Extraction methods for quantifying iron, calcium and magnesium in a historic Brickwork produced during the Spanish colonial period in the Philippines

This study demonstrates the feasibility of performing chemical analyses on heritage materials in the Philippines. Four extraction methods were evaluated based on the percentage of iron, calcium and magnesium in a clay brick sample obtained from an old Spanish colonial period church at Ilocos Norte. Aqua regia (1:3 HNO 3 :HCl, v/v) solvent was used to extract these elements by conventional hot plate digestion. The extraction methods are: digesting the sample directly with aqua regia (M1), sample pre-digested with NH 4 Cl and ethyl alcohol prior to the actual digestion (M2) and soaking the sample with aqua regia for 24 hours (M3) and 48 hours (M4) before digestion. Atomic absorption spectroscopy (AAS) was employed to quantify the concentration of the intended elements. The percentage composition of iron ranges from 4.193 to 4.418%, calcium from 0.123 to 0.203%, and magnesium from 2.346 to 2.458%, respectively. Energy-dispersive X-ray spectroscopy (EDX) analysis was done to support the data obtained from AAS. M1 was more effective in extracting calcium from the brick sample, while M2, M3 and M4 were useful for extracting iron and magnesium. Infrared spectroscopy (IR) provided a basic mineralogical composition of the sample, with peaks that were attributed to quartz, kaolinite, calcite, silicates and hematite