High-performance liquid chromatographic method for the determination of cefpodoxime levels in plasma and sinus mucosa

A selective HPLC method is described for the determination of cefpodoxime levels in plasma and sinus mucosa. Sample preparation included solid-phase extraction with a C₈ cartridge. Cefpodoxime and cefaclor (internal standard) were eluted with methanol and analyzed on an optimised system consisting of a C₁₈ stationary phase and a ternary mobile phase (0.05 M acetate buffer pH 3.8—methanol—acetonitrile, 87:10:3, v/v) monitored at 235 nm. Linearity and both between- and within-day reproducibility were assessed for plasma and sinus mucosa samples. Inter-assay coefficients of variation were lower than 13.6% (n = 10) for plasma (0.2 μg/ml) and lower than 12.4% (n = 5) for sinus mucosa (0.25 μg/g). The quantification limit was 0.05 μg/ml for plasma and 0.13 μg/g for tissue. The method was used to study the diffusion of cefpodoxime in sinus mucosa.     

Application of ion-pair high-performance liquid chromatography to detection of the atypical coproporphyrin isomers II and IV in human faeces

A highly selective and sensitive method has been developed for the detection of small amounts of the atypical isomers II and IV of coproporphyrin in human faeces. This method combines liquid—liquid extraction and solid-phase sampling techniques using talc and C₁₈-modified silica gel as the sorbents. Simultaneous separation of the four coproporphyrin isomers I–IV was achieved by isocratic ion-pair high-performance liquid chromatography. Stool samples of healthy subjects (n = 12) contained 1.1 ± 0.4% (mean ± S.D.) isomer II and 2.2 ± 0.9% isomer IV of total coproporphyrins. A somewhat higher content of isomer II (2.7%) and isomer IV (5.4%) was found in faeces of a patient suffering from porphyria variegata.     

Biological monitoring of hexamethylene diisocyanate by determination of 1,6-hexamethylene diamine as the trifluoroethyl chloroformate derivative using capillary gas chromatography with thermoionic and selective-ion monitoring

A GC method using a novel derivatization reagent, 2′,2′,2-trifluoroethyl chloroformate (TFECF), for the derivatization of primary and secondary aliphatic amines with the formation of carbamate esters is presented. The method is based on a derivatization procedure in a two-phase system, where the carbamate ester is formed. The method is applied to the determination of 1,6-hexamethylene diamine (HDA) in aqueous solutions and human urine, using capillary GC. Detection was performed using thermionic specific detection (TSD) and mass spectrometry (MS)—selective-ion monitoring (SIM) using electron-impact (EI) and chemical ionization (CI) with ammonia monitoring both positive (CI)⁺ and negative ions (CI)⁻. Quantitative measurements were made in the chemical ionization mode monitoring both positive and negative ions. Tetra-deuterium-labelled HDA (TDHDA; H₂NC²H₂(CH₂)₄C²H₂NH₂) was used as the internal standard for the GC—MS analysis. In CI⁺ the m/z 386 and the m/z 390 ions corresponding to the [M + 18]⁺ ions (M = molecular ion) of HDA—TFECF and TDHDA—TFECF were measured; in CI⁻ the m/z 267 and the m/z 271 ions corresponding to the [M — 101]⁻ ions. The overall recovery was found to be 97 ± 5% for a HDA concentration of 1000 μg/l in urine. The minimal detectable concentration in urine was found to be less than 20 μg/l using GC—TSD and 0.5 μg/l using GC—SIM. The overall precision for the work-up procedure and GC analysis was ca. 3% (n = 5) for 1000 μg/l HDA-spiked urine, and ca. 4% (n = 5) for 100 μg/l. The precision using GC—SIM for urine samples spiked to a concentration of 5 μg/l was found to be 6.3% (n = 10).     

