Due to excessive use in agriculture, organophosphorus (OP) pesticides are one of the most widely occurring pollutants in the environment. They inhibit acetylcholinesterase (AChE) activity and cause serious nerve problems in animals and humans, particularly affecting the nerve-muscle junction. Sensitive OP detection and monitoring of degradation are the two challenges of analytical chemistry. Broadly, two detection methods have evolved: Gas chromatography (GC) hooked to a suitable detection system as the compounds are volatile in nature, and more recently, the immobilized biocatalyst systems, detecting by AChE inhibition chemically linked to spectrophotometric or electrical conductance changes. Traditionally GC-mass spectroscopy (GC-MS) and its improvised version, ion trap GC-MS/MS have been used as highly sensitive detection methods for OP. Due to the non-availability of proper standards, the oxidizing products of native OPs, particularly the oxon compounds remained undetected. A more recen
t approach is based on triple quadrupole mass spectroscopy as the detection device for GC (GC-QqQ-MS). This method helps detect traces of a large number of OPs and also the derivatives in fruits and vegetables before being marketed. This is based on a principle that once the pesticides are separated by GC they are ionized both positively and negatively under ion trap and then fragmented in QqQ MS in MS/MS mode. The structure of OP and products can be deduced from the fragmentation pattern in the spectrum. It is possible to quantify the OPs so that biosafety levels can be marked. Although chlorination is practiced for water purification, the process leads to oxidation of thiono (P=S) form of OP to active oxon forms (P=O), which are more harmful. Simultaneous detection of parental and oxon forms of OPs was possible by GC-MS if the water samples were passed through solid-phase extraction prior to GC-MS. In SPE-GC-MS special DB-5 column was used to separate the parental and oxon forms of the OP.