Determination of Potassium Iodate in Edible Salt by Potassium

Iodide-Iodine-Starch System

Xinrong Wen

1,2,*

and Changqing Tu

1,2

School of Chemistry and Environment, Jiaying University, Meizhou, Guangdong 514015, China

Guangdong Provincial Key Laboratory of Conservation and Precision Utilization of Characteristic Agricultural Resources

in Mountainous Areas, Jiaying University, Meizhou, Guangdong 514015, China

Keywords: Spectrophotometry, Potassium Iodate, Potassium Iodide, Edible Salt.

Abstract:

In acidic medium, ki can react with kio

to form i

, then i

and starch form i

-starch blue complex with a

maximum absorption wavelength of 596 nm. Beer's law is obeyed between the kio

content and the absorbance

of i

-starch blue complex. Base on this, the kio

content can be determined indirectly. A novel method for the

determination of potassium iodate in edible salt by potassium iodide-iodine-starch system has been

established. The various effect factors on the determination of iodide by potassium iodide-iodine-starch

system are investigated in detail. Under optimal conditions, when the mass concentration of kio

0.4000~1.280 µg/ml, the linear regression equation is a=-0.0649+0.04702c (µg/ml) with the linear correlation

coefficient is 0.9992. this proposed method had been successfully applied to determinate kio

in edible salt,

and the results agree well with those by standard method.

1 INTRODUCTION

Iodine is one of the essential microelements for

humans. It can enhance the basic metabolism and

promote the growth and development of human

body. Both iodine deficiency and iodine excess do

harm to the human body. Iodine deficiency can cause

an endemic goiter and potential damage to children's

intellectual growth, and iodine excess can lead to

hypothyroidism, thyroid enlargement and other

clinical manifestations. Eating iodized salt is the most

important and effective way to prevent iodine

deficiency disease. Potassium iodiate is usually added

to the edible salt, which is the iodized salt. Eating

iodized salt can achieve the effect of iodine

supplement. Thus, the determination of iodine

content in iodized salt has great practical significance.

So far, the determination methods for potassium

iodinate in salt are mainly included titration

(Mohammad, 2020), spectrophotometry

(Gavrilenko, 2019), emission spectrometry (Yu,

2013), flow-injection (Kuznetsov, 2007), ICP-OES

(Sager, 2019), CE-ICP-MS (Chen, 2007) HPLC

(Manju, 2010) and so on.

In this paper, a novel method for the

determination of potassium iodate in edible salt by

potassium iodide-iodine-starch system is reported. In

acidic medium, I

reacts with KIO

to form I

, then I

and starch form I

-starch blue complex with a

maximum absorption wavelength of 596 nm. There is

a good linear relationship between the absorbance of

-starch blue complex and the KIO

dosage, the

linear equation is A=-0.0649+0.04702C(µg/mL)

within the range of 0.4000~1.280 µg/mL KIO

concentration. So, by measuring the absorbance of I

starch blue complex, the content of KIO

can be

determined indirectly. This proposed method has

been applied to determinate of KIO

in edible salt

with satisfactory result.

2 EXPERIMENTAL

2.1 Equipment and Reagents

UV-2401 UV-visible spectrophotometer (The

Shimadzu Corporation, japan); 723S

spectrophotometer (Shanghai Precision & Scientific

Instrument Co,. Ltd ).

KIO

solution: 10.00 μg·mL

-1

, a 1.000 mg·mL

-1

potassium iodiate solution is prepared and then

Wen, X. and Tu, C.

Determination of Potassium Iodate in Edible Salt by Potassium Iodide-Iodine-Starch System.

DOI: 10.5220/0012012100003633

In Proceedings of the 4th International Conference on Biotechnology and Biomedicine (ICBB 2022), pages 21-26

ISBN: 978-989-758-637-8

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

diluted to 10.00 µg·mL

-1

. KI solution: 1.000 g·L

-1

solution: 5.0 mol·L

-1

. Starch solution:5.0 g·L

-1

All reagents are of analytical reagent grade.

Bidistilled water is used.

2.2 Method

KI solution 3.00 mL, starch solution 3.00 mL, H

solution 1.50 mL, a certain volume of KIO

solution

or edible salt sample solution are added into a 25 mL

volumetric flask. The solution is diluted to the mark

with bidistilled water, mixed well and placed at room

temperature for 40 minutes in the dark. The

absorbance of I

-starch blue complex is measured at

596 nm against the reagent blank.

3 RESULTS AND DISCUSSION

3.1 Maximum Absorption Wavelength

In 500～700 nm, the absorption spectrum of I

-starch

blue complex is obtained using UV-2401 UV-visible

spectrophotometer (Fig. 1). Fig. 1 show that the

maximum absorption wavelength of I

-starch blue

complex is 596 nm.

KIO

:2.00 mL; KI:2.00 mL; H

:3.00 mL; starch:2.00 mL; reaction time:20 min.

Figure 1: Absorption spectrum.

3.2 Reaction Temperature

The effect of reaction temperature is seen in table 1.

We can sen from table 1 that the absorbance of I

starch blue complex keep constantly decreasing with

the increase of reaction temperature. Hereby, the

room temperature is used.

Table 1: The effect of reaction temperature on the absorbance.

Temperature /℃

room

tem

erature

30 35 40

Absorbance 0.380 0.375 0.374 0.372

Temperature /℃ 45 50 55 60

Absorbance 0.368 0.364 0.353 0.342

Experimental conditions: KIO

:2.00 mL; KI:2.00

mL; H

:3.00 mL; starch:2.00 mL; reaction

time:15 min.

