Digitized Theses and Dissertations (1940 - 2009)
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Browsing Digitized Theses and Dissertations (1940 - 2009) by Department "Chemistry, Department of"
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Item 1. Application and optimization of thermospray HPLC/MS with direct electrical heating of the capillary vaporizer. 2. A moving belt transport detector for HPLC based on thermospray vaporization(1985) Yang, Lily; Vestal, Marvin L.; Zlatkis, Albert; Deming, Stanley N.; Wentworth, Wayne E.; Middleditch, Brian S.This dissertation is composed of two parts. In Part 1, the new version of thermospray high performance liquid chromatography/mass spectrometry (HPLC/MS) with direct electrical heating of the capillary vaporizer is described and applied to real on-line HPLC/MS analyses. The effect of fundamental parameters, such as vaporizer temperature, jet temperature, solvent composition, mobile phase flow rate, and electrolyte concentration are reported. Effects of these parameters on thermospray performances are discussed as well as the thermospray ionization mechanism. A new technique for calibration of the mass axis under thermospray operating conditions is described. The results show that polyglycols make excellent calibration standards. The thermospray HPLC/MS analysis of a drug mixture under reversed phase gradient elution conditions is reported. Reproducible spectra from each component of the sample eluted from the HPLC column are obtained with molecular ion species as base peaks in all cases. Detection limits are determined as 10 nanograms or less in the full scan mode. Comparison of chromatograms detected by on-line UV absorption and by mass spectrometry shows that chromatographic fidelity is preserved in the thermospray interface. A profile of a biological fluid, water soluble metabolites extracted from guinea pig urine, is obtained with the thermospray HPLC/MS. One of the styrene oxide metabolites, a methylsulfonium ion, is tentatively identified by comparison with synthetic compounds. In Part 2, a moving belt transport detector for HPLC is described which employs thermospray deposition of the sample onto a moving stainless steel belt with subsequent vaporization or pyrolysis into a flowing gas stream for detection in a conventional GC detector. This detector is superficially similar to earlier transport devices in that a moving surface is required and the sample is detected after the solvent is removed. The major unique feature of the new approach is that the solvent is vaporized and removed without being deposited as liquid on the moving surface. The performance of this new transport detector is evaluated by coupling it to a photoionization detector (PID), using amino acids and peptides as test samples. Thermospray deposition efficiency is as high as 69% for phenylalanine in aqueous solution. Detection limits of this thermospray transport PID are typical in the 10-400 pmol range. The system performs satisfactorily with both aqueous and nonaqueous solvents at flow rates typical for HPLC. Performance of the thermospray transport system with electron capture detector (ECD) is also reported using chlorinated pesticides as test samples.Item 1. Assignment of the high field resonances of 5[alpha], 6[alpha]-epoxy-9,11-seco-gorgostan-3[beta],11-diol-9-one 3,11-diacetate (III): through the use of auto-correlated two dimensional and proton-carbon correlated NMR spectroscopy. II. Three novel marine steroids : [delta]⁵-9,11-seco-gorgostene-3[beta],11,24[beta]-triol-9-one (V),3[beta],11-dihydroxy-9,11-seco-dinostan-9-one (VII), and 3[beta],9[alpha],11[alpha]-trihydroxy-dinostane (VII). From the Gorgonian Pseudopterogorgia Americana (Gmelin)(1983) Musmar, M. J.; Weinheimer, Alfred J.; Kohn, Harold Lewis; Alam, Maktoob; Thummel, Randolph Paul; Vestal, Marvin L.The two steroids, [delta]⁵-9,ll-seco7gorgostene-3[beta],ll-diol-9-one and 5[alpha],6[alpha]-epoxy-9,ll-seco-gorgostan-3[beta],ll-diol-9-one, possess a trisubstituted cyclopropane ring in the side chain similar to gorgosterol and acanthasterol. The 1H-nmr spectra of all of these compounds showed the presence of an extra proton due to unusual high shielding. However, the identity of that non-cyclopropane proton has remained unsolved for many years. [...]Item 1. Preparation of analytically stable capillary and packed columns ; 2. Elimination of peak splitting associated with on-column injection ; 3. Preparation and evaluation of new adsorbents for trace analysis.(1983) Ghaoui, Labib H.; Zlatkis, Albert; Geanangel, Russell A.; Hamburg, Arlene; Kimball, Aubrey P.; Wentworth, Wayne E.This dissertation is composed of three parts. In Part I, a coating of silicone gum SE-54 on nylon and chromosorb W has been converted to an analytically stable, immobilized stationary phase layer by cross-linking with an organic peroxide. [...]Item 1. Reduction of phenylthiomethylcarbinyl benzoate esters to alkenes with titanium metal. 