Characterisation and authentication of A. senegal and A. seyal exudates by infrared spectroscopy and chemometrics.

The authentication of Acacia gums samples requires usually the use of sophisticated and time consuming analytical techniques. There is a need for fast and simple analytical techniques for the objective of a quality control methodology. Commercial Acacia senegal and Acacia seyal gums present characteristic MIR spectra. Principal Component Analysis of the infrared spectra of gum exudates of trees allow to distinguish Acacia gums from another gum exudates (Combretum, Ghatti, Karaya, Tragacanth). Moreover, gums of A. senegal and A. seyal separate them and from other Acacia species (Acacia dealbata, Acacia karoo, Acacia nilotica, Acacia sieberiana). Chemometric treatments of A. senegal and A. seyal MIR spectra were assessed for the quantification of moisture content in Acacia gums, for the classification into the two species and for the adulteration detection and quantification. Results were quite satisfactory, the moisture content was estimated at 3.1%, adulteration was detected at 3.4% and quantified at 5.6%. The discrimination of the two species is done without any ambiguity.

Hydrocarbons in coastal sediments from the Mediterranean sea (Gulf of Fos area, France).

Sedimentary hydrocarbons have been studied quantitatively and qualitatively in 11 coastal stations located in the Gulf of Fos (French Mediterranean coast). Hydrocarbon levels ranged from 10 to 260 mg kg(-1) sed. dry weight. A new parameter "NAR" (Natural n-alkane ratio) is proposed to evaluate the contribution of terrestrial inputs of hydrocarbons in the sediments. The origins of hydrocarbons are multiple: terrestrial inputs, biogenic, pyrolytic (industry emissions mainly steel and iron industries, ship and road traffic). Generally, the main source of contamination is not petroleum. Several ratios between parent polycyclic aromatic hydrocarbons show that the sources of hydrocarbons in the sediments are generally much more pyrolytic than petrogenic.

Applications of diamond crystal ATR FTIR spectroscopy to the characterization of ambers.

Diamond crystal ATR FTIR spectroscopy is a rapid technique with virtually no sample preparation which requires small sample amounts and showed potential in the study of ambers. FTIR spectra of ambers present discriminating patterns and can be used to distinguish amber from immature resins as copal, to determine local or Baltic origin of archaeological ambers and to detect most of the falsifications encountered in the amber commercialisation.

Sources of hydrocarbons in sediments of the Bay of Fort de France (Martinique).

Sedimentary hydrocarbons have been studied quantitatively and qualitatively in 16 stations of the Bay of Fort de France (Martinique). Hydrocarbon levels ranged from 54 to 1045 mg kg(-1) sed. dry weight. Origin of hydrocarbons are multiple: biogenic (terrestrial inputs), pyrolytic (residues of natural or anthropogenic combustions), diagenetic and anthropogenic (petroleum contamination). Generally high levels of hydrocarbons are not associated to a petroleum contamination. The main source of hydrocarbons in the mangrove coastal zones of the Bay of Fort de France seems to be the early diagenetic degradation products of 3-oxytriterpenoids. Excepted two stations, petroleum contamination is very low or absent.

Influence of growth phase on the phospholipidic fatty acid composition of two marine bacterial strains in pure and mixed cultures.

This in vitro study was conducted in order to determine the effects of hydrocarbons and growth phase on the phospholipid ester-linked fatty acid composition of two marine sedimentary hydrocarbon-degrading bacteria. These two strains, namely Corynebacterium sp. and Sphingomonas sp. 2MPII, were cultivated on either a simple soluble substrate (ammonium acetate) or a hydrocarbon (respectively n-eicosane and phenanthrene). The incubations were stopped at different times corresponding to point of lag (2 days), exponential (7 days) and stationary phases (21 and 56 days). The effects of growth phase and hydrophobic substrates were successfully demonstrated by a simple index, given as the sum of saturated fatty acids divided by the sum of unsaturated fatty acids ( summation operatorSFA/ summation operatorMUFA), ranging from 1.4 to 3, 0.3 to 0.6, and 0.5 to 1.0 for Corynebacterium sp., Sphingomonas sp. 2MPII, and mixed cultures, respectively. This result was validated by a principal component analysis. In pure cultures, the phospholipid fatty acid (PLFA) composition was strongly influenced by both the carbon source and the growth phase. Nevertheless, the two strains showed different "behaviors". For 2MPII, the main PLFA composition changes were observed at 2 days while they were progressive as a function of time for Corynebacterium sp. These differences could explain the evolution of PLFAs of mixed cultures.