3.3 Reaction Time

The effect of the reaction time is showed in Fig. 2.

It is found that the absorbance of I

-starch blue

complex gradually increased with the reaction time, and

the absorbance of I

-starch blue complex reaches

greatest when the reaction time is 35 minutes or more.

So, 40 minute is selected.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

500 550 600 650 700

λ/n

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KI:2.00mL; H

:3.00mL; KIO

:2.00mL; starch:2.00mL.

Figure 2: Effect of the reaction time.

3.4 KI Solution Dosage

The effect of KI solution dosage can be seen in fig. 3.

The results showed that as the amount of KI increases,

the absorbance of I

-starch blue complex also

gradually increases. The absorbance of I

-starch blue

complex reaches the maximum value when KI

solution dosage is 2.50 mL. Thereafter, the

absorbance of I

-starch blue is basicly stable as KI

dosage increases. Thus, 3.00 mL KI solution is

chosed.

:3.00mL; KIO

:2.00mL; starch:2.00mL; reaction time:40 min.

Figure 3: Effect of KI solution dosage.

3.5 H

Solution Dosage

The effect of H

solution dosage is showed in Fig.

4. The results show that the absorbance of I

-starch

blue complex gradually increases with the amount of

increases. The absorbances of I

-starch blue

complex are essentially constant when the H

solution dosage is 1.00～2.00 mL. Hence, 1.50 mL

solution is used.

0.10

0.15

0.20

0.25

0.30

0.35

5 152535455565758595105115

min

0.00

0.10

0.20

0.30

0.40

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

V(KI)/mL

Determination of Potassium Iodate in Edible Salt by Potassium Iodide-Iodine-Starch System

KI:3.00mL; KIO

:2.00mL; starch:2.00mL; reaction time:40 min.

Figure 4: Effect of H3PO4 solution dosage.

3.6 Starch Solution Dosage

The effect of starch solution dosage is showed in

Table 2. The experimental results show that the

absorbance of I

-starch blue complex increase with the

increase of starch solution dosage. The absorbance of

-starch blue complex is maintained at stable values

when the starch solution dosage is 2.50 mL or more.

Therefore, the starch solution dosage is chosen as

3.00 mL.

Table 2: The effect of starch solution dosage on the absorbance.

Starch solution dosage

/mL

0.50 1.00 1.50 2.00

Absorbance 0.292 0.383 0.395 0.407

Starch solution dosage

/mL

2.50 3.00 4.00 5.00

Absorbance 0.413 0.415 0.413 0.414

Experimental conditions: KI:3.00 mL;

:1.50 mL; KIO

:2.00mL; reaction time:40 min.

3.7 Calibration Curve

Under the optimum conditions, a series of

determination solutions with different KIO

concentrations are prepared, then the absorbances of

these solutions are measured at 596 nm against the

reagent blank. Using concentration as the abscissa

and absorbance as the ordinate, the calibration curve

(Fig. 5) is obtained. In the range of 0.4000-1.280

μg/mL KIO

, a good linear relationship between the

KIO

concentration and the absorbance of I

-starch

blue complex, the linear equation is A=-

0.0649+0.4702C(μg/mL) and the correlation

coefﬁcient is 0.9992.

0.20

0.25

0.30

0.35

0.40

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

V( H

)/mL

ICBB 2022 - International Conference on Biotechnology and Biomedicine

KI:3.00 mL; H

:1.50 mL; starch:3.00 mL; reaction time:40 min.

Figure 5: Calibration curve.

3.8 Sample Analysis

25.0000 g edible salt sample is weighed and dissolved

in proper amounts of bidistilled water, then it is

transferred into a 250 mL volumetric flask and

diluted to the mark with bidistilled water, shaked

well. This is the edible salt sample solution.

According to the experimental method, 5.00 mL

edible salt sample solution is added, then the

absorbance of I

-starch blue complex is determined,

and the content of KIO

is calculated. Meanwhile, the

recovery tests of standard addition are performed and

the content of KIO

is determined by standard method.

The results as show in Table 3.

Table 3: The content of KIO3 in edible salt.

Sample

Proposed

method

(μg·g

-1

)

RSD

(%)

Standard

method

(GB

26402-

2011)

(μg·g

-1

)

Added

(μg·mL

-1

)

Recovered

(μg·mL

-1

)

Recovery

yield

(%)

Natural sea

salt

37.61 0.2 38.82

0.08000

0.1600

0.07614

0.1642

95.2

102.6

Low sodium

salt

36.06 0.6 37.15

0.08000

0.1600

0.07571

0.1510

94.6

94.4

Well cooked

salt

34.40 0.3 35.45

0.08000

0.1600

0.07512

0.1540

93.9

96.2

From Table 3, we can seen that the content of

KIO

in edible salt by this proposed method is

consistent with the standard method, and the recovery

yields are 93.9%～102.6%.

4 CONCLUSION

A novel method for the determination of KIO

edible salt by potassium iodide-iodine-starch system

has been reported in this paper. This method has been

successfully applied to the determination the content

of KIO

in different edible salt with satisfactory

results. It is obvious that the determination the content

of KIO

by potassium iodide-iodine-starch system

has certain practical significance and foreground of

application.

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Determination of Potassium Iodate in Edible Salt by Potassium Iodide-Iodine-Starch System

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