D K Dodoo

J Apau

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Journal of Science and Technology  © KNUST December 2010 
LINDANE AND PROPOXUR RESIDUES IN COCOA FROM 
CENTRAL REGION OF GHANA 
J. Apau(1), D.K. Dodoo (2) 
(1)Department of Chemistry , Kwame Nkrumah University of Science and Technology, Kumasi, 
Ghana 
E-mail: apaujoseph@yahoo.com 
(2)Department of Chemistry , University of Cape Coast, Cape Coast, Ghana  
ABSTRACT 
Lindane and propoxur residue levels in cocoa samples taken from the Central Region of Ghana 
were determined. Propoxur and Lindane residues in cocoa were extracted by continuous soxhlet 
extraction with a 1:1 v/v acetone-chloroform and acetone-hexane (20:80 v/v) mixture for pro-
poxur and lindane respectively for 12 h. The extracts were passed through preconditioned octa-
decyl (C-18) columns to clean up. The pesticides were then analyzed by gas-liquid chromatogra-
phy using Flame Ionization Detector (FID) and Electron Capture Detector (ECD) for propoxur 
and lindane respectively. The concentration range for lindane in cocoa was 0.055 - 3.318 mg/kg. 
The concentration range for propoxur was 0.001 – 0.991 mg/kg. The mean of lindane in cocoa 
beans were: 0.411 mg/kg, pod 1.113 mg/kg, testa 0.609 mg/kg , placenta 0.905 mg/kg, leaves 
0.892 mg/kg and bark 1.332 mg/kg. The mean concentrations of propoxur in cocoa were: beans 
0.235 mg/kg, pod 0.235 mg/kg, placenta 0.276 mg/kg, leaves 0.104 mg/kg, bark 0.491 mg/kg. 
From the studies it may be preferable to use propoxur for control of pests in cocoa.  
Keywords: Cocoa, Gas chromatography, Lindane, Pesticides, Propoxur. 
INTRODUCTION 
Pesticides have been used extensively over the 
years and this has resulted in environmental 
contamination. Organochlorine pesticides 
(OCs) such as DDT, lindane, alddrin, dieldrin, 
and heptachlor have been found to be persistent 
in the environment in general. Lindane belongs 
to the class IIB (moderately acutely toxic) 
group of insecticides (UNEP/ILO/WHO, 1994). 
Most of the adverse human health effects by 
lindane reported for have been related to agri-
cultural uses (U.S. FDA, 2003). Exposure to 
large amounts of lindane can harm the nervous 
system, producing a range of symptoms from 
headache and dizziness to seizures, convulsions 
and more rarely death (U.S. FDA, 2003; Alva-
rez-Pedrerol, 2008). Prenatal exposure to β-
Hexachlorocyclohexane, an isomer of lindane 
and a production by-product, has been associ-
ated with altered thyroid hormone levels and 
could negatively affect brain development 
(U.S. EPA, 2001). Lindane, being persistent, is 
transported long distances by natural processes 
like global distillation, and it can accumulate 
and concentrate in food chains (Alvarez-
Pedrerol, 2008). When lindane is used in agri-
© 2010 Kwame Nkrumah University of Science and Technology (KNUST) 
Journal of Science and Technology, Vol. 30, No. 3 (2010), pp  15 
Journal of Science and Technology  © KNUST December 2010 
culture, an estimated 12-30% of it volatilizes 
into the atmosphere, where it is subjected to 
long-range transport and can be deposited by 
rainfall. In plants that are transpiring, substan-
tial amount of even very sparingly soluble sub-
stances may enter the roots over a period of 
time and move up to accumulate in the edible 
part of food crops. Lindane is probably taken 
up more readily than most of the other mem-
bers of the group, especially during high rates 
of application.  Tainting or off – flavours of 
cocoa and root crops has often followed the use 
of lindane (Environment News Service, 2001). 
With reported cases of resistance of cocoa pest 
to lindane coupled with accumulated evidence 
that the use of lindane led to the destruction of 
other insects in the ecosystem (Commission for 
Environmental Cooperation, 2006), lindane is 
alternated with propoxur.        
Propoxur is a non-systemic insecticide which 
was introduced by Bayer Limited in 1959. It is 
compatible with most insecticides and fungi-
cides except alkalines, and may be found in 
combination with azinphosmethyl, chlorpyri-
fos, cyfluthrin, dichlorvos, disulfoton, or me-
thiocarb. Agricultural applications include co-
coa, fruit, maize, rice, vegetables, cotton, for-
estry, and ornamentals production. Like other 
carbamates, propoxur can inhibit the action of 
cholinesterase and disrupt nervous system func-
tion. Because it is highly soluble in water, pro-
poxur is moderately persistent, and does not 
adsorb strongly to soil particles; propoxur has a 
high potential for groundwater penetration 
(Howard, 1991; U.S. EPA 1988).  
  
