密闭微波消解-冷原子荧光光谱法测定蔬菜中的痕量汞

采用硝酸和过氧化氢体系,密闭微波消解,冷原子荧光光谱法测定蔬菜中的痕量汞,选择0.3g/L硼氢化钾溶液为还原剂,硝酸溶液(1 99)为酸介质。测定结果表明汞浓度在0~1μg/L范围线性良好,相关系数大于0.9990,汞的加标回收率为90.2%~99.6%,测定结果的相对标准偏差均小于4%,检出限为0.0058μg/L。     

不同环境蔬菜中铅污染的研究

用原子吸收分光光度计石墨炉法分析了公路附近的蔬菜中铅的含量。结果表明,蔬菜中铅的含量还与其距离公路的远近有关,蔬菜与空气接触程度也有关;不同种类蔬菜中的铅污染有差异。     

洛阳市郊区叶菜中重金属含量抽样分析及评价

为了研究洛阳市郊区蔬菜中重金属污染状况,采用火焰原子吸收法对郊区李楼乡和孙旗屯乡抽取的叶菜样品中重金属Cu、Zn、Pb、Cd含量进行了测定。结果表明,8个蔬菜样品中Cu含量在0.393 9～0.970 7 mg/kg之间,Zn含量在1.395 0～10.080 0 mg/kg之间,均未超过国家蔬菜卫生限量标准;Pb含量在0.100 0～0.248 6 mg/kg之间,其中有3个样品Pb含量超出国家蔬菜卫生限量标准;Cd含量有5个样品未检出,其余3个样品也不超国标。经用单因子和综合因子污染指数评价,洛阳市郊区叶菜类蔬菜重金属污染大部分已处于警戒级到轻度污染,因此,应加强蔬菜中重金属污染的预防与治理工作。     

Neutral lipids from seeds of <Emphasis Type="Italic">Cercis siliquastrum,Sapium sebiferum</Emphasis>, and <Emphasis Type="Italic">Koelreuteria paniculata</Emphasis>

The chemical composition of neutral lipids from seeds of Cercis siliquastrum, Sapium sebiferum, and Koelreuteria paniculata were studied. Characteristic features of their individual classes were established. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 318–319, July–August, 2007     

毛细管电泳-电化学检测法检测水解植物蛋白调味液中的3-氯-1,2-丙二醇及其应用

运用毛细管电泳-电化学检测法研究了水解植物蛋白液中3-氯-1,2-丙二醇(3-MCPD)含量的测定。探索了3-MCPD检测的最佳电泳条件。以328 μm的铜圆盘电极为工作电极,在电极电位为+0.65 V(参比电极为饱和甘汞电极),检测池缓冲液为0.05 mol/L氢氧化钠,运行缓冲液为30 mmol/L硼砂(pH 9.24)时,3-MCPD能被很好地分离。3-MCPD的线性范围为6.6~200 mg/L,检测限为0.22 mg/L。研究了水解缓冲液的pH值、水解温度、水解时间等因素对3-MCPD水解反应的影响,用毛细管电泳-电化学检测法检测水解反应过程中3-MCPD的含量。结果表明,在pH 8.0的水解缓冲液中,将水解植物蛋白调味液前体于90 ℃条件下恒温加热1 h,能有效地控制3-MCPD的含量在1.0 mg/kg以下,从而达到我国食品安全允许的限量标准。     

GC-MS法测定粮谷及油料中55种有机磷农药残留量

采用ASE-300快速溶剂萃取仪提取样品中农药残留量,提取液经二氯甲烷液-液分配、凝胶色谱柱（GPC）净化,固相萃取柱（活性炭）再净化,浓缩定容后,用气相色谱-质谱仪（GC-MS）测定,外标法定量.采用选择离子检测进行阳性确证.选择玉米、糙米、大豆、花生为实验样品、敌敌畏等55种农药添加水平在0.5～2.00 mg/kg时,该方法回收率为68%～117%;精密度为4.04%～11.76%;方法测定低限为0.005～0.100 mg/kg,各项指标均满足有关要求.     

