UV–visible spectral identification of the solution-phase and solid-phase permanganate oxidation reactions of thymine acetic acid

2004 ◽  
Vol 14 (5) ◽  
pp. 1313-1315 ◽  
Author(s):  
Chinh T. Bui ◽  
Lien A. Sam ◽  
Richard G.H. Cotton
2019 ◽  
Vol 31 (11) ◽  
pp. 2527-2531
Author(s):  
St. Fauziah ◽  
N.H. Soekamto ◽  
P. Budi ◽  
P. Taba

Molecularly imprinted polymers (MIP) as an adsorbent has been synthesized using β-sitosterol as molecule template on free radical polymerization reaction. The capacity and selectivity of the adsorption from MIP to β-sitosterol was studied in this study. The β-sitosterol concentration in the adsorption-desorption test and the MIP selectivity test were analyzed by UV-visible and HPLC. The MIP obtained from the synthesis results in a high adsorption capacity. Based on the Freundlich adsorption isothermal equation, the adsorption capacity (k) was found to be 1.24 mg/g. The MIP can adsorb 100 % β-sitosterol while cholesterol was only 3 %. The MIP is most selective to β-sitosterol, therefore, has high potential to apply as adsorbent at solid phase extraction method to isolate β-sitosterol from sample extract.


1998 ◽  
Vol 39 (26) ◽  
pp. 4591-4594 ◽  
Author(s):  
Konrad H. Bleicher ◽  
James R. Wareing

2011 ◽  
Vol 89 (8) ◽  
pp. 939-947 ◽  
Author(s):  
Irena Mihailova ◽  
Dimitar Mehandjiev

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.


2008 ◽  
Vol 27 (1) ◽  
pp. 25 ◽  
Author(s):  
Aleksandra Nestorovska-Krsteska ◽  
Meri Mirčeska ◽  
Jean-Jacques Aaron ◽  
Zoran Zdravkovski

An HPLC-UVDAD method for determination of dimethoate, 2,4-dichlorophenoxy acetic acid (2,4-D), mecoprop (MCPP) and linuron in environmental waters was developed. The water samples were concentrated and extracted by a solid phase extraction (SPE) method on Bond Elut PPL cartridges. After extraction the investigated compounds were separated on Stability RP Pesticides chromatographic column using mobile phase composed of acetonitrile- water-acetic acid in volume fractions of 39:59:2 and flow rate of 0.7 mL/min. Ultraviolet absorption detection was carried out for dimethoate, 2,4-D and MCPP at 229 nm, and for linuron at 249 nm. Recoveries made from 500 mL of drinking waters using solid phase extraction ranged between 64.3–92.1 %. The method was applied to environmental waters in Macedonia that receive runoffs from agriculture lands. The levels of pesticides under study ranged between 0.31 μg/L and 7.05 μg/L, depending on the compound and sampling period.


Food systems ◽  
2019 ◽  
Vol 1 (4) ◽  
pp. 19-26
Author(s):  
I M. Pochitskaya ◽  
A. P. Laktionova ◽  
V. L. Roslik

The results of the study of the composition of volatile compounds of rennet cheeses are presented. Sample preparation was performed using Supelco’s solid-phase microextractor, including a special fiber material coated with a layer of divinylbenzene-carboxene-polydimethylsiloxane «DVB / Carboxen / PDMS StableFlesh ™». Using gas chromatography with mass-selective detection, about 400 aroma-forming components were detected, among which 39 compounds were identified, which form the basis of the flavor profile of cheeses. The main flavor descriptors for all cheeses are: propionic, butyric, and caproic acids, acetoin, methyl amyl ketone, 2-nonanone, and limonene. It has been established that the profile of volatile components for cheeses various ripening periods, has significant differences. Thus, for semi-hard cheeses made using propionic acid microorganisms, the most characteristic components are acids — propionic and butyric, as well as compounds of the terpene series o-cymene and β-pinene. For semi-hard cheeses of the Dutch group (formed from the layer), with maturities from 20 days to 3 months, the terpene compounds and esters are the most significant, whereas for superhard cheeses with a maturity of more than a year, the main components affecting the aromatic profile are butyric and caproic acids, 2-heptanone and limonene. Semi-hard and hard cheeses with ripening periods from 3 to 6 months are characterized by a high content of caproic and butyric acids, as well as by the presence of such aromatic substances as limonene and acetic acid ethyl acetate (hexyl acetate). Semi-hard cheeses, which are molded in bulk, with maturities from 10 days to 3 months contain acetoin, caproic acid, as well as significant quantities of the same limonene and hexylacetate.


1992 ◽  
Vol 57 (8) ◽  
pp. 1707-1718
Author(s):  
Wolfgang Voelter ◽  
Gerhard Breipohl ◽  
Chryssa Tzougraki ◽  
Eveline Jungfleisch-Turgut

The solid phase synthesis of an amidated somatostatin analogue based on the principle of differentiated acidolysis is described. The acid labile and smoothly cleavable t-Bumeoc moiety (1% TFA/DCM) is used for temporary Nα-protection of D- and L-amino acids and [4-[[[9H-fluoren-9-yl-methoxycarbonyl]amino](4-methoxyphenyl)methyl]-2-methylphenoxy]acetic acid, attached to an aminomethylated polystyrene resin is used as acid sensitive linker of the solid carrier which releases the peptide in its amide form by treatment with TFA. Its preparation is described in detail.


Sign in / Sign up

Export Citation Format

Share Document