Ultrasensitive Determination of Cadmium in Rice by Flow Injection Chemiluminescence Analysis

Based on the enhancing effect of Cd2+ on luminol–Co2+ chemiluminescence (CL) system, a sensitive method for determining picogram Cd2+ in rice by flow injection (FI)–CL was proposed. It was found that the CL intensity increments were proportional to the concentrations of Cd2+, giving a calibration graph linear over the Cd2+ concentrations ranging from 7.0 to 5,000.0 pmol L−1, with a detection limit of 2.0 pmol L−1 (3σ) and relative standard deviations (RSDs) of 3.2, 2.8, and 2.5 % for 30.0, 300.0, and 1,000.0 pmol L−1 Cd2+ (n = 5), respectively. At a flow rate of 2.0 mL min−1, a complete determination of Cd2+ including sampling and washing could be accomplished within 36 s, giving a sample throughput of 100 h−1. The contents of Cd2+ in rice were found to be 0.07–0.10 mg kg−1. The proposed method was also applied to the determination of Cd2+ in spiked human serum samples with recoveries from 95.9 to 106.3 % and RSDs less than 4.0 %.