问题 问答题 简答题

丁二酮肟分光光度法测定水中镍时,干扰因素有哪些?如何消除?

答案

参考答案:

铜及钴等金属离子易与丁二酮肟生成络合物,不溶于氨水的铁、铝及铬都产生干扰,影响测定结果。柠檬酸铵,可消除二价铅、镁、锌、钙、六价铬及三价铝等的干扰;Na2EDTA溶液,可消除铁、铜、锰及钴的影响。当铜及钴浓度过大时,可采用丁二酮肟—正丁醇萃取分离除去。氰化物干扰测定,可在测定前加入次氯酸钠和硝酸加热除去。

阅读理解

       Parents and doctors have the same worry over especially low birthweight newborns.1.________A trend has therefore developed to make special formulas (配方) of extra nutrients and proteinrich foods for these tiny babies.Unfortunately,a British study has found that this practice could have negative long term effects,such as high blood pressure in adulthood.

       Between 1993 and 1995,Atul Singhal of the Institute of Child Health and his colleagues researched 299 fullterm newborns,each of whom weighed very little for their age.The babies' moms had decided not to breastfeed (用母乳喂养).

       2.________The rest received a formula with more nutrients and 28 percent more protein than the standard formula.The growth of all of these children was compared to that of 175 similarly low birthweight babies whose mothers had chosen to breastfeed their children for their first 9 months.3.________They found 83 babies from the normalformula group,70 babies from the extraformula group,and 95 babies from the breast fed group.4.________According to the latest data,children who had received the extra formula had significantly higher blood pressures than those in the other two groups.

      Seven human tests have indeed shown that when infants are overfed before being stopped breastfeeding,they have an increased possibility to become fat as youngsters.

      No matter how big a child is at birth,he or she will probably reach the same adult height no matter how quickly the baby grows.But reaching one's adult size at a slowtomoderate speed may have a lot of benefits,as Singhal says.5.________

A.Half of these children were given a normal infant (幼儿) formula for 9 months.

B.When they grow up,they might have high blood pressure.

C.These babies have very little energy because they are so small.

D.Six to eight years later,the researchers gave the children a series of measurements and tests.

E.The results were quite surprising.

F.Tiny babies will grow much slower if they are not specially fed.

G.His advice to parents:Be patient.Don't rush a child's growth.

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