High-performance liquid chromatographic determination of spectinomycin in swine, calf and chicken plasma

A rapid clean-up procedure based on ion-pair solid-phase extraction (SPE) for the high-performance liquid chromatographic (HPLC) determination of spectinomycin in swine, calf and chicken plasma at a limit of detection of 50 ng/ml is described. After dilution with water and adjustment of the pH to approximately 5.6, the plasma is applied to a high-hydrophobic C₁₈ SPE column treated with sodium dioctylsulphosuccinate. Spectinomycin is eluted with methanol and derivatized with 2-naphthalene sulphonyl chloride prior to chromatography. The HPLC set-up consists of a dual-column system using two Chromspher silica columns and dichloromethane—acetonitrile—ethyl acetate—acetic acid, in different ratios, as mobile phases. Detection is performed at 250 nm. Quantification is carried out using external standards prepared in blank cleaned plasma. Mean recoveries were 83 ± 3% (n = 5), 93 ± 6% (n = 5) and 92 ± 6% (n = 6) for swine, calf and chicken plasma, respectively, at the 0.1 μg/ml level.     

Identification by gas chromatography and mass spectrometry of lipids from the rat Harderian gland

Lipids from rat Harderian glands were extracted with ethyl acetate, hydrolysed with base and examined by gas chromatography (GC) and gas chromatography—mass spectrometry (GC—MS) as trimethylsilyl (TMS), [²H₉]TMS, methyl ester—TMS, picolinyl, nicotinate and nicotinylidene derivatives. The latter three derivatives were used to reveal the structures of the alkyl chains of fatty acids, alcohols and glycerol ethers, respectively. Forty-eight compounds were identified, representing about 97% of the total extracted lipids as measured by GC peak areas. The major constituents were fatty acids with chain lengths from 12 to 22 carbon atoms (mainly C₁₈ and C₂₀) and fatty alcohols (C₁₆ to C₂₆) derived from wax esters. Most of these acids and alcohols were unsaturated in the ω-7 position and were accompanied by smaller amounts of the saturated and ω-5 monounsaturated analogues. Glycerol ethers were also identified for the first time in this secretion; the ether chains contained from 14 to 19 carbon atoms (mainly 16) and were straight-chain saturated, unsaturated (ω-5 and ω-7) and branched (iso). The only sterol found was cholesterol amounting to 1.24% of the total extract.     

Characterization of VOC Emission from Materials in Vehicular Environment at Varied Temperatures: Correlation Development and Validation

The steady state VOC concentration in automobile cabin is taken as a good indicator to characterize the material emission behaviors and evaluate the vehicular air quality. Most studies in this field focus on experimental investigation while theoretical analysis is lacking. In this paper we firstly develop a simplified physical model to describe the VOC emission from automobile materials, and then derive a theoretical correlation between the steady state cabin VOC concentration (C _a) and temperature (T), which indicates that the logarithm of C _a/T ^0.75 is in a linear relationship with 1/T. Experiments of chemical emissions in three car cabins at different temperatures (24°C, 29°C, 35°C) were conducted. Eight VOCs specified in the Chinese National Standard GB/T 27630–2011 were taken for analysis. The good agreement between the correlation and experimental results from our tests, as well as the data taken from literature demonstrates the effectiveness of the derived correlation. Further study indicates that the slope and intercept of the correlation follows linear association. With the derived correlation, the steady state cabin VOC concentration different from the test conditions can be conveniently obtained. This study should be helpful for analyzing temperature-dependent emission phenomena in automobiles and predicting associated health risks.     

