OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

RE: Teleconference between Dow AgroSciences (DAS) and EPA to Discuss the 

Challenges DAS Has Encountered with the Flux Study Analytical Method

List of Documents

1. Meeting Summary Page 1

2. Meeting Attendees Page 1

3. DAS Talking Points for the Meeting Page 2

1. Meeting Summary

On Thursday, May 10, 2012, EPA’s Office of Pesticide Programs met with Dow AgroSciences 

(DAS) via teleconference and discussed the difficulties DAS had encountered with the flux study 

analytical method, what DAS had done to address the difficulties, and DAS provided EPA with a 

revised study submittal date of July 1, 2012.

2. Meeting Attendees

DAS attendees

Lisa Buchholz, Analytical Chemistry Lab Leader

Joe Gesell, Analytical Chemist

Mike Hastings, Analytical Chemist

Pat Havens, CHP Study Director for Field Fate & Effects Group

Darin Lickfeldt, Regulatory Manager

EPA attendees

Jeff Dawson, HED

Wade Britton, HED

Rochelle Bohaty, EFED

Charles (Chuck) Peck, EFED

Tom Myers, PRD

Joel Wolf, PRD
Direct Flux Measurement of Chlorpyrifos and 

Chlorpyrifos-Oxon Emissions Following Applicaof Lorsban Advanced Insecticide to Alfalfa

Analytical issues and progress review10-May-2012
Agenda

• Introduction • Study purpose• Field conditions overview• Protocol review comments• Analy pp tical method issues and proposed solu• Next steps
Introduction

• Required by Registration Review DCI, Sept. 

...providing confirmatory data on the volatility and oxon fo

under actual use conditions, information on the percentapplied chlorpyrifos that volatilized and converts to oxoproperly designed information on flux This information properly designed information on flux. This information used to estimate both near field and longer range transexposures. 

• Protocol submitted for review May 6, 2011• EPA comments rec’d Sept 9, 2011
Study purpose and design

• Field flux study - not a monitoring study• Near Los Banos, Merced CA (Central Valley) Merced, CA (Central Valley)• Established alfalfa

– Foliar application

• Soil volatility unimportant & understood

• Aerodynamic flux method• Indirect (off-plot) for first sampling period (2 hrs

– Indirect flux via back-calculation with air dispers
Field conditions

•Application 0.94 lb/acre CHP

•2 pints Lorsban Advanced*/acre

•~175 x 175 m (7.6 acres)•Samples and met @ 0.15, 0.33, 0.55, 0.9, 1.8 m•Indirect ~100 ft offplot•Temps

•Mid 60s-70s (night)•High 90s -100 (day)

•20% (day) -70% (night) RH

•Winds calm to 7-10 mph•No precip

* Trademark of Dow AgroSciences LLC
Protocol review responses – details will be in fina

• Protocol was GLP-compliant and audited• Formulation choice – Lorsban Advanced is commercial standard for DA• Field size/sampg g lin hei

ghts/fetch

– Majewski ref – “rule of thumb”

• Lower sampling heights used preferentially @ 90cm => 90m fetch => 1⁄2 field w

• Indirect sampling only in 1st 2 hr period – precedent in earlier protocols • Bare soil plot not included 

– previous work shown not significant

• Surrounding timings (2 weeks) & distance

– Atmospheric half-lives (recent photoreactor results) ~ 6hr for parent an– Plus have pre Plus, have pre

-application samples

• Duration of sampling – “extend until harvest”

– Not a dissipation or residue study, duration sufficient to define flux pat
Analytical method issues

• Initial method based on procedure from U of 

study (Fenske, et al 2009) et al. 2009)

• Significant challenges with implementing me

reported

• Minor modifications to fit DAS workflows and 

previ i ith “ i t b ” th d 

ious experiences

with “

air tu

be” methodo

implemented with little success
Challenges

• Ion suppression

– Co-eluting species from XAD-2, PUF lead to significant ion suppression of 

LC/MS signals

• Low Oxon recoveries encountered when air was pulled through tube to 

actual air sampling

– Ion suppression hindered identification of low Oxon recoveries from XAD-– Experiments proved low recoveries were not due to analyte breakthrough

• Significant efforts made to increase Oxon recovery from XAD-2 tubes

– Different solvent systems and extraction technologies were evaluated (sha

Different solvent systems and extraction technologies were evaluated (shaand ASE)

• Evaluation of Oxon extraction methods/solvents pointed to Oxon degra

and not lack of extraction
Challenges – Cont’d

• Degradate identification efforts using non 14C labeled standards sugge

breakdown product was TCP

• 14C Oxon was sourced to confirm TCP as degradate

– Definitive ID complicated by low TCP’s low MS sensitivity (>10 less sensit– N CHP t b lit l t i th i i it f TCP d t d 

Numerous CHP meta

bolites

elute i

n the

vicinity 

of TCP and most produce 

fragments (MS/MS and in source fragmentation)

• 14C Oxon used to produce TCP in situ to facilitate development of extra

from XAD-2 air tubes

– Solvents that adequately extract CHP and Oxon are not suitable for TCP– 1:1 ACN/MeoH solvent system identified that adequately extracts all three 
Challenges – Cont’d

• Significant challenges in incorporating TCP into LC/MS method d

– Lack of TCP LC/MS sensitivity required optimization of HPLC columns 

phases to increase sensitivity and allow the three compounds to be run 

assay

– Change in extraction solvent system led to different co-extracted specie

tubes which again caused suppression to all three analytes

• Sourced stable isotope internal standards to address ion suppres

issues

• 3 analytes individually spiked to XAD-2 air tubes to:

– Demonstrate extraction efficiency– Check for degradation of CHP to the oxon & TCP metabolites and meta

stability during air sampling (note: UWA did not look at TCP)
CHP Air Tube MD Data

Sample (250 ng spiked)

Average

% Recovered

(expressed as CHP

equivalents)

Total

% recov

TCP OXON CHP

CHP air tube flow 0hrs 0 0 81 81

CHP air tube flow 2hrs 1.1 0.5 90.5 92

CHP air tube flow 16hrs 4 3 83 89
Oxon Air Tube MD Data

Sample (250 ng spiked)

Average

% Recovered

(expressed as OXON

equivalents)

Total

% recovered

TCP OXON CHP

Oxon air tube flow 0hrs 16 81 0 97

Oxon air tube flow 2hrs 63 26 0 88

Oxon air tube flow 16hrs 69

9

0 78
TCP Air Tube MD Data

Sample (250 ng spiked)

Average

% Recovered

(expressed as TCP

equivalents)

Total

% recovered

equivalents)

TCP OXON CHP

TCP air tube flow 0hrs 85 0 0 85

TCP air tube flow 2hrs 77 0 0 77

TCP air tube flow 16hrs 72 0 0 72
• DAS Proposal for data reporting in Flux stud

– CHP residues to be reported without convers

factors (low formation of Oxon and TCP from spiked air tubes)

– Oxon residues to be reported as the sum of 

residues and TCP residues (after conversion equivalents)
Next steps

• NOTE: No study samples analyzed yet – all 

method development/validation

• Study samples will take a solid 2 weeks for a• A l ti l it Analytical write-up d QA an• Flux calculations• Field + flux writeup• Final QA
Questions?