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Nov. 6, 1962
Filed April 9, 1959
h- I00
United States Patent 0 " IC€
Patented Nov. 6, 1962
Ernst Palm, Uberlingen (Bodensee), Germany, assignor t0
Bodenseewerk, Perkin-Elmer & Co., G.m.b.‘H., Uber
lingen (Bodensee), Germany
advantages, it has been proposed that the speed'of the
Filed Apr. 9, 195%, Ser. No. 805,226
6 Claims. (Cl. 346—-33)
This invention is concerned with a method ‘and a de
recording chart be varied in inverse proportion to
the time period of the experiment. This has the effect
of contracting the time axis while at the same time those
bands appearing after longer intervals of time are given
slopes of greater steepness so that they can be more
readily detected.
However, the Well known methods proposed for
achieving this end have the disadvantage that the bands
vice for the analysis of mixtures by means of gas chroma 10 of the individual substances will always be recorded at
In analysis 'by means of gas chromatography, a sample
mixture in the gaseous or vaporous state is introduced
into a stream of an inert carrier gas. This sample is con
veyed through an adsorbing substance (separating sub
stance) by the carrier gas stream. The individual com
ponents of the mixture undergoing investigation are ad
sorbed with more ‘or ‘less strong af?nity by the separat
ing substance. The time required for ?ushing a compo
different points of the recording paper, depending on
the type of apparatus used and the velocity of flow of
the carrier gas. Therefore, gas-chromatographic dia
grams obtained from two different apparatus cannot ‘be
compared with each other without di?iculty. The evalu
ation of such diagrams is therefore a rather diiiicult and
time wasting job and requires considerable experience in
this particular ?eld.
The present invention has therefore for its objects the
nent through the separating substance by means of the
elimination of these disadvantages and the provision of
carrier gas stream depends on the degree of a?inity with
a system whereby the bands of a gas-chromatographic
which the respective component is adsorbed. A c0m~
diagram are always recorded at exactly de?ned points of
ponent, for instance, which does not interact in any way
the recording paper.
with the separating substance will pass through the latter
In order to accomplish the above objects, the speed of
with maximum speed determined by the mechanical flow 25 the recording paper is varied inversely proportional to
resistance of the apparatus; a substance having in?nitely
the duration of the experiment, but the feed motion of
great a?inity for the Separating substance would not pass
the recording paper is only ‘begun when a substance not
through it at all. Generally, the different substances of
interacting with the separating substance appears at the
a mixture will appear with more or less delay one after
exit of the latter.
the other at the exit from the separating substance and 30
In order that the speed of the recording chart be in
may be individually recorded.
versely proportional to the duration of the experiment,
Normally, a bridge with temperature sensitive resistors
the path length of feed of the recording chart varies with
is arranged at the exit of the sample cell containing the
the logarithm of the duration of ‘the experiment, and
separating substance, the bridge being so arranged that
this is the time interval which has lapsed since the mo
one arm is immersed in the gas stream. If the emerging 05 Cl ment the sample was introduced into the carrier gas
stream of gas contains a component in addition to the
stream. But since the recording chart only begins to
carrier gas, the thermal conductivity of the gas is changed
’ move after the air component has appeared, its length
whereby the ‘bridge is unbalanced. With conventional
corresponds to the logarithm of the elapsed time of the
apparatus, the measured voltage value so obtained is am
experiment In minus the logarithm of vthat time IL whichv
pli?ed and utilized for the control of a recording device 40 passes before the "air band” 1 appears. Since
which establishes a diagram on a continuously moving
recording chart. In this ‘diagram, the individual com
ponents of the mixture appearing one-after the other at
the exit of the separating substance can be distinguished
as “bands.” Such a diagram is shown by way of exam
ple in FIG. 1 which represents the measured voltage
plotted against time.
The reference character to designates the moment at
which the experiment starts, i.e., the moment at which
the mixture undergoing investigation is introduced into
the carrier gas stream. After an interval‘ of time tL,
a substance appears at the exit of the sample cell which
has not interacted with the separating substance con
tained in the cell and which produces a band 1 in the
diagram. Such an inert substance may be air, for exam— ‘
ple. The “air band” is almost regularly found underv
normal test conditions. The different components of
the mixture appear after time intervals t1, t2, t3 . . . and
v and the relation tn/tL
for each band is iridependentof.
the type of the apparatus used, each band will be recorded
at an exactly de?ned point of the recording chart.
The points at which the bands of the different sub
stances appear may be preliminarily marked on the re-_
cording chart won a transparent cover sheet correspond
ing in shape to the recording chart.
