BenchTOF-dx. High-performance time-of-flight mass spectrometer for gas chromatography

Transcription

1 BenchTOF-dx High-performance time-of-flight mass spectrometer for gas chromatography

2 BenchTOF-dx High-performance mass spectrometry BenchTOF-dx is an innovative time-of- ight mass spectrometer for gas chromatography (GC). It is compatible with every GC application and offers full spectral sensitivity at similar levels to the selected ion monitoring (SIM) mode of quadrupoles. This ground-breaking instrument is also more than equal to the challenges of advanced research applications. By offering identi cation and measurement of both target compounds and unknowns in highly complex matrices, BenchTOF-dx is right at the frontier of GC/MS technology. BenchTOF-dx is currently providing enhanced analytical performance in the following elds: Environmental contamination Oil exploration and petroleum research Food safety Metabolomics Homeland security Toxicology BenchTOF-dx enhances full-spectral GC/MS analysis 2

3 High-de nition mass spectrometry ensures optimum GC analytical performance BenchTOF-dx A time-of- ight mass spectrometer designed speci cally for gas chromatography BenchTOF-dx is designed to bring together a unique combination of ve key features that deliver high-de nition mass spectrometry and outstanding performance for every GC application. 1 Sensitivity BenchTOF-dx delivers full-range spectra at the sensitivity levels of quadrupole instruments running in selected ion monitoring (SIM) mode. This generates outstanding results for trace-level analysis of both target components and unknowns. 2 Stability The rugged design of BenchTOF-dx ensures long-term stability of mass and analyte response, even for the dirtiest samples. This reduces the frequency of tuning and calibration, and dramatically extends the intervals between scheduled maintenance, for optimum productivity. 3 Selectivity Sub-unit mass resolution allows selective elimination of interferences and dramatic improvement of signal-to-noise ratios. This further enhances detection of trace analytes in complex matrices. 4 Spectral quality The reference-quality spectra (m/z ) produced by BenchTOF-dx simplify component identi cation by library searching, for example, using the NIST database. 5 Speed The high-speed spectral acquisition (10,000 spectra per second) of BenchTOF-dx makes it amenable to all types of gas chromatography. The information-rich datasets allow enhanced deconvolution and analysis of complex GC/MS pro les. The unique, synergistic combination of these ve key attributes delivers high-de nition mass spectrometry a powerful solution for the most challenging GC applications. Clarity of detail. The information-rich GC/MS dataset generated by BenchTOF-dx facilitates high-de nition, detailed analysis of trace components in complex, heavily contaminated samples. 3

4 No bench-top mass spectrometer can compete with the full-spectral sensitivity of BenchTOF-dx 1 Sensitivity BenchTOF-dx has enhanced sensitivity compared to older time-of- ight mass spectrometers a result of using highly ef cient direct ion extraction (dx). This is the process whereby ions are powerfully ejected straight from the source, towards the detector, by a very large, rapidly-pulsed accelerating voltage. In contrast, most time-of- ight MS systems use orthogonal extraction, which involves continuous transfer of ions from the source to a push-out region. Only a fraction of these ions are then pulsed to the detector, resulting in a lower signal. In practice, direct extraction allows BenchTOF-dx to acquire spectra at similar sensitivity levels to those obtained using selected ion monitoring (SIM) on a quadrupole instrument, but across the full spectral range (m/z ). This satis es the demand for reliable measurement of trace compounds both target species and unknowns in a single analysis. BenchTOF-dx harnessing direct extraction of ions from the source for optimum sensitivity 4

5 Sub-unit mass accuracy reduces matrix interferences and optimises sensitivity Total ion chromatogram (TIC) Extracted-ion chromatogram (EIC) ± 0.5 Da 1 ppb dichlobenil Extracted-ion chromatogram (EIC) ± Da Trace pesticides in crude apple extract successfully identi ed using BenchTOF-dx. Top: Total ion chromatogram (TIC) of 1 ppb dichlobenil in a crude extract of apple spanning a mass range Da with a data rate of 5 Hz. Middle: Extracted-ion chromatogram (EIC) for m/z using a window of ±0.5 Da, showing the signal enhancement of BenchTOF-dx at unit mass. Bottom: EIC for m/z using a window of ±0.050 Da. This demonstrates the advantage of high signal intensity combined with accurate sub-unit mass operation eliminating all interferences from the chemical matrix. 5