meso-四-(邻氯对磺酸苯基)卟啉分光光度法测定蔬菜中锌的研究

在溴化十六烷基三甲铵存在下,Zn2 与meso-四-(邻氯对磺酸苯基)卟啉生成配合物。其最大吸收波长为435 nm,表观摩尔吸光系数为1.25×105L.mol-1.cm-1,Zn2 含量在0~0.36μg/mL范围内符合比尔定律。方法用于蔬菜中锌的测定,获得了满意的结果。     

Evaluation of synthesized green carbon catalyst from waste date pits for tertiary butylation of phenol

The present study is intended to adopt a facile method for preparing a sulphonated green carbon catalyst from date pits biomass. Catalyst synthesis involves in situ carbonization and sulphonation and it has been characterized by following techniques such as XRD, SEM, EDX, TEM, FTIR, TGA, and BET. Surface and internal morphology results exhibited that the synthesized sulphonated carbon material possesses a mesoporous structure, while activated carbon possesses a microporous structure. Furthermore, the Fourier transform infrared (FTIR) spectra confirmed the presence of acidic groups (OH, COOH, and SO₃H) in synthesized sulphonated carbon material. Sulphonated carbon material exhibited high acidity (4.7 mmol/g) and good thermal stability. The application of this catalyst for the tertiary butylation of phenol without using any solvent has been investigated. The phenol alkylation reaction showed maximum conversion at reaction condition: temperature (140 °C) with 2 bar (nitrogen gas) pressure with maximum phenol conversion 79.27 wt%, with 68.01% selectivity towards 4TBP+2,4TBP, which is used as an intermediate in antioxidants. The catalyst exhibits comparable catalytic performance up to five reaction cycles. Thus it can be concluded that waste date pits can be successfully employed for green catalyst synthesis and used for reactions involving large molecules.     

Microwave-assisted alkaline digestion combined with microwave-assisted distillation for the determination of iodide and total iodine in edible seaweed by catalytic spectrophotometry

Microwave energy has been novelty applied to speed up a tetramethylammonium hydroxide (TMAH) alkaline digestion of seaweed samples and to assist distillation of iodine from seaweed alkaline digests. Iodide in the alkaline digests from seaweed and distilled iodine, reduced back to iodine in a hydroxylamine hydrochloride solution, was determined by a catalytic spectrophotometric method based on the catalytic effect of iodide on the oxidation of As(III) by Ce(IV) in H₂SO₄/HCl medium (Sandell-Kolthoff reaction). The determination of iodide was directly performed in the alkaline digests, while total iodine was assessed by analyzing the hydroxylamine hydrochloride solution after the distillation process. Microwave-assisted alkaline digestion was performed using 7.5 mL of TMAH and irradiating samples at 670 W for two 5.5 min steps. Microwave-assisted distillation was carried out using 4.0 mL of the alkaline digest and 3 mL of a 2.2 M hydrochloric acid and 0.05% (m/v) sodium nitrite solution, with a microwave power at 670 W for two 90 s steps. The distillate (iodine vapor) was bubbled in 10 mL of a 500 μg mL⁻¹ hydroxylamine hydrochloride solution (accepting solution). The linear calibration ranges were 0.30-20.0 and 0.40-20.0 μg L⁻¹ for iodide determination and total iodine determination, respectively. The limit of detection was 9.2 μg g⁻¹ for iodide and 28.5 μg g⁻¹ for total iodine. Repeatability of the overall procedures, expressed as R.S.D. for 11 determinations, was 2.6% for 196.3 μg g⁻¹ of iodide measured after microwave-assisted alkaline digestion, and 5.8% for 954.3 μg g⁻¹ of total iodine by microwave-assisted alkaline digestion followed by microwave-assisted distillation. Finally, accuracy of the methods was assessed by analyzing the NIST-09 (Sargasso) certified reference material and the methods were applied to the determination of iodide and total iodine in different Atlantic edible seaweed samples with satisfactory results.     

力学可以为农业现代化作贡献

农业现代化提出了许多与力学各个分支都有密切关系的问题．从农田耕作、农业物料性质、农产品烘干、水果和蔬菜生产、农业生物环境、节水灌溉、农业水土资源合理利用和作物生长等方面，介绍了有关的力学问题和目前的研究进展．