Determination of ortho-phthalaldehyde in air and on surfaces

Three sampling and analytical methods have been developed and evaluated for ortho-phthalaldehyde ( OPA): ( 1) an HPLC-UV method for OPA in air, ( 2) a fluorimetric method for OPA on surfaces, and ( 3) a colorimetric method for OPA on surfaces. ( 1) The air sampler contains 350 mg of silica gel coated with 1 mg of acidified 2,4-dinitrophenylhydrazine ( DNPH). Air sampling may be conducted at 0.03 to 1.0 L min(-1) for periods up to 8 h. Samples were eluted with ethyl acetate, and the eluents were allowed to stand for 72 h. Analysis was by high performance liquid chromatography ( HPLC) with a UV detector set at 369 nm. An unusual phenomenon was the observation that the stability of the sample on a sampler at 3 degrees C tends to decrease as the total quantity of OPA collected on the sampler decreases. Elution of the samples within 24 h of air sampling is required. The detection limit ( LOD) is approximately 0.02 mu g of OPA per sample. OPA on surfaces may be collected with strips cut from a sheet of polyvinyl alcohol ( PVA wipe). ( 2) In the surface wipe method with analysis by fluorescence measurement, the strips of PVA wipe were placed into dimethyl sulfoxide. An aliquot was treated with aqueous N-acetyl-L-cysteine and ethylenediamine. Analysis was performed with a portable fluorometer ( excitation and emission wavelengths 365 nm and 438 nm, respectively). The LOD is 0.2 mu g per sample. ( 3) In the surface wipe method with visual colorimetric detection, the strips of PVA wipe were placed into 30 : 70 acetonitrile : water. An aliquot was treated with N-(1-naphthyl) ethylenediamine in 0.1 M sulfuric acid. After color development, the LOD is approximately 48 mu g per sample. These methods have been field tested in a hospital.