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Determination of Total Boron in

Soil by the Curcumin-Acetic Acid

Method After Extraction with 2-

Ethyl-1,3-HexanediolHidekazu Yamada

a& Tomoo Hattori

a

aDepartment of Agricultural Chemistry. Faculty of

Agriculture , Kyoto Prefectural University , Shimogamo ,

Kyoto , 606 , Japan

Published online: 30 Oct 2012.

To cite this article:Hidekazu Yamada & Tomoo Hattori (1986) Determination of Total Boron

in Soil by the Curcumin-Acetic Acid Method After Extraction with 2-Ethyl-1,3-Hexanediol, SoilScience and Plant Nutrition, 32:1, 135-139, DOI: 10.1080/00380768.1986.10557487

To link to this article: http://dx.doi.org/10.1080/00380768.1986.10557487

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Short Communication

oil Set. Plant Nutr., 3 1), 135-139, 1986

DETERMINATION OF TOTAL BORON

IN

SOIL BY

THE CURCUMIN-ACETIC ACID METHOD AFTER

EXTRACTION WITH 2-ETHYL-l,3-HEXANEDIOL

Hidekazu Y M D and Tomoo HATTORI

Department o Agricultural Chemistry. Faculty o Agriculture.

Kyoto Prefectural University. Shimogamo. Kyoto, 606 Japan

Received February 12, 1985

The curcumin-acetic acid method after extraction of boron into chloroform or

methyl isobutyl ketone with 2-ethyl-I,3-hexanediol EHD) has been used for the deter

mination of boron in fertilizers

1)

and foods 2). The extraction with EHD is so

selective

to

boron that it appears to be a suitable procedure for the separation of boron

from the solution of soil digests. The curcumin-acetic acid method is based on the

fact that boron in the organic phase reacts with curcumin in an acetic acid-concen

trated sulfuric acid medium, and this method

is

simpler than the conventional curcumin

method that requires evaporation

to

dryness

of

the reagents.

To apply this technique to the determination of boron in soil

we

evaluated several

analytical conditions for the extraction of boron and color development in the cur

cumin-acetic acid method.

Experimental

J Chemicals and reagents.

Extracting solvent: dissolve

200

ml of EHD into

chloroform, dilute to 1,000 ml with chloroform. Curcumin-acetic acid solution: dis

solve 0.5 g of curcumin into

250

ml of hot glacial acetic acid 60-70C) in a polyethylene

bottle. This reagent solution stored in a dark polyethylene bottle

is

stable for

at

least

2 months. Standard boron solution: dissolve 2.858 g of boric acid HallOs) in water,

dilute

to

500 mI.

This stock solution contains I mg

of

boron per ml and

is

diluted

to prepare the working solutions before use.

2 Apparatus.

Absorbance was read with a Hitachi

100 60

type spectrophotom

eter using 1 cm glass cells. Phase separating filter paper, Whatman IPS, was used

for the separation of the aqueous and organic phases.

3 Procedure.

Fuse 0.2 g of fine-powdered soil sample with I.S g of sodium

peroxide,

Na

2

0

2

, in a

35

ml nickel crucible for

20

min in an electric furnace

at

550C.

Cool and place the crucible in a

100

ml polytetrafluoroethylene PTFE, Tefion) beaker,

and add 5 ml of water in the crucible. Place a polyethylene-made watch glass on the

Key Words: boron, 2-ethyl-l,3-hexanediol, curcumin.

135

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136 H. YAMADA and T. HATTORI

beaker and allow to stand for 30 min to digest the melted product. Transfer the cru

cible contents into the PTFE beaker. Wash the crucible several times with water and

add the washings to the beaker. Acidify the solution in the beaker by gradual addition

o

approximately 4 ml

o

1 2)H

2

SO, and heat the beaker on a hot plate. After

cooling, transfer the solution in the PTFE beaker into the 50 ml polyethylene bottle

with a narrow mouth and dilute it to

25 mt

with water. Add 4

ml o

extracting solvent

in the bottle and shake it for 3 min. Filter the contents in the bottle with a phase

separating filter paper to separate the organic phase from the aqueous phase. To 1

ml o the filtrate (organic phase) add 1 ml o curcumin-acetic acid solution and 0.25

ml o concentrated sulfuric acid. Allow the mixture to stand for 30 min with occa

sional shaking and dilute it to 50 ml with 95 ethanol. After 30 min, measure the

absorbance at 550 nm with reagent blank as a reference, and determine the concentra

tion o boron with reference to a calibration curve prepared at the same time.

esults and dis ussion

Elemental analysis o soils necessitates their decomposition into soluble forms by

acid digestion

or

fusion with various fiuxes. As boron volatilizes easily from the acidic

aqueous solution upon heating, alkali fusion is suitable for boron analysis o soil.

