This invention relates to a continuous flow system automatic analyzing method and apparatus. More particularly, the present invention relates to an automatic analyzing method and apparatus which consumes a reduced quantity of a reagent and has high reliability.
Continuous flow analysis comprises forming a continuous flow of a reagent or a carrier solution, charging a sample into the continuous flow and guiding the flow to a detector for measurement. This analysis has gained a wide application in automatic analyzers because it provides the advantages that the measuring time can be shortened, not only the reaction result but also the reaction process can be measured and only a trace amount of sample is necessary. An example of the continuous flow analyzer of the prior art is disclosed in U.S. Pat. No. 4,022,575, for example. In accordance with this prior art, a carrier stream is formed by a reagent and a necessary amount of sample is charged into the stream. Though this method has the large advantage that the construction is simple, it is not free from the disadvantage that the reagent must be constantly caused to flow and hence, a large amount of reagent is necessary. In addition, the liquid pressure and flow velocity in the flow path must be accurate and stable because the time from introduction of the sample till measurement and the time required for the sample to pass through the reaction portion significantly affect the measuring accuracy. Accordingly, a waiting time is necessary from the start of operation of a pump till the start of analysis so as to stabilize the flow and the reagent is consumed in vain in the interim. If the analyzing method is changed, large quantities of reagent must also be caused to flow in order to replace the reagents.
British Laid-Open Patent No. 2,023,286 discloses an apparatus as an improvement over the conventional continuous flow analyzer of the kind described above. In this improved apparatus, two carrier flow paths are disposed and one is used as a sample introduction path with the other, as a reagent introduction path. Both flow paths are joined together on the downstream side into a single flow path and the reagent and the sample are guided to the reaction portion. Accordingly, the carrier liquid is always caused to flow through the path and the condition of the path is kept stable. The reagent in a necessary amount is introduced in synchronism with the introduction of the sample only at the time of analysis so that the reagent can be saved. In addition, the reagents can be easily replaced when the analyzing method is changed.
However, the drawback of this improved apparatus is that since two carrier flow paths are disposed, two liquid feed pumps must be disposed and the overall size of the apparatus becomes great. In this apparatus, the performance of the pumps affect significantly the accuracy of analysis so that high precision pumps must be employed, resulting eventually in the increase of the cost of production. Hence, the number of pumps is preferably as small as possible.