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Measurement Of Dissociation Constant (Ka) And Partition Coefficient (KP) Of Weak Organic Acids From Their First HyperpolarizabilitiesRay, Paresh Chandra 10 1900 (has links)
No description available.
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Control of Listeria monocytogenes on frankfurters formulated with and without lactate by dipping in sodium lactate and acidified calcium sulfate before and after inoculation for shelf life extensionStohs, Buffy Ann January 1900 (has links)
Master of Science / Food Science Institute, Animal Science & Industry / Daniel Y.C. Fung / The objectives of these studies were to determine the antimicrobial effects of sodium lactate (SL) and acidified calcium sulfate (ACS) on frankfurters formulated with and without lactate in the frankfurter formulation. Two studies were performed, one which mimicked home storage, and the other evaluated the effectiveness of SL (12% v/v) and ACS (12% v/v) as antimicrobial dips when used prior to and after inoculation of Listeria monocytogenes on frankfurters formulated without lactate. In the first study, five peeled frankfurters with and without lactate in the formulation were either dipped in SL or in ACS, stabilized for 30 minutes, vacuum packaged and stored for 30 days at 4°C. Controls were also prepared by dipping in 0.1% peptone. After 30 days the packages were opened and frankfurters were dip inoculated, stabilized for 30 minutes, and one frankfurter from each treatment was sampled. All other frankfurters were then placed in storage at 7°C and sampled after an additional 7, 14, and 21 days. For the second study, treatments consisted of five frankfurters that were first inoculated with a five-strain cocktail of L. monocytogenes, stabilized for 30 minutes, then dipped in SL or acidified ACS; or were first dipped in SL or ACS, stabilized for 30 minutes then dip inoculated. Controls were prepared by dip inoculating frankfurters. One frankfurter from each treatment was sampled immediately. The remaining frankfurters were vacuum packaged, stored at 4°C and sampled after 30, 60, 90, and 120 days. For both studies, on sampling days one frankfurter from each treatment was pulsified and plated on Tryptic Soy Agar (TSA) for viable cell counts and Modified Oxford Medium (MOX) for L. monocytogenes counts. The results indicated that SL dipped frankfurters had lower total aerobic counts and L. monocytogenes counts compared with ACS treatments and the controls. Use of lactate formulation in frankfurters resulted in lower bacterial counts of both natural microflora and inoculated L. monocytogenes in frankfurters after prolonged storage at 4 °C. This research indicates that sodium lactate (12% v/v) may be effective as an antimicrobial dip on frankfurters for the reduction of natural microflora and L. monocytogenes.
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Liquid-liquid equilibria related to the separation of organic acidsXhakaza, Nokukhanya Mavis January 2012 (has links)
Submitted in fulfilment of the requirements of the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / The thesis involves a study of the thermodynamics of ternary liquid mixtures involving carboxylic acids with sulfolane, hydrocarbons and acetonitrile. Carboxylic acids are an important group of polar compounds with many industrial and commercial uses and applications. In South Africa, these carboxylic acids together with many other oxygenates and hydrocarbons are manufactured by SASOL using the Fischer–Tropsch process. The separation of these acids from hydrocarbons is a commercially viable option, and is an important reason for this study. This work focuses on the use of sulfolane in effecting separation by solvent extraction and not by the more common and energy intensive method of distillation. Sulfolane was chosen because of its high polarity and good solvent extraction properties.
The first part of this study involves the determination of excess molar volumes (VmE) of binary mixtures of sulfolane (1) + carboxylic acids (2) at different temperatures of 303.15 K and 308.15 K, where carboxylic acids refer to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid respectively. The densities of the binary systems of sulfolane (1) + carboxylic acids (2) were measured at T = 303.15 K and 308.15 K. The excess molar volumes were calculated from the experimental densities at each temperature. The VmE were negative for the entire mole fractions for all the binary systems. It was found that the VmE in the systems studied increase with an increase in temperature, and also VmE decreases with an increase in the carbon chain length of the carboxylic acid. The VmE data results were correlated using Redlich-Kister equation.
