Determination of Pyrrolnitrin and Derivatives by Gas-Liquid Chromatography

A gas-liquid chromatographic technique was applied to the separation of pyrrolnitrin and its derivatives. The simultaneous use of a flame detector and an electron capture detector made possible the distinction between the nitro derivatives of pyrrolnitrin and the other metabolites. The metabolites could be readily quantitated with the electron capture detector, offering a much more sensitive assay than the flame detector.     

Analysis of methylthiohydantoins of amino acids by gas-liquid chromatography of their trimethylsilyl derivatives

A procedure is described for the analysis of methylthiohydantoins of amino acids from the Edman degradation of proteins and peptides by gas-liquid chromatography of their trimethylsilyl derivatives. The procedure is applicable to the methylthiohydantoins of all the amino acids commonly found in proteins with the exception of arginine, which did not yield a volatile derivative, and hydroxyproline and hydroxylysine, which were not investigated. Chromatographic separation is achieved in a single run with only one unresolved pair, which can be separated by a supplementary procedure requiring only 4.5 min.     

Effect of gibberellin on the production of ethylene and on respiration rate in yellow transparent apples

The dependence of ethylene production and respiration rate on the concentration of gibberellin (GA) applied in water emulsion of lanoline to young fruits was studied in Yellow transparent apples. Ethylene production and respiration rate were slightly increased by GA treatment. The increased level was maintained throughout the entire ripening period, which was also apparent from the total amount of both released gases. A gas-chromatographic method, using a flame ionization detector for simultaneous determination of ethylene and CO₂ in the atmosphere of experimental biological containers, is described in this paper. CO₂ is hydrogenated to methan on Ni — ThO₂ catalyst by hydrogen which is used as carrier gas. The gases pass the hydrogenating reactor after the separation in the Chromatographic column before entering the detector.     

Determination of urinary amino acids by means of glass capillary gas—liquid chromatography with alkali-flame ionisation detection and flame ionisation detection

The determination of amino acids as their N(O)-heptafluorobutyryl-isobutyl ester derivatives by glass capillary gas—liquid chromatography has been studied. Separations of amino acids obtained from insulin hydrolysate and human urine analysed with a flame ionisation detector, an alkali-flame ionisation detector and an electron-capture detector are shown. The quantitative results of urinary amino acids of one deep-sea diver are presented.     

Analysis of thiohydantoins from amino acids by gas-liquid chromatography on short glass capillary columns

A method for separation of amino acid methyl or phenyl thiohydantoins by GLC on a short glass capillary column is described. Calculations of required parameters of the capillary column are presented. By the described methods, nineteen of twenty silylated methylthiohydantoins were separated in one run. The last one (histidine) can be identified on the same column by starting the analysis at a higher temperature. Cysteine and arginine were analysed as S-methylcysteine and ornithine, respectively.     

Separation of mono- and diglycerides by gas--liquid chromatography

The parameters affecting the separation and quantification of trimethylsilyl ethers of mono- and diglycerides have been investigated by gas-liquid chromatography with QF-1 and SE-30 as stationary phases and a flame ionization detector. Results have been compared with those obtained earlier for triglycerides. The isothermal characteristics of a range of trimethylsilyl ethers of mono- and diglycerides on both stationary phases showed that log retention volume was directly proportional to carbon number and inversely proportional to absolute temperature. However, glyceride derivatives with lower carbon numbers deviated from these relationships. By using various rates of programmed temperature rise, we have determined the elution temperatures (Kelvin scale) of the mono- and diglyceride trimethylsilyl ethers relative to that of glycerol trilaurate. The "carbon equivalent of a trimethylsilyl group" is defined and shown to be useful in comparing the chromatographic properties of different glyceride classes. Weight and molar correction factors have been obtained and used to analyze diglycerides derived from egg and bovine brain lecithins.     

