共查询到20条相似文献，搜索用时 62 毫秒
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实验采用原子吸收光谱法测定荸荠、莲藕、莲子中的铁、锌、钙的含量,在样品处理过程中,采用湿法消化法和干法灰化法这两种处理方法进行多元素的消解,并对这两种样品处理方法的操作效果及测定结果进行比较,在本实验的条件下,铁的线性关系是0．1～5．0 mg/L,检出限为0．19 mg/L;锌的线性关系是0．2～1．0 mg/L,检出限为0．04 mg/L;钙的线性关系是0．5～14．0 mg/L,检出限为0．22 mg/L．回收率在90．6%～103．2%范围内． 相似文献
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建立了动物源性食品中9种喹诺酮类药物残留量的液相色谱-电喷雾串联四极杆质谱测定方法.样品经阳离子交换固相萃取柱净化后,采用多反应监测(MRM)模式,进行LC-MS/MS分析.方法检出限均为0.05μg/kg,在0.05～50μg/kg添加水平范围内,喹诺酮类药物回收率为65.8%～94.6%,相对标准偏差为5.3%～9.1%. 相似文献
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《实验室研究与探索》2010,(11)
环境样品有机氯农残的检测要求准确度高、检出限低,并且对于临界值附近的检测数据要求稳定性好、可信度高。为了满足以上技术要求,研究了溶剂提取、PTV-GC/MS程序升温大体积进样-气质联用选择性离子监测SIM模式、内标法定量检测环境样品土壤和水中痕量有机氯农残的方法。PTV进样技术最大限度地降低了有机氯农药中不稳定化合物的热分解(如DDT,Endrin),同时进样量比GC-ECD、GC-MS增大了10倍。GC/MS定性准确度高、目标物分离度好、选择性强、灵敏度高。方法检出限MDL水样可达到0.01μg/L,土壤样品可达到0.001～0.003μg/g;水样和土壤样品20种有机氯农药的加标回收率均在65%～105%;精密度测定相对标准偏差RSD在3.0%～25%。 相似文献
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对惰性熔融红外吸收法测定高氢钛样品中氧含量的分析方法进行了研究,确定了最佳分析参数。通过步进式升温模式将样品中的大部分氢提前释放出来,避免了在高温条件下甲烷的产生。确定高温段最佳分析功率为4. 8 k W;最佳样品称样量为0. 04～0. 08 g;助熔剂采用镍囊镍粒组合形式;氧最短分析时间为140 s,比较器水平设为1%。使用标样502-879建立单标样校准曲线,得到回归方程y=0. 7123 85x。通过对高氢钛样品的多次平行试验和加标回收试验对测定方法的可行性进行了分析,测定方法的相对标准偏差分别为2. 57%,加标回收率在95%～107%,表明该测定方法可以准确测定高氢钛样品中的氧含量。 相似文献
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目的 :建立测定益母草中多糖含量的方法。方法 :采用水杨酸法测定还原性单糖的含量和水解后的总糖含量 ,从而间接测出益母草中的多糖含量。结果 :糖浓度 5～ 4 0ug在范围内呈现良好的线性关系 ,益母草中多糖含量为 (31.16± 0 .2 3) % ,平均回收率为 98.92 %。RSD=2 .2 5 %。结论 :该方法简便、快速、准确 ,并且消除了样品中还原性单糖对多糖含量测定的影响 ,该方法特别适合于含有单糖的样品中多糖的含量测定。 相似文献
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本文利用在酸性条件下亚硝酸盐对硫酸铁铵 硫氰酸钾体系的褪色效应 ,建立了褪色光度法测定果蔬中亚硝酸盐的方法 ,探索了测定的最佳操作条件。最大吸收波长为45 2nm ,表观摩尔吸光系数为 3.2 3× 1 0 3L·mol- 1 ·cm- 1 ,亚硝酸钠质量浓度在 0～ 4μg/ 1 0ml范围内 ,符合比耳定律 ,回收率在 96%～ 1 0 2 %之间。用于样品中亚硝酸盐的测定 ,结果满意。 相似文献
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分析松针中16种有机磷农药和15种有机氯农药的残留量.通过对提取方法的比较,分析检测方法的优点与验证效果.在实验中,样品先经乙腈提取,再进行QuEChERS方法前处理,然后在多反应离子监测(MRM)模式下,通过气相色谱-串联质谱法(GC-MS/MS)对样品进行检测分析和外标法定量.结果表明：在该条件下,各种农药线性关系良好,线性相关系数大于0.98,精密度良好,RSD值在8.71%以内;当样品加标含量为2～10μg/L时,各种农药的平均回收率在68.48%～181.3%之间,RSD值在49.78%以下,方法的检测限低于0.005 mg/kg.该实验方法灵敏度高、准确性好,适用于林业多种有机磷和有机氯农药的残留检测. 相似文献
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常征 《安徽科技学院学报》2003,17(3):253-256
采用溴酸钾 溴化钾消解法 ,通过对消解时间、消解温度及盐酸羟胺加入量的研究 ,得出较为适合的实验条件 ,可以快速测定水样中的汞 ,实际样品分析结果满意 ,RSD % =0 .76%～ 2 .7% ,CV % =92 .8%～ 1 0 1 .3%。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献