Roger Fuoco

GC-MS characterization of proteinaceous and lipid binders in UV aged polychrome artifacts

This paper presents the most significant results obtained from the characterization of protein and lipid binders in a broad range of reference paint materials prepared and stored at Opificio delle Pietre Dure in Florence (Italian Ministry of the Cultural Heritage, Italy). The amino acid distribution for protein binders and the fatty acid distribution for lipid binders were determined by gas chromatography-mass spectrometry before and after being artificially aged through exposure to UV light at 254 nm or 366 nm for different time periods in a climatic chamber (20°C and 80% RH). The results were compared with those relevant to old paintings of different ages, and showed that UV light aging does not significantly affect the amino acid profile of protein binders. Consequently, protein binders in old paintings can be reliably identified by comparing the amino acid composition with that of reference paint materials which have not been aged. However, the composition of lipid binders is substantially affected by UV irradiation, leading to a lowering of oleic acid and the formation of azelaic acid and other dicarboxylic acids including oxalic acid. An oleic to stearic acid ratio of less than 0.5 was observed in all the samples of works of art, and this parameter can be used to evaluate the extent of the artificial aging process. The formation of oxalic acid was also observed starting with pure unsaturated fatty acids, thus supporting the chemical origin of oxalate patina.

GC-MS characterization of paint varnishes

Abstract This paper presents an analytical procedure based on gas chromatography separation and mass spectrometric identification, which allows the determination of natural resins, waxes and lipids in the same microsample (

Characterization of proteinaceous binders in wall painting samples by microwave-assisted acid hydrolysis and GC-MS determination of amino acids

AbstractAn analytical procedure for the characterization of proteinaceous binders (milk or casein, egg and animal glue) in artistic wall painting samples is described. The method is based on microwave-assisted acid hydrolysis of the sample, and on derivatization of the amino acids freed with a silylating agent and their quantitative determination by gas chromatography/mass spectrometry. The procedure was tested on wall painting reference samples, and showed a typical protein recovery of about 70% at 0·1mg sample size. Fourteen amino acids were determined and some ratios between their concentrations were selected, so that the proteinaceous binders in the sample could be identified. Results on some samples from frescoes from the Monumental Celnetery in Pisa (Italy) showed that the amino acid composition of casein differed significantly from that expected, as a result of degradation processes due to aging and moisture.

Comparative determination of some phytohormones in wild-type and genetically modified plants by gas chromatography–mass spectrometry and high-performance liquid chromatography–tandem mass spectrometry

The analytical performances of two optimized analytical methodologies used for the determination of auxins, cytokinins, and abscisic acid in plant samples were critically compared. Phytohormones were extracted from Nicotiana glauca samples using a modified Bieleski solvent and determined both by gas chromatography-mass spectrometry (GC-MS), after derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), and by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) on the Bieleski extract without any further treatment. HPLC-MS/MS gave better results in terms of higher coefficients of determination of the calibration curves, higher and more reproducible recoveries, lower limits of detection, faster sample preparation, and higher sample throughput. Thus, two sets of N. glauca and N. langsdorffii samples, both wild-type and genetically modified by inserting the glucocorticoid receptor (GR) gene encoding for the rat glucocorticoid receptor, were first characterized by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and then analyzed by HPLC-MS/MS. Significant differences in the phytohormone content between the two sample sets were found and are very important in terms of understanding the mechanisms and effects on growth processes and the development of transgenic plants.

A GC-MS study on the deterioration of lipidic paint binders

Abstract This paper presents a study on the degradation of lipidic paint binders induced by irradiation with UV light (365 nm), exposure to urban air pollutants such as NOx and SO2 and combinations of the various treatments. The characterisation of lipidic binders has been performed by a GC-MS procedure on a series of non-pigmented paint specimens prepared at the Opificio delle Pietre Dure–Firenze (Italy) and submitted to accelerated ageing. The results show that UV irradiation and exposure to NOx and SO2 increased the polymerisation and cross-linking of the paint thus facilitating the cleavage of fatty acid chains as a result of progressed oxidation up to the formation of oxalic acid. The presence of oxalic, malonic, succinic, glutaric, adipic, pimelic, OH-octadecenoic acids and cholestenes describes the behaviour of aged paint layers. In samples of paintings by Cimabue, Raffaello and Boucher, oxalic acid and oxidised carboxylic acids have been found, confirming the results obtained in the paint specimens.

ELECTROCHEMISTRY OF S-TRIAZINE HERBICIDES - REDUCTION OF ATRAZINE AND TERBUTYLAZINE IN AQUEOUS-SOLUTIONS

Abstract The electrochemical behavior of both herbicides is qualitatively similar. The two-electron reduction of atrazine (2-chloro-4-ethylamino 6-isopropylamino- 1,3,5- triazine) proceeds only in acidic media where the preceding protonation takes place (pK = 1.44). In solutions of higher pH (2–4) the observed reduction current is kinetically controlled by protonation and the estimated value of the protonation rate constant is kr = 2400 ± 400 mol−1 1 s−. The products of reduction were identified by large-scale electrolysis followed by GC-MS analysis. The electron transfer reaction causes cleavage of the Cl atom and loss of the ethyl group yielding the respective products in the ratio approximately 4:1. The electrochemical properties of terbutylazine are characterized by the protonation constant pK = 2.37 and rate constant kr = 1900 ± 200 mol−1 1 s−1.

