Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a method and apparatus
of analysis, especially photometric,with micro-tubs which are
automatically filled in combination or not with a sampling device.
Particularly, the present invention relates to the systems
for photometric analyses in the visible and ultraviolet radiation
fields and to apparatus intended to effec-t such operations, for
analysis laboratories in which samples must sequentially be exami-
; ned, mainly of biological liquors with a high accuracy especially
in connection with per-centage data. These analyses must be
carried out with sample volumes which very often extremely small,
so that the problem of accuracy is thus exalted since the presence
of a residual of polluting liquor in the test tub has a considerable
bearing on the percentage data to be calculated: this fact is
evidence both by the presence of residues of a previously tested
sample and to the presence of residues of the washing liquors. In
these systems, which use micro-tubs which are automatically filled
by a sample-takin`g mechanism coupled to the tubs, the error indi-
cated above, which is also called ''carry over'' is extremely detri-
mental even if special expedients are adopted for emptying the
tubs and, as rule, it is increased as a function of thc properties
of the surfaces on which the liquors flow and of the properties of
the liquor to be analyzed as such, which may be viscous, foamy,
or capillarly-active.
The system and the apparatus according to the invention have
been conceived so as to attain a substantial accuracy in the rea-
dings even maintaining, in comparison with the systems known at
present, low values of sample useup with respect to the volume which ~;~
is necessary for the tests. The invention permits that very low
pollution values may be achieved, such as to have an even lower
bearing on the final error of the readings than that due to other
factors.
According to the present invention there is provided a method
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of analysing a liquid, using an ap~aratus in which a chamber
is disposed in a flow path with a liquid outlet from the
chamber in a lower region thereof, which method comprises
(i) discharging from said path any liquid remaining from a
previous reading or any washing liquid, by applying suction
to the downstream end of said path so as to flush the path
with a gas; (ii) filling the path, including the chamber,
with a fresh column of liquid to be analysed, by applying
suction to the downstream end of said path; ~iii) advancing
the column of liquid in said path towards the downstream end
of said path, by the application of suction thereto, so as
to cause that portion of the liquid column which was at an
upstream end region of said path at the end of the filling
of stage ~ to occupy the chamber; ~iv) degasi:Eying the
contents of the.chamber, by applying suction to an upper zone
of the chamber; and (v) effecting a reading on the liquid
in the chamber.
In practice, provision is made for a flow of air
from above and from below, which, in addition to removing at
the outset the sample which has already been tested, sweeps
away the major fraction of the residual liquor in the test
route (cuvette and pipings) prior to drawing in the subsequent
sample by suction.
This suction of the sample takes place from the
~ottom of the micro-test-tub and the intake from top, so that
the traces of residual liquor of the previous test can be .
swept away during the suction of the sample: this operation
takes place in three stages in rapid sequential order, viz.:
the first two stages Eor washing and the third for taking the
reading.
With advantage, there is also provided for a stage
of suction of air and thus for establishing a negative pressure
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in the micro-tub after that the terminal portion of the
column of the liquor to be tested has reached the micro-tub;
thus an effect is achieved or removal of bubbles and foam,
that which is vital for a correct photometric reading.
Accordin~ to the present invention thexe is also
provided an apparatus for the photometric analysls of biological
and others liquors, comprising a tub of three-way type, having
a top and a bottom, an arrival duct coming from a sampling
means and connected at the top of the tub, a suction and
discharge duct connected at the bottom of the tub, an air-
suction duct connected at the top of the tub, and valve means
for controlling the suction and discharge duct and the air
suction duct in a selective manner, and means controlling
a time sequence.
According to one aspect of the invention, there is
provided an apparatus suitable for use in analyzing a liquid,
which apparatus comprises a container provided with a chamber
having an inlet in an upper region, a first outlet in a lower
region and a second outlet in an`upper region; a first pipe
connected or connectible to a sampling needle or an equivalent
means, and connected to the inlet; a second pipe connected
to the first outlet and connected or connectible to a suctlon
source; a third pipe connected to the second outlet and
connected or connectible to a suction source; first actuatable
valve means disposed in the third pipe; and control means
for controlling the acutation of the first and second valve
means.
The micro tub may comprise a prismatic cavity which
is intended for taking the readings, and inclined bottom wall
connected to the suction and discharge duct, a top cavity in
the form of a chimney which is connected at the top with the
feed duct and from which the top suction duct branches off.
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The invention will be better understood from the
description and the accompanying drawings which show an
exemplary embodiment of the invention without limiting it~
In the drawings:
FIGURES 1, 2, 3, and ~ show in a very dlagrammatical
manner the characteristic sequential stages of a method r
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of analysis, the apparatus -therefor bein~ shown limit-
- edly to the liquid flo~ diagram.
