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- Reference Material on InstrumentationArticle - A High Temperature Direct Probe for a Mass Spectrometer Design of a Direct Exposure Probe and Controller for use ona Hewlett-Packard 5989 Mass Spectrometer SIS AP1000 AutoProbe™ SIS AP2000 AutoProbe™ - Description of System HPP7: Direct Probe Electronics Console HPP7: Direct Probe for the Agilent (HP) 5973/5975 MSD HPP7: HP Direct Probe Application Notes HPP7: Installation Directions for the Direct Probe HPP7: Side Cover for the HP 5973 MSD HPP7: Support HPP7: Probe Inlet System for the Agilent (HP) 5973 and 5975 MSD with Automatic Indexed Stops HPP7: Theory of Operation of the Direct Probe and Probe Inlet System Direct Thermal Extraction Thermal Desorption Application Notes Environmental Thermal Desorption Application Notes Food Science Thermal Desorption Application Notes Forensic Thermal Desorption Application Notes GC Cryo-Trap Application Notes Headspace Application Notes Purge & Trap Thermal Desorption Application Notes Theory of Operation of the AutoDesorb® System AutoDesorb Notes for SIS Dealers Adsorbent Resin Application Notes Installation of the Short Path Thermal Desorption System on Agilent (HP) and Other GCs Installation of the Short Path Thermal Desorption System on a Varian 3400 GC AutoDesorb® System Development Team Thermal Desorption Applications and Reference Materials Installation of the Short Path Thermal Desorption System - TD5 Part I - Design & Operation of the Short Path ThermalDesorption System Installation Instructions for the Model 951 GC Cryo-Trap on the HP 5890 Series GC Installation Instructions for the Model 961 GC Cryo-Trap on the HP 5890 Series GC Operation of the Model 951/961 GC Cryo-Trap SIS GC Cryo Traps - Theory of Operation NIST/EPA/NIH Mass Spectral Enhancements - 1998 version (NIST98) SIMION 3D Ion Optics Class Mass Spectrometer Source Cleaning Methods MS Tip: Mass Spectrometer Source Cleaning Procedures Mass Spec Source Cleaning Procedures Micro-Mesh® Abrasive Sheets Research Papers Using New Era Syringe Pump Systems EI Positive Ion Spectra for Perfluorokerosene (PFK) Cap Liner Information How do I convert between fluid oz and milliliters? Which bottle material should I choose? Which bottle mouth should I choose? The Bottle Selection Guide CGA Connections for Gas Tanks Chemical Reaction Interface Mass Spectrometry (CRIMS)
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- AccessoriesTD Supply Kit Desorption Tubes Adsorbent Resins Desorption Tube Needles Desorption Tube Seals Desorption System Fittings GC Cryo-Trap Extraction Cell TD Sample Loader Prepacked, Conditioned Desorption Tubes Desorption Tube Packing Accessories Stainless Steel Purge Heads Injection Port Liners Tenax TA Poster TD Application Notes Customer Service
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- Thermal Desorption Applications and Reference MaterialsDirect Thermal Extraction Headspace Environmental Food Science Applications Pharmaceuticals Forensic Note 103: EPA Method 325B, Novel Thermal Desorption Instrument Modification to Improve Sensitivity Note 102: Identification of Contaminants in Powdered Beverages by Direct Extraction Thermal Desorption GC/MS Note 101: Identification of Contaminants in Powdered Foods by Direct Extraction Thermal Desorption GC/MS Note 100: Volatile and Semi-Volatile Profile Comparison of Whole Versus Cracked Versus Dry Homogenized Barley Grains by Direct Thermal Extraction Note 99: Volatile and Semi-Volatile Profile Comparison of Whole vs. Dry Homogenized Wheat, Rye and Barley Grains by Direct Thermal Extraction GC/MS Note 98: Flavor and Aroma Profiles of Truffle Oils by Thermal Desorption GC/MS Note 97: Flavor Profiles of Imported and Domestic Beers by Purge & Trap Thermal Desorption GC/MS Note 95: Detection of Explosives on Clothing Material by Direct and AirSampling Thermal Desorption GC/MS Note 94: Detection of Nepetalactone in the Nepeta Cataria Plant by Thermal Desorption GC/MS Note 93: Detection of Benzene in Carbonated Beverages with Purge & Trap Thermal Desorption GC/MS Note 88: Analysis of Silicone