2. Cyclopentenone synthesis via the alkylating agent 1-(chloromethyl) ethenyl diethyl phosphate(1983) Loh, Jiann-Ping; Welch, Steven C.; Fuchs, Richard; Thummel, Randolph Paul; Albright, Thomas A.; Cates, Lindley A.A high yield and simple method for the reduction of phe-nylthiomethylcarbinyl benzoate esters to form alkenes by freshly prepared, highly activated titanium metal is presented. Utilization of the alkylating agent !-(chloromethyl)-ethenyl diethyl phosphate with ketones is developed. Cyclopentenone formation either via alkylation, hydrolysis, and cyclization or directly from alkylated ketones under mild basic conditions is described.Item 119sn NMR studies on the complexation of tin (II) halides with various donor solvents(1979) Yeh, Ho-Mei Mimi; Geanangel, Russell A.; Bear, John L.; Vestal, Marvin L.The 119Sn chemical shift of SnX2 (X = F, Cl, Br, I) over a range of solute concentrations in HMPA, DMSO, DMF and glyme are reported. Equilibrium constants for the Complexation of SnX2 with some of these solvents are calculated by assuming a two-site exchange model. Relatively poor precision of calculated equilibrium constants was interpreted as evidence that a two-site exchange model does not provide a satisfactory description of the system. Various factors, such as self-association, ionization and/or temperature dependent shift, are believed to contribute to the scatter of data points which results in inconsistent K values.Item 2-substituted-2-acetamido- N-benzylacetamides : synthesis, spectroscopic and anticonvulsant properties(1987) Le Gall, Philippe; Kohn, Harold L.; Dyckes, Douglas F.; Lemke, Thomas L.Select functionalized amino acid derivatives of the potent anticonvulsant agent [alpha]-acetamido-H-benzylphenylacetamide (68b) and 2-acetamido-H-benzylpropionamide (68a) have been prepared and evaluated. Attention has been focused on the replacement of the [alpha]-phenyl and [alpha]-methyl groups in 68a and 68b by five-membered ring hetereoaromatic moieties, benzo-fused heteroaromatic groups, and simple polar substituents. The synthetic and pharmacological studies revealed several notable findings. First, the use of amidoalkylation procedures using boron trifluoride etherate provided a straightforward and reliable method to introduce an electron-rich heteroaromatic substituent at the a-carbon in the amino acid derivatives. This technology permitted the incorporation of acid sensitive, unsubstituted heteroaromatic compounds (i.e., pyrrole (74). indole (72) and benzofuran (75)) within the molecule. [...]Item A computer simulation study of ion-molecule reactions in the mass spectrometer(1970) Tibbals, Harry Fred; Meisels, G. G.; Drake, G. Wilson; Wentworth, Wayne E.; Bear, John L.; Collins, R. EugeneRelative ion abundances were calculated on the basis of a collision model for multiple order ion-molecule reactions. Allowance was made for the energy dependency of reaction cross sections and the existence of long-lived intermediates whose dissociation was assumed to follow unimolecular decay kinetics. Cross section and rate constant values severely affected calculated abundance curves and permitted the assignment of reaction mechanisms. The model was applied to the ethylene system under conditions where only one primary ion, C[lowered 2]H[lowered 4, raised +], was present, pressures varied from zero to ~0.03 Torr, ion paths were relatively long (0.54 cm), and drawout fields were low (<6.3 Vcm[raised -1]). Agreement between experiment and calculations based on the model was readily obtained for the above conditions when E[raised -1/2] dependent collision cross sections and energy independent dissociation rates were assumed. Calculations for more commonly used conditions of shorter ion paths (~.3 cm) and higher pressures and higher drawout fields (10-12 Vcm[raised -1]) gave very poor fits to data obtained from the literature, which were taken in the presence of several primary ions. Unsuccessful attempts were made to obtain improved fits by approximate corrections for reactions of primary ions other than Inclusion of various complications such as hard-sphere cross sections and field penetration effects did not improve agreement between calculations and experiment when energy independent unimolecular rate constants were used. Allowance for the energy dependence of unimolecular dissociation of C[lowered 4]H[lowered 4, raised +] and C[lowered 5]H[lowered 9, raised +] gave improved fits to experimental data. The calculations indicate that for tertiary complexes dissociation is competitive with collision when the dissociation rate constant is of the order of 10[raised 6] sec.