proved beneficial for the analysis of unknown synthetic organic compounds. As a result, the synthetic organic chemists were provided with both qualitative and quantitative data on the composition of their synthetic mixture, and could better follow the path of their synthetic chemistry. Ten cases of such analyses are demonstrated in figures and discussed. [Copyright &y& Elsevier]

Open Probe is based on a vaporization oven mounted on a transfer line of a gas chromatograph mass spedrometer (GC/MS) which is connected to the MS ion source via a short flow resthction capillary. The probe oven is open to room air while having helium purge flow protection to eliminate or significantly reduce air leakage into the oven and MS ion source. Sample analysis can be as simple as touch (the sample), push (the sample holder) into the open probe oven, and have the results. Experiments were performed with a GC/MS with supersonic molecular beams and with a standard Agilent 5975 MSD. Powders and tablets analysis were performed by touching the sample with the bottom side of a melting point vial and inserting it into the open probe oven with total analysis cycle lime of <30 s. Similarly, trace trinitrotoluene (TNT) on human fingerprints was analyzed. Additional sample holder types included swabs, spoons, and vials. The open probe is a leak-proof MS probe which is characterized by fast analysis cycle time, and it uses a low cost mass spectrometer of GC/MS with the benefits of electron ionization of library search and uniform, quantitative response without ion suppression effects. [ABSTRACT FROM AUTHOR]

Abstract: A quantitative answer cannot exist in analysis without a qualitative component to give enough confidence that the result meets the analytical needs (i.e. the result relates to the analyte and not something else). Just as a quantitative method must typically undergo an empirical validation process to demonstrate that it is fit for purpose, qualitative methods should also empirically demonstrate that they are suitable to meet the analytical needs. However, thorough qualitative method validation requires analysis of a great number of samples (possibly more than can be reasonably done), which is generally avoided due to the time and the effort involved. Instead, mass spectrometry (MS) is generally assumed to be the gold standard for qualitative methods, and its results are typically unquestioned. For example, a system was developed by European regulators of veterinary drug residues in food animals (2002/657/EC), in which the number of identification points given in MS analyses depends on the general degree of selectivity of the MS technique used. This well-defined approach gives a definite answer for decision-makers, so it has grown in popularity. However, the identification-points system is not scientific. The reality is that each situation requires information gathering and careful deductive thinking on the part of the analyst to make MS identifications. Rather than devise arbitrary requirements that need to be met by an unthinking analyst, we remind the analytical community that confirmation can be given only if two or more independent analyses are in agreement, preferably using orthogonally selective (independent) chemical mechanisms. In this article, we discuss the proper use of terminology, highlight the identification power of various MS techniques, demonstrate how MS identifications can fail if precautions are not taken, and re-assert the value of basic confirmation practices, qualitative method validation, information checklists, routine quality-control procedures, and blind proficiency-test analyses. [Copyright &y& Elsevier]

Abstract: Pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GC×GC) was combined with quadrupole-based mass spectrometry (MS) via a supersonic molecular beam (SMB) interface using a triple-quadrupole system as the base platform, which enabled tandem mass spectrometry (MS-MS). PFM is a simple GC×GC modulator that does not consume cryogenic gases while providing tunable second GC×GC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. The 20-ml/min second column flow rate involved with PFM is handled, splitless, by the SMB interface without affecting the sensitivity. The combinations of PFM GC×GC–MS with SMB and PFM GC×GC–MS-MS with SMB were explored with the analysis of diazinon and permethrin in coriander. PFM GC×GC–MS with SMB is characterized by enhanced molecular ion and tailing-free fast ion source response time. It enables universal pesticide analysis with full scan and data analysis with reconstructed single ion monitoring on the enhanced molecular ion and another prominent high mass fragment ion. The elimination of the third fragment ion used in standard three ions method results in significantly reduced matrix interference. GC×GC–MS with SMB improves the GC separation, and thereby our ability for sample identification using libraries. GC–MS-MS with SMB provides better reduction (elimination) of matrix interference than GC×GC–MS. However, it is a target method, which is not always applicable. GC×GC–MS-MS does not seem to further reduce matrix interferences over GC–MS-MS and unlike GC×GC–MS, it is incompatible with library identification, but it is beneficial to have both GC×GC and MS-MS capabilities in the same system. [Copyright &y& Elsevier]

