Spectrophotometric Determination of Kelthane in Environmental Samples

doi:10.4236/ajac.2011.26083

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American Journal of Anal yt ical Chemistry, 2011, 2, 726-730

doi:10.4236/ajac.2011.26083 Published Online October 2011 (http://www.SciRP.org/journal/ajac)

Spectrophotometric Determination of Kelthane in

Environmental Samples

Etesh K. Janghel1, Y. Pervez2

1Department of Applied Chemistry, Ashoka Institute of Technology & Management, Gram-Torankatta, Post-Somni,

Rajnandgaon, India

2 Department of Applied Chemistry, Chhatrapati Shivaji Institute of Technology, Durg, India

E-mail: [email protected]

Received September 27, 2010; revised January 10, 2011; accepted January 20, 2011

Abstract

Sensitive spectrophotometric method for determination of kelthane in sub parts per million level is described,

which is based on Fujiwara reaction. Kelthane on alkaline hydrolysis gives chloroform, which can be reacted

with pyridine to produce red colour. The colour is discharged by addition of glacial acetic acid. Then Ben-

zidine (4,4’-Bianiline) reagent is added due to which a yellowish-red colour is formed which has an absorp-

tion maximum at 490nm. Beer’s law is obeyed in the range of 3.3 - 26.0 µg (0.13 - 1.04 ppm) of Kelthane

per 25ml of final solution. The molar absorptivity and Sandell’s sensitivity were found to be 4.32 × 105

L·mol–1·cm–1 and 0.022 µg·cm–2 respectively. The method is found to be free from interferences of other or-

ganochlorine pesticides and various co-pollutants and can be successfully applied for the determination of

kelthane in environmental samples.

Keywords: Spectrophotometry, Kelthane, Acaricide, Benzidine, Environmental Samples

1. Introduction

Kelthane is a well known acaricide of organochlorine

group of pesticides, chemically it is known as 4-4’di-

chloro-alpha trichloromethyl benzhydrol [1] Kelthane

appears to be effective against a wide range of mite spe-

cies and is a well known miticide. It is also effective

against tetrachid, mites, cydamen, broad, mites, Euro-

pean red spider, apple-rust, cherry-rust, tomato-rust, and

various other fruits and vegetable rusts [2].

Field studies indicate that dicofol persists in soil for at

least four years after application. The residue of kelthane

accumulates in rotational crops. Due to very long persis-

tency of residue of this material, the use of kelthane is

recommended on slow growing crops, i.e. citrus fruits. It

has been proved that kelthane is a sever irritant [3,4].

The National Cancer Institute suggests the possibility of

kelthane as oncogen. The toxic effect of kelthane shows

general weakness, comma, affects sex hormones, inhibi-

tion of aromatose activity and death in animal. It is a

contact herbicide with initial toxicity. It has a moderate

acute oral toxicity. The oral LD50 in rat is 809 mg/kg and

1870 mg/kg body weights for rabbit [2]. The tolerance

level of dicofol in vegetable is 1 mg/kg [5-7].

Several instrumental techniques i.e. GLC with Elec-

tron Capture detector [8], Voltammery [9] Neutron acti-

vation analysis [10], Gas chromatography [11], Liquid

chromatography [12], matrix solid—phase dispersion

[13], solid—phase extraction [14], and Spectrophotome-

try [15-18] are available in literature, but most of these

techniques are costly and require trained staff. Spectro-

photometry is a simple, sensitive rapid and versatile

technique for quick determination of analyte. A few

spectrophotometric methods based on the hydrolysis of

kelthane to chloroform and determination of chloroform

by Fujiwara method [15-18] are available, but all these

methods require specially constructed apparatus and

have poor sensitivity than the present method.

In the present a simple and more sensitive method is

developed for the determination of kelthane. The reagent

used in the present method is benzidine which increases

sensitivity of the Fujiwara reaction. The method has been

successfully applied for the determination of kelthane in

environmental samples.

2. Experimental

Apparatus. A Systronics spectrophotometer 104 with 1

E. K. JANGHEL ET AL.727

cm matched quartz cell was used for all spectral meas-

urement. A Systronics pH meter model 335 was used for

pH measurement.

Reagents. All the reagents were of A.R./G.R.grade

and double distilled deionised water was used throughout

the study.

