scholarly journals A Simple and Accurate Approach for Determining the VFA Concentration in Anaerobic Digestion Liquors, Relying on Two Titration Points and an External Inorganic Carbon Analysis

2021 ◽  
Vol 5 (2) ◽  
pp. 15
Author(s):  
Paz Nativ ◽  
Yonatan Gräber ◽  
Yaron Aviezer ◽  
Ori Lahav
Keyword(s):  
Partial Pressure ◽  
Volatile Fatty Acids ◽  
Inorganic Carbon ◽  
Strong Acid ◽  
Direct Analysis ◽  
Anaerobic Digesters ◽  
Acid Titration ◽  
Partial Pressure Of Co2 ◽  
Ph Range

A new analytic approach is presented for determining the total volatile fatty acids (VFAT) concentration in anaerobic digesters. The approach relies on external determination of the inorganic carbon concentration (CT) in the analyzed solution, along with two strong-acid titration points. The CT concentration can be determined by either a direct analysis (e.g., by using a TOC device) or by estimating it from the recorded partial pressure of CO2(g) in the biogas (often a routine analysis in anaerobic digesters). The titration is carried out to pH 5.25 and then to pH 4.25. The two titration results are plugged into an alkalinity-mass-based equation and then the two terms are subtracted from each other to yield an equation in which VFAT is the sole unknown (since CT is known and the effect of the total orthophosphate and ammonia concentrations is shown to be small at this pH range). The development of the algorithm and its verification on four anaerobic reactor liquors is presented, on both the raw water and on acetic acid-spiked samples. The results show the method to be both accurate (up to 2.5% of the expected value for VFAT/Alkalinity >0.2) and repetitive when the total orthophosphate and ammonia concentrations are known, and fairly accurate (±5% for VFAT >5 mM) when these are completely neglected. PHREEQC-assisted computation of CT from the knowledge of the partial pressure of CO2(g) in the biogas (and pH, EC and temperature in the liquor) resulted in a very good estimation of the CT value (±3%), indicating that this technique is adequate for the purpose of determining VFAT for alarming operators in case of process deterioration and imminent failure.

scholarly journals CO2 directly modulates connexin 26 by formation of carbamate bridges between subunits

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Louise Meigh ◽  
Sophie A Greenhalgh ◽  
Thomas L Rodgers ◽  
Martin J Cann ◽  
David I Roper ◽  
...  
Keyword(s):  
Amino Acids ◽  
Partial Pressure ◽  
Computational Modelling ◽  
Connexin 26 ◽  
Homeostatic Regulation ◽  
Co2 Sensitivity ◽  
Partial Pressure Of Co2 ◽  
Physiological Sensing

Homeostatic regulation of the partial pressure of CO2 (PCO2) is vital for life. Sensing of pH has been proposed as a sufficient proxy for determination of PCO2 and direct CO2-sensing largely discounted. Here we show that connexin 26 (Cx26) hemichannels, causally linked to respiratory chemosensitivity, are directly modulated by CO2. A ‘carbamylation motif’, present in CO2-sensitive connexins (Cx26, Cx30, Cx32) but absent from a CO2-insensitive connexin (Cx31), comprises Lys125 and four further amino acids that orient Lys125 towards Arg104 of the adjacent subunit of the connexin hexamer. Introducing the carbamylation motif into Cx31 created a mutant hemichannel (mCx31) that was opened by increases in PCO2. Mutation of the carbamylation motif in Cx26 and mCx31 destroyed CO2 sensitivity. Course-grained computational modelling of Cx26 demonstrated that the proposed carbamate bridge between Lys125 and Arg104 biases the hemichannel to the open state. Carbamylation of Cx26 introduces a new transduction principle for physiological sensing of CO2.

scholarly journals A New Mathematical Model for the Accurate Determination of Volatile Fatty Acids Concentration in Anaerobic Digesters

2020 ◽  
Vol 06 (02) ◽  
pp. 67-84
Author(s):  
Gaston Nsavyimana ◽  
Salvator Kaboneka ◽  
Casimir Harerimana ◽  
Chema Keffala ◽  
Marc Elskens ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Fatty Acids ◽  
Volatile Fatty Acids ◽  
Accurate Determination ◽  
Anaerobic Digesters

Comparison of cardiac output during exercise by single-breath and CO2-rebreathing methods

1985 ◽  
Vol 58 (4) ◽  
pp. 1372-1377 ◽  
Author(s):  
M. D. Inman ◽  
R. L. Hughson ◽  
N. L. Jones
Keyword(s):  
Cardiac Output ◽  
Partial Pressure ◽  
Co2 Rebreathing ◽  
Single Breath ◽  
Partial Pressure Of Co2 ◽  
The Difference ◽  
End Tidal ◽  
Rebreathing Method ◽  
Single Breath Method

