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Gas chromatographic analysis of volatile components in the presence of excess of non-volatiles
SHORT’ COtiMU~ICATIOtiS
169
numbers ‘for the diatomaceous earth columns are similar, and even, if. they areklower, the separation shown on the chromatogram was good. The Teflon column, however, showed a very poor separation for the hydrocarbbns, arid a better, but., not sufficient ‘sep’aration for the alcohols.’ Five,conclusions can be drawn from these data: x. In general, the use, of Chromosorb, Celite and Chromosorb W as support material results in a similar separation, effect. 2. The use of Firebriclc has n’o advantages: it has a very high flow resistance and at the same time, no better separation effect than Celite or Chromosorb. 3. In analyzing polar compounds, the tailing (particularly for the first components of the homologous series) is considerable. with Chromosorb and Firebrick, even if, as in the case of Chromosorb, the theoretical plate number calculated for higher homologues is better. .At the same time, this polarity effect diminishes the separation among the first members of the homologous series: ‘r - ,-. 4. The specific surface area of the support material:does no: influence particularly the separation effect df the column if the surface’area is over a certain limit, and in this case the influence of the polarity is considerably~ higher. This limit seems tosbe according to our data, at about I ms/g, which is contradictory to other data! where a minimum necessary surface area of about 3 ni2/g is given. c ’ 5. The use of .Teflon as support material .is only preferable, where the extremely high ‘polarity of the sample component(s) makes ,it necessary. * t..
The Pevizin-Elkev
Cor$oratiqn, ,
Norwalk, -_
.,..
Coma. (U.S.A.) ,,
,’
.. )’
.
1 F. M. NELSEN AND I?. T. EGGERTSEN, Anal, Cl&em., 30 (Igfj5) 1357. 2. C. I?. LEE AND P, I-F, STROSS, Division of Avzalylical Clbemislry, 135th National American Chemical _ -Society, Meeting, Boston, Mass,.. U.S.&, April g, r 959. Akad. Vorlsgsges~llschaft Geest & Portig KG., Leipzig, 3 R. KAISER, Gas Ckromatographie, : .x960, p. 33. 4 D. I-I.,DEsTY (Editor), Vapoh PJtase Cltromatograpky, Butterworths, London, 1957, p. xii. Akad. Verlagsgesellschsft Ge,est & Portig KG., Leipzig, 5 R. KAISER, Gas CfrromatograpJ~lie, 1960, p. 39.
Received
March z3rd, 1960
Gas chrom+tographic in the presence
J. Clrromalog. ,’ 4 (I 960)
analysis
of volatilg
z W-1 6g
components
of excess of non-volatiles
The analysis of dissolved gases in ‘petroleum fractions lias .been the subje,ct ,of some principle. of .these .met,hods is the same : ‘a recent publications i-3. .The fundamental large .(up to I: ml) liquid sample ‘is introduced into the chromatograph; the’ heavier ‘hydI;ocarbons are adsorbed on. a trap column installed in series before the chromatographic ,cdlurnri’and~~the_ dissolved gases: are analyzed, on,.the ,latter;’ The ‘functidnal ‘schematic of, such. i unit, is given, in Fig., I. j.
C/rro?qalog., 4 (1966). 169-17~ i .:,, .,
SHORTCOMMUNICATIONS
I
SEWS
-DETECTOR
CA\~IfR
REP I
[piiikq Fig. I.
There are many limitations if the principles of this method are applied to the more general problem of the analysis of volatile components dissolved in a nonVolatile medium. The main problem is that the temperature of the instrument must be kept low;and, therefore, the undesirable condensation (or insufficient evaporation) of the solvent into the injection block or the tubes connecting it with the column will make the analysis difficult for two reasons: (I) a part of the volatiles will remain dissolved in the condensed solvent, and (2) a frequent cleaning of the equipment will be necessary. Of course, it is possible to heat this part of the instrument using separately installed heating wires, but if commercial gas chromatographs are used, this requires modification on the instrument. It should be further emphasized that, because the necessary sample volume is in most cases unusually large (I ml: at least 100 times larger than the average liquid sample used at gas chromatographic analyses), the rapid and complete evaporation of this large sample volume is still a problem even if the injection block is heated sufficiently. A further problem is the backflushing of the trap column which also requires special modification of most commercial gas chromatographs. Recently, BRENNER AND ETTRE* described a device for the analysis of trace impurities in gases by condensing the components of interest in a small column connected to the outside gas sampling valve of a commercial gas chromatograph. A simple modification of this device permits its use for the general problem of the analysis of volatile components dissolved in a non-volatile medium. The new device consists of a special trap column with a rubber septum on its top (Fig. 2). The column is filled with adsorbents similar to those described in previous papers (activated charcoal, silica gel, firebrick, etc.) or with column materials which show a much longer retention time for the solvent than for the dissolved substances to be analyzed. The large liquid sample is injected using a hypodermic syringe with a longer needle through the rubber septum directly onto the top of the column packing material (valve in’ position I). ,In’ this way, the sample is carried with the carrier gas flow through the trap column: the non-volatile solvent is adsorbed on the packing material,‘but the volatile components are purged without loss into the chromatographic J. Chvomalog.,
4 (xg6o) 169-171
SIIORT COMMUNICATIONS
=7*
SAMP INJECT . SELF - SEALING SEPTUM.
