Two aspects of molar mass determination via diffusion ordered spectroscopy (DOSY) are described in this work. Firstly, we investigated how far the temperature of measurement affects the outcome of the DOSY experiment. For this, we performed molar mass calibrations of diffusion coefficients obtained for a series of narrowly distributed polystyrene samples in the temperature range of 0 to 40 °C. While a linear calibration is obtained at each temperature, a profound dependence of the obtained diffusion coefficient on temperature is first identified. We then demonstrated that this effect is an artifact created from convection in an NMR tube during the experiment and is dependent on the pulse sequence program. Using the dstebpgp3s pulse sequence, the available molar mass range and the temperature window for calibration are extended, and a reasonable agreement of all data with the Stokes–Einstein equation is found. To verify the validity of the chosen pulse sequence, we further determined the radii of gyration for different polymers via small-angle neutron scattering (SANS) experiments. SANS confirms the expected change in the radius with the molar mass, and no significant temperature dependence of the coil size is seen, in agreement with the results obtained using the dstebpgp3s pulse sequence. Secondly, we discuss different modes of calibration that scientists can use to determine molar masses from their individually measured diffusion coefficients. In addition, we provide a freely available software tool that allows one to directly transform diffusion coefficients into molar masses by applying a variety of calibrations and by guiding researchers as to which calibration is most suitable for their specific case.

中文翻译：

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实现 DOSY 作为摩尔质量表征工具的普遍使用：温度依赖性研究和处理扩散系数的软件工具

这项工作描述了通过扩散有序光谱 (DOSY)测定摩尔质量的两个方面。首先，我们研究了测量温度对 DOSY 实验结果的影响程度。为此，我们对一系列窄分布聚苯乙烯样品在 0 至 40 °C 温度范围内获得的扩散系数进行了摩尔质量校准。虽然在每个温度下都获得了线性校准，但首先确定了所获得的扩散系数对温度的深刻依赖性。然后我们证明，这种效应是实验过程中 NMR 管中的对流产生的伪影，并且取决于脉冲序列程序。使用 dstebpgp3s 脉冲序列，扩展了可用的摩尔质量范围和校准温度窗口，并且发现所有数据与斯托克斯-爱因斯坦方程合理一致。为了验证所选脉冲序列的有效性，我们通过小角中子散射（SANS）实验进一步确定了不同聚合物的回转半径。SANS 证实了半径随摩尔质量的预期变化，并且没有看到线圈尺寸的显着温度依赖性，这与使用 dstebpgp3s 脉冲序列获得的结果一致。其次，我们讨论了科学家可以用来根据单独测量的扩散系数确定摩尔质量的不同校准模式。此外，我们还提供了一款免费的软件工具，允许人们通过应用各种校准并指导研究人员选择最适合其具体情况的校准，将扩散系数直接转换为摩尔质量。