Hao F, Lwin T, Bruckard W J, Woodcock J T
CSIRO Minerals, Clayton South, Vic 3169, Australia.
J Chromatogr A. 2004 Nov 5;1055(1-2):77-85. doi: 10.1016/j.chroma.2004.08.130.
The method described here fulfils the need for a suitable analytical method to determine the concentrations of single and mixed aliphatic amines in the range from hexylamine (C6) to octadecylamine (C18) in flotation test solutions and in commercial flotation collectors. Amines do not have a UV-vis spectrum in aqueous solution but by reacting an amine-containing solution with 4-chloro-7-nitrobenzofurazan solution (chloro-NBD), derivatized products (amino-NBDs) are formed which have absorbance maxima at 470nm. Excess chloro-NBD and the amino-NBDs can be separated from each other by high-performance liquid chromatography (HPLC) and their concentrations measured with a UV-vis detector. Important variables in the derivatization stage are pH, temperature, chloro-NBD concentration, and reaction time, all of which interact with each other. A three-stage statistical procedure was used to determine the optimum conditions. In each stage, an 8-test design was used in which a high and low limit was set for each variable, and the chromatogram peak area of the derived amino-NBD was measured. The optimum derivatization conditions established were pH 8.9, chloro-NBD concentration 0.20% (w/v), temperature 70 degrees C, and reaction time 60 min. Optimum elution conditions for chromatography were an eluent containing 80% (v/v) acetonitrile in aqueous solution containing 40mM acetic acid at pH 4.5. With a flow rate of 2.0 ml/min, dodecylamine had a retention time of about 3 min, whereas octadecylamine had a retention time of 44 min. Straight-line calibration curves were obtained up to at least 200 ppm of amine in solution. The lower limit of detection was estimated to be 0.05 microM (10ppb) with a signal to noise ratio of 3. No interfering substances were found. The method was successfully applied to the analysis of solutions from an actual flotation test and to a solid commercial amine.
本文所述方法满足了对合适分析方法的需求，该方法用于测定浮选测试溶液和商业浮选捕收剂中从己胺（C6）到十八烷基胺（C18）范围内的单一和混合脂肪族胺的浓度。胺类在水溶液中没有紫外可见光谱，但通过使含胺溶液与4-氯-7-硝基苯并呋喃溶液（氯-NBD）反应，会形成衍生化产物（氨基-NBDs），其在470nm处有最大吸收。过量的氯-NBD和氨基-NBDs可通过高效液相色谱（HPLC）彼此分离，并用紫外可见检测器测量它们的浓度。衍生化阶段的重要变量是pH、温度、氯-NBD浓度和反应时间，所有这些变量相互影响。采用三阶段统计程序来确定最佳条件。在每个阶段，使用8次试验设计，为每个变量设定高限和低限，并测量衍生化氨基-NBD的色谱峰面积。确定的最佳衍生化条件为pH 8.9、氯-NBD浓度0.20%（w/v）、温度70℃和反应时间60分钟。色谱的最佳洗脱条件是在pH 4.5的含40mM乙酸的水溶液中含有80%（v/v）乙腈的洗脱剂。流速为2.0 ml/min时，十二烷基胺的保留时间约为3分钟，而十八烷基胺的保留时间为44分钟。在溶液中胺浓度至少达到200 ppm时获得了直线校准曲线。估计检测下限为0.05 microM（10 ppb），信噪比为3。未发现干扰物质。该方法成功应用于实际浮选测试溶液和固体商业胺的分析。