Lipid Formation by Aqueous Fischer-Tropsch-Type Synthesis over a Temperature Range of 100 to 400 °C

The formation of lipid compounds during anaqueous Fischer-Tropsch-type reaction was studied withsolutions of oxalic acid as the carbon and hydrogensource. The reactions were conducted in stainlesssteel vessels by heating the oxalic acid solution atdiscrete temperatures from 100 to 400 °C, atintervals of 50 °C for two days each. Themaximum lipid yield, especially for oxygenatedcompounds, is in the window of 150–250 °C. At atemperature of 100 °C only a trace amount oflipids was detected. At temperatures above150 °C the lipid components ranged from C₁₂to >C₃₃ and included n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanals, n-alkanones, n-alkanes, andn-alkenes, all with essentially no carbon numberpreference. The n-alkanes increased inconcentration over the oxygenated compounds attemperatures of 200 °C and above, with a slightreduction in their carbon number ranges due tocracking. It was also noted that the n-alkanoicacids increased while n-alkanols decreased withincreasing temperature above 200 °C. Attemperatures above 300 °C synthesis competeswith cracking and reforming reactions. At 400 °Csignificant cracking was observed and polynucleararomatic hydrocarbons and their alkylated homologswere detected. The results of this work suggest thatthe formation of lipid compounds by aqueous FTTreactions proceeds by insertion of a CO group at theterminal end of a carboxylic acid functionality toform n-oxoalkanoic acids, followed by reductionto n-alkanoic acids, to n-alkanals, thento n-alkanols. The n-alkenes areintermediate homologs for n-alkan-2-ones andn-alkanes. This proposed mechanism for aqueousFTT synthesis differs from the surface-catalyzedstepwise FT process (i.e., gaseous) of polymerization of methylene reported in the literature.     

Genotoxic and mutagenic activity of environmental air samples from different rural, urban and industrial sites in Flanders, Belgium

The present study reports mutagenic and genotoxic activities associated with ambient air collected at 15 sites characteristic for urban, industrial or rural conditions in Flanders. Airborne particulates (PM10) and semi-volatile compounds were collected on quartz filters (QF) and polyurethane foam (PUF) cartridges using a high-volume sampling device. The mutagenic and genotoxic potency of the organic extracts – Soxhlet extraction with acetone – was determined by use of the Salmonella mutagenicity standard plate-incorporation assay and the Vitotox^® assay, respectively. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC).Ambient air samples contained significant PAH levels and mutagenic activities at all 15 sites: direct mutagenicity of up to 47 revertants per cubic meter was found in the QF extracts and more limited activity of up to 11 rev m⁻³ in the PUF extracts. Metabolic activation of PUF extracts resulted in an important increase in mutagenic activity, up to 30 rev m⁻³, but no such increase was observed for QF extracts. The highest values were observed outside large cities at industrial sites and at a rural site contaminated by pollution from a chemical plant at a distance of 4 km. Also at the background location near the North Sea a significant mutagenic activity was measured in the QF extracts (+S9: 9 rev m⁻³; −S9: 7 rev m⁻³). Apparently, there is in Flanders a significant background exposure level to airborne mutagenicity, even in areas with limited or no nearby pollution sources. Based on the concentrations of 10 mutagenic PAHs and supposing additivity of their specific mutagenicities, only a few percent (mean 3%) of the observed indirect mutagenic activity could be explained. This implies that most mutagenic activity originated from other substances that were not identified or measured in our chemical analysis. This underscores the importance of bio-monitoring measurements.     

Antibiotic production by the immobilized cyanobacterium,Scytonema sp. TISTR 8208, in a seaweed-type photobioreactor

A photobioreactor was constructed using either anchored polyurethane foam strips (1 × 1 × 40 cm, PU-strips) fixed on a stainless-steel ring to prevent flotation, or free-floating polyurethane foam blocks (1 × 1 × 1 cm, PU-blocks) as biomass supporting materials (BSM). The cyanobacterium,Scytonema sp. TISTR 8208, which produces an antibiotic, was immobilized onto PU-strips or -blocks. The free-floating PU-blocks could immobilize only about 70% of the total cells, while the anchored PU-strips could immobilize as much as 97%. PU-strips were chosen as the BSM and we named this type of reactor, seaweed-type bioreactor (STB). Optimal physical conditions for antibiotic production were determined in the STB. Inoculum density was 0.4 g l^–1 and cells were sparged with air containing 5% CO₂ circulated at the gas flow rate of 250 ml min^–1 and illuminated at a light intensity of 200 mol photon m^–2 s^–1. The production of antibiotic could be increased 3-fold.Author for correspondence     