6 Reproducible detector response increased productivity 2 Stability The innovative design of BenchTOF-dx fundamentally reduces the build-up of organic residues inside the ion source. The result is a highly stable response, and a greatly reduced need for cleaning or maintenance. This is a signi cant advance on existing GC mass spectrometers, which get contaminated over time and rely on increasing voltages to offset any resulting loss of sensitivity. Using conventional systems, voltages eventually reach a point where they cannot be increased any further, and at that stage the source has to be cleaned. The direct extraction technology used in BenchTOF-dx allows very large voltages to be applied, greatly extending the interval between source cleaning. In addition, any voltage changes that are eventually required are insigni cant relative to those used for ion extraction. This further enhances the stability of the detector relative to other MS systems. Complementing this excellent response stability is outstanding mass stability. BenchTOF-dx ensures mass accuracy is maintained over extended periods by in-built temperature compensation, ef cient pumping and optimised electronic control of applied accelerating voltages. This minimises the required calibration frequency. The net result of these innovations is minimal variation in performance, even after weeks or months of continuous operation. This makes BenchTOF-dx ideal for challenging environmental, food or clinical applications where matrix effects would otherwise require frequent downtime for cleaning and maintenance. Analytical linearity over more than 4 orders of magnitude Area response m/z 107 R² = Peak area (m/z ) Concentration (ppb) A seven-level calibration of 2-ethylpyrazine with two points at each level (2.5 pg to 50 ng). The inset shows lower-level points. 6

7 Long-term mass stability Fragment ion m/z RSD (%) (n = 18) C 9 F 20 N Flight time (ns) C 4 F 9 + C 3 F CF Day The exceptional mass stability of BenchTOF-dx for four fragment ions of PFTBA (per uorotributylamine). Time-of- ight mass spectrometry harnesses the principle that the time taken for an ion to travel along the ight tube depends on its mass-to-charge ratio. This graph illustrates the exceptional stability of arrival times at the detector of BenchTOF-dx over a 50-day period, for a range of fragment ions. Chromatographic repeatability 5.0 Area (normalised to internal standard) Tribromoanisole Pesticide RSD (%) (n = 14) Tribromoanisole 5.75 EPN 4.52 cis-permethrin Sample The excellent chromatographic repeatability possible with BenchTOF-dx is illustrated by this example, which shows pesticide standards (10 ppb) spiked into a cucumber matrix with sample preparation using QuEChERS. %RSD data are shown tabulated for tribromoanisole, O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN) and cis-permethrin. All the data for tribromoanisole are also shown graphically; the green line shows the mean of the values, and the red lines show one standard deviation. 7

8 Sub-unit mass resolution 3 Selectivity The exceptional mass stability of BenchTOF-dx and inherent advantages of direct extraction (in terms of signal intensity and operational robustness) are perfectly complemented by accurate sub-unit mass resolution. BenchTOF-dx offers sub-amu resolution without compromising system sensitivity. This provides outstanding selectivity for the detection and identi cation of trace target and non-target compounds in complex matrices. Sub-amu resolution bene ts a wide range of challenging GC applications by allowing selective elimination of matrix interferences, which dramatically improves signal-to-noise ratios. Relevant application examples include analysis of persistent organic pollutants (POPs) in foods and the detection of drugs of abuse in biological extracts. Enhanced selectivity improves quanti cation of trace components Unit-mass extraction window Da extraction window TIC TIC Diazepam (quantitation ion) Diazepam (quantitation ion) Diazepam (quali er ion) Diazepam (quali er ion) Detection of target and non-target drugs in a urine extract. In this case, diazepam was an unexpected analyte. The left panel shows 1 dalton-wide extracted-ion chromatograms, with numerous interferences. The right panel shows application of a much narrower (0.020 Da) extraction window, which successfully removes matrix interferences from the diazepam traces, enabling precise ion ratio measurement and quanti cation. 8

