Chemistry: analytical and immunological testing – Halogen containing
Reexamination Certificate
2000-06-02
2003-07-08
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Halogen containing
C436S125000, C436S126000, C436S155000, C436S159000, C436S166000, C436S175000
Reexamination Certificate
active
06589796
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for measuring iodine, a specimen-pretreating reaction tool, and an airtight tool for the specimen-pretreating reaction tool.
BACKGROUND ART
Iodine is an indispensable trace element that becomes a raw material of the thyroid hormone for promoting metabolism of a living body, and the iodine content in the body is 15-20 mg for a healthy adult. The weight of the human thyroid hormone in any adult is about 20 g, and the thyroid gland causes iodine in blood to be selectively concentrated and generates the thyroid hormone. The intake, per day, necessary for any living body is said to be 100-150 &mgr;g. If this iodine lacks and this state is left as it is, goiter is generated and further the function of the thyroid gland deteriorates. Particularly, newborn infants come to undergo a drop in intelligence, hypoplasia, neurological symptoms and the like. Pregnant women's shortage of iodine is said to result in stillbirths and an increase in the death rate of newborn infants.
The number of people who live in regions where there is a risk of the shortage of iodine is said to be about 16 hundred million. Such people are concentrated in developing countries. It is said that this is because in inland and mountainous regions or regions where floods arise frequently or the amount of precipitation is much, by the outflow of iodine from soil the iodine content in plants that grow therein becomes insufficient so that people and animals who/that live therein have a short intake of iodine, thereby suffering from iodine deficiency disorder. For a preventive measure for the disorder, it is said that effective is a relatively simple method, such as supplementation of iodine, for example, an intake of iodized salt. In reality, in USA, European nations and the like, the measure based on this method produces an advantageous effect in iodine-shortage regions.
In such a situation, a target of the eradication of iodine deficiency disorder was adopted in the world summit for children by the United Nations in 1990, and the eradication is listed as one of important themes of International Council for Control of Iodine Deficiency Disorders (ICCIDD), UNICEF and the World Health Organization (WHO), or is listed as a state measure of a great number of nations. For this, it is important that the actual conditions of iodine deficiency disorder are precisely grasped, the disorder is diagnosed and treated, and the actual conditions are periodically being monitoring.
It is said that iodine deficiency disorder can be diagnosed by measuring iodine in urine since the intake of iodine and the excretion amount of iodine into urine have a good correlation. The normal value of iodine in urine, which is an index for this diagnosis, is said to be 100 &mgr;g/L or more.
As a method for measuring iodine, E. B. Sandell et al. reports calorimetric determination using the property that iodide ion functions as a catalyst for increasing the rate of a redox reaction represented by the chemical reaction equation (I) (and abbreviated to Sandell-Kolthoff reaction hereinafter. E. B. Sandell and Kolthoff, Mikrochemica Acta, vol. 1, P9-25(1937)).
2Ce
4+
+As
3+
→2Ce
3+
+As
5+
(I)
That is, this is a sensitive measuring method using the fact that iodine functions, as shown by the chemical reaction equations (II) and (III), as a catalyst for a reaction that by adding an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution as reagents to iodide ion in a specimen, yellow ammonium cerium sulfate (quadrivalent ion) is reduced to produce colorless trivalent cerium ion.
2Ce
4+
+2I
−
→2Ce
3+
+I
2
(II)
I
2
+As
3+
→2I
−
+As
5+
(III)
In measurement of a specimen such as urine, however, the specimen contains a large amount of interference materials having an effect on this redox reaction, such as ion of ascorbic acid and ion of thiocyanic acid. Thus, the specimen cannot be applied, as it is, to this reaction. Actual measurements require pretreatment such as removal of the interference materials in the specimen. As the pretreatment, the following methods are suggested: a method of heating a specimen intensely and incinerate it (M. C. Sanz et al. , Clinica Chemica Acta, 1, 570-576, 1956), a wet incinerating method of adding an oxidizing agent such as perchloric acid or chloric acid, and heating the resultant to oxidize interference materials (Zak et al., Anal. Chem., 24(8), 1345-1348, 1952) , and a method of separating interference materials by dialysis, chromatography or the like (WO96/27794). Among these pretreating methods, the wet incinerating method according to Zak et al. is used as a simplest method. As a mildest and standard wet incinerating method, there is suggested and performed a method of adding 250 &mgr;l of a specimen of urine and 750 &mgr;l of a chloric acid reagent solution into a glass test tube 10 cm in length and 13 mm in inner diameter in a locally-exhausting provision, heating the test tube at 110-115° C. for 1 hour with a sand bath or an aluminum block under an open condition, cooling the tube, adding 3.5 ml of an arsenious acid reagent solution that is acidified with sulfuric acid into the tube to conduct reduction reaction for 15 minutes, adding 350 &mgr;l of an ammonium cerium sulfate reagent solution into the tube, and subjecting this solution to calorimetric determination at 405 nm after the reaction for a certain time (Manual of measurement of iodine in urine, edited by International Council for Control of Iodine Deficiency Disorders, 1993).
However, it is required that a vessel used in the above-mentioned chloric acid-using pretreatment of a urine specimen is made of a raw material which can endure even if the raw material is heated together with such a strong oxidizing agent as chloric acid, and it is also required that, from the vessel, materials which interfere in the Sandell-Kolthoff reaction following the pretreatment do not flow out. Therefore, no vessel made of a polymer material has been used for the chloric acid-using pretreatment of specimens. Moreover, vapor discharged in the pretreatment step is vapor containing chlorine having an irritant smell, or the like. Thus, it is necessary that the pretreatment is performed in a locally-exhausting provision having an exhaust device. For this reason, there is being performed a method of using a glass test tube resisting both heat and any oxidizing agent as a vessel in the locally-exhausting provision having the exhaust device and further heating it together with an oxidizing agent in an open state from the viewpoint of a problem about strength. Besides, in the method of heat-treating a specimen in the glass vessel in an open state, in order to decrease a change in the amount of the solution therein by evaporation and scattering of the specimen, reagent solutions and the like, it is necessary to use a long test tube having a volume scale of 1 ml or more.
The long test tube having a volume scale of 1 ml or more is used; therefore, in order to treat a great number of specimens at the same time, it is necessary to use a wider treating space and a large-scaled heating device. Furthermore, in the chloric acid-using pretreatment of a specimen, in order to discharge harmful vapor originating from chloric acid, which is generated upon heating the specimen together with chloric acid, it is necessary to use the locally-exhausting provision. In the measurement, the color fading reaction (Sandell-Kolthoff reaction) after adding the arsenious acid reagent solution and the ammonium cerium sulfate reagent solution as reagents to iodide ion in a specimen is a relatively speedy and sensitive reaction. For this reason, in measuring an absorbance when a given time passes after the start of the color fading reaction, strictness of measuring-time is required. Therefore, in the measurement wherein specimens are transferred from test tubes to cells for absorbance-measurement one tube
Irie Minoru
Ohashi Toshinori
Yamaki Mituo
Hitachi Chemical Co. Ltd.
Soderquist Arlen
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