SELECTED ION FLOW TUBE MASS SPECTROMETRY. Interscience Expert Center: VIP Meeting 15 Sept. 2009

Transcription

1 SELECTED ION FLOW TUBE MASS SPECTROMETRY Interscience Expert Center: VIP Meeting 15 Sept. 2009

2 PROGRAM u: The IS. X strategy u: What exactly is SIFT-MS? u: Developing methods on the Voice u: Reproducibility at ultratrace levels u: Hyphenating Syft to less straightforward inlet systems u: Application of µ-cte/sift-ms in the beer industry u: Mobile applications with SIFT-MS u: Closing remarks and end

3 WHAT EXACTLY IS SIFT-MS? Hardware, theory and basic principles

4 SUMMARY The following topics will be addressed during this presentation, General introduction SIFT-MS technology Principles & theory

5 HISTORY The technique of SIFT-MS, Developed in the 1970s Measurement of kinetic data for gasphase ion/neutral reactions Demonstrated as a trace analytical technique in the 1990s

6 THE EARLY DAYS

7 NOWADAYS SIFT-MS detects & quantifies trace amounts of target volatiles, Absolute concentrations From whole air In real time PPT level concentrations Organic & inorganic compounds

8 THEORY The key is in the name, S I : selected precursor ions (H 3 O +, NO +, O 2+ ) F T : injected in a thermalized flow tube MS : mass spectrometric detection in real time SIFT-MS is based on soft ionisation, which minimises fragmentation.

9 HARDWARE Configuration of the Syft Voice 200, Reagent ion generation Reagent ion selection (Q1) Ion/sample reactions in flight tube Reaction products selection (Q2) Detection

10 REAGENT IONS Ions are generated under microwave heating, N 2 + O + N + H 2 O + H 2 O + H 2 O + O 2 + N 2 H + O 2 + O 2 + H 3 O + H 3 O + NO + H 3 O + No reaction with the major constituents of air.

11 FLIGHT TUBE The flight tube is fed with helium, Provide thermalized reaction conditions Minimize diffusion Inert transport medium Flight tube bent in 90 angle for size reduction.

12 CHEMICAL IONISATION Typical CI reactions that occur inside the flight tube, Precursor Flight tube Detection H 3 O + Proton transfer MH + M+1 NO + Hydride abstraction [M-H] + M-1 Hydroxide abstraction [M-OH] + M-17 Addition M.NO + M+30 O 2 + Charge exchange M + M Thermalized reaction conditions permit absolute quantification. SIFT-MS 12

13 REAGENT MULTIPLICITY The use of three CI agents increases confidence, H 3 O + NO + O 2 + Acetone , 58 Mw 58 Propanal , 58 Mw 58 Separation of isobaric and isomeric compounds.

14 QUANTIFICATION The absolute concentration of a particular analyte, Flowrate of sample gas into the flight tube Reagent and product ion signals Rate coefficient of the reaction between reagent and analyte Rate coefficients for > 400 compounds are stored in the Syft database.

15 CONCLUSIONS Most important advantages of the Syft instrument, Easy-to-use Fast analysis No sample prep required Absolute quantification Multiple reagent agents Broad application range

16 DEVELOPING METHODS ON THE VOICE 200 Basic strategy and practical examples

17 SUMMARY The following issues will be presented today, How to start developing Syft methods Initial optimization Fine tuning This presentation is accompanied by a software demonstration.

18 STARTING POINT SIFT-MS is generally used for target analysis, Define target components Select monitored reactions Beware of primary & secondary product ions.

19 OPTIMISATION In a second step one should, Verify reaction rates Verify branching ratio Eliminate all conflicts Calculate cycle time

20 CONFLICTS Conflicts occur when products ions from different compounds have the same mass or when product ions occur at the same mass of a reagent ion, Both primary and secondary ions Concentration level Reaction rate Branching ratio And what about matrix interferences?

21 FINE TUNING Critically evaluate test results, Blanks, standards and real samples Remove inaccurate and/or instable traces Example: analysis of contaminants in CO2

22 EXAMPLES

23 EXAMPLES

24 EXAMPLES

25 EXAMPLES

26 EXAMPLES

27 EXAMPLES

28 REPRODUCIBILITY AT ULTRATRACE LEVELS Correct standardisation and blank control

29 SUMMARY The following issues will be addressed today, Critical considerations Preparation of standards Analytical setup Results & discussion Closing remarks

30 CRITICAL CONSIDERATIONS The reliability of any gas analytical system largely depends on the reliability of the standard used to validate the system, Proper preparation of standards Proper sample introduction Proper blank control Adequate system control

31 INTENDED CONCENTRATION LEVELS PPM (one part per parts): Equivalent to one drop of water diluted into 50 liters or one second of time in approximately 11.5 days. PPB (one part per parts): Equivalent to one drop of water diluted into 250 chemical drums (+/ L) or one second of time in approximately 32 years. PPT (one part per parts): Equivalent to one drop of water diluted into 20, two-meter-deep Olympic-size swimming pools or one second of time in approximately years.

