Atomic absorption measurements were carried out using a Varian AA240 spectrometer with a Mg/Ca hollow cathode lamp light source (7 mA lamp current). Atomization was performed using an air/acetylene flame. The instrument was zeroed with 2% HNO3 and rinsed between each collection with deionized water. Magnesium absorbance was measured at 285.2 nm, and calcium absorbance was measured at 422.7 nm. Calibration curves for magnesium/calcium were generated using the previously described standard solutions. Sample data was collected directly after each respective calibration curve was obtained.