Anhydrides, HPLC analysis

The key to a controlled molecular weight build-up, which leads to the control of product properties such as glass transition temperature and melt viscosity, is the use of a molar excess of diisopropanolamine as a chain stopper. Thus, as a first step in the synthesis process, the cyclic anhydride is dosed slowly to an excess of amine to accommodate the exothermic reaction and prevent unwanted side reactions such as double acylation of diisopropanolamine. HPLC analysis has shown that the reaction mixture after the exothermic reaction is quite complex. Although the main component is the expected acid-diol, unreacted amine and amine salts are still present and small oligomers already formed. In the absence of any catalyst, a further increase of reaction temperature to 140-180°C leads to a rapid polycondensation. The expected amount of water is distilled (under vacuum, if required) from the hot polymer melt in approximately 2-6 h depending on the anhydride used. At the end of the synthesis the concentration of carboxylic acid groups value reaches the desired low level. 

Acylation of a / -configurated axially chiral diamine 1 containing a primary amino group with equimolar amounts of monocyclic anhydrides 2 and 4 in toluene or dichloromethane at low temperatures gives the amides 3 or 5 with good diastereoselectivity 10°. Diastereomeric ratios were determined by HPLC analysis after conversion to the methyl esters with diazomethane absolute configurations are based on chemical correlation. 

The geometry of the enolate intermediate was investigated by trapping experiments. When 23 (93% ee) was treated with potassium hydride and acetic anhydride in the presence of 18-crown-6, E-enol acetate 25 (59%) and its Z-isomer 26 (6%) were obtained together with the recovery of 23 (27%). The ee of the recovered 23 was unchanged. These observations indicate that the -enolate is the major intermediate under conditions of kinetic control. HPLC analysis of 25 with a chiral stationary phase indicated the existence of a pair of enantiomers (Figure 3.3a). Rapid interconversion between... 

Hydroxymethyl-8-methoxy-1,4-benzodioxane in benzene cxjntaining acetic anhydride by treatment at ambient temperature with the enzyme. Amano P-30 afforded after work-up at 50% conversion (monitored by HPLC analysis) a 44% yield of (S)-2-hydroxymethyl-8-methoxy-1,4-benzodfoxane (e.e.83%) (ref.33). 

Tables Deposition of collagen-glycosaminoglycan conjugates on poly(octadecen-a/f-maleic anhydride)-coated substrates. Fibrillogenesis and immobilization of fibrillar collagen (1.2 mg/ml) was performed for 2 h at 37 ° C in the presence of heparin and hyaluronic acid (0.4, 1.2 and 5.0 mg/ml, respectively). Thickness of the layers was determined ellip-sometrically using the refractive index of 1.6035 for the dried collagen layer. The collagen amount was determined by amino acid-based HPLC analysis after acidic hydrolysis of surface-bound collagen...

Shang et al. [5] used ASE for the extraction of NP and NPEO from estuarine sediments. A sample of 15-25 g was extracted three times using hexane/acetone at 100°C and 103 atm. This was followed by a clean-up step using CN-SPE. A blank sample was extracted between all samples to avoid contamination. Hexane/acetone was also used in the ASE method for alkylphenols and NPEO by Heemken et al. [12]. Extraction conditions for samples of 0.5-1 g were 100°C, 150 atm, with a static extraction step of 15 min, and a rinse step with 20 mL solvent. After a clean-up by HPLC, the analytes were derivatised with heptafluorobutyric acid anhydride for GC analysis. 

Alkyl halides, alkyl sulfonates and other alkylating agents have also been subject to scmtiny in spheres other than pharmaceuticals, such as in environmental analysis. Various approaches have included two-step SPE, derivatisation with trifluoroacetic anhydride followed by GC/MS (for cyclophosphamide and its analogues in sewage water) SPE on surface water to isolate the antineoplastic agents carmustine, chlorambucil, cyclophosphamide and melphalan for LC-UV and LC-fluorescence measurements and derivatisation of alkyl halides and epoxides with 4-nitrothiophenol followed by HPLC-UV detection (claimed to be better than NBP derivatisation). A patent exists for a field test kit for mustard gases in military use based on NBP derivatisation. 

A quantitative HPLC method for the analysis of sphingolipids as their perbenzoyl derivatives was first developed for ceramides (5). Ceramides can be conveniently derivatized with benzoic anhydride in pyridine (3 hrs at 110°C) and the products formed have been utilized for the quantitative analysis of NFA and HFA ceramides in normal and Farber s disease tissue. Iwamori and Moser also utilized this procedure for the analysis of ceramides in Farber s disease urine (6). More recently Iwamori and Moser (7) established that the ceramide derivatives formed by reaction with benzoyl chloride or benzoic anhydride are analogous to those formed with cerebrosides. They also characterized the behavior... 

The development of a normal-phase HPLC method was warranted due to the presence of phthalic anhydride, which is unstable in water. Analysis in organo-aqueous solvent systems that are used in RPLC would lead to an on-column reaction forming the respective carboxylic acid degradation product. Figure 5-5 shows the chromatogram obtained for the separation of 9,10-anthraquinone from the reactants and impurities on a silica column. The method was successfully applied to monitor the reaction conversion and also to determine the stability of 9,10-anthraquinone at the specified storage conditions. 

Chemical Analysis. Gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) techniques were used to analyze 4-chlorophenol and its oxidation intermediates. For GC-MS analysis, the samples were acetylated in pyridine. The samples were first evaporated to dryness. Then 200 xL of pyridine and 200 (xL of acetic anhydride were added to the dry residue. The samples were heated at 65 °C for 2-3 h to ensure the complete acetylation reaction, and then gently evaporated to dryness in a nitrogen stream. Finally, the residue was redissolved in 0.1 mL of hexane for GC analysis. A GC (HP model 5890) equipped with mass selective detector (HP model 5971) and SPB-5 capillary column (Supelco Co., PA., 25- X 0.2-mm i.d. X 0.33-p.m film thickness) was used. To separate different intermediate products, various oven-temperature programs were performed. The GC-MS interface line was maintained at 300 °C. The mass-... 

The most commonly applied methods for the analysis of polyamines in erythrocytes make use of amino acid analyzers and HPLC techniques. A capillary gas chromatographic method with nitrogen-phosphorous detection was applied to the simultaneous determination of 1,3-diaminopropane, putrescine, cadaverine (Cad), spermidine (Sd), and spermine (Sp) in human erythrocytes. Blood samples, collected by venipuncture into EDTA containing Venoject tubes, were subjected to the removal of plasma by centrifugation and erythrocytes were washed three times with two volumes of 0.9% NaCl. The stability of polyamines in erythrocyte suspensions was also investigated. Quantification of polyamines was done by comparing the peak-area ratio of each analyte and its internal standard with that of the standard. The polyamine samples were eluted with 0.1 M hydrochloric acid solutions. The eluate was evaporated to dryness at 120°C under a stream of air and 200 each of acetonitrile and heptafluorobutyric anhydride were added. The isolation of derivatives... 

MDI may be analyzed by GC, GC/MS, TLC, and HPLC. The latter technique is followed for air analysis using an UV detector. Air is passed through an impinger that contains 1-(2-methoxyphenyl)piperazine solution. The derivative is treated further with acetic anhydride and analyzed (NIOSH 1984, Method 5505). 

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