9 Selectivity enhances sensitivity OFN S/N 2747 unit mass ± 0.5 Da Noise magni ed 500 OFN accurate mass ± Da Noise magni ed 500 This analysis of octa uoronaphthalene illustrates the positive impact of BenchTOF-dx selectivity. The top trace shows a 1 Da EIC of 1 pg octa uoronaphthalene (OFN), acquired over the mass range Da. Octa uoronaphthalene elutes at 5.23 min, but other chemical peaks are also present. Even at 1 amu the enhanced sensitivity of BenchTOF-dx is clearly demonstrated, with a root-mean-square signal-to-noise ratio of 2747 for 1 pg OFN. The bottom trace shows the same dataset but after applying a much narrower (0.02 Da) extraction window. This eliminates chemical and system noise without reducing signal intensity, which has a dramatic effect on sensitivity. Analytical linearity for octa uoronaphthalene The exceptional linearity for pg octa uoronaphthalene is demonstrated by this plot, which shows that BenchTOF-dx provides outstanding performance even at trace levels. Area counts R 2 = Mass on column (pg) 9

10 Enhanced, automated library searching 4 Spectral quality BenchTOF-dx produces reference-quality mass spectra that are a close match to the classical EI mass spectra generated by quadrupole instruments. This addresses the spectral distortion drawback of many other TOF instruments, and allows BenchTOF-dx users to take full advantage of commercial libraries such as those provided by NIST and Wiley. The excellent spectral quality of BenchTOF-dx data is a result of innovative and intelligent system design. Particular features include: Preservation of molecular ions for high-boiling hydrocarbons a challenge for most other TOF instruments. Excellent ion discrimination a result of the sub-amu resolution. Accurate relative intensities across the massrange, providing enhanced spectral matching. Skew-free spectra. Time-of- ight mass spectrometers are inherently skew-free, and BenchTOF-dx is no exception. This stands in contrast to scanning instruments such as quadrupoles, where the ratio of ions eluting from the GC column can change signi cantly during the nite time that it takes to scan across a given mass range. Consistent spectra. Powerful differential pumping allows BenchTOF-dx to accommodate the wide range of changing pressures eluting from GC columns. This ensures that the mass spectrometer delivers consistent spectra irrespective of sample loading. Negligible detector ringing. Detector oscillation ( ringing ) often causes signal distortion on TOF systems, particularly at low masses. BenchTOF-dx hardware and electronics have been designed to minimise these destructive oscillations and extend the practical operating mass range of the system, for example to hydrogen isotopes. High resolution at low mass Counts H + H 2 + He m/z Negligible detector ringing allows BenchTOF-dx to be applied to the lowest limits of the mass range. This pro le spectrum shows detection of hydrogen and helium ions at 1, 2 and 4 Da, illustrating the extremely high resolving power of BenchTOF-dx in low-mass applications. 10

11 Preservation of molecular ions Abundance m/z Spectral quality is maintained across the full mass range, as demonstrated by this mass spectrum of decabromodiphenyl ether (BDE-209), derived from just 25 pg on-column (GC GC/TOF MS). With a mono-isotopic molecular weight of Da, high boiling point, and sensitivity to column activity and hot spots in the sample path, it is a challenging compound to detect at trace levels by GC/MS. The detail of the molecular ion cluster in this low-level analysis is indicative of the quality of the spectra produced by BenchTOF-dx. m/z Absolute abundance Relative abundance (%) Experimental Theoretical (from NIST) The mass spectrum of tetracontane (n-c 40 H 82 ) shows a distinct molecular ion ( Da), with the M+1 ion ( Da) abundance ratio predicted by theory (see table). The fact that BenchTOF-dx can measure the intensities of these diagnostic but low-abundance ions greatly facilitates molecular formula determination. In contrast, molecular ions from large (>C 35 ) alkanes are rarely seen in EI spectra from other TOF MS systems for GC. 11

12 One detector every GC application 5 Speed BenchTOF-dx accumulates 10,000 native spectra per second across the full range of the instrument ( Da). Whatever operations are subsequently performed on this data, a wealth of detailed spectral information is always available should it be needed. The high data acquisition rate of BenchTOF-dx offers added insight into complex chromatograms spectral deconvolution and chemometric techniques for compound identi cation depend on a certain level of de nition to differentiate between components. The high data acquisition rate of BenchTOF-dx greatly enhances the performance of such post-run data-processing software. High data acquisition rates help ensure reliable quantitation. Whatever sampling rate is initially selected, there is always enough data-density for precise re-integration and post-run optimisation of quanti cation if required. The 10,000 spectra acquired every second also make BenchTOF-dx an excellent choice for demanding GC applications, such as fast GC and comprehensive 2D GC (GC GC). High-speed data acquisition for fast or multi-dimensional GC analyses Diesel particulates: NIST standard reference material analysed by thermal desorption GC GC/TOF MS. To achieve such a well-de ned separation across two dimensions, a high data rate (70 spectra/s) is needed. The speed of BenchTOF-dx provides the ability to characterise enormously complex samples such as these diesel particulates. 12

