High-Performance Liquid Chromatography Coupled with Chemiluminescence Nitrogen Detection for the Study of Ethoxyquin Antioxidant and Related Organic Bases

Abstract

The Chemiluminescent Nitrogen Detector (CLND) for use with high-performance liquid chromatography (HPLC) allows for the low-level detection of nitrogen-containing compounds with simple quantitation. The nitrogen selective detector's equimolar response (i.e., equal response for nitrogen independent of its chemical environment) allows for any nitrogen-containing compound to be quantitated as long as the number of nitrogens are known. The HPLC-CLND provides a new detection method for analytes that are not available in large quantities or have unknown chemical or physical characteristics such as oxidation products, metabolites, or impurities. Ethoxyquin is a primary antioxidant that is used to preserve many food products and animal feeds. HPLC-CLND is used in the study of the oxidation products of ethoxyquin because limited quantities of these compounds are available and subsequent calibration curves are difficult to maintain. HPLC-CLND as a new method of detection has been evaluated for its equimolarity of response, linear range, limit of detection, and limit of quantitation.

Ethoxyquin: An Antioxidant Used in Animal Feed

“…This finding suggests that an organism is using EQ instead of natural antioxidants. High efficiency of this antioxidant results not only from chemical features of EQ itself but also from the fact that products of its oxidation also possess antioxidative properties [ 12 , 39 , 41 ].…”

“…According to He and Ackman [ 46 ] the following oxidization products of EQ dominate in fish meal and fish feed: 2,6-dihydro-2,2,4-trimethyl-6-quinolone (QI) and 1,8′-di(1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) (EQDM). At high storage temperature neither QI nor EQDM accumulates; however, another product of EQ oxidation, 2,4-dimethyl-6-ethoxyquinoline, is stable [ 41 ]. As it was pointed out earlier, ethoxyquin oxidization products also possess antioxidative properties.…”

Chemiluminescence detection in HPLC and CE for pharmaceutical and biomedical analysis

“…The HPLC-CLND offers a new detection method for analytes that are not available in large quantities. The study of limited quantities of oxidation products of ethoxyquin was conducted using the HPLC-CLND system (Brannegan et al, 2001).…”

Hollow-fiber liquid-phase microextraction for the direct determination of flumequine in urban wastewaters by flow-injection analysis with terbium-sensitized chemiluminescence

“…by coupling to a flow-injection system [25][26][27] or other analytical systems as HPLC [28][29][30] or CE [31]. Analytical methods based on CL detection combined with flow-injection analysis (FIA-CL) have some advantages over HPLC, mainly with respect to analysis time (since carrier flows are higher than those usually found for mobile phases) and cost (due to of the use of aqueous solvents instead of organic solvents, peristaltic pumps instead of high-pressure pumps, etc.…”

“…Chemiluminescence (CL) methods have been successfully applied to the determination of fluoroquinolone antibiotics in different matrices (pharmaceuticals, biological fluids, animal tissues, etc.) by coupling to a flow‐injection system or other analytical systems as HPLC or CE . Analytical methods based on CL detection combined with flow‐injection analysis (FIA–CL) have some advantages over HPLC, mainly with respect to analysis time (since carrier flows are higher than those usually found for mobile phases) and cost (due to of the use of aqueous solvents instead of organic solvents, peristaltic pumps instead of high‐pressure pumps, etc.…”