‘For the practical application of the method, an ap
paratus is used in which a measured value correspond!‘
ing to the separated components of interest is recorded
on a continuously moving record chart having a speed
inversely proportional to the elapsed time of experiment.
The apparatus is so designed that‘ the feed motion of the
recording chart only‘ star-ts a certain time after a sub-'
stance not interacting with the separating substance ap
produce bands 2, 3 and 4. The period of time up to
the moment where these bands appear on the diagram 60 pears at the exit of the latter.
A further development of the invention allows the
and the height of the bands permits a conclusion as to
sensitivity of the recording to be continuously increased
the nature and the concentration of the components. As
during the experiment. This is done in such a manner
can be clearly seen from FIG. 1, the bands show ever
increasing width the later they appear.
that the sensitivity of recording is varied proportionally
With a constant speed of feed of the recording chart, 65 with the elapsed experiment time. This has the effect
of compensating for the ?attening of the very late ap
there is the disadvantage that substances having a strong
pearing bands. It is then possible, at those points where
adsorption affinity for the separating substance appear
the bands of the different substances will appear, to print
only after a relatively long interval of time, causing un~
graduated scales on the recording chart or on a corre
desirably long recordings. This, in turn, gives rise to
considerable dii?culties with regard to the evaluation and 70 sponding transparent cover sheet. These graduated scales
permit the concentrations of the respective substances to
?ling of such diagrams. In order to eliminate these dis
be read from the heights of the recorded bands. Evalua»
3 he
known manner in accordance with an electric measured
This electric measured value U5 comes from a logarith
tion and analysis of gas chromatographic diagrams may
these be accomplished without difficulty.
In the preferred embodiment of this invention, a cylin
mically wound variable potentiometer on which is im
der supporting a recording chart is driven by means of
an electric motor running at constant speed, the motor
pressed the measuring voltage Um. The measuring voltage
Um is supplied by a detector which is arranged at the
exit of the column containing the separating substance
being switched on when the mixture undergoing investi
gation is introduced into the carrier gas stream. The
recording cylinder is driven through a transmission which
supplies a speed inversely proportional to the time period
elapsed during the experiment. Such transmissions are
known in the prior art. Rope drive transmissions equipped
with appropriate cam plates, for instance, may be used
and which supplies a measuring voltage as soon as the
individual components of the mixture of interest appear.
for this purpose. In order to eliminate the initial speed
range in which the driven speed of the transmission should
be in?nitely great, a clutch may be arranged between the
motor and the transmission, the clutch being engaged
only after the motor shaft has performed one full revolu
tion. The delay of the paper feed may also be realized
by another clutch between the transmission and the
recording cylinder. This latter clutch has the function
of setting the recording cylinder into action only after
the drive shaft of the transmission has performed a cer
The detector may be a Wheatstone bridge of the afore
mentioned type, for instance, but any other suitable means
may also be used for this purpose. The potentiometer
13 is coupled with the recording cylinder §.
According to the invention, the number of revolutions
of the recording cylinder satis?es the following equation:
where N6 designates the number of revolutions of the
recording cylinder. Thus, after 1,000 revolutions of disk
1, disk 4, and shaft 5', recorder cylinder 9 will have
completed exactly 11/2 revolutions.
If now disk 1 has an angular velocity of
tain angular movement the length of path of which can
be adjusted. The variation in recording sensitivity is
most advantageously obtained by the aid of a logarithmi
cally wound potentiometer coupled with the paper feed
motion. The measuring voltage is impressed upon the
potentiometer and the voltage for a recording device is
tapped from it. The potentiometer is designed as a varia
ble potentiometer by which the full scale sensitivity may
e varied over the range of one order of magnitude, the
variable potentiometer performing one full revolution
through one range of magnitude of the time scale during
the feed of the recording chart. After each revolution
4 rev.
the ?rst half revolution of the driven shaft 5" is com
pleted after an interval of time of 2.5 minutes; the sec
ond half revolution after 25 minutes, and the third half
revolution after 250* minutes. The graduated scale 8 per
mits setting time 21, from 0.25 to 250' minutes. Even in
the event of the last mentioned adjustment, a time in
terval from 25 up to 250 minutes will still remain for
of the potentiometer, a change-over of the measuring
range may be effected.
The invention is more fully explained by way of the
embodiment disclosed by the accompanying drawings and
the following detailed description.
In the drawings:
FIG. 1 is an illustration of a fractogram is obtained
with prior art apparatus.