13 A high data rate allows powerful deconvolution of overlapping peaks High-speed analysis of perfume spiked with allergens. A data rate of 20 Hz (or 500 summed spectra per data point) applied to this spiked perfume sample means that closely co-eluting peaks can be deconvolved, allowing target compounds of interest to be identi ed. The magni ed region at 4.28 min shows the allergen methyl 2-octynoate (red trace, with a basal peak width of approx. 1.0 s) as a contributor to a large multi-component peak (blue trace), despite being dwarfed by co-eluting components (grey traces). A high data rate also has bene ts for library matching. The clean deconvolution of co-eluting compounds illustrated above has clear bene ts for library matching. In this case, matching against the NIST_11 library gave a library match of 88% for methyl 2-octynoate with probability 87%. The presence of the characteristic M 1 ion at 153 Da further demonstrates the quality of the spectra produced by BenchTOF-dx. 13

14 Engineered from rst principles BenchTOF-dx Innovative technology, elegant design BenchTOF-dx is engineered from rst principles to provide reliable MS detection and outstanding analytical performance for all major brands of GC. The system is rugged, requiring minimal intervention for routine applications, but at the same time offering expert users the performance and exibility required for specialist research work. Notable advantages include: High operating voltages and routine auto-clean cycles, which virtually eliminate the need for manual source cleaning. As a result, BenchTOF-dx operates for extended periods without routine maintenance. Ion source Re ectron Auto-optimisation of control parameters, which helps both experienced and inexperienced GC/MS users to maintain system performance and make the most of their time. The three-way, split- ow turbo-pump ensures that when the system needs to be vented, BenchTOF-dx can be back up and running within as little as 30 minutes. It also ensures that calibration gas clears rapidly after auto-tuning. Remote access to operating parameters. ALMSCO is the mass spectrometry division of global analytical instrument company Markes International Ltd. Wherever a BenchTOF-dx system is installed around the world, LAN communications enable remote diagnostics and ef cient fault recovery by Markes/ALMSCO engineers. LAN communications also facilitate off-site user training by BenchTOF-dx specialists. Detail of the BenchTOF-dx ight-tube 14

15 Discrimination-free analysis of high-boiling mixtures Retention time (min) PAH MW of extracted ion Area response Colour of trace 8.05 Benzo[c] uorene Turquoise 9.24 Benz[a]anthracene Red 9.34 Cyclopenta[cd]pyrene Grey 9.38 Chrysene Red Methylchrysene Purple Benzo[b] uoranthene Blue Benzo[k] uoranthene Blue Benzo[j] uoranthene Blue Benzo[a]pyrene Blue Indeno[1,2,3-cd]pyrene Green Dibenzo[a,h]anthracene Brown Benzo[ghi]perylene Green Dibenzo[a,l]pyrene Pink Dibenzo[a,i]pyrene Pink Dibenzo[a,e]pyrene Pink Dibenzo[a,h]pyrene Pink Analysis of a high-boiling polycyclic aromatic hydrocarbon (PAH) mixture, demonstrating highly resolved and symmetrical peaks, with excellent recoveries of the 6-ring dibenzopyrene isomers. The GC mass spectrometer interface is a critical part of the sample ow path demanding precise and uniform temperature control. With BenchTOF-dx this is guaranteed because the transfer line is formed from and implicitly insulated by the high vacuum of the source chamber. BenchTOF-dx also controls the temperature of the interface, facilitating connectivity with any make of gas chromatograph. Stemming from its research-grade origins, the upper limits of BenchTOF-dx temperature regulation meet or exceed the working range of all known GC columns. The rapid, split analysis of a Florida mixture (n-alkanes of even carbon-number), illustrating freedom from discrimination over the volatility range C 12 to C 40. This is only achievable when the heated GC-to-MS interface is uniform, inert and has no impact on the analysis. 15

