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- 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
- Note 72: 1998 Version of the NIST/EPA/NIH Mass Spectral Library, NIST98 (This Page)
By O. David Sparkman
Expanded for Quality. Evaluated for Quality
Figure 1. The NIST Mass Spectral Search Program with all seven of its Windows displayed. Added Features for Quality
Prior to 1998, it had been six years since NIST released its last version of the NIST/EPA/NIH Mass Spectral Library. During that period, NIST has completed a ten-year project to completely evaluate the Library. As this process progressed, NIST was able to generate a number of spectra and acquire several important collections of quality spectra. This has allowed the Library to increase in size to 129,136 spectra of 107,886 compounds. This is a 75% increase in coverage. All but 57 of the compounds have an associated structure.
In an effort to develop the Library that has been optimized for the identification of unknown compounds through their mass spectra, NIST undertook a program, using experienced mass spectrometrists, where complete-as-possible spectra were evaluated for the presence or absence of peaks based on the structure, empirical formula, and molecular weight of a compound. In the event that anomalies were found,
Figure 2. MS Interpreter- a tool within the NIST MS Search Program that allows for a number of different functions including the ability to calculate the distance between peaks and determine if mass spectral peaks are logical based on an associated structure.
decisions as to what should be done with a spectrum (delete from the Library, remeasure (always, where possible), or remove contaminant peaks) were reached and agreed to by two of these mass spectrometrists. This process has led to thousands of selections, deletions, and modifications to produce this optimal Library. The process of the development of the Library has been described in numerous presentations at the American Society for Mass Spectrometry meetings over the past few years.1,2,3
This new evaluated Mass Spectral Database is the NIST98 Mass Spectral Library. It is distributed along with the NIST Mass Spectral Search Program for Windows. This allows the use of either the search routines from within the mass spectral software of many manufacturers or the NIST MS Search Program itself. The NIST MS Search
Program has been described in numerous publications.4,5,6
In addition to the NIST98 Database, users can also build their own libraries and have structures associated with the spectra. The Wiley 6 Registry of Mass Spectral Data is now available in the NIST format.
The NIST98 MS Search Program allows for many different Desktop configurations to be set by the user for displaying the results of the many different ways to search the NIST98 Library. Not only can unknown spectra be searched against this evaluated Database, but the Database can also be searched using incremental names of synonyms of compounds, by Chemical Abstract Services (CAS) registry numbers, empirical formula, molecular weight, and the identification number given in the Library. In addition, the Database can be searched based on data input as to the m/z value, relative or absolute intensity or type (normal, neutral loss, intensity rank in the spectrum, or whether or not it represents the maximum m/z in the spectrum) of peak. Molecular weight, unknown spectra, and peak searches can be constrained as to what elements are present as well as how many or a range of the atoms of each element can be present in a retrieved spectrum. Unknown spectra and peak searches can be constrained as to an allowable molecular weight range. Searches can also be constrained to retrieve only spectra of those compounds that are also listed in other specified databases such as those maintained by the EPA or NIH.
One of the new features in the NIST MS Search Program, V 1.6, is the ability to include user-generated structures in the form of MOL files in User libraries. This feature has been a part of the HP ChemStation, but it has now been improved so that implicit hydrogens associated with functional groups are displayed.
New Features in the NIST MS Search Program
Two new features of the NIST MS Search Program are AMDIS (Automated Mass Spectral Deconvolution and Identification System) and a very unique routine that will aid in spectral evaluation and interpretation - MS Interpreter.
AMDIS will read and display GC- and LC-MSD data files from most popular instrument data systems. The files are evaluated on the basis of spectral uniqueness. Unique spectra (with contaminating peaks eliminated -deconvoluted spectra) are compared against target libraries or are sent to the NIST MS Search Program for identification. AMDIS is provided with individual target libraries (all derived from the NIST98 Library) for use with environmental, drugs of abuse, toxicological, and flavor/fragrance applications. The libraries can be expanded, and User libraries can be built from chromatographic/mass spectral data or additional spectra from the NIST98 Library or other libraries in the NIST MS Search Program format. Additional information on AMDIS appear in a future applications note in this newsletter.
