Objective: A new ion exchange column technology was used to establish an efficient and sensitive method for the detection of inorganic arsenic. Methods: Based on the new As Specia Fast Column, the pretreatment methods, liquid phase separation and mass spectrometry determination conditions of inorganic arsenic in rice were optimized. Finally, arsenic compounds were separated by As Specia Fast Column and detected by liquid chromatography inductively coupled plasma mass spectrometry. The external standard method was used for quantitative analysis. The detection limit, precision and accuracy of the method were determined by measuring the content of arsenic compounds in rice samples and rice standard samples. At the same time, three Guangdong rice samples were selected as the experimental samples of this study, and 1 g of each sample was weighed and measured in parallel three times. The method was compared with the method of liquid chromatography-atomic fluorescence spectrometry (LC-AFS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) in the national standard. Results: The inorganic arsenic in rice was extracted with 0.5% nitric acid solution at 65 ℃ for 15 h, and the pH was adjusted to alkaline. The mobile phase A (8 mmol/L HNO₃, 50 mmol/L NH₃·H₂O) and mobile phase B (40 mmol/L HNO₃, 80 mmol/L NH₃·H₂O) were used as the mobile phase gradient elution (93%) . Five arsenic compounds can reach baseline separation under the conditions of RF power of 1 500 W and atomization gas flow of 0.97 L/min. The detection limits ranged from 0.114 to 0.331 μg/L, and the inorganic arsenic content in rice samples ranged from 0.063 to 0.232 mg/kg. The results of determination of arsenic compounds in rice flour reference materials were all within the uncertainty range indicated by the standard. The recoveries were 86.7%~106.7%, and the precision was 1.9%-12.5%. Compared with national standards, the results of determination of arsenate in rice were relatively close (using this method, LC-AFS, LC-ICP-MS to detect the content of arsenate in rice samples 1 was 0.231, 0.226, 0.236 mg/kg, respectively). However, due to insufficient sensitivity, the national standard method is difficult to detect low levels of arsenic compounds (Arsenobetaine was not detected in rice sample 1). The method can detect the content of arsenobetaine in rice sample 1 was 0.023 mg/kg. Conclusion The established method can meet the requirements of inorganic arsenic determination in rice, and it is more rapid and accurate than the current national standard. It can better monitor and evaluate the content of i-As in rice, and provide accurate data for comprehensively grasping and evaluating the safety of rice consumption of residents.

Objective To explore whether receptor interacting protein (RIP)1/RIP3 pathways participate in glutamate induced cell death in HT-22 neuronal cells and investigate the potential neuroprotection ofnecrostatin-1 in glutamate induced cell death in HT-22.Methods (1) In vitro cultured mouse hippocampal neuronal HT-22 cells were divided into control group,zVAD group,necrostatin-1 (Nec-1) group,glutamate group,glutamate+zVAD group,glutamate+zVAD+Nec-1 group and glutamate+Nec-1 group;they were treated with zVAD,Nec-1 and glutamate at the final concentrations of 20 μmol/L,30 μmol/L and 3 mmol/L for 24 h.Cell viability was detected using a luminescence-based commercial kit Cell Titer-Glo (CTG).Necrotic cell death was measured by propidium iodide (PI) and HE stainings.(2) HT-22 cells were divided into control group Ⅰ,glutamate group Ⅰ and glutamate+Nec-1 group Ⅰ;MitoSox Red was used to detect mitochondrial reactive oxygen species (ROS) level.(3) HT-22 cells were divided into control group Ⅱ,glutamate group Ⅱ and glutamate+tertiary butyl-hydroxyanisole (BHA) group;the final concentration of BHA was 100 μmol/L;necrotic cell death was measured by PI and HE stainings after 24 h of treatment.(4) HT-22 cells were divided into RIP3 siRNA and control group Ⅲ,and then,they were transfected with RIP3 siRNA or negative siRNA,respectively;the RIP3 protein expression was determined by Westem blotting after 72 h of treatment.(5) HT-22 cells were divided into negative siRNA+Control,RIP3 siRNA,negative siRNA+glutamate and RIP3 siRNA+glutamate groups;the cells were transfected with RIP3 siRNA or Negative siNRA,respectively;48 h later,the glutamate groups were treated with 3 mmol/L glutamate;PI positive cells and cell viability were measured by PI and HE stainings and CTG at 24 h after glutamate treatment.Results (1) As compared with control group,percentage of PI positive cells was greatly increased and cell viability was decreased in glutamate group and glutamate+zVAD group,with statistically significant differences (P＜0.05);as compared with those in the glutamate group,percentage of percentage of PI positive cells was was significantly decreased and cell viability was statistically increased in glutamate+Nec-1 group (P＜0.05).(2) ROS level in HT-22 cells of the glutamate group was significantly increased than that in the control group Ⅰ (P＜0.05);however,ROS level in HT-22 cells of glutamate+Nec-1 group Ⅰ was significantly decreased than that in glutamate group Ⅰ (P＜0.05).(3)Percentage of PI positive cells in the glutamate group Ⅱ was significantly higher than that in the control group Ⅱ (P＜0.05),and that in the glutamate+BHA group was statistically lower than that in the glutamate group Ⅱ (P＜0.05).(4) The RIP3 protein expression in the RIP3 siRNA group was obviously down-regulated as compared with that in the control group Ⅲ.(5) As compared with those in the negative siRNA group,percentage of PI positive cells was statistically increased and cell viabilities were statistically decreased in glutamate group (P＜0.05);however,percentage of PI positive cells was significantly decreased and cell viability was significantly increased in RIP3 siNRA+glutamate group as compared with those in the glutamate group (P＜0.05).Conclusion RIP1/RIP3 pathway and ROS might mediate glutamate induced cell death in HT-22 cells.