16 MOSAIG-HD software brings out the best in BenchTOF-dx MOSAIG-HD Software for BenchTOF-dx Versatility and ease-of-use The MOSAIG-HD software package provided with every instrument offers a uniquely versatile and powerful interface to BenchTOF-dx. As well as being physically compatible with all major makes of GC, MOSAIG-HD enables BenchTOF-dx data to be seamlessly converted to the le formats of several popular GC/MS data analysis platforms. This allows the analyst to take advantage of the power of BenchTOF-dx while remaining in a familiar GC/MS operating environment, minimising the operator learning curve and enhancing productivity in highthroughput laboratories. Powerful processing for exceptional analytical results For high-throughput routine operation, the compatibility of BenchTOF-dx with a variety of data-analysis platforms is ideal. However, in order to realise the full power of BenchTOF-dx, including sub-amu resolution, users are recommended to take advantage of the full data-processing functionality of MOSAIG-HD, which includes advanced spectral deconvolution and data-mining. As well as the standard functionality required for GC/MS data processing, MOSAIG-HD offers a number of unique features that amplify the bene ts of high-de nition mass spectrometry. These are described on the following pages. BenchTOF-dx integration with existing data-analysis platforms 16

17 Enhanced real-time functionality MOSAIG-HD allows the user to view and analyse data as it is generated, speeding up method development and optimisation. Rather than taking a snapshot, MOSAIG-HD allows access to the entire dataset collected up to the selected time, providing high-quality data on the spot and a clear picture of how the analysis is proceeding. Dynamic background compensation (DBC) MOSAIG-HD facilitates dynamic background compensation to selectively eliminate chemical interference (for example column bleed) as it changes over time. DBC is implemented automatically, eliminating the need for manual subtraction of the background. Importantly, no peak-related ions are affected, even if the ions are common to both the background signal and a co-eluting chromatographic peak. MOSAIG-HD displays the original and backgroundcompensated chromatograms simultaneously for optimum clarity, and both data les are stored for future use (for example, manual re-integration). Without DBC With DBC The analysis of a Chinese alcoholic spirit, illustrating the power of MOSAIG-HD to identify trace components. Left: Total ion chromatograms with and without dynamic background compensation, showing the dramatic improvement DBC has on the TIC baseline. Right: The resulting mass spectra for the minor component at min (circled) show that without DBC the spectral identity of the compound is masked by background ions. The improved quality of the spectrum offered automatically by DBC allows con dent matching against the NIST reference library. 17

18 Added insight into complex chromatograms Deconvolution of overlapping peaks MOSAIG-HD features a powerful spectral deconvolution algorithm to separate individual unresolved components contributing to a single chromatographic peak. This functionality takes full advantage of the high-speed data acquisition of BenchTOF-dx, and enhances searching against spectral libraries. Matching against target libraries The reference-quality spectra generated by BenchTOF-dx means that matching against standard spectral libraries is simple and reliable. To complement standard library searching, MOSAIG-HD also offers an advanced searching algorithm based on principal components analysis (PCA). This allows the automated comparison of spectra from real-time or post-run chromatographic data against a user-speci ed set of target spectra. When PCA is used in conjunction with spectral deconvolution, target matching is greatly enhanced. The process is also independent of chromatographic retention times and can therefore be applied to compare data collected using GC analytical columns of different dimensions, or with different stationary phases. Deconvolution of a complex TIC allows identi cation of 10 ppb tribromoanisole (red trace) in a complex TIC (blue trace). Co-eluting compounds are also indicated (grey traces). MOSAIG-HD con dently reports results without ambiguity because of an inbuilt PCA routine (depicted here). This extra step diminishes the likelihood of false-positives or false-negatives during compound identi cation. 18

19 Optimal processing for accurate mass MOSAIG-HD software makes the most of the high-de nition data generated by BenchTOF-dx. The graphical user interface allows operators to examine every analytical detail in total ion chromatograms, while extracted-ion chromatograms feature sub-amu accuracy for robust and repeatable quantitation. BenchTOF-dx data is also fully compatible with standard spectral libraries featuring sub-amu resolution, allowing greater elucidation. Ions of exact mass may be de ned as quanti er or quali er ions for enhanced, interference-free calibration and quanti cation. Calibration/quantitation of pesticides using sub-amu ion resolution The graphical user interface of MOSAIG-HD. Above: The application of a quantitative processing method to a data le, showing detection and quantitation of compounds found in a complex sample during food safety testing. Right: A multi-point calibration based on the sub-amu extracted ions for a target analyte (tribromoanisole), allowing quantitation of sample components. 19

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