Selective Separation and Preconcentration of Caffeine from Natural and Pharmaceutical Products using New Polyurethane Foams

Abstract Two polyurethane foam-based sorbents (PUF) were synthesized by imprinting and grafting techniques and examined for selective separation and preconcentration of caffeine (CAF) in some pharmaceutical products and in black tea. Molecularly imprinted PUF was synthesized based on hydrogen-bonding interactions between CAF and alizarin yellow G (AYG) and subsequent polymerization into PUF. The static experiments indicated optimum sorption conditions at pH=6.5 and 5.5 for imprinted PUF (AY-IPUF) and grafted PUF (AY-GPUF), respectively. In the online experiments, the suitable preconcentration time was found to be 40 and 20s for (AY-IPUF) and (AY-GPUF), respectively, at a flow rate of 1.75 mL.min-1. Desorption of CAF has been affected by passing 500 µL of 0.05, 0.01 mol.L−1 HCl eluent onto (AY-IPUF) and (AY-GPUF), respectively. The online methods have provided satisfactory enrichment factors of 8.4 and 10.5 for (AY-IPUF) and (AY-GPUF), respectively. The time consumed for preconcentartion, elution and determination steps was 1.48 and 1.05 min, thus, the throughput was 42 and 57 h-1, for (AY-IPUF) and (AY-GPUF), respectively. The developed sorbents were studied for the determination of CAF in pharmaceutical samples which will be helpful to minimize caffeinism. Finally, in silico bioactivity, ADMET and drug-likeness predictive computational studies of caffeine were also carried out

[Evaluation of concentration methylene diphenyl diisocyanate [MDI] in the polyurethane industries of Iran]

MDI [Methylene Diphenyl Diisocyanate] is a high tonnage product, which comprises about 90% of the total diisocyanate in the market. Polyurethanes are produced by reacting diisocyanate with polyols and other chemicals. They are known as respiratory tract and skin sensitizers and are the most common cause of occupational asthma in the world [NIOSH 1994]. On this subject, evaluation of MDI concentration in the polyurethane factories by HPLC, and is worthy to determine its pollution level. All sampling methods have some limitation, therefore, this survey the method of NIOSH 5522 has been used as a standard sampling and analyzing method t then, we utilize SPSS V.13 software, for our data to be analyzed for statistical discussion. Results showed that all of the polyurethane industries under this study have high concentration, rate of more than 80 micro g/m[3]. There was a strong correlation between indoor temperature and high MDI concentration, thus, it implies that various temperatures may be increased, in addition to working time ensuring it has a good correlation with MDI concentration. It also implies that when ever they have more working time comparatively, in turn, they have high exposure rate of MDI pollutant in the workplace. To obtain a better way for determination of MDI concentration in the workplace is using biological monitoring as a standard method to survey the exposure to diisocyanate, by using metabolite determination, it will be easier to collect and analyze more samples as the sampling is not as time-consuming as air monitoring

Calcification Comparison of Polymers for Vascular Graft

Polytetrafluoroethylene (PTFE), polyurethane (PU) and silicone are widely known biocompatible polymers which are commonly used for vascular grafts. However, in vitro and in vivo calcifications of these polymers have been found to seriously compromise their quality as biomaterials. In consideration of this problem, the present study compared the calcification rate and extent of PTFE, PU and silicone. Using the in vitro flow-type method, PTFE, PU and silicone films were tested for 1, 4, 7, 10, 14 and 21 days. After 21 days of in vitro calcification test, the calcium levels on PTFE, PU and silicone were 35.89 5.01 microgram /cm2, 23.73 0.68 microgram/cm2 and 19.86 5.28 microgram/cm2, respectively. The higher observed calcium level for PTFE may be due to the effect of the rough surface of PTFE in accumulating calcium ions on the polymer surface. From the 7th day of test, the [Ca]/[P] molar ratio started to decrease over time, and PTFE showed a faster calcification process. This decreasing [Ca]/[P] molar ratio demonstrated the typical calcification mechanism consisting of phosphorus ion accumulation following calcium ion accumulation. This study concluded that PU and silicone are less calcified than PTFE film, a finding in good agreement with previously published studies.

Biocompatibilidade de materiais endodônticos. Resposta do tecido subcutâneo de cobaias à resina poliuretana derivada do óleo de mamona - Parte 2 / Biocompatibility of endodontic materials subcutaneous tissue response of guinea-pig to polyurethane resin derived from castor bean oil - Part 2

A poliuretana derivada do óleo de mamona apresenta uma fórmula molecular que tem mostrado compatibilidade com os tecidos vivos. O propósito deste trabalho foi o de comparar esse polímero (Poliol) com quatro materais - AH26, Dentinol, Kerr Sealer, e Sealapex - segundo as normas da FDI e ADA/ANSI, com a finalidade da sua utilizaçäo como cimento de obturaçäo de canal. Todos os materiais foram manipulados de acordo com as instruçöes dos fabricantes. O método utilizado foi o de implante subcutâneo de tubos de Teflon em cobaias. (FDI, 1980; ADA/ANSI, 1982) Foram utilizadas 45 cobaias (+800gr cada), que receberam quatro implantes dorsais com o mesmo material (12 por período). A parede externa do tubo serviu como controle da técnica. Após 30, 60, e 90 dias, os animais foram mortos e os espécimes processados para exame histológico de rotina...

Work place challenge: spirometric response in polyurethane (isocyanate) paint workers.

In industrialised countries, isocyanate is probably the most common cause of occupational asthma. The present study was conducted to see the effect on FEV1 in workers who were directly exposed to isocyanate. One hundred and fourteen workers of a rail coach factory who were involved in polyurethane paint spray were studied. Spirometry was done three times, first before starting the work, at two hours and then 6-8 hours after finishing the work to see immediate, late and dual responses. Positive response was considered when there was fall of 20% or more in forced expiratory volume in 1 second (FEV1) from base line. Sixteen per cent of the workers exposed to isocyanate developed immediate reaction, 10% developed late reaction and 6% developed dual reaction. Non-smokers were more prone to develop late and dual responses.