Automated fluorometric determination of vitamin C in foods.

Two automated fluorometric methods were compared with the official AOAC methods for determining vitamin C in fortified ready-to-eat cereals, fruits, vegetables, baby foods, flour products, pet foods, meats, frozen dinners, juices, and nutritional health bars. Each sample was analyzed in duplicate on 2 days and included a recovery study on all products. Egberg's semiautomated method (Method 1) and Roy's automated method (Method 2) were compared with the manual AOAC tritrimetric and fluorometric methods. The correlation factor for Methods 1 and 2 were 0.999 and 0.979, respectively, when compared with the AOAC methods. The recovery study showed average recoveries of 97.8% for Method 1, 99.3% for Method 2, and 100.6% for the AOAC methods. The results suggest that Method 1 is the method of choice for the majority of the products analyzed.

High pressure liquid chromatographic determination of sugars in various food products.

A high pressure liquid chromatographic (HPLC) method has been developed which is fast, simple, specific, and reliable over a wide range of sugar concentrations in a variety of food matrices. With few exceptions, sample preparation is simple, requiring only a water-ethanol extraction, followed by a rapid mini-column cleanup before injection into the HPLC system. The majority of samples can be prepared for analysis within 1--1 1/2 hr, and the following sugars are separated in less than 45 min: fructose, glucose, sucrose, maltose, lactose, melibioals, chocolate products, chocolate sirups, cookies, health food products, molasses, preserves, processed fruits, and soy protein products.

High performance liquid chromatography determination of sulfamethazine at low levels in nonmedicated swine feeds.

A method for the determination of sulfamethazine at the 0.5 ppm level by high performance liquid chromatography (HPLC) has been shortened and simplified by use of a mini-column clean-up procedure. Fortified feed samples were extracted with acetonitrile, concentrated, and redissolved in the mobile phase. Sulfamethazine was separated from most extraneous material by a mini-column of C18/Porasil B and AX/Corasil, and analyzed by HPLC at 254 nm. Liquid standard solutions were used to fortify four formulated swine feeds and corn sample each at three levels, giving an average recovery of 98% and a relative standard deviation of 7.3%. Tests were run using 32 antibiotics and drugs to determine if they would interfere. Most of these substances were not eluted under the conditions used. Compounds which absorbed at the wavelength used did not interfere with the sulfamethazine peak.