SPME - DIFFUSIVE SAMPLING FIBER HOLDER (DFH) for TWA Analysis

Transcription

1 Page 24 Page 1 SPME - DIFFUSIVE SAMPLING FIBER HOLDER (DFH) for TWA Analysis Manual Cat.No U CHROMLINE Via Anita Garibaldi, Prato (PO) Italy Phone: Fax: info@chromlinesrl.com web: CHROMLINE SRL. Printed in Italy. Ver.1.6 Chromline Srl Via Anita Garibaldi, Prato (PO) Italy Phone: FAX: info@chromlinesrl.com web:

2 Page 2 Page 23 REPLACEMENT PARTS & ACCESSORIES IMPORTANT NOTE This holder accepts only SPME Fast Fit Assemblies (FFA). Standard SPME fibers do not work and can be damaged when attempted to be used with this holder. DFH Parts: Magnetic Plunger (H6) (DFH000D) Needle Protection Cage (H3) (DFH002) PTFE Sealing Cups (SC1) Parts included with U: 1x DFH Holder 1x Magnetic Plunger 1x Stainless Steel Needle Guide 1x PTFE Sealing Cup 23ga Blunt 1x PTFE Sealing Cup 24ga Blunt Stainless Steel Needle Guide (SC2) Sealing Mechanism (H5) (DFH000B) Holder end cap (H4) (DFH005) DFH Body (H1) DFH Body Screw (H2) (DFH004) DFH Manual Desorption Adapter (Optional Accessory, DFH00C) FFA FIBERS Recommended for VOC Sampling FFA57295-U PK3, 85 μm CAR/PDMS STABLEF. SPME Fast Fit Assembly 23 ga FFA57335-U PK3, 85 μm CAR/PDMS STABLEF. SPME Fast Fit Assembly 24 ga Other fibers FFA57293-U PK3, 65μm PDMS-DVB Stableflex SPME Fast Fit Assembly 23ga FFA57327-U PK3, 65 μm PDMS-DVB Stableflex SPME Fast Fit Assembly 24 ga FFA57298-U PK3, 50/30 μm DVB/CAR/PDMS Stableflex SPME Fast Fit Assembly 23 ga FFA57329-U PK3, 50/30 μm DVB/CAR/PDMS Stableflex SPME Fast Fit Assembly 24 ga FFA57341-U PK3, 100 μm PDMS SPME Fast Fit Assembly 23 ga FFA57301 PK3, 100 μm PDMS SPME Fast Fit Assembly 24 ga FFA57294-U PK3, 85 μm POLYACRYLATE SPME Fast Fit Assembly 23 ga FFA57305 PK3, 85 μm POLYACRYLATE SPME Fast Fit Assembly 24 ga FFA57354-U PK3, 60 μm PEG Metal SPME Fast Fit Assembly 23 ga FFA57309 PK3, 30 μm PDMS SPME Fast Fit Assembly 24 ga FFA57302 PK3, 7 μm PDMS SPME Fast Fit Assembly 24 ga FFA57289-U PK3, 30 μm PDMS SPME Fast Fit Assembly 23 ga FFA57291-U PK3, 7 μm PDMS SPME Fast Fit Assembly 23 ga PTFE Sealing Mechanism U PK3, PTFE sealing cups 23ga blunt one identification line (SFSC23BL) U PK3, PTFE sealing cups 24ga blunt two identification lines (SFSC24BL) U Stainless steel guide of needle (SFSC000A) Replacement Parts U Magnetic plunger (Z-Setting) for SPME-DFH (DFH000D) U SPME-DFH Sealing unit (DFH000B) U Holder end cap (DFH005) custom Needle protection cage (DFH002) Accesories U DFH manual desorption adapter (DFH000C) U SPME FFA Storage Container

