Improved spectrophotometric determination of osmium(VIII) with 4-(2-pyridylazo) resorcinol in mixed surfactants

The colour development between 4-(2-pyridylazo)-resorcinol(PAR) and osmium(VIII) in the presence of cationic and nonionic surfactants in a weakly acidic medium was more stable and reproducible than in the absence of surfactant (PAR-alone method). An improved spectrophotometric determination of osmium(VIII) with PAR was investigated in the presence of mixed surfactants of N-hexadecyltrimethylammonium chloride (HTAC) and Brij 58 [poly(oxyethylene)lauryl ether] as cationic and nonionic surfactants at pH 6.0-7.2. The calibration graph was linear in the range 0-110 microg/10 ml osmium(VIII), and the apparent molar absorptivity was 2.4 x 10(4) l.mole(-1).cm(-1) with a Sandell sensitivity of 0.0079 microg/cm(2) osmium(VIII).     

(Triisopropylsilyl)acetaldehyde acetal as a novel protective group for 1,2-diols

(Triisopropylsilyl)acetaldehyde dimethyl acetal (TIPS-ADMA) was synthesized from chlorotriisopropylsilane in three steps. Cyclic and acyclic 1,2-diols can be transformed to (triisopropylsilyl)ethylidene acetals (TIPS-AA). Removal of the acetal by LiBF₄ regenerates the starting diol in excellent yield even in the presence of an acetonide of 1,2-diol. The TIPS-AA group can survive under the deprotection conditions of the acetonide in acetic acid at 80 °C. Selective protection of 2,3- and 4,6-diols for O-methyl d-mannoside with TIPS-ADMA and selective deprotection of the acetals have been achieved.     

Concentration and degradation of hyaluronic acid in knee synovial fluid from carrageenin-induced rabbit arthritis

The concentration and degradation of hyaluronic acid in the synovial fluid of carrageenin-induced arthritic joints of rabbits was studied. A 0.5-ml volume of 1% lambda-carrageenin was intra-articularly injected three times into a right knee joint, and saline into a left. After 5 d from the last injection, inflammatory changes were observed in the synovial membrane and synovial fluid, but not in the articular cartilage. In the inflammatory synovial fluid, lipid peroxide content, phosphatase activity and cell counts were significantly increased, but the copper concentration was not changed. Concentration of polymeric hyaluronic acid and total hyaluronic acid were determined by high-performance liquid chromatography using gel-permeation columns. Total hyaluronic acid was appreciably decreased in the inflammatory fluid. The polymeric hyaluronic acid determined was 38% of the total hyaluronic acid in the inflammatory fluid and 74% in the control fluid. This suggests that in the inflammatory fluid, molecular weights of hyaluronic acid are distributed in the broader range. The concentration of chondroitin sulphates was similar in both the inflammatory fluid and the control fluid, but the content ratio of chondroitin sulphates to hyaluronic acid was higher in the inflammatory fluid. In the inflamed synovial membrane, synthesis of hyaluronic acid as measured by incorporation of [14C]glucosamine into glycoconjugates was increased by about twice that in the control membrane.