Cyclamate derivatization

Another approach would be to derivatize cyclamate prior to analysis. Cyclamate can be determined by HPLC and UV detection at 314 nm after conversion to A/,/V-dichlorocyclohexyl-amine. Derivatization can be carried out directly in the sample or after extraction and cleanup. /V,/V-Dichlorocyclohexylamine is separated on a reverse-phase column (Nucleosil Cl8 or Fine-pak SIL Cl8 T-5) with a mobile phase of methanol water, 8 2 v/v (43,46). Cyclamate can also be determined at 585 nm after postcolumn derivatization with methyl violet 2B as described by Lawrence and Charbonneau (16). 

Cyclamate can also be determined after its oxidation to cyclohexylamine. Cyclohexy-lamine can be quantified by HPLC with trinitrobenzenesulfonic acid precolumn derivatization and UV detection (72). Cyclohexylamine can also be converted into a fluorescent derivative, separated on a Cl8 reversed-phase column with acetonitrile Na2HP04 buffer (64 36, v/v), and quantified at 350 and 440-650 nm of excitation and emission, respectively (73). 

M Lehr, W Schmid. Simple and specific HPLC method for determination, after derivatization to N,N-dichlorocyclohexylamine, of cyclamate in beverages containing fruit juice. Z Lebensm Unters Forsch 192(4) 335-338, 1991. 

I Casals, M Reixach, J Amat, M Fuentes, L Serra-Majem. Quantification of cyclamate and cyclo-hexylamine in urine samples using high-performance liquid chromatography with trinitrobenzenesul-fonic acid pre-column derivatization. J Chromatogr A 750(1-2) 397-402, 1996. 

J Rueter, DIU Raczek. Sensitive and selective HPLC procedure with pre-chromatographic derivatization for the determination of cyclamate in foods. Z Lebensm Unters Forsch 194(6) 520-523, 1992. 

Cyclam, or 1,4,8,11-tetraazacyclotetradecane is a popular macrocyclic ligand for d-tran-sition metal coordination chemistry. It also coordinates to lanthanide ions, although much less strongly than the better size-adapted cyclen. As for the latter, however, derivatization of the amine functions by amide, carboxylate, or phosphinate groups considerably improves the coordination ability of the macrocycle. 

Gas chromatography Acesulfame-K, aspartame, cyclamate, saccharin, and stevioside are determined by gas chromatography, but the main drawback of this technique is that a derivatization is required. Acesulfame-K is methylated with ethereal diazomethane, aspartame is converted into its N- 2-methylpropoxycarbonyl) methyl ester derivative, menthol and isobutyl chloroformate are used to convert aspartame to 3-[(isobutoxycarbonyl)amino]-4-[[a-(methoxycarbonyl)phenethyl]amino]-4-oxobutyric acid, cyclamate is determined as cyclohexene resulting from the reaction with nitrite, saccharin is converted to N-methylsaccharin, and stevioside is hydrolyzed. Detection is carried out utilizing flame-ionization, flame-photometric electron-capture detectors or nitrogen-phosphorus detection. 

Cyclamate salts are not readily detected by spectroscopic techniques. So, a chemical derivatization is often performed in order to improve the characteristics of cyclamate for detection. Two spectrophotometric FIA methods were proposed. Gouveia et al. [79] proposed a procedure based on the reaction of cyclamate with an excess of nitrite solution. The unconsumed excess of nitrite is monitored spectrophotometrically using the Griess reaction to eliminate interference caused by dye additives, an alumina column was incorporated into the flow system and used for both colorless and colored samples. 

Cabero et al. [80] developed a method based on the conversion of cyclamate to cyclo-hexylamine and the subsequent reaction with l,2-naphthoquinone-4-sulfonate, yielding a spectrophotometrically active derivative, which is detected at 480 nm thus, other sweeteners, such as saccharin or aspartame, do not interfere in these determinations. The hydrolysis step is performed batchwise by treatment of cyclamate with hydrogen peroxide and hydrochloric acid, while the cyclohexylamine derivatization is carried out in the flow injection system (Figure 24.9). Rocha et al. [81] reported a flow system based on multicommutation for fast and clean determination of cyclamate. The procedure exploits the reaction of cyclamate with nitrite in an acidic medium and the spectrophotometric determination of the excess of nitrite by iodometry. The flow system was designed with a set of solenoid micropumps to minimize reagent consumption and waste generation (Figure 24.10). 

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