Frans_M_Everaerts_Isotachophoresis_378342.pdf

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CONDUCTIVITY DETECTION 143 6.4.4. The a.c. method of resistance determination In order to measure the conductivity (resistance) of an electrolyte, in which a potential of about 6 kV towards earth is present, good galvanic insulation between the sensing electrodes and the electronic circuit (i.e., the conductimeter) at low potential is necessary. This can be realized by measuring the conductivity with an a.c. current that passes through a transformer with two separated coils, the construction of which will be described in detail. All types of electric leak currents must be prevented; even a leak current via the sensing electrodes of 1 0-9 A will have a considerable influence on the measurement of the conductivity. This is shown particularly in this chapter, where the coating of electrodes is dealt with. We found that the conductivity of isotachophoretic zones could be determined optimally with a probe in which the micro-sensing electrodes were constructed to be equiplanar. In order to prevent an electric current flowing from one sensing electrode towards the other, if the electrodes are mounted badly so that a potential difference exists between the electrodes by the driving current via the transformer, a capacitor is arranged in series with the transformer. It can be repeated (see section 6.4.1) that in isotachophoretic analyses the sample ions separate according to their effective mobilities and form discrete zones with concentrations that are constant with time, homogeneous throughout each zone and directly related to the concentration of the leading electrolyte. If the electric current is stabilized, all of the velocities of the zones, in the steady state, are identical and constant with time. The boundary between two successively moving zones is sharpened by the electric field, which increases stepwise, following each zone in whch it is a constant, to compensate for the less mobile ions. This stepwise increase in the electric field causes a stepwise increase in the electric resistance according to Ohm’s law. In addition, this stepwise increment is automatically directly proportional to the effective mobilities of the ionic species actually present in each zone. If the operational system is chosen well (e.g., Table 12.1), the electric resistance of each zone is determined by the electric resistance of the leading electrolyte zone. These conductivities are not defined by the electric driving current, assumed temperatures can be neglected. Because the conductivities of the zones are determined, the length of the zones provides the quantitative information. 6.4.5. Conductivity probe with equiplanar-mounted sensing electrodes The construction of the measuring cell is shown in Fig.6.16, which shows also the principle of its construction. In a round piece of transparent insulating material, e.g., Perspex (acrylic), a hole of diameter 0.4 mm is drilled along part of its length (a). A metallic foil (e.g., Pt- 10-30% Ir of thickness 0.01 mm) is glued to this piece of transparent insulating material at the opposite end to that where the 0.4-mm hole has been drilled. Cyanolite@ proved to be a good adhesive when Perspex was used as the insulating material. If different transparent material (e.g., TPX) is used, a different procedure has to be followed. A small core of TPX is prepared, which is surrounded with a cylinder of acrylic that fits exactly. The remainder of the procedure can then be followed as for Perspex. With aid of a template (shown in Fig.6.16a), the centre is located with aid of a 0.2-mm drill. Special care has to be taken to ensure that this 0.2-mm hole does not
144 DETECTION SYSTEMS Fig.6.16. Conductivity probe with the measuring electrodes mounted equiplanar. All dimensions are given in millimetres. For explanation, see text. C d
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Journal of Chromatogaphy Library -
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Journal of Chromatography Library -
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Dedicated to Pr0f.Dr.h. A.I.M. Keul
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Contents Preface ..................
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CONTENTS IX 6.4.2. The d.c. method
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CONTENTS XI 12.2.2. Applications ..
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It is very well known that charged
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Chapter 1 Historical review SUMMARY
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HISTORICAL REVIEW 3 Independently i
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THEORY
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Chapter 2 Principles of electrophor
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MOVINGBOUNDARY ELECTROPHORESIS a S
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MOVINGBOUNDARY ELECTROPHORESIS 0 iu
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ISOTACHOPHORESIS 13 2.4. PRINCIPLE
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ISOTACHOPHORESIS 15 As the anionic
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ISOTACHOPHORESIS velocities, so tha
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ISOTACHOPHORESIS 19 d.t ’.t I Fig
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ISOTACHOPHORESIS 21 t Fig.2.8. Isot
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ISOELECTRIC FOCUSING 23 The four is
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DISCUSSION 25 Fig.2.11. Survey of t
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Chapter 3 Concept of mobility SUMMA
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IONIC MOBILITY AND IONIC EQUIVALENT
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EFFECTIVE IONIC MOBILITY 31 obtain
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EFFECTIVE IONIC MOBILITY 33 compari
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EFFECTIVE IONIC MOBILITY Fig.3.4. R
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DETERMINATION OF IONIC MOBILITIES 3
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DETERMINATION OF IONIC MOBILITIES 3