3 Page 22 Page 3 Name Conc. (mg/m 3 ) in Tedlar bag 25 L % Loss after C RSD% (n=5) % Loss after 15 Room Temp. ( C) RSD% (n=5) % Loss after C RSD% (n=5) Dichloromethane 16,625-6,9 6,6-4,6 7,9-11,3 8,2 MTBE 9,25-2,8 9,8-7,2 4,3-4,3 9,2 n-hexane 8,25-4,3 8,7-8,1 4,6-6,1 6,7 1,1,1 Trichloroethane 16,75-4,9 6,2-1,4 8,6-3,5 9,7 1,2 Dichloroethane 15,625-3,9 9,3-6,3 4,1-7,3 4,5 Benzene 11-5,3 4,1-6,7 4,1-5,5 6,2 Trichloroethylene 18,25-6,1 6,6-4,5 8,6-4,8 7,5 Toluene 10,875-4,7 6,8-7,8 6,5-6,3 2,9 Tetrachloroethylene 20,25-4,2 7,4-3,1 7,3-3,3 8,1 Ethylbenzene 10,875-5,5 5,3-5,7 4,5-6,1 5,0 m + p Xylene 10,75-5,1 3,7-4,0 7,5-4,9 5,5 o-xylene 11-4,8 6,1-6,8 4,6-6,2 3,5 1,3,5 Trimethylbenzene 10,875-3,5 8,8-4,3 5,5-5,9 5,4 1,2,4 Trimethylbenzene 10,875-5,6 6,3-5,1 4,5-5,5 8,3 INDEX INTRODUCTION 4 DFH HOLDER PARTS 6 ACCESSORIES 7 SPME FIBERS USED ON DFH 7 PTFE SEALING CAP INSTALLATION 8 SPME-FFA / FIBER INSTALLATION 10 ZERO AND SETTING OF Z-LENGTH 11 SAMPLING 14 ANALYSIS MANUAL DESORPTION 15 AUTOMATED DESORPTION (MFX System) 17 APPENDIX TABLE 1 Sampling rates 18 How to estimate Sampling Rates (SR) 20 Temperature correction 20 References for Diffusive sampling with SPME 20 PTFE Sealing Data 21 REPLACEMENT PARTS & ACCESSORIES 23

4 DIFFUSIVE SAMPLING FIBER HOLDER (DFH) Page 4 PTFE SEALING DATA Page 21 Introduction A DFH holder installed with a FFA is capable of determining time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which a fiber is extended outside its needle, during TWA passive sampling the fiber is retracted a known distance into its needle. The DFH SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to the fiber. Analyte molecules Piercing/protection needle Fiber Plunger The Chromline sealing mechanism ensures integrity of fiber conditioning as well as storage of sampled fiber. Below chromatograms show a cleaned fiber immediately desorbed and after conditioning (Fig. 56) and after15 days sealed with the PTFE Sealing Cap used in the DFH (Fig. 57). The sealed fibers were exposed to the atmosphere below mentioned compounds and concentrations. No contamination could be observed in that time. With the same test set up the storage stability of a sample was evaluated for the same mix of VOCs at different tempratures was evaluated. Temperatures was -4 C, room temperature ( C) and +40 C. The test was done with 85μm CAR/PDMS 23ga fiber (the same fibers were used for each temperature). For sampling the fibers were exposed 15 sec to the atmosphere of compounds mentioned in below table. For details on this study please contact Chromline under info@chromlinesrl.com. Diffusion distance Z SPME fiber 2010 Chromline Srl Fig. 1. Schematic of analyte molecular diffusion and sorption on to a fiber. This process is described with Fick s first law of diffusion, whereby determination of the amounts of analytes accumulated over time enables measurement of the TWA concentration to which the sampler was exposed. C m SR t _ where C is TWA concentration, m is analyte mass adsorbed, SR is sampling rate (which can be found/estimated in the Appendix in this manual) t is sampling time (e.g.15 min or 8 h). TWA passive sampling with a SPME device has been shown to be almost independent of air flow rate, and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length could be changed. Environmental conditions, e.g. temperature, pressure, relative humidity, and ozone, have little or no effect on sampling. For more details please refer to the references listed in the Appendix (page 10). Fig Fiber after conditioning. Fig Fiber 15 days into Chromline PTFE sealing cup.

