Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Apparatus and method for examining a liquid sample
The invention relates to an apparatus and a method for examining a liquid
sample, in
particular a urine sample, for determining the risk of urinary lithiasis.
The risk of becoming ill with urinary lithiasis is 5 to 15% on average in
industrialised
countries: peak values of approximately 20% are reached in the Gulf States.
Epidemiological data show an increasing tendency in the incidence and in the
prevalence of
calculosis. 75% of calculi formed in the industrial countries consist of
calcium oxalate.
A patient who has already suffered from a calculus once without therapy or
with unsuitable
therapy should expect a probability of recidivism of 75 - 100%. The need for a
suitable
method for determining the risk of uroliths may be derived from this. This is
particularly
important for determining the risk of recidivism in patients who are already
ill.
IS
A method developed at the urological clinic of Bonn University and based on a
calculation
of what is known as the Bonn risk index (BRI) has proven suitable for
determining a urolith
risk indicator. To calculate the BRI, a 40-millimolar ammonium oxalate
solution is added
to a urine sample by a standard method until calcium oxalate crystallisation
commences.
The millimolar concentration of oxalate (Ox2-) added to the urine sample at
this moment is
determined and related to a sample volume of 200 ml. In specialist medical
circles, the
concentration of oxalate (Ox2-) based on a sample volume of 200 ml is
described as the
added amount of oxalate (Ox2-). In addition, the initial concentration of free
calcium ions in
the urine sample [Ca2+] is determined: the concentration is given in mmol/l.
The BRI is
then calculated as
BRI = [Ca2+] / (Ox2-)
A BRI of I/L is considered to be the risk limit for calcium oxalate lithiasis.
All problems
are allocated one of eight risk categories, I - VIII. BRI 1/L falls between
risk categories IV
and V. In a variation of the measurement method, the risk of calcium phosphate
lithiasis
CONFIRMATION COPY
AMENDED
SHEET
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can also be determined, a phosphate solution, rather than the ammonium oxalate
solution,
being presented to the urine sample until it crystallises and the ratio of
free calcium ions
and phosphate solution being determined as the risk indicator.
A measuring device for examining a liquid sample by titration is known from
WO 02/063285.
WO 91/16618 Al describes a measuring head for a titration measurement
apparatus.
As regards the method developed at the Bonn University and mentioned at the
outset,
reference should be made to the scientific paper entitled, "Comparison of
laser-probe and
photometric determination of the urinary crystallisation risk of calcium
oxalate", in Clinical
Chemistry and Laboratory Medicine, vol. 40, no. 6, pages 595f., June 2002.
JP 2000/266668 describes a measuring head for reaction monitoring.
JP 11014632 describes a fibre sensor for liquid level determination.
Reference should also be made to the scientific paper entitled, "Laser-probe-
based
investigation of the evolution of particle sized distributions of calcium
oxalate particles
formed in artificial urine", in Journal of Crystal Growth, vol. 233, no. 1 -
2, pages 367f.
The object of the invention is to provide an apparatus and a method for
examining liquid
samples with which, in particular, the above-described method of examination
of a urine
sample for determining the Bonn risk index may be carried out cost-effectively
and reliably
in a medical practice or in a hospital. The apparatus should enable the method
to be carried
out in a standard, substantially automated manner and at low cost.
AMENDED SHEET
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According to the invention, the object is attained by an apparatus
comprising.the features of
claims 1, by a method with the features of claims 30 and 31, and by a
measuring head for
use in an apparatus of the generic type comprising the features of claim 38.
The inventors have found that a titration system may be used in conjunction
with optical
transition measurement to determine the crystallisation point of a liquid
sample. However,
the measuring arrangement for transmission measurement could not, in turn,
necessitate the
exclusive use of sample vessels for the liquid sample, in particular for a
urine sample, of
high optical quality. The inventors have concluded from this that although a
portion of the
liquid sample is to be investigated thoroughly with a light ray for
transmission
measurement, it is, on the other hand, disadvantageous to pass rays through
the sample
vessel itself.
According to the invention, therefore, the apparatus comprises a measuring
head which
comprises an optical fibre and may be immersed into a liquid sample to be
measured. A
first end of the optical fibre is allocated to a light source. A Iight sensor
is arranged in a
defined manner relative to the light path, predetermined by the optical fibre,
of the light
emitted from the light source. In the immersed region of the measuring head
there is further
provided a recess which further interrupts the optical fibre in such a way
that at least a
portion of the light guided by the optical fibre thoroughly examines the
liquid sample over
a defined distance. Clouding of the liquid to be examined, which is due to the
initiation of
crystallisation during the defined addition of a titration liquid to the
liquid sample by a
titration system of the measuring apparatus may then be detected by the light
sensor on the
basis of the increasing losses of transmission.
