Determination of TBA number by high performance liquid chromatography

A high performance liquid chromatographic (HPLC) method for the quantitation of malonaldehyde in aqueous distillates was developed. Compared with the standard TBA test, the HPLC method was faster, and less affected by side feactions. A total of 5 min was necessary to assay each distillate and only malonaldehyde was detected. The standard curves were reproducible and standards were stable for up to 6 days. The HPLC method could detect malonaldehyde levels ranging from 1×10⁻¹¹ to 4×10⁻¹¹ mol/10μL and either peak height or peak area could be used to quantitate the malonaldehyde concentration. The coefficient of determination between absorbance values determined by the TBA test and peak heights determined by HPLC was 0.946. Twenty-one freeze-dried chicken samples with TBA numbers ranging from 3.93 to 16.6 were used for this correlation.     

Determination of ethylene oxide oligomer distributions in alcohol ethoxylates by HPLC using a rotating disc-flame ionization detector

A high performance liquid chromatographic (HPLC) method has been developed for the quantitative determination of ethylene oxide (EO) oligomer distributions (% wt) in acetylated alcohol ethoxylates, R(OCH₂CH₂)_nOH, from n=0, 1 to n=30 using a rotating disc-flame ionization detector. Both single carbon number and mixed carbon number alcohol-based (NEODOL® ethoxylates) samples have been analyzed by gradient elution with 2 different solvent systems on a Waters μ-Porasil column. With both solvent systems, 95% hexane is the initial solvent but with one system, 100% acetone is the final solvent and with the other, 10% methanol/90% acetone is used. The latter solvent elutes the higher ethoxylates from n=21 to n=30 quantitatively from the μ-Porasil column which the 100% acetone solvent fails to do. The 100% acetone solvent separates n=2 and n=3 from n=0,1 which the methanol-containing solvent does not do. Response factors for n=3 and n=8 have been experimentally determined and the response factors for the other EO units have been calculated from these 2 results. The corrected EO oligomer distributions for both NEODOL® 25-9 and NEODOL® 23-6.5 determined by HPLC are in good agreement with those determined earlier by circular thin layer chromatography (up to n=16 can be determined by this method). The average EO numbers determined by the HPLC method and by a wet chemical (phthalic anhydride) method are in excellent agreement for the above 2 samples and a sample of NEODOL® 23-7.5. The results are discussed in terms of Snyder’s theory for gradient elution in HPLC using the gradient steepness parameter.     

Kinetic analysis of plasma VLDL-TG and VLDL-remnant-TG turnover in anesthetized rats

We have estimated the turnover and relative pool sizes of nascent-VLDL-TG and VLDL-remnants-TG in anesthetized rats. [1-¹⁴C]Palmitoyl- and [2-³H]glyceryl-labeled “VLDL”-TG (including nascent VLDL-TG and VLDL-remnants-TG) were prepared by injecting labeled palmitate and glycerol into donor rats. Labeled serum from these rats was then injected intravenously into nembutalized male rats and serial blood samples taken for 30 min. Special care was taken to define any early components in the labeled “VLDL”-TG disappearance curves. In other experiments, the donors were rendered functionally hepatectomized 30 min after injection of³H-glycerol and the endogenous labeled VLDL-TG was allowed to circulate 30–60 min before collection of the TG-labeled VLDL-remnants-containing serum. The latter was injected into 4 recipient nembutalized rats and the remnant-TG-turnover measured by serial sampling as above. In two cases,¹⁴C-“VLDL” and³H-VLDL-remnants were injected as a single bolus into ether-anesthetized rats. Despite its complex composition, “VLDL”-TG in most cases disappeared in a single exponential fashion for 30 min with an average half-life of 5.9 min in nembutalized and 2.8 in ether-anesthetized rats. VLDL-remnants-TG showed a more complex behavior, but contained a major rapid component with a mean t_1/2 of ca. 1.5 min in both groups. The data, analyzed by multicompartmental analysis, were fitted to a simple model in which turnover of a larger nascent VLDL-TG pool with formation of a more rapidly turning over smaller pool of VLDL-remnant-TG is the rate-limiting step in overall TG removal from the d<1.006 fraction of rat serum. The data are consistent with our theoretical prediction that under these conditions the kinetics of the VLDL-remnants cannot be resolved from analysis of the total composite “VLDL” (nascent plus remnant) pool.     

