Current Analytical Chemistry - Volume 6, Issue 1, 2010

The world is multivariate [1]. In order to be significant, data coming from diagnostic work on Environment and Cultural Heritage as well must be subjected to a multivariate analysis. Multivariate analysis and chemometrics [2] are integrated approaches necessary [3] to the knowledge of the cultural item history, its constructive techniques, degradation, dating and origin. The second biennial CMA4CH Meeting occurred on 1-4 June 2008 at Ventotene, a small island near Rome (Italy). Under the II world war, in 1941, some prisoners of the jail, located in the much closed S. Stefano Island, wrote the “Manifesto di Ventotene” postulating the European Union (thanks to Altiero Spinelli, Ernesto Rossi, Eugenio Colorni, Luigi Einaudi, Ursula Hirschmann, Ferruccio Parri, Sandro Pertini et al.). The aim of the conference is to favour the meeting between researchers, experts, connoisseurs and competents on chemometry with those working on Environment and Cultural Heritage, not forgotten a session dedicated to theoretical aspects. More than one hundred authors contributed to the Meeting with more than forty presentations. This special issue contain an accurate selection of papers based on the researches presented at the 2nd edition of the International Meeting CMA4CH with a balance in the three main topics. All papers pass a three, serial, refereeings; the first to check consistence and quality balance, the second to check chemical/physical aspects, the third to check multivariate and chemometry content [4]. Even if slow, this method ensures an increasing quality passing among the three steps. Where possible all papers were revised to in order to facilitate the understanding also by readers with no experience in the chemometrics field [5]. In the previous edition of the Meeting, 2006 [6], we defined the terms cultherimetry and cultherimetrics [7] as the area combining multivariate analysis with cultural heritage. The two main geographic areas where “culture“ born and growth are the mediterraneum and the continental China those, unfortunately, are also subject to an increasing environmental pollution due to antrhopic impacts. Papers in the follow treat large quantities of statistical methods applied to data collected in the spirit of the meeting. Mainly; Principal Components Analysis, Canonical Components Analysis, Hierarchical Cluster Analysis and K means clustering, potential functions, wavelengths selection, PLS, PLS-DA, PCoA are widely used with other multivariate techniques. In many of the papers treating Cultural Heritage the analyses are performed by “in situ” non invasive or microinvasive techniques in order to respect the value of the artefacts. As it regards papers treating Environment [8], traces content of toxic metal ions were determined in potable waters by Instrumental Neutron Activation Analysis (INAA). A Mass balance Model was applied to data coming from PM10 monitoring obtained by Thermal Optical Transmission (TOT) Ionic Chromatography (IC) and Inductive Plasma Coupling - Optical Emission Spectroscopy (IPC-OES). Aerosol samples coming from a Mediterranean and a Turkey monitoring stations were analysed by IC with UV detection. HPLC was used to compare the efficiency of different nanosized TiO2, used to catalyse the UV photodegradation of typical textile dyes. An interesting works build a bridge from cultural heritage and environmental, a paleoenvironmental study of Triassic and Cretaceous clays to find separation of samples by means of cluster analysis. First of all I would like to thank all the authors for their great patience in following the Meeting's Abstract Template as well as for the prompt replies to the Referee's questions regarding papers included in this special issue. A big thanks to some friends and co-workers for their diligent help in corrections and proofs; in alphabetical order: M.I. Dias, J.B. Ghasemi, A. Kachbi, P. Ielpo, F. Marini, S.H. Plattner, M.P. Sammartino. The third meeting is planned for September 26-29, 2010 near the larger volcano of Europe, Taormina in Sicily Island (Italy). Also from this edition there is a “cheap course; Multivariate Analysis for Novices” in the three days before the meeting.

A quantitative structure - activity relationship (QSAR) study has been applied to a data set of 33 diphenyl ether herbicide with their inhibition data on protoporphyrinogen oxidase (PPO) enzyme. Diphenyl ethers (DPEs) are a class of herbicides that strongly and competitively inhibit the protoporphyrinogen oxidase (PPO) enzyme. PPO is the last common enzyme in the biosynthetic pathway to heme and chlorophyll. Two linear correlating models, multiple linear regression (MLR) and partial least squares (PLS) regression methods were used. Stepwise regression as a variable selection method was employed to develop a regression equation based on 26 training compounds, and predictive ability was tested on 7 compounds reserved for that purpose. A multi-parametric equation containing four structural descriptors with good statistical impact was obtained. The squared regression coefficients of prediction for the MLR and PLS regression methods were 0.95 and 0.94 respectively. The physicochemical meaning of the descriptors and their relations to the dependent variable are discussed.

