Saturday, 15 July 2006

Fortified Water and Soils Extraction-Efficiency of Triclopyr (3, 5, 6- trichloro-2 pyridinyloxyacetic acid) with Four Organic Solvents.

Desh Duseja and Gary Kriner. Tennessee State Univ, Box 9543 Dept of Agricultrural Sciences and Institute of Agricultural and Environmental Research, 3500 John Merritt Blvd., Nashville, TN 37209-1561

Benzene (C6H6)has been extensively used as a solvent in various chemical analyses by gas chromatography (GLC). This is also true for GLC methods for triclopyr (3, 5, 6-trichloro-2-pyridinyloxyacetic acid) determination in soils and water. However, because of recent restrictions on benzene use, it has become imperative to investigate the use of alternate organic solvents for this purpose. Also, often needed ‘clean up' steps in the extractions utilize additional organic solvents. The objective of this study was to compare four organic solvents {benzene, toluene (TOL), chloroform (CHCL3) and methylene chloride (CH2CL2)} as to their efficiency in triclopyr extraction from deionized (DW) water fortified at 1.0 ppmw triclopyr concentration, and from two soil samples (labeled CN04 and NT48) fortified at 0.05 ppmw. Soil type was a Byler silt loam (Typic fragiudalf mixed, thermic). Two soil samples were collected from a field at the soil depths of 0-10 cm (CN48) and 10-20 cm (NT48), air-dried, crushed and sieved (0.2 mm). Their organic matter (OM) contents were ~ 1% (CN04) and ~ 2% (NT48); their pHs (1:2 water)were 6.9 and 6.7, respectively. A well known GLC method for this chemical (DowElanco Method, ACR 84.2) was used, except the clean up part of the method was omitted. The extracts were injected into an HP (Agilent Technologies) GC model 6890 (u-ECD detector) after appropriate preparation. Seven replications were used to calculate Method Detection Limit (MDL) with each solvent. GLC analyses recoveries from fortified water with C6H6 (101%) and CH2Cl2 (86%) were statistically significantly (p<0.01) higher than those from TOL (65%), and CHCl3 (67%). However, the MDLs were also statistically significantly (p<0.01) better for C6H6 (0.139) and CHCl3 (0.143), relative to CH2Cl2 (0.283) and TOL (0.244). It seems that CH2CL2 will be a preferable alternate solvent for triclopyr water analysis by this method. Benzene gave 101 average recovery, whereas TOL, CHCL3 and CH2CL2 recoveries were 104, 102, and 112%, respectively, from a CN04 soil (OM <1%). From the NT48 soil (OM ~ 2%), recoveries were: 102% (C6H6), 146% (TOL), 118% (CH2CL2) and 88% (CHCL3). MDLs were comparable for the four three solvents --- 0.049, 0.067, 0.042 and 0.052 ppmw for C6H6, CH2Cl2, CHCL3 and TOL, respectively. CH2Cl2 and CHCL3 seem to be alternate solvents of choice for these soils even in higher OM soils. ‘Wet' (50% moisture w/w) soils extraction resulted in inconsistent triclopyr recoveries (average 111.5%), ostensibly due to interference in GC peak areas on GC (ECD detector). However, overnight oven-drying (105-1100C) of fortified soils tended to remove this interference resulting in consistent recoveries of around 102%.

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