Volatile secretions and epicuticular hydrocarbons of the beetle Ulomoides dermestoides

Many species of tenebrionids produce and secrete a defensive volatile blend containing mainly benzoquinones and alkenes. In this study we characterized the volatile organic compounds (VOC) of the beetle Ulomoides dermestoides (Coleoptera: Tenebrionidae). Solid phase microextraction (SPME) coupled to capillary gas chromatography–mass spectrometry (CGC–MS) analysis was used to identify methyl-1,4-benzoquinone (MBQ), ethyl-1,4-benzoquinone (EBQ), 1-tridecene (C_13:1), and 1-pentadecene (C_15:1), representing more than 90% of the volatile blend. We also used CGC–MS to analyze the epicuticular hydrocarbons of U. dermestoides. Saturated, unsaturated, and branched structures with chain lengths ranging from 13 to 43 carbons were detected. n-pentacosane (C_25:0) and 9,11-pentacosadiene (9,11-C_25:2) were the most abundant components, representing more than 40% of the cuticular hydrocarbons.     

Influence of Precision of Emission Characteristic Parameters on Model Prediction Error of VOCs/Formaldehyde from Dry Building Material

Mass transfer models are useful in predicting the emissions of volatile organic compounds (VOCs) and formaldehyde from building materials in indoor environments. They are also useful for human exposure evaluation and in sustainable building design. The measurement errors in the emission characteristic parameters in these mass transfer models, i.e., the initial emittable concentration (C ₀), the diffusion coefficient (D), and the partition coefficient (K), can result in errors in predicting indoor VOC and formaldehyde concentrations. These errors have not yet been quantitatively well analyzed in the literature. This paper addresses this by using modelling to assess these errors for some typical building conditions. The error in C ₀, as measured in environmental chambers and applied to a reference living room in Beijing, has the largest influence on the model prediction error in indoor VOC and formaldehyde concentration, while the error in K has the least effect. A correlation between the errors in D, K, and C ₀ and the error in the indoor VOC and formaldehyde concentration prediction is then derived for engineering applications. In addition, the influence of temperature on the model prediction of emissions is investigated. It shows the impact of temperature fluctuations on the prediction errors in indoor VOC and formaldehyde concentrations to be less than 7% at 23±0.5°C and less than 30% at 23±2°C.     

Assessment of oxidative DNA damage formation by organic complex mixtures from airborne particles PM10

The free radical generating activity of airborne particulate matter (PM₁₀) has been proposed as a primary mechanism in biological activity of ambient air pollution. In an effort to determine the impact of the complex mixtures of extractable organic matter (EOM) from airborne particles on oxidative damage to DNA, the level of 8-oxo-2′-deoxyguanosine (8-oxodG), the most prevalent and stable oxidative lesion, was measured in the human metabolically competent cell line Hep G2. Cultured cells were exposed to equivalent EOM concentrations (5–150 μg/ml) and oxidative DNA damage was analyzed using a modified single cell gel electrophoresis (SCGE), which involves the incubation of whole cell DNA with repair specific DNA endonuclease, which cleaves oxidized DNA at the sites of 8-oxodG. EOMs were extracted from PM₁₀ collected daily (24 h intervals) in three European cities: Prague (Czech Republic, two monitoring sites, Libuš and Smíchov), Košice (Slovak Republic) and Sofia (Bulgaria) during 3-month sampling periods in the winter and summer seasons. No substantial time- and dose-dependent increase of oxidative DNA lesions was detected in EOM-treated cells with the exception of the EOM collected at the monitoring site Košice, summer sampling. In this case, 2 h cell exposure to EOM resulted in a slight but significant increase of oxidative DNA damage at three from total of six concentrations. The mean 8-oxodG values at these concentrations ranged from 15.3 to 26.1 per 10⁶ nucleotides with a value 3.5 per 10⁶ nucleotides in untreated cells. B[a]P, the positive control, induced a variable but insignificant increase of oxidative DNA damage in Hep G2 cell (approximately 1.6-fold increase over control value).Based on these data we believe that EOM samples extracted from airborne particle PM₁₀ play probably only a marginal role in oxidative stress generation and oxidative lesion formation to DNA. However, adsorbed organic compounds can undergo various interactions (additive or synergistic) with other PM components or physical factors (UV-A radiation) and in this way they might enhance/multiply the adverse health effects of air pollution.     

