DD284976B5 - PROCESS FOR PREVENTING WEAR PROBLEMS DURING SAMPLING IN PHOTOMETRIC ANALYZING MEASURING DEVICES - Google Patents

Description

For this 1 page drawings

Field of application of the invention

The invention relates to a method for reducing carryover errors in sample delivery in photometric analyzers, ζ.B. Devices of spectrophotometry or fluorimetry.

Characteristic of the known state of the art In the analytical photometric are advantageously permanently installed, working on the flow or suction principle Measuring cuvettes used with devices for automatic supply of external agents at a suction point

provided test samples in the measuring cuvette are gekokoppelt.

In particular, in routine high sample throughput analysis, the operator is completely relieved of operating

and control operations and to save valuable sample material, an automatic sample change is required in which by fully exploiting a given sample volume, the required cuvette filling and a low carry-over error is achieved. In order to reduce the carry-over error to a permissible size, special flushing processes (eg with water) are introduced in the case of technical solutions that have been specified, which require an additional operation and additional means.

In another method, more sample volume is used than is necessary for a single filling of the measuring cuvette,

wherein the additional sample substance is used to pre-rinse the sample transport system (tubes, cannulas) and the cuvette and serves to ensure complete filling of the cuvette. To comply with the requirement, dio

The limit for a permissible carryover error is not to exceed the available sample volume

as completely as possible divided into shares for prewashing and measuring, with reserve volumes to compensate for

Tolerances in the sample transport system are to be considered. With the last in the sample transport system and

the cuvette volume adapted sample content is to ensure a complete filling of the cuvette.

To reduce the carryover error and to determine and supply the sample components are the following solutions

known:

1. There are specified intake times for the rinsing and filling, which requires high demands on the constancy of the performance of the pump system.

2. By means of suitable metering units (piston or peristaltic pumps), fixed metering volumes are generated. The disadvantage is the high technical complexity of piston pumps, especially with variable volume setting. Peristaltic pumps have a lack of accuracy in the dosage especially after an exchange of the tubing.

3. Cuvettes with level measurement require additional technical effort (transmitter, receiver).

4. The visual observation of the aspirated sample quantity requires a high concentration ability of the device operator and results in an increase of inaccuracy.

Object of the invention

The aim of the invention is to reduce the carry-over error with a technically simple, inexpensive and user-friendly solution with rational use of the sample volume.

Explanation of the essence of the invention

The object of the invention is to precisely and variably set the sample rates for pre-wash and fill in the automatic operation of the power of the pump system and changes in the sample transport system. According to the invention, the object is achieved by a method for reducing carryover errors in the sample supply in photometric Analysmeßgeräten, in which a predetermined, transported by a transport sample volume in a proportion for pre-washing a sample transport system and a measuring cuvette and a share to fill the cuvette for a measurement is and flushing operations are provided with a rinsing liquid. In at least one of the rinsing operations, a determination of the workload of the means of transport for transport through the sample transport system up to

Messvüvotte and to fill the cuvette, which required for pre-washing and filling shares of the intended Sample volume are dosed. The entry of the rinsing liquid into the MeßkiiVette, which simultaneously signals the end of the transport to the measuring cell, the Filling and its completion are determined by a Meßsignaländerung in photometric analyzer. With the method according to the invention can be from the knowledge of the workload for transport and filling the Calculate labor costs that are required, the existing sample volume without residual substance for the Use pre-rinsing and secure filling of the measuring cell. The rinsing operations with rinsing liquid to be carried out anyway at certain times are simultaneously without

additional technical or operational effort used for calibration. This ensures that for each

predetermined sample volume and even after changes to the means of transport and the sample transport system in the subsequent measurement process of carryover error is minimized.

In addition, it is possible in the process with the help of additional funds to further reduce the carryover

automatically insert air segments into the pre-purge portion. The necessary additional work for the means of transport need only be considered accordingly.

embodiment The invention will be explained in more detail below with reference to the schematic drawing. Show it

1 shows a block diagram of a sample transport system for a measuring cuvette of a photometer. FIG. 2 shows the transmission profile during the filling of a measuring cuvette.

The system shown in Fig. 1 contains as Meßküvetto a suction cuvette 1, which is filled by a first peristaltic pump 2 from a storage vessel 3 and a second peristaltic pump 4 is emptied into a waste container 5. For photometric analysis are next to a radiation source 6, a receiver 7, a transmitter 8 and a Photometer 9, which communicates with two hose pump 2,4, which distribute the means of transport of the system for controlling drive stepper motors (not shown) in connection. For the sake of clarity, <>. Other elements of the Fotometeraufbaus was omitted. The method according to the invention is carried out after a Fotometerabglelch the empty suction cuvette 1 against air, z. B. in the transmission mode, in connection with a flushing process using flushing liquid, the same or similar liquid properties (viscosity, surface tension) as the sample liquid to be measured. The rinsing liquid is conveyed by the hose pump 2 from a container 10 during a continuous or stepwise interrupted transport into the suction cuvette 1.

In this case, the photometer computer 9 determines the steps of the stepping motor as workloads of the transport means until the rinsing liquid enters the suction cuvette 1 and until it reaches the filling level necessary for the analysis. After each step of the stepper motor, the transmission is measured. From the course of transmission (FIG. 2), the sample inlet (filling level 0) and the completion of the filling process (filling level 1) are determined according to defined criteria and assigned to the executed number of steps. After possibly repeated determination and corresponding statistical evaluation by the Fotometer computer 9, the necessary step numbers for transport to the suction cuvette 1 and to the filling are known. For a given sample volume, the step numbers are calculated so that it can be pre-rinsed without residual substance and the suction cuvette 1 can be filled.

The workloads are redetermined in each wash program and thus continuously adapted to the current state of the system, in particular after a Goräteeinschalten or for example after the change of hoses. The execution of the method according to the invention can be inevitably predetermined or requested by the operator.

Reference numeral 1 Suction cuvette 2.4 Schiauch pump 3 Storage vessel

5 waste container

6 radiation source

7 receivers

8 evaluation electronics

9 Photometer calculator 10 containers

Claims (1)

Claim: Method for reducing carryover errors in sample delivery in photometric analyzers, where the sample volume is divided into a proportion for pre-rinsing the sample transport system and the sample cuvette and a portion for filling the sample cuvettes for a measurement and rinsing with a rinsing liquid, characterized in that at least during the first rinse with the rinsing liquid, the volume fractions for pre-rinsing the sample transport system and the measuring cuvette and the volume fractions for filling the cuvette by determining the respective workload of the sample transport system via the measured signal recorded in the photometric analyzer and a derived therefrom calibration signal for dosing the sample substance.