Sodium carbonate in the food industry
Also known as soda ash or disodium carbonate, sodium carbonate (Na2CO3) is widely used in the food and beverage industries, principally as a food/beverage additive (E500) for the purposes of acidity regulation, anti-caking protection and leavening. It is also used as a food ingredient, such as in some pretzels, some types of noodles and in fruit sherbet confectionery. Consequently sodium carbonate is present in a plethora of food and beverages, ranging from dairy products, confectionery, beers, ciders through snack foods and breakfast cereals to condiments. Sodium carbonate is mainly produced from the direct mining of natural mineral resources or via industrial processes whose starting reagent is sodium chloride.
Purity
Whatever the means of production, the final purity and the impurity profiles of a finished product depend on the composition of the raw materials and the production process itself. The acceptability of the purity profile depends of course on intended use of the product. Some impurities of sodium carbonate such as sodium chloride, sulphate, calcium, magnesium, iron, arsenic and heavy metals, may be present as trace quantities throughout various production processes. Levels of chloride and sulphate may indeed be used as markers of anion impurity. International regulatory bodies, such as the US Food and Drugs Administration (FDA) and various pharmacopeias stipulate the required purity levels for substances added to foodstuffs. Sodium carbonate is one such substance where a purity of 99.5 % or more is often required in the raw material. For these reasons, a fast, reliable, comprehensive, sensitive, accurate and easy means of estimating impurity levels in raw material sodium carbonate is needed.
Ion chromatography
A wide range of cations and anions can be determined in sodium carbonate samples by ion chromatography, in which a whole range of ions can be determined in a single chromatographic elution. In this article, we confine ourselves to the analysis of the two marker anions of sodium carbonate, as this is technically a challenge because of the high levels of the carbonate which may interfere with or mask the trace levels of other anions present. Ironically, a mobile phase which includes sodium carbonate may be used, along with an anion suppressor to remove or suppress the separated carbonate ions from the chromatogram. Hence the other anions may be more easily separated and determined, without the need for more protracted sample preparation, other matrix elimination techniques or excessive retention times. Cecil Instruments’ IonQuest modular ion chromatography systems with conductivity detection and anion suppression have been shown to provide for the accurate, fast, reproducible, reliable and sensitive analysis of anions in sodium carbonate. The system software, which is 21 CFR Part 11 compliant makes the ion chromatography systems easy to operate. Processes are easily automated and may be modified and configured with accessories, such as column heater/chillers, other autosamplers, other detectors, post column derivatisation units etc., as and when required. The ability of the IonQuest system C-2 to determine chloride and sulphate ions in samples of sodium carbonate has been clearly demonstrated in extensive evaluation studies which used an experimental configuration involving a conductivity detector and anion suppressor. This detector gives low noise, high sensitivities, low drift, a wide range and fast response times. After some experimentation with regenerants in an anion suppressor, the IonQuest C-2 system was shown to be able to detect low ppm levels of anions in sodium carbonate samples. This high sensitivity was achieved easily with an analysis time of less than 10 minutes per sample (experimental conditions available from the author). Chloride and sulphate ions were also detected and of course yet other anions in sodium carbonate samples can be detected by the same method within the same chromatographic elution. In addition, low ppm levels of cations in sodium carbonate samples, such as calcium and magnesium, can also be detected by the use of a simpler Cecil IonQuest ion chromatography system, whereas low ppm levels of transition and heavy metals in sodium carbonate samples, can be determined by the use of a Cecil Adept isocratic, post column reactor HPLC system.
Overall, our evaluation experiments have shown the suitability of the IonQuest ion chromatography systems to facilitate the quality control of raw ingredient materials for the food and beverage industries in a fast, reliable, comprehensive, sensitive and accurate method.
The author
Ade Kujore, Cecil Instruments Limited
Milton Technical Centre, Cambridge
United Kingdom
email: info@cecilinstruments.com
Tel.: +44 1223 420821
web site: http://www.cecilinstruments.com