Abstract ii
The second part was the study of the binodal or solubility curves and tie line data for the ternary systems of [sulfolane (1) + carboxylic acids (2) + hydrocarbons (3)] and [acetonitrile (1) + carboxylic acids (2) + hydrocarbon (3)].
Hydrocarbons refer to pentane, hexane, dodecane and hexadecane. The binodal curve experimental data was determined by the cloud point technique. Liquid-liquid equilibrium (LLE) phase diagrams were constructed using the mole fractions and refractive indices (nD). Tie line data were obtained for the sulfolane-rich and hydrocarbon-rich phases as well as the acetonitrile-rich and hydrocarbon-rich phases respectively. The tie lines in both cases were skewed towards the hydrocarbon-rich phases indicating that relative mutual solubility of carboxylic acids is higher in the hydrocarbon-rich phase than in the solvent-rich phase. Selectivity values were calculated from the tie-lines to determine the extraction capabilities of solvents sulfolane and acetonitrile. Selectivity values in all cases were greater than one, meaning that both sulfolane and acetonitrile can be used to separate carboxylic acids from hydrocarbons. Binodal curve data were correlated by the Hlavatý, beta (𝛽) and log𝛾 equations; average standard deviation error for Hlavatý was 0.012, for beta (𝛽), 0.023 and for log𝛾, 0.021. The NRTL and UNIQUAC models were used to correlate the experimental tie-lines. The calculated values based on the NRTL equation were found to be better than those based on UNIQUAC equation; the average root-mean square deviation, (rmsd), between the phase composition obtained from experiment and that from calculation was 0.061 for the NRTL model, as compared to 0.358 for UNIQUAC model for the ternary systems involving sulfolane. For ternary systems of acetonitrile, the NRTL equation was better than the UNIQUAC with the rsmd of 0.003 and 0.287for UNIQUAC equation. / DUT Postgraduate Development and Support Directorate (PGDS)
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Phase equilibrium studies of sulfolane mixtures containing carboxylic acidsSithole, Nompumelelo Pretty January 2012 (has links)
Submitted in fulfilment of the academic requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / In this work, the thermodynamics of ternary liquid mixtures involving carboxylic acids with sulfolane, hydrocarbons including cycloalkane, and alcohols are presented. In South Africa, Sasol is one of the leading companies that produce synthesis gas from low grade coal. Carboxylic acids together with many other oxygenate and hydrocarbons are produced by Sasol using the Fischer-Tropsch process. Carboxylic acids class is one of the important classes of compounds with great number of industrial uses and applications. The efficient separation of carboxylic acids from hydrocarbons and alcohols from hydrocarbons is of economic importance in the chemical industry, and many solvents have been tried and tested to improve such recovery. This work focussed on the use of the polar solvent sulfolane in the effective separation by solvent extraction and not by more common energy intensive method of distillation.
The first part of the experimental work focussed on ternary liquid-liquid equilibria of mixtures of [sulfolane (1) + carboxylic acid (2) + heptane (3) or cyclohexane or dodecane] at T = 303.15 K, [sulfolane (1) + alcohol (2) + heptane (3)] at T = 303.15 K. Carboxylic acid refers to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid. Alcohol refers to methanol, ethanol, 1- propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol. Ternary liquid- liquid equilibrium data are essential for the design and selection of solvents used from liquid- liquid extraction process.
Abstract vi
The separation of carboxylic acids from hydrocarbons and the alcohols from hydrocarbons is commercially lucrative consideration and is an important reason of this study. The separation of carboxylic acids or alcohols from hydrocarbons by extraction with sulfolane was found to be feasible as all selectivity values obtained are greater than 1.
