Modern Methods of Plant Analysis / Moderne Methoden Der Pflanzenanalyse

123 phase and hence have no direct bearing on the retention time of solutes. However in gas-solid chromatography, a considerable quantity of the mobile phase may be adsorbed on the surface of the stationary adsorbent which diminishes the column's effective length and ability to retain solutes. In this respect helium has been found to be preferable to most other gases (GREENE and Roy, 1957) because it is adsorbed to the least extent. 3. Packed columns offer a considerable resistance to flow, which may create a pressure differential between inlet and outlet of sufficient magnitude to cause an unfavorable flow rate through a significant length of the column. A reduced inlet/outlet pressure ratio can be obtained by using light molecular weight gases toward which the column packing shows the greatest permeability. The flow rate of the mobile phase is normally adjusted by altering the column inlet pressure, for which purpose commercial pressure regulators of sufficient accuracy are available. Quantitative measurements of the flow rate can be made by a number of methods, including rotameters, orifice meters, soapfilm flow meters and displacement of water. The former two methods are the most con­ venient but the least accurate; moreover they create a back pressure and are temperature dependent whereas although the moving soap bubble is cumbersome to employ and unusable for continuous readings, it is preferred when the highest accuracy is required.

— Contents.- Emission and Atomic Absorption Spectrochemical Methods..- A. Flame Emission Methods.- I. Lundegardh Method.- II. Flame Photometric Method for Sodium, Potassium and Calcium.- III. Flame Spectrophotometric Method for Magnesium.- IV. Flame Spectrophotometric Method for Iron, Manganese and Copper.- B. Arc Emission Analysis.- I. The Variable Internal Standard, Cathode Layer Method.- II. Direct Cathode Layer Analysis of Plant Ash.- III. The Method of Successive Additions.- C. Spark Emission Methods.- I. Porous Cup Solution Spark Method for Magnesium.- II. The Pelleted Rotating Disc Spark Method.- D. Atomic Absorption Methods.- References.- Mass Spectrometric Methods..- A. Instrumentation.- B. The Sample.- I. Vapor Pressure.- II. Techniques of Introduction.- III. Purity.- C. Origin of Mass Spectra and their Interpretation.- I. Ionization and Fragmentation of Organic Molecules.- II. The Molecular Weight.- III. Simple Fragments.- IV. Rearrangements.- V. Metastable Ions.- VI. Multiple-Charged Peaks.- VII. Mixtures.- VIII. High Resolution Spectra.- D. Specific Applications.- I. Amino Acids.- 1. Qualitative Spectra.- 2. Quantitative Analysis of Amino Acid Mixtures.- II. Amino Acid Sequence in Peptides.- III. Fatty Acids and Related Compounds.- IV. Alkaloids.- V. Miscellaneous Groups.- VI. Determination of Stable Isotopes in the Intact Molecule.- Appendix I.- References.- Plant Spectra: Absorption and Action..- A. Instrumentation.- B. Light Scatter Phenomena.- C. Absorption Spectra.- D. Action Spectra.- E. Fluorescence Excitation Spectra.- References.- Gefriertrocknung..- A. Die biologischen Probleme der Gefriertrocknung.- I. Das intracellular Gefrieren.- II. Die Vitrifikation.- III. Das extracelluläre Gefrieren.- IV. Die Trocknung.- V. Die Fehlerquellen.- VI. Testmethoden.- B. Die Vakuum-Sublimation.- I. Theoretische Grundlagen.- II. Apparative Ausrüstung.- 1. Der Vakuum-Pumpstand.- 2. Der Trocknungsraum.