5 Page 20 Compound CAS # Z3 SR theor. Z5 SR theor. Z10 SR theor. Z30 SR theor. (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) 1,2,3 trichlorobenzene , , , , ,2,4 trichlorobenzene , , , , How to estimate SR A SR D Z where: SR is sampling rate (cm 3 /min), A is surface area of the needle opening (A23ga= 1.464x10-3 cm 2 ; A24ga= 9.926x10-4 cm 2 ), Z is the diffusion path length (cm), and D is the diffusion coefficient of the analyte in air (cm 2 /min). Temperature Correction Temperature corrections are rarely needed as temperature has little effect on SR (10 ºC variation causes less than 5% difference). However, temperature corrected SR values for sampling at operating temperatures significantly different than 25 C can be calculated by: SR TX SR 298 TK 298 where: SRTX is sampling rate (ml/min) at the operating temperature ( K), SR298 is sampling rate (cm 3 /min) at 25 C (298 K) and TK is the operating temperature (K). More details on the temperature sensitivity of SPME TWA sampling can be found in below refernces. References for diffusive/air sampling with SPME 1. Anal. Chem. 2003, 75, Time-Weighted Average Passive Sampling with a Solid-Phase Microextraction Device (Yong Chen and Janusz Pawliszyn). 2. Journal of Chromatography A, 892 (2000) Time-weighted average sampling of volatile and semi-volatile airborne organic compounds by the solid-phase microextraction device (Abir Khaled, Janusz Pawliszyn). 3. Journal of Chromatography A, 1129 (2006) Diffusive sampling of airborne furfural by solid-phase microextraction device with on-fiber derivatization (Shih-Wei Tsai, Kuo-Yuan Kao). 4. Anal. Chem. 1999, 71, Time-Weighted Average Sampling with Solid -Phase Microextraction Device: Implications for Enhanced Personal Exposure Monitoring to Airborne Pollutants (Perry A. Martos and Janusz Pawliszyn)) 1,5 Use of Diffusive Sampling Fiber Holder (DFH) Fig. 1 shows the Chromline Diffusive Sampling Fiber Holder (TWA Sampler) for SPME that allows precise retraction of the fiber from 0 mm to 35 mm into the piercing needle. The DFH is used in combination with SPME Fast Fit Fiber Assembies (FFA, see page 7 for details). Before and after sampling the FFA, installed in the holder, is sealed by a PTFE sealing cup inserted into a spring loaded mechanism (sealing cap) to avoid contamination and sample loss. For sampling the sealing cap is removed. After sampling the cap is placed on the holder again and the whole holder is stored refrigirated. Alternatively a SPME Fig. 1 - Chromline DFH Holder. Page 5 FFA Storage Container for (57592-U) can be used to store the FFA before and after sampling by removing it from the sampler. During sampling, the fiber is retracted at a known length of Z and exposed for a defined time. Duration/exposure time and ambient temperature are recorded. To be able to set a defined and reproducible Z-value, the holder with the FFA must be Zeroed before setting a Z-value by adjusting the fiber in the holder (see chapter Zero and Setting of Z-Length ). After sampling the fiber is transferred to a laboratory and the amount of compound trapped is analyzed by GC by thermally desorbing it in the hot injector port. The desorption can be done manually (use of optional DFH manual desorption adapter Cat.# U) or automated using the Multi Fiber EXchanger (MFX)* for unattended desorption sequences of up to 25 samples (see page 17). To calculate the time weighted average concentration during the sampling period the following equation is used: m C SR t _ where: C is the average concentration (μg/m 3 ), m is the mass of the analyte desorbed from the fiber (μg), as determined by GC, SR is the sampling rate (ml/min) and t is the time (min). In Appendix Table 1 are SR values for a range of products listed. Also there is a formular given to estimate the SR for other compounds not listed. Temperature corrections are rarely needed as temperature has little effect on SR (10 ºC variation causes less than 5% difference). For extreme temperatures see the Appendix for corrections. * available from Gerstel GmbH & Co KG

