Estimation of Quizalofop Ethyl Residues in Black Gram(Vigna mungo L.) by Gas Liquid Chromatography

Kousik Mandal • Sanjay Kumar Sahoo •

R. S. Battu • Balwinder Singh

Received: 4 February 2013 / Accepted: 15 November 2013 / Published online: 26 November 2013

� Springer Science+Business Media New York 2013

Abstract Quizalofop ethyl, a phenoxy propionate herbi-

cide is used for post emergence control of annual and

perennial grass weeds in broad-leaved crops in India. The

experiments were designed to study the harvest time resi-

dues of quizalofop ethyl in black gram for two seasons. At

harvest time, the residues of quizalofop ethyl on black

gram seed, foliage and soil were found to be below the

determination limit of 0.01 mg kg-1 following a single

application of the herbicide at 50 and 100 g a.i. ha-1 for

both the periods. Application of the herbicide is quite safe

from a consumer and environmental point of view.

Keywords Quizalofop ethyl � Black gram �Residues � Dissipation

Black gram (Vigna mungo L.) is one of the important pulse

crops grown throughout India. It is consumed in form of

‘dal’. It is the chief constituent of ‘papad’ and also of ‘bari’

(spiced balls) which make curry. In the south, the husked

dal is ground into a fine paste, allowed to ferment, and is

then mixed with equal quantity of rice flour or make ‘dosa’

and ‘idli’. It is used as a nutritive fodder specially for milch

cattle. It is also used as a green manuring crop. Urd grain

contains about 24 % protein, 60 % carbohydrate, 1.3 % fat,

and is the richest among the various pulses in phosphoric

acid, being five to ten times richer than in others (Singh

2003).

Quizalofop ethyl, ethyl (2RS)-2-[4-(6-chloroquinoxalin-

2-yloxy)phenoxy]propionate (Fig. 1) is used for post

emergence control of annual and perennial grass weeds in

broad-leaved crops, particularly sugar beet, fodder beet,

oilseed rape, sunflowers, soybeans, cotton, peanuts, flax,

alfalfa and some vegetables. It is a selective and systemic

herbicide absorbed by the leaves with translocation

throughout the plant. As a systemic herbicide to inhibit

acetyl CoA carboxylase, quizalofop ethyl was absorbed

from the leaf surface and translocated throughout the plant,

moved in both xylem and phloem from the treated foliage

to the root system, and accumulated in the meristematic

tissue, and thus it inhibits the biosynthesis of fatty acid.

Considerable concern is being expressed over the

magnitude of pest control chemicals left in food stuffs

following their use on crops. It is important to ensure

that levels of harvest time residues of pesticides on

foodstuffs do not pose any hazard to consumers and are

admissible in domestic as well as international trade.

Therefore, the present studies were undertaken to

determine the harvest time residues of quizalofop ethyl

on the black gram crop under sub-tropical conditions of

Ludhiana, Punjab, India.

Materials and Methods

The certified reference standard of quizalofop ethyl (purity

100.0 %) was supplied by M/s Dhanuka Agritech Limited.

Targa Super 5 EC (quizalofop ethyl) used for application

on the crop was obtained from M/s Dhanuka Agritech

Limited, India. Analysis of acetone extract of the formu-

lation showed only quizalofop ethyl and no interfering

peak was observed near the retention time of the compound

estimated.

K. Mandal (&) � S. K. Sahoo � R. S. Battu � B. Singh

Pesticide Residue Analysis Laboratory,

Department of Entomology, Punjab Agricultural University,

Ludhiana 141004, Punjab, India

e-mail: kousik11@gmail.com

123

Bull Environ Contam Toxicol (2014) 92:115–118

DOI 10.1007/s00128-013-1159-4

Black gram (var. Mash 1-1) was raised during Kharif 2008

and 2009 at Punjab Agricultural University, Seed Farm La-

dhowal, Ludhiana, Punjab, India, and the crop was raised

according to recommended agronomic practices (Anony-

mous 2008). Three replications were selected for each

treatment i.e. control, recommended, and double the rec-

ommended dosages. The three replications for each treat-

ment were arranged in a randomized block design, and the

size of the each plot was 100 m2. The soil was of light texture

with low content of organic matter. Other relevant properties

of the soil were organic carbon = 0.30 %; pH = 8.0;

sand = 78.0 %; silt = 10.2; and clay = 11.8 %. The

meteorological data, comprising temperature, relative

humidity and number of sunlight hours, from the first spray to

final sampling (2008 and 2009) are presented in Fig. 2.