Olfactory sensitivity to food odor components in the short-tailed fruit bat,Carollia perspicillata (phyllostomatidae,chiroptera)

Summary The absolute olfactory sensitivity in a frui-teating bat, Carollia perspicillata, was investigated. Eighteen monomolecular food odor components from 3 substance classes were tested using a sniff rate analysis method. Detection thresholds (Table 1) ranged from 3.6 · 10¹³ to 2.7 · 10¹⁰ molecules/cm³ air. Interindividual variation (N = 4) for a substance did not exceed one order of magnitude. Significant correlations between olfactory performance and carbon chain length of the odor molecule were found for two substance classes: Sensitivity to the aliphatic iso-alcohols increased linearly from C₂ to C₅, and a nonlinear correlation was found for the acetic esters, with the C₄- and C₇-forms being clearly better perceived than the other homologues. In acetic esters, the sensitivity for the n-forms of the molecule was significantly higher than for the iso-forms. No such correlation between stereo-isomers and olfactory perception was found for the n- and iso-forms of carbon acids and aliphatic alcohols. Fruit-typical odor components like ethyl butyrate (5.4 · 10¹⁰), n-pentyl acetate (2.8 · 10¹⁰), or linalool (1.8 · 10¹¹ molecules/cm³ air) were the most effective among all compounds tested, suggesting that the nutritional specialization of the bat may be associated with a specific spectrum of olfactory sensitivity.     

Homologous long-chain δ-lactones in leaf cuticular waxes of Cerinthe minor

A homologous series of eleven δ-lactones (1,5-alkanolides) was identified in cuticular waxes from leaves of Cerinthe minor L., six of them representing novel compounds. They accounted for 79% of the total coverage of 41 μg wax per cm² leaf area. Various chemical transformations with product identification by GC-mass spectrometry and GC-FTIR were employed to assign the structures. The chain-lengths of the δ-lactones ranged from C₂₂ to C₃₂ and even-numbered homologues were prevalent. Additionally, aldehydes (C₂₆–C₃₀), alkanes (C₂₃–C₂₉), primary alcohols (C₂₆–C₃₂), alkanoic acids (C₂₀–C₃₂), wax esters (C₄₀–C₅₆) and lupeol were detected.     

Polarisationsoptische Untersuchungen am Auge von Calliphora erythrocephala (Meig.)

Zusammenfassung Die Doppelbrechung der Cornealinse und der Rhabdomere im Facettenauge von Calliphora erythrocephala (MEIG.) wurde untersucht.Der Gangunterschied wurde in Schnitten parallel zur Ommatidienachse gemessen. Die Differenz der Brechungsindices — die Doppelbrechung — zwischen dem außerordentlichen und dem ordentlichen Strahl ist (n _e – n _o) = 0,0012. Die Cornealinse ist ein einachsig, negativ doppelbrechender Kristall. Die optische Achse verläuft parallel zur Ommenachse.Die Kristallkegel und die Rhabdomerenkappen sind isotrop. Die Rhabdomere selbst sind anisotrop. Der Gangunterschied in den Sehstäben 1–6 (50 nm) scheint größer zu sein als im siebenten Rhabdomer (18 nm). Die Rhabdomere der siebenten und achten Sehzelle liegen jedoch genau hintereinander in einer Achse und dieTubuli sind zueinander senkrecht orientiert. Polarisationsoptisch gesehen liegen die beiden Sehstäbe in Subtraktionsstellung. Die Doppelbrechung der Rhabdomere ist (n _e – n _o) = – 0,0004.