6 DFH HOLDER PARTS Fig. 2 - DFH holder (Cat.# U). H6a H6b H6 Fig. 4 - Magnetic Plunger for Z-setting (Cat.# U). PTFE Sealing Cups & Needle Guide Fig. 5 - for 23ga blunt tip fibers one identification notch (Cat.# U). Fig. 7 - Stainless steel needle Guide. (Cat.# U). H2 H4 H1 Fig. 3 - DFH parts. H1- Holder Body H2- Holder Body Screw H3- Needle Protection Cage H4- Holder end cap H5- Sealing Unit H5 H6- Magnetic Plunger H6a- Plunger Screw H6b- Plunger Detach Screw (actuates magnetic center) Page 6 H3 Fig. 6 - for 24ga blunt tip fibers two identification notches (Cat.# U). Note: For diffusive sampling with SPME only blunt tipped fibers are suitable. Fibers with beveled tip are not suitable! Page 19 Compound CAS # Z3 SR theor. Z5 SR theor. Z10 SR theor. Z30 SR theor. (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) Ethyl acetate , , , , Ethyl ter-butyl ether (ETBE) , , , , Ethylbenzene , , , , Ethyltoluene , , , , Ethyltoluene , , , , Ethyltoluene , , , , n-heptane , , , , n-hexane , , , , Hexanol , , , , Isobutanol , , , , Isobutyl acetate , , , ,00212 Isooctane , , , , Isopropyl acetate , , , , Isopropyl ether , , , , p-isopropyltoluene , , , , Limonene , , , , Metanolo , , , , Methoxy 2-propanol , , , , Methoxy 2-propyl acetate , , , , Methoxyethanol , , , , Methyl methacrylate , , , , Methylacetate , , , , Methylcyclohexane , , , , Methylcyclopentane , , , , Methylethylketone , , , , Methylisobutylketone , , , , Methylpentane , , , , Methylpentane , , , , Metil-t-butiletere (MTBE) , , , , Metoxyethyl acetate , , , , Naphthalene , , , , n-nonane , , , , n-octane , , , , n-pentane , , , , Propanol , , , , Propyl acetate , , , , Propylbenzene , , , , Styrene , , , , ,1,1,2-Tetrachloroethane , , , , ,1,2,2-Tetrachloroethane , , , ,00219 Tetrachloroethylene , , , , Tetrahydrofuran , , , , Toluene , , , , ,1,1-Trichloroethane , , , , Trichloroethylene , , , , ,2,3-Trichloropropane , , , , ,2,4-Trimethylbenzene , , , , ,3,5-Trimethylbenzene , , , , n-undecane , , , , m-xylene , , , , o-xylene , , , , p-xylene , , , ,002266

