The determination of molybdenum in botanical samples

by Su, Lee-ping

(Uncorrected OCR) Ab2tract of thesis enti tIed "'ilie Dtltermination of Molybdenum in Botanical

Samples"

sut~ittedby Lee-ping Su

for the degrge of haster of Science

at the University of Hong Kong in December 1974.

Molybdenum, a biologically active element, which plays an

important role i~1 the nitrogen fixati.oncilld protein synthesis process

i.n plants, is essential. fOr the normal f.:Towth of plants. A dot ~cier-::y

of molybdenum j n plants may lead to the occurrer.ce of physi 01 o{~ical

SYl!,ptO!!lS whioh eventually become lethal if a remedy is not taken tn time.

Tissue analysis of molybdenum.is s..i..gnificant in di.agnosing molybd.enum

status as ,?ell as in providing information on the on'relation -bett-Ieen

crop yield and fertilizer response ?

. , The molybdenum content in a driedbotanj.cal sample f'13.y: b0

j.n the range from a ::e\,; ppm to less than 1 ppm. Investiga.tior. \,?.s ~i

thus made on the current available methods which would. determire

molybdenum dO'Tn to sub-rtd.crogram levels, such as spectrophotometric,

neutron activation, atomic absorption spect:::opnoto!1letric and cataly"dc

meth nds of analysis. Because of the possibil i:tiesoffered by the

recently introduced rarlioaYlalytical techniques, an attnmpt vras alsc

made to study ire use of substoichiometric; isotope dilution anN

isotope exchange reaction in organic :phase conditions.

- ii

....

After a thorough review aYJd experimental investiga~ion of these e~alytical methods, it has been concluded that even though

the sensitivity and feasibility C'.re satisfactory for neutron achvation and catalytic reaction-rate methods, the app1ication of atomic ab'3orption spectrophotometric method ? lith a non-flame atomiza-:'ion technique has the greatest advantages due to its simplicity, specifici ty anr rapidi ty ?

The sensi ti.vity 0:' this method is 0.003 ug/ml of mclybdenum.

The molybJ.enum content in dried Cauliflower leaf tissues ? las f::>und

to QCl 0.458 ?0.015 }J.g/g with a :;:elative standard deviati.on of ;t 3.2% for five measurements ?

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