Thermal and water source effects upon the stability of enteroviruses in surface freshwaters

The long-term survival of three human enterovirus serotypes, Coxsackievirus B3, echovirus 7, and poliovirus 1 was examined in samples of surface freshwater collected from five sites of physically different character. These were an artificial lake created by damming a creek, a small groundwater outlet pond, both a large- and a medium-sized river, and a small suburban creek. Survival was studied at temperatures of -20, 1, and 22 degrees C. The average amount of viral inactivation was 6.5-7.0 log10 units over 8 weeks at 22 degrees C, 4-5 log10 units over 12 weeks at 1 degree C, and 0.4-0.8 log10 units over 12 weeks at -20 degrees C. The effect of incubation temperature upon viral inactivation rate was statistically significant (p less than 0.00001). As determined by pairing tests, survival was also significantly related to both viral serotype and water source at each of the three incubation temperatures (p less than or equal to 0.05). Efforts were made to determine whether the rate of viral inactivation observed at the different incubation temperatures was related to characteristics inherent to the water that was collected from the different locations. The characteristics examined included physical and chemical parameters, indigenous bacterial counts, and the amount of bacterial growth that the waters would support (measured as the maximum number of generations which seeded bacteria could undergo after being placed into either pasteurized or sterile-filtered water samples). Analysis of viral inactivation rate versus these characteristics revealed three apparent effectors of viral persistence.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of pasteurization on the self-assembly of human milk lipids during digestion

Human milk is critical for the survival and development of infants. This source of nutrition contains components that protect against infections while stimulating immune maturation. In cases where the mother's own milk is unavailable, pasteurized donor milk is the preferred option. Although pasteurization has been shown to have minimal impact on the lipid and FA composition before digestion, no correlation has been made between the impact of pasteurization on the FFA composition and the self-assembly of lipids during digestion, which could act as delivery mechanisms for poorly water-soluble components. Pooled nonpasteurized and pasteurized human milk from a single donor was used in this study. The evolving FFA composition during digestion was determined using GC coupled to a flame ionization detector. In vitro digestion coupled to small-angle X-ray scattering was utilized to investigate the influence of different calcium levels, fat content, and the presence of bile salts on the extent of digestion and structural behavior of human milk lipids. Almost complete digestion was achieved when bile salts were added to the systems containing high calcium to milk fat ratio, with similar structural behavior of lipids during digestion of both types of human milk being apparent. In contrast, differences in the colloidal structures were formed during digestion in the absence of bile salt because of a greater amount of FFAs being released from the nonpasteurized than pasteurized milks. This difference in FFAs released from both types of human milk could result in varying nutritional implications for infants.     

Direct Quantitative Gas Chromatographic Separation of C2-C6 Fatty Acids, Methanol, and Ethyl Alcohol in Aqueous Microbial Fermentation Media

A method is described for the direct quantitative gas chromatographic separation of C(2)-C(6) lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 muliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C(2)-C(6) acids added to culture supernatant fluids were obtained.     

Rapid and Sensitive Detection of Bacteria by Gas Chromatography

A gas chromatograph fitted with electron capture and flame ionization detectors was employed for the rapid detection of bacteria by analysis for their metabolic products. The presence of Proteus vulgaris, Streptococcus faecalis, S. liquefaciens, Escherichia coli B, Bacillus cereus, and B. popilliae was detected in 2 to 4 hr in media inoculated with less than 10(4) cells per ml, whereas a 7- to 12-hr growth period was required for the detection of products formed in cultures of Serratia marcescens, Aerobacter aerogenes, E. coli K-12, Staphylococcus aureus, and Salmonella typhimurium. Metabolites elaborated by the equivalent of less than a single cell of B. cereus, S. faecalis, P. vulgaris, or E. coli B were sensed by the electron capture detector. The flame ionization detector was generally not as sensitive. Volatile metabolites were identified, and their concentrations were determined.     

Quantitative gas-liquid chromatographic determination of ftorafur and 5-fluorouracil in biological specimens

A method developed for measuring the antitumor agent ftorafur and its biotransformation product 5-fluorouracil was applied to biological specimens. After extraction with ethylacetate, ftorafur, 5-fluorouracil, and the internal standard 2-methyl-4-hydroxy-6-chloromethylpyrimidine are converted to their chloromethyldimethylsilyl derivatives and assayed by glc, using either an electron-capture or a flame ionization detector. The minimum detectable amount is 100 pg/injection for ftorafur and 50 pg/injection for 5-fluorouracil employing electron-capture detection. Linearity was found up to microgram amounts of both substances, without any interference from endogenous substrates. Preliminary data are reported on the comparative serum kinetics of ftorafur and 5-fluorouracil in mice.     