Rapid analysis of dimer acid by HPLC/FID

A method was developed for the rapid analysis of polymerized fatty acids (dimer acid) using normal phase HPLC with a flame ionization detector (FID). The use of analytical scale HPLC with the FID is a significant limprovement over existing methodology for dimer analysis. The HPLC analysis takes only 25 min per sample, with no derivatization required. The FID response is linear for dimer samples from 10% to 90% monomer content. Absolute measurement precision is typically less than 0.5 area percent. Recovery of synthetic dimer blends averaged 102%. Results for the analysis of commercial dimer acid are comparable to those obtained using an HPLC/gravimetric method. The HPLC/FID method is applicable to the analysis of crude dimer as well as the finished dimer product.     

Gossypol analysis in cottonseed oil by HPLC

Gossypol in cottonseed oil was selectively separated by the extraction of cottonseed oil with a hexane and N,N dimethyl formamide:water (2∶1, v/v) solvent mixture. After filtration, the extract was injected into the HPLC with the elution time less than 15 min. The spectrophotometric method showed 2 to 5 times higher values of gossypol content in different types of glanded cottonseed oil than did the HPLC method. This is probably due to the gossypol derivatives and coloring interferences reacting with p-anisidine to develop color and increasing the absorbance reading, whereas gossypol was separated and detected in the HPLC method.     

Physicochemical characterization of galactosyldiglycerides and their quantitation in wheat flour lipids by high performance liquid chromatography

A high performance liquid chromatographic (HPLC) method was developed for analyzing digalactosyldiglycerides (DGDG) and monogalactosyldiglyceride (MGDG) in polar lipids fractionated from lipid extracts of wheat or flour. Wheat lipid samples were prepared by solvent extraction, then fractionated on a silica gel packed open column. A Spherisorb ODS (octadecyl silane) column with methanol/water elution system was used for separation of glycolipids in the polar lipid fractions. The detection limit of the refractive index detector with interferometric optics was 0.25μg for both DGDG and MGDG. Separating on nonpolar bonded phase columns permitted us to differentiate, based on fatty acid composition and position, among components within the specific glycolipid classes. Semipreparative HPLC on analytical columns was used to subfractionate the polar lipids. The glycolipids were collected for functional group characterization. Approximately 35% of each DGDG subfraction was accounted for as carbohydrate. The absence of phosphorus precluded phospholipids. Fatty acid analysis by gas chromatography showed the first DGDG to be linoleic acid, whereas the second DGDG peak was composed of linoleic, oleic and palmitic acids. Mass spectrometric analysis of the first DGDG peak showed linoleic acid in both the SN-1 and 2 positions. Mass spectrometric analysis revealed that palmitic or oleic acid in the second peak was preferentially located on the SN-1 position; linoleic acid was on the SN-2 position. Contribution no. 80-207J, Department of Grain Science and Industry, Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS. Part of a dissertation submitted by T.N. Tweeten in partial fulfillment of the PhD degree. Honored Student Award Presentation at AOCS annual meeting, San Francisco, April 1979.     

