Chemistry: analytical and immunological testing – Halogen containing – In aqueous solution
Patent
1997-09-03
1999-08-17
Warden, Jill
Chemistry: analytical and immunological testing
Halogen containing
In aqueous solution
436 63, 436124, 436129, 436166, 436174, 436175, 436177, G01N 3352
Patent
active
059393289
DESCRIPTION:
BRIEF SUMMARY
The invention relates to methods and means for the determination of iodide in aqueous solutions, preferably in urine.
BACKGROUND OF THE INVENTION
In clinical diagnosis, the determination of iodide in the urine plays an important role in monitoring the function of the thyroid gland. The determination of iodide in foodstuffs and fodder is also becoming increasingly important. Suitable rapid methods which can be used routinely have hitherto not been described for the determination of iodide in urine.
In most known methods, a pretreatment of the urine is carried out either by treatment with a strong acid or by ashing at high temperatures. This is followed by the determination of iodide by measurement of the reduction of cerium (IV) ions to cerium (III) ions by the catalytic action of iodide (Sandell-Kolthoff reaction). The pretreatment with strong acids (potassium chlorate in 70% perchloric acid) or the dry ashing of the urine with potassium carbonate serves to remove substances which can interfere in the reduction of the cerium ions. This results in the formation of toxic perchloric acid vapors and the perchlorates which are likewise formed are known to be explosive.
Anal. Chim. Acta 282, 87 (1993) describes a method for the determination of iodide using chlorpromazine and hydrogen peroxide, but this is very susceptible to interference by many substances which occur especially in urine and also in foodstuffs and fodder. Furthermore, DE-A 37 43 224 discloses a method for the determination of peracids, wherein a chromogen and iodide are added to the sample solution. However, those skilled in the art could not deduce from this publication that this reaction can be used for the detection of iodide.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a simple and rapid test for the determination of iodide by means of which even untrained personnel can determine without difficulty even small amounts of iodide in aqueous solutions semiquantitatively or even quantitatively, without rigid pretreatment measures being required and without the formation of toxic substances.
The invention provides a method for the determination of iodide in aqueous solutions which is characterized in that the sample solution is admixed with a chromogen and a peracid solution and the color reaction is evaluated visually or photometrically. For the determination of iodide in urine, the urine sample is preferably pretreated by means of a purified activated carbon. It is here advantageous if the purified activated carbon is present in an extraction column.
The invention further provides means for the determination of iodide in aqueous solutions, which comprise a chromogen, a peracid solution and, if desired, an extraction column containing an activated carbon.
It has been found that the method of the invention is less susceptible to interference and can be carried out significantly more quickly than the known methods for the determination of iodide in urine. Iodide concentrations down to 6 .mu.g/dl can still be detected in the presence of a high anionic matrix concentration. In aqueous solutions without an organic matrix, the detection limit for iodide is 0.2 .mu.g/dl.
DETAILED DESCRIPTION OF THE INVENTION
For the process of the invention, chromogens used can be all chromogens known in the literature which are oxidizable in the presence of peracids using iodide as catalyst. Suitable are preferably aromatic amines such as o- and p-phenylenediamine, benzidine and benzidine derivatives, in particular tetramethylbenzidine. The concentration of the chromogen should be in the range from 1 to 5 mM, preferably about 2.5 mM.
Peracid solutions are, for example, aqueous solutions of peracetic acid, perpropionic acid, perbutyric acid, perbenzoic acid, etc., preferably an aqueous peracetic acid solution. The concentration of this solution should be in the range from 1 to 5%, preferably about 2.5%.
The means of the invention can either consist of two solutions, a peracid solution and a solution of a chromogen, or apart from the pe
REFERENCES:
patent: 3121615 (1964-02-01), Price
patent: 4900682 (1990-02-01), Fischer et al.
Davies et al. "Determination of Peracids in the Presence of a Large Excess of Hydrogen Peroxide Using a Rapid & Convenient Spectrophotometric Method", Analyst, Sep. 1988, vol. 113 pp. 1477-1479.
Yaqub et al "Spectrophotometric determination of iodide in blood and urine", JPMA, J. Pak. Med. Assoc. 1979, 29(11) 249-50. Abstract only.
Yabu et al "Measurement of iodide in urine", Eiyo Asesumento (1988) 5(2) 179-83. Abstract only.
Beil Stefanie
Fischer Wolfgang
Groh Thomas
Carrillo S.
Merck Patent Gesellschaft mit beschrankter Haftung
Warden Jill
LandOfFree
Method for the determination of iodide does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the determination of iodide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the determination of iodide will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-314571