Contaminants on Electronic Components by Thermal Desorption GC-MS Note 84: Vacuum Pump Exhaust Filters - Charcoal Exhaust Traps Note 83: Vacuum Pump Exhaust Filters - Oil Mist Eliminators Note 82: Vacuum Pump Exhaust Filters Note 80: Design, Development and Testing of a Microprocessor ControlledAutomated Short Path Thermal Desorption Apparatus Note 79: Volatile Organic Compounds From Electron Beam Cured and Partially Electron Beam Cured Packaging Using Automated Short Path Thermal Desorption Note 77: The Determination of Volatile Organic Compounds in VacuumSystem Components Note 75: An Apparatus for Sampling Volatile Organics From LivePlant Material Using Short Path Thermal Desorption Note 73: The Analysis of Perfumes and their Effect on Indoor Air Pollution Note 71: Flavor Profile Determination of Rice Samples Using Shor tPath Thermal Desorption GC Methods Note 65: Determination of Ethylene by Adsorbent Trapping and Thermal Desorption - Gas Chromatography Note 64: Comparison of Various GC/MS Techniques For the Analysis of Black Pepper (Piper Nigrum) Note 63: Determination of Volatile and Semi-Volatile Organics in Printer Toners Using Thermal Desorption GC Techniques Note 60: Programmable Temperature Ramping of Samples Analyzed ViaDirect Thermal Extraction GC/MS Note 57: Aroma Profiles of Lavandula species Note 55: Seasonal Variation in Flower Volatiles Note 54: Identification of Volatile Organic Compounds in Office Products Note 43: Volatile Organic Composition In Blueberries Note 42: The Influence of Pump Oil Purity on Roughing Pumps Note 41: Hydrocarbon Production in Pine by Direct Thermal Extraction Note 40: Comparison of Septa by Direct Thermal Extraction Note 39: Comparison of Sensitivity Of Headspace GC, Purge and Trap Thermal Desorption and Direct Thermal Extraction Techniques For Volatile Organics Note 38: A New Micro Cryo-Trap For Trapping Of Volatiles At the Front Of a GC Capillary Column Note 37: Volatile Organic Emissions from Automobile Tires Note 36: Identification Of Volatile Organic Compounds In a New Automobile Note 35: Volatile Organics Composition of Cranberries Note 34: Selection Of Thermal Desorption and Cryo-Trap Parameters In the Analysis Of Teas Note 33: Changes in Volatile Organic Composition in Milk Over Time Note 32: Selection and Use of Adsorbent Resins for Purge and Trap Thermal Desorption Applications Note 31: Volatile Organic Composition in Several Cultivars of Peaches Note 30: Comparison Of Cooking Oils By Direct Thermal Extraction and Purge and Trap GC/MS Note 29: Analysis Of Volatile Organics In Oil Base Paints By Automated Headspace Sampling and GC Cryo-Focusing Note 28: Analysis Of Volatile Organics In Latex Paints By Automated Headspace Sampling and GC Cryo-Focusing Note 27: Analysis of Volatile Organics In Soils By Automated Headspace GC Note 26: Volatile Organics Present in Recycled Air Aboard a Commercial Airliner Note 25: Flavor and Aroma in Natural Bee Honey Note 24: Selection of GC Guard Columns For Use With the GC Cryo-Trap Note 23: Frangrance Qualities in Colognes Note 22: Comparison Of Volatile Compounds In Latex Paints Note 21: Detection and Identification Of Volatile and Semi-Volatile Organics In Synthetic Polymers Used In Food and Pharmaceutical Packaging Note 20: Using Direct Thermal Desorption to Assess the Potential Pool of Styrene and 4-Phenylcyclohexene In Latex-Backed Carpets Note 19: A New Programmable Cryo-Cooling/Heating Trap for the Cryo-Focusing of Volatiles and Semi-Volatiles at the Head of GC Capillary Columns Note 18: Determination of Volatile Organic Compounds In Mushrooms Note 17: Identification of Volatile Organics in Wines Over Time Note 16: Analysis of Indoor Air and Sources of Indoor Air Contamination by Thermal Desorption Note 14: Identification of Volatiles and Semi-Volatiles In Carbonated Colas Note 13: Identification and Quantification of Semi-Volatiles In Soil Using Direct Thermal Desorption Note 12: Identification of the Volatile and Semi-Volatile Organics In Chewing Gums By Direct Thermal Desorption Note 11: Flavor/Fragrance Profiles of Instant and Ground Coffees By Short Path Thermal