Gas Chromatography

quent to the excellent review of Hardy ... GC include that of Scott (202) on new ..... ponents to high speed chromatography were discussed by Davis (5...
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Review of Fundamental Develorrments in Analysis

Gas Chromatography Stephen Dol Nogare

E. 1.

du Pont de Nemours & Co., Inc., Wilmington, Del.

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HIS review is confined to the literature dealing with gas chromatography (GC) which has appeared subsequent to the excellent review of Hardy and Pollard (96). The technique-centered aspects of these articles will be considered mainly. A comprehensive review covering both fundamental and applied aspects would approximately double the amount of literature cited. The ANALYTICAL CHEMISTRYapplied revieas ( 7 ) contain a good deal of information on the application of GC to specific problems of air pollution, petroleum, coatings, food, etc. Other reviews dealing with many aspects of GC include that of Scott (202) on new developments, Ray (181) on general principles, Purnell (175), Phillips (172), and Clough (43) on theory and apparatus, general reviews by Hausdorff (99) and Magritte (162), a review of the kinetic and pIate treatments by Trevino (218), and Harris (97) who reviewed GC from the viewpoint of the analytical chemist. Reviews of meetings devoted to new work in GC also have been published (62, 68). The new books dealing wholly with GC and its application are the second edition of Keulemans (131), which has been expanded to include recent developments in capillary columns and detectors, a new book edited by Pecsok (169) based on the University of California GC course, and a book by Bayer (16), which is designed as a reference for the applications of GC to the analysis of a wide variety of practical problems. A sizable section on GC is included in the book on new analytical techniques by Jones (1.21) and a manual, edited by Johns (116),recently has appeared.

PACKED COLUMNS

E5ciency. The distribution of a solute, in a plate treatment of the column derived by Jaulmes and Mestres (114), gives results in good agreement with the orighal Martin theory. Giddings (84) has sought to develop a common basis for theories of chromatography-Le., the various rate and plate theories. The rate theories (material conservation, stochastic) were shown to lead to the same peak diffusion coefficient by assuming a relaxation time model and expressing the nonequilib-

rium displacement of the chromatographic peak. The height equivalent to a theoretical plate (HETP) for the plate model also was related to relaxation time model by equating H E T P / 2 to the distance between an equilibrium point moving a t a rate, R,, and the nonequilibrium point after an interval equal to the relaxation time. Said (191) has continued his theoretical treatment of the elution chromatographic process by deriving a general equation combining elution and deposition. He has considered also the difference between theoretical and experimental peaks, taking into account dead volume and finite sample size. The second paper (192) deals with the calculation of the Poisson distribution by transformation to the normal distribution for which tables are available. Charts are presented for this conversion. The terms of the van Deemter equation were used by Purnell (176) to predict the effects of column pressure, liquid phase loading, sample size, and both particle size and size distribution on column efficiency. Results of the experimental work confirmed the general validity of the equation except that negligible or negative eddy diffusion, A terms, were obtained for the most efficient columns. An explanation for the variation of A values with velocity was suggested by Giddings (86) who proposed the equation: H=-

A

1

+ b/v

to account for the eddy d8usion contribution to HETP. At high v values the contribution becomes independent of velocity and equivalent to the van Deemter A , whereas a t low u values the contribution becomes negligible. The work of Stewart et al. (909) was directed at providing a theoretical basis for pressure gradient effects on the various terms of the van Deemter equation. Two pressure functions were derived, one being the original James and Martin pressure correction. The effect of pressure is expected to be small except for large p , / p o ratios, where the A term is affected as indicated above. The determination of true column efficiency should involve the measurement of band spreading due only to the column and not to extra-column factors.

