Ion chromatography (IC) is a widely used analytical technique for the determination of anionic and cationic analytes in various sample matrices. In modern IC systems, high purity acid, base, or salt eluents are generated electrolytically using deionized water as the carrier. The Reagent-Free Ion Chromatography (RFIC) systems with electrolytic eluent generation make it possible to perform a wide range of ion chromatographic separations using only deionized water as the carrier. For many applications, the RFIC
systems provide improved performance with increased sensitivity and the flexibility to perform isocratic and gradient separations. In addition to saving time, labor, and operating costs, the RFIC systems eliminate errors and problems associated with manual eluent preparation and offer users the benefits of simplicity, ease of use, and improved method reproducibility.
Coupling RFIC technology with Capillary scale systems provides a very unique feature set that offers the end-user greater flexibility and ease of use with respect to system operation and readiness.
Nitrate and nitrite in processed meats and spinach
Nitrate and nitrite salts are often used as food additives in processed meats like bacon, ham, and sausages to stabilize the color of red meat. They also function as preservatives, helping to prevent the growth of microorganisms that cause food poisoning. The presence of nitrite and nitrate in processed meat is believed to increase the risk of cancer in the digestive tract. The reaction between nitrite with secondary and tertiary amines leads to the formation of carcinogenic chemicals known as N-nitroso compounds. The nitrate content of food is also important, as nitrate can be reduced to nitrite by bacterial enzymes present in the posterior part of the tongue and in the stomach under acidic conditions. For these reasons, the use of nitrate and nitrite salts as food additives is strictly regulated worldwide. For example, the European Commission established the maximum allowable concentration for nitrate and nitrite salts in processed meat as 150 mg/kg.
Nitrate and nitrite are also found naturally in vegetables and fruits. The amount of nitrate in vegetables depends on agricultural practices, environmental variables (season, light, temperature, etc.), and genetic factors. Most vegetables usually have low levels of nitrate, with leafy vegetables such as lettuce, spinach, and arugula having the highest levels. Conversely, only trace amounts of nitrite.
Ion Chromatography System
Ion chromatography (IC) is the most used and well-established technique for the analytical determination of nitrite and nitrate. Application Note 112 describes anion exchange chromatography with UV detection for the determination of nitrate and nitrite in meat products.
A Thermo Scientific™ Dionex™ IonPac™ AS11 column was used in that work. In this application note, we developed an IC method using a high capacity version of the Dionex IonPac AS11 column to separate nitrite and nitrate from other anions present in a meat homogenate and slurried spinach. The Dionex IonPac AS11-HC column is a high capacity column that allows relatively large injection volumes, thus facilitating the determination of low nitrate and nitrite concentrations.10 After the separation, nitrate, and nitrite were detected by suppressed conductivity detection. The two food samples were extracted with deionized water and subjected to a series of clean up steps before they were analyzed on the IC system. For more details can be the download of the following application note.