Determination of Calcium Content in Crude Oil by Spectrophotometric Method

Two spectrophotometric methods ACBK and TB-ASA were developed for the determination of calcium content in crude oil. The results show that the existence of magnesium ion decreases the precision of measurements for TB-ASA method, while the disturbance of magnesium ion can be eliminated by ACBK method due to the dualwavelength spectrophotometery. The optimal conditions include the dual wave length of 528 nm and 541 nm, pH of buffer solution of 10.5, color time of 30 min, and a color agent of 3 mL ACBK solution (w = 0.000 5). The regression equation is c = 446.07ΔA + 0.123 9 with R2 = 0.999 for ACBK spectrophotometery. Compared with the inductively coupled plasma atomic emission spectrometry (ICPAES) method, the ACBK dualwavelength method is more simple and precise while similar results are obtained.