Just one of the many features of MS Interpreter is that it provides an enhancement of the popular ISOFORM utility included with previous versions of the NIST MS Search Program. This is used to calculate and display (graphical and numerically) isotopic patterns based on inputted formulas and to produce formulas for neutral fragments and ions based on molecular formula, elemental constraints, and/or m/z values of ions and neutrals.
In addition to all the functions of ISOFORM, MS Interpreter allows for a graphical comparison of observed and theoretical isotopic patterns, the ability to use a graphic tool to determine and display the m/z difference between a designated precursor peak and another peak, and, based on a simple single-bond cleavage presumption, the display of the portion of a molecular structure represented by individual peaks in the mass spectrum. This feature is a result of Robert Mistrik's Cluster Analysis research reported at the 1997 Palm Springs ASMS meeting. This powerful utility just adds to the ability of using the NIST MS Search Program and the NIST98 Library in the identification of compounds whose spectra are not in the Database.
The NIST MS Search Program, V 1.6, is still provided with three search algorithms (the Identity Search for spectra of compounds whose spectrum is probably in the Library, and the Similarity and Neutral Loss Searches for spectra of compounds whose spectrum is probably not in the Library) that has made it such a widely used utility in mass spectrometry laboratories. This later feature, combined with Substructure Identification, is one of the factors that is being extensively used in the evaluation of APCI and ESI LC/MS spectra obtained by in-source collisionally activated dissociation (CAD) or MS/MS.
What IS Quality?
At issue, under many circumstances, is what is meant by the word "quality." This word has often been used as a size-comparative measure when it comes to mass spectral libraries. In the past, the basis for judgment has been the number of spectra; however, this has changed with the NIST98 Library. The NIST98 Library's total number of peaks/average number of peaks/median number of peaks values (10,033,398/93/78) are far greater than those of the only other large spectrum number/mass spectral library (the Wiley Registry of Mass Spectral Data - 8,087,622/35/10)6.
Figure 3. Two of the many views of AMDIS. Both target and nontarget analytes can be pulled from very complex reconstructed total ion current chromatograms. This is one of the most thoroughly tested programs ever developed for use with LC/MS and GC/MS data.
As can be easily imagined, with the numbers of spectra in the tens of thousands, the possibility of duplicating a given spectrum is very possible. This has been a problem with all previous mass spectral libraries. The only way to assure that this is not a factor is to have some unique identifier associated with each unique spectrum. This is best accomplished by the use of a CAS registry number or a structure. The NIST98 Library has a larger percentage of spectra with a unique identifier than any other mass spectral library that has been distributed. Of all the compounds in the NIST98 Library, 99.95% have an associated structure. These unique structures were compared using one of the many in-house-developed software programs utilized by NIST to assure the highest quality. Remember, there is a difference between replicate spectra (multiple spectra of the same compound from different sources) and duplicate spectra (the same spectrum presence in the library with different index numbers).
In combination, the NIST98 Library and the NIST MS Search Program represent one of the most powerful tools for the mass spectrometrist. As with any power tool, there are a lot of features that require training to fully implement.
1. P. Ausloos, C. Clifton, S. Lias, A. Mikaya, S. Stein, D. Sparkman, D. Tchekovskoi, V. Zaikin, D. Zhu "The Critical Evaluation of a Comprehensive Mass Spectral Library," J. Am. Soc. Mass Spectrom. 1999, 10, 288-299.
2. V. Zaikin, P. Ausloos, C. Clifton, S. Lias, A. Mikaya, D. Sparkman, S. Stein "The Evaluation of a Comprehensive MS Reference Library," Proceedings of the 43rd ASMS Conference on Mass Spectrometry and Allied Topics, Atlanta, GA, 1995.
3. S. Stein "Estimating Probabilities of Correct Identification from Results of Mass Spectral Library Searches," J. Am. Soc. Mass Spectrom. 1994, 5, 316-323.
4. S. Stein, D. Scott "Optimization and Testing of Mass Spectral Library Search Algorithms for Compound Identification," J. Am. Soc. Mass Spectrom. 1994, 5, 859-866.
5. S. Stein "Chemical Substructure Identification by Mass Spectral Library Searching," J. Am. Soc. Mass Spectrom. 1995, 6, 644-655.
These figures are based on reprint of a paper distributed by F. W. McLafferty et al. in conjunction with a Poster Presentation at the 45th ASMS meeting in Palm Springs, CA, 1997.