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Internal standard. A solution was prepared by mixing 5.00mLof unknown elementXwith2.00mLof solution containingrole="math" localid="1654777035083" 4.13μgof standard elementSper millilitre, and diluting to10.0mL. The signal ratio in atomic absorption spectrometry was (signal fromX)/ (signal fromS)=0.808. In a separate experiment, with equal concentrations ofXandS, (signal fromX)/signal fromS)=1.31. Find the concentration ofXin the unknown.

Short Answer

Expert verified

The concentration ofXin the unknown has to be calculated as1.02μg/mL

Step by step solution

01

Concept used

Response factor:

In chromatography, a response factor is well-defined as the proportion between the concentration of a compound being analyzed and the response of the detector to that compound.signalfromanalyteconcentrationofanalyte=Fsignalfromstandardconcentrationofstandard

AxX=FAsS

where,

Axsignal from analyte

Xconcentration of analyte

Fresponse factor

Assignal from standard

SConcentration of standard

02

Calculation of concentration of unknown element

A solution was prepared by mixing 5.00MLof unknown element Xwith 2.00mLof solution.

It has 4.13μ²µof standard element S/millilitre and it is diluted to 10.0mL

Using standard mixture to determine the response factor.

We knew that X=Sand the ratio of signals Ax/Asis1.31

Mixture of unknown plus standard, the concentration of Sis

S=4.13μ²µ/mL2.0010.0=0.826μ²µ/mL

For the unknown mixture F=Ax/AsX/S

role="math" localid="1654931185928" 1.31=0.808X/0.826X=0.509μ²µ/mL

The concentration of Xdiluted from 5.00 to 1.00mLin the mixture with S,

The original concentration ofX=1.05.00.509μ²µ/mL=1.02μ²µ/mL

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A solution containing3.47mMX(analyte) and1.72mMS(standard) gave peak areas of3473and 10222,respectively, in a chromatographic analysis. Then1.00mLof 8.47mMSwas added to5.00mLof unknownX,and the mixture was diluted to10.00mL. This solution gave peak areas of5428and4431forXandS, respectively.

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Standard addition graph. Tooth enamel consists mainly of the mineral calcium hydroxyapatite,C10PA46OH2. Trace elements in teeth of archeological specimens provide anthropologists with clues about diet and diseases of ancient people. Students at Hamline University used atomic absorption spectroscopy to measure strontium in enamel from extracted wisdom teeth. Solutions were prepared with a constant total volume of 10.0mLcontaining role="math" localid="1667792217398" 0.750mgof dissolved tooth enamel plus variable concentrations of added Sr.

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