32 STANDARD PREPARATION Preparation of low level gas standards, Tedlar bag Canister Permeation tubes ASTM METHOD D 4051 Details are described in ASTM D4051.

33 TEDLAR BAG Most straightforward, but not the correct way to proceed, Increased blank levels, e.g. acetic acid, phenol, DMAC Memory effects, e.g. methanol Loss of polar compounds, e.g. formaldehyde Not suitable for reactive compunds Risk of condensation of compounds

34 IN-LINE PREPARATION Systems equipped with permeation tubes, Sub-ppb to %-level Modular Humidification Compressed gas

35 PERMEATION TUBES Small containers filled with a pure chemical compound in a two-phase equilibrium between gas and liquid phase. Containers are made in inert polymeric material and held at constant temperature. The device emits the compound through a permeable wall at a constant rate. The permeate is mixed with carrier gas at a controlled flow rate to obtain a known mixture that can be used as reference gas.

36 CONSEQUENCES SIFT-MS is more susceptible to interferences at low levels, High sensitivity No chromatographic pre-separation Dedicated precautions are required to permit appropriate evaluation.

37 DEDICATED SET-UP The evaluated set-up consists of, Zero air generator Permeation tube chamber with six tubes Direct split interface Closed system

38 SCHEMATIC Direct sampler with split interface Zero air generator Permeation tube chamber Syft VOICE200

39 EXPERIMENTS Prime aim was to focus on, Blank levels and blank control Repeatability of results Reproducibility of results Linearity

40 BLANK LEVELS Absolute level is function of the quality of supplied air, Laboratory air? Compressed nitrogen In-line filter systems Zero air from generator

41 LABORATORY AIR The IS-X lab air was contaminated with, Hexane Dichloromethane GC/MS analysis of lab air. No information on polar solvents.

42 RESULTS Several types of gas supply were evaluated, Compound Blank N2 Thermo filter Restek filter Blank Zero air Acetaldehyde Acetone Formaldehyde Heptane M-xylene Toluene All concentrations in ppb

43 REPEATABILITY Analysis of permeation feed, Compound 30 ppb 15 ppb 10 ppb 5 ppb 2.5 ppb Acetaldehyde Acetone Formaldehyde Heptane M-xylene Toluene

44 REPRODUCIBILITY Daily analysis of 15 ppb standard (QCS), 120 Acetaldehyde Acetone Formaldehyde Heptane Toluene M-xylene Compound %RSD 100 Acetaldehyde Acetone Day Formaldehyde 8.80 Heptane 10.1 M-xylene 7.21 Toluene 11.1 Please note that SIFT-MS does not use internal standards!

45 LINEARITY (1) Overview of calibration curves, Acetaldehyde Linear (Acetaldehyde) Acetone Linear (Acetone) Formaldehyde Linear (Formaldehyde) R 2 = R 2 = R 2 =

46 LINEARITY (2) Overview of calibration curves, Heptane Linear (Heptane) Toluene Linear (Toluene) M -xylene Linear (M -xylene) 8.25 R 2 = R 2 = R 2 =

47 CONCLUSION Relevant operation at ultratrace levels, Control of blank levels Reproducible standard preparation Proper system control

48 EXPANDING THE APPLICATION AREA OF SYFT Hyphenation to less straightforward inlet systems

49 SUMMARY The following issues will be addressed today, Overview of Voice 200 inlets Precautions Coupling types Examples

50 HYPHENATION IN PRACTICE A number of factors need to be taken into account, Selection of Syft inlet type Direct or indirect coupling Short transfer paths Inertness

51 SYFT INLETS The Syft Voice 200 has a variety of inlets configured, Two standard sample inlets (front) One direct inlet (front) One ambient inlet (rear)

52 STANDARD INLET Particularly suited for the introduction of, Canisters Tedlar bags Monitoring Inlet is equipped with a needle valve and closed from exterior air. Permits automatic background subtraction.

53 DIRECT INLET Particularly well-suited for the analysis of, High sensitivity analyses Less volatile compounds Active compounds The direct inlet provides immediate entrance to the flight tube.

54 HEATED EXTERNAL INLET The direct inlet is fitted with a heated transferline, Flexible tube Inert path (Siltek) Heatable to 200 C Internal restriction Absolute sensitivity is proportional to total flow towards the flight tube.

55 PRECAUTIONS When using the direct inlet, Avoid valves in the flow path Control administered flows Beware of dirty samples Beware of leaks Beware of cold spots

56 INDIRECT COUPLING This configuration is most suited when, The sampling point needs to remain accessible Inlet flows are too high Sensitivity is less of an issue Indirect coupling uses a restriction. Two types: 10 ml/min and 40 ml/min

57 DIRECT COUPLING This configuration is most suited when, Sensitivity is important Inlet flows are constant Inlet flows are accurately controlled Direct coupling does not use a restriction.

