| The ocean play a fundamental role in driving the global climate change, and sea surface temperature is essential for understanding process that control ocean evolution. Foraminiferal Mg/Ca ratios are now routinely analysed because of their value as indicators of past ocean temperature, and it offers a few distinctive advantages. In this paper, we established a suite of cleaning method prior to Mg/Ca analysis and analysed Mg/Ca ratios on inductively coupled plasma optical emission spectrometry (ICP-OES).We obtained 53 Mg/Ca ratios in planktonic foraminifera (Globeriginoides rubber white) from the core F10-09-01 which was located in the West Philippine Sea (18°40.23′N, 135°37.11′E, 3225m). We applied the"oxidative"cleaning method between"Mg"cleaning method and"Cd"cleaning method.It is also called"Mg"cleaning and it involved a number of discrete sequential steps aimed at removing clay organic matter and Fe-Mn-coatings and so on. This method includes multiple rinses with distilled deionised water (ddH2O) and methanol in an ultrasonic bath followed by removal of silicate minerals under the microscope and oxidation in a warm (90℃) mixture of 30% H2O2/0.1M NaOH solution and typically a single acid leaching step with 250μL 0.001N HNO3 ultrasonicated for 10 seconds. After this process, the sample solution was measured on ICP-OES. Instrument operating conditions are listed as follows: the auxiliary gas flow is 0.5L/min, the nebuliser pressure is 0.2Mpa, the pump rate is 20 rpm, the RF power is 1150KW, the view height is 15.5mm. The short-term(intrarun) precision and long-term(interrun) precision for Mg/Ca ratios, determined from replicate runs of a standard solution containing Mg/Ca=3.333mmol/mol at a Ca concentration of 16 ppm, are <0.5% and 1%.The relative standard deviation of the 53 samples is 2.7%.According to the calibration of Lea(2000): Mg/Ca (mmol/mol) =0.30exp[0.089×SST(℃)], the sea surface temperature of our samples is 28℃±0.3℃.
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