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Chapter 4 Mathematical model for is
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GENERAL EQUATIONS 43 anionic specie
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GENERAL EQUATIONS 4.2.1. Equilibriu
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GENERAL EQUATIONS 41 i Similar equa
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GENERAL EQUATIONS 49 Uthzone (U-llt
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GENERAL EQUATIONS 4.2.4. Modified O
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GENERAL EQUATIONS TABLE 4.2 REDUCED
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MATHEMATICAL MODEL FOR THE STEADY S
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VALIDITY OF THE ISOTACHOPHORETIC MO
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CHECK OF THE ISOTACHOPHORETIC MODEL
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CHECK OF THE ISOTACHOPHORETIC MODEL
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REFERENCES 81 Fig.4.17. Relationshi
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Chapter 5 Choice of electrolyte sys
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CHOICE OF THE SOLVENT 85 In general
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CHOICE OF THE SOLVENT TABLE 5.2 THE
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CHOICE OF THE SOLVENT pH and pKvalu
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CHOICE OF THE SOLVENT 91 TABLE 5.4
Page 108 and 109: CHOICE OF THE pH OF THE LEADING ELE
Page 110 and 111: CHOICE OF THE pH OF THE LEADING ELE
Page 112 and 113: CHOICE OF THE TERMINATING AND LEADI
Page 114 and 115: ADDITIONS TO THE ELECTROLYTE SOLUTI
Page 116 and 117: EXAMPLES Choice of solvent. Can wat
Page 118 and 119: EXAMPLES 103 solvent, hoping that a
Page 120 and 121: EXAMPLES TABLE 5.11 STEP HEIGHTS OF
Page 122 and 123: EXAMPLES TABLE 5.12 STEP HEIGHTS OF
Page 124 and 125: Fig.5.9. Isotachopherograms of the
Page 126 and 127: EXAMPLES II 4 3 Fig.5.11. Isotachop
Page 128 and 129: REFERENCES 113 Example I. As exampl
Page 130 and 131: INSTRUMENTATION
Page 132 and 133: Chapter 6 Detection systems SUMMARY
Page 134 and 135: THERMOMETRIC RECORDING 6.1.3. Combi
Page 136 and 137: THERMOMETRIC RECORDING Potential gr
Page 138 and 139: THERMOMETRIC RECORDING /2 Fig.6.1.
Page 140 and 141: THERMOMETRIC RECORDING T t l Fig.6.
Page 142 and 143: THERMOMETRIC RECORDING 7 127 It-- I
Page 144 and 145: THERMOMETRIC RECORDING a concentrat
Page 146 and 147: HIGH-FREQUENCY CONDUCTIVITY DETECTI
Page 148 and 149: CONDUCTIVITY DETECTION 133 Fig.6.9.
Page 150 and 151: CONDUCTIVITY DETECTION 135 The d.c.
Page 152 and 153: CONDUCTIVITY DETECTION 137 Hi V 1kR
Page 154 and 155: CONDUCTIVITY DETECTION Fig.6.12. Co
Page 156 and 157: CONDUCTIVITY DETECTION Fig.6.14. Th
Page 160 and 161: CONDUCTIVITY DETECTION 145 contact
Page 162 and 163: CONDUCTIVITY DETECTION 147 We can n
Page 164 and 165: CONDUCTIVITY DETECTION 149 N.Y., U.
Page 166 and 167: CONDUCTIVITY DETECTION 151 achieved
Page 168 and 169: UV ABSORPTION METER 153 -_-.- +- R
Page 170 and 171: UV ABSORPTION METER Fig.6.22. Contr
Page 172 and 173: W ABSORPTION METER r +15V -15V Mod
Page 174 and 175: W ABSORPTION METER 159 TABLE 6.4 PR
Page 176 and 177: W ABSORPTION METER 230 240 2% m zm
Page 178 and 179: to Mod (Fig 6.24) oscillator I sync
Page 180 and 181: UV ABSORPTION METER 165 dicular to
Page 182 and 183: Fig.6.31. Isotachopherograms for th
Page 184 and 185: UV ABSORPTION METER 169 50 Fig.6.33
Page 186 and 187: ADDITIVES TO THE ELECTROLYTES 171 6
Page 188 and 189: ADDITIVES TO THE ELECTROLYTES 173 e
Page 190 and 191: ADDITIVES TO THE ELECTROLYTES 175 a
Page 192 and 193: ADDITIVES TO THE ELECTROLYTES 177 o
Page 194 and 195: ADDITIVES TO THE ELECTROLYTES 179 d
Page 196 and 197: ADDITIVES TO THE ELECTROLYTES 181 T
Page 198 and 199: ADDITIVES TO THE ELECTROLYTES Fig.6
Page 200 and 201: ADDITIVES TO THE ELECTROLYTES 185 F
Page 202 and 203: ADDITIVES TO THE ELECTROLYTES 1 2 3
Page 204 and 205: ADDITIVES TO THE ELECTROLYTES 189 n
Page 206 and 207: COATING OF THE MICRO-SENSING ELECTR
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DETECTION LIMITS 193 electric drivi
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DETECTION LIMITS 195 Fig.6.48. Infl
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DETECTION LIMITS 197 TABLE 6.6 SURV
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CONCLUSION 199 average length of a
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REFERENCES 201 seen. Again it is cl
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Chapter 7 Instrumentation SUMMARY T
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INJECTION SYSTEMS I! I n Fig.7.1. P
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INJECTION SYSTEMS Fig.7.3. Exploded
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INJECTION SYSTEMS Fig.7.5. Injectio
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COUNTER ELECTRODE COMPARTMENTS 21 1
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COUNTER ELECTRODE COMPARTMENTS Even
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COUNTER ELECTRODE COMPARTMENTS 21 5
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EQUIPMENT the large bore, a more di
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EQUIPMENT 219 belonging to three cl
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EQUIPMENT 221 signal of the thermoc
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EQUIF'MENT 223 No effect on the res
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EQUIPMENT 225 Fig.7.14. Electrophor
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EQUIPMENT Fig.7.16. Photograph of t
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EQUIPMENT 229 mounted equiplanar, w
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COUNTER FLOW OF ELECTROLYTE 231 ins
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COUNTER FLOW OF ELECTROLYTE p High
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COUNTER FLOW OF ELECTROLYTE Fig.7.2
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COUNTER FLOW OF ELECTROLYTE 231 aro
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COUNTER FLOW OF ELECTROLYTE p high
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COUNTER FLOW OF ELECTROLYTE 24 1 7.
