title: Analysis of commercial beverage products by size exclusion chromatography coupled with UV-vis absorbance detection and dynamic surface tension detection.
abstract: Multidimensional analysis of instant coffee and barley beverage samples using size exclusion chromatography (SEC) combined with a dynamic surface tension detector (DSTD) and a UV-vis absorbance detector (UV) is reported. A unique finding of this study was the action of the tetrabutylammonium (TBA) cation as a modifying agent (with bromide as the counter anion) that substantially increased the surface pressure signal and sensitivity of many of the proteins in the chromatographically separated samples. The tetrabutylammonium bromide (TBAB) enhancement of the surface pressure signal was further investigated by studying the response of 12 commercial standard proteins (alpha-lactalbumin, beta-lactoglobulin, human serum albumin (HSA), albumin from chicken egg white (OVA), bovine serum albumin (BSA), hemoglobin, alpha-chymotrypsinogen A, cytochrome C, myoglobin, RNase A, carbonic anhydrase, and lysozyme) in buffer performed using flow injection analysis (FIA) coupled with the DSTD with and without various concentrations of TBAB. The FIA-DSTD data show that 1mM TBAB enhances sensitivity of HSA detection, by lowering the limit of detection (LOD) from 2mg/mL to 0.1mg/mL. Similarly, the LOD for BSA was reduced from 1mg/mL to 0.2mg/mL. These FIA-DSTD experiments allowed the detection conditions to be optimized for further SEC-UV/DSTD experiments. Thus, the SEC-UV/DSTD system has been optimized and successfully applied to the selective analysis of surface-active protein fractions in a commercial instant coffee sample and in a soluble barley sample. The complementary selectivity of using the DSTD relative to an absorbance detector is also demonstrated.
authors.affiliation: Department of Chemistry and Biochemistry, 3307 Third Avenue West, Suite 205, Seattle Pacific University, Seattle, WA 98119, USA. pierck1@spu.edu
authors.forename: Karisa M
authors.initials: KM
authors.lastname: Pierce
authors.forename: Emilia
authors.initials: E
authors.lastname: Bramanti
authors.forename: Massimo
authors.initials: M
authors.lastname: Onor
authors.forename: Roberto
authors.initials: R
authors.lastname: Spiniello
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kangas
authors.forename: Kristen J
authors.initials: KJ
authors.lastname: Skogerboe
authors.forename: Robert E
authors.initials: RE
authors.lastname: Synovec
mesh_terms: D000818:Animals; D001628:Beverages / Q000032:analysis*; D002417:Cattle; D002850:Chromatography, Gel; D002853:Chromatography, Liquid; D003069:Coffee / Q000737:chemistry; D017022:Flow Injection Analysis; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D011134:Polysaccharides / Q000032:analysis; D011506:Proteins / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013500:Surface Tension; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003069:Coffee; D011134:Polysaccharides; D011506:Proteins; D000644:Quaternary Ammonium Compounds; D014867:Water; C009405:tetrabutylammonium