American Journal of Analytical Chemistry, 2011, 2, 1-15 doi:10.4236/ajac.2011.228118 Published Online December 2011 (http://www.SciRP.org/journal/ajac) Developments in Analytical Methods for Detection of Pesticides in Environmental Samples Rama Bhadekar*, Swanandi Pote, Vidya Tale, Bipinraj Nirichan Department of Microbial Biotechnology, Rajiv Gandhi Institute of Information Technology & Biotechnology, Bharati Vidyapeeth Deemed University, Pune, India E-mail: *[email protected] Received November 19, 2011; revised December 21, 2011; accepted December 28, 2011 Abstract The present review gives a survey of all the published methods along with their advantages and limitations. Traditional methods like thin layer chromatography, gas chromatography, liquid chromatography etc are still in use for this purpose. But some recent bio-analytical methods such as immunosensors, cell based sensors etc. have also gained equal importance. This article also overviews various electro-analytical methods and their applications as detection devices when combined with FIA and biosensors. Lastly nanoparticle based biosensors have also been discussed. The review concludes with futuristic approach to reduce the risks caused by pesticides. This scrutiny should provide concise evaluation of different techniques employed for pesticide detection in environmental samples. Keywords: Biosensors, Chromatography, Detection, Flow Injection Analysis, Nano Particles, Pesticides, Pollutants 1. Introduction ganochlorines (dichlorodiphenyltrichloroethane, chlor- dane, aldrin, dielrin, lindane, endrin) and botanical insec- People have contradictory ideas about the meaning of ticides (nicotine, rotenoids, pyrethrum). Herbicides are pesticides. The dictionary defines pesticide as a sub- used to destroy other weeds that interfere with produc- stance for destroying harmful insects. The scientists are tion of the desired crop. Based on their structure they are of the opinion that pesticides are chemical or biological grouped into chlorophenoxy compounds (e.g.: 2,4-D, 2, substances that are designed to kill or retard the growth 4,5-T), dinotrophenols like 2-methyl-4,6-dinitrophenol of pests interfering with the growth of crops, shrubs, (DNOC), bipyridyl compounds like paraquot, carbamate trees, timber and other vegetation desired by humans. herbicides, substituted urea, triazines and amide herbi- The term pesticide includes substances intended for use cides like alanine derivatives. Fungicides include a num- as plant growth regulators, defoliants, desiccants or agents ber of structurally different chemicals like cap tan, folpet, for thinning fruit or preventing the premature fall of fruit. pentachlorophenolziram, nambam etc. Fungicides con- The substances applied to crops either before or after taining mercury are known to cause nerve disorders [2]. harvest to protect the commodity from deterioration dur- Rhodenticides are designed to kill rodents, mice, squir- ing storage and transport also come under the category of rels, gophers and other small animals. They vary from pesticides [1]. highly toxic one with the ability to kill an organism with Pesticides are broadly classified into two groups viz A) one-time dose or less toxic ones requiring repeated in- chemical pesticides and B) biopesticides. A) Chemical gestion over a period of time. Nematicides act against pesticides are conventionally synthetic materials that di- nematodes like Meloidogyne incognita, Criconemella rectly kill or inactivate the pest. They are classified ac- xenoplax etc. cording to the type of organisms they act against as for B) Biopesticides are pesticides derived from natural example 1) insecticides, 2) herbicides, 3) fungicides, 4) sources like animals, plants, bacteria, and certain miner- rodenticide, 5) nematicides [2]. Insecticides include or- als. For example, canola oil and baking soda have pesti- ganophosphates (TEPP, parathion. trimesters of phos- cidal applications and are considered biopesticides. Bio- phates and phosphoric acids), carbamates (aldicarb), or- pesticides fall into three major classes: Copyright © 2011 SciRes. AJAC 2 R. BHADEKAR ET AL. 1) Microbial pesticides consist of microorganisms like important component for plant growth. Pesticides ham- bacteria, fungi, viruses or protozoa as the active ingredi- per the fertility of soil by inhibiting the storage of nitro- ents. They can control many different kinds of pests, gen and other essentials in soil. Light and toxic com- although each with separate active ingredient that is rela- pounds are suspended in air by pesticide spray. This tively specific for its target pest(s). 