CARR I ER GAS GAS SAMPLING
R
POSITION
I
POSITION
H
;
VALVE
CHROMATOGRAPHIC COLUMN HOT WATER (OR OIL) BATH
$00 TRAP CaUMN
Fig. 2
column and analyzed there. The trap column may be conveniently heated with a water or oil bath to elevated temperatures if necessary. After finishing the analysis, the valve is to be turned to position II, and the trap column backflushed using nitrogen or air. The device has been successfully employed for the analysis of dissolved gases or light organic solvents in water. The Pevlzin-Elmer
Corporation,
Norwalk,
EDWARD W. CIEPLINSICI LESLIE S. ETTRE
Conn. (U.S.A.)
1 P. G. ELSEY, Agtal. Chem., 31 (1959) 869. J. P. PAGLIS, 2nd Riannual International Gas Clbvomalogvaplcy,Symposium, Michigan State Univ., June 1959; ISA PYOC.,2 (1959) 156. 3 J. A.P~TROCELLI AND D. H. LICHTENPELS, AnaLChem., 31 (1959) 2017.
2
4 N. BRENNERAND
Received
April
L.S. ETTRB,
zsth,
Anal.
Cl~m.,31
(1959)
1960
1815.
J.
BOOK
Citromalog.,
4 (IgGo)
169-171
RIIVIEW
(Chromatographie en phase gazeuse), par A. I. M. KEULEMANS, 2e edition, C. G. VERVER, l%diteur, Reinhold Publishing Corporation, New-York, 1959, xxi + 234 pages, gg figures.
Gas Ckromatogra$hy
Peu d’annees se sont ecoulees entre les deux editions de ce livre, dont l’int&&t, pour ceux qui veulent prendre contact avec cette nouvelle technique, se trouve ainsi dt5montrk. La rkcente edition marque un progres sur l’ancienne, en ce sens que l’auteur J, ChYOmalOg., 4 (1960)
171-172
169
numbers ‘for the diatomaceous earth columns are similar, and even, if. they areklower, the separation shown on the chromatogram was good. The Teflon column, however, showed a very poor separation for the hydrocarbbns, arid a better, but., not sufficient ‘sep’aration for the alcohols.’ Five,conclusions can be drawn from these data: x. In general, the use, of Chromosorb, Celite and Chromosorb W as support material results in a similar separation, effect. 2. The use of Firebriclc has n’o advantages: it has a very high flow resistance and at the same time, no better separation effect than Celite or Chromosorb. 3. In analyzing polar compounds, the tailing (particularly for the first components of the homologous series) is considerable. with Chromosorb and Firebrick, even if, as in the case of Chromosorb, the theoretical plate number calculated for higher homologues is better. .At the same time, this polarity effect diminishes the separation among the first members of the homologous series: ‘r - ,-. 4. The specific surface area of the support material:does no: influence particularly the separation effect df the column if the surface’area is over a certain limit, and in this case the influence of the polarity is considerably~ higher. This limit seems tosbe according to our data, at about I ms/g, which is contradictory to other data! where a minimum necessary surface area of about 3 ni2/g is given. c ’ 5. The use of .Teflon as support material .is only preferable, where the extremely high ‘polarity of the sample component(s) makes ,it necessary. * t..
The Pevizin-Elkev
Cor$oratiqn, ,
Norwalk, -_
.,..
Coma. (U.S.A.) ,,
,’
.. )’
.
1 F. M. NELSEN AND I?. T. EGGERTSEN, Anal, Cl&em., 30 (Igfj5) 1357. 2. C. I?. LEE AND P, I-F, STROSS, Division of Avzalylical Clbemislry, 135th National American Chemical _ -Society, Meeting, Boston, Mass,.. U.S.&, April g, r 959. Akad. Vorlsgsges~llschaft Geest & Portig KG., Leipzig, 3 R. KAISER, Gas Ckromatographie, : .x960, p. 33. 4 D. I-I.,DEsTY (Editor), Vapoh PJtase Cltromatograpky, Butterworths, London, 1957, p. xii. Akad. Verlagsgesellschsft Ge,est & Portig KG., Leipzig, 5 R. KAISER, Gas CfrromatograpJ~lie, 1960, p. 39.