- 3. Kühleinrichtungen.- 4. Objektheizung.- 5. Meßgeräte.- III. Gefriertrocknungsanlagen.- C. Anwendungen.- I. Gefriertrocknung flüssiger Präparate.- II. Konservierung von Mikroorganismen.- III. Fixation für cytochemische Untersuchungen.- IV. Fixation für elektronenoptische Untersuchungen.- D. Verwandte Methoden.- I. Gefrierkonservierung.- II. Gefriersubstitution.- III. Gefrierschnitte.- Vapour Phase Chromatography..- A. Theoretical Approach.- I. Chromatography in General.- 1. Nature of Stationary Phase: Adsorption vs. Partition.- 2. Mobile Gas Phase : Elution, Displacement and Frontal Analyses.- II. Types of Theories.- 1. Linear vs. Non-Linear Distribution Isotherms.- 2. Ideal vs. Non-Ideal Chromatography.- III. Plate Theory.- 1. Calculation of the Number of Theoretical Plates.- 2. Calculation of the Distribution Coefficient.- 3. Evaluation of a Chromatographic Separation.- IV. Rate Theory.- 1. Eddy Diffusion.- 2. Molecular Diffusion.- 3. Resistance to Mass Transfer.- 4. Temperature, Flow Rate and Pressure.- V. Modifications and Additional Theories.- B. Apparatus Requirements.- I. Detection Systems.- 1. Integral Methods.- a) Titration.- b) Electrical Conductivity.- c) Volume and Pressure Changes.- d) Combustion to Carbon Dioxide.- 2. Differential Detectors — which Consume the Sample.- a) Combustion to Carbon Dioxyde.- b) Hydrogenation to Methane.- c) Flame Emissivity.- d) Hydrogen Flame and Thermocouple.- e) Flame Ionization.- 3. Differential Detectors — which Preserve the Sample.- a) Surface Potential.- b) Dielectric Constant.- c) Impedance of Gas Flow.- d) Heat of Vaporization.- e) Interferometer.- f) Spectroscopy.- g) Radioactivity.- h) Thermal Conductivity — the Katharometer or Diapharometer.- i) Gas Density Balance.- j) High Voltage Ionization.- k) Thermionic Emission.- 1) ? -Ray Ionization.- m) Radio Frequency Detector.- 4. Summary of Detector Characteristics.- II. Gas Phase.- III. Sample Introduction.- 1. Gaseous Samples.- 2. Solid and Liquid Samples.- IV. Stationary Phase.- 1. Column Construction.- 2. Column Dimensions.- 3. Capillary Columns.- 4. Solid Support.- 5. “Active” Solid Adsorbents.- a) Charcoal, Alumina Silica Gel.- b) Molecular Sieves.- c) Tailing Reducers.- d) Chromatothermography.- e) Multiple Columns.- 6. Liquid Phase for GLC.- a) Column Preparation.- b) Selection of the Stationary Phase.- c) Improvement of Peak Symmetry.- V. Temperature Control.- 1. Types of Heating Units.- 2. Programmed Temperature Chromatography.- C. Techniques.- I. Sample Preparation.- 1. Removal of Water.- 2. Esterification.- II. Fraction Collection.- III. Sample Identification.- 1. Use of Standards.- 2. Homologous Series Plots.- 3. Detectors with Different Responses.- 4. Auxiliary Instruments.- 5. Electron Affinity Spetroscopy.- 6. Functional Group Classification.- IV. Quantitative Analysis.- 1. Peak Heights.- 2. Peak Areas.- 3. Overlapping Peaks.- 4. Sloping Base Line and Secondary Peaks.- 5. Instrument Correction Factors.- 6. Internal Standard and Internal Normalization.- D. Applications.- I. Analytic Applications.- 1. Carbon Dioxide and Oxygen : Respiration and Photosynthesis.- 2. Hydrogen, Hydrogen Sulfide, Methane and other Fermentation Gases.- 3. Olefins and Saturated Hydrocarbons.- 4. Nitrogen, Nitrous Oxide, Nitrogen Dioxide and Nitric Oxide.- 5. Ammonia, Organic Amines and Amino Acids.- 6. Alkaloids, Indoles, Purines and Related Compounds.- 7. Carbohydrates.- 8. Lipids, Fatty Acids.- 9. Mono and Dicarboxylic Acids of Low Molecular Weight, and their Derivatives.