2) Plant-Incorpo- causes air borne diseases and nasal infections. Besides all rated-Protectants (PIPs) are pesticidal substances that are the environmental hazards; pesticides pose serious risk to produced by genetically modified plants for example: mankind. Health hazards caused by some of the pesti- introduction of Bt toxin gene in the cotton plants. 3) cides are summarized in Table 1. Different pesticides Biochemical pesticides are naturally occurring substances have different acceptable residual levels and these are set that control pests by non-toxic mechanisms (for e.g. in- up by World Health Organization (WHO), European sect sex pheromones that interfere with mating as well as Community (EU), FAO (Food and Agricultural Organi- various scented plant extracts). Biopesticides are envi- zation) of UN, US environmental protection agency ronmentally safe and non toxic to plants and animals. (EPA) and the US National Institute for Occupational However, their use is limited due to 1) less social aware- Safety and Health (NIOSH) [3-5]. The Toxicity of pesti- ness, 2) comparatively lower crop yields, 3) need for cides, made it essential to have accurate and reliable me- frequent applications, 4) less worked research area. thods of monitoring their levels for safety purposes. Ear- On the contrary, application of chemical pesticides has lier techniques used for pesticide detection were chroma- proved to be economically beneficial and hence their use tographic methods like Gas Chromatography (GC), High has increased globally especially after the advent of Performance Liquid Chromatography (HPLC) along with “Green Revolution”. The productivity of crop has been Mass Spectrometry (MS) etc. They were sensitive and increased by use of suitable pesticide. They protect the reliable. However, they had limitations like 1) complex crop from disease causing organisms, from plant patho- procedure, 2) time consuming sample treatments, 3) need gens and also from vector borne diseases. Another im- of highly trained technicians, 4) inability to perform on portant advantage is reduction in cost of labor. site detection etc. To improve these methods newer tech- Even though pesticides play significant role in agri- niques are being developed. The new techniques use culture they are the most important environmental pol- more sensitive devices like chromatographic techniques lutants. This is due to their wide spread presence in water, with various detection methods, electro analytical tech- soil, atmosphere and agricultural products. Currently it niques, chemical and biosensors, spectroscopic tech- poses major threat not only to living organisms but also niques and flow injection analysis (FIA). Sometimes a to environment specially ground and surface water. Syn- combination of one or more methods proved successful thetic pesticides affect the growth of plants. Chemical in detecting a particular class of pesticide. This article compounds in the pesticides are not biodegradable. This presents an all embracing survey of the classical methods causes their sedimentation near plant roots making the along with update knowledge of recent advances in the supply of essential NPK inefficient. This inefficiency techniques. hinders growth of crops and their resistance to other harmful microbes. Pesticides percolate into the soil and 2. Spectrophotometry get mixed with ground water. This causes draining of pesticides into the nearby stream or lake. This in turn This was a widely used method for the detection of pes- adversely disturbs the aquatic eco system. Soil is another ticide residues from environmental samples. Spectro- Table 1. Harmful effects of pesticides on humans. Type of pesticide Effects observed Ref. Adversely affects nerve functioning, direct exposure can cause eye problems like blurring of Organophosphates [6,7] vision, reddening, retardation in fetal growth etc. Disruption of dopamine transport in the brain, increased risk of lung and pancreatic cancer, Chlorides [8] neutrophil inflammation etc. Methyl Bromide Increase in serum albumin level [9] Mercury containing fungicides Nerve disorders [10] Irritation of skin and eyes, slowing of heart beats, weakness of muscles, central nervous system Fungicides like atrazines, amides, etc. [11] disorders etc. Rhodenticides like Strychnine Sodium Complete loss of hair, paresthesias, nausea, vomiting and abdominal pain, pulmonary oedema [12] monofluoroacetate Thallium, etc. bronchopneumonia, diaphoresis, blurred vision and severe symmetric extensor muscle spasms Copyright © 2011 SciRes. AJAC R. BHADEKAR ET AL. 3 photometry measures the amount of light absorbed by 3.1. Potentiometry the analyte solution and this amount of light is directly proportional to the quantity of the analyte. The technique Potentiometry measures the potential of electrochemical is based on two properties of light: 1) particle nature of cells. A potentiometric