[raised -1]. The effect of the energy dependence of unimolecular rates upon calculated ion abundance vs. pressure curves was evaluated in detail. It was shown that the energy dependence of rate constants for competitive dissociation processes in the CitHg+ complex formed in the ethylene system is similar to that of the C[lowered 4]H[lowered 8, raised +] ion formed by electron impact from the more stable C[lowered 4]H[lowered 8] isomers.Item A file interface and data dictionary for the ECRDBS high level database system(1987) Wu, Yu-Tung; Elmasri, Ramez A.; Huang, Stephen S. H.; Deming, Stanley N.The Entity-Category-Relationship (ECR) data model captures important descriptive semantics of a database, such as generalization hierarchies and attribute inheritance. Since no complete ECR DBMS has been implemented before, an ECR DBMS, called ECRDBS, is implemented to demonstrate the usefulness of the above data modeling concepts. This thesis describes the design and implementation of two components of ECRDBS; the file interface and the data dictionary system. In the first part of the thesis, the indexed file organization on the VAX/VMS system is used to implement a file interface which provides basic, record at a time, file commands for storage, retrieval and updating of information. In the second part of the thesis, a data dictionary system based on the ECR model is implemented. It is responsible for parsing the data definition statements for a particular database and creation of data dictionary files. Function procedures are provided for the user and other components of the ECRDBS system to access the information stored in the data dictionary files.Item A general method for the fluorination of compounds containing boron-hydrogen bonds(1971) VanPaasschen, John Matthew; Geanangel, Russell; Bear, John L.; Welch, Steven C.A method for the fluorination of compounds containing horon-hydrogen bonds using anhydrous hydrogen fluoride as the fluorinating agent is described. Trimethylamine-borane and tertiary-butylamine-borane are fluorinated sequentially, forming the heretofore unknown amlne-monofluoroborane and the amine-difluoroborane and the known amine-trifluoroborane and ammonium-tetrafluoroborate. Preliminary results are also presented on the methylamine-borane and lithium borohydride systems. The formation of the new partially fluorinated amine-boranes is confirmed. Proton and boron-11 n.m.r. data are presented for all of the trlmethylamlne-borane and tertlary-butylamlne-borane adducts. In addition, fluorine-19 n.m.r. data are presented for the trimethylamine-borane adducts. This method for the fluorination of hydridic hydrogens on boron requires no special equipment. The reaction can be run In the air (with precautions against excess moisture, In some cases) on a scale greater than 200 millimoles giving yields of better than 80%.Item A kinetic and thermodynamic study of fast reactions in mixed aqueous solvents by the pressure jump technique(1972) Underdown, David Reuel; Bear, John L.; Kimball, Bruce A.; Geanangel, Russell A.; Wendlandt, Wesley W.The change in the rate constants and stability constants of the one-to-one nickel(II) malonate complex was studied as a function of changing structure and macroscopic properties of the solvent at different temperatures. The favorable equilibrium constant, forward rate constant and entropy change of the nickel(II) malonate system allowed the use of the pressure jump technique to study the solvent effect on the thermodynamic and kinetic properties of the system. Small amounts of dioxane were used to vary the solvent properties because of its complete misicibility with water, low dielectric constant, and neutral nature. The variations in the kinetic and thermodynamic parameters of the nickel(II) malonate system in the various water-dioxane solvent systems are explained on the basis of the solvent structure promotion and breaking ability of dioxane. The equilibrium constants of nickel(II) malonate at different temperatures and in the various water-dioxane systems were determined from spectrophotometric data.Item A kinetic and thermodynamic study of some lanthanide (III) complex formation reactions(1973) Yun, Sock Sung; Bear, John L.; Murray, Christopher B.; Wendlandt, Wesley W.; Wentworth, Wayne E.; Geanangel, Russell A.The stability constants for the formation of several one-to-one lanthanide (III) tartrate complexes have been determined at different temperatures. The rate constants for the formation of lanthanide (III) tartrate and oxalate complexes have also been obtained at different temperatures. The variation of thermodynamic parameters