Showing papers in "Journal of Mass Spectrometry in 1978"

Separation and analysis of molecular species of mycolic acids in Nocardia and related taxa by gas chromatography mass spectrometry.

Abstract: The gas chromatographic separation and mass spectrometric identification of mycolic acids ranging from C28 to C68 in Nocardia and related acid-fast groups of bacteria was established. Using this method, the molecular species of mycolic acids were clearly separated as the trimethylsilyl (TMS) derivatives of the methyl esters, according to their total carbon numbers. From the ions produced by gas chromatography mass spectrometry, the total carbon and double bond numbers were determined, while the straight and branched chain structures were identified by the mass fragment ions due to C2 ∼ C3 cleavage [RCHOSi(CH3)3]+, and C3 ∼ C4 cleavage [(CH3)3SiOCHCH(R′)COOCH3]+, respectively. Based on the molecular species composition, the average carbon numbers of the mycolic acids from 16 strains of Nocardia and related taxa (Mycobacterium rhodochrous complex and Gordona bronchialis) were determined. Each species of bacteria was demonstrated to possess a characteristic profile of mycolic acid composition, and they were shown to be classified approximately into at least four groups: (1) C28 to C48 (average carbon numbers C33 ∼ 38) mostly saturated for Nocardia erythropolis and several ‘Mycobacterium rhodochrous complex’; (2) C34 to C50 (average C43 ∼ 34) monoenoic and dienoic for N. rubra, N. corallina and N. lutea; (3) C44 to C58 (average C51 ∼ 52) monoenoic to tetraenoic for N. asteroides and ‘true’ nocardiae; (4) C56 to C68 (average C62 ∼ 64) monoenoic to pentaenoic for N. polychromogenes and Gordona bronchialis. The results indicate that the structural determination of mycolic acids by gas chromatography mass spectrometry can be one of the most useful criteria for the chemotaxonomy of Nocardia and related bacteria.

Abnormal metabolites of isoleucine in a patient with propionyl-CoA carboxylase deficiency.

Abstract: A number of previously unrecognized abnormal metabolites have been identified and quantitated in the urine of a patient with an inherited deficiency of propionyl-CoA carboxylase. These included the isoleucine metabolites 2-methyl-3-hydroxybutyric acid and 2-methylacetoacetic acid. These isomers 3-hydroxyvaleric acid and 3-oxovaleric acid were found, which may be products of the condensation of propionyl-CoA with acetyl-CoA catalyzed by 3-oxoacyl-CoA thiolases. Following a load of isoleucine, 2-methylbutyrylglycine was identified. This metabolite has not previously been observed in man.

Quantitative determination of nifedipine in human plasma by selected ion monitoring.

Abstract: A highly sensitive and specific method for the determination of nifedipine in plasma is described. Nifedipine was oxidized to its pyridine analogue with nitrous acid and determined by selected ion monitoring. Deuterium labeled nifedipine was used as an internal standard. Plasma levels as low as 5 ng ml-1 were measured. The usefulness of the method was demonstrated by obtaining plasma concentration curves for humans after an oral dose of 10 mg.

Potential energy profiles for unimolecular reactions of organic ions: [C3H8N]+ and [C3H7O]+

Abstract: The unimolecular decompositions of two isomers of [C3H8N]+, and , are discussed in terms of the potential energy profile over which reaction may be considered to occur. The energy needed to promote slow (metastable) dissociations of either ion is found to be less than that required to cause isomerization to the other structure. This finding is supported by the observation of different decomposition pathways, different metastable peak shapes for C2H4 loss, the results of 2H labelling studies, and energy measurements on the two ions. The corresponding potential energy profile for decomposition of the oxygen analogues, and , is compared and contrasted with that proposed for the [C3H8N]+ isomers. This analysis indicates that for the oxygen analogues, the energy needed to decompose either ion is very similar to that required to cause isomerization to the other structure. Consequently, dissociation of either ion is finely balanced with rearrangement to the other and similar reactions are observed. Detailed mechanisms are proposed for loss of H2O and C2H4 from each ion and it is shown that these mechanisms are consistent with 2H and 13C labelling studies, the kinetic energy release associated with each decomposition channel, the relative competition between H2O and C2H4 loss and energy measurements.