Alkali fusion with sodium peroxide as a fusion fiux was chosen. Soil sample could be

completely decomposed with the addition o an amount o sodium peroxide o more

than six times the weight

o

the soil sample. A larger flux/sample ratio

is

desirable

so that both the temperature and time o fusion can be kept to a minimum. But when

sodium peroxide was added in excess, the amount o sulfuric acid to acidify the solu

tion after fusion increased and the corrosion

o

the nickel crucible was accelerated.

Therefore, 1.5 g o sodium peroxide was mixed with 200 mg o soil and the mixture

was fused for 20 min at

550C.

Extraction conditions o boron with EHD and conditions for color development

o

the boron-curcumin complex in an acetic acid-concentrated sulfuric acid medium

were also studied. The results obtained generally agreed well with the results reported

by

AOAZZI

3)

and by

UENO

and

TODA

(1);

thus, this paper described a

few

improve

ments in the method.

t

is well known that a small amount o water contaminating the organic phase

affects the color development

o

the boron-curcumin complex: with only 50 ,ul

o

water

present in 1

ml o

organic phase, the absorbance was about 85

o

that without water

in the organic phase. To remove the interference from water, the filtration through

a dry filter paper or the addition o a drying agent, such as sodium sulfate anhydride

or propionic anhydride, has been tested. But when a phase separating filter paper

was used, the phase separation and the dehydration

o

the organic phase could be

achieved at the same time.

The volume ratio

o

an aqueous to an organic phase is

o

importance in solvent

extraction, because the recovery by extraction

is

closely related to the value o the

ratio. A higher ratio is desirable as a means of concentrating boron, hence lowering

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Determination of Boron in Soil

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138

H. YAMADA and T. HATTORI

Table 1. Reproducibility and recovery of added boron with the proposed method.

Sample Sample taken (g)

Soil A 0.200

0.200

SoilB

0.100

O

100

Boron added

(Jlg)

as B

in the form

of

HaBOs

o

5.0

o

5.0

Boron found Jlg)

7.36, 7.18, 7.04, 7.48

X=7.27 36.3 ppm in soil)

S=0.194, CV=2.67%

12. 1,

12.3,

12. 1,

12.2

X=12.2

S=0.0957, CV=0.79%

Recovery=98.3%

2.14, 2.20, 2.24, 2.36

X=2.24

(22.4 ppm in soil)

S=0.0929, CV=4.16%

7.24, 7.12

X=7.18 Recovery=98.9%

X

mean; S, standard deviation; CV, coefficient of variation. Soil A: collected from the plow layer

of

a paddy field

at

Kyoto Prefectural University. Soil B: collected from the surface

of

virgin land formed

on serpentinite

at

Ooe-cho in Kyoto Prefecture.

Table 2. Analytical results

of

boron in reference samples.

Boron concentration Mean

Reported value (4, 5

(ppm)

(ppm)

(ppm)

eference sample

Soil SO-I 20.9, 24.1, 22.6

22.5

204

SO-3

29.7,

28.9,25.9

28.2

227

SO-4

44.7, 47.9, 46.0

46.2

4310

Rock

JB-1

8.8, 10.1, 10.9

9.9

JO-l

5.9,

6.5,

6.0

6.1 8.2*

Arithmetic mean

of

reported values (5).

(basalt) and JG- (granodiorite) from the Geological Survey of Japan were determined

to evaluate the accuracy of the method. The boron contents obtained in this study

were in good agreement with the reported values

4, 5)

for the reference samples (Table

2).

REFERENCES

1) UENO, Y. and TODA, T., Determination

of

boron in fertilizer by using curcumin-acetic acid,

iken

Kaiho 29, 14-20 1976) (in Japanese)

2)

FUKUI,

S.,

HIRAYAMA,

T.,

NOHARA,

M.,

KOBAYASHI, K., KAWAMURA,

T.,

IWAIDA,

M., lTo, Y.,

OOAWA, S., KAKIUCHI, Y.,

YAMAZAKI,

H., and ONO, N., Colorimetric determination of boric acid

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Determination of Boron in Soil

139

n

food by chelate extraction with 2-ethyl-l,3-hexanediol

and

by using protonated curcumin,

isei

Kagaku,

29, 323-328 1983) in Japanese)

J

AOAZZI E.J., Extraction flame photometric determination

of

boron,

Anal. Chem.,

39, 233-235 1967)

4) STEaM, H.P. Certified reference materials,

CANMET

Canada Centre

of

Mineral andEnergy Tech

nology) Report 80-6E 1980)

S

ANoo,

A. KURASAWA

H

OHMORI,

T., and TAKEOA E., 1974 compilation

of

data on the

OSJ

geochemical reference samples JG-l granodiorite

and

JB-l basalt,

Geochem. J.

8, 175-192 1974)

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