7 APPENDIX TABLE 1 Theoretical SR Values at 25 C for a 23 ga 85 μm Carboxen/PDMS Fiber (Cat.# FFA57295-U). How to estimate SR values is described on page 20. Page 18 ACCESSORIES Page 7 Compound CAS # Z3 SR theor. Z5 SR theor. Z10 SR theor. Z30 SR theor. (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) (mm) (ml/min) Acetone , , , , Acetonitrile , , , , n-amyl acetate , , , , Tert-Amyl alcohol (TAA) , , , ,00236 Tert-Amyl methyl ether (TAME) , , , , Benzene , , , , Benzyl alcohol , , , , Bromobenzene , , , , Bromochloromethane , , , ,00284 Bromoform , , , , n-butanol , , , , sec-butanol , , , , tert-butanol , , , , Butoxyethanol , , , , n-butyl acetate , , , ,00212 tert-butyl acetate , , , ,00212 Butylbenzene , , , , Carbon tetrachloride , , , , Chlorobenzene , , , , Chloroform , , , , Chlorotoluene , , , , Chlorotoluene , , , , Cumene , , , , Cyclohexane , , , , Cyclohexanol , , , ,00219 Cyclohexanone , , , , n-decane , , , , Diacetone alcohol , , , , ,2-Dibromo-3- chloropropane , , , , Dibromochloromethane , , , , ,2-Dibromoethane , , , , Dibromomethane , , , , ,1-Dichloro-1-propene , , , , ,4-Dichlorobenzene , , , , ,2-Dichloroethane , , , ,00265 Dichloromethane , , , , ,2-Dichloropropane , , , , Diethyl ether , , , , N,N-Dimethylformamide , , , , ,4-Dioxan , , , , n-dodecane , , , , Ethanol , , , , Ethoxyethanol , , , , Ethoxyethyl acetate (EGEA) , , , , Ethyl 1-hexanol , , , , Fig. 8 Manual desorption adapter for DFH (Cat.# U). SPME FIBERS USED WITH DFH Fig. 9 Optional SPME-FFA Storage Container (Cat.# U) The DFH holder accepts only SPME Fast Fit Fiber Assemblies (FFA). The FFA are a configuration of SPME fibers allowing the automated exchange of SPME fibers by the Multi Fiber EXchange (MFX) system on a CTC CombiPAL type autosampler. For the most recent listing of products, please refer to sigma-aldrich.com/spme. Only fibers with blunt tips can be used for Fig. 10 SPME-FFA diffusive SPME sampling! Recommended for standard TWA sampling of VOCs: FFA57295-U PK3, 85 μm CAR/PDMS STABLEF. SPME Fast Fit Assembly 23 ga FFA57335-U PK3, 85 μm CAR/PDMS STABLEF. SPME Fast Fit Assembly 24 ga FFA Barcode Labeling Provides the user and the autosampler with following information about the properties of the SPME fast fit fiber assembly A. The color code indicates the phase type. The coding is the same as for the colored screw hub of the traditional SPME fiber assemblies B. Fiber ID: The first 2 digits of the barcode identify the fiber type, incorporating the phase and the gauge size. C. The remaining digits represent a unique tracking number for sample traceability.

8 PTFE CUP INSTALLATION & REPLACEMENT Page 8 Page 17 ANALYSIS: AUTOMATED DESORPTION WITH MFX The PTFE sealing cup (Part SC1) must match the gauge size of the needle in the used SPME Assembly. After 2-4 storage cycles it is recommended to replace the PTFE sealing cap to ensure maximum sealing efficiency. For highly concentrated samples an exchange after 1 cycle might be necessary. Data on PTFE sealing efficiency can be found in the Appendix. H5 H5 Fig. 52 Remove FFA from the holder (follow Fig in this manual in reverse order). Fig. 53 Insert the FFA fiber in the tray of MFX System. (25-Pos. Tray is shown, available also as 3 and 45- Pos. versions) Fig. 11 Unscrew & remove the Sealing Unit (part H5) from the DFH. Fig. 12 Close up of Sealing Unit (part H5) without PTFE sealing cap H5 SC1 SC2 H5 SC1 SC2 Fig Parts for assembling the sealing mechanism (H5, SC1* and SC2). * The PTFE sealing cup (part SC1) must match the type of needle on used SPME assembly (24 or 23 ga) used. PRESS Fig Assemble parts H5, SC1 and SC2 as shown above. Screw SC1 into H5 and press SC2 onto SC1. Fig. 54 The tray of the MFX System is equipped with special caps (SPME fiber saver) to preserve the fiber conditioning or loaded sample. MFX System Fig. 55 GERSTEL MPS autosampler with MFX option. Shown is a 3-position system. Available also as a 25-pos. system (Fig. 53 shows the tray) and a 45-position system on request. For more information on the Multi Fiber EXchanger System please refer to the Gerstel web site:

9 Page 16 Page 9 Fig. 49 Hand tighten the manual adapter. The holder is now ready for manual injection. Fig. 50 Inject into the GC injection port, making sure the holder does not tilt to prevent needle bending, and press the plunger completely down to expose the fiber in the injector. Fig The PTFE sealing cup is now properly installed. Fig Re-insert the sealing unit into the holder. Note: 5 cm Please refer to your GC instruments manual for the distance of the injector top to the hottest part of the injector block. The manual desorption adapter (Cat.No U) is designed for an injection depth of 5 cm. Fig Fingerthight sealing unit. Fig. 51 Detail of fiber being exposed when plunger is pushed down completely. Optional FFA Storage After sampling, the FFA can also removed from the DFH and be stored in an optional FFA Sorage container (Cat.# U)