- 10. Alcohols, Aldehydes, Ketones and Miscellaneous Esters.- 11. Phenyl Propanoid Compounds, Aromatic Acids, Phenols and Related Substances.- 12. Terpenes.- 13. Sulfur Compounds.- 14. Steroids.- 15. Miscellaneous Compounds.- II. Preparative Gas Chromatography.- E. Conclusion.- References.- Ion-Exchange Chromatography..- A. Ion-Exchange Materials.- I. Fundamental Properties of Ion-Exchange Resins.- 1. Chemical Structure.- 2. Physical Properties.- a) Cross-Linking.- b) Exchange Capacity.- c) Particle Size.- II. Ion-Exchange Celluloses.- B. Theory of Chromatographic Procedures.- I. Elution Analysis.- 1. Theory of Elution Analysis.- 2. Conditions for Successful Elution Analysis on Ion-Exchange Resins.- II. Displacement Development.- 1. Completely Ionized Components.- 2. Incompletely Ionized Components.- Comparison of Elution and Displacement Methods.- III. Frontal Analysis.- C. Apparatus.- D. Experimental Procedures.- I. Purification of Ion-Exchange Resins.- II. Preparation of the Column.- III. Operation of the Column.- 1. Elution Analysis.- a) Column Loading.- b) Choice of Solvents.- c) Selection of Temperature.- d) Analysis of Effluent.- e) Regeneration of Ion-Exchangers.- 2. Displacement Development.- a) Selection of Column Size.- b) Concentration of Developer.- c) Size of Fraction.- d) Regeneration of Resins.- E. Some Applications of Ion-Exchange Chromatography.- I. De-Ionization and Preliminary Group Separation of Extracts from Plant Tissues.- Separation into Four Groups.- a) Aromatic Substances.- b) Cationic or Basic Groups.- c) Acidic Substances.- d) Neutral Substances.- II. Separation of a Group of Closely Related Solutes by the Elution Method.- III. Separation of Compounds of High Molecular Weight.- F. Ion-Exclusion.- G. Mechanism of Adsorption of Solutes on Ion-Exchange Resins.- H. Applicability of Ion-Exchange Chromatography.- I. Choice of Ion-Exchanger.- II. Conditions for Chromatography.- III. Rechromatography.- References.- Table 1. Chromatographie grade resins and celluloses.- Molecular Sieving other than Dialysis..- A. Ion-Exchange Materials as Ionic Sieves.- Separations by Ionic Sieving.- B. Molecular Sieving on Starch.- C. Dextran Gels as Molecular Sieves.- 1. Theory of gel Filtration.- 2. Preparation and Operating of Columns.- 3. Some Applications of Dextran Gels as Molecular Sieves.- References.- Dünnschicht-Chromatographie..- A. Methode und Geräte.- I. Die Herstellung dünner Sorptionsschichten.- II. Sorptionsmittel und Bereitung der Streichmasse.- 1. Kieselgel G für Dünnschicht-Chromatographie „Merck“.- 2. Aluminiumoxid G für Dünnschicht-Chromatographie „Merck“.- 3. Kieselgur G für Dünnschicht-Chromatographie „Merck“.- III. Auftragen der Substanzen und Auswahl des Elutionsmittels.- IV. Trennkammer und deren Sättigungszustand.- V. Sichtbarmachung der getrennten Substanzen.- 1. Chemische Verfahren.- 2. Physikalische Verfahren.- a) Aktivitätsmessung.- b) Fluorescenzverfahren.- 3. Biologische Verfahren.- VI. Untere Erfassungsgrenze im Vergleich zur Papierchromatographie.- VII. Dokumentation und allgemeine Auswertung.- VIII. Quantitative Auswertung.- 1. Direkte Verfahren.- 2. Indirekte Verfahren.- B. Spezielle Arbeitstechniken.- I. Zirkular- und Formgebungstechnik.- II. Stufentechnik.- III. Zweidimensionale Arbeitsweise ohne und mit Zwischenreaktion.- C. Anwendungsbereich und Einsatzmöglichkeiten.- D. Anwendungsbeispiele.- 1. Alkaloide.- 2. Aminosäuren.- 3. Indol-Auxine.