The impact of the excessive use of pesticides, 
especially organochlorines in the African eco-
system brought scientists together for the first 
Joint FAO/IAEA meeting on the impact of or-
ganochlorine use on the flora and fauna in Af-
rica – Tanzania in 1991 (WHO, 1991). The 
meeting recommended the need for scientific 
data on the use, dissipation and bioconcentra-
tion of these pesticides.  It is in line with this 
that this project on lindane and propoxur resi-
dues in cocoa from the Central Region of 
Ghana was chosen. Central Region is a major 
producer of cocoa and the University of Cape 
Coast where the project was done is located 
there. The data obtained could help in policy 
formulation on the use of lindane and propoxur 
on cocoa in Ghana. 
 
MATERIALS AND METHODS 
All solvents were purchased from British Drug 
House (BDH) and were of pesticide residue  
determination grade. Lindane and propoxur 
standards were purchased from Ehrenstorfer, 
GmbH, Germany, in sealed vials. Solid phase 
extraction (SPE) bond elute C-18, 3 cc/500 mg 
was purchased from Varian Inc., USA. Glass-
ware was washed with detergent, rinsed with 
distilled water and acetone and were heated to 
180 ˚C for 2 h to dry. 
 
Part of the cocoa plant comprising the fruit, 
leaves and bark was collected from six cocoa 
growing towns in the Central Region of Ghana. 
The sampled locations included Abura 
Dunkwa, Assin Fosu, Breman Asikuma, Twifu 
Mampong, Jukwa and Berase. In each town 
five farms which were sprayed by Agriculture 
Extension officers every year were selected. 
About 50 samples of fruit, leaves and bark were 
randomly taken from each farm. Sampling was 
done from October to December 2006. Ten 
samples each were taken every two weeks. 
Samples were collected and washed in distilled 
water and transferred into labeled storage bags. 
Prior to analysis samples were stored in freez-
ers and maintained at 4 oC to prevent deteriora-
tion. Samples were air dried for four weeks and 
pulverized with wiring blender. Lindane resi-
dues in cocoa samples were extracted using 
soxhlet extraction (Therdteppitak et al., 2003). 
Fifty grams sample was put in extraction thim-
ble, and placed in a soxhlet extractor. The sam-
ple was extracted with 150 ml of acetone: hex-
ane (20: 80 v/v) at 50 ˚C for 12 h. The extracts 
were filtered, concentrated to 1 ml using bϋchi 
vacuum rotary evaporator. Each of the raw ex-
tracts was then dissolved in 10 ml hexane and 
passed through pre-conditioned octadecyl (C-
18) columns at a rate of 2 ml min-1. The column 
Apau and Dodoo 16 
Journal of Science and Technology  © KNUST December 2010 
Lindane and Propoxur residues in cocoa... 17 
was washed with 1 ml, 30% methanol followed 
by 1 ml deionized water and was allowed to 
dry. The sample which was trapped in the col-
umn was eluted 5 times with 1 ml aliquots of 
hexane to recover the lindane residue.  Hexane 
in the sample was allowed to evaporate off, 
leaving the residue alone in the vial. Concen-
trated sample was dissolved in 1 ml portion of 
hexane, mixed thoroughly with a whirl mixer 
and then transferred to auto sample vial for 
analysis using Gas chromatograph.  
 