Stock solution of kelthane. (Tropical Agro system In-

dia Ltd.) 1 mg/ml solution or kelthane was prepared in

alcohol. Working standards were prepared by appropriate

dilution of the stock solution with alcohol.

Benzidine. (Merck, Germany) 1% solution of ben-

zidine in 25% alcohol was prepared.

Sodium hydroxide. 5 M aqueous solutions.

Hydrochloric aci d. 10 M aqueous solution.

Pyridine, glacial acetic acid, n-hexane and ether sol-

vent.

Procedure. An aliquot containing 2.0 - 30 µg of

kelthane was taken in a 25 ml-graduated tube. The solu-

tion was evaporated off up to 0.5 ml on a water bath. To

this 1ml of pyridine and 2 ml of 5 M NaOH were added

and thoroughly shaken. The contents were kept in water

bath at 70˚C - 75˚C for ~3 min. and shaken time to time.

The yellowish-red colour solution obtained was cooled in

ice-cold water bath and then decolourised with 2 ml gla-

cial acetic acid. To this yellow colour solution 2 ml of

1% benzidine and 1 ml of 10 M HCl were added and the

content was allowed to stand for 10 minute. The volume

was made up to the mark and the absorbance of the yel-

lowish-red coloured dye was measured at 490 nm against

a reagent blank.

Colour Reaction of Kel thane

The reaction was supposed to take place in four steps.

1) Kelthane was hydrolyzed by Sodium hydroxide to

generate chloroform (I) and 4, 4-dichlorobenzophenone.

2) In this step chloroform reacted with pyridine in al-

kaline medium to form Schiff’s base of glutaconic alde-

hyde (II).

3) In the third step, by addition of glacial acetic acid,

the pink colour of Schiff’s base of glutaconic aldehyde

was converted in to the yellow coloured glutaconic al-

dehyde (III).

4) Yellow coloured Glutaconic aldehyde formed a pur-

ple red coloured polymethine dye (IV) with benzidine

reagent in the fourth step (Mechanism 1).

3. Results and Discussion

Spectral Characteristic. All the spectral measurements

were carried out against, reagent blank which showed

negligible absorbance at 490 nm (Figure 1).

Adherence of Beer’s Law, Molar absorptivity, and

Sandell’s sensitivity. Beer’s law was obeyed over a con-

Mechanism 1

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

440460 480500 520540 560

W a ve l e ngth of nm

Absorb an ce, 490n m

Figure 1. Absorption curve of kelthane.

centration range of 2.0 µg - 30.0 µg (Figure 2) of

kelthane per 25 ml of final solution (0.13 - 1.04 ppm).

Molar absorptivity and Sandell’s sensitivity were found

to be 4.32 × 105 l·mol–1cm–1 and 0.022 µg·cm–2 respec-

tively.

Effect of reagent concentration. 1 ml of pyridine and

2 ml of 5 M NaOH were required for maximum colour

intensity. Excess of NaOH made the solution slightly

turbid. 2 mL of acetic is necessary for decolourisation of

the red colour. Excess amount, however, does not affect the

reaction. A minimum of 2 ml of benzidine was required

E. K. JANGHEL ET AL.

728

0.2

0.4

0.6

0.8

1.2

0102030

Conce ntration of Kel tha ne in µg pe r 25 ml

Absorbance

Figure 2. Calibration curve of kelthane.

for maximum colour intensity. Excess amount of ben-

zidine decreases the colour intensity (Figure 3).

Effect of time and temperature. It was observed that

heating the reaction mixture for a ~3 minutes in a water

bath at 70˚C - 75˚C gave maximum and constant absorb-

ance value. The purple red colour dye was found to be

stable for ~10 min. and thereafter showed gradual de-

crease in intensity with increasing time. (Figures 4 and 5).

Effect of pH. Maximum absorbance of the dye was ob-

served when pH of the final solution was between 3 and 4.

Precision. The precision of the method was checked

by seven replicate analysis containing 25 µg kelthane per

10 ml of final solution. The standard deviation and rela-

tive standard deviation were found to be ±0.0033 and ±

0.53% respectively.