Johnson and Stross (119) have separated peak width into column and noncolumn factors, and conclude from their model that suitable corrections for the apparatus dead volume can be applied to an observed peak width. Excessive detector cell volume, particularly for diffusion cells, was shown to contribute markedly to peak asymmetry. Whatmough (232) observed a marked change in peak shape as larger amounts of methane were injected into a carbon adsorption column. Peaks changed from nearly Gaussian shape of constant half width to a skewed shape of increasing half width; linear correspondence of peak height to concentration occurred only in the regions 0 to 5Q/, and 45 to lOOyo methane, the slopes being different. The behavior observed by Khatmough was confirmed by Vizard and Wynne (224) and explained by Bosanquet (SO), who showed how peak height was related to original methane concentration in the sample for C0>20y0. Linearity below 5y0 methane was attributed to diffusion control of peak width. Liquid Phases. Various family plots of In VGus. I / T , In p o , and number of carbon atoms were prepared by Young (241) for the alkyl ketones on dinonyl phthalate columns. The 1/T and number of carbon atoms plots were linear. Ln p" plots were linear with slopes decreasing with increasing molecular weight. Young has also discussed the relative effects of branching and chain lengthening on such plots. Heats of solution estimated from In V o us. 1/T plots for benzene, cyclanes, and cyclenes were reported for the liquid phase polyethylene glycol octyl tolyl ether by Pyke and Swinbourne (177). The relationship between p" ratios and experimental retention ratios for a series of aromatic compounds on silicone oil was studied by Jentzsch and Bergmann (116). Observed deviations from expected agreement were attributed to deviations of the activity coefficient from one. Bayer (IS,14) suggested the use of a selectivity coefficient (separation factor) as a means of evaluating the specificity of a liquid phase. He points out that the ratio taken for two substances of different functionality but the same boiling point is a ratio of their activity coefficients, and serves t o VOL 32, NO. 5, APRIL 1960

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characterize the liquid phase from this standpoint. Partition coefficients from GC and both velocity ratios and boiling point depression data from equilibriumstill experiments Bere used by Warren and coworkers (229) to correlate GC and extractive distillation performance. A study of the effect of changing the chemical composition of the liquid phase on the separation of saturated and unsaturated fatty acid esters was described by Lipsky et al. (143, l & ) . Of the various polyesters investigated, those derived from short-chain dibasic acids (particularly polydiethylene glycol succinate) gave best results. This conclusion was substantiated by the experimental comparison of butanediol and diethylene glycol succinates for similar separations by Dimick and Chu (62). Orr and Callen (167)also have evaluated a number of polyester phases for the separation of fatty acid esters. These workers discussed the interaction of ester solutes with such liquid phases and suggested a compensation procedure. The exaggerated tailing which arose from association of free fatty acids n a s reduced by operation at high temperature for the higher fatty acids (18) and by the addition of a high proportion of sebacic acid to various polyester liquid phases for the lower acids (179). I n the latter case nearly symmetrical peaks were obtained. The separation of a number of complev Ca to Cshydrocarbon mixtures with selective liquid phases and liquid-modified adsorbents was demonstrated by Rijnders (187). The analysis of aqueous mixtures was reported especially successful on &p'oxypropionitrile and hexaethylene glycol dimethyl ether by Kelker (1.90) at temperatures up to 100" C. Smith (206) made a n extensive study of nine hydrophilic liquid phases for the analysis of water-containing mixtures and has discussed their applicability and limitations. High molecular weight amines were found by Zarembo and Lysyj (242) to be satisfactory for high-water samples. Resolution of racemic mixtures on mono- and dimolecular layers of optically active liquid phases was demonstrated by Karagounis and Lippold (126). Isomeric benzene and naphthalene compounds were shown t o be effectively resolved on 2,4,7-trinitrofluorenone (164), suitable for temperatures to 200' C. JanAk and Novak (112) have studied the selectivity of a number of liquid phases impregnated on a n activated sodium aluminum-silicate for the separation of gaseous paraffins and olefins from butadiene. Xitrogen and oxygen were shown t o be separated on blood from various sources (86). The retention of oxygen was characteristic of the blood used. The strong interaction between amines and molten metal stearate phases and the possi-

