title: Redox tuning and species distribution in Maya Blue-type materials: a reassessment.
abstract: Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography-mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemistry data permits the estimatation of indigo loading in archeological Maya Blue, which is in the range of 0.2 to 1.5 wt %. These results support a view of 'genuine' Maya Blue-type materials as complex polyfunctional organic-inorganic hybrids.
authors.affiliation: Departament de Química Analítica, Universitat de València, Dr. Moliner, 50, 46100 Burjassot València, Spain. antonio.domenech@uv.es
authors.forename: Antonio
authors.initials: A
authors.lastname: Doménech-Carbó
authors.forename: Francisco Manuel
authors.initials: FM
authors.lastname: Valle-Algarra
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Doménech-Carbó
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Domine
authors.forename: Laura
authors.initials: L
authors.lastname: Osete-Cortina
authors.forename: José Vicente
authors.initials: JV
authors.lastname: Gimeno-Adelantado
mesh_terms: D001546:Bentonite / Q000737:chemistry / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004563:Electrochemistry; D006801:Humans; D007203:Indigo Carmine / Q000737:chemistry* / Q000302:isolation & purification; D007510:Isatin / Q000737:chemistry* / Q000302:isolation & purification; D007616:Kaolin / Q000737:chemistry / Q000302:isolation & purification; D017616:Magnesium Compounds / Q000737:chemistry* / Q000302:isolation & purification; D017633:Magnesium Silicates / Q000737:chemistry* / Q000302:isolation & purification; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D017655:Silicon Compounds / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D017616:Magnesium Compounds; D017633:Magnesium Silicates; D017655:Silicon Compounds; D001546:Bentonite; D007616:Kaolin; D007510:Isatin; C001671:magnesium trisilicate; D007203:Indigo Carmine; C026325:attapulgite