as a function of atomic number obtained in this study for lanthanide (III) tartrate complexes are explained in terms of the difference in hydration numbers between the lighter and heavier lanthanide elements. The kinetic parameters for the lanthanide (III) tartrate and oxalate systems are compared to those of other lanthanide systems reported in the literature. It is found that the structure of the ligand is significant in lanthanide complex formation reactions. For the lanthanide monodentate complexes such as the nitrates, sulfates and acetates, the reaction rate is controlled by the rate of water exchange of the cation, whereas for the lanthanide complexes with polydentate ligand anions such as the oxalate, tartrate and CyDTA (cyclohexylenediaminetetraacetate), the reaction rate is primarily determined by the chelate formation step. The lanthanide murexides and anthranilates which are monobasic polydentate ligand complexes may be an intermediate case between the above two cases.Item A kinetic and thermodynamic study of the complexation of tetra-[mu]-boxylatodirhodium(II) with some selected ligands(1975) Das, Kamalendu; Bear, John L.; Wendlandt, Wesley W.; Cox, James R., Jr.; Kimball, Aubrey P.; Geanangel, Russell A.The kinetics and thermodynamics of the formation of 1:1 and 1:2 adducts of Rh[lowered 2](O[lowered 2]CR)[lowered 4], where R = CH[lowered 3], CH[lowered 3]OCH[lowered 2] or CH[lowered 3]CH[lowered 2], and ligands, 5'-AMP, L-histidine, DL-methionine, imidazole and pyridine, have been studied at 25[degrees]C in a phosphate buffer of ionic strength 0.1 and pH 7.40, using temperature-jump and 'entropy titration' techniques. The stability constants, enthalpies, and entropies of reactions indicate that the Rh-L (axial) bonding has some ir-interaction. Thus, rhodium(II) methoxyacetate has been found to form the most stable adduct with pyridine which has the highest ir-acceptor ability of all the ligands studied. The kinetic study indicates that the reactions with the nitrogen donor ligands are describable by Eigen's mechanism. Of the three carboxylates, rhodium(II) propionate has the highest rate of reaction with all of the ligands. The variation of the rate with changing R group in the parent carboxylate has been explained by its desolvating effect on the substrate. DL-methionine shows a large ligand effect which can not be explained by the S[lowered N]1IP mechanism.Item A kinetic study of some ligand substitution reactions(1967) Lin, Chin-tung; Bear, John L.; Wendlandt, Wesley W.; McElrath, Eby N.; Whitcomb, Margaret R.The rate constant for the formation and dissociation of the one-to-one complexes of nickel with malonate and succinate ligands and magnesium with oxalate ligand have been determined by a pressure-jump technique. The rates were determined at different temperatures and the activation parameters calculated. The results indicate that within experimental error there is no change in the activation parameters resulting from a change in properties of the ligand and they are consistent with a model in which the rate-determining step is the elimination of a water molecule from the inner hydration shell of the metal ion.Item A kinetic study of some rare earth ligand substitution reactions(1967) Graffeo, Anthony John; Beas, John L.; Becker, Ralph S.; Fuchs, Richard; Knopp, Paul J.The solution chemistry of the rare earth ions has been the subject of many discussions in the chemical literature. This is the result of the unusual variations observed in the stability of rare earth complexes with varying atomic number of the central ion involved. This type of behavior has also been observed in a number of independent thermodynamic studies of different rare earth complexes. A number of suggestions have been advanced in explanation of these variations. In an attempt to clarify the situation with respect to these complexes, the kinetics of the complex formation reactions between rare earth ions and the anions derived from acetylacetone and oxalic acid were studied by a relaxation technique—the pressure-jump method—which depends on the behavior of the equilibrium system after a sudden change in external conditions. Rate constants for the reaction of the anions with many of the rare earth ions were obtained and, in addition, activation parameters were determined for several of the rare earth/oxalic acid systems. These data are interpreted in terms of a model for the hydrated ions and variations are explained in terms of changes in solvent structure. The model suggested is shown to correllate well with a large body of experimental data.Item A mass spectrometric investigation of B-N bond association energies in the amine-borane system(1973) Emmel, Robert Henry; Geanangel, Russell