Flow Injection Determination of Ascorbic Acid by Iron(III)-Catalyzed Lucigenin Chemiluminescence in a Micellar System

Abstract

A flow-injection method is proposed for the determination of trace amounts of ascorbic acid. This method is based on the lucigenin chemiluminescence emitted by ascorbic acid in a basic medium. In this reaction the presence of iron(III) together with a nonionic surfactant Brij 35 (polyoxyethylene-23-lauryl ether), enhanced the intensity of the chemiluminescence signal to as high as 100-times compared to that in their absence. The present method allows the determination of ascorbic acid over the range 2.OX 10-' -6.0X10 -5 mol dm-3. The relative standard deviation was 1.9% for five determinations of 5.0X106 mol dm-3 ascorbic acid; the detection limit (signal-to-noise ratio=3) was 2.0X10 L-Ascorbic acid is widely distributed in plant and animal tissues, and involves the metabolism of various substances in vivo. Many papers have been reported on the determination of ascorbic acid: titration with 2,6-dichloroindophenoll, spectrophotometry2-S, an enzymatic method6-9 including an enzyme electrode, cyclic voltammetry10, amperometryll, HPLC12,13 and a chemiluminescence (CL) method.l4-1 Among them, the CL method is known to be very sensitive over other methods. The concentration range, 10-6 -10-5 mol dm 3, levels of ascorbic acid were determined using the lucigenin CL reaction.l4-16 However, the sensitivity of these methods is not good enough and batch methods are sometimes laborious and time consuming.Glue and Petschl' first reported on the lucigenin CL reaction with hydrogen peroxide, finding that Nmethylacridone produced during the course of reaction acted as a primary emitter in this CL reaction. The formation of charge-transfer (CT) complexes between the biacridinium cation and various anions was also investigated with respect to the lucigenin CL reaction.18 Lucigenin is known to react with the reductants14, such as ascorbic acid, glucose, urea and iron(II), to form intense CL light over a wavelength range of 420 -510 nm in the same manner as an oxidant, such as hydrogen peroxide.19On the other hand, flow injection analysis (FIA) is one of the simplest approaches to the automation of chemical analysis, and is being applied to a wide variety of analytical fields. The advantages of FIA are high accuracy, a high sampling rate and versatility.20 This is due to the rapid and reproducible mixing of the sample and reagent solutions. Therefore, the application of flow injection analysis to the CL method provides both reproducibility and a high sampling rate. This paper describes the FIA method for determining 10-' mol dm 3 levels of ascorbic acid based on the lucigenin CL reaction. In applying the lucigenin CL reaction to FIA, slightly soluble reaction products15, such as N-methylacridone and 10,10'-dimethyl-9,9'-biacridylindene, caused a decrease in the reproducibility; it was thus necessary to remove both precipitates from the flow cell. A micellar system containing Brij 35 was used to solubilize the reaction products. In addition, iron(III) was also used as a catalyst in this reaction, and the CL intensity increased furthe...

Analytical applications of flow injection with chemiluminescence detection—a review

“…(227) The auto-oxidation of analgin in Tween 80, in the presence of rhodamine 6G as sensitizer, to generate CL emission has been used for its determination in pharmaceutical preparations (3). Lucigenin CL has been used to determine ascorbic acid (7) and inhibition of the iron(II)-catalysed reaction can be used to measure dopamine (19). Cobalt(II) has been determined in eye lotions by the hydroxylammonium chloride-sensitized reaction with lophine and hydrogen peroxide (17).…”

Flow‐chemiluminescence: a growing modality of pharmaceutical analysis

“…However, the addition of a small amount of the surfactant sodium dodecylsulphate prevents the precipitation. 45,46 The ionic surfactant Brij 35 has been used in the determinations of ascorbic acid 47 and isoprenaline, 48 based on the lucigenin reaction (see Table 5). …”

Flow injection methods for the determination of retinol and α‐tocopherol using lucigenin‐enhanced chemiluminescence

“…Flow injection‐CL methods for the determination of retinol and α ‐tocopherol in pharmaceutical formulations based on the enhancement effect of vitamin A on tris(2,2′‐bipyridyl)Ru(II)–Ce(IV) and of retinol and tocopherol on potassium permanganate–formaldehyde in acidic medium have been reported previously (23,24). Lucigenin‐CL enhancement or inhibitions have been reported to determine metal ions, ascorbic acid and amino acids (25–27). Table 1 compares methods for the determination of retinol and α ‐tocopherol in terms of the sample matrix and the sensitivity.…”