Desorption Note 10: Quantification of Naphthalene In a Contaminated Pharmaceutical Product By Short Path Thermal Desorption Note 9: Methodologies For the Quantification Of Purge and Trap Thermal Desorption and Direct Thermal Desorption Analyses Note 8: Detection of Volatile Organic Compounds In Liquids Utilizing the Short Path Thermal Desorption System Note 7: Chemical Residue Analysis of Pharmaceuticals Using The Short Path Thermal Desorption System Note 6: Direct Thermal Analysis of Plastic Food Wraps Using the Short Path Thermal Desorption System Note 5: Direct Thermal Analysis Using the Short Path Thermal Desorption System Note 4: Direct Analysis of Spices and Coffee Note 3: Indoor Air Pollution Note 2: Detection of Arson Accelerants Using Dynamic Headspace with Tenax® Cartridges Thermal Desorption and Cryofocusing Note 1: Determination of Off-Odors and Other Volatile Organics In Food Packaging Films By Direct Thermal Analysis-GC-MS
- Application NotesNote 103: EPA Method 325B, Novel Thermal Desorption Instrument Modification to Improve Sensitivity Note 102: Identification of Contaminants in Powdered Beverages by Direct Extraction Thermal Desorption GC/MS Note 101: Identification of Contaminants in Powdered Foods by Direct Extraction Thermal Desorption GC/MS Note 100: Volatile and Semi-Volatile Profile Comparison of Whole Versus Cracked Versus Dry Homogenized Barley Grains by Direct Thermal Extraction Note 99: Volatile and Semi-Volatile Profile Comparison of Whole vs. Dry Homogenized Wheat, Rye and Barley Grains by Direct Thermal Extraction GC/MS Note 98: Flavor and Aroma Profiles of Truffle Oils by Thermal Desorption GC/MS Note 97: Flavor Profiles of Imported and Domestic Beers by Purge & Trap Thermal Desorption GC/MS Note 96: Reducing Warping in Mass Spectrometer Filaments, with SISAlloy® Yttria/Rhenium Filaments Note 95: Detection of Explosives on Clothing Material by Direct and AirSampling Thermal Desorption GC/MS Note 94: Detection of Nepetalactone in the Nepeta Cataria Plant by Thermal Desorption GC/MS Note 93: Detection of Benzene in Carbonated Beverages with Purge & Trap Thermal Desorption GC/MS Note 92: Yttria Coated Mass Spectrometer Filaments Note 91: AutoProbe DEP Probe Tip Temperatures Note 90: An Automated MS Direct Probe for use in an Open Access Environment Note 89: Quantitation of Organics via a Mass Spectrometer Automated Direct Probe Note 88: Analysis of Silicone Contaminants on Electronic Components by Thermal Desorption GC-MS Note 87: Design and Development of an Automated Direct Probe for a Mass Spectrometer Note 86: Simulation of a Unique Cylindrical Quadrupole Mass Analyzer Using SIMION 7.0. Note 85: Replacing an Electron Multiplier in the Agilent (HP) 5973 MSD Note 84: Vacuum Pump Exhaust Filters - Charcoal Exhaust Traps Note 83: Vacuum Pump Exhaust Filters - Oil Mist Eliminators Note 82: Vacuum Pump Exhaust Filters Note 81: Rapid Bacterial Chemotaxonomy By DirectProbe/MSD Note 80: Design, Development and Testing of a Microprocessor ControlledAutomated Short Path Thermal Desorption Apparatus Note 79: Volatile Organic Compounds From Electron Beam Cured and Partially Electron Beam Cured Packaging Using Automated Short Path Thermal Desorption Note 78: A New Solution to Eliminate MS Down-Time With No-Tool-Changing of Analytical GC Columns Note 77: The Determination of Volatile Organic Compounds in VacuumSystem Components Note 76: Determination of the Sensitivity of a CRIMS System Note 75: An Apparatus for Sampling Volatile Organics From LivePlant Material Using Short Path Thermal Desorption Note 74: Examination of Source Design in Electrospray-TOF Using SIMION 3D Note 73: The Analysis of Perfumes and their Effect on Indoor Air Pollution Note 72: 1998 Version of the NIST/EPA/NIH Mass Spectral Library, NIST98 Note 71: Flavor Profile Determination of Rice Samples Using Shor tPath Thermal Desorption GC Methods Note 70: Application of SIMION 6.0 To a Study of the Finkelstein Ion Source: Part II Note 69: Application of SIMION 6.0 To a Study of the Finkelstein Ion Source: Part 1 Note 68: Use of a PC Plug-In UV-Vis Spectrometer To Monitor the Plasma