钌催化前驱体是影响负载型钌催化剂催化性能最重要因素。 前驱体中的部分杂质会对催化性能产生抑制作用, 尤其是S, P, Cl, As等杂质元素含量过高会降低催化剂的活性, 严重时会造成催化剂中毒; 因此, 必须严格控制催化前驱体中杂质元素的含量。 建立了快速准确测定催化前驱体亚硝酰硝酸钌(Ru(NO)(NO3)3)中杂质元素的分析方法。 Ru(NO)(NO3)3经稀硝酸溶解后采用电感耦合等离子体串联质谱(ICP-MS/MS)直接测定其中的8个杂质元素(P, S, Ti, V, Cr, Mn, Fe, As)。 为防止Ru(NO)(NO3)3溶液水解形成Ru(NO)(NO3)x(OH)3-x, 采用稀硝酸介质有效维持了样品溶液的稳定性。 在MS/MS模式下, 通过一级四极杆质量过滤器(Q1)控制进入碰撞/反应池(CRC)的离子, 仅允许与待测元素具有相同质荷比(m/z)的离子进入CRC, 从而将来自样品基质和等离子气Ar所形成的干扰离子阻止在CRC外, 消除了大量质谱干扰。 通过向CRC内通入O2为反应气, 目标离子P+, S+, Ti+, V+, As+与O2的反应为放热过程(31P++O2→31P16O++O, ΔHr=-3.17 eV; 32S++O2→32S16O++O, ΔHr=-0.34 eV; 48Ti++O2→48Ti16O++O, ΔHr=-1.63 eV; 51V++O2→51V16O++O, ΔHr=-0.85 eV; 75As++O2→75As16O++O, ΔHr=-0.63 eV), 能自发反应生成氧化物离子; 目标离子Cr+, Mn+与O2的反应为吸热过程(52Cr++ O2→52Cr16O++O, ΔHr=+1.38 eV; 55Mn++O2→55Mn16O++O, ΔHr=+2.15 eV)。 为促进Cr+, Mn+与O2发生反应, 通过调整CRC的工作参数, 设置八极杆偏置电压为较大的负电压, 使Cr+和Mn+在与O2反应前被加速, 提高Cr+和Mn+的动能, 促进了反应的发生, 通过吸热反应生成氧化物离子; 而P+, S+, Ti+, V+, Cr+, Mn+, As+干扰离子在CRC内不能与O2发生反应, 仍然保持原始的m/z。 通过二级四极杆质量过滤器(Q2)将这些干扰离子阻止在外, 仅允许所形成的氧化物离子进入检测器, 几乎完全消除了元素P, S, Ti, V, Cr, Mn, As的所有质谱干扰。 NH3因含一对孤对电子而具有高反应活性, 能与很多金属离子反应形成团簇离子。 通过向CRC内通入NH3/He为反应气, 目标离子Fe+与NH3发生质量转移反应, 在所形成多个团簇离子中, Fe(NH3)+2的丰度最高且无干扰, 通过NH3质量转移法消除干扰。 结果显示, 8个元素在0～500 μg·L-1范围内具有良好的线性关系, 线性相关系数≥0.999 8。 方法的检出限为0.29～485 ng·L-1, 按所建立的方法分析了实际样品中8个杂质元素的含量, 各元素的加标回收率为93.2%～107.5%, 相对标准偏差(RSD)≤3.9%。 方法具有样品处理简单、 分析速度快和精密度高的特点, 适合催化前驱体亚硝酰硝酸钌中多个杂质元素的准确测定, 为制备负载型钌催化剂提供了质量保障。

Ruthenium catalyzed precursor is the most principal factor affecting the catalytic performance of the supported ruthenium catalyst. Some impurities in the ruthenium catalyzed precursor can inhibit the catalytic performance. In particular, the high content of impurities (such as S, P, Cl and As) reduces activity of the catalyst. In severe cases, the catalyst can be poisoned, thus the level of impurities in the catalytic precursor must be controlled. In this paper, we report an analytical method for rapid and accurate determination of impurity elements in ruthenium nitrosyl nitrate (Ru(NO)(NO3)3) precursor. After dissolved by nitric acid, the impurities (such as P, S, Ti, V, Cr, Mn, Fe and As) were directly determined by inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS). In order to prevent the hydrolysis of Ru(NO)(NO3)3 into Ru(NO)(NO3)x(OH)3-x, we used diluted nitric acid to dissolve the samples while retaining their stability. In the MS/MS mode, the first quadrupole mass filter (Q1) controlled the collision/reaction cell (CRC) ions, only allowing analytes with the same mass charge ratio (m/z) into the CRC. It prevented the interfering ions from the sample matrix and plasma Ar from traveling outside of the CRC, eliminating a significant mass spectral interference. The reaction of target ions P+, S+, Ti+, V+ and As+ with O2 (added into the CRC as a reaction gas) was an exothermic process, which could spontaneously produce corresponding oxides (31P++O2→31P16O++O, ΔHr=-3.17 eV; 32S++O2→32S16O++O, ΔHr=-0.34 eV; 48Ti++O2→48Ti16O++O, ΔHr=-1.63 eV; 51V++O2→51V16O++O, ΔHr=-0.85 eV; 75As++O2→75As16O++O, ΔHr=-0.63 eV). The reaction of Cr+ and Mn+ target ions with O2 was an endothermic process (52Cr++O2→52Cr16O++O, ΔHr=+1.38 eV; 55Mn++O2→55Mn16O++O, ΔHr=+2.15 eV). In order to promote this endothermic reaction, we adjusted parameters of the CRC, in particular, by setting the octopole bias voltage to a negative voltage. Under these conditions, kinetic energy of Cr+ and Mn+ increased and the ions accelerated before the reaction with O2. However, the P+, S+, Ti+, V+, Cr+, Mn+ and As+ ions did not react with O2 in CRC, but still maintained the original m/z. The second quadrupole mass filters (Q2) could block out these interfering ions allowing the oxide-forming ions to enter the detector. This technique eliminated almost all interference from P, S, Ti, V, Cr, Mn and As. NH3 has high reactivity and a pair of lone pairs of electrons, therefore it reacts with many metal ions forming cluster ions. By adding NH3/He as a reactant gas into the CRC, the mass shift reaction of the target Fe+ ions with NH3 occurred. Among the multiple cluster ions, content of Fe(NH3)+2 was the highest and no interference was observed. Thus, we eliminated the interference by the NH3 mass shift method. All 8 elements had a good linear relationship in the range of 0～500 μg·L-1 with the correlation coefficient R2≥0.999 8. The instrumental limit of detection (LOD) of analyte ranged from 0.29 to 485 ng·L-1. According to the established method, the contents of impurity elements in the samples were analyzed. The spiked recovery of the analyte ranged from 93.2% to 107.5%, and the relative standard deviations (RSDs) were less than 3.9%. The proposed method has the advantages of simple sample processing, high speed of analysis and high precision, and is suitable for accurate determination of impurities in Ru(NO)(NO3)3, thereby providing a quality guarantee for preparing the supported ruthenium catalysts.