Phosphorus release by pure cultures of Acinetobacter sp. : effect of the growth stage with cells cultivated on various carbon sources

In order to understand biological phosphorus removal mechanisms, the role of growth stage and volatile fatty acids (VFA) on phosphate release in the anaerobic stage of P removal by three Acinetobacter strains was investigated. The phosphate release in anaerobic conditions was affected by the physiological state of cells and by the carbon source used. When the experiments were made with stationary growth phase cells, the release of phosphate was higher for all three strains cultured on acetic, propionic and butyric acid. Cells showed a limit to the amount of phosphate that could be released from total phosphate accumulated. Only 5–38% of P accumulated by the log cells and 18–58% of total P accumulated by stationary cells could be released. The ratio between the amount of P released and organic substrate removed under anaerobic condition varies depending on VFA types and tested strains.     

Correlations between PID and FID Field Analytical Instruments in the Analysis of Soil Contaminated with Diesel Fuel

Research was conducted to determine if there is a correlation between the data gathered by field analytical instruments in analyzing soil contaminated with diesel fuel. One instrument was equipped with a flame ionization detector (FID) and the other a photoionization detector (PID). The results showed that the concentration readings of the PID and FID displayed a linear relationship for soil recently contaminated with diesel fuel. However, for soil containing weathered diesel fuel in the field, a logarithmic relationship between the PID and FID readings was displayed. It was also determined by laboratory experimentation that the PID and FID readings both exhibited log-linear decreases over time for uncovered diesel fuel-contaminated soil. It was concluded that the PID and FID can both individually be used to evaluate soil contaminated by diesel fuel and might be interchangeable depending on the needs of the researcher.     

External detection of axoplasmic transport using 32P-ATP as precursor

Axoplasmic transport was studied by employing a new external detection method, comparing it to the scintillation method. ³²P-ATP was used as the precursor, and the pattern obtained was one typical of slow transport. The patterns recorded from nerves with the external detector system were seen to be closely similar to those found in the same nerves with the usual scintillation method, the external detector systems having the advantage of allowing studies to be made of changes in the pattern of transport in the same nerve over a period of days.     

Rapid Sensitive Assay for Interferons Based on the Inhibition of MM Virus Nucleic Acid Synthesis

A method for assaying mouse interferon based on the inhibition of viral ribonucleic acid (RNA) synthesis was devised. The amount of MM virus and RNA synthesized in interferon-treated L-cell cultures was determined by measuring the amount of (3)H-uridine converted into a trichloroacetic acid-insoluble form after treatment of the infected cultures with 2.5 mug of actinomycin D per ml. The amount of RNA synthesized was inversely related to the concentration of interferon used for treatment. A linear dose-response regression curve was obtained by plotting the log of the amount of RNA made, expressed as a percentage of the control, versus the log of the reciprocal of the interferon dilution. A unit of interferon was defined as that concentration which inhibited nucleic acid synthesis by 50% (INAS(50)). The concentration of mouse interferon could be determined within 24 hr. This assay method, on the average, was approximately half as sensitive as the method which measured the 50% reduction of MM virus plaque number (PDD(50)-MM method), but was, on the average, almost 1.7 times as sensitive as the PDD(50)-VSV method. It averaged approximately 20 times the sensitivity of the methods which used as end points the 70% reduction in yield of MM virus or the complete inhibition of cytopathic effect by MM virus. The reproducibility of the INAS(50) technique was tested in two ways. (i) Four independent assays of an interferon specimen were performed with replicate cultures. The standard deviation was 11.2% of the mean titer. (ii) On different dates, one interferon specimen was assayed seven times and another was assayed four times. The standard deviations were 21.5 and 26.6% of the respective mean titers.     

