Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation.
A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide, CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon=65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer's law is obeyed in a 1x10(-6) to 2x10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r=0.999) and a detection limit of 3.1x10(-7) mol L(-1), corresponding to 38 microg L(-1). At flow rates of 200 microL min(-1) of the donor stream and 100 microL min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD<2.3% (n=10, 300 microL injections of 1x10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore.
Highly Sensitive Determination of Butyl Xanthate in Surface and Drinking Water by Headspace Gas Chromatography with Electron Capture Detector
A highly sensitive and convenient method for the determination of butyl xanthate in surface water and drinking water was developed by headspace gas chromatography with electron capture detector (HS–GC–ECD). The analytical method was based on the decomposition of butyl xanthate under an acidic condition, generating carbon disulfide, which could be sensitively detected by gas chromatography with electron capture detector. The signal of CS2 from the decomposition of potassium butyl xanthate was directly proportional to the concentration of potassium butyl xanthate over the range 0.7–100 ng/mL. The detection limit at a signal-to-noise ratio of three (S/N = 3) for potassium butyl xanthate was 0.3 ng/mL (~1.6 × 10−9 mol/L), which was more than two orders of magnitude lower than the popular UV methods and close to one order of magnitude lower than the similar headspace gas chromatography–mass spectroscopy method. The relative standard deviation (R.S.D.) within a day and in 3 days for potassium butyl xanthate at both 5 and 50 ng/mL was less than 4.7 %, suggesting good analytical performance of the present method. Good recoveries from 93.3 to 104.7 % were obtained from spiked surface and drinking water samples, indicating that the proposed HS–GC–ECD method was applicable for the quantification of butyl xanthate in surface and drinking water. Compared with other reported methods, the present method is highly sensitive, without sample preparation, and easily extended to the analysis of other xanthates.
Polarography of O-alkylxanthates in acetone: Evidence for existence of tris(o-alkylxanthato) mercury(II) complexes
Summary Polarographic investigation of a series of potassium O-alkylxanthates in acetone has shown that they undergo the following processes at a mercury electrode 2Hg 0 +6ROCS 2 2Hg(S 2 COR) 3 − +4 e 2Hg II (S 2 COR) 3 − +Hg 0 2Hg II (S 2 COR) 2 +2 e (where R is an alkyl group). Analysis of the two waves corresponding to these processes shows qualitative agreement with theoretical predictions for such a mechanism, although the system is complicated by adsorption phenomena. The complex Hg II (S 2 COC 4 H 9 ) 2 has actually been isolated, and strong evidence for the existence of Hg II (S 2 COR) 3 − complexes has been obtained. Behaviour in other media is briefly reported.