FIGURE 5 shows an ele^tri.c diagram, and
FIGURES 6, 7, 8 and 9 sl~ow a perspective view,
: 5 in diagrammatical fashion and ~ross-sectiona]. views~
taken along the l.ines VII-VII and VIII-VIII of FIGURE 6,
and a vertical diagrammatical cross-section of the micro-
tub-containing cell, respectively ~
According to that which is shown in th_ accompany-
ing drawings, the numeral 1 generally indicates the c~
which contains the micro-tub 3~ the latter being extend-
- ed vertically and .in a slot-like outline for the request-
ed analyses. At top, the micro--tub 3 has a chimney-
like outline at 3A, to be extended into a duct 5 and
fitting 5A. Laterally, in a position intermediate in :~:
the portion 3A a second duct 7 with a fitting 7A is
connecGed to 3A. From the bottom of the micro-tub 3 a
passageway 3B is excended from which a duct 9 with a .: .
fitting 9A branches off upwards. From the duct 5 of :~
the cell l a portion of pipe ln extends towards the
needle 12 which is intended o:r sampling the liquors
from the respective test tubes P. From the duct 9 a
piping 14 branches off, in wh ch an electromagnetic
valve 16 is inserted. Through the valve 16 the duct 14 `;`
and thus the bottom of the tub can be out in communi~
cation with the suction duct 18. The duc-t 7 is con-
nected to a porticn of piping 20 which reaches via an
electromagnetic valve 22 the same suction duct 187 which :
serves ~l~o for discharging the liquors which have been
flown through the apparatus.
The micro-tub can also be mad~ with a capacity of
300 microlitres and the electronlagnetic valves are of
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the quick-acting type and are controlled by a special-
ly provided electronic circuit which is with appro-
priate timers for carrylng out a cycle of steps.
In the illustrative diagrasl of FIGURE 5, the nume-
ral 26 indicates a switch for starting the filling cycl--,
28 is a switch for starting the emptying cycle~ 30 is a
- timer for establis~ing -the filling time~ the latter be-.ng
adjustable as a function of the properties of the sample
concerned, 3~ is a wait-timer for the time of waiting
between a fil~ing stage and a flo~Y stage to be described
hereinafter, 3~, is a timer for tha dura-tion of the flow
stage, 36 is a timer for a wait stage between the flow
stage and the reading, in order to obt.ain the settling
of the liquor in the micro-tub. The numeral 38 is the
emptying timer.
The operation of a cycle of analysis is as follows7
startin~ from the stage of empt~ting and discharge of a
- liquid presellt in the micro-tub and which can be a wash-
ing liquor or a sample of a pre.vious analysis.
During the first stage the two electromagnetic
valves 16 and 2` ar-e simulta~eously opened while the
ncedle 12 is in the atmosphere: thus a suction o- air is
experienced from the suction duct lO through the micro~
tub 3 and the two ducts 7 and 9. Thus the ~1ischarge o-
the liquid held in the tub is carried out and. moreover~
due to the effect of the air stream, also the removal of
at least a portion of the residues of liquids otherwise
stuck to the walls of the ducts. This initial stage
(see FIGURE 1) is terminated by the closure of the two
electromagnetic valves 16 and ~.
In a second sta~e of the cycle the liquid is drawn .
as soon as the sampling needle has ent.ered the test tub
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or when the test tub has been l:;~ted to have ~he
-sampling needle entering it. At this sta~e~ -the
timer 30 opens -the electromagI!etic valve 16 ror such
- ~ tirle that the drawn-in liquor may fill the sections
10, 3, 9 and 14 of the routeO The liquid in the
sections 9 and 14 is the first ~o flow through the in-
ternal route in which polluting residues are still
present so that it will ob~iously be the most heavily
', polluted one as it has washed out the whole route.
The liquid oontained in the micro-tub portion 3 is ca-
pable'of diluting possible further residues and this
is efficiently carried out during a stay time which is
established by the timer 32. The liquid presen-t in the
- section 10 of 1,he route is obviously the less polluted
one and ~hall be the one for taking the readingsO
A third stage is carried out with advantage imme- ~
diately as -the sampling needle has emerged from the
test tub or as the test tub has been withdrawn on com-
pletion of the suction stage, During this third,stage
the valve 16 is reopened for a certain time which is
established by the timer 34. This act originates a
flow of the liquid column in-to ~he route formed by the
sections 10~ 3~ 9~ 14 and thus the nonpolluted liquor
which was formerly present in the section 10~ is trans- ,~
2S ferred into the micro-tub 3 and thus is in a posi-tion
to undergo the photometric test, the latter being thus
exempt to a degree from errors due to pollution.
During a fourth stage, after the closure of the
valve 16 and when the le~s polluted liquor to be test-
ed is in the micro-tubj the valve 22 is opened for a
short time and this fact causes a negative pressure to
be produced in the top portion of the ~icro-tub: the
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result is the removal ar.d the disposal also of the
foamy fractions and air bubbles ~hich might have been
formed also deeply in the licluid Inass in the micro-
tub. This stage substantially permits to restrict
the alterations of the readings uue to bubbles of air
and this is due to the effect o~ the negative pressure
- and thus, to a certain degree~ to the phenomenon of
"negative water hammer" as caused by the negative pres- -
sure. Immediately on closing the ~alve 22, the read-
ing is taken and a fresh cycle is started by removing
the tested liquor.
It is intended that the drawings show but an exaDIple
as a practical showing of the invention, modifications
and changes being possible without departing from the
scope of the invention~
