Determination of monounsaturated alkyl side chain 2-alkylcyclobutanones in irradiated foods

The 2-alkylcyclobutanones (2-ACBs) are formed from triglycerides by irradiation treatment and may be used as markers for this type of food processing. This paper describes a detection method for the analysis of monounsaturated alkyl side chain 2-ACBs, which is formed upon irradiation from monounsaturated fatty acids which frequently are the most abundant fatty acids in foods. The estimated radioproduction yields of the cis-2-(dodec-5'-enyl)-cyclobutanones (cis-2-dDeCB) and the cis-2-(tetradec-5'-enyl)-cyclobutanones (cis-2-tDeCB) were 1.0 +/- 0.5 and 0.9 +/- 0.2 nmol.mmol(-1) precursor fatty acid.kGy(-1), respectively, being similar to that of saturated 2-ACBs. The stability study of the s- and mu-2-ACBs in poultry meat samples irradiated at 10 kGy and stored for 3-4 weeks at 4 degrees C and 25 degrees C showed that these compounds undergo some transformation, their amounts being reduced by about 50%. These storage losses did not depend on the saturation state of the alkyl side chain. The EI-MS detection limit of 2-tDeCB is 3 times higher (0.6 pmol) than that of 2-dodecylcyclobutanone (0.2 pmol). Consequently, when the oleic acid content of the analyzed food exceeds the content of palmitic acid by a factor of 3, it would be of an advantage to apply 2-tDeCB as a marker for detection of the irradiation treatment.     

Collaborative validation of the QuEChERS procedure for the determination of pesticides in food by LC-MS/MS

Seven FDA pesticide laboratories collaborated to develop and validate an LC-MS/MS method to determine 173 pesticides in <20 min. The average determination coefficient (r2) was >0.99 for all but two compounds tested. The limits of detection were <20 ng/mL for all compounds and <10 ng/mL for 363 of the 368 transitions reported. The method was used to determine pesticides in two AOAC sponsored proficiency samples. The LC-MS/MS determination was used for the analysis of oranges, carrots and spinach using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method. Each matrix was fortified at 20, 100, 400, and 1000 ng/g. No false positive responses were detected in controls of the three matrices. 165 pesticides had recoveries between 70 and 130%, and 161 had minimum detection levels less than 10 ng/g. Recoveries of 169 compounds for the 1000 ng/g spikes were within 50-150%. A matrix effect study indicated all three matrices caused a small net suppressing effect, the most pronounced attributable to the citrus matrix. The procedure proved to be accurate, precise, linear, sensitive and rugged, and adds 100 pesticides to the scope of the FDA pesticide program.     

Reduced Atmospheric Manganese in Montreal Following Removal of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Methylcyclopentadienyl manganese tricarbonyl (MMT) was used between 1990 and 2003 as an antiknock agent and as an octane booster in Canadian unleaded gasoline. Its combustion leads to Mn emissions. The objective of this research was to examine the variations in atmospheric Mn in Montreal (Canada) from 2001 to 2007, covering the period prior (2001?C2003) to and following (2005?C2007) MMT use. Three sampling stations were selected because of their proximity to roads with widely differing and well-known traffic patterns. Filters from 2001 to 2007 were obtained from the Montreal Urban Community. The first sample of each month was selected, and Mn analysis was performed by neutron activation analysis. Total suspended particulates (TSP) was calculated by weighing the filters before and after dust collection. Results show a significant decrease of Mn over time at each station, whereas TSP decreased significantly in two stations. Comparing atmospheric Mn during and after the period of use of MMT 2001?C2003 vs 2005?C2007 showed a significant decrease at all stations. For TSP, only one station showed borderline significant decline between these two periods. Overall, between the two periods, Mn and TSP decreased by 39% and 17%, respectively. These data suggest that the combustion of MMT led to an increase of airborne Mn of approximately 22%. These findings should help in decision-making processes concerning the use of MMT in gasoline in other countries.     