Conditions In GC-CRIMS Note 67: Using Chemical Reaction Interface Mass Spectrometry (CRIMS) To Monitor Bacterial Transport In In Situ Bioremediation Note 66: Probe Tip Design For the Optimization of Direct Insertion Probe Performance Note 65: Determination of Ethylene by Adsorbent Trapping and Thermal Desorption - Gas Chromatography Note 64: Comparison of Various GC/MS Techniques For the Analysis of Black Pepper (Piper Nigrum) Note 63: Determination of Volatile and Semi-Volatile Organics in Printer Toners Using Thermal Desorption GC Techniques Note 62: Analysis of Polymer Samples Using a Direct Insertion Probe and EI Ionization Note 61: Analysis of Sugars Via a New DEP Probe Tip For Use With theDirect Probe On the HP5973 MSD Note 60: Programmable Temperature Ramping of Samples Analyzed ViaDirect Thermal Extraction GC/MS Note 59: Computer Modeling of a TOF Reflectron With Gridless Reflector Using SIMION 3D Note 58: Direct Probe Analysis and Identification of Multicomponent Pharmaceutical Samples via Electron Impact MS Note 57: Aroma Profiles of Lavandula species Note 56: Mass Spec Maintenance & Cleaning Utilizing Micro-Mesh® Abrasive Sheets Note 55: Seasonal Variation in Flower Volatiles Note 54: Identification of Volatile Organic Compounds in Office Products Note 53: SIMION 3D v6.0 Ion Optics Simulation Software Note 52: Computer Modeling of Ion Optics in Time-of-Flight mass Spectrometry Using SIMION 3D Note 51: Development and Characterization of a New Chemical Reaction Interface for the Detection of Nonradioisotopically Labeled Analytes Using Mass Spectrometry (CRIMS) Note 50: The Analysis of Multiple Component Drug Samples Using a Direct Probe Interfaced to the HP 5973 MSD Note 49: Analysis of Cocaine Utilizing a New Direct Insertion Probe on a Hewlett Packard 5973 MSD Note 48: Demonstration of Sensitivity Levels For the Detection of Caffeine Using a New Direct Probe and Inlet for the HP 5973 MSD Note 47: The Application Of SIMION 6.0 To Problems In Time-of-Flight Mass Spectrometry Note 46: Delayed Extraction and Laser Desorption: Time-lag Focusing and Beyond Note 45: Application of SIMION 6.0 to Filament Design for Mass Spectrometer Ionization Sources Note 44: The Design Of a New Direct Probe Inlet For a Mass Spectrometer Note 43: Volatile Organic Composition In Blueberries Note 42: The Influence of Pump Oil Purity on Roughing Pumps Note 41: Hydrocarbon Production in Pine by Direct Thermal Extraction Note 40: Comparison of Septa by Direct Thermal Extraction Note 39: Comparison of Sensitivity Of Headspace GC, Purge and Trap Thermal Desorption and Direct Thermal Extraction Techniques For Volatile Organics Note 38: A New Micro Cryo-Trap For Trapping Of Volatiles At the Front Of a GC Capillary Column Note 37: Volatile Organic Emissions from Automobile Tires Note 36: Identification Of Volatile Organic Compounds In a New Automobile Note 35: Volatile Organics Composition of Cranberries Note 34: Selection Of Thermal Desorption and Cryo-Trap Parameters In the Analysis Of Teas Note 33: Changes in Volatile Organic Composition in Milk Over Time Note 32: Selection and Use of Adsorbent Resins for Purge and Trap Thermal Desorption Applications Note 31: Volatile Organic Composition in Several Cultivars of Peaches Note 30: Comparison Of Cooking Oils By Direct Thermal Extraction and Purge and Trap GC/MS Note 29: Analysis Of Volatile Organics In Oil Base Paints By Automated Headspace Sampling and GC Cryo-Focusing Note 28: Analysis Of Volatile Organics In Latex Paints By Automated Headspace Sampling and GC Cryo-Focusing Note 27: Analysis of Volatile Organics In Soils By Automated Headspace GC Note 26: Volatile Organics Present in Recycled Air Aboard a Commercial Airliner Note 25: Flavor and Aroma in Natural Bee Honey Note 24: Selection of GC Guard Columns For Use With the GC Cryo-Trap Note 23: Frangrance Qualities in Colognes Note 22: Comparison Of Volatile Compounds In Latex Paints Note 21: Detection and Identification Of Volatile and Semi-Volatile Organics In Synthetic Polymers Used In Food and Pharmaceutical Packaging Note 20: Using Direct Thermal Desorption to Assess the