AMENDED SHEET
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Preferably, a ray-form light source is used as the light source and may be
produced; for
example, by means of an orifice structure in an expansive light source or by
the use of a
laser, for example a laser diode. Furthermore, the notion of the light source
in the present
application is not restricted to the visible wavelength range, as a source of
electromagnetic
radiation outside the range which is perceptible to the human eye may also be
used, for
example an infrared source. Visible light, in particular in the red range of
the spectrum,
preferably of approximately 650 nm is preferred.
A detector system which is suitable for the light source is used as the light
sensor and may
be, for example, a photo transistor, a photo diode or a photo resistor. It is
also conceivable
to construct the photo sensor as a sensor matrix so the influence of faults
may be reduced
by adjusting the sensor arrangement.
According to the invention the measuring head is accordingly configured in
such a way
that, with the ends of the optical fibre, it is allocated to the light source
and the light sensor,
but may be separated therefrom. It is particularly preferable to use a
measuring head which
is only used for one respective urine sample in the context of a disposable
measuring head.
This procedure affords the advantage, in particular, that the measuring head
coming into
contact with the liquid sample does not have to be cleaned in a complex manner
after taking
a measurement. In addition, as a disposable part, it does not have to be
formed so as to be
suitable for a large number of measuring and cleaning steps.
With respect to geometric configuration, the measuring head is so constructed
that it is
immersed into a urine sample, at least until a recess in the measuring head,
which is
traversed by the light ray, is filled with the liquid to be measured, in
particular the urine. In
addition, it is preferable to arrange the light source and the light sensor in
such a way that
they do not come in to contact with the liquid sample, i.e. only the measuring
head which
touches the liquid sample becomes contaminated, although this is immaterial as
it is a part
which will be exchanged after one measurement in any case.
A possible configuration of the measuring head comprises an optical fibre with
at least one
ray-deflecting device. This enables the light source, as well as the light
sensor to be
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positioned above the liquid level of the urine to be examined. Two ray
deflectors which are
at an angle of 45° to the horizontal and an angle of 90° to one
another, so that a ray portion
leading substantially vertically downwards, followed by a substantially
horizontal ray
portion and a ray portion which is directed substantially vertically upwards,
is constructed
in the measuring head, have proven particularly advantageous. Said recess in
the measuring
head is located in at least one of these ray portions, so that the ray
penetrates through the
liquid sample substantially freely in a specific portion and detects changes
in transmission
over this known path.
With an apparatus according to an invention of this type it is accordingly
possible to
determine, in conjunction with a metering system for the crystal formers, the
amount of
crystal former which leads to the initiation of crystallisation. A solution
which contains a
lithogenic component of the type of crystal of which the risk or
crystallisation is to be
determined is used as the preferred crystal former for a sample. An oxalate or
phosphate
solution is preferred as the crystal former for a urine sample.
For measuring the amount of crystal former required in proportion to the
volume of the
liquid sample, it is necessary to determine the existing amount of liquid in
the urine to be
examined. With a known weight of the sample vessel, this can be determined
using a
weighing apparatus.
Alternatively, the geodesic height of the liquid level in the sample vessel
may be measured
in the case of a known form of sample vessel in order to determine the volume
of the
measured liquid. Various apparatuses are conceivable for this purpose, for
example,
moisture sensors which have an open pair of electrodes between which contact
is produced
by the liquid to be measured, which in turn may be detected by resistance
measurement. A
device for determining the geodesic height of the liquid level, connected to
the measuring
head for transmission measurement is particularly preferred. Preferably, the
measuring head
is then, in turn, connected to a height adjusting apparatus which enables the
measuring head
to travel into the sample vessel from above and therefore to be immersed into
the urine. If
the height adjusting apparatus is so constructed that measurement is carried
out from a
known reference height from the distance covered in a vertical direction, the
geodesic
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height of the liquid level and therefore the volume of liquid in the sampling
container may
be determined if the position of the liquid sensor is known.
In a particularly preferred configuration of the invention, the recess in the
measuring head
is used to determine the position of the liquid level of the urine sample. The
initially free
measuring head, i.e. there is no liquid in the recess provided by transition
measurement, is
moved vertically downward in the direction of the liquid level until the
liquid to be
examined penetrates into the recess and changes the transmission. The position
of the liquid
level may then be determined from the known position of the recess and the
light ray
travelling therein as well as the distance covered.
The measured value of the free calcium ions [Ca2+J, required for BRI
calculation, is
determined in a preferred development of the apparatus for examining a urine
sample by
means of a suitable sensor system. In a possible configuration, a specific
amount of the
untreated urine sample is removed from the sample vessel for this purpose and
presented to
a sensor of a Ca2+ ions by means of a fluidics system. 'This may be, for
example, an ion-
selective field-effect transistor which comprises an ion-selective membrane.
