The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast, Preliminary Authentication of Gemstones.

The identification of gemstones is an important topic in the field of cultural heritage, given their enormous value. Particularly, the most important precious stones, namely diamond, emerald, ruby and sapphire, are frequently subjected to counterfeit by substitution with objects of lesser value with similar appearance, colour or shape. While a gemmologist is able to recognise a counterfeit in most instances, more generally, it is not easy to do this without resorting to instrumental methods. In this work, the use of UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) is proposed as a fast and easy method for the preliminary identification of gemstones, alternative to the classical methods used by gemmologists or to Raman spectroscopy, which is by far the instrumental method with the best diagnostic potential, but it cannot be used in situations of problematic geometric hindrance. The possibilities and the limitations given by the FORS technique are critically discussed together with the spectral features of the most important gemstones. Finally, the application of chemometric pattern recognition methods is described for the treatment of large sets of spectral data deriving from gemstones identification.

On the Traceability of the Hazelnut Production Chain by Means of Trace Elements.

The production chain of hazelnuts has been studied by analyzing three sets of samples produced in purity from three different pools of hazelnuts of cultivar "Tonda Gentile Trilobata", "Tonda Gentile Romana" and "Mortarella", all cultivated in Italy. From each pool, five processed products were obtained: roasted hazelnuts, hazelnut paste, hazelnut cream, Gianduja paste and Gianduiotto paste. After pre-treatment by means of dry ashing, all samples from each cultivar, including raw hazelnuts, were then analyzed by means of Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). A good discrimination was obtained among the different chain stages according to the distribution of the trace elements, as expected. More interesting was the discrimination among the different cultivars: it was possible to distinguish the samples produced from the respective cultivar by means of specific chemical markers, particularly Mo and Ni.

It's Only a Part of the Story: Analytical Investigation of the Inks and Dyes Used in the Privilegium Maius.

The Privilegium maius is one of the most famous and spectacular forgeries in medieval Europe. It is a set of charters made in the 14th century upon commitment by Duke Rudolf IV, a member of the Habsburg family, to elevate the rank and the prestige of his family. These five charters, now kept at the Österreichisches Staatsarchiv in Vienna, have been subjected to a thorough interdisciplinary study in order to shed light on its controversial story. The charters are composed of pergamenaceous documents bound to wax seals with coloured textile threads. The present contribution concerns the characterisation of the inks used for writing and of the dyes used to colour to the threads: Are they compatible with the presumed age of the charters? Though showing only a part of the whole story of the charters, dyes analysis could contribute in assessing their complex history from manufacturing to nowadays. The dyes were characterised with non-invasive in situ measurements by means of fibre optic (FORS) and with micro-invasive measurements by means of Surface Enhanced Raman Spectroscopy (SERS) and High-Performance Liquid Chromatography with Mass Spectrometry (HPLC-MS) analysis. The results showed that the threads of four of the charters (three dyed with madder, one with orchil) were apparently coloured at different dyeing stages, then re-dyed in the 19-20th century.

Tracking the Mandorla di Avola Almond Variety by Means of ICP Analysis.

The Mandorla di Avola is recognized all over the world as one of the best almond varieties. It is cultivated in a small area inside the provinces of Siracusa and Ragusa (Sicily, southern Italy). It is used in traditional Sicilian cuisine for both salty and sweet foods and of course in artisan pastry, apart from being consumed as a fruit. Due to its extraordinary organoleptic and beneficial features, the Mandorla di Avola is frequently counterfeit with almond varieties of lower quality coming from other countries. While its nutraceutical features have been studied, the possibility of authenticating it with respect to other varieties has not been explored. In this work, we used microelements determined with ICP-OES and ICP-MS as chemical descriptors to distinguish samples of Mandorla di Avola almonds from almonds coming from California and Spain, which are usually employed as substitutes in pastry. Among the different elements determined, Mn and P were found to be the best descriptors for authentication.

On the Traceability of Honey by Means of Lanthanide Distribution.