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ANALYTICAL CHEMISTRY

bilities for studying complex stabilities by this method were discussed by Barber and coworkers ( 9 ) . Ammonia was found irreversibly absorbed on silver salt solutions until enough ammonia was introduced to form a stable ammine after which ammonia peaks showed a plateau suggesting formations of a second, unstable ammine (66). Solid silver nitrate has been used to react selectively with sec-bromide in a short precolumn, permitting a differential analysis of secand isobutyl bromides (98). Solid Supports. An extensive study by Baker and coworkers (8) of pore size distribution and other characteristics of Celite and related supports showed that most of the liquid phase is located in the fine pores with a thin layer over the remainder of the support. Optimum characteristics for a n ideal support are: hard material, pore size of 1 micron or less, narrow particle size distribution, optimum size 275 to 300 microns. Improved peak sharpness was achieved by Zlatkis and coworkers (244) with strong aqua regia treatment of firebrick. Strong adsorption sites on supports were masked by gold or silver plating, rcsulting in improved peak symmetry (166). The great effect of adsorption sites was clearly shown by the experiments of Wolf and Ternow (239) with silica gel. A silicone coating was applied to Celite by passing dichlorodimethylsilane vapor through the support (102). The silic o w pretreated support gave polyester columns which showed good reproducibility for separations at 137' to 200' C. A solid support which is suitable for separating strongly basic nitrogen compounds was derived from the inorganic fraction of a commercial detergent impregnated with potassium hydroxide (67). A clue to the nature of adsorption effects on supports is suggested by the work of Szekely e.! al. (212) whose experiments indicate that liquids form islands on thc surface leaving uncovered areas available for adsorption. Adsorbents. The preparation of alumina of different activities (differing water contents) was studied by Scott (199) and the retention of hydrocarbons relative to activity was established. Adsorption strength and surface area for silica gel have both been derived from the retention plots of hydrocarbons (238) while the properties of the Linde 5A Molecular Sieve have been extensively studied by Janllk and coworkers (110, 111). JanAk (108) also has demonstrated that symmetrical adsorption peaks for hydrogen may be obtained by depositing palladium on Celite. Adsorption studies on various charcoals by Habgood (93) suggested that the small pores in adsorbents are a more important factor than surface area. A detailed procedure was reported for the preparation of a n active magnesium silicate which provides a

more convenient separation of the C,to CC hydrocarbons than either silica gel or di-n-ethylformamide columns (53). Surface area measurements of adsorbents and catalysts also have been made by Cremer (61) and by Roth and Ellwood (189),who have eliminated several c h s e s of experimental d a c u l t y in the original Nelsen and Eggertsen procedure. Tamaru (214) used GC to study the mechanism of surface catalysis by passing reactant and sample through the catalyst packed column and by independent measurement of the individual retention times for sample and reactant. Cremer (60) has suggested that GC be classified according to the degree to which a n adsorbent surface is modified by a condensed phase-Le., adsorption referring to unmodified surfaces, mixed adsorption referring to monolayer coatings, and multimolecular or gas-liquid partition. A theory which relates GC to static adsorption measurements has been published by Hanlan and Freeman (95). Carrier Gases. The effect of different carriw gases on high speed G C was investigated by Loyd and coworkers (150) who showed that optimum carrier gas velocity in small inner diameter columns is proportional to diffusivity of the carrier. Efficiency was in the order nitrogenghydrogen, helium, R ith hydrogen yielding equivalent chromatograms in one fourth the time required for nitrogen. The advantages of carbon dioxide for adsorption separations arising from smaller diffusion effects have been noted (223). For the analysis of trace components in a gas stream, Willis (235) used a carrier of the same qualitative composition such that greater or smaller amounts of impurities in the sample show up as positive or negative peaks, depending on their concentration relative to that in the carrier. Sample Injection. Bethea and Smutz (27, 28) reported on the dependence of efficiency and retention time on sample size. There appears to be an optimum sample size for both minimum HETP and minimum retention. hlodification of the familiar Agla syringe to permit nearly instantaneous injection of samples greater than 10 pl. was described by Sweeting (111). A bypass valve, designed to permit injection of samples with little or no back pressure from the carrier gas and suitable for operation to 250' C., also was reported (193). For the introduction of easily hydrolyzed samples, a capillary crusher has been described in detail (f23). A novel method for injecting aldehydes and ketones by flash exchange of their 2,4dinitrophenylhydrazones with aketoglutaric acid at 250" C. was developed by Ralls (178). Accurately