The modified Hlavatý, beta (β) and log equations were fitted to the experimental binodal data measured in this work. Hlavatý gave the best overall fit as compared to beta ( ) and log function.
The NRTL (Non-Random, Two Liquid) and UNIQUAC Universal Quasichemical) model were used to correlate the experimental tie-lines and calculate the phase compositions of the ternary systems. The correlation work served three purposes:
to summarise experimental data
to test theories of liquid mixtures
prediction of related thermodynamics properties.
The final part of the study was devoted to the determination of the excess molar volumes of mixtures of [sulfolane (1) + alcohol (2)] at T = 298.15 K, T = 303.15 K and T = 309.15 K. Density was used to determine the excess molar volumes of the mixtures of [sulfolane (1) + alcohols (2)]. Alcohol refers to methanol, ethanol, 1- propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol.
The work was done to investigate the effect of temperature on excess molar volumes of binary mixtures of alcohols and sulfolane, as well as to get some idea of interactions involved between an alcohol and sulfolane. The excess molar volume data for each binary mixture was fitted in the Redlich–Kister equation to correlate the composition dependence of the excess property. / National Research Foundation
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Phase equilibrium studies of sulfolane mixtures containing carboxylic acidsSithole, Nompumelelo Pretty 20 August 2012 (has links)
Submitted in fulfilment of the academic requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2012. / National Research Foundation
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Organic acids as potential growth promoters in abalone cultureGoosen, Neill Jurgens 12 1900 (has links)
ENGLISH ABSTRACT: The first successful captive spawning of the South African abalone Haliotis midae occurred in
the 1980’s and subsequently the commercial abalone industry in South Africa has
developed, with an estimated investment of US$ 12 million and annual output of 500 to 800
tons by 2001, making South Africa the biggest abalone producer outside of Asia. Natural
kelp is currently the major feed and the development of a suitable substitute, and improved
disease management in abalone culture are seen as the primary factors limiting expansion of
the industry in South Africa. Further, abalone growth rates are very slow and improvements
in growth rate will lead to shortened production times with benefits to producers. Diseases in
aquaculture have traditionally been combated using antibiotics as treatment (therapeutic
usage) and preventative measure (prophylactic usage). In terrestrial livestock management,
antibiotics are also used as growth promoters. The use of antibiotics in aquaculture has
recently sparked concerns about the development of antibiotic resistance in pathogens of
humans and aquaculture organisms, and alternative strategies to using antibiotics mainly
focus on manipulating the microbial composition in the host organism, in order to establish a
beneficial microbial population to prevent disease.
The role that organic acids and their salts can play as growth promoters in the South African
abalone Haliotis midae, and as manipulators of the gut microflora of this species of abalone
was investigated and compared to the effects of antibiotics. Three different treatments were
tested against a negative control and a positive control containing 30ppm avilamycin, a
commercial antibiotic growth promoter (AGP) used in the pig and poultry industry. The 3
treatments consisted of 1% acetic and 1% formic acid (treatment AF), 1% sodium benzoate
and 1% potassium sorbate (treatment SBPS), and 1% benzoic and 1% sorbic acid
(treatment BS). Three different experiments were conducted to test the effects of the different
acids and salts. The first experiment was under controlled optimum water temperature
conditions (16.5ºC), another at elevated water temperature (20.5ºC) in order to test response
during temperature stress conditions, and the final trial was conducted under uncontrolled
practical production conditions. In an attempt to establish the mechanism by which the
treatments have their effects (if any), the composition of the gut microflora of the abalone
was monitored. It was found that the organic acids and salts investigated can enhance the growth rate of
Haliotis midae in the size class 23 mm to 33 mm mean length significantly when compared to
both control treatments. It was further found that the tested AGP had no effect on growth
rate. None of the treatments had a significant effect on feed conversion ratio (FCR),
Incidence cost (IC) or feed intake. It could also not be shown that the treatments affected the
intestinal microflora of the abalone, although this might be due to inadequate microbiological
methods. The mechanism by which the acids and salts have their effects could not be
established.
