1203the organic phase with 6 M hydrochloric and 1 M nitric acids, respectively (Table VI).Application to Analysis of Strontium from Milk and Geological Samples. A sample of milk was prepared for analysis as described earlier (16). An aliquot (20 mL) of solution was taken and potassium was first removed with DB-18-crown-6 in chloroform at pH 1.0 from 1 X M picric acid leaving strontium in the aqueous phase. Then strontium from the aqueous phase was extracted with 18-crown-6 in chloroform at pH 3.0. Potassium and strontium were stripped from the organic phase with 6 M hydrochloric acid and 1 M nitric acid, respectively. In triplicate analyses the amount of strontium found was 29 ppm. The standard value was 30 ppm.For the analysis of strontium from geological samples like basaltic rock (B.R.) and syanite rock (SY II), the samples were brought into solution as per the procedure described earlier (17). An aliquot of this solution was taken and potassium was extracted with DB-18-crown-6 in chloroform at pH 1.0. Then strontium from the aqueous phase was extracted with 18crown-6 a t pH 3.0. Potassium and strontium were stripped from the organic phases with 6 M hydrochloric acid and 1 M nitric acid, respectively. In triplicate analyses the amount of strontium found in basaltic rock was 1115 ppm, as against the standard value of 1100 ppm, and the amount of strontium found in syanite rock was 238 ppm, as against the standard value of 233 ppm. The proposed method for solvent extraction separation of strontium has several advantages. It is possible to separate strontium not only from alkali and alkaline-earth elements in the concentration range of 1:50 but also from commonly associated elements such as lead, mercury, thorium, and uranium in fission product mixtures. The separation of strontium from halides was possible in higher ratios (1:500). Similarly the separation of strontium from phosphate and perchlorate was of significance as they were associated with minerals. The method is applicable to the analysis of strontium in milk and geological samples. The total time required for analysis was 2 h. The method is simple, rapid, selective, and reproducible.Registry No. Sr, 7440-24-6; 18-C- 4-( Bromomethyi)-7-methoxycoumarln (Br-Mmc), 7 4 dlethylamino)coumarln-3-carbohydrazide (DCCH), and 7-( dlethyiamino)-3-[4-( (iodoacetyl)amlno)phenyl]-4-methylcoumarln(DCIA) are evaluated as carboxylic acid derlvatlzing agents to be detected using peroxyoxalate chemllumlnescence with hlgh-performance liquid chromatography. The derivatlzatlon procedure for Br-Mmc and DCIA requires only one step as opposed to two for DCCH derlvatlzatlon. No chemliumlnescence Is observed from the Br-Mmc derivatives but detectlon limits of stralght chaln carboxylic acids derlvatlzed with DCIA and detected with peroxyoxalate chemliumlnescence are In the low femtomole range.The detection of fluorophors by peroxyoxalate chemiluminescence was first demonstrated by Curtis and Seitz who detected dansylated amino acids on a thin-layer chromatography (TLC) plate (I). Th...
The role of amine compounds in quenched peroxyoxalate chemiluminescence was investigated. The mechanistic steps examined included (1) fluorescence quenching; (2) base hydrolysis of the oxalate; and (3) a competitive interaction between the quencher and fluorophore for the peroxyoxalate reaction intermediate(s). The results showed no evidence of amines causing fluorescence quenching. Base hydrolysis of the oxalate is significant only at high concentrations of amines. When the concentration of amines is greater than or equal t o the level of oxalate, the amines can compete with the fluorophore for reaction with the intermediate(s). Because competitive effects were demonstrated, one analytical implication is that caution must be exercised in applications where more than one fluorophore is present. At low concentrations of fluorophores relative to the oxalate, chemiluminescence emission of both fluorophores will be observed. At higher levels, the fluorophores can compete for reaction with the intermediate(s). Finally, an important analytical implication of this study is that the quenching response can be used t o quantify amines without the need for derivatization. The limitation is that the linear response is approximately one order of magnitude.
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