The fluidics
system preferably also comprises an apparatus for introducing rinsing liquids
for cleaning
purposes. For calibrating the sensors, it is additionally preferred to present
a calibrating
solution thereto. The construction of the pumps, containers, and receivers
required for this
propose and of the associated fluidic control are within the ability of a
person skilled in the
art.
For controlling the apparatus according to the invention, the apparatus
according to the
invention may comprise internal or external control units in the form either
of
microcontrollers or externally connected PCs, by means of which an interface
for the user
in the form of input units and displays may also be produced.
The measuring head preferably has a holding device for holding it on a mount
of the
apparatus, the holding device comprising a holding means, in particular an
integrally
connected component with a set breaking point, which is so constructed that
the holding
device may only be used once. This means that the measuring head can only be
used once.
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Accidental repeated use of a measuring head, which can lead to distorted
results owing to
impurities, is thus avoided. Repeated use of the measuring head is precluded
particularly
reliably if the holding means is made unserviceable as a holding means after
the first use of
the holding device.
In a variation, the measuring head is so constructed that it conveys the light
received from
the light source to the light sensor. A change in the transmission of the
liquid sample to be
examined may be determined in this way.
Alternatively, the measuring head may be constructed in such a way that it
conveys the
light received from the light source along a light path, adjacent to which the
sensor is
arranged, but in which the sensor is not directly arranged. A measuring head
configuration
of this type may be used to measure scattered light provided by the liquid
sample.
The apparatus can comprise a drive device for moving the measuring head
relative to the
sample vessel, at least a portion of a determining device for determining the
liquid level of
the liquid sample being provided on the measuring head. To simplify the
exchange of the
sample vessel, it is advantageous in any case if the measuring head is movable
relative to
the sample vessel. In the above-described development, this movement may at
the same
time conveniently be used to determine the liquid level.
If the recess in the measuring head is a part of the determining device, the
light source and
the light sensor may be used for liquid level determination, together with
this recess as the
light intensity of the light emitted by the light source and conveyed through
the measuring
head changes on entering the recess into the liquid sample to be examined.
A fluid duct of the fluid system may be constructed in the measuring head. A
portion of the
liquid sample may then be aspirated via the measuring head for determining a
parameter of
the liquid sample to be examined via the fluid duct. This aspiration fluid
duct is then also
exchanged when the measuring head is exchanged and this makes it easier to
keep the
measuring apparatus clean.
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The fluid duct is preferably closed by a sealing stopper which, in the
measuring position of
the measuring head, is penetrated by a line portion of the fluid system on the
measuring
head receiving side. A sealing stopper of this type allows the fluid duct to
be sealed cleanly
against the line portion.
In a preferred development, a fluid duct of the titration system is
constructed in the
measuring head. A separate titration feed pipe into the sample vessel can then
be dispensed
with.
Preferably, a stirrer is provided for stirring the liquid sample, the
measuring head
comprising at least one flow component, in particular at least one flow blade,
for co-
operating with the liquid sample. This allows defined mixing of the liquid
sample during
stirring and therefore a reproducible examination of the liquid sample.
In a variation of the measuring apparatus, the measuring system comprises a
spectrometer
for determining the concentration. This allows reliable, substance-selective
determination
of concentration.
With regard to the method, the object of the invention is achieved on the one
hand, by a
method for examining a liquid sample by titration, which employs the above-
described
measuring apparatus according to the invention. This object is achieved, on
the other hand,
by a method for examining a liquid sample by titration, comprising the
following steps:
preparation of the liquid sample, measurement of the liquid level of the
liquid sample by
introduction of a measuring head from above into the liquid sample,
determination of the
concentration of at least one type of ions in the liquid sample, feeding of a
crystal former
into the liquid sample and measurement of the transparency of the liquid
sample after
introduction. Defined, reproducible determination of the liquid parameters is
thus possible.
Preferably, a new disposable measuring head is used prior to feeding. This
ensures
particularly readily reproducible processing conditions with regard to the
measuring head.
Cleaning of a used measuring head is unnecessary.
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Preferably, a concentration determining sensor is cleaned and/or calibrated
prior to
determination of concentration. This provides defined conditions during
determination of
the concentration, so concentration-determining sensors which have a long-term
drift
tendency may also be used.
The liquid sample may be stirred before determining the concentration. This
ensures
defined measuring conditions, as a homogeneously distributed liquid sample is
measured.
Preferably, a sample parameter is calculated from the measured values of
concentration and
transparency. This allows a concentration-dependent crystallisation point to
be determined
by a simple numerical value.
Preferably, the pH of the liquid sample is additionally determined. This
provides additional
information about the constitution of the liquid sample.
In addition, the temperature of the liquid sample may be determined. This may
be used, in
particular, to correct the determined concentration. Additional liquid
parameters may also
be measured using the measuring apparatus. In an advantageous development, the
measuring apparatus may be constructed as a mobile laboratory for determining
a large
number of liquid parameters.