Received
March z3rd, 1960
Gas chrom+tographic in the presence
J. Clrromalog. ,’ 4 (I 960)
analysis
of volatilg
z W-1 6g
components
of excess of non-volatiles
The analysis of dissolved gases in ‘petroleum fractions lias .been the subje,ct ,of some principle. of .these .met,hods is the same : ‘a recent publications i-3. .The fundamental large .(up to I: ml) liquid sample ‘is introduced into the chromatograph; the’ heavier ‘hydI;ocarbons are adsorbed on. a trap column installed in series before the chromatographic ,cdlurnri’and~~the_ dissolved gases: are analyzed, on,.the ,latter;’ The ‘functidnal ‘schematic of, such. i unit, is given, in Fig., I. j.
C/rro?qalog., 4 (1966). 169-17~ i .:,, .,
SHORTCOMMUNICATIONS
I
SEWS
-DETECTOR
CA\~IfR
REP I
[piiikq Fig. I.
There are many limitations if the principles of this method are applied to the more general problem of the analysis of volatile components dissolved in a nonVolatile medium. The main problem is that the temperature of the instrument must be kept low;and, therefore, the undesirable condensation (or insufficient evaporation) of the solvent into the injection block or the tubes connecting it with the column will make the analysis difficult for two reasons: (I) a part of the volatiles will remain dissolved in the condensed solvent, and (2) a frequent cleaning of the equipment will be necessary. Of course, it is possible to heat this part of the instrument using separately installed heating wires, but if commercial gas chromatographs are used, this requires modification on the instrument. It should be further emphasized that, because the necessary sample volume is in most cases unusually large (I ml: at least 100 times larger than the average liquid sample used at gas chromatographic analyses), the rapid and complete evaporation of this large sample volume is still a problem even if the injection block is heated sufficiently. A further problem is the backflushing of the trap column which also requires special modification of most commercial gas chromatographs. Recently, BRENNER AND ETTRE* described a device for the analysis of trace impurities in gases by condensing the components of interest in a small column connected to the outside gas sampling valve of a commercial gas chromatograph. A simple modification of this device permits its use for the general problem of the analysis of volatile components dissolved in a non-volatile medium. The new device consists of a special trap column with a rubber septum on its top (Fig. 2). The column is filled with adsorbents similar to those described in previous papers (activated charcoal, silica gel, firebrick, etc.) or with column materials which show a much longer retention time for the solvent than for the dissolved substances to be analyzed. The large liquid sample is injected using a hypodermic syringe with a longer needle through the rubber septum directly onto the top of the column packing material (valve in’ position I). ,In’ this way, the sample is carried with the carrier gas flow through the trap column: the non-volatile solvent is adsorbed on the packing material,‘but the volatile components are purged without loss into the chromatographic J. Chvomalog.,
4 (xg6o) 169-171
SIIORT COMMUNICATIONS
=7*
SAMP INJECT . SELF - SEALING SEPTUM.
CARR I ER GAS GAS SAMPLING
R
POSITION
I
POSITION
H
;
VALVE
CHROMATOGRAPHIC COLUMN HOT WATER (OR OIL) BATH
$00 TRAP CaUMN
Fig. 2
column and analyzed there. The trap column may be conveniently heated with a water or oil bath to elevated temperatures if necessary. After finishing the analysis, the valve is to be turned to position II, and the trap column backflushed using nitrogen or air. The device has been successfully employed for the analysis of dissolved gases or light organic solvents in water. The Pevlzin-Elmer
Corporation,
Norwalk,
EDWARD W. CIEPLINSICI LESLIE S. ETTRE
Conn. (U.S.A.)
1 P. G. ELSEY, Agtal. Chem., 31 (1959) 869. J. P. PAGLIS, 2nd Riannual International Gas Clbvomalogvaplcy,Symposium, Michigan State Univ., June 1959; ISA PYOC.,2 (1959) 156. 3 J. A.P~TROCELLI AND D. H. LICHTENPELS, AnaLChem., 31 (1959) 2017.
2
4 N. BRENNERAND
Received
April
L.S. ETTRB,
zsth,
Anal.
Cl~m.,31
(1959)
1960
1815.
J.
BOOK
Citromalog.,
4 (IgGo)
169-171
RIIVIEW
(Chromatographie en phase gazeuse), par A. I. M. KEULEMANS, 2e edition, C. G. VERVER, l%diteur, Reinhold Publishing Corporation, New-York, 1959, xxi + 234 pages, gg figures.
Gas Ckromatogra$hy
Peu d’annees se sont ecoulees entre les deux editions de ce livre, dont l’int&&t, pour ceux qui veulent prendre contact avec cette nouvelle technique, se trouve ainsi dt5montrk. La rkcente edition marque un progres sur l’ancienne, en ce sens que l’auteur J, ChYOmalOg., 4 (1960)
171-172