Automatic method for evaluating the activity of sourdough strains based on gas pressure measurements

A new method is proposed for the evaluation of the activity of sourdough strains, based on gas pressure measurements in closed air-tight reactors. Gas pressure and pH were monitored on-line during the cultivation of commercial yeasts and heterofermentative lactic acid bacteria on a semi-synthetic medium with glucose as the major carbon source. Relative gas pressure evolution was compared both to glucose consumption and to acidification and growth. It became obvious that gas pressure evolution is related to glucose consumption kinetics. For each strain, a correlation was made between maximum gas pressure variation and amount of glucose consumed. The mass balance of CO2 in both liquid and gas phase demonstrated that around 90% of CO2 was recovered. Concerning biomass production, a linear relationship was found between log colony-forming units/ml and log pressure for both yeasts and bacteria during the exponential phase; and for yeasts, relative gas pressure evolution also followed optical density variation.     

静电喷雾法制备乳酸菌微胶囊的实验研究

目的为解决乳酸菌产品活菌数的不稳定性,对乳酸菌进行微胶囊化包埋。方法用海藻酸钠和明胶的混合体系作为壁材,对乳酸菌进行静电喷雾包埋处理,并让微胶囊化乳酸菌在模拟胃肠液的环境中进行耐酸性和肠溶性实验。结果混合体系的壁材与乳酸菌具有较好的生物相容性,优选得出当芯壁材为12时包埋率最高（96．3％）,微胶囊化乳酸菌在经人工胃液处理2h后,活菌数比未经微胶囊化的对照组高出2个数量级,且在经人工肠液处理40min后,乳酸菌几乎全部释放。结论静电喷雾法制备的乳酸菌微胶囊具有一定耐酸性和肠溶性。     

Gas chromatographic determination of the hypoglycaemic agent gliclazide in plasma

A gas chromatographic method has been developed that permits the accurate and specific determination of the hypoglycaemic agent gliclazide in plasma. Gliclazide is extracted with chloroform and, after clean-up, derivatized with diazomethane followed by heptafluorobutyric anhydride to form N-methyl-N′-heptafluorobutyrylgliclazide, which is assayed on a gas chromatograph equipped with a flame ionization detector, an electron-capture detector or a nitrogen—phosphorus sensitive detector.Accurate determinations are possible with flame ionization detection over a concentration range of 1–15 μg/ml of gliclazide in plasma with a relative standard deviation of 5.2%. The minimum detectable concentration with electron-capture detection is 0.02 μg per sample. Plasma levels of gliclazide in dogs following single oral administration (40 mg per dog) have also been determined.     

Chemical differences in volatiles between Melittis melissophyllum L. subsp. melissophyllum and subsp. albida (Guss) P. W. Ball (Lamiaceae) determined by solid-phase microextraction (SPME) coupled with GC/FID and GC/MS

Melittis melissophyllum (Lamiaceae) is a perennial herb, typical of woody places, occurring in Italy with two subspecies, i.e., melissophyllum and albida. So far, the classification of these two taxa was only based on morphology, i.e., the presence of glandular trichomes, the dimension of the leaves, and the number of teeth on each side as the main discriminant characters. To find marker compounds to chemically discriminate the subsp. melissophyllum with respect to the subsp. albida, a solid-phase microextraction SPME analysis coupled with GC/FID (=flame ionization detector) and GC/MS was carried out. SPME proved to be a chemotaxonomically useful technique that permitted a clearly differentiation of the two subspecies at headspace level. The subsp. melissophyllum was characterized by high amount of the mushroom alcohol oct-1-en-3-ol and the phenolic coumarin, whilst the subsp. albida exhibited a high content in monoterpenes and sesquiterpenes, α-pinene, sabinene, and (E)-caryophyllene being the major compounds. Multivariate chemometric techniques, such as cluster analysis (CA) and principal-component analysis (PCA), were used to support chemical data and characterize the population according to the taxonomy. In addition, the micromorphology and distribution of glandular trichomes of both subspecies were studied by scanning electron microscopy (SEM).     

Gas chromatographic determination of eugenol in ethanol extract of cloves

An ethanolic extract of cloves was analyzed by gas chromatography directly to identify eugenol and other major phenolic compounds without previous separation of other components. Separation was performed on a fused-silica capillary column of 30 mx0.53 mm I.D., 0.53 μm film thickness. The detector was a flame ionization detector. Helium gas at a flow-rate of 3 ml/min was used as a carrier gas. The analysis were performed with linear temperature programming. Nine components were detected and special attention was given to the major phenolic compound, eugenol.