Potential Pool of Styrene and 4-Phenylcyclohexene In Latex-Backed Carpets Note 19: A New Programmable Cryo-Cooling/Heating Trap for the Cryo-Focusing of Volatiles and Semi-Volatiles at the Head of GC Capillary Columns Note 18: Determination of Volatile Organic Compounds In Mushrooms Note 17: Identification of Volatile Organics in Wines Over Time Note 16: Analysis of Indoor Air and Sources of Indoor Air Contamination by Thermal Desorption Note 14: Identification of Volatiles and Semi-Volatiles In Carbonated Colas Note 13: Identification and Quantification of Semi-Volatiles In Soil Using Direct Thermal Desorption Note 12: Identification of the Volatile and Semi-Volatile Organics In Chewing Gums By Direct Thermal Desorption Note 11: Flavor/Fragrance Profiles of Instant and Ground Coffees By Short Path Thermal Desorption Note 10: Quantification of Naphthalene In a Contaminated Pharmaceutical Product By Short Path Thermal Desorption Note 9: Methodologies For the Quantification Of Purge and Trap Thermal Desorption and Direct Thermal Desorption Analyses Note 8: Detection of Volatile Organic Compounds In Liquids Utilizing the Short Path Thermal Desorption System Note 7: Chemical Residue Analysis of Pharmaceuticals Using The Short Path Thermal Desorption System Note 6: Direct Thermal Analysis of Plastic Food Wraps Using the Short Path Thermal Desorption System Note 5: Direct Thermal Analysis Using the Short Path Thermal Desorption System Note 4: Direct Analysis of Spices and Coffee Note 3: Indoor Air Pollution Note 2: Detection of Arson Accelerants Using Dynamic Headspace with Tenax® Cartridges Thermal Desorption and Cryofocusing Note 1: Determination of Off-Odors and Other Volatile Organics In Food Packaging Films By Direct Thermal Analysis-GC-MS Tech No. "A" Note 14: Elimination of "Memory" Peaks in Thermal Desorption Improving Sensitivity in the H.P. 5971 MSD and Other Mass Spectrometers - Part I of II Improving Sensitivity in the H.P. 5971 MSD and Other Mass Spectrometers- Part II of II Adsorbent Resins Guide Development and Field Tests of an Automated Pyrolysis Insert for Gas Chromatography. Hydrocarbon Production in Pine by Direct Thermal Extraction A New Micro Cryo-Trap for the Trapping of Volatiles at the Front of a GC Capillary (019P) - Comparison of Septa by Direct Thermal Extraction Volatile Organic Composition in Blueberry Identification of Volatile Organic Compounds in Office Products Detection and Indentification of Volatiles in Oil Base Paintsby Headspace GC with On Column Cryo-Trapping Evaluation of Septa Using a Direct Thermal Extraction Technique INFLUENCE OF STORAGE ON BLUEBERRY VOLATILES Selection of Thermal Desorption and Cryo-Trap Parameters in the Analysis of Teas Redesign and Performance of a Diffusion Based Solvent Removal Interface for LC/MS The Design of a New Direct Probe Inlet for a Mass Spectrometer Analytes Using Mass Spectrometry (CRIMS) Application of SIMION 6.0 to Filament Design for Mass Spectrometer Ionization Sources A Student Guide for SIMION Modeling Software Application of SIMION 6.0 to Problems in Time-of-flight Mass Spectrometry Comparison of Sensitivity of Headspace GC, Purge and TrapThermal Desorption and Direct Thermal Extraction Techniques forVolatile Organics The Influence of Pump Oil Purity on Roughing Pumps Analysis of Motor Oils Using Thermal Desorption-Gas Chromatography-Mass Spectrometry IDENTIFICATION OF VOLATILE ORGANIC COMPOUNDS IN PAPER PRODUCTS Computer Modeling of Ion Optics in Time-of-Flight mass Spectrometry using SIMION 3D Seasonal Variation in Flower Volatiles Development of and Automated Microprocessor Controlled Gas chromatograph Fraction Collector / Olfactometer Delayed Extraction and Laser Desorption: Time-lag Focusing and Beyond A New Micro Cryo-Trap for the Trapping of Volatiles at the Front of a GC Column Design of a Microprocessor Controlled Short Path Thermal Desorption Autosampler Computer Modeling of Ion Optics in Time-of-Flight Mass Spectrometry Using SIMION 3D Thermal Desorption Instrumentation for Characterization of Odors and Flavors