weighed microsamples of liquids may be injected directly on the packing by a simple capillary method (208) and openended pipets have been used for the introduction of small gas samples into a n evacuated sample port (4). Molecular Sieves were used by Tonge and Timms (21'7) to scavenge samples from low-pressure gas systems after which the adsorbed sample was introduced into a GC apparatus by heating.

CAPILLARY COLUMNS

plication of a coulometric detector to fatty acid analysis by Liberti (14.2). Skarstrom (205) described a detector which senses the transient thermal changes in a solid adsorbent induced by eluted solutes. He also described a n adsorption air drier which requires no heat for regeneration. A study of the hlellor carbon dioxide combustion detector (thermal conductivity detection) has been made by Ne1 and coworkers (163) and a modification of the Martin qas density meter, which simplifies construction, was published by Murray (161).

Methods for the preparation of capillary columns and for introducing very small samples were described by Lipsky and coworkers (145). I n this work it was noted that the Lovelock detector will sense lo-" to 10-15 mole of a n organic vapor. Zlatkis and Lovelock (244) report a sensitivity of lo-'* mole. Design considerations involved in t h e use of capillary columns have been discussed by Condon (44, 4 5 ) and some of the theoretical aspects were discussed by Condon and Golay (46). The split-stream technique for introducing extremely small samples also was described (14,,249). Application of capillary columns and the Lovelock detector t o the difficult problem of fatty acid analysis has been continued by Lipsky and coworkers (146) who cite efficiencies of 21 t o 200 theoretical plates per foot. For hydrocarbons, efficiencies of 750 theoretical plates per foot were reported (243). Nylon capillaries were shoivn t o exert little or no adsorption effect on paraffins and aromatic compounds and to exhibit cfficiencies of the order of 3/4 million plates (1000-foot capillary) (boo). Desty and coworkers (60) considered the factors contributing t o capillary coluuin efficiency through the Golay equation. They found t h a t minimum HETP values were obtained with glass capillaries, presumably because of their smoother bores. Glass capillaries are now available in 100- to 3W-foot lengths from Corning Glass Co.

DETECTION

Detectors. F o r some time i t has been recognized t h a t greater sensitivi t y t h a n shown by currently known detectors is possible, b u t t h a t t h e mayimum useful sensitivity may well be limited by other apparatus factors. Several papers have indicated the usefulness of biological detectors, the nose for supplementing thermal conductivity in cheese flavor studies (104) and the male moth t o sense active components in extracts of the female moth (16). Included among the more instrumental detector developments is a n ultraviolet absorption detector (120) and the ap-