A single post-emergent application of quizalofop ethyl

(Targa Super 5 EC) at 50 and 100 g a.i. ha-1 was made at

20–30 days after sowing in black gram. In control plots,

only water was sprayed. Pesticide was sprayed as a foliar

application in three replications with the help of a Knap-

sack sprayer fitted with flat fan nozzle.

About 1 kg each of black gram seed and foliage was

collected randomly from control and treated plots of each

treatment at harvest time (94 days) in both the years during

Kharif 2008 and 2009 after application of the insecticide.

The samples from each treatment plot were pooled and

mixed thoroughly on a sheet of polyethylene in the field. A

subsample of about 250 g was taken from each pooled

sample from each treatment plot and transported to the lab-

oratory, and a representative 50 g was processed immedi-

ately after the subsample reached the laboratory.

Soil samples (1 kg) were also collected at harvest time

(94 days) after herbicide application. Soil samples were col-

lected separately from 10–15 sites of each treated plot with the

help of a tube auger at a depth of about 10–15 cm. Soil from

the sites were pooled and sieved, and extraneous matter,

including stones/pebbles, were removed. After thorough

mixing, a subsample of about 1 kg was taken from each

pooled sample from each treatment plot and transported to the

laboratory. A representative 50 g sample was processed

immediately after bringing the samples in the laboratory.

Samples were processed and analyzed at the Pesticide

Residue Analysis Laboratory, Department of Entomology,

Punjab Agricultural University, Ludhiana. A representative

50 g sample of chopped and macerated black gram seed,

foliage and soil were dipped separately overnight into

100 mL acetone in an Erlenmayer flask for 24 h. The

extract was filtered into 1 L separatory funnel along with

rinsings of acetone. The filtrate in the separatory funnel

was diluted with 600 mL brine solution (almost saturated

sodium chloride solution), and the contents were parti-

tioned three times into 100, 75 and 50 mL toluene. The

combined organic layers were collected into 500 mL bea-

ker through 3.75 cm layer of anhydrous sodium sulfate

supported on a pre washed glass wool in a funnel. Toluene

fractions were treated with 500 mg activated charcoal

powder for about 2–3 h at room temperature. The clear

extract was filtered through Whatman filter paper No. 1,

concentrated to near dryness and about 20 mL acetone was

again added and concentrated using a rotary vacuum

evaporator at 40�C. The final volume was reconstituted to

about 5 mL using acetone. Soil samples were processed in

a similar manner as described above.

Analysis of quizalofop ethyl was carried out on a gas

liquid chromatograph (GLC) (Shimadzu Model GC-2010)

equipped with electron capture detector (ECD) 63Ni sup-

plied by M/S Shimadzu Corporation, Kyoto, Japan. A

capillary column DB-1 (30 m 9 0.25 mm i.d. 9 0.25 lm

N

N

OCl

O CH

CH3

O

O

H2C CH3

Fig. 1 Structure of quizalofop

ethyl

Fig. 2 Meteorological data,

comprising temperature, relative

humidity and number of

sunlight hours during the

experimental period

116 Bull Environ Contam Toxicol (2014) 92:115–118

123

film thickness) with split ratio 1:10 was used for estimation

of quizalofop ethyl. GC operating parameters were as

follows: carrier gas flow rate: 30 mL min-1; temperature:

injection port: 290�C, detector: 300�C, column tempera-

ture: 270�C. Under these operating conditions the retention

time of quizalofop ethyl was found to be 7.262 min.

Results and Discussion

The selected method provided good recoveries of quiz-

alofop ethyl residues, 85.27 %–91.07 % from black gram

foliage and seed samples in the concentration ranges of

0.01–0.10 lg g-1. In the case of soil samples 84.81 %–

92.68 % recovery was found for quizalofop ethyl at

0.01–0.10 lg g-1 fortification level (Table 1). So, the

percent recoveries of quizalofop ethyl in black gram foli-

age, seed and soil were found to be consistent and more

than 85 %. Therefore, the results have been presented as

such without applying any correction factor.