Liquid parameters of this type may be: the specific gravity, the content of or
the presence of
Na, K, Mg, NH4, Cl, P04, S04, creatin, uric acid, leucocytes, nitride,
albumin, proteins,
glucose, ketone, urobilin, billirubin, urobillinrubin, erythrocytes,
haemoglobin. The
separation of serum proteins such as albumin, transfernn, globulins,
immunoglobulins and
immunoglobuIin fragments.
The invention will be described in more detail with reference to the following
figures which
show embodiments.
Fig. 1 shows the optical measuring system for determining the crystallisation
point.
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Fig. 2 shows a sample-receiving region with a sample vessel and a sampling
plate as well
as the optical measuring system according to Fig. l and the associated
positioning
device.
Fig. 3 shows the metering system for titration.
Fig. 4 shows the fluidics system.
Fig. 5 is a schematic external view of the measuring appliance.
Fig. 6 is a view similar to Fig. I of an alternative measuring head for an
optical measuring
system.
Fig. 7 is a view along sight line VII in Fig. 6.
Fig. 8 is a section along VIII-VIII in Fig. 7.
Fig. 9 is a view along sight line IX in Fig. 6.
Fig. 10 is a view of the measuring head according to Fig. 6 from above.
Fig. 11 is a section along line XI-XI in Fig. 9.
Fig. 12 is a flow chart for examining a liquid sample by titration.
Fig. 1 is a schematic view of the optical measuring system for titration for
determining the
crystallisation point. A measuring head I absorbs light from a light source 2
and conveys it
to a light sensor 3. The measuring head I is formed as an exchangeable unit,
in particular as
a disposable unit. The measuring head also allows an arrangement of the light
source 2 and
of the light sensor 3 above the level of the liquid sample. The ray deflection
of the
measuring head required for this purpose may be achieved, for example,
according to Fig. I
by two reflective surfaces 6.1 and 6.2 which are at an angle of 45° to
the vertical and at an
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angle of 180° to one another. Further configurations are conceivable,
in particular the use of
a substantially horizontal reflecting element in the bottom region of the
measuring head and
a V-shaped ray configuration. Preferably, the illuminating light leaves the
light source with
a directional component pointing vertically downwards and the light is
returned to the light
sensor with a directional component pointing vertically upwards. This enables
the
measuring head 1 to be immersed into the liquid sample without soiling the
liquid source 2
and the light sensor 3.
It is preferable to introduce a substantially ray-shaped light ray into the
measuring head. If
this then consists of a material which is transparent to the employed wave
length of the
illuminating light, for example, PMMA (polymethylmethacrylate) or Makrolon
(polycarbonate), which are 70-81 % transparent to visible light. Any plastics
materials
which may be produced by injection-moulding or by machining processes may
generally be
used. Alternatively, the optical fibre may also consist of glass. In most
cases, the influence
of scattered light may be ignored for the measuring head and merely the
external regions in
which ray deflection occurs are then advantageously reflected. Alternative
configurations of
the measuring head include glass fibres or optical fibres based on polymers
for ray
positioning. It is also conceivable to separate regions of opposing ray
positioning from one
another by the geometric configuration of the measuring head. This may be
effected, for
example, by a recess which separates a first portion of the measuring head
with
downwardly directed ray positioning from a second part in which ray
positioning is
directed upwards. Owing to the formation of an interface from the material of
the
measuring head to the open region in the recess, crosstalk between the
individual regions of
ray positioning in the measuring head, which reduces the accuracy of
measurement, is
avoided. A free region of this type is sketched in Fig. 1.
For taking transmission measurements, it is necessary to interrupt the optical
fibre over a
specific irradiation distance. According to Fig. l, a recess 5 in which the
liquid to be
examined penetrates in the immersed state should preferably be provided in the
measuring
head. This recess 5 and the liquid located therein are then traversed by the
released light
ray. This is then introduced into the measuring head or into the optical fibre
of the
measuring head again and presented to the light sensor 3
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Fig. 2 is a longitudinal section through the sample-receiving region 7 for
receiving a sample
vessel 8 positioned on a sample plate 9. The sample plate 9 is so positioned
that it provides
a support which is as horizontal as possible for the sample vessel 8, for
determining the
position of the liquid level as exactly as possible. The sample plate 9 is
also allocated a
motor 10 to allow a rotational movement for mixing the liquid sample in the
sample vessel
8. In a preferred configuration, the sample plate 9 is driven indirectly, and
this may be
achieved, for example, by a magnetic drive. This measure enables the sample-
receiving
region 7 to be sealed from the external region for reasons of hygiene. In
particular, the
region 7 may be worked out on the housing side in such a way that the escape
of liquids
into the interior of the appliance is totally precluded.
The measuring head 1 for transmission measurement is located above the sample
vessel 8
in the sample-receiving region 7. It is fixed on a measuring head carrier 11
and can
preferably be exchanged by mere manual interventions in the sense of a
disposable article.