The evaluation of detectors was considered by Johnson and Stross (118) who amplified the original treatment by Dimbat et al. t o include limit of detection and noise measurements. Young (240) has reviewed the literature on detector sensitivity and recommended pQo values (-log Q,,)t o represent detector performance satisfactorily, where Qo is the limit of detection equivalent to a stated multiple of the noise level. Similar considerations have been treated by hIcWilliam (158). Several thermal conductivity (TC) cells were reported utilizing thermistors and having low noise (162); a unit for use with either thermistors or filaments adaptable to a wide temperature range (215) was also described. Johnson and Stross (119) have pointed out the significance of the detector volume contribution to both efficiency and peak sken-ness and have suggested suitable corrections. The effect of detector response time on peak shape and therefore, resolution and efficiency, was demonstrated by Schmauch (194). The effect of pressure, flow, and temperature on differential detectors also has been discussed (135). Ray (18.2, 183) demonstrated that carrier gases of low thermal conductivity offered highest sensitivity. This conclusion was challenged by a number of workers (68, 7'8, 196, %OS. 236) who pointed out that for a constant wire temperature, carrier gases of high conductivity (helium) gave greater sensitivity with relatively constant response. It was also noted that low conductivity gases, such as argon, frequently yield positive, negative, or zcro signals, because their thermal conductivities are close to that of the solutes. Ray replied that voltage limitations imposed by the instrument frequently limit the wire temperature obtainable (184) and noted that the conductivity of monatomic gases shows a smaller increase with temperature than that of organic vapors (185). Because of the latter effect, relative sensitivity should increase with argon but decrease n-ith helium for a n increase in filament temperature. I n a subsequent treatment of T C cell response by Schmauch and Dinerstein (196), cell factors and T C factors were

fully discussed. I n this same area, Wiseman (937) has amplified his earlier treatment of heat flow in the T C cell. I n a study of the relationship of T C cell response to sample composition it was shown that peak area correlated best with volume fraction of the component in the sample over a range of conditions (215). I n other work, peak areas ere shown to correlate with mole per cent (49) and with weight per cent (48). Within a homologous series, relative T C response corresponds with molecular weight using helium as carrier (159). Accurate results (1.9%) were obtained when relative signal response values were used with a n internal standard (69). Jamieson (107) showed for vapous carrier gases that the linearity of T C response improves at high temperature. Special requirements of T C cells for application to kinetic studies (10) and process control (207) have been noted. An interesting modification of T C cells to provide the derivatives of elution curves, permitting exact location of maxima, was described by McDermott and Cooper (157). Detectors based on various ionization methods are receiving increased attention because of their suitability in conjunction with capillary columns where both small gas volumes and samples are required. Lovelock et al. ( f 4 9 ) and Evans and Wing (73) reviewed the principles and operation of the 8-ray ionization detector. A modification of this detector in which the sensed volume was reduced to about 1 J. also was described (147). Use of the 8-ray ionization detector for the differentiation of chemical types has been demonstrated by Lovelock (148). By operating the detector a t selected voltages it is possible t o make electron capture predominate for various species with resulting negative peaks. A comparison of the sensitivity of the Lovelock detector with other types has been made (105) and comprehensive construction details were published by Farquhar and coworkers (75) and Graven (90). A flame ionization detector design with two electrometer amplifier circuits was given by Thompson (216). A new radio-frequency glow detector in which the drop in direct current output is proportional to solute concentration was developed by Karmen and Bowman (128). A limit of detection of lo-'* mole was cited for this detector (129). A comprehensive study of a refined ionization gage detector was reported by Hinkle et al. (100) while extensive performance data on a similar apparatus were furnished by Guild and COR orkers (92). Radioactive Tagging. Labeling of organic compounds by exposure t o tritium gas offers interesting possibilities for the high sensitivity detection of trace components with standard VOL. 32, NO. 5, APRIL 1960

21 R

counting techniques. Dorfman and Wilzbach (64) described a relatively rapid procedure for carrying out the exchange with minimum decomposition and Nystrom et al. (166) have effectively applied it to fatty acid analysis. Ways in which isotopes may be utilized in reaction studies were discussed by Emmett (71),who also reported on apparatus for these radioactive studies, as have others (19, 156). GC was shown superior to low temperature distillation for the separations of hydrocarbon gases by means of carbon-14 tracers (127). Read-Out. Problems associated with the adaptation of read-out components to high speed chromatography were discussed by Davis (56). Scott ($01) showed the practicability of presenting entire, fast (1-minute) chromatograms on a long-persistance cathoderay tube with photographic recording for future reference. The JanAk nitrometer detector was automated to read out solute volumes directly (113). A printing integrator with a maximum counting rate of 6000 counts per minute which prints peak area and can compensate for attenuation changes was described by Claudy et al. (41). A two-pen recorder which traces both the chromatographic peak and the time integral with full range of five chart widths was developed by Doolen (63), and Perrine (170) reported a precise (0.2%) ball-and-disk integrator with a count rate of up to 60,000 counts per minute. Continuous attenuation of wide-range signals, rather than the usual stepwise reduction, was achieved by use of a coupled logarithmic slide-wire attached to the recorder (160). A computer designed for converting peak areas to percentage composition has been announced