Collisional activation spectra of [M + Li]+, [M + Na]+ and [M + K]+ ions formed by field desorption of some monosaccharides

Abstract: The collisional activation spectra of monosaccharide ions formed by [Li]+, [Na]+ and [K]+ ion attachment under field desorption conditions are reported. It is shown that the elimination of the alkali ions is determined by the alkali ion affinities of the molecules (M) and competes with a fragmentation of M which is almost independent of the alkali ion attached. Correspondingly the alkali ion is predominantly retained in the fragment ions. The usefulness of this method for the differentiation of underivatized isomers is demonstrated.

Recognition of functional groups by chemical ionization mass spectrometry

Abstract: A means of recognition of functional groups in organic molecules using chemical ionization mass spectrometry is described. Mass spectra of 34 C27-steroids using methane, isobutane and ammonia as reagent gases are recorded and correlations with structure proposed. Ammonia chemical ionization spectra are most instructive, generally yielding abundant ions of four types: an ammonium adduct [M+ NH4]+, an ammonia displacement ion [M + NH3 - X]+, a protonated molecular ion [M + H]+ and an elimination ion [M - X]+. Both the [M + H]+ and [M - X]+ ions appear to derive from the ammonium adduct [M + NH4]+, and the ion [M + NH3 - X]+ derives by a nucleophilic displacement of an elimination fragment X by neutral ammonia. Steroid ketones and olefins give predominantly [M + NH4]+ and [M + H]+ ions, whereas alcohols and esters give a three-component pattern of [M + NH4]+, [M + NH3 - X]+ and [M - X]+ ions. Spectra derived using methane or isobutane as reagent gas contain three major ion types: the protonated molecular ion [M + H]+, the hydride abstraction ion [M - H]+ and the elimination ion [M - X]+. Steroid ketones give the [M + H]+ion predominantly; the olefins give both [M + H]+ and [M - X]+ ions. Steroid alcohols give [M + H]+, [M - X]− ions. Recognition by these means of functionality in nonsteroid compounds appears also to be possible.

Selected metastable peak monitoring: a new specific technique in quantitative gas chromatography mass spectrometry.

Abstract: Using the combined electrostatic analyser-magnet scan facility of a double focusing mass spectrometer, the daughter ion peak for the fragmentation, [M-57]+ leads to [M-57-76]+, of a 5alpha-dihydrotestosterone tert-butyl-dimethylsilyl ether was monitored during gas chromatography mass spectrometry. The detection limit was approximately 20 pg. The steroid was detected by this method in an extract of human blood plasma.

Mass spectrometry of N‐nitrosamines

Abstract: The preparation of a series of N-nitrosamines for carcinogenicity studies presented an opportunity to study mass spectral fragmentation schemes in detail. Condensed spectra are listed for 146 N-nitrosamines of widely differing structures, including nitroso derivatives of commercial drugs and insecticides. Aliphatic nitrosamines were generally characterized by molecular ions and loss of OH. Subsequent fragmentation via alpha-cleavage is similar to that of aliphatic amines. The loss of OH is believed to result in a cyclic ion. Subsituted aliphatic nitrosamines varied in fragmentation schemes with structure and position of the substitutent groups. However, most showed alpha-cleavage at some point in fragmentation. When substituted with aromatic groups prominent peaks due to the aromatic moiety were observed. The alicyclic nitrosamines showed losses of NO, NOH and OH and subsequent alpha-cleavages. Nitrosamides were characterized by rupture of the carbonyl to nitrogen bond. Spectra of substituted ureas usually showed charge retention by the carbonyl fragment, while carbamate esters showed ions from both fragments.

Metabolic N-oxidation of 3-substituted pyridines: identification of products by mass spectrometry.

Abstract: The mass spectral characteristics of the N-oxides of a range of 3-substituted pyridines, and of quinoline and isoquinoline, are described. The molecular ion is the base peak in the majority of cases, provided that thermolysis is minimized when using the direct probe or gas chromatography inlets. Chromatographic and mass spectral evidence is presented which indicates that biological oxidation of the heteroaromatic nitrogen of 3-substituted pyridines is a route of metabolism in vivo and in vitro.