It was found that the animals in the controlled system underwent an initial adaptation period,
which led to improvement in specific growth rate (SGR), FCR and IC as the experiment
progressed during the controlled optimal conditions experiment. Large differences in FCR
and IC was seen for controlled optimal conditions and production conditions which means
that there is still a large scope for developing methods to improve practical on-farm feed
utilisation by abalone.
SGR, FCR and IC were negatively influenced by raising water temperature from 16.5ºC to
20.5ºC. The composition of the gut microflora of the abalone also changed significantly after
the water temperature was raised. It appears that animal weight gain and shell growth
respond differently to changing water temperatures, which is reflected in a change in Fulton
condition factor.
A relationship between the length and weight of abalone between 15 mm and 47 mm was
established and it was found that Haliotis midae does not follow an isometric growth
relationship. This relation can be used as a tool to improve farm management and therefore
also profitability.
Various micro-organisms were isolated from Haliotis midae during the trial, but their
relationship and interaction with abalone is not clear. Clear dominance by specific species of
bacteria was observed during certain periods.
The current research has clearly showed the potential of organic acids and their salts to act
as growth promoters in the South African abalone Haliotis midae, with application in both the
local aquaculture and feed manufacturing industries. The possibility further exists that some
aspects of the current research can be adapted to be applicable in other abalone species
and even in other aquaculture species. / AFRIKAANSE OPSOMMING: Die eerste suksesvolle aanteel van die Suid-Afrikaanse perlemoen Haliotis midae in
gevangeskap is in die 1980’s gerapporteer, waarna ‘n suksesvolle akwakultuur industrie
ontwikkel het met ‘n geskatte produksievermoë van 500 tot 800 ton en kapitaalbelegging van
US$ 12 miljoen in 2001. Suid-Afrika is tans die grootste perlemoen-produserende land wat
buite Asië geleë is. Die ontwikkeling van ‘n geskikte alternatiewe voedselbron vir natuurlike
kelp (tans die algemeenste voedselbron wat gebruik word in die kweek van perlemoen),
sowel as verbeterde siektebestryding word tans gesien as die hooffaktore wat verdere
uitbreiding in die Suid-Afrikaanse industrie beperk. Perlemoen het verder baie stadige
groeitempo’s en enige verbetering in hierdie verband sal produksietye verkort en dus
produsente bevoordeel. Siektes in akwakultuur word tradisioneel bestry deur gebruik te
maak van antibiotiese behandeling (terapeutiese bestryding) of van voorkomende
behandeling (profilaktiese bestryding). In gewone diereproduksie-sisteme (bv. varke en
hoenders) word antibiotika ook gebruik as groeistimulante. Die gebruik van antibiotika in
akwakultuur het onlangs die bekommernis laat ontstaan dat sekere menslike en dierepatogene
weerstand kan ontwikkel teen sommige middels, wat die behoefte laat ontstaan het
om siektebestryding sonder die gebruik van antibiotika te ontwikkel. Alternatiewe strategieë
fokus grootliks daarop om die samestelling van die mikrobiese bevolking van die gasheer te
manipuleer en sodoende ‘n voordelige bevolking in die gasheer te vestig, wat dan siektes
voorkom.