One of the main issues still not resolved is to what extent casters were capable to change the composition of the bronze objects in order to meet the demands of the “market”. To face this problem it is necessary to study a large number of items produced by a single foundry with modern analytical techniques. The discovery of a Dolium at the end of 1800, buried near a furnace containing more than 14,000 pieces of bronze objects allowed performing compositional analysis on virtually every item of daily use. The objects were found in central Italy near Bologna in the so called “ripostiglio di San Francesco” (“hoard of San Francesco”). 431 measurements were carried out using portable energy dispersive x-ray fluorescence analysis (EDXRF). Abundance of the main elements (Cu, Sn, Pb, Fe, Sb, Ag, As) in the bronze alloy was analysed on 229 objects, after their brushing in order to remove the “patina” of oxidation. On 126 objects a single point was analysed (with measurement repetition), while on 155 objects two or more points were investigated. The research objects were chosen among the 14,000 pieces by museum curators and were grouped in 15 categories based on a visual and functional study. The complete data set was studied by chemometric analyses with Explorative Data Analysis techniques. The results of this preliminary study could not identify a clear correlation between composition and destination of use. However, some of the technical aspects of the fusion process were highlighted by this research.

Chemical mass balance modeling (CMB) was applied to determine the PM10 sources and their contributions. PM10 samples were collected in Lecce (40.338N, 18.108E, a town of South Italy), during two monitoring campaigns performed on July 2005 and February 2006. Nine source profiles and average mass concentration of the following chemical parameters: elemental carbon (EC), organic carbon (OC), chlorine (Cl-), nitrate (NO3 -), sulfate (SO4 2-), sodium (Na+), ammonium (NH4 +), potassium (K+), magnesium (Mg2+), calcium (Ca2+), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), manganese (Mn), iron (Fe), copper (Cu), lead (Pb), and zinc (Zn) were used to run the CMBmodel. The results obtained by application of CMB8.2 are shown. The contributions to PM10 show that dominant contributor was traffic with 37% followed by petroleum industry with 19% and field burning with 16%. Minor source contributions were marine aerosol (1%), ammonium sulfate production (4%), ammonium nitrate production (11%), oil-fired power plant (0.1%), gypsum handling (10%) and crustal (2%). Moreover, the Absolute Principal Component Scores (APCS) model was applied to the PM10 samples collected in order to find a correlation between the two source profile sets. With APCS model five source profiles were found and a good correlation (correlation coefficient bigger than 0.8) between crustal, marine, industrial profiles of CMB model and the corresponding ones of APCS model was found.

In this paper we have applied a chemometric treatment for investigating and comparing the element composition in potable water samples collected in two Italian urban areas, Rome and Florence, and analyzed by Instrumental Neutron Activation Analysis. The spectrum of drinkable tap Roman water shows very low limits of potentially toxic elements (Sb, Hg, Cr, Ni, etc.); in particular, they are present at levels below the values suggested by the European laws and the World Health Organization (WHO) guidelines. Further, it is also evidenced that the elemental composition is quite similar to that of uncontaminated natural waters. According to the Florence drinking water element characterization, the concentration values show an almost good situation except for Al. Comparing the two water systems a higher level of I, Se and some anthropogenic elements (Cu, Na, Zn) is found in Florence samples. A multivariate statistical treatment such as canonical analysis was performed for identifying the contribution of each element to the chemical composition of Roman water.

The presence of large quantities of toxic heavy metals (i.e. cobalt, chromium, lead, cadmium, zinc, etc.) in the environment may be a serious threat to humans. Hence, the development of novel methods able to eliminate these toxic contaminants from wastewater in efficient and economically viable ways is highly desirable. In this work we assayed the ability of two polymers, polyethylenimine (PEI) and its carboxylated derivative (PEI-COOH), to complex heavy metals and to remove them from contaminated water by polymer-assisted ultrafiltration. PEI is able to complex efficiently Ag, Al, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn and Zn and reduce their concentration in permeate to values <4 ppm. Interestingly, PEI is very efficient to remove Cr and Sn down to a concentration less than 0.1 ppm. Moreover, PEI-COOH derivative is more efficient than PEI to remove Ag, Al, Cd, Co, Cu, Ni, Pb, and Zn to a concentration less than 0.4 ppm (ICP-OES analysis). Our preliminary results indicate that PEI-COOH is able to complex those metals that are not complexed by PEI, hypothesising that the combined use of these two polymers may be efficiently employed as a powerful strategy for the complete removal of heavy metals from wastewater.