A quality index for reference mass spectra

Abstract: A numerical rating for evaluating the quality of reference mass spectra used for retrieval and interpretive applications is proposed. The overall quality index is the product of seven quality factors: (1) source of the spectrum; (2) ionization conditions; (3) higher molecular weight impurities; (4) illogical neutral losses; (5) isotopic abundance accuracy; (6) number of peaks; and (7) lower mass limit of peaks. For quality factor 6 the number of peaks of abundances ≥1% was found to correspond to 15 more than the number of atoms in the molecule with a correlation coefficient of 0.482. The program has been found useful in preparing a data base of 41429 mass spectra; for the majority of spectra judged to be unsatisfactory by the program this arose from a low quality factor 6 value (too few peaks).

Electrohydrodynamic ionization mass spectrometry of biochemical materials

Abstract: Electrohydrodynamic ionization mass spectrometry has been applied to a range of biochemical materials dissolved in glycerol with NaI as electrolyte. Sugars (glucose, sucrose, raffinose), nucleosides (adenosine, thymidine, uridine), a tripeptide (glutathione) and an aminocyclitol antibiotic (neomycin) have been analyzed. Unambiguous analysis of a multicomponent solution has been demonstrated. All samples yielded several quasimolecular ions involving either proton or cation attachment to clusters of sample and/or solvent molecules. Unlike other techniques such as field desorption, electrohydrodynamic ionization is not observed to cause fragmentation of sample molecules. The mass spectrometer was operated so as to analyze only those ion clusters which had not undergone decomposition processes; under these conditions, most materials are ionized with similar efficiencies if the total abundance of all characteristic quasimolecular ions is considered. Information regarding the amino acid sequence of glutathione was obtained by thermal pretreatment of the glycerol solution before mass analysis. Positive and negative ion spectra give complementary information which can resolve potential ambiguities regarding the exact composition of quasimolecular ions. Electrohydrodynamic ionization mass spectrometry should be applicable to materials which cannot be ionized by other methods.

Hydrogen rearrangement in molecular ions of alkyl benzenes: Mechanism and time dependence of hydrogen migrations in molecular ions of 1, 3-diphenylpropane and deuterated analogues

Abstract: Hydrogen migrations in the molecular ions of 1,3-diphenylpropane, preceding the fragmentations to [C7H7]+ and [C7H8]+ ions, have been investigated by use of deuterated derivatives. By comparing the distribution of deuterium labels in the [C7(H, D)8]+ products from metastable molecular ions with the distribution patterns calculated for various exchange models, it is shown that the H migrations occur by two processes linked by a common intermediate: (i) exchange between hydrogen isotopes at the -methylene group and at the ortho positions of the phenyl group: (ii) exchange between hydrogen isotopes at the ortho and ortho positions in the intermediate. In these mechanisms the eight hydrogen isotopes at both benzylic positions and both the ortho and ortho positions of 1,3-diphenylpropane participate in a mutual exchange. A statistical equipartition of the hydrogen isotopes at these eight positions is not reached in metastable molecular ions, however. The distribution pattern of [C7(H, D)8]+ ions from the deuterium labelled compounds as a function of the mean number n of exchange cycles has been calculated according to this reaction model and compared with experimental results for unstable molecular ions, generated by 70 eV and 12 eV electrons, respectively, and metastable molecular ions. Good agreement is obtained for all compounds and n = 0.4-0.8 for unstable molecular ions and n = 5-8 for metastable ions. Therefore, the hydrogen exchange in the molecular ion of 1,3-diphenylpropane is a rather slow process. These results firmly establish the isomerization reaction involving the conversion of the molecular ion of 1,3-diphenylmethane to the intermediate and hence to the molecular ion of 7-(2-phenylethyl)-5-methylene cyclohexa-1,3-diene and preceding the fragmentations. The postulated intermediate is a true one which corresponds to a -complex type ion and which fragments to [C7H8]+ ions. Surprisingly, no isomerizations of the intermediate by hydrogen shifts within the protonated aromatic system (ring walks) are observed.

Identification of hydroxylated chlorodibenzo-p-dioxins, chlorodibenzofurans, chlorodiphenyl ethers and chloronaphthalenes as their methyl ethers by gas chromatography mass spectrometry.

