Applicability of Pressurized Liquid Extraction for Melamine Analysis in Pet Foods with High-Performance Liquid Chromatog
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Applicability of Pressurized Liquid Extraction for Melamine Analysis in Pet Foods with High-Performance Liquid Chromatography with Diode Array Detection Byungchul Kim & Lawrence A. LeBlanc & Rodney J. Bushway & L. Brian Perkins
Received: 12 June 2009 / Accepted: 31 August 2009 / Published online: 24 September 2009 # Springer Science + Business Media, LLC 2009
Abstract A pressurized liquid extraction (PLE) method was developed for melamine analysis in pet foods. The PLE method which utilized an accelerated solvent extraction (ASE®) system was also compared with sonication and polytron extraction methods. The parameters for the optimized PLE method were temperature (75°C for wet pet food, 125°C for dry pet food), pressure (1,500 psi), static time (10 min), flush volume (40%), purge time (1 min), and number of cycles (1). Recoveries obtained by PLE method were significantly higher (P≤0.05) than those of sonication and polytron methods for dry pet food samples. For the analysis of adulterated pet foods, PLE resulted in the highest melamine content followed by sonication and polytron. Using PLE, samples fortified with melamine at 2.5 and 100 mg kg−1 resulted in recoveries ranging from 55% to 90% for wet samples and from 90% to 116% for dry samples. Low recovery rate from wet samples at low spike level (2.5 mg kg−1) may have been caused by co-aggregation of polysaccharide and protein with melamine due to low pH during solid-phase extraction cleanup. Limit of detection and limit of quantification values were 0.5 (mg kg−1) and 1.0 (mg kg−1) for dry samples. Overall, PLE had the best extraction efficiency compared to sonication and polytron, proving PLE to be a useful tool for melamine analysis of pet foods. Keywords Melamine . Pet Food . Pressurized Liquid Extraction . HPLC . Diode Array Detection
B. Kim : L. A. LeBlanc : R. J. Bushway : L. B. Perkins (*) Department of Food Science and Human Nutrition, University of Maine, Orono, ME 04469-5735, USA e-mail: [email protected]
Introduction In 2007, adulterated pet foods resulted in major recalls throughout the USA. It was found that imported ingredients from China such as wheat gluten and rice protein used to make pet foods were adulterated with melamine (US FDA 2008a). In 2008, baby formula contaminated by melamine caused more than 50,000 babies in China to have kidney problem, along with a few deaths related to this condition (US FDA 2008b). It is thought that the nitrogen-rich compound melamine (1,3,5-triazine-2,4,6-triamine) was intentionally added to the pet food ingredients or baby formula to increase nitrogen levels, so that the final products would appear to have sufficient protein content (World Health Organization 2008). Melamine and cyanuric acid can combine in water to form a melamine cyanurate complex which is considered the causative agent for the kidney disease (He et al. 2008; Cianciolo et al. 2008; Reimschuessel et al. 2008). Recently, various analytical methods have been used to determine melamine concentrations in different matrices such as cer
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