Egg-Citing! Isolation of Protoporphyrin IX from Brown Eggshells and Its Detection by Optical Spectroscopy and Chemiluminescence

Abstract

We describe five laboratory modules, A through E, that can be completed in one 3-h laboratory period. Module A extracts the eggshell pigment from brown eggshells, module B identifies the pigment, using UVÀvis spectroscopy, as protoporphyrin IX by comparison of the spectrum with published data and quantifies it. Module C records the fluorescence spectrum of ABSTRACT: A simple and cost-effective laboratory experiment is described that extracts protoporphyrin IX from brown eggshells. The porphyrin is characterized by UVÀvis and fluorescence spectroscopy. A chemiluminescence reaction (peroxyoxalate ester fragmentation) is performed that emits light in the UV region. When the porphyrin extract is added as a fluor to this chemiluminescence reaction, an eye-catching deep red glow is emitted from the solution. Using a familiar object, an egg, the experiment touches upon many aspects in chemistry (natural products isolation, structure and photophysical properties of porphyrins, photochemistry). Focus is placed on the understanding of the optical properties of protoporphyrin that enable the final chemiluminescence experiment. This project is appropriate for upperlevel organic chemistry students, but might also serve in the advanced physical chemistry laboratory to facilitate a more detailed discussion of photophysical phenomena. Finally, the chemiluminescence experiment is suitable as an impressive stand-alone demonstration.

Pigmentation of White, Brown, and Green Chicken Eggshells Analyzed by Reflectance, Transmittance, and Fluorescence Spectroscopy

“…This property is common knowledge by visual inspection. The distribution was quantitavely examined by partial dissolution of PPIX localized close to the outer shell surface . The transmittance spectra absorb with equal strength upon irradiation from both surface sides, see Figure (c), and (d).…”

“…The distribution was quantitavely examined by partial dissolution of PPIX localized close to the outer shell surface. [25,28] The transmittance spectra absorb with equal strength upon irradiation from both surface sides, see Figure 4 (c), and (d). It should be noted that Tspectra do not render the gradient but still the absolute extent of non-uniformity so that they help to understand the pigment distribution over the layer depth.…”

“…More specifically, the shell is soaked in a neutral or slightly alkaline solution of ethylenediaminetetraacetate (EDTA) which dissolves the cuticle and pigments therein but only slightly affects the calcareous region . An alternative is surface etching with diluted hydrochloric acid to extract pigment from eggshell . These methods allow one to differentiate between pigment positions close to the outer surface and the interior of the shell .…”

“…[24] An alternative is surface etching with diluted hydrochloric acid to extract pigment from eggshell. [25] These methods allow one to differentiate between pigment positions close to the outer surface and the interior of the shell. [26,27] Samiullah and Roberts found more PPIX in the calcareous part than in the cuticle.…”

The Red Color of Life Transformed – Synthetic Advances and Emerging Applications of Protoporphyrin IX in Chemical Biology

“…A key compound is protoporphyrin IX (PPIX), which, as the biosynthetic precursor of hemes as well as the chlorophylls of photosynthesis, remains one of the most intensely studied natural tetrapyrrolic compounds. In daily life, next to blood, it is often found on the breakfast table as the shell pigment in brown eggs …”