Abstract: The methyl ethers of a number of hydroxylated (poly)chlorodibenzo-p-dioxins, chlorodibenzofurans, chlorodiphenyl ethers and chloronaphthalenes, representing all different hydroxy substitutions, were synthesized and their mass spectra investigated. With the exception of the methoxy derivatives of the chlorodibenzofurans, it appeared that the mass fragmentation patterns of the structural isomers of each class of compounds were very specific and allowed unambiguous assignment of the position of the methoxy group in the molecule. The different fragmentation patterns can be explained in terms of plausible mechanisms resulting in stable charge delocalized (oxonium) ions. Because of its diagnostic value, this method is useful in the structure elucidation of hydroxylated metabolites of pure isomers of chlorodibenzo-p-dioxins, chlorodiphenyl ethers and chloronaphthalenes.

Ion–molecule reactions of methoxymethyl cations with some organic substrates studied by ion cyclotron resonance spectrometry

Abstract: The reactions of methoxymethyl cations generated from dimethyl ether with propene, butene-2, vinyl methyl ether, acetaldehyde and acetone have been studied. The collision complexes, generated with the olefines, may eliminate an olefine, a methanol and a formaldehyde molecule as shown by double resonance experiments. From deuterium labelling it is found, that in the cases of propene and butene-2 the elimination of an olefine is accompanied by an extensive H/D interchange in the collision complexes, which has been shown not to occur in the long-lived reactant methoxymethyl cations if the internal energy of the methoxymethyl cations is less than 2.3 eV. The H/D interchange in these collision complexes is reduced in the elimination of methanol and is almost completely suppressed in the elimination of formaldehyde. In reactions with vinyl methyl ether, however, the eliminations of methanol and formaldehyde from the corresponding collision complexes appear to proceed with extensive H/D interchange. These observations point to acyclic collision complexes rather than 4-membered ring complexes. The collision complexes generated with acetaldehyde and acetone decompose by elimination of formaldehyde only. Deuterium labelling has shown that the formaldehyde molecule contains the original methylene group of the reactant methoxymethyl cations. In addition, 18O labelling in acetone has shown that the original oxygen atom of the methoxymethyl cations is retained completely in the eliminated formaldehyde. These observations exclude any formation of 4-membered ring collision complexes and can only be explained by acyclic complexes. Possible mechanisms of all reactions mentioned are discussed in the light of these results.

Mass spectrometric analyses and characterization of Kepone in environmental and human samples

Abstract: A specific portion of our environment has been contaminated with Kepone, or chlordecone. Additionally, some specific human exposures to high concentrations of Kepone have been confirmed. Gas chromatography mass spectrometry involving chemical ionization and high resolution mass spectrometry were used to detect, identify and confirm the presence of Kepone, Kepone photoproducts and a reduction product of Kepone in environmental and human samples. Field desorption, field ionization and electron impact mass spectrometric methods, as well as infrared and nuclear magnetic resonance techniques were used to characterize and identify Kepone hydrate and hemiketal in benzene and methanol solutions, respectively.

The determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in biological extracts by gas chromatography mass spectrometry.

Abstract: Using both gas chromatography low resolution mass spectrometry and gas chromatography high resolution mass spectrometry, 2,3,7,8-tetrachlorodibenzo-p-dioxin at the part per trillion level may be determined in pre-concentrated extracts of bovine fat, liver and milk; human milk; rats; rice; grass; soil and water. Criteria are set forth for the objective determination of detection limit, signal and noise as applied to these determinations.

A simplified technique for collecting breath CO2 for isotope ratio mass spectrometry.

Abstract: A simplified technique of collecting breath CO2 for isotopic analysis has been developed. The subject breathes into a 3 1 bag from which a 50 ml aliquot is transferred to an evacuated, septum-capped tube (Vacutainer). The sample is later withdrawn and the CO2 is cryogenically purified. No isotope fractionation is observed in samples collected in this manner. Samples have been stored up to three months without any change in the isotope ratio.

Excitation in ion–molecule collisions. A study of protonated aromatic molecules by ion kinetic energy spectrometry

Abstract: Collision induced dissociation of protonated aromatic ions formed in a chemical ionization source has been studied using the technique of mass analyzed ion kinetic energy spectrometry. The observed fragmentations are concordant with those seen in the photodissociation spectra of the same ions with one significant exception. Loss of H is always a major collision induced dissociation process but is not observed in photodissociation spectra. This differences is not due to differences in the total amount of energy transferred in ionic excitation but to differences in the form in which the energy is supplied. Collision induced dissociation can lead to processes forbidden in photoexcitation, particularly those associated with electron unpairing in violation of the eveneven+even rule for fragmentations.