(SI. Quantitative and Qualitative Measurements. The need for standard procedures to determine specific and relative retention volumes (188) and suggested nomenclature (35) have been pointed out. A recommendation that the width measurement in the peak height X width product be taken a t 45.4% (instead of 50%) peak height for more accurate area measurement also was made (114). The nonlinear calibration curves observed with adsorption columns have been noted (232) and explained (30). For quantitative analysis by the internal standard method, Lee and Oliver (140) recommended use of two standards for wide-range samples. Fraction collectors were described for manual (141) and automatic (137) isolation of eluted solutes. Fractions may rtlso be collected in a unit designed for reduced pressure operation (47). Techniques for the rapid identification of materials by a combination of GC, mass spectrometry, and infrared analysis have been described by Schols (I@), and problems associated with the analysis of

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ANALYTICAL CHEMISTRY

troleum gases also was described (31). Two- and three-stage analyzers were successfully used to study trace hydSocarbons in exhaust gases (103) with suggestions for extending the work to the C9 to CI2range. Another three-column system for the analysis of light hydrocarbon mixtures and carbon dioxide was reported by Claesson (40). Noble gas mixtures containing nitrogen, oxygen, and methane were successfully studied on a multiple column system with temperature adjustment as required by the sample (91). The use of a multiple (204). column system for the relatively irMicroinfrared techniques have been reversible removal of a major or troublerefined by Gallaway et al. (81) to handle some component was termed subtracthe typically small samples from GC tive chromatography by Brenner and peaks, and a small (7.5-ml.) gas cell for coworkers (32). This technique Mas this application was described by Rusused to remove oxygen on a catalystsell (190). A 22-ml. infrared cell packed precolumn with hydrogen as attached directly to the column output carrier by KrejEi et al. (I%), and for the was used by White et al. (2%) to detect removal of ethylene on a sulfuric acid 0.1 to 0.501, impurities in ethyl alcohol column by Martin (155). and 0.04 to 0.13y0 components in tolProgrammed Temperature. Reuene. Advantages in infrared examinaduced analysis time can frequently be tion of vapors rather than liquids were achieved by the use of programmed cited by Anderson (6), who noted that temperature columns for the analysis 5 pmoles of vapors or liquids boiling up of wide boiling range miutures. The to 175' C. can be estimated to 5 2 % . modification of a commercial instruHeated cells should extend the usefulment for temperature programming ness of this procedure. was reported by Wiersma and Tollefson Standard Data. Relative retention (234). Two papers have dealt with the data have been summarized by Hively design and performance of a laboratory (101) for all readily available CI to CS programmed temperature chromatoand some C, hydrocarbons on five liquid graph (54) and of a commercially availphases a t five different temperatures. able apparatus (154). Perry (171) inMethyl esters of the fatty acids were corporated a programmer in a flexible tabulated by James and Martin (106) GC apparatus. Several constant carand some 48 halides, alcohols, alderier flow controllers for use Rith variable hydes, and ketones on both a polar and temperature columns were described by a nonpolar liquid phase a t three temKnox (132) and Clough (42). The peratures were tabulated by KovAts former uted a dummy column to com(134). Terpenes and unsaturated alpensate for temperature changes and cohols and esters have been characthe latter has discussed several aspects terized by Bayer and coworkers (17) of variable temperature operation. along with a variety of phenolic comSullivan et al. (210) showed that pounds (26, 109). A wide range of nonlinear temperature p r o g r a m i n g can compounds was characterized by be achieved simply and applied with Raupp (180) who used n-pentane as the good results. Variable temperature opstandard. The retention behavior of a eration was also utilized by Adams and wide range of chemical types was tabucoworkers for the study of sulfur comlated for 10 different columns (n-penpounds ( 1 , Z ) and by Juranek (184,125) tane = 1) and graphically presented by Scholly and Brenner (197). @,@-Oxy- for the separation of hydrocarbon gases on adsorption columns. A theoretical propionitrile and hexaethglene glycol treatment of the factors involved in dimethyl ether were selected as parprogrammed temperature GC has been ticularly useful liquid phases for which given Ey Habgood and Harris (94) and the relative behavior (benzene = 1) of by Dal Kogare and Langlois (55). 77 compounds was cited (130). The application of chromathermography t o several analytical problems was reported (219, 221). SPECIALIZED OPERATION Trace Analysis. Special requirements for trace analysis by GC were Multistage. A four-stage apparatus discussed by Jones (122) with particular was designed by Bloch (29) for the reference to the use of conventional routine analysis of about 70 hydrocarequipment. An ionization detector was bons and H2, 02,NS, GO, COS,and COS used by Farrington et al. (74) to study from a single sample. The apparatus polluted atmospheres. The rembval of utilized three detectors and recorders. water from air samples without loss of A parallel two-column arrangement into oxygenated compounds was carefully which the sample is split for the deterinvestigated by these workers. The mination of 02, N2, CO2, and light pe-