- 4. Steroide und Steroidglykoside.- 5. Lipide.- Literatur.- Paper Chromatography on a Preparative Scale..- A. General.- I. Impurities.- II. Choice of Solvent System.- III. Quantities.- IV. Application of the Sample.- V. Localisation of Bands.- VI. Elution of the Resolved Spots.- B. Multisheet- and Cardboard-Chromatography.- C. Separation on Paper-Packs.- I. Circular Chromatopack Procedure.- II. One Dimensional Chromatopack Procedure.- III. Chromatopile Procedure.- D. Column Chromatography.- I. Columns of Cellulose Powder.- 1. Filling of the Column.- 2. Elution.- 3. Fraction CoUector.- II. Paper Roll Column Chromatography.- E. Continous Paper Chromatography.- F. Accelerated Chromatography.- I. High Temperature Paper Chromatography.- II. Centrifugal Chromatography.- References.- Determination of Size, Shape and Homogeneity of Macromolecules in Solution..- A. Average Molecular Weights.- B. Osmotic Pressure.- I. General Theoretical Considerations.- 1. Definition of Osmotic Pressure.- 2. van’;t Hoff’;s Law and Derivation of Osmotic Pressure Equation.- a) Ideal Charged Macromolecule-Donnan Equilibrium.- b) Non-Ideal Charged or Uncharged Macromolecule, i.e. the General Case.- 3. Extrapolation to Zero Concentration.- II. Experimental Method.- 1. Types of Osmometers.- a) Dynamic and Static Methods.- b) Membranes.- 2. Difficulties and Precautions.- C. Light Scattering.- I. Fundamental Concepts of the Theory of Light Scattering.- II. Scattering by Dilute Solutions.- III. Fluctuation Theory of Scattering.- IV. Systems of Isotropic Particles Comparable in Size to the Wave Length: Internal Interference.- 1. Dissymmetry Method.- 2. Zimm Method.- V. Polydispersity.- VI. Anisotropy and Depolarisation.- VII. Equations for Polarised Incident Light.- VIII. Scattering from Large Spherical Particles — Validity of Approximate Solution for Internal Interference.- IX. Multicomponent Systems.- X. Charged Macromolecules : Non-Random Systems.- XI. Interacting Systems.- XII. Experimental Methods.- 1. Measurement of Reduced Intensity of Scattering.- 2. Cells.- 3. Volume and Refraction Effects.- 4. Back Reflection Correction.- 5. Calibration of Light Scattering Photometers.- 6. Measurements on Coloured Solutions.- 7. Fluorescent Solutions.- 8. Measurement of Refractive Index Increment.- 9. Clarification of Solutions.- 10. Concentration of Solute.- 11. Measurement of 90° Scattering.- 12. Dissymmetry Method.- 13. Angular Intensity Measurements.- D. Diffusion.- I. Information Available from Diffusion.- II. Diffusion and the Laws of Diffusion.- 1. Types of Diffusion Measurements Carried out in Practice.- a) Steady-State Diffusion.- b) Free Diffusion.- c) Restricted Diffusion.- d) Diffusion during a Sedimentation Velocity Experiment.- 2. Feck’;s first Law and Definition of Diffusion Coefficient.- 3. Thermodynamic Interpretation of Diffusion Coefficient.- 4. Fick’;s second Law.- 5. Equations for Evaluating Diffusion Coefficients Using Measurements of Free Diffusion Experiments.- 6. Correction of Diffusion Coefficients to Standard Conditions.- a) Correction of D for Viscosity.- b) Correction of D for Temperature.- c) Extrapolation of D to Zero Solute Concentration.- 7. Detection of Heterogeneity by Free-Diffusion Experiments.- III. Experimental Method for Steady-State and Free-Diffusion Experiments.- 1. Steady-State Diffusion — the Diaphragm Cell.- 2. Free Diffusion.- 3. Optical Methods for Free Diffusion.- a) Schlieren Method.- b) Gouy Interference Fringe Method.