Page 13 - Volume 3, Issue 1, January 2010

Tsakirakis

et al.

12

ing the bag 50 times.

Quality control samples were prepared

with fortification of matrices on each appli-

cation day. Thus, three samples of different

types of dosimeters (outer, inner fabric, in-

ner and outer gloves, caps and XAD-2 tubes)

were fortified at two fortification rates. The

fortification solution was taken directly from

the nozzle of the tank in the field. The field

fortified samples were exposed to the envi-

ronmental conditions for the duration time

of the application. During this period the

XAD-2 tubes were left attached to air pumps

operating at an airflow rate of 2.0 l/min. Ad-

ditionally, field blank samples for each do-

simeter type were treated as the fortified

samples.

For the accurate determination of the

actual spray solution concentration, three

volumetric flasks of 10 ml each were forti-

fied in the field concurrently with the dosim-

eter fortification. The flask fortification vol-

ume was 1 ml taken from the spray solution

used for the application.

Analytical Part

A fully validated, in-house analytical

method was applied for the determination

of iprodione in the different types of dosim-

eters and in quality control samples. For the

analysis of all field and quality control sam-

ples used in the study, the principal steps of

themethod included sample extractionwith

n

-hexane, extract concentration, filtration

and Gas Chromatography determination us-

ing Electron Capture Detector (GC-ECD) and

pendimethalin as internal standard.

The

n

-hexane solvent, P-R grade, was pur-

chased from Merck (Darmstadt, Germany).

Iprodione (99.3 % pure) and pendimethalin

(98.4% pure) analytical standards were pur-

chased from Sigma-Aldrich (Steinheim, Ger-

many). The commercial iprodione SC formu-

lation (Rovral 50 SC, 500 g a.s. iprodione/l)

was purchased from Basf Agro Hellas (Sin-

dos, Greece). For the filtration of extracts,

PTFE (polytetrafluoroethene) 0.45 μm sy-

ringe filters (Acrodisc, p/n 4219T, PALL Dreie-

ich, Germany) were used. Stock solutions of

iprodione analytical standard (1000 μg/ml)

were prepared in P-R grade

n

-hexane and

stored at -18°C. Working solutions of the an-

alytical standard (100, 10 and 1 μg/ml) were

prepared by further dilution of stock solu-

tion in

n

-hexane and stored at -18°C.

Iprodione residues were extracted from

the different types of dosimeters with

n

-

hexane in high density polyethylene con-

tainers on an overhead shaker for 45 min at

200 rpm. The extraction volumes used were

3.5 l for outer garment parts, 1.5 l for inner

garment parts and 600 ml for caps and for

inner gloves. The extraction of nitrile gloves

was performed in the field using 400 ml

n

-

hexane, as described above. The extraction

of the XAD-2 tubes (extraction volume 10

ml) was carried out in 30 ml screw cap vials

after disassembling of the tube and trans-

ferring the absorbent layer material to the

extraction vial, and placed on the overhead

shaker for 45 min. The actual concentra-

tion of iprodione in the field spray solution

(FST) was determined from the field forti-

fied flasks after solvent (water) evaporation

to dryness and re-dissolving of the dry resi-

due in

n

-hexane.

Depending on the initially measured ip-

rodione concentration in the analyzed sam-

ple extracts, the extract was either concen-

trated in a rotary evaporator or diluted with

hexane to obtain a concentration into the

range of the calibration curve (0.1-0.9 μg/

ml). The internal standard pendimethalin

was added at 0.04 μg/ml to the final solu-

tion, which was filtered prior to GC injection

(injection volume 1 μl).

Gas Chromatography

The chromatographic determination

was performed with an Agilent GC 6890N

instrument (Thermo-Finnigan Italia, Roda-

no, Italy), equipped with a split/splitless in-

jector (splitless mode), with an ECD and au-

tosampler (Gerstel MPS2-Twister) 2000).

Chromatography parameters are presented

in Table 2.

Analytical Method Validation

The analytical method validation includ-

ed study of linearity, accuracy, precision,