Determination of double bond positions in fatty acids with conjugated double bonds

Abstract: The positions of the double bonds in fatty acids with conjugated double bonds may be determined by mass spectrometry of the methyl esters of their trimethylsilyl ether derivatives obtained by hydroxylation of the double bonds followed by silylation of the resulting polyols. The method has been applied to trans-9,trans-11- and trans-10, trans-12-octadecadienoic acid.

Mass analysed collisional activation mass spectra of organic salt cations produced by field desorption linked magnetic and electric field scanning

Abstract: The collisional activation mass spectra of some organic salt cations produced by field desorption are reported. The principal fragmentations of these ions are discussed. The collisional activation mass spectra were obtained, with good mass resolution, by linked scanning of the electric and magnetic fields in a double focusing mass spectrometer.

Negative ion mass spectroscopy of natural products. VIII—α-Amino acids

Abstract: The negative ion mass spectra (2-4 eV) of twenty free alpha-amino acids have been investigated and compared with the respective low voltage positive ion mass spectra (6-16 eV). The important fragmentation processes are discussed.

Hydrogen migrations in mass spectrometry. VI—the chemical ionization mass spectra of substituted benzoic acids and benzyl alcohols†

Abstract: The H2 and CH4 chemical ionization mass spectra of a series of series of substituted benzoic acids and substituted benzyl alcohols have been determined. For the benzoic acids the major fragmentation reactions of the protonated molecule involve elimination of H2O or elimination of CO2, the latter reaction involving migration of the carboxylic hydrogen to the aromatic ring. For the benzyl alcohols the major fragmentation reactions of [MH]+ involve loss of H2O or CH2O, analogous to the CO2 elimination reaction for the benzoic acids. It is shown that the CO2 and CH2O elimination reactions occur only when a conjugated aromatic ring system is present, and that for the carboxylic acid systems, methyl groups and, to a lesser extent, phenyl groups are capable of migrating. The only discernible effect of substituents on the fragmentation of [MH]+ is an enhancement of the H2O loss reaction in the benzoic acid system when an amino, hydroxyl, or halogen substituent is ortho to the carboxyl function. This ‘ortho’ effect, which differs in scope from that observed in electron impact mass spectra, is attributed to an intramolecular catalysis by the ortho substituent of the 1,3 hydrogen migration in the carbonyl protonated acid followed by H2O elimination. Apparently, this route is favoured over the direct elimination of H2O from the carbonyl protonated acid, since the latter has a high activation energy barrier because of unfavourable orbital symmetry restrictions.

Field desorption mass spectrometry of 1-methylpyridinium salts

Abstract: Quaternary pyridinium salts were investigated by field desorption, field ionization and electron impact mass spectrometry. Thermal decomposition of the salts under field desorption conditions was found to give very abundant volatile products, identified as the dihydro analogues and the ‘methides’ of the cations. The formation of the volatile compounds, especially those with molecular weights corresponding to those of the (cation −1), (cation +1) and (cation +13) was studied in detail by deuterium and 13C labelling experiments.

In‐beam electron impact mass spectrometry of amino sugars

Abstract: Characteristics of in-beam electron impact ionization mass spectra of several amino sugars, which give barely detectable molecular ion peaks by the use of conventional direct inlet probes, are described. The spectra of these compounds almost always exhibited the M + 1 peak and the spectral features were apparently a combination of those of the conventional electron impact spectrum and some major peaks originating from the M + 1 ions. In the case of neamine, effects of the measurement conditions such as the source temperature, ionizing voltage, the position of the sample and time factors on the intensity of the M + 1 peak were examined. When the samples were mixed with ammonium chloride, the M + 1 peaks in the in-beam spectra were completely suppressed, while with aqueous ammonia, the abundance of the M + 1 peaks in creased by several times.

Evidence for a [2+4] cycloaddition in the ion‐molecule reaction of ionized 1,3‐butadiene with vinyl ethyl (methyl) ether in the gas phase

Abstract: By use of deuterium labelling it is shown that the radical cation of 1,3-butadiene reacts with vinyl methyl (or ethyl) ether in the gas phase through a [2+4] cycloaddition reaction. This leads to an excited collision complex of ionized 4-methoxy- (or ethoxy) cyclohexene, which expels mthanol (or ethanol) through a 1,3 elimination, as does 4-methoxycyclohexene itself upon electron impact. The spectrum of daughter ions produced by collision induced decomposition of the resulting ion with m/e 80 has been compared with spectra produced by the collision induced decompositions of the m/e 80 ions given by 1,3-cyclohexadiene, 1,4-cyclohexadiene, 1,3,5-hexatriene and the [M–MeOH] ion from 4-methoxycyclohexene.

