degradation ofOPEsinwater-isopropanol(50:50)extractsof
swabsusedforsamplecollectionfromdifferentsurfaces.Itwas
shown thatsuchmixtureprovidesthebestextractionofvarious
types ofinorganicandorganicexplosives [20]. However,asaresult
of elevatedviscosityofthismixturetheFIAsysteminthisstudy
need tooperateatpressureshigherthanthosenormallyprovided
by peristalticpumps.Also,initialexperimentsusingperistaltic
pumps demonstratedpoorstabilityofthesiliconetubingwhenin
contact withsolutionsofisopropanol,hydrochloricacidandso-
dium hydroxiderequiringthefrequentreplacementofthetubing
and leadingtopoorreproducibilityofdata.Forthisreasona
pneumatic FIA-CLsystemconsistingof five pressurelinesequip-
ped withprecisionlow-pressureregulators(maximumoperating
pressure0.2MPa)wasconstructedasshownin Fig. 1.
The acidfumesandtheheatgeneratedfromthereactionbe-
tween concentratedHClandNaOHwasapracticalchallengein
selecting theacidandbaseconcentrationsinthisstudy.Ad-
ditionally,thesolubilityofNaCl,formedasaproductoftheneu-
tralisation reactionofHClandNaOH,inisopropanolisverylow
(0.013gg1 at 23.5 °C). Toavoidfrequentregulatormalfunction
and systemblockageduetoNaClprecipitation,50:50v/vdeio-
nised water–isopropanolmixturewasusedtocarrythe100 mL
sample plugintothecheminertmixingchamber.Thesystemop-
eratedoptimallywithoutblockagefromNaClprecipitationand
systemmalfunctionfromacidfumesandexcessiveheatwhen32%
HCl (concentrated)and18%NaOH(w/v)wereused.