Daar is ondersoek ingestel na die rol van organiese sure en hul soute as groeistimulante en
manipuleerders van die mikrobiese bevolking in die Suid-Afrikaanse perlemoen Haliotis
midae. Drie verskillende behandelings is getoets en vergelyk met beide ‘n negatiewe- en
positiewe kontrole (wat 30 dele per miljoen van ‘n kommersiële antibiotiese groeistimulant
bevat het). Die drie formulasies het onderskeidelik bestaan uit ‘n mengsel van 1% etanoëen
1% metanoësuur (behandeling AF), 1% bensoë- en 1% sorbiensuur (behandeling BS) en
1% natriumbensoaat en 1% kaliumsorbaat (behandeling SBPS). Om die effekte van hierdie
formulasies te toets, is daar 3 proewe gedoen. Een proef is gedoen onder temperatuurbeheerde
toestande teen ‘n optimum watertemperatuur van 16.5ºC terwyl ‘n ander gedoen is
onder onbeheerde, praktiese produksie-omstandighede. ‘n Verdere beheerde proef is
gedoen teen ‘n watertemperatuur van 20.5ºC om die effek van die verskillende formulasies te
toets wanneer die diere aan temperatuur-spanning blootgestel word. Die samestelling van
die mikrobiese bevolking in die dunderm van die perlemoen is deurentyd gemonitor in ‘n poging om die meganisme vas te stel waarvolgens die sure en soute hul effek het, indien
daar enige effek waargeneem word.
Daar is gevind dat die onderskeie sure en suursoute die groeitempo van Haliotis midae met
‘n gemiddelde lengte van 23 mm tot 33 mm beduidend kan verhoog in vergelyking met die
groeitempo’s van beide kontroles. Daar is gevind dat die antibiotiese groeistimulant geen
effek het op die groei van die diere nie en dat geen behandelings ‘n beduidende effek op
voeromsetting, voerkoste of voerinname gehad het nie. Daar kon nie bewys word dat enige
van die formulasies of die antibiotika ‘n effek gehad het op die mikrobes in die
spysverteringskanaal van die perlemoene in die sisteem nie, alhoewel die gebrek aan ‘n
effek moontlik toegeskryf kan word aan die onakkurate en onvoldoende mikrobiologiese
metodes wat gebruik is tydens die studie. Die meganisme waarvolgens die sure werk kon
nie vasgestel word nie.
Daar is verder gevind dat die diere in die temperatuur-beheerde eksperiment aanvaklik deur
‘n aanpassingsperiode gegaan het, wat tot gevolg gehad het dat die spesifieke groeitempo,
voeromsetting en voerkoste verbeter het met die verloop van die eksperiment. Daar is groot
verskille gevind in die voeromsetting van beheerde optimale toestande en onbeheerde
produksietoestande, wat impliseer dat daar nog baie ruimte en geleenthede is om metodes
te ontwikkel wat beter voeromsetting bewerkstellig tydens perlemoenproduksie.
Spesifieke groeitempo, voeromsetting en voerkoste is nadelig beïnvloed toe die
watertemperatuur verhoog is vanaf 16.5ºC na 20.5ºC. Die samestelling van die mikrobiese
bevolking in die spysverteringskanaal van die perlemoen het ook beduidende veranderinge
ondergaan tydens hierdie temperatuur verhoging. Dit wil voorkom asof die lengtegroei van
die dop en die toename in massa verskillend reageer op ‘n verandering in watertemperatuur
en hierdie effek word weerspieël in die verandering in Fulton-kondisiefaktor.
‘n Verwantskap tussen totale doplengte en totale gewig van Haliotis midae kon vasgestel
word vir diere tussen 15 mm en 47 mm en daar is gewys dat H. midae nie ‘n isometriese
groeipatroon volg nie. Hierdie verwantskap kan aangewend word tydens produksiebestuur
om produksie te verbeter en daardeur ook winsgewendheid te verhoog.
Verskeie mikrobes is tydens die verloop van die proef geïsoleer, maar die rol van en
interaksie tussen hierdie mikrobes en die Suid-Afrikaanse perlemoen is nie duidelik nie.
Sekere bakterieë het die mikrobiese bevolking in die spysverteringskanaal van die
perlemoen in hierdie proef oorheers tydens sekere groeiperiodes. Die huidige navorsing het duidelik aangetoon dat organiese sure en hul soute as
groeistimulante kan optree in die Suid-Afrikaanse perlemoen Haliotis midae, met toepassings
in die plaaslike akwakultuur- en voervervaardigins-industrieë. Dit beskik verder oor die
potensiaal om aangepas te word sodat dit toepaslik is in ander perlemoenspesies en selfs
ander akwakultuur organismes.
