Conventional and thermal lens spectrophotometric determination of p-aminobenzoic acid and arylamine diuretics previous azodye formation in a micellar medium

The determination of the diuretics hydrochlorothiazide, bendroflumethiazide and furosemide by both conventional and thermal lens spectrophotometry (TLS, 100 mW of pump power at 514.5 nm) following previous hydrolysis, diazotization and coupling with N-(naphthyl)ethylenedine (NED) in a sodium dodecyl sulphate (SDS) micellar medium of pH approximately 1 was studied. p-Aminobenzoic acid (PABA) was used as a model compound to optimize the derivatization procedures. 3-Substituted indoles, such as 5-hydroxyindole-3-acetic acid and tryptophan, gave N-nitroso derivatives which interfered with the determination of the diuretics in urine. The derivatized diuretics in urine were separated using HPLC with a Spherisorb ODS-2 C(18) column, and a 0.1M SDS mobile phase containing 5% n-propanol and 0.001M sodium dihydrogen phosphate (pH 3). The diuretics gave limits of detection (LODs) of ca. 5 x 10(-9)M for the TLS procedure. The LODs were 20-50-fold higher for the corresponding spectrophotometric procedure.     

An Investigation of the N-Arylsulfonylation of 2-Azetidinones

N-Arylsulfonylation of 2-azetidinones can lead to the diastereoselective formation of oligomerization products. However, a simple increase of arylsulfonyl chloride concentration minimized oligomerization and allowed preparation of 1-arylsulfonyl-2-azetidinones in good yield.     

Spatial energy estimates in dynamical problems for a semi-infinite piezoelectric beam

The behaviour of the total energy for a semi-infinite piezoelectricbeam, with uniform or variable cross-section, in dynamical conditionsis investigated. Precisely, we obtain some estimates in termsof the data for the energy of the portion of the body at distancegreater than z from the base and for its norm in L¹(0,t) (wheret is an arbitrary positive time). We obtain some estimates whichdepend on the initial data if t z/V (where V is a computablepositive material constant); if t > z/V, by using also theKorn inequality, we show that the bounds depend on all the data.Under mild hypotheses on the initial data we derive the asymptoticbehaviour of the energy as z +. All possible combinations ofboundary conditions are examined and the kind of the estimateis formally the same for all the problems whether the beam isa cylinder or not.