Cardiac output (Q) was estimated in supine rest and in upright cycling at several work rates up to 200 W in five male and one female subjects. At least four repetitions of both the CO2-rebreathing plateau method (Collier, J. Appl. Physiol. 9:25–29, 1956) and the Kim et al. (J. Appl. Physiol. 21: 1338–1344, 1966) single-breath method were performed at each work rate, in a steady state of O2 consumption and heart rate. At supine rest and low work rates, estimates of Q were similar by the two methods. However, at higher work rates, the single-breath method significantly (P less than 0.05) underestimated the value obtained by CO2 rebreathing. The reason for the difference in estimates of Q by the two methods was traced to the determination of arterial partial pressure of CO2 (PaCO2) and mixed venous partial pressure of CO2 (PvCO2). The estimate of PaCO2 from the single-breath method was approximately 88.5% of the estimate from end-tidal PCO2 used with the rebreathing method (P less than 0.001). The oxygenated PvCO2 calculated from the single-breath Q averaged approximately 92.5% of the PvCO2 from CO2 rebreathing (P less than 0.0001). The difference in estimates of Q was not eliminated by using a logarithmic form of the CO2 dissociation curve with the single-breath method.

Accuracy in determination of the temperature and partial pressure of CO2 in CO2:N2:H2O:NO2 mixtures by multiple-frequency laser probing

2007 ◽  
Vol 74 (6) ◽  
pp. 903-909 ◽  
Author(s):  
K. I. Arshinov ◽  
M. K. Arshinov ◽  
V. V. Nevdakh ◽  
M.-Y. Perrin ◽  
A. Soufiani ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Multiple Frequency ◽  
Laser Probing ◽  
Partial Pressure Of Co2 ◽  
Frequency Laser

scholarly journals KAJIAN EKSTRAK ETANOL BUNGA BOGENVIL (Bougenvillea spectabillis Willd) SEBAGAI BIOINDIKATOR ASAM BASA

KOVALEN ◽  
2017 ◽  
Vol 3 (3) ◽  
pp. 277
Author(s):  
Nurhaeni Nurhaeni ◽  
Fitri A Bande ◽  
Rismawaty Sikanna
Keyword(s):  
Color Change ◽  
Ethanol Extract ◽  
Strong Acid ◽  
Weak Acid ◽  
Alkaline Condition ◽  
Acid Base ◽  
Ph Indicator ◽  
Strong Base ◽  
Acid Titration

Studies of ethanol extract of bougainvillea flowers (Bougenvillea spectabillis Willd) as bioindicators of the acid-base has been done. The aims to determine the content of chemical compounds contained in extracts of bougainvillea flowers and bougainvillea flower extract pH stretch. Achievement of the objectives has done through the test of ethanol extract of bougainvillea identification of compounds and the determination of the acid-base stretch of pH indicator is. The obtained results showed that bogenvil ethanol extract containing flavonoids with 401 nm absorption and provided a color change in the acid and alkaline condition the color is yellow. The appropriate acid-base titration is used as bioindicators of a strong acid titration with a strong base, weak acid with a strong base and a weak base with a strong acid.Keywords: Flowers bougainvillea, indicators, bases acid titration

Scaling risk assessment in a closed circuit recycled board mill by speciation methods

TAPPI Journal ◽  
2012 ◽  
Vol 11 (5) ◽  
pp. 53-61 ◽  
Author(s):  
PATRICK HUBER ◽  
SYLVIE NIVELON ◽  
PATRICE NORTIER
Keyword(s):  
Calcium Carbonate ◽  
Volatile Fatty Acids ◽  
Inorganic Carbon ◽  
Stability Index ◽  
Closed Circuit ◽  
Critical Problem ◽  
Local Scaling ◽  
Water Analyses ◽  
Closed Water ◽  
Speciation Calculation

Calcium carbonate scaling often is a critical problem for recycled board mills that have closed water circuits. The objective of this study was to determine local scaling risks throughout the production process. To predict scaling potential, we calculated several saturation indexes, based on speciation determined from detailed water analyses. Calculated scaling trends are in accordance with observed dissolution and precipitation of calcium carbonate in the process, when considering local aeration phenomena. The importance of volatile fatty acids (resulting from anaerobic bacterial activity) in calco-carbonic equilibriums is discussed, and taken into account in the speciation calculation. We also demonstrate the need to measure inorganic carbon instead of alkalinity in such conditions. This makes typical scaling indexes, such as the Ryznar Stability Index, irrelevant to predict scaling risk in closed circuit conditions; thus, it is necessary to use general speciation methods, as described in this paper.

Determination of ochratoxin A in wine by direct analysis in real time-tandem mass spectrometry

2017 ◽  
Vol 35 (2) ◽  
pp. 185 ◽  
Author(s):  
Xiaoming GONG ◽  
Ronghui MA ◽  
Hongtao WANG ◽  
Liqiang GUO ◽  
Kai LI ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Real Time ◽  
Ochratoxin A ◽  
Direct Analysis ◽  
Tandem Mass

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

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