A.; Veillon, Claude; Zlatkis, Albert; Kimball, Aubrey P.A four part study of boron-nitrogen bond dissociation energies in a series of borane adducts of trimethylamine is reported. The first part involves a study of the low temperature thermal properties (290[degrees]K to 320[degrees]K) of trimethylamine-borane. The quantities measured include enthalpy, free energy, entropy, and the dissociative equilibrium constant for the reaction 2(CH[lowered 3])[lowered 3]NBH[lowered 3] ---> 2(CH[lowered 3])[lowered 3]N + B[lowered 3]H[lowered 6]. The B-N bond dissociation energy was calculated and found to be in good agreement with measurements made by mass spectrometry. The 70, 15 and 10 eV mass spectra of (CH[lowered 3])[lowered 3]N, (CH[lowered 3])[lowered 3]NBH[lowered 3], (CH[lowered 3])[lowered 3]NBD[lowered 3], (CH[lowered 3])[lowered 3]NBH[lowered 2]F, (CH[lowered 3])[lowered 3]NBH[lowered 2]Cl, (CH[lowered 3])[lowered 3]NBH[lowered 2]Br, (CH[lowered 3])[lowered 3]NBH[lowered 2]I, (CH[lowered 3])[lowered 3]NBHBr[lowered 2], (CH[lowered 3])[lowered 3]NBHF[lowered 2], (CH[lowered 3])[lowered 3]NBF[lowered 3], (CH[lowered 3])[lowered 3]NBCl[lowered 3] and (CH[lowered 3])[lowered 3]NBBr[lowered 3] were recorded. Metastable peaks common to all spectra were attributed to transitions involving only the trimethylamine portion of the adducts. Fragmentation schemes were not proposed due to the lack of supportive evidence. Trends in ion abundances are discussed. A computer of average transients is developed, and discussed, for appearance potential measurements where sample pressure fluctuations are a problem. Its applicability is tested by measuring the molecular ionization potential for trimethylamine-borane and the B-N bond dissociation energy for trimethylamine-borane and trimethylamine-trifluoroborane. A comparison in experimental results is made between Morrison's second differential method and Warren's extrapolated voltage difference technique. A systematic study of boron-nitrogen bond dissociation energies in compounds of the form (CH[lowered 3])[lowered 3]NBH[lowered 3-y]X[lowered y] (X represents F, Cl, Br, I) was undertaken. The state of the BX[lowered 3] moiety (sp[raised 3] vs sp[raised 2]) at the completion of clevage was investigated and it appears that dissociation occurs without complete reorganization. Therefore, a term representing the reorganization energy was not included in calculation of bond dissociation energies A comparison of methyl proton ((CH[lowered 3])[lowered 3]NBH[lowered 3-y]X[lowered y]) chemical shifts and boron-nitrogen bond strengths were made. It showed that nmr chemical shifts cannot be depended on to reflect relative adduct strengths except where very large differences occur such as with (CH[lowered 3])[lowered 3]NBF[lowered 3] and (CH[lowered 3])[lowered 3]NBBr[lowered 3].Item A micro-extraction of volatile metabolites from body fluids for analysis by high resolution gas chromatography and GC-MS(1976) Stafford, Michele Lee; Zlatkis, Albert; Welch, Steven C.; Bear, John L.A solvent extraction method for sampling of volatile metabolites from human biological fluids developed by Zlatkis and Andrawes (45) was tested using plasma, urine, breast milk, and amniotic fluid collected from postpartum females and neonate on day 1 or soon after, depending on the fluid. The technique requires only 100 [mu]l plasma, 3 ml urine, 20 [mu]l breast milk, and 500 [mu]l amniotic fluid to be extracted with 500 [mu]l, 1 ml, 100 [mu]l, and 750 [mu]l ether, respectively, after saturation of the fluid with ammonium carbonate. The centrifuge tube containing the mixture is vortexed, centrifuged, revortexed, and centrifuged. The supernant fraction is distributed by a tubular syringe equipped with a 5" 22g needle onto glass wool contained in a tube that can be fitted directly into the injection port. After stripping the ether from the glass wool with helium, the tube is put into the inlet port. The volatile compounds are desorbed at 240°C into a stainless steel pre-column trap submerged into liquid nitrogen. After 15 minutes, gas chromatographic analysis is begun. The procedure is rapid, reproducible, requires only small volumes of biological fluids; thus, its use as a diagnostic test for pathological disorders is promising.Item A new model for the ground state potential energy curves of diatomic molecules(1985) Furet, Pascal; Matcha, Robert L.; Matcha, Robert L.; Ignatiev, Alex L.; Kevan, Larry; McCauley, Joseph L.A new model for the ground state potential energy curves of heteronuclear diatomic molecules is presented. In this model, applicable equally to covalent and ionic bonds, the total potential energy is decomposed into a covalent and an ionic component whose respective contributions