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Investigations with polarized light on the eye of Calliphora erythrocephala (Meig.)

Summary The birefringency of the corneal lens and of the rhabdomeres in the compound eye of Calliphora erythrocephala (MEIG.) was investigated.The phase difference was measured in sections parallel to the axis of the ommatidium. The difference of the refractive indices — the birefringency — between the extraordinary and the ordinary beam is (n _{e – n o}) = –0,0012. The corneal lens is a negative birefringent crystal. Its optical axis runs parallel to the axis of the ommatidium.The crystalline cones and the extracellular distal processes of the rhabdomeres are isotropic. The rhabdomeres are anisotropic. The phase difference along the rhabdomeres No. 1–6 (50 nm) seems to be higher than in the seventh (18 nm). As rhabdomere No. 8 is situated beneath rhabdomere No. 7 and the tubules of these two rhabdomeres are perpendicularly orientated, the phase differences are partially cancelled. The birefringency of the rhabdomeres is (n _e – n _o) = –0,0004.

     

A novel method for characterisation of microbial growth kinetics on volatile organic compounds

A novel method for the determination of microbial growth kinetics on hydrophobic volatile organic compounds (VOC) has been developed. A stirred tank reactor was operated as a fed-batch system to which the VOC was continuously fed via the gas phase, assuring a constant VOC concentration in the mineral medium. A flow of air was saturated with the VOC, and then mixed with a further flow of air, to obtain a predetermined VOC concentration. Thus, different VOC concentrations in the mineral medium could be obtained by altering the VOC concentration in the feed gas. The growth kinetics of Xanthobacter autotrophicus GJ10 on 1,2-dichloroethane (DCE) and of Pseudomonas sp. strain JS150 on MonoChloroBenzene (MCB) were assessed using this method. The growth of strain JS150 was strongly inhibited at MCB concentrations higher than 160 mg l⁻¹, and the results were fitted using a piecewise function. The growth kinetics of strain GJ10 were described by the Luong model where maximum growth rate μ_max = 0.12 h⁻¹, substrate saturation constant K _S = 7.8 mg l⁻¹, and maximum substrate concentration S _m (above which growth is completely inhibited) = 1080 mg l⁻¹. Varying nitrogen and oxygen flows enabled the effect of oxygen concentration on the growth kinetics of Pseudomonas JS150 to be determined. Received: 30 November 1998 / Received revision: 19 March 1999 / Accepted: 20 March 1999     

High-performance liquid chromatographic analysis of amoxicillin in human and chinchilla plasma, middle ear fluid and whole blood

We extended the application of a sensitive high-performance liquid chromatography assay of amoxicillin developed in this laboratory for human plasma and middle ear fluid (MEF) to other sample matrices including chinchilla plasma or MEF and human and chinchilla whole blood with minor modification and validated the limit of quantitation at 0.25 μg/ml with a 50-μl sample size for human and chinchilla plasmas or MEFs. Amoxicillin and cefadroxil, the internal standard, were extracted from 50 μl of the samples with Bond Elut C₁₈ cartridges. The extract was analyzed on a Keystone MOS Hypersil-1 (C₈) column with UV detection at 210 nm. The mobile phase was 6% acetonitrile in 5 mM phosphate buffer, pH 6.5 and 5 mM tetrabutylammonium. The within-day coefficients of variation were 2.7–9.9 (n=4) and 1.7–7.2% (n=3) for chinchilla plasma and MEF samples, respectively; 2.8–8.1% (n=3) and 2.9–4.7% (n=3) for human and chinchilla whole blood, respectively. An alternative mobile phase composition for chinchilla plasma and MEF samples reduced the analysis time significantly.     

