聚乙二醇中的羟基数
AN-T-178
2020-08
zh
Pyridine-free, fully automated determination according to ASTM E1899, EN 15168, and DIN 53240-3
羟基数是量化化学物质中羟基存在情况的重要总和参数。作为一项重要的质量参数，羟基数经常在树脂、涂料、聚酯醇、脂肪和溶剂等各种聚合物中进行测定。与其他标准不同，ASTM E1899 不含吡啶，无需在高温下长时间回流。它在室温下进行，只需少量样品，适用于极低的羟基数（<1 毫克 KOH/g 样品），并可全自动进行。本应用说明介绍了根据 ASTM E1899、EN 15168 和 DIN 53240-3 标准对 1-辛醇和聚乙二醇中的羟基数进行电位测定的方法。使用 OMNIS DIS-Cover 技术，所有样品制备步骤均可完全自动化。此外，使用 OMNIS 样品机器人还可同时分析多个样品。因此，每个样品的平均分析时间可从约 24 分钟缩短至 12 分钟，大大提高了实验室的生产效率。
The hydroxyl number (HN) is an important sum parameter for quantifying the presence of hydroxyl groups. As a key quality parameter, it is regularly determined in resins, paints, polyesterols, fats, and solvents. Unlike other standards, ASTM E1899 is free from pyridine and does not require refluxing samples at high temperatures for extended periods. It is performed at room temperature, requires only a small sample size, is applicable to extremely low HN, and can be performed fully automatically.
This Application Note describes the potentiometric determination of HN in 1-octanol and polyethylene glycol according to ASTM E1899, EN 15168, and DIN 53240-3. Using the OMNIS Dis-Cover technique, all sample preparation steps can be fully automated. Moreover, the use of an OMNIS Sample Robot allows parallel analysis of multiple samples, reducing the time per analysis for one sample from approximately 24 min to 12 min, and increasing productivity in the laboratory considerably.
This application is demonstrated on 1-octanol (theoretical HN of 430.08 mg KOH/g) and polyethylene glycol (PEG) 3000.
No sample preparation is required.
The determinations are performed on an automated system consisting of an OMNIS Sample Robot S equipped with Dis-cover, an OMNIS Professional Titrator equipped with two dSolvotrodes, and multiple OMNIS Dosing Modules for the addition of the auxiliary solutions.
An appropriate amount of sample is weighed into the titration beaker, acetonitrile is added, and the beaker is capped with the Dis-Cover lid. After dissolution of the sample, TSI solution is added, the beaker is covered and solution is stirred for the stipulated time. Then deionized water is added, and after stirring shortly, acetonitrile is added. The solution is titrated until after the second equivalence point with standardized tetrabutylammonium hydroxide in isopropanol.
Well-defined titration curves are obtained for the tested samples. The result for 1-octanol is well within the acceptable limit for the standard with a low standard deviation. For PEG 3000, which is analyzed on both work stations in parallel, acceptable results with low standard deviations are obtained. Results are summarized in Table 1. An example titration curve is displayed in Figure 2.
| Hydroxyl number (n = 6) | Mean in mg KOH/g sample | SD(rel) in % |
|---|---|---|
| 1-Octanol | 435.63 | 0.3 |
| PEG 3000 (WS 1) | 36.56 | 0.3 |
| PEG 3000 (WS 2) | 36.22 | 0.5 |
Precise and reliable determination of the hydroxyl number according to ASTM E1899, EN 15168, and DIN 53240-3 can be achieved using a fully automated OMNIS system. With the option to analyze up to four samples simultaneously, the productivity of a laboratory can be significantly improved. Furthermore, the OMNIS system can be customized according to your needs and expanded for other titration applications required for quality control.
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Internal reference: AW TI CH1-1274-042019