以化學方法探討不同黑色鋼筆墨水

Abstract

鋼筆墨水的成份為染料、顏料與奈米顆粒這類的有色物質以及作為載體的水及乙二醇或有機溶劑，除此之外還含有表面活性劑及其他添加物，存在於墨水中的酸性染料多為離子型態。市面上販賣的鋼筆墨水有多種顏色，其中有許多人眼無法辨識出差別的同色系墨水。本篇研究使用了紫外光/可見光分光光譜法、基質輔助雷射脫附游離串聯質譜法、液相層析串聯光二極體陣列偵測器與液相層析串聯質譜法並計算各方法區分10款黑色鋼筆墨水的辨別能力，其中五款為染料墨水、另外五款為含有奈米顆粒的顏料墨水，儘管顏色相似但透過紫外光/可見光分光光譜圖可發現10個樣品間確實有差異存在，確認彼此之間存在有不同的成份。利用粒徑分析儀獲得墨水中奈米顆粒的粒徑大小，並使用基質輔助雷射脫附游離-飛行時間式質譜圖中顯示之特徵峰將墨水彼此區分。接著以離子對液相層析法分離樣品中含有的染料離子，串聯光二極體陣列偵測器與質譜儀加以分析。結果顯示特徵峰位在240 nm紫外光吸收光譜圖的墨水皆含有奈米顆粒，顏色與染料墨水相比較黑，而吸收特徵峰位於575 nm的墨水於正電模式質譜圖中也有m/z 695.088訊號峰出現。根據紫外光/可見光分光光譜法、基質輔助雷射脫附游離串聯質譜法、液相層析串聯光二極體陣列偵測器與液相層析串聯四極桿/飛行時間式質譜法的結果顯示分辨率介在0.71~1.00之間，且最有效率的方法為基質輔助雷射脫附游離串聯質譜法正電模式。而透過上述方法，即使是顏色十分近似的墨水也能加以辨識，為鋼筆墨水鑑識研究提供了能有效分析的方法。Fountain pen inks contain dyes, pigments or nanoparticles as colorants; water and ethylene glycol or organic solvent as vehicles. The dyes in fountain pen inks were usually acid dyes which are ionic compounds. There are many colors of fountain pen inks on the market, including some inks of analogous color that cannot be distinguished by human eyes. In this study, fountain pen inks of black colors (5 dye-based and 5nanoparticle-based) have been investigated by UV-Vis absorption spectroscopy, LC-DAD, MALDI-TOF MS, and LC-Q/TOF MS analysis. UV/Visible spectroscopy of fountain pen inks showed different profiles despite their similar colors. Particle size analysis were effectively applied to check the existence of nanoparticles in the samples. Ten kinds of black fountain pen inks were differentiated successfully by the profiles of their MALDI-TOF spectra. The dye-based fountain pen inks were further analyzed and compared by ion pair liquid chromatography, in which the dyes were separated effectively using diode array and mass spectrometer as detectors. The results showed that fountain pen inks which shown absorption at 575 nm also exhibiting m/z 695.088 in positive mode mass spectra. Nanoparticle-based inks are darker than dye-based inks, they show the same absorption at 240 nm. On the basis of combined results of all analytical methods mentioned above, the values of discriminating power were 0.71-1.00. The best method is positive mode of MALDI-TOF since it can distinguish fountain pen inks of similar colors, that provides an effective analytical approach for differentiation and identification of fountain pen inks.