Interactions of tropospheric CO2 and O3 enrichments and moisture variations on microbial biomass and respiration in soil

Soil microbial biomass C (C_mic) is a sensitive indicator of trends in organic matter dynamics in terrestrial ecosystems. This study was conducted to determine the effects of tropospheric CO₂ or O₃ enrichments and moisture variations on total soil organic C (C_org), mineralizable C fraction (C_Min), C_mic, maintenance respiratory (qCO₂) or C_mic death (qD) quotients, and their relationship with basal respiration (BR) rates and field respiration (FR) fluxes in wheat‐soybean agroecosystems. Wheat (Triticum aestivum L.) and soybean (Glycine max. L. Merr) plants were grown to maturity in 3‐m dia open‐top field chambers and exposed to charcoal‐filtered (CF) air at 350 μL CO₂ L^?1; CF air + 150 μL CO₂ L^?1; nonfiltered (NF) air + 35 nL O₃ L^?1; and NF air + 35 nL O₃ L^?1 + 150 μL CO₂ L^?1 at optimum (? 0.05 MPa) and restricted soil moisture (? 1.0 ± 0.05 MPa) regimes. The + 150 μL CO₂ L^?1 additions were 18 h d^?1 and the + 35 nL O₃ L^?1 treatments were 7 h d^?1 from April until late October. While C_org did not vary consistently, C_Min, C_mic and C_mic fractions increased in soils under tropospheric CO₂ enrichment (500 μL CO₂ L^?1) and decreased under high O₃ exposures (55 ± 6 nL O₃ L^?1 for wheat; 60 ± 5 nL O₃ L^?1 for soybean) compared to the CF treatments (25 ± 5 nL O₃ L^?1). The qCO₂ or qD quotients of C_mic were also significantly decreased in soils under high CO₂ but increased under high O₃ exposures compared to the CF control. The BR rates did not vary consistently but they were higher in well‐watered soils. The FR fluxes were lower under high O₃ exposures compared to soils under the CF control. An increase in C_mic or C_mic fractions and decrease in qCO₂ or qD observed under high CO₂ treatment suggest that these soils were acting as C sinks whereas, reductions in C_mic or C_mic fractions and increase in qCO₂ or qD in soils under elevated tropospheric O₃ exposures suggest the soils were serving as a source of CO₂.     

Protein recovery by continuous flotation

Summary Bovine serum albumin (BSA) was recovered from aqueous solutions by foam flotation. The protein concentrations in foam liquid C _S, in feed C _Pand in residue C _Rwere determined. The protein enrichment C _S/C_Pand the separation C _S/C_Ras well as the protein fraction in the foam liquid % BSA and foam liquid volume flow were determined as functions of the medium properties, operational conditions, and equipment parameters as well as concentrations of solid particles. At low protein concentrations in feed (e.g., C _P=40 mg · l^-1), and at 40° C, high performance was attained (C _X=2,000 mg · l^-1, C _R=4.4 mg · l^-1, C _S/C_P=50, C _S/C_R=450, 90% BSA. Continuous foam flotation is an efficient procedure for the recovery of low concentrations of proteins from liquid cultures.Abbreviations BSA bovine serum albumine - C _P protein concentration in feed (mg · l^-1) - C _R protein concentration in residue (mg · l^-1) - C _S protein concentration in foam liquid (mg · l^-1) - C _S/C_R protein separation (-) - C _S/C_P protein enrichment (-) - V _P feed rate (ml · min^-1) - V _R residue flow rate (ml · min^-1) - V _S foam liquid volume flow (ml · min^-1) - N number of theoretical stages in an ideal cascade (-) - temperature (° C) - mean residence time (min)