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- Note 64: Comparison of Various GC/MS Techniques For the Analysis of Black Pepper (Piper Nigrum) (This Page)
Presented at PittCon 98, March 1998, New Orleans,
LA
ABSTRACT
A large number of volatile and semi-volatile organic compounds are present in black pepper, which are responsible for its unique odor and flavor. These compounds include aromatics, hydrocarbons, terpenes and sesquiterpenes. In order to analyze and identify these compounds, a variety of extraction and sample introduction techniques are utilized for preparation of the sample for gas chromatographic separation of the analytes and for identification via a mass spectrometer. The purpose of this paper is to study four different GC introduction techniques and a direct mass spec technique, including (1) solvent extraction, (2) direct probe mass spectrometry, (3) direct thermal extraction (DTE), (4) dynamic headspace and (5) solid phase micro extraction (SPME). Each technique has its own advantages and disadvantages. In this study, each technique was used to analyze a sample of black pepper to compare the ease and speed of each technique, the relative sensitivity of each method and the range of volatile and semi-volatile organic compounds extracted by each method. The purpose is to develop an understanding of each technique in order to aid the selection of an appropriate method for the analysis of other samples of volatile and semi-volatile organics. Collectively, the five techniques identified more than 100 analytes in black pepper. However, the sample size required for each technique varied, as well as the range of light volatiles and semi-volatile organic compounds detected. The direct probe mass spec technique proved to be the least specific of the methods, identifying only piperine, the major alkaloid in black pepper. The greatest sensitivity with black pepper was achieved with the solvent extraction. Purge & Trap proved the least sensitive. The DTE had the shortest preparation time-over five minutes. |
INTRODUCTION
A large number of volatile and semi-volatile organic compounds including aromatics, hydrocarbons, terpines and sesquiterpines are responsible for the unique odor and flavor of black pepper. There is a variety of extraction and GC sample introduction techniques for the separation and mass spectrometer identification of these analytes.
The purpose of this paper is to study four different GC/MS sample introduction techniques and one direct probe mass spec technique for the analysis of volatile and semi-volatile analytes present in black pepper. The techniques studied include: (1) solvent extraction, (2) dynamic headspace (P&T), (3) direct thermal extraction (DTE), (4) solid phase micro extraction (SPME) and (5) direct probe mass spectrometry. Each of these techniques has its own advantages and disadvantages. Therefore, each technique was evaluated in order to compare the equipment needed for analysis, speed of analysis, relative sensitivity, and range of volatile and semi-volatile organic compounds extracted. This study will help develop an understanding of each technique in order that chemists can select an appropriate method for the analysis and identification of the volatile and semi-volatile organics present in black pepper, as well as in other food samples.
EXPERIMENTAL
Materials
A sample of commercial black peppercorns was finely ground in a micro-mill for 5 minutes. This homogeneous mixture was used for all studies.
Gas Chromatograph/Mass Spectrometer Combination
The techniques (#1-4) utilized a HP 5890 Series II GC with Electronic Pressure Control, interfaced to a HP 5989 Mass Spectrometer. The GC injection port temperature was at 250 °C and the GC/MS transfer line was at 250 °C. A SGE BPX35, 0.25mm x 0.25µ x 60m GC capillary column was programmed with an initial temp of 30 °C for 5 min, a 6 °C min-1 ramp to 260 °C and a final temp of 260 °C for 5 min. Carrier gas flow was 0.90 ml per min of He. The HP 5989 MS operated in Electron Impact Mode (EI), with a mass range of 35 to 450 Daltons. The direct probe technique was conducted on a HP 5973 MSD with the SIS direct sample probe attachment.