Gas chromatography–mass spectrometry (GC–MS) suffers from a major limitation in that an expanding number of thermally labile or low volatility compounds of interest are not amenable for analysis. We found that the elution temperatures of compounds from GC can be significantly lowered by reducing the column length, increasing the carrier gas flow rate, reducing the capillary column film thickness and lowering the temperature programming rate. Pyrene is eluted at 287 °C in standard GC–MS with a 30 m×0.25 mm I.D. column with 1-μm DB5ms film and 1-ml/min He column flow rate. In contrast, pyrene is eluted at 79 °C in our “Supersonic GC–MS” system using a 1 m×0.25 mm I.D. column with 0.1-μm DB5ms film and 100-ml/min He column flow rate. A simple model has been invoked to explain the significantly (up to 208 °C) lower elution temperatures observed. According to this model, every halving of the temperature programming rate, or number of separation plates (either through increased flow rate or due to reduced column length), results in ∼20 °C lower elution temperature. These considerably lower elution temperatures enable the analysis of an extended range of thermally labile and low volatility compounds, that otherwise could not be analyzed by standard GC–MS. We demonstrate the analysis of large polycyclic aromatic hydrocarbons (PAHs) such as decacyclene with ten fused rings, well above the current GC limit of PAHs with six rings. Even a metalloporphirin such as magnesiumoctaethylporphin was easily analyzed with elution temperatures below 300 °C. Furthermore, a range of thermally labile compounds were analyzed including carbamates such as methomyl, aldicarb, aldicarbsulfone and oxamyl, explosives such as pentaerythritol tetranitrate, Tetryl and HMX, and drugs such as reserpine (608 a.m.u.). Supersonic GC–MS was used, based on the coupling of a supersonic molecular beam (SMB) inlet and ion sources with a bench-top Agilent 6890 GC plus 5972 MSD. The Supersonic GC–MS provides enhanced molecular ion without any ion source related peak tailing. Thus, the lower GC separation power involved in the analysis of thermally labile and low volatility compounds is compensated by increased separation power of the MS gained from the enhanced molecular ion. Several implications of these findings are discussed, including our conclusion that slower chromatography leads to better analysis of thermally labile compounds. [Copyright &y& Elsevier]

• We report the novel and useful LTM-LPGC-MS technique for the first time. • A new working instrument for real-world application was developed. • LTM-LPGC-MS concepts, features, and trade-offs are described and evaluated. • Example applications with <1 min analysis cycle times are demonstrated. • Comparison of LTM-LPGC-MS is made with conventional fast GC-MS. Conventional gas chromatography - mass spectrometry (GC-MS) takes 20–40 min per sample, which is undesirably slow in any application if speed can be increased while still meeting analytical needs. In this study, we achieved reasonably good separations with full analysis cycle times of less than 1 min by combining for the first time low-pressure (LP) GC-MS with low thermal mass (LTM) resistive-heating for rapid temperature ramping and cooling of the capillary column. The analytical column is threaded into the LTM thin-walled metal tubing in an instrumental device known as "LTM Fast GC" that is mounted at the top of the gas chromatograph in a detector port. The column inlet and outlet are connected to the GC injector and MS transfer line as usual. For LPGC-MS, a 40 cm, 0.1 mm. i.d. uncoated flow restrictor capillary connected at the injector is coupled with a 2.6 m, 0.25 mm i.d., 0.25 µm film thickness analytical column leading to the MS. Thus, the inlet operates at normal GC pressures, but the analytical column is under vacuum, which increases the optimal helium carrier gas flow velocity thereby increasing speed of full range separations while maintaining acceptable quality of chromatography. This column configuration in LTM-LPGC-MS trades a 64-fold gain in speed of analysis vs. standard GC-MS for a 4-fold loss in chromatographic peak capacity, thereby converting analysis time from minutes into seconds in common applications. For example, jet fuel containing fatty acid methyl esters (akin to biofuel) was separated in 25 s with <1 min full analysis cycle time. An EPA Method 8270 mixture of 76 analytes was also analyzed in <1 min full cycle time by LTM-LPGC-MS. Other examples include very fast analysis of heroin in a street drug powder and elucidation of a new organic synthetic compound. In this report, we describe and discuss the several advantageous and practical features of LTM-LPGC-MS, as well as its trade-offs. [ABSTRACT FROM AUTHOR]