The precision of the method was determined by

repeatability studies of the method and expressed by rela-

tive standard deviation (RSD) values. The RSD for

repeatability (RSDr) was measured by comparing the SD

values of the recoveries from spiked samples analyzed the

same day. The RSDr values were ranged from 1.27 % to

4.67 % quizalofop ethyl for the spiking levels as shown in

Table 1.

Half-scale deflection was obtained for 0.5 ng quizalofop

ethyl which could be easily identified from the baseline and

taken for calculating 10 % full scale deflection which

comes to be 0.1 ng. When 50 g of sample was extracted,

cleaned up and final volume made to 5 mL, 1 lL (10 mg)

of sample when injected did not produce any background

interference. Thus, limit of quantification (LOQ) was found

to be 0.01 mg kg-1 and limit of detection (LOD) being

0.003 mg kg-1.

The samples of black gram seed and foliage were col-

lected and analysed at harvest from the treatments of

quizalofop ethyl 5 EC at 50 and 100 g a.i. ha-1. The

interval between last application and the harvest of the crop

was found to be 94 days during 2008 and 2009. The resi-

dues of quizalofop ethyl black gram seed and foliage were

found to be less than the LOQ arrived at 0.01 mg kg-1.

Samant and Senapati (2004) studied the residues of qui-

nalphos in black gram (var. Dhauli) following application

at 0.5 and 1.0 kg a.i. ha-1. The safe waiting period of

17–22 days is reported.

Sahoo et al. (2012) studied the quizalofop ethyl residues

on onion during 2009 and 2010. The average initial

deposits of quizalofop ethyl on onion were observed to be

0.25 and 0.33 mg kg-1, respectively, following single

application of the herbicide at 50 g a.i. ha-1 during 2009

and 2010, respectively. At harvest time, the residues of

quizalofop ethyl on onion were found to be below deter-

mination limit of 0.01 mg kg-1 following single applica-

tion of the herbicide at 50 and 100 g a.i. ha-1 for both the

periods. Koeppe et al. (1990) reported the metabolism of

[phenyl-U-14C]quizalofop-ethyl or [quinoxaline-14C]quiz-

alofop-ethyl in soybean and cotton plants. [14C]Quizalo-

fop-ethy1 was applied to soybean or cotton plants at

112 g a.i. acre-1 as a post emergence spray, and plant

samples were harvested initially (0 day) and at 3, 6, and

13.5 (maturity) weeks after treatment. No detectable 14C

residues (\0.01 mg kg-1) were found in mature beans or

pods, whereas the mature fiber and seeds from the cotton

contained 0.08 and 0.09 mg kg-1 total 14C residues,

respectively.

Soil samples collected from black gram field at 94 days

of application were not found any residues of quizalofop

ethyl for both the dosages in both the seasons during 2008

and 2009. Sahoo et al. (2012) reported the quizalofop ethyl

residues following application of quizalofop ethyl at 50 and

100 g a.i. ha-1 during 2009 and 2010. Soil samples col-

lected from onion field at 10 days after application were

not found any residues of quizalofop ethyl for both the

dosages in 2009 as well as 2010. In the case of cropped soil

no residues were detected after 3rd and 5th day respec-

tively, following application of mancozeb at 750 and

1,500 g a.i. ha-1 for all the three seasons (Sarkar et al.

2005). No residues were detected 7 days after application

in the soil following application of propineb at 1,225 and

2,450 g a.i. ha-1 (Ganguly et al. 2009).

Acknowledgments The authors are thankful to Indian Council of

Agricultural Research, New Delhi India for sponsoring the project

and also to the Head, Department of Entomology, PAU, Ludhiana and

Director, Seed Farm Ladhowal, Punjab Agricultural University, Lu-

dhiana Punjab, India, for providing necessary research facilities.

Table 1 Recovery studies of quizalofop ethyl on black gram seed,

black gram foliage and soil

Substrate Level of

fortification

(mg kg-1)

% Recoverya RSDr

(%)

Black gram seed 0.01 85.27 2.73

0.05 89.07 5.65

0.10 91.07 2.20

Black gram foliage 0.01 85.50 4.67

0.05 87.14 4.27

0.10 89.21 1.54

Soil 0.01 88.88 2.34

0.05 92.68 5.10

0.10 84.81 1.27

a Each value is the mean of three replicate determinations

Bull Environ Contam Toxicol (2014) 92:115–118 117

123

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