Honey is a natural food appreciated all over the world since antiquity due to its well-recognised beneficial properties. However, it is also considered among the most counterfeited foods. Therefore, analytical methods are currently being developed to allow the verifying of its geographic provenance and its botanical origin. Trace- and ultra-trace elements are usually exploited as chemical descriptors in authentication studies, as they allow the properties declared in the label to be verified. A different matter is to trace a food by means of traceability, that is, to find the link between a food and the soil in which this food originates. For traceability, it has been demonstrated in several studies that the lanthanides are particularly useful to find this link. In the present study, the traceability of the honey chain has been studied by means of ICP-MS and ICP-OES analysis, by comparing the lanthanide distributions of 17 different monofloral honey chains, each one composed of honey, flowers and soil in which such flowers grew. The results show that, while the fingerprint of soil, described by the lanthanide distribution, is transmitted unaltered from soil to flowers, a slight fractionation on the heavier lanthanides (from Dy to Lu) occurs in the passage from flowers to honey.

Identification of Illicit Conservation Treatments in Fresh Fish by Micro-Raman Spectroscopy and Chemometric Methods.

In the field of food control for fresh products, the identification of foods subjected to illicit conservation treatments to extend their shelf life is fundamental. Fresh fish products are particularly subjected to this type of fraud due to their high commercial value and the fact that they often have to be transported over a long distance, keeping their organoleptic characteristics unaltered. Treatments of this type involve, e.g., the bleaching of the meat and/or the momentary abatement of the microbial load, while the degradation process continues. It is therefore important to find rapid methods that allow the identification of illicit treatments. The study presented here was performed on 24 sea bass samples divided into four groups: 12 controls (stored on ice in the fridge for 3 or 24 h), and 12 treated with a Cafodos-like solution for 3 or 24 h. Muscle and skin samples were then characterized using micro-Raman spectroscopy. The data were pre-processed by smoothing and taking the first derivative and then PLS-DA models were built to identify short- and long- term effects on the fish's muscle and skin. All the models provided the perfect classification of the samples both in fitting and cross-validation and an analysis of the bands responsible for the effects was also reported. To the best of the authors' knowledge, this is the first time Raman spectroscopy has been applied for the identification of a Cafodos-like illicit treatment, focusing on both fish muscle and skin evaluation. The procedure could pave the way for a future application directly on the market through the use of a portable device.

Two-Dimensional Gel Electrophoresis Image Analysis.

Gel-based proteomics is still quite widespread due to its high-resolution power; the experimental approach is based on differential analysis, where groups of samples (e.g., control vs diseased) are compared to identify panels of potential biomarkers. However, the reliability of the result of the differential analysis is deeply influenced by 2D-PAGE maps image analysis procedures. The analysis of 2D-PAGE images consists of several steps, such as image preprocessing, spot detection and quantitation, image warping and alignment, spot matching. Several approaches are present in literature, and classical or last-generation commercial software packages exploit different algorithms for each step of the analysis. Here, the most widespread approaches and a comparison of the different strategies are presented.

Chemometric Tools for 2D-PAGE Data Analysis.

Two-Dimensional Polyacrylamide Gel Electrophoresis (2D-PAGE) provides two-dimensional maps where proteins appear separated according to their isoelectric point (pI) and molecular weight (MW). Usually these maps are very complex (i.e., hundreds or thousands of spots can be present in each map), and characterized by a low reproducibility, which hinders the possibility to identify reliable biomarkers unless robust methods are applied. The analysis of different sets of 2D-PAGE maps (e.g., control vs. pathological or control vs. drug-treated samples) to identify candidate biomarkers (proteins under- or over-expressed in different conditions) is usually carried out through image analysis systems providing a so-called spot volume dataset where each sample corresponds to a map described by the optical densities of all the detected spots. The identification of candidate biomarkers can be therefore accomplished by comparing different maps by classical monovariate statistical tests applied spotwise, or by multivariate chemometric tools applied to the entire set of spots present on each map. Here, the most exploited multivariate techniques will be considered, ranging from pattern recognition to classification methods.

A preliminary study on the authentication and traceability of extra virgin olive oil made from Taggiasca olives by means of trace and ultra-trace elements distribution.

Extra virgin olive oil (EVO) is among the most counterfeit foodstuffs in the present market. The Italian production is with no doubt one of the most valuable and therefore mostly counterfeit, due to the difficulty in checking the geographic provenance of olives. In order to provide a way for verifying the provenance of EVO, the role of microelements and, in particular, of lanthanides in the oil production chain has been studied. The distribution of lanthanides as determined by means of ICP-MS analysis appeared to provide a good tool for tracing the EVO production chain. Lanthanides and other microelements were then used for distinguishing a particularly prised EVO production from Liguria (northwestern Italy) made from Taggiasca olive variety, verifying that this production can be easily authenticated on the base of these chemical descriptors.

