Analytical application of pyridine type ionic liquid as solid solvent

Abstract

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%.

Keywords:

• Ions
• Tea
• Temperature dependent solid–liquid separation