The consecutive loss of two H2O molecules from protonated 1,2‐ and 1,3‐ cyclohexanediols in the gas phase: An example for the incidence of skeletal rearrangement in chemical ionization mass spectrometry

Abstract: The consecutive dehydration of protonated molecules [MH]+ of 1,2- and 1,3-cyclohexanediols (cis and trans isomers) by loss of two H2O molecules has been investigated. Analysis of 2H labelled compounds showed that loss of the first H2O molecule represents a simple heterolysis, i.e. a dissociation without exchange of hydrogens between O—H and C—H bonds. Subsequent elimination of the second H2O molecule in the process [MH–H2O]+[MH–2H2O]+ followed several competing paths. The two major ones corresponded formally (with reference to an intact 6-ring skeleton) to 1,3- and 1,4-eliminations; in comparison, the alternative 1,2-elimination is only a minor route at most. At least for the 1,3-elimination, water loss from the [MH–H2O]+ ions is not direct, but is associated with skeletal rearrangement, most probably of the Wagner-Meerwein-type, effecting contraction of the 6- to a 5-membered ring.

Use of a new silylating agent for separation of bile acids and cholesterol by selected ion monitoring with the computer controlled intensity matching technique.

Abstract: Dimethylethylsilyl ether derivatives of human biliary bile acid ethyl esters and cholesterol were separated completely by gas chromatography and selected ion monitoring by use of the mixed stationary liquid phase of OV-101 and Dexsil 300GC (1:1). These derivatives could be prepared easily and subjected directly to gas chromatography mass spectrometry. Dimethylethylsilyl ethers of bile acids ethyl esters were eluted in regular order according to the number of hydroxyl groups when used with the non-polar stationary liquid phases. Lithocholic acid, a minor component of human bile, was identified easily by selected ion monitoring with the computer controlled intensity matching technique.

Determination of lithium in microlitre amounts of human body fluids at therapeutic and normal levels by stable isotope dilution and field desorption mass spectrometry.

Abstract: The use of field desorption mass spectrometry for the determination of lithium in body fluids at therapeutic levels--ppm region--as well as at the normal level--ppb region--has been developed. The use of a stable isotope enriched internal standard, together with the outstanding sensitivity of field desorption for alkali cations and the high specificity of mass spectrometry, allows a quantitative determination of lithium in microlitre amounts of body fluids, such as plasma, saliva and urine. The assay allows a determination of lithium even at ultratrace concentrations where routine spectroscopic procedures cannot be applied. Analysis of plasma required a simple protein precipitation, whereas saliva and urine could be analysed without treatment. The precision of the data obtained ranged from 2--10%. The time consumption for one analysis in routine work is about 20--30 min.

Laser assisted field desorption mass spectrometry

Abstract: The method of indirectly heating the emitter wire with a laser is introduced into field desorption mass spectrometry. Use of this method results in improved sensitivity, more reliable high resolution performance, and extension of field desorption mass spectrometry to the area of high temperature chemistry.

Characterization by three-dimensional representation of sequential transitions of metastable ions in a double focusing mass spectrometer

Abstract: The ion currents due to products of selected ion reactions of toluene and 3-chlorophenol, occurring in the source or flight tube of a double focusing mass spectrometer for which the electric sector precedes the magnetic sector, have been represented by plotting them against two variables that reflect independently the effects of the sectors. The daughter ion produced from the molecular ion of 3-chlorophenol that decays by sequential losses of CO in the field free region preceding the electric sector and Cl˙ in the field free region preceding the magnetic sector gives rise to a peak with a distinctive shape on the resultant three-dimensional surface. A peak due to the daughter ion arising from the corresponding sequential losses of H˙ and C2H2 from the molecular ion of toluene could not be detected. A portion of the ion kinetic energy spectrum which would be recorded by a detector at the energy resolving slit is derived from the surface for 3-chlorophenol and is in satisfactory agreement with a published spectrum.