Propoxur residues in cocoa samples were ex-
tracted using soxhlet extraction (Bentum et al., 
2006).  A 50 g sample was put in extraction 
thimble, and placed in a soxhlet extractor. The 
sample was extracted with 150 ml of acetone: 
chloroform blend (1:1 v/v) at 50 ˚C for 12 h, 10 
ml buffer solution of EJ-275, pH buffer at 4 
was added to the extracts and partitioned with 
20 ml chloroform using a separating funnel. 
The aqueous layer was discarded. The organic 
layer was evaporated to 1 ml using vacuum 
rotary evaporator. The extracts were dissolved 
in 20 ml hexane and placed in separating funnel 
and partitioned with 10 ml acetonitrile. The 
hexane layer was discarded. The acetonitrile 
layer was evaporated to 1 ml using vacuum 
rotary evaporator. Extracts were dissolved in 50 
ml chloroform and passed through precondi-
tioned octadecyl   (C-18) columns at a rate of 2 
ml min-1 to clean up. The column was washed 
five times with 5 ml chloroform to recover pro-
poxur residue. Propoxur extracts were evapo-
rated to 5 ml and 1µl aliquot was added for 
analysis by gas chromatograph. 
 
Each prepared sample was analysed  for lin-
dane by gas-liquid chromatographic techniques 
using Hewlett Packard 5890 series II with inte-
grator (Hewlett Packard 3396A) gas chromato-
graph  equipped with a SPB-608 (length 30 m, 
ID 0.5 mm and film thickness of 1.5 µm) fused 
silica capillary column. The detection system 
consisted of a 63Ni electron capture detector. 
The column oven was maintained at 200 ˚C. 
The 63Ni detector was operated at 250 ˚C. The 
instrument injection ports were at 200 ˚C. The 
carrier gas was nitrogen at a flow rate of 25 ml/
min. The injection technique was on-column 
and injection volume was 1 µl. 
Each prepared sample was analysed for pro-
poxur by gas-liquid chromatographic tech-
niques using varian 3700 gas chromatograph 
equipped with a DB-5 column  (length 30 m, 
ID 0.5 mm, 0.25m film) and contains polyphen-
ylsilozane. Carrier gas was helium at a flow 
rate of 30 ml/min. The column oven was main-
tained at 310 ˚C, the injected ports at 300 ˚C 
and the flame ionization detector was operated 
at 320 ˚C. The injection technique was on-
column and injection volume was 1 µl. 
 
RESULTS AND DISCUSSIONS 
The following results were obtained from this 
study. 
 
Figure 1 indicates that lindane was present in 
all the parts of the cocoa plant studied.  The 
levels of lindane concentration in cocoa beans 
ranged from 0.055 to 0.897 mg/kg with the 
highest concentration occurring in beans from 
Abura Dunkwa. However, the Codex Alimen-
tarius Acceptable Daily Intake (ADI) for lin-
dane is 0.001 mg/kg (FAO/WHO, 1998).  The 
results are comparable to those reported by 
Lynes (1978) for the West African sub region 
which ranged between 0.001 and 0.600 mg/kg. 
The mean concentration of lindane in beans 
was 0.411 ± 0.348 mg/kg. The average concen-
tration of lindane in the pod was 1.113 ± 0.918 
mg/kg. The concentration ranged from 0.082 to 
2.546 mg/kg with the highest occurring in pod 
from Twifu Mampong. The concentration range 
for the testa was from 0.150 to 1.473 mg/kg 
with a mean concentration of 0.609 ± 0.517 
mg/kg and the highest concentration occurring 
in testa was from Abura Dunkwa.  Average 
concentration of lindane in placenta was 0.905 
± 0.835 mg/kg. The levels ranged from 0.083 to 
2.230 mg/kg with the highest concentration 
detected in placenta of samples from Twifu 
Mampong. An average lindane concentration of 
0.892 ± 0.858 mg/kg was found for the leaves. 
However, the concentrations ranged from 0.167 
Journal of Science and Technology  © KNUST December 2010 
18 
Fig. 1:  Lindane residues in cocoa plant in mg/kg collected from different districts in Central 
Region 
Fig. 2: Propoxur residues in cocoa plant in mg/kg collected from different districts in Central 
Region  
Apau and Dodoo 
 
Journal of Science and Technology  © KNUST December 2010 
19 
to 2.245 mg/kg, with the highest detected from 
leaves from Assin Fosu. The mean concentra-
tion of lindane levels in the bark was 1.333 ± 
1.208 mg/kg. The bark had concentrations 
ranging from 0.199 to 3.318 mg/kg. The high-
est concentration was detected in the bark from 
Assin Fosu. 
 