Lower Cretaceous and Triassic-Hettangian clays from the Algarve Basin (South Portugal) were deposited in distinct environments during basin subsidence due to Pangea break up. The mineralogy, geochemistry and granulometry of 45 samples of both clay groups were studied, using X-ray diffraction, instrumental neutron activation analysis, X-ray fluorescence and laser diffractometry by attenuation of X-rays. Multivariate statistical techniques (principal component analysis and K-means clustering), after scandium normalization of chemical contents, were used to study simultaneously all data, enabling to distinguish the different clay types by establishing the best discriminatory parameters: high contents (in decreased order) of kaolinite, quartz, Chemical Index of Alteration (CIA), Ti, goethite, Hf, Si, > 63 im fraction and Zr, characterize the group of clays from Cretaceous; while high contents of hematite, Mg, mobile elements (K, Cs and P), illite, Ca, phyllosilicates in general, Mn and dolomite, are associated to Triassic-Hettangian clays. This approach revealed useful to facilitate the integration of all data, as was possible to confront the geochemistry with the mineralogy, enabling the best palaeoenvironmental interpretations. In fact, the clay mineral assemblage is significantly influenced by the dominant weathering process and provides information on changes in aridity/humidity patterns.

In Romania and especially in Transylvania the process of creating icons implied the use of different supports, mainly wood and glass. Samples have been collected from various areas of these religious artefacts. The aim of this research is to apply a combination of FTIR spectroscopy and Mass Spectrometry techniques in order to identify and characterize the composition of the pigments, binders and varnishes used by Transylvanian icon's artisans. The information obtained through these procedures is part of the identification elements of the icons' period and school, and in the end it contributes to the technical expertise of these artefacts. Besides knowing the materials, the technology, the state of preservation and the patrimonial value of the artworks, the main goal is to better understand all the practical aspects of the active preservation and restoration procedures.

Laser Induced Breakdown Spectroscopy (LIBS) can be successfully used for cultural heritage applications, like pigment and stone identification or archaeological metal characterisation. In this work we focus on the study of wall paintings, working on a reference database of 30 commercial pigments traditionally used in murals and prepared with fresco, tempera (egg yolk, casein, animal glue) and oil techniques following ancient recipes. Two methods of signal analysis are tested for the automatic recognition of pigments and painting techniques. The first one is based on spectral lines identification for the detection of characteristic chemical elements. In the second one, we use two different chemometric models : soft independent modelling of class analogy (SIMCA) for the pigment identification and partial least-squares discriminant analysis (PLS-DA) for the technique characterisation. Results show the improvement of pigments and techniques recognition obtained with the multivariate analysis approach. As far as the real samples analysis is concerned, the signal processing has to be improved in order to remove non relevant and noisy information, such as background and thresholds that disturb the correct classification.

In this study, source regions of atmospheric sulfate and nitrate in rural areas at the Black Sea and the Mediterranean coasts of Turkey are compared. Stations on the Black Sea and Mediterranean Sea are located at Amasra and Antalya regions, respectively. Source regions of SO4 2- and NO3 - are determined by using potential source contribution function (PSCF). Statistical significance of source regions assigned by PSCF were assured using bootstrapping with 3000 iterations. Source regions affecting sulfate and nitrate concentrations at the Mediterranean and Black Sea regions have some similarities and differences. Emissions from source regions in Russia and Balkan countries affect both the Mediterranean and Black Sea basins.

Pattern recognition methods, i.e. the methods concentrating on the possibility of assigning an object to a class based on the result of a set of measurements are ubiquitous in chemometrics. In this paper, the main chemometric classification methods are discussed in terms of their nature, behavior, advantages and drawbacks. Both parametric and non parametric or discriminant and modeling techniques are illustrated together with a discussion of some applications to real world problems.

Small quantities of Roman mortars and stuccos from the Theatre of Marcellus and Porticus of Octavia were subjected to different instrumental techniques - thermogravimetric analysis (TG, DTG), Inductively Coupled Plasma Emission Spectroscopy (ICP-AES) and X-ray diffraction (XRD). The instrumental characterisation and chemometries allowed the stucco samples to be easily distinguished from the mortar. In practice, using the three instrumental analytical methods a total of 36 variables were obtained. The variables were then selected using PCA (Principal Component Analysis), reducing this number to 10. Lastly, using HCA (Hierarchical Cluster Analysis) a good separation was obtained between the two groups of samples (mortars and stuccos).

