title: Chromatographic and spectroscopic identification and recognition of ammoniacal cochineal dyes and pigments.
abstract: In this work a combined chromatographic and spectroscopic approach is used to provide a diagnostic assessment of semi-synthetic ammoniacal cochineal through the syntheses of its dyes and lakes according to art historical recipes. Commercially introduced in the late XIX century as a dye and pigment, it was used to obtain a brilliant purplish/violet nuance which provided a more stable option over carminic acid although its evidenced use in manufacts and artworks of heritage importance have been scarcely documented. Through HPLC-DAD, it has been possible to identify 4-aminocarminic acid as the main component of ammoniacal cochineal highlighting a chemical formula analogous to acid stable carmine, a recent patented food dye. FTIR clearly distinguishes the amine group in the ammoniacal cochineal dye preparation and TLC-SERS allows for an adequate separation and spectral differentiation in its main components to be evidenced. Colloidal SERS has permitted spectral markers useful in discerning ammoniacal cochineal over carminic acid to be highlighted and discussed. Finally, the methods experimented in this study for the identification of ammoniacal cochineal have been validated on analyzing a sample of dyed wool.
authors.affiliation: Università degli Studi di Perugia c/o Dipartimento di Chimica, Biologia e Biotecnologie, Via Elce di Sotto 8, Perugia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Chieli
authors.affiliation: Institut Royal du Patrimoine Artistique (IRPA-KIK, Belgium), 1, Parc du Cinquantenaire, 1000 Brussels, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Sanyova
authors.affiliation: Istituto CNR di Scienze e Tecnologie Molecolari (CNR-ISTM), via Elce di Sotto 8, I-06123 Perugia, Italy; Centro di Eccellenza SMAArt (Scientific Methodologies applied to Archaeology and Art) c/o Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy. Electronic address: b.bd.doherty@talk21.com.
authors.forename: B
authors.initials: B
authors.lastname: Doherty
authors.affiliation: Università degli Studi di Perugia c/o Dipartimento di Chimica, Biologia e Biotecnologie, Via Elce di Sotto 8, Perugia, Italy; Istituto CNR di Scienze e Tecnologie Molecolari (CNR-ISTM), via Elce di Sotto 8, I-06123 Perugia, Italy; Centro di Eccellenza SMAArt (Scientific Methodologies applied to Archaeology and Art) c/o Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
authors.forename: B G
authors.initials: BG
authors.lastname: Brunetti
authors.affiliation: Istituto CNR di Scienze e Tecnologie Molecolari (CNR-ISTM), via Elce di Sotto 8, I-06123 Perugia, Italy; Centro di Eccellenza SMAArt (Scientific Methodologies applied to Archaeology and Art) c/o Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Miliani
keywords: 4-Aminocarminic acid; Ammoniacal cochineal; Carminic acid; Semi-synthetic dye