Determination of cations at the parts-per-billion level with non-suppressed ion chromatography and indirect photometric detection.
Determination of cations at the parts-per-billion level with non-suppressed ion chromatography and indirect photometric detection.
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使用非抑制离子色谱和间接光度检测以十亿分之一的水平测定阳离子。
DOI：
10.1016/s0021-9673(01)86862-x
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Sheu,C
中科院分区：
文献类型：
--
作者：
Chang,CA;Wu,QH;Sheu,C
钴 (III) 络合物流动相在 300-600 nm 区域有两个吸收带。 dd 过渡带最大值位于 498 nm，摩尔吸收率 E= 148 1 mall’cm-i。另一个以 324 nm 为中心的谱带 (E= 3940 1 mol-’cm-’) 对应于配位乙酰丙酮阴离子的 n-+ rc* 跃迁。在 300 nm 以下，还存在可能由于 rt+ rc* 和 n-+ n* 跃迁而产生的更强吸收包络。 Small 和 Miller* 表明，间接光度检测的信噪比 (S/N) 为： 其中 C 和 C 分别是样品和洗脱液的浓度，A 和 A 分别是样品和洗脱液的摩尔吸光系数，N 是常数，指的是随机噪声波动。对于透明离子，A,= 0，方程式： 1 变为： s cs-“N, c. N(2) 这意味着给定 C 和 N 作为常数，S/N 比将随着 C 的减小而增加。另一方面，如果 G/C 保持恒定，则 N 因子应随仪器、洗脱液和实验选择的波长而变化。在我们目前的研究中，选择 254 nm 时，S/N 比通常要好得多，因为 254 nm 处的摩尔吸光系数钴 (II1) 配合物的信噪比在 324 nm 和 498 nm 下要大得多。 同样，当使用带有氘灯的 Micromeritics 786 可变波长检测器替换带有 254 nm 钨灯的 Waters 固定波长检测器时，信噪比下降，图 1a 和 b 显示了 ppb 浓度水平的 Mg2+ 和 Ca*+ 离子的相同混合物与两种不同的 [Co] 的分离。 (en),(acac)].(NO,)* 洗脱液浓度；即，10e5 M 和 3.13。 尽管图 1b 的操作的洗脱液浓度降低至 3.13. 10m5 M，即图 1a 的 50%，但图 1b 数据的信噪比并未增加。 2. 相反，与图 1a 相比，它们实际上略有下降。这表明等式 1 和 2 中的 N 因子不仅取决于仪器和洗脱液等许多其他因素，而且还取决于我们实验室目前正在研究的一个主题。另一方面，根据这些信噪比值，本研究中 Mg*+ 和 Ca2+ 离子的检测限可能约为 10 ppb。对于特定应用，使用在不同波长下吸收的取代惰性络合物。在目前的情况下，如果样品溶液含有大量紫外吸收物质，则可以选择324 nm或498 nm的波长。
The cobalt (III) complex mobile phase has two absorption bands in the region 300-600 nm. A dd transition band maximum is at 498 nm with molar absorptivity, E= 148 1 mall’cm-i. Another band centered at 324 nm (E= 3940 1 mol-’cm-‘) corresponds to the n-+ rc* transition of coordinated acetylacetonate anion. Below 300 nm, an envelop of even stronger absorptions due to probably rt+ rc* and n-+ n* transitions is also present. Small and Miller* have shown that the signal-to-noise (S/N) ratio for indirect photometric detection is: where C, and C, are the respective concentrations of sample and eluent, A, and A, are the molar absorptivities of sample and eluent, respectively, and N, is a constant, referring to a random noise fluctuation. For a transparent ion, A,= 0, eqn. 1 becomes: s cs-“N, c. N(2)This means that giving C, and N, as constants, the S/N ratio will increase as C, decreases. On the other hand, if G/C, is kept constant, the N, factor should vary with the instrument, the eluent, and the wavelength chosen for the experiment. In our present study, the S/N ratio is in general much better when 254 nm is chosen because the molar absorptivity at 254 nm for the cobalt (II1) complex is much greater than those at 324 nm and 498 nm. Similarly, when a Micromeritics 786 variablewavelength detector with a deuterium lamp was used to replace the Waters fixedwavelength detector with a tungsten lamp at 254 nm, the S/N ratio drops. Fig. la and b show the separation of the same mixture of Mg2+ and Ca*+ ions at a ppb concentration level with two different [Co (en),(acac)].(NO,)* eluent concentrations; ie, 6.25. 10e5 M and 3.13. 10e5 M, respectively. Although the eluent concentration is reduced to 3.13. 10m5 M for the operation of Fig. lb; ie, 50% of that for Fig. la, the S/N ratios for Fig. lb data do not increase as predicted using eqn. 2. Instead, they actually decrease a little as compared to Fig. la. This indicates that the N, factor in eqns. 1 and 2 is dependent upon not only a number of other factors such as instrument and eluent but also the eluent concentration. This is a subject currently under study in our laboratory. On the other hand, with these S/N ratio values, the detection limits can be estimated to be about 10 ppb for both Mg*+ and Ca2+ ions for the present investigation. It is possible to use a substitution-inert complex that absorbs at different wavelengths for specific applications. In the present case, if the sample solution contains a lot of UV-absorbing species, the wavelength of 324 nm or 498 nm may be chosen
非抑制阴离子色谱中的取代惰性金属配合物流动相
DOI：
--
发表时间：
1984
期刊：
影响因子：
--
作者：
C. Chang;K. L. Fong
通讯作者：
K. L. Fong