Thermal Desorption System
The Scientific Instrument Services Short Path Thermal Desorption System (SPTD), Model TD3, was used for both the direct thermal extraction technique and the purge & trap techniques (techniques #2 and #3).
GC Micro Cryo Trap
A Scientific Instrument Services Model 951 GC Micro Cryo-Trap was placed at the front of the GC column in order to improve GC peak resolution. During the injection phase, the cryo-trap uses liquid CO2 to freeze the analytes at the front of the GC column at -70 °C. After injection was complete the cryo-trap was heated to 250 °C to release the analytes for analysis.
1. CHCl3 Solvent Extraction
Thirty (30.0) mg of black pepper was suspended in 4.0 ml of chloroform and shaken for 10 minutes. It was then filtered and the residue was extracted with an additional 4ml of chloroform. The combined filtrate was evaporated to 5.0 µL, and 0.5 µL was injected into the GC. This is equivalent to the analysis of 3.0 mg of black pepper.
2. Dynamic Headspace - Purge & Trap
The SIS Purge and Trap System was used in conjunction with the SPTD for the Purge & Trap technique. Black pepper (3.1 mg) and glass distilled water (5.0 mL) was put in a 25 mL P&T tube and connected to the Purge & Trap apparatus. The P&T tube was placed into a water bath maintained at 92 °C. Sample desorption tubes were packed with 150 mg Tenax® TA Resin for analyte trapping and attached to the P&T apparatus. The sample was purged with helium for 30 minutes at 40 ml per min and the analytes trapped on the desorption tube. An additional 40 ml per min dry purge was used during sample collection to eliminate the condensation of water on the adsorbent trap. After the P&T was complete, the desorption tube was purged with an additional 40 ml He to remove all water content. The Tenax desorption tube was then placed into the SPTD and thermally desorpted into the GC at 250 °C for 5 min. The analytes were cryo-focused at the front of the column and subsequently released and analyzed via the mass spectrometer.
3. Direct Thermal Extraction (DTE)
For the DTE technique, 3.2 mg of the pepper sample was placed on top of a glass wool plug in a 3.0 mm I.D. thermal desorption tube. The tube was purged with Helium for 20 sec, injected into the GC and thermally extracted for 5 min at 250 °C. The extracted analytes were cryo-focused at the front of the GC column. Afterward, the trapped volatiles were released and analyzed via the GC/MS system. Additional studies were conducted on the black pepper samples at several different extraction temperatures between 100 and 350 °C and also via a temperature programmed thermal extraction. These results were used to optimize the DTE system temperature parameters.
4. Solid Phase Micro Extraction (SPME)
A SuplecoTM Solid Phase Microextraction Assembly was used for the Solid Phase Microextraction (SPME) technique, with a 100 µm thick, Polydimethylsiloxane (PDMS) stationary phase. Black pepper (3.1 mg) was mixed with 5.0 mL water in a head space vial and capped. The mixture was heated to about 90 °C and allowed to sit for 30 min with the SPME fiber exposed to the liquid mixture in the sample vial. The SPME fiber was then injected into the GC injection port, thermally desorbed in the GC injection port for 5.00 minutes, and cryo-focused at the front of the GC column for subsequent analysis.
5. MS Direct Probe
For sample preparation, 2.6 mg of black pepper was suspended in 1.0 ml chloroform and shaken for 5 minutes. Then, 0.5 µL of solution was injected into the direct probe sample vial, the glass sample vial was inserted into the direct probe and the direct probe then inserted into the HP 5973 MSD. The direct probe was ballistically heated to 350 °C, and the mass spectrometer was scanned from 35 to 500 Daltons.
RESULTS
Utilizing the various techniques, more than 100 peaks were found in the GC chromatograms of the black pepper. Compounds identified via the HP ChemStation software included a large number of hydrocarbons, aromatics, terpenes and sesquiterpenes. These included piperine (the major aromatic compound present in black pepper), linalool, alpha- and beta-pinene, myrcene, 3-carene, limonene, and alpha- and beta-caryophyllene. These analytes identified were corroborated by the CRC Handbook of Medical Herbs. Each of the sample preparation and GC injection techniques was compared for its ability to detect these analytes, as well as its relative sensitivity. Figure 1 shows the relative sensitivity of the four GC/MS techniques. The total ion chromatograms have been adjusted for the same sample size and the same sensitivity scale.