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Application of modern analytical techniques and chemometric methods to the chemical characterisation of South African wines : determination of non-volatilesDe Villiers, A. J. (Andre Joubert) 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The present study deals in the first instance with the improvement of current analytical
techniques for the analysis of the non-volatile content of wines. An improved sample
preparation method, using solid phase extraction (SPE), was initially developed for the
analysis of organic acids, sugars and phenolic compounds. Consequently, modem
analytical methodologies were assessed to obtain optimal techniques for the separation of
various non-volatile compounds. A capillary electrophoresis (CE) method, demonstrably
more reliable than currently used high performance liquid chromatography (HPLC) and CE
methods, is proposed for the analysis of organic acids. HPLC with refractive index (RI) or
evaporative light scattering detection (ELSD) proved more suitable than CE for the analysis
of sugars in dry wines. Liquid-chromatography-mass spectroscopy (LC-MS) offered
superior sensitivity and resolution compared to the relatively new technique of CE-MS for
the analysis of wine phenolics. LC-MS was further applied for the efficient and sensitive
analysis of non-coloured phenolics and anthocyanins in wine. Negative- and positive
electrospray ionisation, respectively, were used in conjunction with an ion-trap mass
analyzer, for the identification of 34 phenolics and 31 anthocyanins in red wine samples.
Complementary CE and LC methods were developed to allow the identification of artificial
dyes in red wines, added illegally to improve their colour. Also, the application of stir bar
sorptive extraction (SBSE) with liquid desorption and micellar electrokinetic
chromatography (MEKC) for the analysis of bitter acids in beer is reported.
In the second part of the thesis, the analytical results obtained for South African red and
white wines were evaluated. Following comparison of the results with literature reports,
several pattern recognition techniques were employed. A classification function obtained by
linear discriminant analysis (LDA) was used to classify both red and white wines according
to variety, based on their chemical composition. This classification is achieved independent
of the factors of wine age or geographical origin, making it useful for authenticity
evaluation. / AFRIKAANSE OPSOMMING: Hierdie studie het as primêre doel die verbetering van bestaande analitiese metodes vir die
analise van nie-vlugtige komponente in wyn. In die lig hiervan, is eerstens 'n toepaslike
monster-voorbereidingstegniek, gebasseer op soliede fase ekstraksie (SPE), ontwikkel vir
die gelyktydige analise van organise sure, suikers en fenoliese komponente vanuit die wyn
matriks. Vervolgens is moderne analitiese rtietodes ondersoek en gepastde
skeidingstegnieke is ontwikkel vir die verskillende chemiese wyn-komponente. Kappillêre
elektroforese (CE) en hoë-druk vloeistof-chromatografie (HPLC) in kombinasie met
verskeie deteksie-metodes is vergelyk. Hieruit is 'n verbeterde CE metode vir die analise
van organise sure is ontwikkel, terwyl HPLC in kombinasie met refraksie-indeks- en
verdampings lig verstrooiings deteksie (ELSD) die beste resultate lewer vir die analise van
suikers in droë wyne. Die toepasbaarheid van vloeistof-chromatografie met massa
spektrometriese deteksie (LC-MS) vir die analise van fenoliese komponente is
gedemonstreer, terwyl CE-MS onvoldoende resolusie en sensitiwiteit toon vir die analises.
LC-MS is vervolgens ook gebruik vir die identifikasie van 34 fenoliese verbindings en 31
antosianiede in rooi wyn. Komplementêre HPLC en CE metodes is ontwikkel vir die
identifikasie van onwettige sintetiese kleurstowwe in' rooi wyn. 'n Addisionele monstervoorbereidingsstap,
roerstaaf sorptiewe ekstraksie (SBSE), is saam met vloeistof-desorpsie
en misellêre elektrokinetiese chromatografie (MEKC) gebruik vir die analise van hops
bitter sure in bier.