Abstract: Gas chromatography–mass spectrometry (GC–MS) instrument limit of detection (LOD) is typically listed by major vendors as that of octafluoronaphthalene (OFN). Most current GC–MS instruments can achieve LODs in the low femtogram range. However, GC–MS LODs for realistic analytes in actual samples are often a few orders of magnitude higher than OFN''s. Users seldom encounter 1pg LOD in the single ion monitoring mode in their applications. We define this detectability difference as the “OFN gap.” In this paper, we demonstrate and discuss how the OFN gap can be significantly reduced by the use of GC–MS with supersonic molecular beams (SMB). Experimental results were obtained with a recently developed GC–MS with SMB named 1200-SMB, that is based on the conversion of the Varian 1200 system into a GC–MS–MS with SMB. With this 1200-SMB system, the LOD of all types of analytes, including OFN, in real samples is significantly improved through the combination of: (a) enhanced molecular ion; (b) elimination of vacuum background noise; (c) elimination of mass independent noise; (d) elimination of ion source peak tailing and degradation; (e) significantly increased range of thermally labile and low volatility compounds that are amenable for analysis through lower sample elution temperatures; (f) reduced column bleed and ghost peaks through sample elution at lower temperatures; (g) improved compatibility with large volume injections; and (h) reduced matrix interferences through the combination of enhanced molecular ion and MS–MS. As a result, the 1200-SMB LODs of common and/or difficult compounds are much closer to its OFN LOD, even in complex matrices. We crossed the <1fg OFN LOD milestone to achieve the lowest LOD to date using GC–MS, but more importantly, we attained LOD of 2fg for diazinon, a common pesticide analyte. In another example, we achieved an LOD of 10fg for underivatized testosterone, which is not amenable in traditional GC–MS analysis, and conducted many analyses of naturally incurred testosterone in alligator blood extracts. In comparison with standard GC–MS, we measured detectability enhancement factors of 24 for dimethoate, 30 for methylstearate, 50 for cholesterol, 50 for permethrin, >400 for methomyl, and >2000 for C32H66. In general, the harder the compound analysis, the greater is the gain in sample detectability using the 1200-SMB versus traditional GC–MS. Thus, the 1200-SMB lowers LOD, particularly for difficult analytes that are normally sacrificed in methods, and the detectability gains can amount to a few orders of magnitude over traditional GC–MS in real-world applications. [Copyright &y& Elsevier]

Abstract: A new approach of flow modulation comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS) with supersonic molecular beam (SMB) and a quadrupole mass analyzer is presented. Flow modulation uniquely enables GC×GC–MS to be achieved even with the limited scan speed of quadrupole MS, and its 20ml/min column flow rate is handled, splitless, by the SMB interface. Flow modulation GC×GC–SMB–MS shares all the major benefits of GC×GC and combines them with GC–MS including: (a) increased GC separation capability; (b) improved sensitivity via narrower GC peaks; (c) improved sensitivity through reduced matrix interference and chemical noise; (d) polarity and functional group sample information via the order of elution from the second polar column. In addition, GC×GC–SMB–MS is uniquely characterized by the features of GC–MS with SMB of enhanced and trustworthy molecular ion plus isotope abundance analysis (IAA) for improved sample identification and fast fly-through ion source response time. The combination of flow modulation GC×GC with GC–MS with SMB (supersonic GC–MS) was explored with complex matrices such as diesel fuel analysis and pesticide analysis in agricultural products. [Copyright &y& Elsevier]

