Development of ultrasound-assisted emulsification microextraction for determination of thiocynate ion in human urine and saliva samples

Ultrasound-assisted emulsification microextraction (USAE-ME) procedure coupled with UV–vis spectrophotometric measurement has been developed for determination of thiocyanate ion (SCN−) in water and biological fluids samples. The method is based on protonation of SCN− ions in acidic medium and extraction of thiocyanic acid into fine droplets of chloroform as an extraction solvent contains rhodamine B (RhB). The RhB was protonated in presence of thiocynanic acid to form highly colored ion-pair complex of [thiocynate][RhBH+] in chloroform, which used for subsequent spectrophotometric determination of SCN− ions. Experimental parameters for both spectrophotometric reaction and USAE-ME procedure have been optimized. Under optimized conditions the calibration curve for SCN− showed good linearity in the range of 38.0–870.0 ng mL−1 (R2 = 0.9967). The limit of detection (S/N = 3) and preconcentration factor were 5.0 ng mL−1 and 40, respectively. Relative standard deviation for determination of 200 ng mL−1 of SCN− was 2.8% (n = 5). The proposed method has been successfully applied for determination of SCN− ion in tap water, mineral bottled water and human saliva and urine samples with an average recovery of 99.2%.