- c) Rayleigh Interference Fringe Method.- d) Polarized-Light Method.- 4. Zero Time Correction.- 5. Method of Expressing Results.- 6. Example of Calculation of Reduced Height-Area Ratio.- From Schlieren Photographs of an Artificial Boundary in the Ultracentrifuge.- IV. The Use of the Diffusion Coefficient in Determining Molecular Weight.- 1. Combination of Sedimentation and Diffusion Coefficients to give Molecular Weight.- 2. Approximate Method Using Stokes’; Law.- 3. Combination of Diffusion Coefficient and Intrinsic Viscosity.- 4. Diffusion Coefficient Relationship to Molecular Shape.- V. Factors Contributing to Uncertainty in the Experimental Determination of the Diffusion Coefficients of Macro-Molecules.- 1. Interaction of Solute Flows.- 2. Charge Effects with Macromolecules.- 3. Initial Conditions — Dialysis.- 4. Purity of Solute.- E. Ultracentrifugation.- I. Information Available from Sedimentation, and General Aspects of Sedimentation Analysis.- II. The Two Facets of Sedimentation Analysis.- III. Non-Ideal Behaviour and Charge Effects.- IV. Sedimentation Velocity.- 1. The Boundary and Optical Means of Observation.- 2. The Sedimentation Coefficient and its Experimental Evaluation.- 3. Minimum Requirements from Sedimentation Analysis which must be Fulfilled if a Substance is to be Claimed as Homogeneous with Respect to Sedimentation Coefficient.- 4. More Stringent Tests which must be Satisfied by a Homogeneous Material.- 5. Expressions of the Degree of Heterogeneity of a Material.- a) Actual Distribution of Sedimentation Coefficients.- b) Method of Indicating Departure of Sedimentation Curve from that Representative of Homogeneity.- 6. Density Differences as a Test of Heterogeneity. Equilibrium Sedimentation in a Density Gradient.- V. Equation for Determining Molecular Weight from Sedimentation Velocity.- 1. The Svedberg Equation.- 2. Approximate Methods.- 3. Partial Specific Volume.- VI. Sedimentation Equilibrium and Approach-to-Equilibrium.- 1. Klainer-Kegeles Calculation of the Archibald Method when a Plateau Region is Still Present.- 2. A General Method of Calculation which can be Applied throughout the Cell whether or not a Plateau Region Exists.- 3. Method of Calculation of Molecular Weight which Gives the Weight-Average Molecular Weight of the Whole Solute once Equilibrium has been Attained.- 4. Method of Calculation which Gives the z-Average Molecular Weight of the Whole Solute once Equilibrium has been Attained.- VII. The Proportions of Components in a Sedimenting Mixture.- 1. The Johnston-Ogston Effect.- 2. Velocity Sedimentation in Systems of Reversibly-Interacting Components.- F. Viscosity.- I. Newtonian and Non-Newtonian Viscosity.- II. Functions of Viscosity.- III. Viscosity Relations for Particles of Different Shapes.- IV. Experimental Methods.- G. Particle Shape from Hydrodynamic Measurements.- I. Spheroidal Molecules.- 1. Frictional Coefficient.- 2. Intrinsic Viscosity.- 3. Combination of Hydrodynamic Methods to Give Particle Shape.- II. Randomly-Coiled Molecules.- Sectional References.- Optical Rotatory Dispersion. Its Application to Protein Conformation..- A. Mean Residue Rotation of Polypeptides and Proteins.- B. Optical Rotatory Dispersion — Drude Equation.- C. Rotatory Properties of Synthetic Polypeptides.- D. Optical Rotatory Properties of Proteins.- Existence of Structures in Proteins other than the Right-Handed ?-Helix and Random Coil.- E. Temperature Dependence of Optical Rotation.- ...