PEG. 2 shows in schematic form a device in accord
ance with the present invention.
FIG. 3 shows by way of example a diagram recorded
with the device of this invention.
A synchronous motor (not represented in the draw
the measurement.
The variable potentiometer 13 may be coupled with the
recording cylinder 9 by means of a rope drive so that it
performs a full revolution if the recording cylinder has
turned one half revolution. The tapped voltage is there
by continuously varied proportional to the time by the
factor 10. Thereupon, the additional change-over of the
measuring range is effected, and with the following half
revolution of the recording cylinder—corresponding to a
full revolution of the variable potentiometer-—a continu
ous variation of the sensitivity up to a factor of 100
takes place.
A diagram such as illustrated in FIG. 3 is then obtained.
The bands of the individual substances, CH4, for ex
ample, are preliminarily marked on the recording tape.
ings) is switched on when the substance of interest in in
Graduated scales are printed at these points to permit
jected into the carrier gas stream. A disk 1 ?tted with
the various heights of the bands which constitutes
a driving pin 2 is mounted on the shaft of the synchronous 50
a means for directly determining the concentrations of
motor. After the shaft of the motor has performed one
the respective substances.
revolution, pin 2 contacts a dog 3 which is provided .on
What is claimed is:
a disk 1%. Disk d is mounted on the driven shaft 5’ of
1. In a signal recording system including analyzer
the transmission 5. Disk 4 is thereby rotated and, con
means for determining components of a sample, means
sequently, shaft 5' is driven. The transmission 5 is so
for introducing a sample into said analyzer means, said
designed and constructed that with a constant driving
analyzer means generating upon each introduction a train
speed, the speed of the driven shaft 5" is inversely pro
of time-displaced signal peaks providing a measure re
portional to the time which has elapsed since the start
of the experiment and thus since the moment the motor
spectively of different components in said sample, and
signal recording means, the improvement wherein said
was set in motion. The equations shown in transmission (if) signal recording means comprises:
5 indicate that when the angular velocity ((114) of disk
chart means having a time axis;
4 is constant, the angular velocity (m6) of disk 6 is in
chart marking means movable transversely to the time
versely proportional to time.
axis of said chart means in response to each of said
A disk 6 carrying a driver pin 7 which is adjustable 65
in holes 7’ in accordance with a graduated scale 8 is
signal peaks;
driving means adapted to provide relative movement
between said chart means and said chart marking
means along the time axis at a variable speed in
After the driven shaft 5” and the disk 6 have per
versely proportional to the time elapsing from the
formed a certain angular movement which can be ad
introduction of said sample; and
justed on the graduated scale 8, pin 7 comes in contact 70
means for starting said driving means upon the appear
with a dog 19 of a recording cylinder 9 and starts to
ance of a preselected signal peak.
set the latter in motion.
2. The apparatus of claim 1 wherein said driving means
Numeral .11 designates a recording pen which is mount
comprises a constant speed motor means and a variable
ed on a slide 12. Slide 12 is movable axially with respect
to the recording cylinder and may be moved in any 75 speed transmission means driven by said motor.
mounted on the driven shaft 5".
3. The apparatus of claim 2 wherein said transmission
means is characterized by an output speed 100 which bears
a relationship to the input speed wt‘ de?ned by the equa
4-. The apparatus of claim 2 wherein said means for
starting comprises a clutch between said constant speed
motor means and said chart means whereby said motor
able speed inversely proportional to the time elapsing
from the introduction of said sample; means for starting
said driving means upon the appearance of a preselected
signal peak; electrical attenuator means ‘adapted to re
ceive said signal peaks and having a variable output;
means for varying the output of said attenuator means;
chart marking means movable transversely to the direc
tion of movement of said chart means; and means for
means rotates through a ?nite angle before said chart Ii) moving said chart marking means proportionally to the
output of said attenuator means.
means is actuated thereby.
6. The apparatus of claim 5 wherein said attenuator
5. In a signal recording system including analyzer
means is a logarithmically wound potentiometer.
means for determining components of a sample, means
for introducing a sample into said analyzer means, said
analyzer means generating upon each introduction a train 15
of signal peaks providing a measure respectively of differ
ent components in said sample, and signal recording
means, the improvement wherein said signal recording
means comprises movable chart means; driving means
adapted to move said chart means at a continuously vari 20
References Cited in the ?le of this patent
Guillemin ____________ __ Sept. 3,
Potter ______________ __ Oct. 21,
Spracklen ____________ __ Aug. 11,
Norem ______________ __ Sept. 15,
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