Ming-Yan LUO,Bei LÜ,Guo-Bin SHEN,Fei-Fang ZHANG,Bing-Cheng YANG
Electrodialytic eluent generator, one of the key components of ion chromatography system, was fabricated and evaluated. The data achieved indicated that its performance could be comparable to that of commercial one. The maximal operation pressure was over 20 MPa, the generated KOH concentration was up to 100 mM, and the designed usage lifetime was about 354 day (take 8 h working time per day). This device will be helpful to the improvement of domestic instruments of ion chromatography.
An anion-exchange chromatography method combined solid phase extraction (SPE) was developed for the simultaneous analysis of glycolate acid (GL), monochloroacetic acid (MCA) and dichloroacetic acid (DCA) in synthetical betaine products. The analytes and unknown anionic impurities were well separated on a Metrosep A supp5 anion-exchange column (150 mm×4 mm) with 2.0 mmol/L Na 2 CO 3 +2.0 mmol/L NaHCO 3 solution as eluent. Suppressed conductivity detection was used. A strong cation exchange (SCX) solid phase extraction (SPE) cartridge was used to reduce the concentration of matrix betaine and a Cleanert IC-Ag pretreatment cartridge was used to remove high Cl − concentration. The detection limits of GL, MCA and DCA were 0.09, 0.017 and 0.05 µg/L, respectively. The relative standard deviations (RSDs) of the retention times and peak areas were less than 0.09% and 0.49%, respectively. The recoveries of the three analytes were between 90.6% and 100.8%. The analytical results showed that GL and DCA were present in high concentration and no MCA was found when the proposed ion chromatography method was applied to three synthetical betaine samples. The proposed method is simple, sensitive and timesaving, and is also suitable for routine analysis in quality control of synthetical betaine products.
A new stationary phase for iodide ion analysis has been developed. The cationic polymer-epichlorohydrin-dimethylamine (PEPI-DMA) was served as modifier in synthesizing polyelectrolyte sorbents and the macroporous polystyrene-divinylbenzene (PS-DVB) resin was used as support. The positively charged polymer (PEPI-DMA) was electrostatically bonded to a negatively charged particle (PS-DVB sulfonated). The new stationary phase was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), elemental analysis, chemical adsorption and desorption measurements. The chromatographic evaluation of the new stationary phase was performed using various anions with a conductivity detector. The new stationary phase was also applied to the determination of iodide directly with a DC amperometric detector using a platinum working electrode and an Ag/AgCl reference electrode. The chromatographic conditions were optimized and the eluent solution contained 5 mmol/L HNO 3 and 15 mmol/L NaNO 3 at a flow rate of 1.0 mL/min and column temperature of 30 °C. The applied voltage of the DC amperometric detector was 0.9 V. Under the optimum conditions, the linear range of the method was 0.2–50 mg/L for iodide ion with a correlation coefficient of 0.9990. The detection limit was 0.05 mg/L (calculated at S/N = 3) and the relative standard deviations (RSD, n = 6) were all less than 1% for retention time, peak area and peak height. This method was also utilized for the determination of iodide ions in samples of povidone iodine solution and kelp samples with satisfactory results.
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