DETERMINATION OF ACETIC AND FORMIC-ACID IN LEAD CORROSION PRODUCTS BYION-EXCHANGE CHROMATOGRAPHY

Ion-exchange chromatography using a Diones DX100 ion chromatograph was used to determine the concentrations of acetic and formic acid in cor rosion products from the underside of lead roofs on historic buildings in the UK. Acetate and formate ions were extracted from the lead corr osion products by shaking in 2 mn borax solution, Organic acids were s eparated using a Diones AS4A-SC ion-exchange column and 2 mM borax sol ution as eluent and detected by chemically suppressed conductivity det ection. A linear calibration curve was obtained over the range 1-100 p pm for acetate and formate ions with correlation coefficients r(2) = 0 .9987 and 0.9997 and limits of detection of 0.12 and 0.10 ppm, respect ively, with a 25 mm(3) sample volume. The RSD of a mid-range standard (10 ppm, six replicates) was 1.4% for acetate and 1.0% for formate, Th e recoveries of acetate and formate ions from the lead oxidation produ cts were 97.5 and 98.6%, respectively. High concentrations of organic acids were found in samples collected from many of the sites which suf fered severe underside lead corrosion, confirming a wider role of orga nic acids in the accelerated breakdown of lead roofs.