Simultaneous Determination by Gas Chromatography of Lindane and Carbaryl in Combined Formulations
http://www.e-journals.net
ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2011, 8(1), 391-399
Simultaneous Determination by
Gas Chromatography of Lindane and
Carbaryl in Combined Formulations
INDRAJIT SEN, AJAY SHANDIL, MANJEET AGGARWAL and
RAKESH KUMAR KHANDAL*
Shriram Institute for Industrial Research
19 University Road, Delhi-110007, India
Received 18 January 2010; Revised 2 April 2010; Accepted 21 May 2010
Abstract: A gas chromatographic method developed and validated for
simultaneous determination of lindane and carbaryl for quality evaluation of
lindane-carbaryl granule, using a glass capillary HP5 column (30 m x 0.32 mm;
0.25 µm), temperature programming with flame ionization detector and
dibutylphthalate as an internal standard. The calibration graphs were found
linear in the concentration range of 1 µg/mL to 1000 µg/mL for both lindane
and carbaryl with correlation coefficient of 0.999 and 0.999 respectively and
co-efficient of variation for intra-day and inter-day repeatability studies at
different concentration levels was found to be less than 2%. The accuracy of
method ranges between 98.5% to 100.8%. Specificity and robustness were also
within the acceptable range. The method is highly sensitive with LOD and
LOQ as 0.5 and 2 µg/mL for lindane and carbaryl respectively. The method
has been tried on several formulations of lindane-carbaryl granules for quality
control and has been found to be applicable.
Keywords: Gas chromatography, Carbaryl, Lindane, Combined formulation.
Introduction
Ever since the combination formulations consisting of more than one technical grade
pesticide were allowed around a decade ago in India, there has been a large number of
combination formulations being introduced in the market. The experience with the
combination formulations has been encouraging, as their efficacy has been found to be better
than the formulations containing single ingredient1.
Granules of lindane and carbaryl is one of the most widely used agrochemical formulation
consisting of combination of two very important pesticide ingredients namely lindane and carbaryl
present at concentration levels of 4% each. Lindane, also known as gamma-hexachlorocyclohexane
392
R. K. KHANDAL et al.
(γ-HCH)2 is an organochlorine chemical that has been used both as an agricultural insecticide and
as a pharmaceutical treatment for infestations of lice and scabies3,4. Under the IUPAC system,
lindane is named as gamma-1α, 2α, 3β, 4α, 5α and 6β-hexachlorocyclohexane, which is a white,
odorless, crystalline solid with molecular weight of 290.82 g/mole and molecular formula of
C6H6Cl6 and chemical structure1, 5 as shown in Figure 1a.
Carbaryl, named as per IUPAC as 1-naphthyl methyl carbamate is a white crystalline
solid having molecular weight of 201.22 g/mole and molecular formula of C12H11NO2 with
the chemical structure1,6-8 as shown in Figure 1b.
Figure 1a. Chemical structure of lindane Figure 1b. Chemical structure of carbaryl
(gamma-1α, 2α, 3β, 4α, 5α and 6β- (1-napthyl methyl carbamate)
hexachlorocyclohexane)
Carbaryl is widely used as an insecticide for home gardens, commercial agriculture and
forestry9,10. Lindane-carbaryl granules (a colored formulation) is one of the most widely
used agrochemical formulations. It has a broad range of insecticidal activity, contact
stomach action, nervous and respiratory action11-16 . The formulation is used for various crop
pests in soil and agricultural fields17-21.
As there are no validated methods available in the literature for the simultaneous determination
of both lindane and carbaryl, we have made an attempt to evaluate the quality of the combined
granular formulation containing lindane and carbaryl with respect to the concentration of the active
ingredients. Though there are methods available for the analysis of lindane in lindane containing
formulation or carbaryl in carbaryl formulations as per CIPAC or WHO specification they do not
mention about the analysis of combined lindane-carbaryl formulations22-28. On the other hand
although Indian standard (IS) specification does have a protocol for analysis of lindane-carbaryl
granules (IS: 11784:1986), two different methods are specified for the analysis of lindane and
carbaryl respectively. For the analysis of lindane, the specification (IS: 882-1984) mentioned the gas
chromatographic method using α-naphthol as an internal standard, whereas for the analysis of
carbaryl, spectrophotometric method is mentioned (IS: 7539-1975)29-35. The analysis of two
components individually using two different methods is not only time consuming but it has also
been observed that, during the gas chromatographic determination of lindane using α-naphthol as
an internal standard, produces inaccurate results. This is due to fact that α-naphthol generally
formed as an intermediate during the synthesis of carbaryl, is present as an impurity in the lindanecarbaryl formulation and thereby causes an interference with the accurate determination of lindane
and carbaryl when internal standard used is also α-naphthol.
The aim of the present work was to develop and validate an analytical method using a
gas chromatographic technique for simultaneous determination of both lindane and carbaryl
which is comparatively faster with significant precision, accuracy and resolution.
Experimental
The reference standards lindane (purity: 99%) and carbaryl (purity: 99%) were obtained from
Sigma-Aldrich (USA). Dibutyl phthalate having purity 99% was procured from Fluka chemicals
Simultaneous Determination by Gas Chromatography
393
(USA) and acetone (HPLC grade) was purchased from SD fine chemicals, Mumbai, India.
Formulations (within their shelf life) of lindane-carbaryl granules of commercial grade were
procured from the local market. All chemicals were used as received.
Gas chromatography analysis was carried out using VARIAN-CP-3800 Gas Chromatograph
equipped with split/splitless injector, a flame ionization detector was used for the
measurements and glass capillary HP-5, ID: 0.32 mm, length: 30 m, film thickness: 0.25 µm;
packed with non-polar polymer [(5%-phenyl)-methylpolysiloxane]. Mettler weighing balances
with a least count of 0.0001 g and 0.001 mg for weighing of samples and standards
respectively. Calibrated ‘A’ grade glassware of borosil procured from local market.
Preparation of internal standard stock solution (A): Dibutyl phthalate (DBP)
Approximately 0.5 g of dibutyl phthalate was accurately weighed and transferred into 100 mL
volumetric flask, dissolved and diluted to volume using HPLC grade acetone.
Preparation of reference standard solutions (B)
Approximately 2.5 mg each of reference standard of lindane and carbaryl were weighed accurately
and transferred into 25 mL volumetric flask. To this 2.5 mL of internal standard stock solution (A)
was added using a pipette and total volume was made up to the mark by HPLC grade acetone.
Preparation of sample solutions (C)
Approximately 60 mg each of the se (...truncated)