The order of lindane concentrations in the vari-
ous parts of the cocoa tree was 
 bark > pod > leaves > placenta > testa > beans. 
The bark is a storage organ in which most un-
wanted substances are stored. It conducts water, 
food and chemicals to other parts of the plant. 
The bark here retains much of the pesticide. 
The order also suggests that the outer parts  are 
exposed directly to the pesticide during applica-
tion accumulates much of it. New leaves and 
fruits are restored year after year to replace old 
ones. It is therefore not surprising that the bark 
contains the highest concentration of lindane. 
 
Figure 2 shows that propoxur was not detected 
in most of the parts of cocoa trees sampled.   
The levels of propoxur in the beans ranged be-
tween 0.0106 and 0.664 mg/kg, with an average 
concentration of 0.235 ± 0.372 mg/kg. The 
highest concentration of propoxur occurred in 
beans from Twifu Mampong. The levels, with 
the exception of those from Twifu Mampong 
were comparable to the FAO/WHO ADI of 
0.02 mg/kg (Kidd et al., 1991). This suggests 
that farmers at Twifu Mampong might not be 
using propoxur properly in agricultural prac-
tices. With the exception of Twifu Mampong 
which had concentration of 0.001 mg/kg for 
testa, the rest had levels below detection limit. 
This can be attributed to the fact that propoxur 
is not a persistent insecticide. The pod had pro-
poxur levels in the range of 0.003 to 0.361 mg/
kg with the highest level detected in pod from 
Abura Dunkwa. A mean concentration level of 
0.235 ± 0.335 mg/kg was found for the pod. A 
concentration range of 0.169 to 0.544 mg/kg 
was detected for the placenta with the highest 
concentration from Jukwa, and an average of 
0.276 ± 0.179 mg/kg. The levels of propoxur in 
the leaves from Abura Dunkwa contained the 
highest concentration. The level falls within 
0.021 to 0.252 mg/kg with an average concen-
tration of 0.104 ± 0.128 mg/kg. The bark had 
concentration ranging from 0.189 to 0.991 mg/
kg, with a mean concentration of 0.491 ± 0.436 
g/kg. The bark from Breman Asikuma had 
the highest level. The order of propoxur con-
centration in the cocoa plant was bark > pod > 
placenta > leaves > beans > testa. It was ob-
served that the highest concentration of pro-
poxur was detected for the bark of the cocoa 
and this was the same for lindane. 
 
CONCLUSION 
Comparing the concentrations of the pesticides, 
it is noted that for the same part, there were 
higher levels of lindane than propoxur. How-
ever, propoxur was sprayed on the cocoa trees 
uring the year of the study. This indicates the 
higher persistence of lindane in the environ-
ment.  The fact that propoxur was not detected 
in many parts of the cocoa plant shows how 
easily propoxur is decomposed in the environ-
ment. From the studies it may be preferable to 
use propoxur for control of pests in cocoa. The 
study also revealed that the concentration of 
lindane in cocoa beans from the Central Region 
of Ghana was below FAO/WHO recommended 
maximum residue limit of 1 mg/kg (Lynes, 
1978). The concentration of propoxur in cocoa 
beans was also comparable to FAO/WHO ADI. 
This could be attributable to good farming 
practices. Therefore cocoa beans from Ghana 
are safe for consumption.  
                                                                                                                   
ACKNOWLEDGEMENT 
The authors express gratitude to Messers Osei 
Akoto, Akwasi Acheampong and Godfred 
Darko all at KNUST for proof reading the 
manuscript and making constructive sugges-
tions. 
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LINDANE AND PROPOXUR RESIDUES IN COCOA FROM CENTRAL REGION OF GHANA

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LINDANE AND PROPOXUR RESIDUES IN COCOA FROM CENTRAL REGION OF GHANA

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