Como resultado de los descubrimientos que establecieron en firme la teoría atómica de la materia en el primer cuarto del siglo XIX, los científicos pudieron determinar las masas atómicas relativas de los elementos conocidos hasta entonces. El desarrollo de la electroquímica durante ese periodo por parte de los químicos británicos Humphry Davy y Michael Faraday condujo al descubrimiento de nuevos elementos.

Multivariate statistical techniques such as factor analysis (FA), cluster analysis (CA) and discriminant analysis (DA), were applied for the evaluation of spatial variations and the interpretation of a large complex water quality data set of three cities (Lahore, Gujranwala and Sialkot) in Punjab, Pakistan. 16 parameters of water samples collected from nine different sampling stations of each city were determined. Factor analysis indicates five factors, which explained 74% of the total variance in water quality data set. Five factors are salinization, alkalinity, temperature, domestic waste and chloride, which explained 31.1%, 14.3%, 10.6%, 10.0% and 8.0% of the total variance respectively. Hierarchical cluster analysis grouped nine sampling stations of each city into three clusters, i.e., relatively less polluted (LP), and moderately polluted (MP) and highly polluted (HP) sites, based on the similarity of water quality characteristics. Discriminant analysis (DA) identified ten significant parameters (Calcium (Ca), Ammonia, Sulphate, Sodium (Na), electrical conductivity (EC), chloride, temperature (Temp), total hardness(TH), Turbidity), which discriminate the groundwater quality of three cities, with close to 100.0% correct assignment for spatial variations. This study illustrates the benefit of multivariate statistical techniques for interpreting complex data sets in the analysis of spatial variations in water quality, and to plan for future studies.

Water quality indices provide a simple and understandable tool for managers on the quality and possible uses for irrigation water, however an individual quality factor alone is not enough to evaluate the irrigation water quality because it could be restrictive and sometime it could give an unfavorable qualification. The aim of this paper was propose a quality profile of irrigation water using the preexisting water quality indices to be applied to arid and semiarid regions. As a case studied, the water of the Del Molle River (Nogolí, San Luis, Argentina) was researched. Samples were collected during the period

A study of the water quality of the Potrero de los Funes River (San Luis -Argentina) was carried out in order to evaluate the possible effect of the anthropogenic activities on the river developed in the homonymous town. Samples were collected during the period March 2000-November 2005 at three selected sampling sites (RP 1 , RP 2 and RP 3 ). Different physicochemical and bacteriological parameters (turbidity, pH, conductivity, suspended solids, alkalinity, potassium, sodium, calcium, magnesium, chlorides, nitrates, phosphates, sulphates, chemical oxygen demand (COD), 5-day biological oxygen demand (BOD 5 ), dissolved oxygen, total coliforms, Escherichia coli and total heterotrophic bacteria) were analysed according to the Standard Method for the Examination of Water and Wastewater. When comparing the values of total coliforms, E. coli, total heterotrophic bacteria, COD, BOD 5 and phosphates from the zone without anthropogenic influence (RP 1 ) and the urban zones (RP 2 and RP 3 ) an important variation in the parameters was observed. These results indicate that the urban activity produces a serious and negative effect on the water quality, thus constituting a sanitary risk and may have a major impact on the trophic status of the Potrero de los Funes dam. As case study, we report on the use of General Quality Index (GQI) to evaluate spatial and seasonal changes in the water quality of Potrero de los Funes River. Results revealed a significant degradation of the water quality at RP 2 and RP 3 .

Trace metals have negative effects on the oxidative stability of edible oils and they are important because of possibility for oils characterisation. A single-step procedure for trace elemental analysis of edible oils is presented. To this aim, a solubilisation with tetramethylammonium hydroxide (TMAH) was assayed prior to inductively coupled plasma mass spectrometry detection. Small amounts of TMAH were used, resulting in high elemental concentrations. This method was applied to edible oils commercially available in Argentine. Elements present in small amounts (Cu, Ge, Mn, Mo, Ni, Sb, Sr, Ti, and V) were determined in olive, corn, almond and sunflower oils. The limits of detection were between 0.004 lg g À1 for Mn and Sr, and 0.32 lg g À1 for Sb. Principal components analysis was used to correlate the content of trace metals with the type of oils. The two first principal components retained 91.6% of the variability of the system. This is a relatively simple and safe procedure, and could be an attractive alternative for quality control, traceability and routine analysis of edible oils.