58 HYPHENATED SYSTEMS The following sample introduction systems were hyphenated, Static headspace injection with CombiPAL Thermodesorption with Unity 2 Material emissions with Microchamber

59 STATIC HEADSPACE The easiest way to introduce volatile components, Well understood Dedicated autosamplers Broad application area Aqueous and non-aqueous

60 IN PRACTICE Practical hyphenation was achieved, CombiPAL installed on TraceGC S/SL injector with laminar cup liner Direct coupling to Syft, i.e. without restriction Retention gap at 150 C MS transferline at 150 C

61 METHOD DEVELOPMENT Parameters that need optimization, Injection type: split or splitless Injection rate Syft acquisition parameters

62 RESULTS AND DISCUSSION Experiments were carried out in the field of, Environmental: analysis of BTEX in water Chemical: analysis of solvents Food: analysis of aldehydes in malt

63 BTEX IN WATER Considerations, Occuring conflicts Injection optimisation Blank levels Repeatability Linearity

64 SYFT METHOD Overview of key parameters, Dwell time: 100 ms per single reaction Analysis time: sec Tolerance ratio: 20 % Reagents: H 3 O +, NO + and O + 2

65 SYRINGE SELECTION Accurate quantification necessitates stable analyte flows, Syringe, ml 10 µl/sec 20 µl/sec 50 µl/sec min 0.8 min 0.3 min min 2.1 min 0.8 min min 4.2 min 1.7 min Use of multi-injection methods, e.g. splitless and split in one run Use of multi-syft methods, e.g. optimal dwell times

66 INJECTION SPEED Fast injection reduces carrier gas dilution, thus increases absolute response, Benzene Ethyl benzene + xylenes Toluene Fast injection disturbs Syft analysis stability.

67 VALIDATION (1) Blank levels and repeatability, Compound Blank, ppb 20 ppb, %RSD Benzene Ethylbenzene + xylenes Toluene No interferences detected Highly repeatable analysis

68 VALIDATION (2) Linearity, Benzene Toluene Ethylbz + xylenes Response Conc, ppb Response Conc, ppb Response Conc, ppb R² = R² = R² =

69 SOLVENTS Considerations, Broad range of target compounds High concentration levels Real samples contain limited number of solvents Many negative samples Tedious calibration procedure

70 SYFT METHOD Overview of key parameters, Dwell time: 100 ms per reaction Analysis time: sec Tolerance ratio: 20 % Reagents: H 3 O + and NO +, no O 2+! Target compounds: ACN, EtOH, EtOAc, i-proh and iso-octane (IS)

71 VALIDATION (1) Blank levels and repeatability, Compound Blank, ppb 500 ppm, %RSD 50 ppm, %RSD 2-Propanol Acetonitrile Ethanol Ethyl acetate Iso-octane Little interference due to high reporting limit Repeatable analysis at various levels

72 VALIDATION (2) Linearity, R 2 = R 2 = R 2 = R 2 = (EtOAc) (ACN) (EtOH) (i-proh) Conc, ppm

73 VALIDATION (3) Reproducibility, 2-Propanol Acetonitrile Ethanol Ethyl acetate All RSDs < 10%; EtOH and EtOAc < 5%.

74 THERMAL DESORPTION A well understood way of preconcentrating air samples, High sensitivity analyses Superior limits of detection Environmental monitoring Material emissions, e.g. automotive

75 IN PRACTICE Practical hyphenation of both systems, Unity 2 transferline Syft direct heated transferline Direct coupling, i.e. without restriction Flowrates matched

76 METHOD DEVELOPMENT Parameters that require optimization, TD parameters, e.g. desorption temperature Split ratio Trap heating rate

77 SYFT METHOD Overview of key parameters, Dwell time: 100 ms per reaction Analysis time: 250 sec Tolerance ratio: 20 % Reagents: H 3 O +, NO + and O + 2

78 RESULTS AND DISCUSSION Following analyses were carried out, Syft standard on Tenax Standard TD settings Sensitivity Linearity

79 SYFT STANDARD Tube loaded with ng of analytes,

80 LINEARITY Ethylbenzene,

81 MICROCHAMBER A fast way for sensitive material emission analysis, Miniature emissions testing Six samples at 120 C Four samples at 250 C Inert interior No complex pneumatics

82 IN PRACTICE Practical hyphenation of both systems, Restriction installed on Syft TD tube with frit fixed in front of restriction Total assembly connected to µ-cte Restriction permits exposure of transferline to ambient air.

83 RESULT AND DISCUSSION Several experiments were carried out using the µ-cte/syft hyphenation. Results will be discussed in the next presentation. Thank you for your attention