complex mixtures from combined GC and mass spectrometric data also were treated (230). Gohlke (88) described his work with the time-of-flight mass spectrometer combined with a flexible GC unit for the characterization of complex organic mixtures. Applications of the same apparatus also were cited (231). The basis for a combined GC-mass spectrometric method for complex petroleum samples was the selection of a column which resolves the components according to carbon number

concentration of trace constituents was utilized for carbon dioxide in air and acetylene in ethylene (33, 34) and for methane in air (139). High Temperature. T h e design of a high-temperature apparatus for use t o 500" C. was reported by Alexander and Marsh (3) and by Wachi (225) n h o modified the original Felton instrument. Both of these reports discuss the use of inorganic salt eutectics as liquid phases. Modification of a commercial instrument for use t o 450' C. also was described (11, 12). Polyphenyl tars and asphaltenes (3, 11, 12) n-ere evaluated for high-temperature work. Preparative Scale. D e Wet and Pretorius (61) and Golay (89) have discussed the theoretical aspects of large-scale separation in packed and open columns. Golay offered theoretical support for improved efficiency with large columns with roughened inner walls and by the use of mixing regions t o smooth out variation in the rate at which the so1utc.s migrate in a column of large cross section. Columns up t o 3 inches in diameter were reported by Patrick (168) t o handle up t o 5 grams of sample. The design-of a commercial preparative scale apparatus which permits 100-fold scale-up of GC separations and which uses the column bundle arrangement was described by Johns et al. (117).- Reference to the effect of flooding on preparative scale work was made by Bens and McBride (25). Continuous Separation. T h e theoretical aspects of a system in which t h e liquid a n d gas phases move countercuirent in a helix-packed t u b e with temperature gradient were reported by Kuhn and coworkers (1.38), and demonstrated for the separation of a fatty acid mixture. A series of papers by Benedek and associates (21-24) have dealt Rith the calculation of critical parameters for the successful operation of continuous separations by the hypersorption technique. Details of a large-sca!e unit also were reported (60, 80). Continual Analysis. Use of automatic chromatographs for t h e analysis of process streams is currently widely accepted, as indicated by t h e range of commercial instruments for this purMore recently, t h e emphasis pose. has been on t h e use of process chromatographs for process control, and the general requirements for adaptation of G C t o analyzer and control functions were presented by Wall et al. (226-228). Emphasis was placed on the lack of a reliable liquid sampling valve. A chromatographic system useful for process control was described by Turner (220) and by Fourroux (76). Spectrcchromatography (77) represents a combination of ultraviolet spectroscopy and GC for the automatic analysis of

aromatics, particularly. A high-speed automatic chromatograph capable of less than 1-minute chromatograms has been reported (38, 150). A process stream analyzer also was announced by Russian viorkers (5).

apparatus fitted with flame temperature detector, which appears well suited t o student use, was described by Geldenhuis et al. (83).