Mythic dyes or mythic colour? New insight into the use of purple dyes on codices.

The traditional knowledge concerning the use of Tyrian purple in Late Antique and Medieval purple codices - those precious biblical texts written with noble metal inks on parchment dyed or painted with purple colourants - is here updated in view of new analytical evidence. Recent literature reports the analysis carried out on some purple codices, suggesting that Tyrian purple has not, if ever, been used in their making. A large number of purple codices has been considered in this work to elucidate the nature of the purple colour. Results have been discussed within the frame of previous information, thus covering a vast majority of the purple codices presently identified. In most of the instances the use of less expensive dyes such as folium or orchil is suggested. Moreover, analytical results from a non-invasive spectroscopic approach have been definitely confirmed by micro-invasive surface-enhanced Raman analysis performed on micro samples of purple parchment taken from two 6th century codices.

Analytical evidences of the use of iron-gall ink as a pigment on miniature paintings.

Iron-gall ink (IGI) has been used by scribes for writing since at least the 4th century CE. Another typical use of this ink was for drawing: many Old Masters created beautiful sketches in brown-black hues. Despite its widespread use to draw lines, it seems like IGI was hardly used for painting as well. In fact, the number of identification on manuscripts is very low at present. This could be partially due to a lack of reliable diagnostic information. In this work we tried to better define the possibility of identifying IGI as a pigment on illuminate manuscripts, evaluating the pros and cons of three different techniques: UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS), Raman spectroscopy and XRF spectrometry. With concern to in situ non-invasive analysis, Raman spectroscopy has the best diagnostic power but FORS seems to provide the better compromise between selectivity and ease of application. Moreover, new analytical evidences was given on the particular use of IGI by ancient illuminators: a non-invasive and micro-invasive diagnostic survey on Western manuscripts datable in the range 6-16th centuries was carried out showing that, apart from its widespread use as an ink for writing and drawing, IGI was largely used as a pigment too. The large number of identification obtained allows us to hypothesise that this pigment was used all through medieval Europe up to at least the Renaissance, where its use is already documented in drawing. The occurrence of IGI in miniature paintings older than 6th century or more recent than 16th century cannot be excluded, as is its use beyond Europe; further measurements could instead widen the time range and the geographic area. Nevertheless, the present study allows shedding a new light on the use of this colourant all along the period of medieval and Renaissance miniature painting art.

Role of Lanthanides in the Traceability of the Milk Production Chain.

The traceability and authentication of milk were studied using trace and ultratrace elements as chemical markers. Among these variables, the group of lanthanides resulted in being particularly useful for this purpose as a result of their homogeneous distribution inside milk, which showed on the contrary to be intrinsically inhomogeneous from the elemental point of view. Using in this pilot study milk samples from a factory in Piedmont (Italy), we demonstrated that the distribution of lanthanides can be used as a fingerprint to put into relation the soil of the pasture land on which cows graze and the bottled milk produced in the factory. In fact, the distribution is maintained nearly unaltered along the production chain of milk, apart from the passage into the stomachs of the cows. Using the same variables, it was possible to discriminate between milk produced in the factory and milk samples taken from the large-scale retail trade.

On the identification of folium and orchil on illuminated manuscripts.

The identification of the two purple dyes folium and orchil has rarely been reported in the analysis of painted artworks, especially when analysing illuminated manuscripts. This is not consistent with the fact that ancient literary sources suggested their use as substitutes for the more expensive Tyrian purple dye. By employing non-invasive spectroscopic techniques, the present work demonstrates that these dyes were actually widely used in the production of ancient manuscripts. By employing UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) and spectrofluorimetry, the abundant identification of both dyes on medieval manuscripts was performed by comparing the spectra recorded on ancient codices with those obtained on accurate replicas of dyed or painted parchment. Moreover, examples are also reported whereby the considered purple dyes were used in mixtures with other colourants. The overall information obtained here allowed us to define new boundaries for the time range in which orchil and folium dyes were used which is wider than previously thought, and to focus on their particular uses in the decoration of books.