Zahra Premji, PhD Candidate

DEPARTMENT OF CHEMISTRY

CHEMISTRY 603

ANALYTICAL/ENVIRONMENTAL SECTION

SPEAKER:            Zahra Premji, PhD Candidate

DATE:                     Monday, January 30, 2012.

TIME:                      12:30 pm

PLACE:                  SB 324

TITLE:                    Development of a complex-based flow injection spectrophotometric method for determination of the herbicide pinoxaden in environmental samples.

ABSTRACT:           

Jasmin Shah, M. Rasul Jan, Mian Muhammad and Farhat-un-Nisa Shehzad.

Toxicological & Environmental Chemistry, 93(8), Sept 2011, 1547-1556.

A flow injection spectrophotometric method was developed for the determination of the herbicide pinoxaden (PXD). Pinoxaden is commonly used to control grass weeds found in wheat and barley crops, and works by suppressing the function of acetyl-CoA carboxylase thereby inhibiting fatty acid synthesis in these weeds. Globally, wheat production accounts for nearly half of all cereal production. PXD is harmful if inhaled, an irritant to eyes and the respiratory system. It is also harmful to aquatic flora and fauna and may cause long-term adverse effects in aquatic systems. It is therefore important to be able to determine PXD residues on harvested wheat and barley crops, in the soil used to grow these crops and in nearby aquatic systems.

Current methods are based on HPLC followed by UV detection or LC/MS/MS systems. While these systems function well, the proposed system has the potential to be a simpler, more precise and faster method. An added advantage is that the equipment required is less costly than that of the current methods. UV detection cannot be used directly even though PXD shows a strong absorbance at 300nm, because environmental samples contain by-products that also show absorbance in this region. However, the red iron hydroxamate complex that is formed when PXD reacts with hydroxylamine hydrochloride followed by iron (III) chloride shows a strong absorbance at 500nm, which is the basis of the proposed method.