The light source 2 which remains permanently on the measuring system and the
light sensor
3 are preferably arranged in the measuring head 11. In a preferred
configuration, moreover,
the measuring head Garner is allocated a marking and/or detection system by
means of
which an already used measuring head 1 may be detected or which marks a
measuring head
as used when it is attached or is immersed into the liquid sample. In a
possible
configuration, two plastic pins which may be broken off and which actuate a
switch when
inserted into the measuring head carrier are arranged on the measuring head.
The pins break
off so that the switches cannot be triggered again if they are re-used. The
switch transmits
two signals to the electronics. The first signal has a short duration and the
second signal is
applied throughout the measuring process and at the same time serves to check
the position
of the measuring head.
For positioning the measuring head l, the measuring head Garner 11 is
connected to a
positioning system 12, which substantially allows a vertical movement for
immersing the
measuring head I into the liquid sample.
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For carrying out the investigation, it is necessary to determine the liquid
volume of the
liquid sample in the sample vessel 8. This may be effected in various ways. On
the one
hand, it is possible to derive the volume by determining the weight of the
filled sample
vessel 8. For this purpose, the sample plate 9 can be allocated a weighing
unit.
Alternatively, if the shape of the sample vessel is known, the volume may be
measured by
determining the geodesic height of the liquid level of the liquid sample in
the sample vessel
8. A configuration in which a liquid detection system 14 is connected to the
measuring
head, and the positioning system 12 for the measuring head is allocated a
position
measuring system 13 is particularly preferred. Starting from a specific
reference point, the
vertical distance covered by the measuring head I until it reaches the liquid
level may be
used to determine the volume of the liquid sample in the sample vessel 8. In a
possible
configuration, the position measuring system 13 comprises contact switches for
the
reference position. These may be formed, for example, as Hall-effect sensors.
In addition, the distance covered by the measuring head during positioning may
be
determined by a suitable sensor, for example a rotational speed sensor or a
linear scale. If a
stepping motor is selected as the drive, it is unnecessary to use additional
sensors to
determine the movement.
Fig. 3 is a schematically simplified view of the metering system allocated to
the titration
system for feeding a crystal former into the liquid sample. A 0.04 N ammonium
oxalate
solution is preferably added as the crystal former for effecting calcium
oxalate
crystallisation. If calcium phosphate crystallisation in human urine is to be
examined
instead, the ammonium oxalate solution is replaced by a phosphate solution. In
a possible
configuration of the metering system, the controlled, volumetrically precise
addition of the
crystal former is effected by applying a precisely predetermined pressure to a
resource
container in which the crystal former is located. This is produced by a pump
19 and
monitored by a pressure sensor 20. Using an extraction tube immersed into the
liquid under
pressure in the resource container 17, the crystal former is conveyed by the
filter 18 to a
nozzle 16, from which the controlled addition of the crystal former into the
sample vessel 8
and the liquid sample located therein then takes place. Alternatively, the
crystal former can
be introduced by means of a metering pump, not shown in Fig. 3, rather than
applying
CA 02545643 2006-05-04
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pressure to the resource container 17. Other volumetrically precise methods of
addition may
also be selected for carrying out the measuring method. Preferably, the liquid
sample will
be stirred during the feeding process. This can be effected by rotating the
sample vessel, the
measuring head 1 immersed into the liquid sample then acting as a flow
breaker.
Fig. 4 shows the fluidics system of the measuring apparatus in a schematically
simplified
manner. It is used for examining further parameters of the liquid sample, the
content of free
calcium ions being of particular interest in the case of urine. In addition,
the urine
temperature and the pH can also be determined. For this purpose, a specific
fraction of the
liquid sample is removed from the sample, automatically or by the user, and
conveyed to
the fluidics system, the lines of this fluidics system having a vacuum, so the
liquid can be
transported to the intermediate container 2l by switching the valves 23.1,
23.2 and 23.3.
The necessary vacuum is produced therein by an air pump 22. Owing to this
measure, both
the liquid sample and further liquids, for example a first calibrating
solution 27 and a
second calibrating solution 26 as well as a cleaning solution 25 can be
conveyed through
the sensor block 24. It is also possible to ventilate the ducts for cleaning
purposes via the air
supply 28. As an alternative to using a vacuum in the fluidics system, a pump,
for example,
a hose pump, may be used for transporting the liquid. This configuration is
not shown in
Fig. 4.
Ion-selection field-transistors (ISFET) of which the ion selectivity is
brought about by the
choice of a suitable membrane, are preferably used in the sensor block 24. A
pH sensor and
a temperature sensor may additionally also be used as the sensors.
Fig. 4 does not show the details of signalling and control. The apparatus may
be controlled,
for example, by one or more microcontrollers, which can also process the
sensor signals.