In die tweede deel van die tesis word die resultate verkry m.b.v. bg. tegnieke vir die analise
van Suid-Afrikaanse rooi- en wit wyne, bespreek. Die resultate is vergelyk met waardes uit
die literatuur, en verskeie statistiese metodes is gebruik om die data te ondersoek. Met
behulp van chemometriese metodes is 'n klassifikasie funksie verkry wat die klassifikasie
van Suid-Afrikaanse wyne volgens druifsoort, gebasseer op die chemiese samestelling van
die wyne, toelaat. Die klassifikasie is moontlik, onafhanklik van die ouderdom of
geografiese oorsprong van die wyne.
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Development of analytical methodologies for the determination of metals and organic acids in environmental and traditional Chinesemedicine studies by capillary electrophoresis董豪珊, Tung, Ho-shan. January 2000 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
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Stanovení perfluorovaných organických kyselin v půdách chromatografickými metodami / Stanovení perfluorovaných organických kyselin v půdách metodou plynové chromatografieOkáľová, Zuzana January 2014 (has links)
A method employing solid-liquid extraction with methanol and solid-phase extraction (SPE) clean-up step using Supelco SupelcleanTM ENVITM -Carb 3 mL cartridges (0.25 g graphitized carbon adsorbent) followed by gas chromatography - mass spectrometry with negative chemical ionization (GC-NCI-MS) has been optimized and applied for determination of ultratrace concentrations of C6 - C12 perfluorinated carboxylic acids (PFCAs) in soil samples. A sophisticated multifactorial statistic method, response surface methodology, employing 1/16 fractional factorial design and the face centered central composite design as well has been applied to find the significant parameters which influence the extraction procedure of PFCAs and SPE clean-up step and to set the optimum extraction and clean-up levels of eight parameters evaluated yielding the maximum extraction recovery of all PFCAs. The analyte extraction recoveries and the limits of detection and quantification have been obtained. The recoveries of individual PFCAs were within a range from 85 to 100 % for analyte spiked concentration level of 1.1 ng g−1 and within a range from 91 to 107 % for analyte spiked level of 2.1 ng g−1 . The values of limits of detection were 1.9 - 3.0 pg g−1 and limits of quantification 6.4 - 10.1 pg g−1 . This analytical method has...
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Production of levulinic acid from sugarcane bagasseMthembu, Lethiwe Debra January 2016 (has links)
Submitted in fulfillment of the academic requirements for the Masters in Applied Sciences (Chemistry), Durban University of Technology, Durban, South Africa, 2016. / The main aim of this work was to produce levulinic acid (LA) from sugarcane bagasse (SB) and since there is approximately 3 000 000 tons of bagasse produced per annum by 16 factories that are located on the north coast of Kwa-Zulu Natal, after the extraction of sugar.
For this project fructose was firstly used for the production of LA, thereafter SB was used to produce LA. Cellulose was extracted from sugarcane bagasse using two types of pre-treatments namely (i) acid-alkali pre-treatment and (ii) liquid hot water (LHW). In the latter method acid hydrolysis and enzymatic hydrolysis was used to hydrolyse cellulose to glucose.
For the acid-alkali pre-treatment work, two types of bagasse was used namely (i) mill-run bagasse and (ii) depithed bagasse and for the LHW a mill-run bagasse (pellets form) was used.
In both pre-treatment methods the glucose solution was then acid catalysed by two different acids (i) an environment friendly acid, methanesulfonic acid (MSA) and (ii) sulphuric acid, producing levulinic acid. The results showed that MSA and sulphuric acid produced almost the same yield of LA but, MSA is preferred for the production of LA since it is less toxic and less corrosive than sulphuric acid. / M
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