<span name="style_bold">Objective:</span> Analytical methodology was validated for the determination of magnesium in foods by atomic absorption flame spectroscopy. <span name="style_bold">Material and Methods: </span>Foods that are eaten cooked were baked in the usual manner of consumption in Costa Rica, and samples were taken for moisture determination. The digestion of the samples was made in a microwave oven and magnesium content measured by atomic absorption flame spectroscopy. Validation of the methodology was carried out using magnesium standard solutions traceable to NIST ® and certified traceable, reference materials. <span name="style_bold">Results: </span>The linearity range was (0,021 to 0,65) mg/L with a correlation coefficient of 0,992. The detection and quantification limits obtained were 0,021 mg/L and 0,037 mg/L, respectively. The sensitivity calibration was 0.688 ALmg-1 and the sensitivity was 215 Lmg-1. The accuracy was evaluated in terms of reproducibility, the RDSr value was 1.1 %. The accuracy was determined using three standards certified by NIST ®, SRM 1846 Infant Formula with a reported value for magnesium (538 ± 29) mg / kg, SRM 1846 Bovine Muscle Powder with a reported value for magnesium (960 ± 95) mg / kg, and SRM 8415 Whole Egg Powder with a reported value for magnesium (305 ± 27) mg / kg in mass; in the three cases, the bias obtained, on average, was -0.0014 mg/L. <span name="style_bold">Discussion: </span>46 foods selected from the Costa Rican food basket were analyzed, fresh or cooked in the usual way of consumption, without adding additives. Foods containing magnesium were: legumes (chickpeas, lentils, black and red beans), grains and cereals (white and pre-cooked rice), dairy products (whole milk powder, mozzarella cheese, fresh cheese), vegetables (sweet potato, garlic, sweet plantain), grains (beans, lentils, chickpeas), beef (tilapia, chicken breast, loin and beef liver), fruits (bananas both creole and exportation-quality), industrial products (bread made from wheat flour as well as corn tortillas).46 foods selected from the Costa Rican food basket were analyzed, fresh or cooked in the usual way of consumption, without adding additives. Foods containing magnesium were: legumes (chickpeas, lentils, black and red beans), grains and cereals (white and pre-cooked rice), dairy products (whole milk powder, mozzarella cheese, fresh cheese), vegetables (sweet potato, garlic, sweet plantain), grains (beans, lentils, chickpeas), beef (tilapia, chicken breast, loin and beef liver), fruits (bananas both creole and exportation-quality), industrial products (bread made from wheat flour as well as corn tortillas).

dietary minerals; food; magnesium