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COUNTER FLOW OF ELECTROLYTE I I 31
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COUNTER FLOW OF ELECTROLYTE max. 15
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APPLICATIONS
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Chapter 8 Introduction SUMMARY In t
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INTRODUCTION 25 1 the various ionic
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Chapter 9 Practical aspects SUMMARY
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DISTURBANCES CAUSED BY H+ AND OH 25
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DISTURBANCES CAUSED BY H+ AND OH- 2
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DISTURBANCES DUE TO CO, 263 Electro
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ENFORCED ISOTACHOPHORESIS 265 t T T
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WATER AS TERMINATOR 267 function of
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PURIFICATION OF THE TERMINATOR 7 4
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REFERENCES 271 AS an example, the c
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Chapter 10 Quantitative aspects SUM
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THERMOMETRIC MEASUREMENTS 215 vj c
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THERMOMETRIC MEASUREMENTS TABLE 10.
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CONDUCTIMETRIC MEASUREMENTS factor
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CONCLUSION 28 1 Tables 10.3-10.5 wa
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Chapter 11 Separation of cationic s
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SEPARATION USING A THERMOCOUPLE AS
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I SEPARATION USING A THERMOCOUPLE A
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SEPARATION USING CONDUCTIVITY AND U
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Chapter I2 Separation of anionic sp
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SEPARATION USING A THERMOMETRIC DET
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SEPARATION USING CONDUCTIVITY AND W
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Chapter 13 Amino acids, peptides an
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AMINO ACIDS TABLE 13.1 OPERATIONAL
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AMINO ACIDS 8- ?- 6- 5- 4- 3- 2- f-
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AMINO ACIDS 317 TABLE 13.5 STEP HEI
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AMINO ACIDS Fig.13.3. Schematic dia
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AMINO ACIDS TABLE 13.6 DETERMINATIO
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SEPARATION OF PROTEINS IN AMPHOLYTE
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SEPARATION OF SMALL PEPTIDES reprod
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Chapter I4 Separation of nucleotide
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Chapter 15 Enzymatic reactions SUMM
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ENZYMATIC CONVERSION OF GLUCOSE (FR
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ENZYMATIC CONVERSION OF PYRUVATE 35
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Chapter 16 Separations in non-aqueo
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SEPARATION OF ANIONIC SPECIES IN ME
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SEPARATION OF CATIONIC SPECIES IN M
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EXPERIMENTS IN AQUEOUS METHANOLIC S
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Chapter I7 Counter flow of electrol
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INTRODUCTION 317 In various operati
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EXPERIMENTAL 0% 10 % a b 60 % a b a
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EXPERIMENTAL 381 caused by the coun
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CONCLUSION 383 c t r ’r; I I"
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APPENDICES
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Appendix A Simplified model of movi
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PROCEDURE OF COMPUTATION A.3. PROCE
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EXPERIMENTAL 39 1 TABLE A1 THEORETI
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DISCUSSION E I I Fig.A2. Graphical
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Appendix B Diameter of the narrow-b
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Appendix C Literature 1897-1966 F.
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LITERATURE 399 B.P. Konstantinov an
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LITERATURE 401 1971 L. Arlinger, Is
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LITERATURE 403 1973 L. Arlinger and
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LITERATURE 405 A. Chrambach and J.S
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LITERATURE 407 M. Coxon and M.J. Bi
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Symbols and abbreviations SYMBOLS A
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SYMBOLS AND ABBREVIATIONS SUPERSCRI
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Subject index A Absorption meter, U
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SUBJECT INDEX 41 5 Detection limit
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SUBJECT INDEX 41 7 --_ , separation
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