Analysis of milkfat by HPLC

A routine method for HPLC analysis of milkfat has been developed, which takes into account the specific phenomena of this complex and far-ranging system of triglycerides. The usual amount of injection of 1 mg has been reduced to 30 or 10 μg of fat. By this the composition of the mobile phase (acetone:acetonitrile, 35/65) and the temperature of the column (Nucleosil C18-5 μ, 15 cm + Microspher C18-3μ, 10 cm, in series, T=30–35 C) could be adjusted to a relatively high selectivity without inducing the high-melting fat components to crystallize on the column. A further advantage resulting from this consisted in permitting the eluent to be recycled over long periods of time. The extremely low amounts of samples necessitated a highly sensitive detection (Δn=5 × 10⁻⁷ RI units full scale deflection) which could be realized by an interferential refractometer in connection with a thermostat to keep up a stable temperature of the whole HPLC system (ΔT<0,005 K). By this it was possible to separate milkfat into 45 to 50 different types of triglycerides. By comparing soft and hard milkfats and fractions of milkfats, every fourth peak, starting with C 42, could be attributed to saturated triglycerides; apart from this, easily recognizable qualitative features appearing in the chromatograms permitted conclusions about the feeding regimen and energy supply of the cattle. Furthermore, due to the high stability of separating conditions achieved and due to computer software developed for this purpose it was possible to obtain and compare a large number of chromatograms under the same conditions.     

Identification and quantification of cholesterol oxides in grated cheese and bleached butteroil

Butteroil samples bleached with benzoyl peroxide (BP) and 17 commercial cheeses were screened for oxidized sterols by thin layer chromatography (TLC). Ungrated cheeses made from bleached milk and freshly bleached butteroil contained no detectable oxidized sterols. Oxidized sterols were detected in stored, bleached butteroils and in grated cheeses. Four major oxidation products were the isomeric 5,6-epoxycholesterols and the epimeric 7-hydroxycholesterols identified by TLC, high performance liquid chromatography (HPLC) and mass spectrometry (MS). Additional sterol oxides (tentatively identified and not quantified) present in these samples included low levels of 7-ketocholesterol and cholesta-3,5-dien-7-one. The epimeric 7-hydroxycholesterols were detected in bleached butteroils stored in air (BP-A) and nitrogen (BP-N) for 22 days at 15 C. Butteroil, after 90 days of storage at 15 C, had 30 (BP-N) and 60 (BP-A) μg total oxides/g of bleached oil and, after 1-year at −20 C, had 70 (BP-N) and 180 (BP-A) μg/g butteroil. A grated, unbleached cheese packaged in clear glass contained the most oxidized sterols (44 μg/g). Sterol oxides were not detected in bleached cream using a simulated industrial process.     

Enzymatic acylation of ether and ester lysophospholipids in rat liver microsomes

The acylation of lysophospholipids by rat liver acyltransferases was studied. A comparison between ester and ether lysophospholipids as substrates revealed large differences in substrate properties. For instance, oleic acid from oleoyl-CoA and arachidonic acid from arachidonoyl-CoA were not incorporated into 1-O-octadecyl-sn-glycero-3-phosphocholine under experimental conditions that allowed an optimal transfer of oleic acid and arachidonic acid to 1-O-palmitoyl-sn-glycero-3-phosphocholine. However, we observed an acyl-CoA-independent transfer of arachidonic acid from 1-O-stearoyl-2-O-arachidonoyl-sn-glycero-3-phosphoinositol to 1-O-octadecyl-sn-glycero-3-phosphocholine.     

Automated AOM test for fat stability

A home-built version of the automated AOM test was used with Canola, corn, sunflower, olive and Crisco? oils, shortening and lard. The endpoint was found by measuring the conductivity of a solution of the exit gas from the reaction tube. Coefficients of variability of the samples ranged from 1.1% to 8.3%. The endpoint of the test was ca. 100 PV for Canola oil, ca. 200 PV for corn oil and 35 PV for lard. The aqueous solutions of the volatiles of three oils were used to determine the TBA value. Canola, sunflower and olive oil had TBA values ranging from 6–60 μg malonaldehyde/g at the end point. No apparent relationship was found between the TBA values of the volatiles’ solutions and the PV’s of the oils. Presented at the 73rd AOCS Annual Meeting, Toronto, 1982.     