Abstract: We have combined the benefits of supersonic molecular beam interface and its related fly-through electron ionization (EI) ion source with the advanced features of the Varian 1200L gas chromatography–mass spectrometry (GC–MS) and mass spectrometry–mass spectrometry (MS–MS), resulting in a new and powerful GC–MS platform with record setting performance. Electron ionization of vibrationally cold molecules in the supersonic molecular beams (SMB) (cold EI) provided mass spectra with enhanced molecular ion, yet with good library search results and superior identification probabilities. We found that high GC column flow rates lower the elution temperature for any given compounds. This allows much larger molecules to elute at the maximum temperature of standard columns. We analyzed a mixture of heavy linear chain hydrocarbons all the way to C84H170 with a molecular weight of 1179.3amu, using a 4m 0.25mm i.d. column and 32ml/min He flow rate. Furthermore, we obtained a dominant molecular ion to all these compounds. The lower elution temperatures also greatly enhance the ability to analyze very thermally labile compounds such as carbamate pesticides. The experimental 1200 system is capable of triple quadrupole based MS–MS. We found that MS–MS on the molecular ion is much more effective than on fragment ions, and thus, the enhancement of the molecular ion directly improves the MS–MS sensitivity. Fast GC–MS analysis was also explored, based on very high column flow rate for fast splitless injections without affecting the sensitivity, and on the high system selectivity due to the combination of enhanced molecular ion and MS–MS. We demonstrate a few seconds long GC–MS–MS analysis of diazinon, spiked at 10ng/g in a mixed fruit and vegetable extract. The feature of enhanced molecular ion provides significant enhancement in the detection sensitivity via SIM and RSIM on the molecular ion. While octafluoronaphthalene (OFN) detection limit of below 1fg in SIM mode is shown, the harder is the compound analysis by standard GC–MS the greater is the gain in sensitivity by 1200-SMB. For example, the use of the 1200-SMB resulted in an improvement of over 50 times in the RSIM detection limit of cholesterol on its molecular ion at m/z =386, and decabromobiphenylether could be analyzed in SIM mode at 1ppb with S/N>50 (peak-to-peak noise). [Copyright &y& Elsevier]

We developed a new instrumental approach, termed Supersonic GC–MS, which achieves fast, sensitive, confirmatory and quantitative analysis of a broad range of pesticides in complex agricultural matrices. Our Supersonic GC–MS system is a modification of a bench-top Agilent 6890 GC+5972 MSD with a supersonic molecular beam (SMB) interface and fly-through EI ion source. One of the main advantages of Supersonic GC–MS is an enhanced molecular ion (M+) in the resulting mass spectra. For example, The M+ was observed in all 88 pesticides that we studied using the Supersonic GC–MS whereas only 36 of 63 (57%) pesticides that we investigated in standard GC–MS exhibited a M+. We also found that the degree of matrix interference is exponentially reduced with the fragment mass by about 20-fold per 100 amu increasing mass. The enhancement of the M+ combined with the reduction in matrix background noise permit rapid full scan analysis of a potentially unlimited number of pesticides, unlike selected ion monitoring or MS–MS in which specific conditions are required in segments for targeted pesticides. Furthermore, unlike the case with chemical ionization, EI-SMB-MS spectra still give accurate identification of compounds using common mass spectral libraries. In practice, we found that libraries favor mass spectra in which the M+ appears, thus Supersonic GC–MS produced better spectra for compound identification than standard GC–MS. To achieve even lower identification limits, the M+ plus a second major ion (still using full scan data) gives higher signal-to-chemical noise ratios than the traditional 3-ion approach. The replacement of two low-mass ions with the M+ (supersonic two-ions method) results in a significant reduction of matrix interference by a factor of up to 90. Another main advantage of Supersonic GC–MS is its exceptional suitability for fast GC–MS with high carrier gas flow-rate. Fast Supersonic GC–MS was able to analyze thermally labile pesticides, such as carbamates, that are difficult or impossible to analyze in standard GC–MS. Large volume injection using a ChromatoProbe was also demonstrated, in the 6 min analysis of pesticides at 20 ng/g in a spice matrix. [Copyright &y& Elsevier]