Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromotography and Gas Chromotography-Mass Spectrometry

Journal of the Arkansas Academy of Science Volume 52 Article 9 1998 Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromotography and Gas Chromotography-Mass Spectrometry Cheryl L. Fossler University of Arkansas at Little Rock Frank L. Setliff University of Arkansas at Little Rock Ali U. Shaikh University of Arkansas at Little Rock Follow this and additional works at: https://scholarworks.uark.edu/jaas Part of the Organic Chemistry Commons Recommended Citation Fossler, Cheryl L.; Setliff, Frank L.; and Shaikh, Ali U. (1998) "Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromotography and Gas Chromotography-Mass Spectrometry," Journal of the Arkansas Academy of Science: Vol. 52 , Article 9. Available at: https://scholarworks.uark.edu/jaas/vol52/iss1/9 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact . Journal of the Arkansas Academy of Science, Vol. 52 [1998], Art. 9 Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromatography and Gas Chromatography-Mass Spectrometry Cheryl L. Fossler, Frank L. Setliff, and AliU. Shaikh* Department of Chemistry University of Arkansas at Little Rock Little Rock, AR 72204 *Corresponding Author Abstract Six 2,5- and 5,6- dihalonicotinic acids in a mixture were converted to their corresponding methyl esters and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Four methods of conversion were compared for their GC sensitivity, efficiency and analysis time. In Method #1, using HC1 and methanol as the reagents, the displacement of the halogens by chlorine (from HC1) at 2- and 6-positions was a common occurrence, rendering the method inefficient. InMethod #2 (BF3/methanol), the displacement of halogens by methoxide was evident. Method #3 (dicyclohexylcarbodiimide/methanol) produced a mixture of derivatives with a poor yield. Method #4 (diazomethane) gave a quantitative yield of the corresponding methyl esters without any side reactions and was suitable for analytical method development. The latest method provided short analysis time with all six methyl dihalonicotinates eluting within nineteen minutes. The resolution of the ester peaks was excellent and the detection limit was about 1 ng/|iL for the dihalonicotinic acids. Introduction Nicotinic acid, also known as niacin, is an essential vitamin that contributes to the metabolism of carbohydrates and fats, the production of certain hormones, the functioning of the nervous and digestive systems, and the maintenance of healthy skin (Clayman, 1989). It is interesting, therefore, to study some of its derivatives to determine any beneficial properties. As many as twenty-six of the possible thirty-two 2,5- and 5,6-dihalonicotinic acids have been synthesized (Setliff, 1970; Setliff and Rankin, 1972; Setliff and Price, 1973; Setliff and Lane, 1976; Setliff and Greene, 1978; Setliff and Huie, 1981). The primary purpose of the synthesis of these compounds was to investigate their potential anti-arthritic, anti-viral, anti-psoraisis, or anti-bacterial properties. Other researchers have also studied these compounds as potential hypolipidemic agents (Gacek et al., 1972) Consequently, it has become quite important to develop sensitive analytical methods to determine the presence of these compounds in trace quantities, so that their potential application as pharmaceutical or agricultural agents can be evaluated in terms of their potency, toxicity, and metabolic transformation in living systems. A survey of the literature reveals no analytical method available for the separation of the dihalonicotinic acids in a mixture. However, nicotinic acid and some of its other derivatives have been analyzed by high performance liquid chromatography (Iwaki et al., 1996; Manceau et al., 1992) and gas chromatography and gas chromatography-mass spectrometry (Zoellner, 1994). The HPLC method was employed to study the bioconversion of nicotinic acid to nornicotine in biological matrices such as blood plasma and urine (Manceau et al., 1992). The GC and GC-MS methods have been used to investigate the structural fragmentation patterns of the mono and diacylglycerol derivatives of nicotinic acid (Zoellner, 1994). The purpose of the present research was to develop an acceptable analytical method for the separation and quantification of several dihalonicotinic acids in a mixture using GC and GC-MS techniques. Four methyl esterification methods, well-documented in the literature, were compared in terms of GC sensitivity, efficiency, and analysis time using six dihalonicotinic acids in a mixture as a test sample, as listed in Fig. 1. The methods used were (1) HCl/methanol, (2) BF3/methanol, (3) Dicyclohexylcarbodiimide/methanol, and (4) diazomethane. These methods are commonly used for the methyl esterification of a variety of aliphatic and aromatic acids. Method #4 has been used earlier to synthesize the methyl esters of eight dihalonicotinic acids (Setliff and Huie, 1981). The conversion into the esters was about eighty percent in most cases. However, halogen replacement by chlorine at 2- and 6- positions from HC1 produced in-situ was observed for some esters when the preparation of the esters was attempted by reacting the dihalonicotinic acids with SOC1 2 and methanol. Journal of the Arkansas Academy of Science, Vol. 52, 1998 Published by Arkansas Academy of Science, 1998 46 46 Journal of the Arkansas Academy of Science, Vol. 52 [1998], Art. 9 Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromatography and Gas Chromatography-Mass Spectrometry sis of organic acids in order to increase the volatility of the test compounds so that they willbe more amenable to separation in a GC column with little or no peak-tailing. The success of a method depends largely on the structures of the acids, and to some extent on their solubilities and other physical characteristics. It is imperative, therefore, to attempt various methods in order to develop the most suitable analytical method for a class of compounds. Materials and Methods AVarian Model 3400 gas chromatograph, coupled with a flame-ionization detector, was used to perform the GC analysis of the compounds. The GC-MS analyses were conducted with a Varian 3400 GC coupled with a Varian Saturn IIIon-Trap Detector, and also with a Hewlett-Packard Model 5890 Series IIGC with a Hewlett-Packard Model Table 1:The six dihalonicotinic acids used for the analy (...truncated)