Figure 1.
Solvent Extraction
Solvent extraction has historically been the method of choice for the analysis of analytes in food samples. In this study the solvent extraction technique proved to be the most sensitive of the extraction methods. It also yielded the largest number of analytes (Figure 1). This technique does not discriminate based on analyte volatility, as the other techniques do. However, it can discriminate based on the solvent analyte solubility. This latter effect was not seen in this sample. In this technique the very light volatiles can be lost during sample preparation and sample concentration. This technique produced a large number of semi-volatile and non-volatile analytes that were not detected via the other techniques. Other disadvantages of this technique include the exposure of laboratory staff to the hazardous chloroform solvent and the cost of solvent disposal.
Dynamic Headspace
Purge & Trap was the least sensitive of the techniques studied (Figure 1). However, it did yield lower molecular weight (lower boiling point) analytes that were not detected in the other techniques (Figure 4). Static headspace techniques have also been used for the analysis of the very volatile analytes in black pepper and other samples. However, our previous studies have proven that static headspace is even less sensitive than dynamic headspace (P&T) and will not detect any of the higher boiling compounds or semi-volatile organics.
Figure 2.
Direct Thermal Extraction
The Direct Thermal Extraction technique is a preferred technique because it requires no sample preparation or extraction. The solid matrix sample is just placed directly into the thermal desorption tube and the analytes are thermally exacted from the sample. The DTE technique yielded a high abundance of volatile and semi-volatile organics, though slightly less than that achieved with solvent extraction (Figure 1). In a second study of this technique, several samples of black pepper were thermally extracted at temperatures from 100 to 350 °C (Figure 2). Higher molecular weight compounds did not begin to appear until the thermal extraction temperature was raised above 300 ºC. However, at this high temperature, some sample decomposition did occur. In a third study, the black pepper sample was analyzed via a temperature programmed thermal extraction from 100 to 250 °C (Figure 3). Utilizing the temperature programmed mode, it was expected that less sample decomposition would occur. In addition, several higher molecular weight analytes were detected, including a trace of peperine at 49.50 min.
Figure 3.
SPME
SPME is a low-cost sample preparation technique that yielded fairly good results. However, the technique was less sensitive than the DTE and solvent extraction techniques (Figure 1). Historically, SPME has been less suitable for the analysis of the more volatile analytes; however, new fiber coatings have appeared recently that improve the detection of the low molecular weight analytes. The SPME technique detected a few peaks in the higher-mass range that were only detectable in the temperature programmed DTE and the solvent extraction techniques (Figure 4).
Figure 4.
Direct Probe
The direct probe technique is normally a poor choice for the analysis of complex mixtures of anlaytes in foods, because it does not offer the ability to separate or resolve the multiple analytes present in these samples. However, this technique can prove useful if a sample contains only one or two analytes that are significantly higher in concentration than other analytes in the sample. This technique has the advantage that it is quick (1 to 3 minutes). The literature reports that piperine is the major flavor component in black pepper. However, piperine was not detected in any of the other techniques, except the DTE temperature programmed technique, either due to piperine's high boiling point or solubility. The direct probe was the only technique that successfully identified piperene in black pepper (Figure 5). This is due to its high concentration relative to the other analytes present.
Figure 5
CONCLUSION
No one anlytical method is optimal in all instances. There are a large number of factors that need to be considered in the selection of an anlaytical method. These factors include the physical properties of the sample, the sample matrix, the number of analytes of interest present in the sample, interfering compounds, the thermal stability of the sample, the cost and range of the equipment available, and the cost and time of the analysis.
Of the five techniques studied for black pepper, solvent extraction was the most sensitive technique, with the DTE technique the next most sensitive technique. The P&T technique was the least sensitive technique. The DTE and P&T techniques proved effective in the detection of the lowest boiling analytes. Static headspace is a good technique for the detection of the very volatile analytes. However, this technique cannot detect the less volatile and semi-volatile organics. The solvent extraction technique was the best method for the detection of the semi-volatile and non-volatile analytes. It was also the least costly in terms of additional hardware required. SPME was a good low-cost method for the analysis of many volatile and semi-volatile analytes, but it was less sensitive than the DTE and solvent extraction techniques. The MS direct probe technique was useful for the analysis of the piperine in black pepper and can also be used for the quick analysis of other samples.