Aspartame: analysis

Sweeteners can be roughly divided into two groups bulk and intense sweeteners. Prodolliet (1996) and Gloria (2000) reviewed thoroughly the analysis and properties of intense sweeteners acesulfame-K, alitame, cyclamate, aspartame, glycyrrhizin, neohesperidin DC, saccharin, stevioside, sucralose and thaumatin. They are generally used in low calorie products such as diet... 

There is a recent trend towards simultaneous CE separations of several classes of food additives. This has so far been applied to soft drinks and preserved fruits, but could also be used for other food products. An MEKC method was published (Lin et al., 2000) for simultaneous separation of intense sweeteners (dulcin, aspartame, saccharin and acesulfame K) and some preservatives (sorbic and benzoic acids, sodium dehydroacetate, methyl-, ethyl-, propyl- and isopropyl- p-hydroxybenzoates) in preserved fruits. Ion pair extraction and SPE cleanup were used prior to CE analysis. The average recovery of these various additives was 90% with good within-laboratory reproducibility of results. Another procedure was described by Frazier et al. (2000b) for separation of intense sweeteners, preservatives and colours as well as caffeine and caramel in soft drinks. Using the MEKC mode, separation was obtained in 15 min. The aqueous phase was 20 mM carbonate buffer at pH 9.5 and the micellar phase was 62 mM sodium dodecyl sulphate. A diode array detector was used for quantification in the range 190-600 nm, and limits of quantification of 0.01 mg/1 per analyte were reported. The authors observed that their procedure requires further validation for quantitative analysis. 

This technique has been established for many years particularly for water, soil and feeding-stuff analysis, where a large number of analyses are required for quality control or monitoring purposes. A number of applications have been published for food additives including aspartame (Fatibello et al., 1999), citric acid (Prodromidis et al., 1997), chloride, nitrite and nitrate (Ferreira et al., 1996), cyclamates (Cabero et al., 1999), sulphites (Huang et al., 1999 AOAC Int, 2000), and carbonate, sulphite and acetate (Shi et al., 1996). Yebra-Biumm (2000) reviewed the determination of artificial sweeteners (saccharin, aspartame and cyclamate) by flow injection. 

Use print and electronic resources to study compounds that have been produced as diet aids, such as aspartame and olestra. How do these compounds work Are there drawbacks or risks involved in using these compounds Choose one compound, and conduct a risk-benefit analysis. 

CE has been applied extensively for the separation of chiral compounds in chemical and pharmaceutical analysis.First chiral separations were reported by Gozel et al. who separated the enantiomers of some dansylated amino acids by using diastereomeric complex formation with Cu " -aspartame. Later, Tran et al. demonstrated that such a separation was also possible by derivatization of amino acids with L-Marfey s reagent. Nishi et al. were able to separate some chiral pharmaceutical compounds by using bile salts as chiral selectors and as micellar surfactants. However, it was not until Fanali first showed the utilization of cyclodextrins as chiral selectors that a boom in the number of applications was noted. Cyclodextrins are added to the buffer electrolyte and a chiral recognition may... 

For the analysis and separation of benzoic acid, caffeine, aspartame, and saccharin in dietetic soft drinks, a HPLC system consisting of a Varian MCH-5N-CAP 150 x 4.6 mm column and a variable wave length UV/VIS detector was recommended [32]. The mobile phase is a gradient, beginning with 90% 0.01 M KH2PO4 (pH = 2) and methanol, and ending in 25 minutes with 60 % buffer / 40 % methanol. 

Aspartame, sweetness production, 28-30 Aspartic acid, as food material, 138-147 Aspartic acid dipeptides, taste, 141-142r Astringpncy, sensation based on generalized membrane responses, 16-18 Automated data analysis and pattern recognition tool kit, 102... 

M.9 In a combustion analysis of a 0.152-g sample of the artificial sweetener aspartame, it was found that 0.318 g of carbon dioxide, 0.084 g of water, and 0.0145 g of nitrogen were produced. What is the empirical formula of aspartame The molar mass of aspartame is 294 g-mol. What is its molecular formula ... 

Herrmann et al. (24) used ion-pair chromatography for the determination of cyclamate. The efficiency of LiChrosorb RP-18 and Hypersil MOS 3 with a mobile phase of 5 mM tetrabutylammonium p-toluenesulfonate, pH 3.5, mixed with 12% methanol for the separation of cyclamate from other sweeteners was investigated. With the first column, cyclamate separated from saccharin, but the second was the recommended column for the analysis of cyclamate, saccharin, aspartame, and dulcin in a single run. 

During HPLC analysis of aspartame, the most commonly used stationary phase is reverse-phase Cl 8. Two main types of mobile phase have been used an alcohol (methanol or isopropanol)... 

Various methods have been developed for the simultaneous determination of several sweeteners in a single run. Most of the methods described in the literature and summarized in Table 3 have been developed for the separation of three sweeteners, especially for saccharin, acesulfame-K, and aspartame. Herrmann et al. (24), Veerabhadrarao et al. (27), and Hausch (66) developed methods for the simultaneous determination of four sweeteners. Prodolliet and Bruelhart (33) and Wu et al. (47) separated five sweeteners. The most comprehensive method is the one developed by Lawrence and Charbonneau (16), which allows the simultaneous analysis of seven sweeteners. With the increased number of sweeteners available and their use being approved for use in specified food products and beverages by different countries, methods capable of separating several sweeteners simultaneously are still needed. 