Determination of surfactant mixtures in shampoos and detergents by HPLC

A technique for separating 4 nonionic, 7 anionic and 4 amphoteric surfactants with n-dodecyl groups was studied by high performance liquid chromatography (HPLC) and applied to the determination of these surfactants in commercial shampoos and household detergents. Conditions used for the separation were: column packing and size, TSK-LS 410 (5μ) and 6 mm i.d. × 500 mm (2 connected, 250 mm columns); mobile phase, water/methanol (25/75, v/v) containing 0.25 M sodium perchlorate adjusted to pH 2.5 with phosphoric acid; column temp., 50 C; detector, RI. Surfactants in shampoos and detergents were clearly distinguished from each other and determined without column chromatographic pretreatment, e.g., ion-exchange chromatography.     

Carotenoids and tocols of corn grain determined by HPLC

A high performance liquid chromatographic (HPLC) procedure has been developed that permits determinationof carotenoids and tocols in the same sample preparation of corn grain. For 15 inbreds, the total carotenoids ranged from 16 to 77 μg/g dry wt and the total tocols from 30 to 128 μg/g dry wt. For four inbreds, total carotenoids were concentrated in the horny endosperm (83±2%) and total tocols in the germ (77±6%). After six months storage at room temperature, the mean loss of total carotenoids for four inbreds was 42±4%, while the tocols had a mean loss of 5%. Presented at the AOCS meeting in Honolulu, HI in May 1986.     

Electrospinning of chitosan/poly(lactic acid-co-glycolic acid)/hydroxyapatite composite nanofibrous mats for tissue engineering applications

Electrospinning, which is a fiber fabrication technique using electrical forces to produce fibers with diameters ranging from nanometers to several micrometers, can be used to prepare materials mimicking the extracellular matrix proteins for potential use as tissue engineering scaffolds. In this study, nanofibrous mats of chitosan (CH) and poly(lactic acid-co-glycolic acid) (PLGA) having fiber diameters between 167 to 525 nm, and containing hydroxyapatite (HAp), were prepared by electrospinning technique. Morphological, chemical, thermal and degradation tests and cell affinity tests were carried out. Chitosan mats were stable in aqueous media and showed degradability in the presence of lysozyme. In PBS solution, PLGA mats disintegrated completely in 2 weeks. Meanwhile, CH-PLGA mats containing equal amounts of both CH and PLGA fibers and CH-PLGA-HAp samples containing 20 % HAp lost 50 and 40 % of their initial weight in 4 weeks, respectively. Cell culture tests showed that all electrospun fibrous mats promoted SaOs-2 cell attachment and proliferation. However, cell proliferation on CH-PLGA-HAp fibrous mats was higher compared to the others after 7 days demonstrating the positive effect of HAp on cell affinity properties compared to pristine CH or PLGA fibrous scaffolds.     

Synthesis of EPDM-g-MAN by suspension graft copolymerization and its toughening effect on SAN resin

Suspension graft copolymerization of methyl methacrylate and acrylonitrile onto ethylene–propylene–diene terpolymer (EPDM) was carried out under different reaction conditions. A series of graft products of EPDM-graft-methyl methacrylate and acrylonitrile (EPDM-g-MAN), characterized by Fourier-transform infrared spectroscopy, was blended separately with styrene–acrylonitrile (SAN) resin to investigate their toughening effect on SAN matrix. The relationship between the polarity of EPDM-g-MAN and toughness of EPDM-g-MAN/SAN resin blends (AEMS) was evaluated. The compatibility and morphologies of AEMS were probed by dynamic mechanical analysis, transmission electron microscopy, and scanning electron microscopy to determine the toughing mechanism of the blends. Thermogravimetry results showed that the thermal stability of AEMS was enhanced with the incorporation of EPDM-g-MAN graft copolymer.     

Nutritional aspects in textured soy proteins

Textured soy protein products have found extensive use in pet foods and many human foods. They extend and complement meats in formulated foods. Numerous feeding tests with people and experimental animals show that biological values are high and protein efficiency ratios compare favorably with pure meat products. By careful processing of the textured soy products, high quality, safe, low cost protein food can be prepared. Textured soy proteins are an excellent example of man’s creative ability to engineer a supplementary food that is nutritious, palatable, and economical.     