Effect of foreign species. The validity of the method

was assessed by investigating the effect of various co

pollutants and polyhalogenated compounds on the de-

termination of Kelthane by the developed method, by

adding a known amount of these compounds to a solu-

tion containing 25.0 µg Kelthane per 25 ml of the final

solution. The tolerance limit in ppm of interfering spe-

cies was established, as the concentration required for

causing an error of not more than ±2.0% in the absorb-

ance for Kelthane. The Results of these experiments are

shown in Table 1, which showed that the method was

found to be free from interference of various polyhalo-

genated compounds and metal ions, commonly found in

the described samples. Trichloroacetic acid and chloro-

form gave positive interference. N-hexane and petroleum

ether extracts from the vegetables and other samples

have no interference.

4. Application

In Water Sample. 100 ml of kelthane free water sample

was taken and fortified with known amounts of kelthane

Figure 3. Effect of the concentration of benzidine solution.

Figure 4. Effect of temperature.

Figure 5. Effect of time.

and kept for 3 - 4 h.. Then kelthane was extracted in

n-hexane. Hexane was evaporated off and kelthane was

determined by the present as well the reported method

[18]. The recoveries are shown in Table 2.

In Milk Sample. To assess the applicability of the

method for the determination or kelthane in milk samples,

known amounts of dicofol were added to the milk sample.

E. K. JANGHEL ET AL.

729

Kelthane was extracted in n-hexane as reported [6] and

determined by present as well as reported method [18].

The recoveries are shown in Table 2.

In Vegetables and Fruits Samples. Various vegetables

and fruits samples such as tomato, beans grapes were

weighed, crushed and then spiked with known amounts

of kelthane and kept for 3 - 4 h. Kelthane was extracted

in n-hexane. Hexane was evaporated off and kelthane

was determined by the present as well as reported

method [18].The recoveries are shown in Table 2.

The comparison of the present method with other re-

ported [15-18] method is shown in Table 3.

Table 1. Effect of foreign species: (Concentration of kelthane 25 µg/25 ml).

Foreign species Tolerance limit ppm* Foreign species Tolerance limit ppm*

DDT 1000 Cu2+, Cd2+ 1100

Carbaryl, Propoxur 600 Pb2+ 550

2,4-D, 2,4,5-T 450 NO2-, Sn2+, Ca2+, Ni2+ 430

Paraquat BHC 200

150

Zn2+, Fe2+

400

Malathion, CCl4 100 Hg2+ 300

Parathion 50 PO43- 150

* - The amount of foreign species causing error of ±2%.

Table 2. Recoveries of kelthane in various environmental samples.

S.N. Sample Kelthane added µg Kelthane found* µg % Recovery

Proposed method Reported method [18] Proposed method Reported method [18]

Watera

14.25

23.75

13.867

22.50

95.00

92.50

90.00

Milka

14.12

23.46

13.13

20.63

94.13

93.84

87.50

82.50

Tomatob

14.42

24.26

14.25

24.375

96.13

97.44

95.00

97.50

Beansb

13.95

24.70

13.867

24.688

94.33

98.80

92.50

98.75

Grapesb

14.23

24.13

13.99

23.75

94.80

96.52

93.26

95.00

*Mean of three replicate analysis; aSize of sample 100 ml. bSize of Sample 50 gm.

Table 3. Comparison of the proposed method with other spectrophotometric method.

S.N. Methods/Reagents µmax-nm Beer’s law ppmAmount of

pyridine used mlRemarks

1. Fujiwara method

pyridine/NaOH (15) 530 12.4 - 124 5.0 Methods require special type

of distillation apparatus.

2. Modified Fujiwara

method/Pyridine/NaOH (16) 530 200 - Poor sensitivity

3. Sulphanilicacid +

Formic acid (18) 505 1.48-11.8 1.0 Less sensitive

4. Benzidine (Present method) 490 0.13-1.04 1.0 Method is simple, more sensitive free from

inter-ference of other chlorinated hydrocarbon.

E. K. JANGHEL ET AL.

730

5. Conclusions

The data shown in Tables 2 and 3 clearly indicate that

the present method is simple, rapid and more sensitive

than other reported method for determination of kelthane.

It can be successfully applied for the determination of

kelthane in various environmental samples.

6. Acknowledgements

Authors are thankful to the Principal and Head, Chha-

trapati Shivaji Institute of Technology Durg, Principal &

Head, Ashoka institute of Technology & Management,

Rajnandgaon for providing laboratory facilities and fi-

nancial assistance.

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