G Verzella, G Bagnasco, A Mangia. Ion-pair high-performance liquid chromatographic analysis of aspartame and related products. J Chromatogr 349(1) 83-89, 1985. 

E Mueller, H Jork. Analysis of aspartame-containing cola drinks by hydrophobic chromatography on Fractogel TSK. Dtsch Lebensm Rundsch 86(8) 243-247, 1990. 

JC Scherz, JC Monti, R Jost. Analysis of the peptide sweetener aspartame by liquid chromatography. Z Lebensm Unters Forsch 177 124-128, 1983. 

In summary, to maximize the stability of aspartame/acesulfame K blends in soft drinks, formulate on the right-hand side of the synergy curve. This is also an example of how the analysis of sweetener levels in a soft drink may not always give an accurate reflection of the perceived sweetness/acceptability of a drink. 

In dry beverages aspartame is stable for several years. Analysis of aspartame is generally by HPLC (MacArthur et al., 2002). 

Synergism occurs with fructose (Hyvonen el al., 1978), aspartame, cycla-mate (Bakal, 1987) and sucralose (Tate Lyle Pic, 1986). Negative synergy (i.e. suppression) occurs with acesulfame K blends. Analysis of saccharin is usually done using HPLC (Halm Gilikson, 1987) or spectrophotometric methods (Ramappa Nayak, 1983). 

Two methods have been published which were designed to analyse a range of sweeteners and preservatives in one run. The fust method, published in German by Hagenauer-Hener et al. (1990), describes the analysis of aspartame, acesulfame K, saccharin, caffeine, sorbic acid and benzoic acid in soft drinks and foods. The method relies on a similar system to that given above but with a less complex solvent system (Figure 10.5). The solvent system has been modified to include a gradient portion to elute the preservatives more quickly. 

Acesulfame K was intr oduced as a high-intensity sweetener at around the same time as aspartame. It too is much sweeter than sucrose but is also stable under the low pH conditions of soft drinks. Its analysis in a soft drink is relatively straightforward and an HPLC procedure is given by Grosspietsch and Hachenburg (1980). 

G. Verzella and A. Mangia, High-performance liquid chromatographic analysis of aspartame, J. Chromatogr., 346 411 (1985). 

Aspartame has been reported in a variety of solvatomorphic forms, namely one anhydrous form, two hemihydrate forms (Forms I and II) and a di-hemihydrate [8]. The structural details of the crystal properties have been discussed earlier, and will also be addressed in the discussion on thermal analysis. The room temperature transition between the hemihydrate and di-hemihydrate forms occurs between relative humidities of 40% and 60%. 

Leung et al [8] reported that the thermogravimetric analysis (TGA) of aspartame hemihydrate (Forms I and II) and aspartame dihemihydrate displayed mass losses for water (first mass loss) and methanol (second mass loss). This information is summarized in the following table ... 

Aspartame has been assayed by a flow injection analysis biosensor employing an immobilized enzyme (pronase) which cleaves the peptide bond. The resulting phenylalanine methyl ester is then detected by an L-amino acid oxidase electrode. This method was applied to analysis of aspartame in foods [82]. 

A number of spectrometric methods have been proposed for the quantitative analysis of aspartame. These include colorimetric [56-60], UV absorption [61-66], and fluorescence methods [67, 68]. 

Conditions for the High Performance Liquid Chromatographic Analysis of Aspartame... 

Two studies have compared HPLC and CZE methods for aspartame [78, 80]. Although the CZE method was found to be faster than the HPLC method and had better resolution, it was also found to be ten to twenty fold less sensitive. While this may not be important when raw materials are assayed, it may be of concern in the analysis of biological samples. 

Ottinger el al.2S6 have applied their comparative taste dilution analysis (cTDA) to examine the extractable products from heated aqueous D-glucose and L-alanine that were not solvent-extractable. One HPLC fraction proved to be a strong sweetness enhancer. It was isolated and submitted to LC-MS and NMR, both ID and 2D the results, together with its synthesis from HMF and alanine, unequivocally identified it as the inner salt of /V-( I -carboxycthyl)-6-(hydroxy-methyl)pyridinium-3-ol (alapyridaine, Structure 45). It has no taste on its own, which in many applications would be an advantage. Depending on the pH, it lowers the detection threshold of sweet sugars, amino acids, and aspartame, the... 

Thevaluesof k2+ = 2.05xl0 5sec-1M-1 and k0 = 1.50 sec 1M 1 are estimated. Substituting these values into Equation (5.174) followed by nonlinear regression analysis gives other k values. Intuitively from the profile of pH 2 to 4, one can assume kj 0 = 0. As demonstrated for monoprotic and diprotic weak acids and weak bases, the pH-rate constant profile is dependent on the kinetic pathway of the hydrolysis. It can be seen from Figure 5.32 that at pH 3 to 4 and pH 4 to 9, k2>0 and k0 0 are the predominant processes of the hydrolysis of aspartame, respectively. 

E. Preparation of instrument for analysis of caffeine, saccharin, benzoate, and aspartame from beverages... 

E. Preparation of Instrument for Analysis of Caffeine, Saccharin, Benzoate, and Aspartame from Beverages ... 

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