Measurement of Warfarin in the Oral Fluid of Patients Undergoing Anticoagulant Oral Therapy

Background Patients on warfarin therapy undergo invasive and expensive checks for the coagulability of their blood. No information on coagulation levels is currently available between two controls. Methodology A method was developed to determine warfarin in oral fluid by HPLC and fluorimetric detection. The chromatographic separation was performed at room temperature on a C-18 reversed-phase column, 65% PBS and 35% methanol mobile phase, flow rate 0.7 mL/min, injection volume 25 µL, excitation wavelength 310 nm, emission wavelength 400 nm. Findings The method was free from interference and matrix effect, linear in the range 0.2–100 ng/mL, with a detection limit of 0.2 ng/mL. Its coefficient of variation was <3% for intra-day measurements and <5% for inter-day measurements. The average concentration of warfarin in the oral fluid of 50 patients was 2.5±1.6 ng/mL (range 0.8–7.6 ng/mL). Dosage was not correlated to INR (r = −0.03, p = 0.85) but positively correlated to warfarin concentration in the oral fluid (r = 0.39, p = 0.006). The correlation between warfarin concentration and pH in the oral fluid (r = 0.37, p = 0.009) confirmed the importance of pH in regulating the drug transfer from blood. A correlation between warfarin concentration in the oral fluid and INR was only found in samples with pH values ≥7.2 (r = 0.84, p = 0.004). Conclusions Warfarin diffuses from blood to oral fluid. The method allows to measure its concentration in this matrix and to analyze correlations with INR and other parameters.

Simultaneous determination of arsenic, selenium, tin and mercury by non-dispersive atomic fluorescence spectrometry.

A procedure is described for simultaneous determination of arsenic, selenium, tin and mercury in aqueous solution by non-dispersive atomic-fluorescence spectrometry. Radiofrequency-excited EDLs, 100% modulated in the kHz region, were used for atom excitation. Sodium tetrahydroborate was used as reductant and a hydrogen-argon miniflame as atomizer. In the optimized procedure, which uses 1 ml of sample, the limits of detection (three times the standard deviation of the blank) were 0.04, 0.08, 0.1 and 0.1 ng ml for arsenic, selenium, tin and mercury respectively. The linear dynamic range was greater than three decades for all analytes and the precision was better than 7% (typically 3%) for concentrations 1 ng ml . Results for mutual interference effects are reported. Copper, nickel, lead and cobalt interfered only with selenium (5 ng ml ), when present in at least 200-fold weight ratio to it. Using 5 ml of sample improved the limits of detection for selenium and arsenic (0.01 and 0.02 ng ml respectively), but at the expense of greater interference. Recovery from spiked natural water samples was better than 95% at the ng ml level, except for selenium in sea-water, when the recovery was only 85%. Determination of the four elements, including standard-addition and background measurements, requires about 10 min.

Determination of Polychlorobiphenyls in Environmental Samples from Antarctica

Abstract The analysis of PCBs in sea water samples gathered during the 1990–91 Italian expedition in Terra Nova Bay—Gerlache Inlet showed a typical total concentration of 550 pg/l. A slight increase in PCB content was observed in the surface layer of the water column before pack ice melting, while an increase by a factor of about two was found in the same water layer after pack ice melting. PCBs were also measured in marine sediment, lake sediment and soil samples collected at Terra Nova Bay, Wood Bay and Victoria Land during the 1989–1990 Italian expedition. The relevant concentrations ranged between 45–361, 102–560 and 61–120 pg/g respectively and were strongly dependent on the total particle surface of each sample. PCB congener distributions were centered on 3- to 6-substituted and on 4- to 7-substituted congener classes for sea water and sediment/soil samples respectively, and were typical for each matrix considered.

Polychlorobiphenyls in Sediment, Soil and Sea Water Samples From Antarctica

Abstract The presence of PCBs was evaluated in environmental samples collected in Antarctica during the 1990–91 and 1991–92 Italian Expeditions by using an optimized procedure for GC-ECD peak assignment. In particular, marine sediment samples from Terra Nova Bay and Ross Sea, and lake sediment and soil samples from Victoria Land, near to the Italian Base (BTN) (1990–1991 expedition) were collected and analyzed. The relevant PCB concentrations ranged between 30–160, 60–120 and 40–70 pg/g respectively, and were strongly dependent on the particle size distribution of each sample as found in previous expeditions. The depth profiles of PCB content in marine sediment samples collected in a few stations clearly show that PCBs are confined in a surface layer of about 10 cm. A coastal sea water depth profile of PCBs before and after pack ice melting was also obtained by collecting samples in Terra Nova Bay—Gerlache Inlet (1990–91 expedition). The total PCB concentration was about 140 pg/1 and was practically const...