Effect of nafion membrane thickness on performance of vanadium redox flow battery

The performance of vanadium redox ow batteries (VRFBs) using different membrane thicknesses was evaluated and compared. The associated experiments were conducted with Nafion® 117 and 212 membranes that have 175 and 50 μm of thickness, respectively. The charge efficiency (CE) and energy efficiency (EE) of VRFB using Nafion® 117 were higher than those of VRFB using Nafion® 212, while power efficiency was vice versa. In terms of amounts of charge and discharge that are measured in different charging current densities, the amounts in VRFB using Nafion® 212 are more than that in VRFB using Nafion® 117. To further characterize the effect of membrane thickness on VRFB performance, electrochemical impedance spectroscopy (EIS) and UV-vis. spectrophotometer (UV-vis) were used. In EIS measurements, VRFB using Nafion® 117 was more stable than that using Nafion® 212, while in UV-vis measurements, vanadium crossover rate of VRFB usingNafion® 212 (0.0125M/hr) was higher than that of VRFB using Nafion® 117 (0.0054 M/hr). These results are attributed to high crossover rate of vanadium ion in VRFB using Nafion® 212. With these results, vanadium crossover plays more dominant role than electrochemical reaction resistance in deciding performance of VRFB in condition of different membranes.     

Preparation and characterization of a new polymer/pharmaceutical-based composite. Part I: Meloxicam

Composites of low-density polyethylene (LDPE), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-octadecene), and an LDPE/EVA blend were prepared with different amounts of meloxicam (1, 3 and 5 wt %) by the melt blending process. Meloxicam was homogenously dispersed in polymer matrices. The polymer–meloxicam composites showed thermal behavior and thermal characteristics similar to those of the original polymers. Meloxicam release from the composites was examined in vitro for 50 days. The composites were incubated in phosphate-buffered solution and meloxicam concentration was determined by high-performance liquid chromatography. The prolonged release of the drug indicates that meloxicam-loaded plastic rings offer potential for control of reproduction and chronic inflammatory conditions.     

The analysis of glycerol by gas chromatography

Commencai glycerol and its organic impurities can be measured accurately by a single gas Chromatographic GC analysis utilizing Tenax-GC® and flame detection.     

Reversible addition-fragmentation chain transfer polymerization of vinyl acetate and vinyl pivalate in supercritical carbon dioxide

Two highly supercritical CO₂-soluble, poly(vinyl acetate) (PVAc)-based macro-reversible addition-fragmentation chain transfer (RAFT) agents were synthesized. The RAFT agents were used for the first time in RAFT/macromolecular design via the interchange of xanthates (MADIX) and polymerization of vinyl acetate (VAc) and vinyl pivalate (VPi) in supercritical carbon dioxide (scCO₂). A homopolymer PVAc and a block copolymer PVAc-b-PVPi made by RAFT/MADIX polymerization were characterized, and the effects of time and RAFT agents on polymerization were examined. For the 8.4 wt% RAFT agent in VAc, the molecular mass (M _n ) of homopolymer PVAc was 26,000 g mol^?1 and PDI was 1.35. For the copolymerization of VPi using 9.8 wt% PVAc-RAFT agent in VPi for 24 h, the M _n and PDI of PVAc-b-PVPi reached 32,400 g mol^?1 and 1.42, respectively. These results suggest that the polydispersity can be controlled during the clean production of PVAc and PVPi by RAFT/MADIX polymerization in scCO₂.     

Receptors of sex pheromones and abstinons inMusca domestica andGlossina morsitans

Receptors arranged in two pairs on the inner and outer sides of the proximal end of the tibia of legs ofMusca domestica L. andGlossina morsitans morsitans Westwood are described here for the first time. In the male fly, these receptors function in perception of sex pheromones, as demonstrated in experiments in which the sense organs were coated with paraffin. Similar techniques showed that sense organs for abstinon are located on the tarsi. Scanning electron microscopy and light microscopy show that the tibial sense organs ofMusca may be sensilla of the coeloconic type.