The measure of the acid concentration in an organic media is a common issue in chemistry. With the aim to overcome this problem in a facile and inexpensive way, the spectroscopic properties of a PEGylate porphyrin derivative, the 5,10,15,20-p-(ω-methoxypolyethyleneoxyphenyl) porphyrin (P), as an acidity sensor were tested.

Its behaviour was analysed in toluene and several fuels through acid titration experiments. In each case, examining UV–vis and fluorescence spectroscopic data, the disappearance of the free-base porphyrin derivative Uv–vis signals (B- and Q-bands) and the increasing of new bands, as a consequence of the added acid, was monitored.

On the basis of these data it was possible to evaluate the presence of acid in several organic media as toluene, gasoline, diesel, and jet fuel, using our porphyrin derivative in very low amount (about 3 ppm).

Finally, in order to exclude the risk of a negative contribution of P in ash formation, the complete oxidation of the porphyrin compound under common engine's combustion conditions was also ascertained.

有机介质中酸浓度的测量是化学中的常见问题。为了以简便且廉价的方式解决此问题，测试了聚乙二醇化卟啉衍生物5,10,15,20-对-（ω-甲氧基聚乙氧基苯基）卟啉（P）作为酸度传感器的光谱性质。

通过酸滴定实验分析了其在甲苯和几种燃料中的行为。在每种情况下，检查紫外可见光谱和荧光光谱数据，由于添加了酸，游离碱卟啉衍生物Uv-vis信号（B和Q波段）消失了，新的波段增加了。被监视。

根据这些数据，可以使用极少量（约3 ppm）的卟啉衍生物评估甲苯，汽油，柴油和喷气燃料等几种有机介质中酸的存在。

最后，为了排除P对灰分形成负作用的风险，还确定了在普通发动机燃烧条件下卟啉化合物的完全氧化。