Determination of Metal Ion Content in Animal Feed Using Atomic Absorption Spectrophotometry
Key words: atomic absorption spectrophotometer; animal feed; heavy metal; analytical method. This procedure outlines the accurate determination of essential and toxic metal ions such as calcium, copper, iron, manganese, magnesium, potassium, sodium, and zinc in animal feed samples using an atomic absorption spectrophotometer (AA1800). The method involves sample digestion, calibration, and measurement under controlled conditions to ensure reliable results. 1. Instruments and Equipment - AA1800 Atomic Absorption Spectrophotometer with air-acetylene flame and background correction. - Crucibles made of platinum, quartz, or porcelain (without potassium or sodium). - Glassware (hard glass) boiled in hydrochloric acid before use. - Electric heating plate, water bath, muffle furnace (550°C ± 15°C), analytical balance (0.1 mg accuracy), and hollow cathode lamps for specific elements. - Quantitative filter paper. 2. Reagents and Solutions - Water complying with GB/T 6682 grade III. - Hydrochloric acid (12 mol/L, 6 mol/L, 0.6 mol/L). - Cerium nitrate solution, barium chloride solution, and standard solutions for Cu, Fe, Mn, Zn, Ca, K, Mg, Na. - Blank solutions containing lanthanum and cesium to minimize interferences. 3. Procedure - Sample preparation: Weigh 1–5 g of sample into a crucible, depending on estimated metal content. - Dry ashing: Char the sample on a hot plate, then incinerate in a muffle furnace at 550°C for 3 hours. - Dissolution: Dissolve the residue in hydrochloric acid, filter, and dilute to volume. - Calibration: Prepare standard solutions and plot calibration curves for each metal ion. - Measurement: Analyze sample and blank solutions under the same instrument conditions, subtracting blank absorbance values. - Data correction: Adjust results according to the dilution factor and reference tables for accurate reporting. 4. Results and Reporting - Metal concentrations are calculated from the calibration curves and expressed in mg/kg or g/kg based on the dilution factor. - Table 1 provides correction factors for different concentration ranges, ensuring precision across various levels of metal content. Key words: atomic absorption spectrophotometer; animal feed; heavy metal; analytical technique.
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