are determined by a quantity [function], called bond polarity, which is an accurate measure of the ionic character of a bond. The ionic part of the energy is modeled by the Rittner potential, derived using the implicit perturbation theory formalism, while the covalent part is represented by an empirical potential energy function whose parameters are related to atomic constants obtained from the equilibrium spectroscopic properties of the homonuclear diatomic molecules corresponding to the atoms forming the heteronuclear molecule. The new model is applied in detail to the alkali halides. Employing the Hulburt-Hirschfelder potential energy function to represent the covalent component of the energy, significant improvement in the predicted values of the spectroscopic constants of these molecules is achieved over the earlier models which all consider the alkali halides 100% ionic molecules. An expression of the model in terms of atomic and ionic constants only is obtained by decomposing the repulsive part of the ionic component of the energy into singleion contributions according to an arithmetic mean rule related to ionic radii. The model is also applied to some essentially covalent heteronuclear molecules containing two alkali or halogen atoms. Satisfactory agreement with experiment is found and in many instances the results are superior to ab initio calculation results.Item A novel rearrangement of substituted phenylhydroxylamines(1970) Nolen, Robert L.; Cox, James R.; Geanangel, Russell A.; Willcott, Mark Robert, III; McElrath, Eby N.The rearrangement in different solvents of a number of substituted phenyl hydroxyl amines has been investigated. Kinetically, the N-acyl-N-phenylhydroxyl amines show a great sensitivity to electronic changes in the molecule. Electron withdrawing substituents decrease the rate, and electron donating substituents increase the rate markedly. In all compounds investigated, 0-dichloroacetyl-N-acetyl-N-(4-methylphenyl)hydroxyl amine and 0-di chioroacetyl-N-acetyl-N-phenylhydroxyl amine, two different compounds could be isolated depending on whether or not a base was present. The compound always isolated when no base was present was the kinetically controlled product X or XIII. The second product was the thermodynamically more stable product XI or XIV. The structure of the kinetically controlled product has been shown to be a novel one. Oxygen-18 tracer studies have shown that the rearrangement of O-dichioroacetyl-[raised 18]O-N-acetyl-N-(4-methylphenyl)hydroxyl amine rearranges in neat solution by an ion pair mechanism, whereby the oxygen-18 strategically placed in the di chioroacetyl carbonyl group was mixed exactly half and half with the phenyl hydroxyl amine oxygen. The rearrangement of O-dichioroacetyl-[raised 18]O-N-acetyl-N-phenylhydroxyl amine in chloroform solution occurred by transfer of all the labelled oxygen to the ortho position. This result indicates a change in mechanism from that of the 4-methyl compound. In dichloroacetic acid, O-dichloroacetyl-[raised 18]O-N-acetyl-N-phenylhydroxyl amine rearranged by three different pathways; one intermolecular, one cyclic, and the third by an intramolecular process. Just by changing the ring substituents, two different mechanisms were detected. Also, the change in solvent produced a marked change in mechanism. Therefore, the solvent and electronic effects indicate a very complex and delicate system.Item A preconcentration method and a new adsorbent for trace organic analysis in environmental samples(1987) Yao, Chien-Chang David; Zlatkis, Albert; Wentworth, Wayne E.; Kadish, Karl M.; Fuchs, Richard; Middleditch, Brian S.An innovative approach for on-line preconcentration and trace organic analysis is described. A new adsorbent can directly collect organics in aqueous samples from 1 [microliter] to 1 ml (It can be expanded to 100 ml or 1 1.) followed by thermal desorption and analysis by a capillary column in gas chromatography. Problems of interference from water, column deterioration, detector limitation, and flow rate differences between thermal desorption time and analyses time are not in the new method. Graphite fluoride, (-(C2F)n-), is the new adsorbent in this study. Graphite fluoride can adsorb trace organics such as halocarbons in aqueous samples at the part per billion level. With this technique, it should be possible to achieve analysis at the part per trillion level with a conventional flame ionization detector, and lower levels with an electron capture detector. This represents a significant improvement in sensitivity over past methods. The new procedure lends itself to automated systems. It may also be possible to eliminate the cold trap between the thermal desorption and analysis steps.