13C qNMR结合DFSS方法测定油品芳碳率

利用六西格玛设计(design for six Sigma,DFSS)方法,通过定量核磁共振碳谱(quantitative carbon nuclear magnetic resonance spectroscopy,~(13)C qNMR)对由11种已知烃类化合物组成的模型油品进行了芳香碳摩尔百分比C(ar)%,简称芳碳率]测定的系统研究,建立了C(ar)%与样品浓度Conc.、弛豫试剂浓度Cr(acac)_3]和循环延迟D13个参数之间的数学模型,据此模型得到了优化的参数设置:Conc.为180mg/mL,Cr(acac)_3]为12 mg/mL,D1为10.5 s.按此设置进行了8组验证实验,其结果重现性较好,相对标准偏差(relative standard deviation,RSD)为0.61%;准确性较高,达到99.0%~100.6%.该方法也可用于其它分析测试方法的系统研究,且实验结果对现行油品芳碳率测定标准中相关参数,如Cr(acac)_3]和D1的设置能够提出补充性建议.

Determination of Aromatic Carbon Mole Ratio in Oil Samples by Quantitative 13C NMR Spectroscopy with DFSS Methodology

Aromatic carbon mole ratios C(ar)%] in model oil samples, which consisted of 11 saturated/unsaturated compounds with known contents, were determined by quantitative carbon nuclear magnetic resonance spectroscopy (13C qNMR) with the design for six Sigma (DFSS) methodology. An empirical model was established between C(ar)% and sample parameters, including sample concentration (Conc.), concentration of relaxation reagent Cr(acac)3 and relaxation delay (D1). Based on the model, the optimal condition was determined to be at sample concentration 180 mg/mL, concentration of Cr(acac)312 mg/mL and D110.5 s. Eight verification experiments were performed under the optimal condition, and the results showed fairly good repeatability (RSD = 0.61%) and accuracy (99.0%~100.6%). The work also gave some supplementary suggestions on parameter settings for the current GB method/ASTM method.