Spectrometric multicomponent analysis is a subject of great practical importance in the environmental, clinical, pharmaceutical and cultural heritage areas. Partial Least Squares (PLS) modeling based on SIMPLS algorithm was applied for the simultaneous spectrophotometric determination of Co(II), Ni(II) and Cu(II) with ammonium purpurate (murexide) as the complexing agent. An analytical wavelengths of (400 to 490) nm were chosen and an experimental calibration matrix for PLS was designed with 21 samples of (0.354 to 5.893) μg/mL, (0.352 to 5.869) μg/mL and (0.381 to 6.355) μg/mL for cobalt, nickel and copper, respectively. A leave one out cross-validation procedure was used for selecting the number of components using PRESS. The method was successfully applied to the simultaneous determination of these metals in industrial alloys.

New equipments and procedures to monitor in situ soluble salts content in stone materials were set up. They base on the extraction, by flowing ultrapure water, of soluble salts from stone surfaces and on the continuous registration of the real-time response of a conductometric probe; on the final collected solution, conductivity measure and analysis of anions by ionic chromatography can be performed in laboratory. A correlation between the signal obtained in situ and the chromatographic data was looked for; satisfying results were obtained but further investigation are needed in order to take into account all the involved parameters/variables and to extract the most significant index from the signal curve. It must be stressed that the actual normative on Cultural Heritage is scarce and in some case doesn't ensure a fully correct analytical procedure; anyway we compared our method with that indicated in the UNI11087. Surely a multivariate approach will be of help to optimize both the equipment and the procedure. The engineering of the apparatus must be improved too, so the presented results must be considered preliminary.

Due to its high intrinsic efficiency, heterogeneous catalysis is widely used in waste water treatments employing mixed catalysts. However, in this kind of catalysis it is extremely difficult to separate the suspended catalyst from the solution at the end of the procedure due to the small dimension of the particles. In environmental applications, the most used catalyst is titanium dioxide because of its great catalytic efficiency. The present research concerns the efficiency evaluation of TiO2 catalysts, estimated on the extent of photodegradation of target molecules after a radiation treatment (solar, UV, microwave) carried out in a dedicated apparatus. Experimental variables are: 1) catalyst type (TiO2 particles of different size), 2) catalyst concentration (0.1, 0.2, 0.5, 1.0 g/L), 3) exposure time (45 and 90 min), and 4) target molecules (five industrial textile dyes: Acid Blue 29, Alizarin Red S, Procion Red MX-5B, Reactive Blue 2, Acid Green 25). The efficiency of the photodegradation process has been evaluated by a UV/ Vis spectrophotometry comparing the spectra of the target substances obtained before and after the degradation process itself, therefore monitoring the cracking of the chromophore groups. Obtained data matrix was analysed with chemometric tools. The aim of this work was to identify the correlation between photodegradation efficiency and experimental variables. It has been also evaluated the possibility of substituting nanomaterial catalysts with catalysts characterized by bigger particle size keeping the degradation efficiency unaltered: this evaluation has been performed because the non- nanoparticles are more easily separable from suspension, making the water clarification post-processes easier.

Identification of artworks is mainly based on a few characteristics which can be observed using non-invasive tools (sight, touch, simple instruments), the investigated properties being geometry, weight, colours, texture, etc. Nowadays, technology allows reproducing all these characteristics to such an extent that even expert conservators can be deceived: in particular at the present time even the geometry of an artwork can be easily reproduced with the help of laser scanner analysis and with a rapid prototyping machine or a computer numerical control (CNC) milling machine. We propose a new tool, the Sonic Imprint, producing a code capable of identifying a rigid artefact from its vibrational resonance frequencies beyond doubt. In fact the vibration modes of an artefact strongly depend on the spatial distributions of its density and elastic parameters, as well as on its internal defects, definable in terms of abrupt changes of elastic properties in a small portion of the object. Then even small differences of these properties (differences usually present even among “identical” objects produced with industrial methods, at least in terms of defects) give appreciable variations of the Sonic Imprint codes, allowing secure identification of artworks, prevention of clonation and even damage monitoring. Moreover the procedure is really robust, rapid, inexpensive and not invasive. We tested it on a large number of commercial objects with the same shape and dimension and on many artworks in archaeological museums: an example is described. The application of this methodology to small-size artefacts (from small stones, vessels, pottery to medium-large coins) involves some problems in the detection of the Sonic Imprint. The problems, just due to the smaller sizes of this kind of objects, arise from the presence of higher resonance frequencies and larger damping of the induced vibrations. This implies that probes and instrumentation should be replaced to be adapted to the new experimental conditions.