The measuring system may be formed as an autarchic unit, but it is also
conceivable to
outsource specific control functions and functions, for example, for forming a
user interface
or for printing functions, to an external control unit or to a PC.
Fig. 5 is a general view of the measuring apparatus. A housing, in which the
transmission
measuring system with the exchangeable measuring heads and the metering system
for
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carrying out titration measurements are accommodated is shown. The apparatus
further
comprises a fluidics system for sampling with further sensor elements, in
particular for
measuring the content of free calcium ions and the pH and the temperature of
the liquid
sample. Only the sample-receiving region for introduction of a sample vessel
is accessible
to a user. This sample-receiving region is preferably constructed from
stainless steel to
allow easy cleaning. A configuration in which at least portions of the sample-
receiving
region 7 are covered with a layer of titanium oxide is also preferred. This
has an anti-
bacterial effect, in particular with conjunction with UV-irradiation, so
automatic
disinfection of the sample-receiving region can be carried out. If a UV light
source is
integrated in the region of the sample-receiving region 7 for this purpose, it
is preferable to
close the sample-receiving region with a UV-tight door element to protect the
user.
In addition to use of the apparatus according to the invention for examining
human urine, in
particular for determining the BRI, it is possible to examine a large number
of different
liquids, in which the transmission properties are changed by the addition of a
substance and
for which quantities change in transmission is to be determined
quantitatively.
Fig. 12 is a flow chart for carrying out the method for examining a liquid
sample by
titration in the example of a sample of human urine.
The measuring apparatus is switched on in a preparatory step 32. Starting
parameters, for
example, an identification code of the patient, are then input in an input
step 33 via an
alphanumeric keyboard. The user can control the input parameters via an LCD
display of
the measuring apparatus. After the parameters have been input, the measuring
head 1 is
inserted into a corresponding measuring head socket of the measuring apparatus
in an
assembly step 34. The measuring head 1 comprises a contact pin (not shown)
which
cooperates with a corresponding contact in the socket of the measuring
apparatus. If the
measuring head is incorrectly positioned in the socket, the measuring
apparatus
automatically emits an error message on the LCD display. The sample vessel 8
is then
placed on the sample plate 9 with the liquid sample and the door element 30 is
subsequently
closed in a readiness step 35. The closed position of the door element 30 is
checked by the
measuring apparatus via corresponding contacting. If the door element 30 is
not correctly
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closed, the measuring program emits an error message. Measurement is
subsequently
started automatically. The liquid level of the liquid sample is subsequently
measured in a
level measuring step 36. For this purpose, the measuring head 1 is driven from
a defined
zero position by means of the positioning system 12, which comprises a
threaded spindle
from above into the sample vessel with the liquid sample. Using the position
measuring
system 13, the distance covered is measured via the number of revolutions of
the threaded
spindle. As soon as the recess 5 is wetted by the liquid sample, in other
words, as soon as
the lower edge of the recess 5 is at the height of the liquid level, the
intensity of the ray
falling onto the light sensor 3 changes as, on the one hand, the refractive
indices at the
interfaces of the recess 5 change and, on the other hand, the light ray
through the liquid is at
least partially attenuated. The change in intensity caused by the attainment
of the liquid
level is detected by the light sensor 3. As soon as a defined change has
occurred, for
example as soon as the measured intensity attains less than 98% of the
starting intensity, the
instantaneous position of the threaded spindle is detected by the position
measuring system
13. In this way, the liquid level of the liquid sample in the sample vessel 8
can be
determined exactly and conclusions can be drawn about the amount of sample
from the
height of the liquid level and the then known liquid volume in the sample
vessel 8.
A cleaning step 37 now takes place in preparation for concentration
determination. For this
purpose, the cleaning solution 25 is temporarily guided past the sensor block
24. The
cleaning solution 25 then remains for a short time in the fluidics system, so
bacteria can be
destroyed. This passing and standing of the cleaning solution 25 is repeated a
plurality of
times during the cleaning step 37. If the measuring apparatus is not used for
a prolonged
period, it may also be necessary to clean further line regions of the fluidics
system and not
just the sensor block 24.
The sensor block 24 is calibrated in a subsequent calibration step 38. For
this purpose, a Ca
ion sensor and the pH sensor of the sensor block 24 are brought into contact
with the first
calibration solution 27. The first calibration solution 27 is drawn past the
sensors of the
sensor block 24 for a short time. As soon as the measured values of the sensor
are stable, as
detected by the measuring program by means of a slight variation in successive
measured
values, the measured values are stored. This process is subsequently repeated
with the
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second calibration solution 26 within the calibration step 38. The measurement
program
determines the necessary calibration parameters for Ca-concentration
determination and pH
determination from the measured values of the sensor determined in this way,
from the two
different calibration liquids. The subsequently collected measured values are
collected
using the calibration parameters contained.