Enzymatic synthesis of aroma compound xylosides using transfer reaction by Trichoderma longibrachiatum xylanase

Enzymatic synthesis of aroma compound xylosides was performed by Trichoderma longibrachiatum xylanase. Information concerning the nature of xylosides present in the reaction medium was obtained by GC-EI-MS, by GC-NCI-MS of TFA derivatives, and by positive FAB-MS of the reaction mixtures. Moreover, the structures of isolated benzyl beta-D-xylopyranoside and 4-O-beta-xylopyranosyl-beta-D-xylopyranoside were established by (1)H and (13)C NMR and heteronuclear two-dimensional ((1)H-(13)C) chemical shift correlation. The results obtained for hexyl and benzyl alcohol xylosides indicated that a reaction implying a transfer of one to two or three xylose units from xylan was involved. The enzyme was able to recognize xylobiose, xylotriose, and xylan as xylose donors. Benzyl xyloside, produced independently of xylobioside and xylotrioside, was found as the major kinetic product of the reaction. Benzyl xyloside was produced in higher quantities and at a higher rate than that obtained for the di- and trixyloside derivatives. The maximum production for benzyl xyloside, 1.29 g/L, was obtained in the presence of hexane (50%) used as cosolvent. Xylosides and xylobiosides of several aroma compounds, (Z)-hex-3-en-1-ol, heptan-2-ol, geraniol, nerol, and citronellol, were synthesized in different amounts, from 850 mg/L for (Z)-hex-3-en-1-yl xylosides to 1.5 mg/L for citronellyl xylosides. No synthesis occurred when menthol, linalool, and eugenol were used as acceptors.     

In situ quantification of CH<Subscript>4</Subscript> bubbling events from a peat soil using a new infrared laser spectrometer

Purpose  

CH₄ emissions from peatlands are space and time dependent. The variety of efflux routes contributes to these variabilities. CH₄ bubbling remains difficult to investigate since it occurs on a timescale of seconds. The aims of this study were to use for the first time the recently built infrared high-resolution spectrometer, SPectrometre Infra-Rouge In situ Troposphérique to (1) measure in situ CH₄ fluxes in natural and artificial peatland plot and (2) observe online bubbling events with quantification of CH₄ emission fluxes corresponding to this very sudden degassing event.     

Comment on "Mixed-layer deepening during Heinrich events: a multi-planktonic foraminiferal delta18O approach"

Rashid and Boyle (Reports, 19 October 2007, p. 439) analyzed oxygen isotopes in planktonic foraminera from marine sediments and concluded that Heinrich events (massive iceberg discharges into the North Atlantic Ocean) caused upper water masses to deepen. We question the robustness of this interpretation and argue that a strongly stratified mixed layer characterized by dense sea-ice cover and production of oxygen-18-depleted brines likely prevailed during such events.     

Effects of Aeration, Alum Treatment, Liming, and Organic Matter Application on Phosphorus Exchange between Soil and Water in Aquaculture Ponds at Auburn, Alabama

Application of readily-oxidizable organic substrate to laboratory soil-water systems and fish ponds caused anaerobic conditions in bottom soil and water, and concentrations of soluble reactive phosphorus (SRP) increased. Aeration of ponds increased total phosphorus (TP) concentrations by suspending soil particles in the water, but SRP concentrations declined because of increased oxy- genation of bottom water and soil, Alum [Al₂(SO₄)₃·14H₂O] treatment of ponds reduced SRP and TP concentrations in ponds, but the low concentration of alum used, 20 mg/L, had little residual effect on phosphorus concentration. Application of agricultural limestone at 0.2 kg/m² to ponds with soil pH of 5.5 and Ca²⁺ concentration of 5 mg/L did not affect SRP and TP concentration. Unless pond soils were anaerobic at their surfaces, a condition not acceptable in thermally-unstratified fish ponds, soils released little phosphorus to the water. Strong adsorption of phosphorus by soils in intensive ponds with feeding is beneficial, because removal of phosphorus by aerobic soils is a control on excessive phytoplankton growth. In fertilized ponds, phosphorus must be applied at frequent intervals to replace phosphorus removed from the water by soils.     

A quantum laser pointer

The measurement sensitivity of the pointing direction of a laser beam is ultimately limited by the quantum nature of light. To reduce this limit, we have experimentally produced a quantum laser pointer, a beam of light whose direction is measured with a precision greater than that possible for a usual laser beam. The laser pointer is generated by combining three different beams in three orthogonal transverse modes, two of them in a squeezed-vacuum state and one in an intense coherent field. The result provides a demonstration of multichannel spatial squeezing, along with its application to the improvement of beam positioning sensitivity and, more generally, to imaging.     

CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun

Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.