Analytical application of pyridine type ionic liquid as solid solvent

Copper (Cu2+) ion was determined at micro level by diethyldithiocarbamate (DDTC) spectrophotometry after temperature-dependent solid–liquid separation using N-butyl pyridinium hexafluorophosphate ([BPy]PF6) as a solid solvent and DDTC as an extractant. The results showed that ions can be extracted 100% by DDTC–[BPy]PF6 at pH = 10·20. The extracted species was neutral Cu(DDTC)mCl2 (m = 1) based on slope analysis in the Cu2+–[BPy]PF6–DDTC temperature-dependent solid–liquid separation system. The recovery of Cu2+ extracted into DDTC–[BPy]PF6 can be achieved using 2 mol L−1 HNO3 as stripping agents. Back extraction method was adopted for the detection and quantification of Cu2+ ions using the DDTC spectrometry. The calibration curve was Y = 0·00328 + 0·10279X (correlation coefficient = 0·99922), the linear calibration range was 7·68 × 10−2 0·768 μg mL−1 and the limit of detection was 1·28 × 10−2 μg mL−1 for Cu2+. In this method, the contents of Cu2+ in Tieguanyin tea were determined with relative standard deviations (n = 5) of 2·82% and recoveries in the range of 96·6–108·5%.