José Ricardo Carneiro

Determination of E-2-nonenal by high-performance liquid chromatography with UV detection: Assay for the evaluation of beer ageing

The analysis of E-2-nonenal is of considerable interest for the brewery industry as this compound is claimed to be responsible for a paper/cardboard unpleasant flavour. Usually, the presence of E-2-nonenal can be noticed in aged beers at levels higher than 0.1 microg/l. In this work, an analytical method was developed to determine E-2-nonenal in beer involving steam distillation of beer followed by an extraction/concentration step using solid-phase extraction and determination of E-2-nonenal by HPLC with UV detection. Fastness and simplicity are the main advantages of the proposed method, when compared with other existing methodologies for the determination of E-2-nonenal in beer. Using the developed conditions, the interference of E-2-nonenal formed by degradation of its precursors during steam distillation is almost negligible. The presence of sulphur dioxide at legal levels does not interfere with the assay. The method was used in a comparative study of fresh and either naturally or forced aged beers. A much larger chromatographic peak was found near the peak of E-2-nonenal that correlates well with the peak of E-2-nonenal. Identification of the corresponding compound is currently under investigation, considering its future application on the evaluation of beer ageing.

Soil–geosynthetic inclined plane shear behavior: influence of soil moisture content and geosynthetic type

Abstract This paper deals with the inclined plane shear on three different geosynthetics (a geocomposite (GC), a non-woven geotextile (GTX), and an extruded geogrid (GGR)) with a residual soil from granite. Soil and geosynthetic properties, test equipment, and procedures are described. The influence of soil moisture content and geosynthetic type on soil–geosynthetic interaction behavior is discussed by analyzing the results of the inclined plane shear tests. The main conclusions that can be outlined from the present study are the following: (1) the influence of soil moisture content was relevant for the soil–GTX and soil–GC interfaces. Indeed, the resistance of those interfaces decreased with the increase of soil moisture content. No significant differences were observed between the behavior of those geosynthetics; (2) the influence of soil moisture content on the behavior of the soil–GGR interface was less evident. A slight decrease on the interface friction angle was only observed for the highest soil moisture content; (3) the dry soil–GGR interface resistance was lower than that observed for the other two geosynthetics due to the relevance of soil–soil friction at the GGR apertures, to the high percentage of fines of the soil used in the research (D50 = 1·00 mm), and to the smoother solid lateral surface of the extruded GGR when compared with the surface of the GTX or GC.

Accelerated weathering of polypropylene geotextiles

Abstract This paper reports research about the durability of non-woven geotextiles when exposed to artificial weathering conditions [ultraviolet (UV) radiation, rain and dew] on a laboratory weatherometer. The geotextiles were specially manufactured from polypropylene fibers stabilized with different amounts of the additive Chimassorb 944 and the pigment carbon black. The degradation suffered by the geotextiles was evaluated by tensile tests and by scanning electron microscopy.

Determination of Chimassorb 944 in Polypropylene Geotextiles by HPLC-UV

This paper reports the development of a method for the determination of Chimassorb 944 (C944), in polypropylene geotextiles, by high performance liquid chromatography with ultraviolet detection. The C944 was removed from the geotextiles by an ultrasonic extraction and then separated in a NH2 column, followed by UV detection at 244 nm. Analytical validation showed that the method is accurate and precise. The developed methodology was applied for the determination of C944 in geotextiles exposed to artificial UV radiation and to natural weathering. To the best of our knowledge, this is the first method proposed for the determination of C944 in geotextiles.

Laboratory Evaluation of Interactions in the Degradation of a Polypropylene Geotextile in Marine Environments

The long-term behaviour of geosynthetics applied in coastal engineering structures can be adversely affected by many agents. This paper studies the resistance of a nonwoven polypropylene geotextile against some degradation agents present in marine environments and evaluates the existence of interactions between them. For that purpose, the geotextile was exposed to some laboratory degradation tests: immersion tests (in seawater, deionised water, and sodium chloride 35 g·L−1), thermooxidation, and artificial weathering. The geotextile was (1) exposed separately to each degradation test and (2) exposed successively to combinations of two or three degradation tests. The damage caused by the degradation tests was evaluated by monitoring the tensile properties of the geotextile. Based on the changes occurred in tensile strength, reduction factors were determined. The reduction factors obtained directly in the multiple exposures were compared with those obtained by the traditional methodology for the combined effect of the degradation agents. The results, among other findings, showed the existence of relevant interactions between the degradation agents and showed that the reduction factors obtained by the traditional methodology were unable to represent accurately (by underestimating) the degradation occurred in the geotextile.

Resistance of Geotextiles Against the Isolated and Combined Effect of Mechanical Damage Under Repeated Loading and Abrasion

The installation procedures (which may cause mechanical damage) and abrasion may provoke unwanted changes in the properties of the geosynthetics, affecting their performance. This work evaluated the resistance of two geotextiles (with different structures) against two degradation mechanisms: mechanical damage under repeated loading and abrasion. The geotextiles were (1) exposed in isolation to each degradation mechanism and (2) exposed consecutively to both degradation mechanisms. The damage suffered by the geotextiles (in the degradation tests) was evaluated by monitoring changes in their tensile and static puncture behaviour. Based on the changes occurred in tensile and puncture strength, reduction factors were determined. The reduction factors obtained in the successive exposure to mechanical damage under repeated loading and abrasion were compared with the reduction factors determined by the traditional methodology for the combined effect of those degradation mechanisms.

Mechanical Damage of Geosynthetics Used in the Base Liner System of Landfills Caused by Different Aggregates

The installation process may cause unwanted changes in the mechanical behaviour of the geosynthetics. In this work, some geosynthetics used in the base liner system of landfills (a combination of a geotextile, a geomembrane and a geosynthetic clay liner) were submitted to mechanical damage under repeated loading tests (procedure adapted from EN ISO 10722), being monitored the changes occurred in their short-term behaviour. The mechanical damage under repeated loading tests consisted in placing the geosynthetics between a flexible base (granite residual soil with a relative density of 80%) and an aggregate and submitting them to cyclic dynamic loading. The geosynthetics were damaged with a natural aggregate (gravel 14/20), a recycled ceramic aggregate and corundum (synthetic aggregate used in EN ISO 10722). The damage suffered by the geosynthetics was evaluated by monitoring changes in their tensile, tearing (only for the geomembrane) and static puncture properties.