LITERATURE CITED

MISCELLANEOUS

Potential usefulness of GC for the separation of inorganic compounds was shown for the transition metal halides by Wachi (225) and Freiser (79), n hile Duswalt (67) was able to resolve the acetonyl acetonates of several metal ions. The separation of a n organic acid mixture by elution with alcohol vapor in place of more conventional carriers was demonstrated by Dumazert and Ghiglione (65). Characterization of solute retention values was made by measurement of the volume of alcohol vaporized into the column. Separation by fractional codistillation in a powdered metal packed tube with helium as carrier also was performed (36). Porter and Johnson (174) have demonstrated circular GC in which the carrier is circulated by a pump. Efficiency was shown to increase continuously for a 10-foot column up to 15 cycles. The technique was used with volatile liquid phases t o determine separation factors for extractive distillation (173). Mixtures of ortho-para hydrogen (72) HP,HT, and T P (82) and HP, HD, DI, (186) have been successfully analyzed by GC. Excellent separation of the difficult pair, m- and p-xylenes, was achieved on 7,s-benzoquinoline by Desty and associates (59). The use of GC for measuring water in various pharmaceutical preparations h a s given good results according to Elvidge and Proctor (70). A unique theoretical explanation of the movement of highly radioactive gases in adsorption tubes which takes into account temperature changes due to adsorption and radioactivity was offered by Glueckauf (87). An approach to the objective measurement of odor using ionization detectors was described by Mackay (151). A rapid, accurate method for measurement of blood alcohol was reported by Maricq and Molle (163). Additional information concerning the composition of a sample can be obtained by determining the time required to backfiush the less volatile components (222). The manner in which problems in chemical kinetics may be attacked by G C was outlined by Knox (13.3) along with recommended apparatus modifications. A hand-sized G C apparatus which is stated t o have 15,000 theoretical p b t e s has been reported by the Shell Development Laboratory (39). An inexpensive, easily constructed GC

(1) Adams, D. F., Koppe, R. K., Jungroth, D. &I., 136th Meeting, ACS, Atlantic City, K.J., September 1959. (2) Adams, D . F., Koppe, R. K., Tappi 42,601 (1959). (3) . , Alexander. D.. Marsh. R. F.. I.S.A. Symposium' on 'Gas Chromatography, hfichigan State University, June 10-12, 1959. -___

(4) Amberg, C. H., Echigoya, E., Kulawic, D., Can. J . Chem. 37, 708 (1959). (5) Anders, 5'. R., Frolovskii, P. A., Remnev. V. F., Slobodkin, M. S., Khim.

i Tekhnoi. Topliv i 'Masel

4;

25 119591. (6) Andersbn, D. M. W., Analyst 84, 50 (1959). (7) Applied Reviews, ANAL. CHEM. 31, 631 (1959). (8) Baker, W. J., Lee, E. H., Wall, R. F., I.S.A. Symposium on Gas Chromatography, Michigan State University, June 10-12, 1959. (9) Barber, D. W., Phillips, C. S. G., Tusa, G. F., Verdin, A., J . C h a . SOC. 1959, 18.

(10) Bardwell, J., 2nd Alberta Gas Chromatography Symposium, Edmonton, February 13, 1959. (11) Baxter, R. A., Keen, R. T.,Atomic Energy Comm. Rept. N U - S R - 3 1 5 4

.

(June . . 1959). -- -- ,

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(22) -Ihid.. n. - r 353. --I

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(19.59).

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