Preparation of biological reference materials at LAN – IPEN – CNEN/SP

Abstract

Three biological reference materials were prepared to be used in interlaboratory programs and/or proficiency tests, as well as, for calibration of analytical instruments and validation of analytical methods for environmental trace elements: A Perna perna mussel reference material was produced and certified by means of an interlaboratory comparison. The material was designed as a quality assurance tool for element biomonitoring studies along the Brazilian seashore. For the preparation of the Brazilian mussel reference material, 164kg of Perna perna (Linnaeus, 1758) mussels were purchased from a single producer, from Cocanha Beach in Caraguatatuba City, São Paulo State North Shore where mussels are cultivated by the longline system. After cleaning, freeze-drying and homogenization, the mussel samples were packed in 171 bottles and, the material was irradiated with a gamma ray dose of 5 kGy to enhance its stability. The certified mass fraction values and associated expanded uncertainties were obtained for Al, As, Ca, Cd, Cl, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Se, Th and Zn at the certification campaign. A fish tissue reference material was produced in the context of an International Atomic Energy Agency (IAEA) project aiming analytical quality improvement for laboratories of the Latin American and Caribbean region. Whitemouth croake (Micropogonias furnieri), known as corvina, was the chosen species due to its low cost and high consumption in Latin America countries. For preparation, about 300kg of fish was collected and only the edible parts were used. After adequate processing, the fish material was bottled in 534 bottles with approximately 25g each. The reference values and associated expanded uncertainty (k = 2) were established for As, Cd, Cu, Fe, K, Mn, Na, Se and Zn; Finally, a bovine kidney reference material to be used in the quality control of meat products was prepared using 35 kg of fresh bovine kidney from cattle reared under controlled feeding conditions. The preparation resulted in a final batch of 175 flasks. It was possible to assign values to 20 elements with their respective uncertainties, being 9 certified values (As, Cu, Fe, K, Mg, Mn, Na, Se and Zn), 10 indicative values (Br, Ca, Cd, Cl, Co, Cs, Hf, Mo, P and Rb) and 1 as additional information (Hg). All the three reference material production projects took advantage of the unique metrological properties of Instrumental Activation Analysis (INAA) not only in the certification process but also in the homogeneity and stability assessment following ISO Guide 30 series recommendations.