The determination of the ethanol content in food products is of fundamental importance for HALAL certification. In this work, an analytical method for the determination of ethanol in water by headspace gas chromatography with flame ionization detector (HS-GC-FID) has been developed and validated for the use in characterization of ethanol reference materials. The validation study was carried out in the linear calibration range 100 - 1500 mg/kg using the NIST SRM 2900, nominal 95.6%. The studied performance characteristics of the method were the limit of detection, LOD, the limit of quantification LOQ, selectivity, linearity, precision, recovery and bias. The validation results showed that the method is selective, precise, accurate and free from any significant bias. The LOD and LOQ were 1.27 and 3.86 mg/kg respectively and the estimated expanded uncertainty was 2% indicating that the method is fit for the purpose of certification of ethanol in water reference materials.
Adel B. ShehataAbdulrahman R. Al AskarMohammed A. Al RasheedAbdulrahman M. Al ZahranyFahd A. Al KharraaSowailem A. Al Sowailem
Reverse-selective membranes have attracted considerable interest for bioethanol production.However,to date,the reverse-separation performance of ethanol/water is poor and the separation mechanism is unclear.Graphene-based membranes with tunable apertures and functional groups have shown substantial potential for use in molecular separation.Using molecular dynamics simulations,for the first time,we reveal twoway selectivity in ethanol/water separation through functional graphene membranes.Pristine graphene(PG)exhibits reverse-selective behavior with higher ethanol fluxes than water,resulting from the preferential adsorption for ethanol.Color flow mappings show that this ethanol-permselective process is initiated by the presence of ethanol-enriched and water-barren pores;this has not been reported in previous studies.In contrast,water molecules are preferred for hydroxylated graphene membranes because of the synergistic effects of molecular sieving and functional-group attraction.A simulation of the operando condition shows that the PG membrane with an aperture size of 3.8Åachieves good separation performance,with an ethanol/water separation factor of 34 and a flux value of 69.3 kg∙m‒2∙h‒1∙bar‒1.This study provides new insights into the reverse-selective mechanism of porous graphene membranes and a new avenue for efficient biofuel production.
Efficient separation of biofuels from fermentation broths vis pervaporation plays an important role in addressing the global challenges,such as developing renewable energy.Great efforts have been continuously devoted in the past decades to developing high-performance pervaporation membranes.A recent report published in Science by Zhao et al.showed that a superhydrophobic surface could contribute significantly to improving the pervaporation separation of ethanol-water mixture,which will generate broad interest for the new design of separation membranes.