The liquid sample in the sample vessel 8 is subsequently stirred in a stirring
step 39. For
this purpose, the sample plate 9 with the sample vessel 8 is set into uniform
rotation about
the vertical axis of the sample vessel 8. The measuring head 1 is lowered
further into the
liquid sample and therefore acts as a stirrer during the stirnng step 39.
In a subsequent concentration-determining step 40, a portion of the liquid
sample from the
sample vessel 8 is aspirated via a supply line 41 (CF.Fig.4) from the sample
vessel 8 into
the sensor block 24. The aspirated sample volume is then passed by the sensor
block 24 for
I 5 a short time. After the waiting for an adjustment period of the Ca sensor
of the sensor block
24, the Ca2+-concentration is measured with the Ca sensor of the sensor block
24. The pH is
measured with the pH sensor of the sensor block 24. The temperature is
measured using the
temperature sensor. The temperature value is used to correct the Ca-
concentration value by
means of the measurement program.
A further cleaning step 42 for the sensor block 24 now takes place. The
cleaning step 32
corresponds to the cleaning step 37.
In a crystallisation measuring step 43, the sample vessel 8 is initially
rotated uniformly by
means of the motor 10 of the sample plate 9 in a preparatory manner, so that a
thoroughly
mixed liquid sample is obtained. The light source 2 is then switched on and
the intensity of
the light arriving at the light sensor 3 from the light source 2 is measured.
At specific time
intervals, for example at respective intervals of one minute or also at
intervals of a few
seconds, a specific amount of ammonium oxalate is injected or titrated from
the resource
container 17 via the metering system 15. The measurement program calculates
the total
injected amount of ammonium oxalate from the previously known concentration of
the
ammonium oxalate solution. Titration is continued during the crystallisation
measuring step
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43 until calcium oxalate crystallisation occurs. The crystallisation point can
be detected by
clouding of the liquid sample and an associated lower light intensity at the
light sensor 3.
The instant of titration, for example, at which the measured light intensity
at the light
sensor 3 is 98% of the light intensity at the beginning of titration can be
determined as the
crystallisation point. During the crystallisation measuring step 43, the
amount of added
ammonium oxalate required for achieving the crystallisation point can be
measured in this
way with an accuracy of, for example, +/- 0.2 ml at a titration rate of 40
mmol/I via the
reduction in the light intensity measured at the light sensor 3.
The BRI index is subsequently calculated in a calculation step 44. For this
purpose, the
amount of oxalate is initially calculated from the amount of liquid in the
liquid sample and
the amount of ammonium oxalate added up to the crystallisation point. The BRI
index is
obtained in the manner mentioned at the beginning of the description as the
quotient of the
Ca2+-concentration determined in the concentration-determining step 40 divided
by the
amount of oxalate. In medical circles, the amount of oxalate is understood to
be the
concentration of oxalate (Ox2-) based on a sample volume of 200 ml.
In a subsequent storage step 45, the following values in particular, are then
stored: the
patient's identity code, the date, the time, the measured temperature, the
measured Ca2+-
concentration, the measured pH, the BRI index calculated form the measured
data, the
respective individual values measured by the sensors of the sensor block 24
and any error
messages that have appeared. A compact flash card, in particular, is used as
the storage
medium. For maintenance or monitoring purposes, the storage medium can be
transferred
to a maintenance or monitoring computer via a read-out interface.
The desired data of the measured, calculated or stored values are printed out
in a final
printing step 46. For this purpose, the stored information can be transferred
to a computer,
for example via an USB-interface. The data can be further processed there.
A measuring head which is an alternative to the measuring head I shown in Fig.
1 is shown
in Fig 6 to I 1. Components of this measuring head corresponding to those
which have
already been described herein before with reference to Fig. I to 5 or with
reference to the
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description of the method according to Fig. 12 bear like reference numerals
and will not be
described again in detail. In the upper holding portion 47 in Fig. 6, in a
lateral wall 48, the
alternative measuring head 1 has a horizontally extending holding groove 49
which is open
to the left in Fig. 6. The holding groove 49 is a component of a holding
device for holding
the alternative measuring head 1 in a socket of the measuring apparatus. The
socket has a
holding rib (not shown in the drawing) which is complementary to the holding
groove 49.
A holding pin 50 which is arranged in the holding groove 49 and extends
horizontally in
Fig. 6 and transversely to the extension of the holding groove 49 is a further
component of
the holding device. In the socket of the measuring apparatus, the holding pin
50 cooperates
with a holding opening of the measuring apparatus corresponding thereto.
A fluid duct 51 which communicates fluidically with the supply line 41 of the
fluidics
system in the assembled alternative measuring head 1 is constructed in the
alternative
measuring head 1. The fluid duct 51 extends in a first duct portion 52 from an
upper
limiting wall, which is horizontal in Fig. 6, of the recess 5 upwards into the
holding potion
47. The fluid duct 51 has a 90° deflection here, and initially narrows
after this deflection
and then widens conically in a second duct portion 53. Via a subsequent
stepped
enlargement 54, the second duct portion opens from a lateral wall 55, on the
left of Fig. 6 of
the alternative measuring head 1.
