Chemiluminescence of synephrine based on the cerium(IV)–rhodamine B system

Abstract

A new chemiluminescence (CL) method is described for the determination of synephrine. It is based on the reaction between synephrine and Ce(IV) in a nitric acid medium and measurement of the CL intensity produced by rhodamine B used as a luminophore, similar to luminol or lucigenin in basic media, instead of as a sensitizer. In the optimum conditions, the increase of CL intensity was correlated with synephrine concentration over the range 5.0 x 10(-9)-1.0 x 10(-6) g/mL with a detection limit of 1.0 x 10(-9) g/mL. The relative standard deviation (RSD) was 2.9% for 1.0 x 10(-7) g/mL synephrine (n = 11). The method was applied to the determination of a drug in herbal products, citrus fruit and biological samples, with satisfactory results. The results given by the proposed method are in good agreement with those given by HPLC-UV and UV spectrophotometry.

Selectivity and potential interference from phenolic compounds in chemiluminescence methods for the determination of synephrine

“…Where possible, we replicated the instrument manifolds and chemical conditions described in the previously proposed chemiluminescence methods for the determination of synephrine (13)(14)(15). In the first (13), an alkaline luminol solution was merged with a solution of hexacyanoferrate(III) and then with a water carrier stream containing the injected sample (Fig.…”

“…In the second chemiluminescence method (14), an acidic cerium(IV) solution was merged with rhodamine B and then with the water carrier stream (Fig. 3b).…”

“…The same research group also quantified synephrine in citrus fruit extracts, blood and urine, using FIA with chemiluminescence detection based on the reaction with cerium(IV) and rhodamine B in acidic solution (14). As in the previous study, only the results for the fruit extracts were verified using HPLC with UV-absorbance detection.…”

“…Although synephrine has been promoted by some supplement manufacturers as a safe alternative to ephedrine, there are concerns that it may also have potential to cause harm (3,4). Numerous new methods for the determination of synephrine have recently been reported (5)(6)(7)(8)(9)(10)(11)(12), including three based on chemiluminescence detection (13)(14)(15).…”

“…As in the previous study, only the results for the fruit extracts were verified using HPLC with UV-absorbance detection. In both of these investigations (13,14), the potential interference from species such as urea, uric acid, sugars and inorganic salts were studied, but the numerous phenolic compounds present in C. aurantium extracts and biological fluids were not examined.…”