Closure to “Buffetting of a Suspension Bridge by Storm Winds”

Abstract

removed, and the solution added to an equal volume of 12 M HCl (Ultrex II ultrapure reagent, Baker) and heated for 16 h at 100 8C in an organic-free sealed glass ampoule. This material was dried in vacuo to remove water, HCl and any volatile organic acids, then analysed by GC-MS as above. GC-MS was performed on a Thermoquest-Finnigan GCQ with an injector temperature of 240 8C and a DB-17ms-60m (J&W Scientific) column at an initial temperature of 70 8C increasing at 58 per min to 240 8C. Samples for HPLC were hydrolysed as above, and after drying, 100 ml of 10 mM pH 9.5 sodium borate was added to the tube which, after mixing, was re-dried in vacuo to remove volatile amines. The sample was analysed via the OPA/NAC fluorescent labelling and chromatography protocols of ref. 30 on a Hewlett Packard 1100 series HPLC with a Supelco Discovery C-18, 5 mm resin, 4.6 £ 250 mm analytical column with a 5 ml sample loop. This chiral label reacts with chiral amines (such as alanine and serine), forming diastereomers which can be separated by HPLC. However, differing absorptivities of these labelled diastereomers results in pairs of peaks where the areas of diastereomers are different even though there are equal amounts of the D and L forms. After a mild acid hydrolysis with the acid concentration diminished by a factor of 100 (0.06 M HCl), glycine and serine were measured at levels 3-4 times lower than for the standard hydrolysis procedure. Even hot water was adequate to release glycine, albeit an order of magnitude less than the standard hydrolysis.