Determination of glyphosate and aminomethylphosphonic acid in soybean samples by high performance liquid chromatography using a novel fluorescent labeling reagent

A highly sensitive pre-column derivatization HPLC method for simultaneous determination of glyphosate (GLYP) and its major metabolite aminomethylphosphonic acid (AMPA) in soybean samples was developed. The analytes were labeled with a novel fluorescent labeling reagent 3,6-dimethoxy-9-phenyl- 9H-carbazole-1-sulfonyl chloride (DPCS-Cl) at 70 °C for 25 min. The optimized concentration of DPCS-Cl was 25 μg mL-1 and the molar ratio of analytes to DPCS-Cl was 1:4.2. The derivatives were separated on a reversed-phase column by gradient elution and were monitored with fluorescence detection at 318 nm (excitation) and 440 nm (emission). The method linearity, calculated for GLYP and AMPA, had a correlation coefficient greater than 0.999. The detection limits for GLYP and AMPA were 0.02 ng mL-1 and 0.01 ng mL-1 (S/N = 3), respectively. In addition, a simple sample pretreatment for the soybean samples was developed to extract GLYP and AMPA. The recovery of extraction was more than 95%. Then, this method gave the detection limits of 0.002 mg kg-1 for GLYP and 0.001 mg kg-1 for AMPA in soybean samples. This HPLC method was applied to the determination of glyphosate and AMPA in soybean samples with its merits of simplicity in pretreatment, rapidity in derivatization, stability of the derivatives and high sensitivity. © 2013 The Royal Society of Chemistry

Distribution of Spectral Lags in Gamma Ray Bursts

Using the data acquired in the Time To Spill (TTS) mode for long gamma-ray bursts (GRBs) collected by the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory (BATSE/CGRO), we have carefully measured spectral lags in time between the low (25-55 keV) and high (110-320 keV) energy bands of individual pulses contained in 64 multi-peak GRBs. We find that the temporal lead by higher-energy gamma-ray photons (i.e., positive lags) is the norm in this selected sample set of long GRBs. While relatively few in number, some pulses of several long GRBs do show negative lags. This distribution of spectral lags in long GRBs is in contrast to that in short GRBs. This apparent difference poses challenges and constraints on the physical mechanism(s) of producing long and short GRBs. The relation between the pulse peak count rates and the spectral lags is also examined. Observationally, there seems to be no clear evidence for systematic spectral lag-luminosity connection for pulses within a given long GRB.Comment: 20 pages, 4 figure

Research Progress on Starfish Outbreaks and Their Prevention and Utilization: Lessons from Northern China.

Starfish are keystone species as predators in benthic ecosystems, but when population outbreaks occur, this can have devastating consequences ecologically. Furthermore, starfish outbreaks and invasions can have adverse impact economically by impacting shellfish aquaculture. For example, an infestation of starfish in Qingdao led to a 50% reduction in sea cucumber production and an 80% reduction in scallop production, resulting in an economic loss of approximately RMB 100 million to oyster and other shellfish industries. Addressing the imperative need to proactively mitigate starfish invasions requires comprehensive research on their behavior and the underlying mechanisms of outbreaks. This review scrutinizes the historical patterns of outbreaks among diverse starfish species across various regions, delineates the factors contributing to the proliferation of Asterias amurensis in Chinese waters, articulates preventive and remedial strategies, and outlines the potential for the sustainable utilization of starfish

The instability of diffusive convection and its implication for the thermohaline staircases in the deep Arctic Ocean

In the present study, the classical description of diffusive convection is updated to interpret the instability of diffusive interfaces and the dynamical evolution of the bottom layer in the deep Arctic Ocean. In the new consideration of convective instability, both the background salinity stratification and rotation are involved. The critical Rayleigh number of diffusive convection is found to vary from 10³ to 10¹¹ in the deep Arctic Ocean as well as in other oceans and lakes. In such a wide range of conditions, the interface-induced thermal Rayleigh number is shown to be consistent with the critical Rayleigh number of diffusive convection. In most regions, background salinity stratification is found to be the main hindrance to the occurrence of convecting layers. With the new parameterization, it is predicted that the maximum thickness of the bottom layer is 1051 m in the deep Arctic Ocean, which is close to the observed value of 929 m. The evolution time of the bottom layer is predicted to be ~ 100 yr, which is on the same order as that based on ¹⁴C isolation age estimation