10 Page 10 Page 15 SPME FFA INSTALLATION AFTER SAMPLING 1. Proceed in reverse order to those shown in Figures 43 to Record exposure time in your documentation. 3. Store sampler refrigerated for transport and until analysis. Fig. 18 Use conditioned SPME Fast Fit Fiber Assembly (FFA). H1 Fig Unscrew part H1 from holder body screw. Alternatively: 1. Remove the FFA from the sampler and place it in SPME-FFA Storage Container (Cat.# U, available as accessory) for transport 2. Record exposure time in your documentation. 3. Keep the store container refrigerated for transport and until analysis. ANALYSIS: MANUAL DESORPTION Fig Insert FFA with barcode end into the part H1. Fig. 21 Make sure the FFA is fully inserted into part H1. Fig. 45 Remove holder end cap. Fig. 46 Insert plunger into the holder. Make sure the magnetic center is in contact position (see detail). H3 H2 H1 Fig. 22 Carefully reinsert part H1 with FFA into holder body screw with attached sealing mechanism (part H2&H3) Fig. 23 Handtight holder body and part H1. The SPME FFA fiber is now in the holder. Fig. 47 Unscrew lower part of holder (Protection cage with sealing unit, parts H3&H5) Fig. 48 Attach the manual desorption adapter (Cat# U) onto the holder.

11 Page 14 Page 11 SAMPLING ZERO AND SETTING OF Z-LENGTH Adjusting the holder & fiber to zero for precise set up of diffusion path way- Z. Perform this operation in a clean environment. H5 H4 Fig. 40 Take the device and remove the sealing unit with the PTFE cup (H5) Fig. 41 The sampling now starts. During sampling sealing unit can be stored in the other end of holder. (b) H4 (a) Fig The plungers center is magnetic and will attach to the top of the FFA. Make sure that the magnetic center is adjusted like shown on the picture above. Adjustment is done by turning the plunger detach screw (part H6b) Fig Remove holder end cap (part H4). Fig. 42 Storing sealing unit during sampling: Take off holder end cap H4 (a) put it on the sealing cap indicated above too prevent loss of it (b). Fig. 43 Place the sealing unit into the rear end of the sampler. This safely stores the sealing cap and prevents contamination of the PTFE sealing cup. H1 H6a H6 Fig. 44 Leave the device opened during the time of sampling. Fig Insert DFH Magnetic Plunger (part H6 ) into upper part of DFH (H1 part) as shown above. fiber Fig Hand tight the plunger screw (part H6a). Connect the magnet center with the installed FFA by carefully sliding in the plunger

12 Page 12 Page 13 SETTING Z-LENGTH (Sampler sensitivity) Zero notch Fig. 28 Set plunger to zero position by moving part H6 to the last notch toward plunger middle (1) and lock it by sliding the pin (3) into the slot (2). Fig The zero of the graduated scale is aligned with the red index of the plunger. Fig. 34 Unlock the plunger from Zero position to be able to set the Z-value by sliding the plunger Fig. 35 Slide the plunger (H6) out of the holder to adjust the value of Z. Each plunger notch corresponds to 5 mm increment of the Z-length. Example of positioning Z = 15 mm H6b 1 Fig. 30 Remove the sealing unit to adjust the zero of the FFA fiber. Fiber Fig. 31 Without unlocking the plunger turn part 1 by holding the sampler with the other hand on the holder body. Observe fiber needle opening (Fig. 32). Fig. 36 In principle any value between 0 and 35mm can be adjusted. Record the setting. Fig. 37 Detach the magnetic center from the FFA by turning the plunger detach screw (part H6b) (make sure NOT to change Z!). Plunger & FFA are now disconnected In Line Needle H6a H4 Fig. 32 The zero setting is reached when SPME fiber tip is positioned level with the opening of the needle. Fig. 33 Re-insert sealing unit to seal the fiber. Fig Remove the plunger by unscrewing part H6a and place the holder end cap (H4) onto the holder. Fig. 39 The holder is now ready for transport to the sampling site.