Before the alternative measuring head 1 is inserted, the fluid duct 51 is
closed by a sealing
stopper (not shown) which is inserted tightly into the enlargement 54. In the
measuring
position of the alternative measuring head 1, in which the measuring head 1 is
received in
the socket of the measuring apparatus, the sealing stopper is penetrated by a
line portion of
the supply line 41 of the fluid system on the measuring head receiving side.
This line
portion is formed by a conventional commercial injection needle. Once the
sealing stopper
with the line portion has been pierced, the sealing stopper seals the line
portion against the
internal wall of the enlargement 54, producing a fluid connection between the
fluid duct S 1
and the supply line 41 that is sealed from the exterior.
In a deflection portion 56 in the lower region, in Fig. 6, the two ray
deflectors 6.1, 6.2 are
directly adjacent to one another so that the deflection region 56 has the form
of an inverted
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roof edge. A flow blade 7S is formed integrally onto the two deflectors 6.1,
6.2 so as to
project on respective sides. The two flow blades S7 act as flow components
which
cooperate with the liquid sample during stirring of the liquid sample for
thorough mixing
purposes.
During insertion of the alternative measuring head I into the measuring
position, the
holding pin SO latches into the associated opening in the socket of the
measuring apparatus
1. The opening is configured in such a way that, as the measuring head is
removed after
measurement, the holding pin SO breaks away from the holding portion S7 at a
set breaking
point. As the holding pin SO has a holding function, the alternative measuring
head cannot
be re-used after it has broken away.
In the alternative measuring head 1, the recess S is used to determine the
liquid level of the
liquid sample, as described herein before in conjunction with the flow chart
in Fig. 12.
1 S Together with the positioning system 12, the position measuring system I
3, the light source
2, the light sensor 3 and the steel deflectors 6.1, 6.2, therefore, the socket
S forms a
determining device for determining the liquid level of the liquid sample.
The two variations of the measuring head shown on the one hand, in Fig. 1 and,
on the
other hand, in Fig. 6 to 11, are each constructed in such a way that they
convey light
received from the light source 2 directly to the light sensor 3. In a further
variation of the
measuring head (not shown), the measuring head is so configured that it
conveys the light
received from the light source 2 along a light path, adjacent to which the
light sensor 3 is
arranged, the sensor not being arranged directly in the light path. In this
case, the light
2S sensor 3 does not measure changes of transmission produced by the incipient
crystallisation
of the liquid sample, but changes in the resultant scattered light intensity.
The light sensor 3
can, for example, be arranged in such a way that it does not initially measure
a light
intensity from the light source 2 in the case of a non-scattering liquid
sample. Only due to
the scattering produced as a result of the incipient crystallisation does
scattered light pass to
the light sensor 3 which can then be correspondingly sensitive in design so
that it can then
already detect small amounts of scattered light.
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In a further variation of the measuring head (not shown), a fluid duct of the
metering or
titration system 15 is constructed with the nozzle 16 in the measuring head.
In a further variation of the measuring head, a spectrometer is used to
determine the Ca2+-
concentration in the concentration-determining step 40, rather than the sensor
block 24. For
this purpose, the portion of the liquid sample, of which the Ca2+-
concentration is to be
determined, is permeated with light of different wavelengths, conclusions
about the
presence of Ca-ions in a corresponding concentration being drawn form the
absorption of
the liquid at specific wavelengths.
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List of Reference Numerals
1 Measuring head
2 Light source
3 Lightsensor
4 Light path
5 Recess
6.1, 6.2 Ray deflector
7 Sample-receiving region
8 Sample vessel
9 Sample plate
I 0 Motor
I I Measuring head carrier
12 Positioning system
13 Position measuring
system
14 Liquid detection system
15 Metering system
16 Nozzle
17 Resource container
18 Filter
19 Pump
20 Pressure sensor
21 Intermediate container
22 Air pump
23 Valves
24 Sensor block
25 Cleaning solution
26 First calibration
solution
27 Second calibration
solution
28 Air supply
29 Housing
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30 Door element
31 Open region in measuring
head
32 Preparatory step
33 Input step
34 Assembly step
35 Readiness step
36 Level measuring step
37 Cleaning step
38 Calibration step
39 Stirnng step
40 Concentration-determining
step
4l Supply line
42 Cleaning step
43 Crystallisation measuring
step
44 Calculation step
45 Storage step
46 Printing step
47 Holding portion
48 Lateral wall
49 Holding groove
50 Holding pin
S 1 Fluid duct
52 First duct portion
53 Second duct portion
54 Enlargement
55 Lateral wall
56 Deflecting portion
57 Flow blades
