Publications by authors named "Michael J Angove"

28 Publications

  • Page 1 of 1

Semi-Solid and Solid Dosage Forms for the Delivery of Phage Therapy to Epithelia.

Pharmaceuticals (Basel) 2018 Feb 26;11(1). Epub 2018 Feb 26.

Department of Pharmacy and Applied Science, La Trobe Institute for Molecular Science, La Trobe University Bendigo Campus, PO Box 199, Bendigo 3550, Australia.

The delivery of phages to epithelial surfaces for therapeutic outcomes is a realistic proposal, and indeed one which is being currently tested in clinical trials. This paper reviews some of the known research on formulation of phages into semi-solid dosage forms such as creams, ointments and pastes, as well as solid dosage forms such as troches (or lozenges and pastilles) and suppositories/pessaries, for delivery to the epithelia. The efficacy and stability of these phage formulations is discussed, with a focus on selection of optimal semi-solid bases for phage delivery. Issues such as the need for standardisation of techniques for formulation as well as for assessment of efficacy are highlighted. These are important when trying to compare results from a range of experiments and across different delivery bases.
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http://dx.doi.org/10.3390/ph11010026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874722PMC
February 2018

The effect of inositol hexaphosphate on cadmium sorption to gibbsite.

J Colloid Interface Sci 2016 Jul 20;474:159-70. Epub 2016 Apr 20.

La Trobe University, P.O. Box 199, Bendigo, Vic. 3552, Australia.

Hypothesis: Oxides, hydrous oxides and hydroxides of aluminium and iron are important in determining the availability of trace and heavy metals in soil systems. The presence of complexing anions is also known to affect the binding of these metals in soils. Since organophosphates, such as inositol hexaphosphate (IP6), are present in most soil systems they are expected to affect the nature of the interaction between metal ions and metal (hyr)oxides.

Experiments: Both adsorption edge and isotherm experiments were conducted on Cd(II)-gibbsite and Cd(II)-IP6-gibbsite systems. In addition, solid-state (31)P MAS NMR measurements were performed on the ternary system. All results were used to develop Extended Constant Capacitance surface complexation models of both the Cd(II)-gibbsite and IP6-Cd(II)-gibbsite sorption systems.

Findings: The presence of IP6 significantly increased sorption of Cd(II) to gibbsite below pH 8 especially at higher concentrations of Cd(II) and IP6. The (31)P MAS NMR spectra, together with surface complexation modeling, indicated the presence of two outer-sphere ternary complexes with the first, [(SOH2)3(3+)(LHCd)(9-)](6-), important at relatively low concentrations, while the second, [SLH3(8-)Cd(2+)](6-), dominated sorption at higher sorbate concentrations. Thus the presence of organophosphates in soil systems increases sorption and may therefore decrease the availability of trace and heavy metals to plants.
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http://dx.doi.org/10.1016/j.jcis.2016.04.028DOI Listing
July 2016

Synthesis, structure elucidation, DNA-PK and PI3K and anti-cancer activity of 8- and 6-aryl-substituted-1-3-benzoxazines.

Eur J Med Chem 2016 Mar 27;110:326-39. Epub 2016 Jan 27.

Pharmacy and Applied Science, La Trobe Institute for Molecular Science, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia. Electronic address:

The synthesis of 6-aryl, 8- aryl, and 8-aryl-6-chloro-2-morpholino-1,3-benzoxazines with potent activity against PI3K and DNA-PK is described. Synthesis of thirty one analogues was facilitated by an improved synthesis of 3-bromo-2-hydroxybenzoic acid 13 by de-sulphonation of 3-bromo-2-hydroxy-5-sulfobenzoic acid 12 en route to 2-methylthio-substituted-benzoxazine intermediates 17-19. From this series, compound 20k (LTURM34) (dibenzo[b,d]thiophen-4-yl) (IC50 = 0.034 μM) was identified as a specific DNA-PK inhibitor, 170 fold more selective for DNA-PK activity compared to PI3K activity. Other compounds of the series show markedly altered selectivity for various PI3K isoforms including compound 20i (8-(naphthalen-1-yl) a potent and quite selective PI3Kδ inhibitor (IC50 = 0.64 μM). Finally, nine compounds were evaluated and showed antiproliferative activity against an NCI panel of cancer cell lines. Compound 20i (8-(naphthalen-1-yl) showed strong anti-proliferative activity against A498 renal cancer cells that warrants further investigation.
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http://dx.doi.org/10.1016/j.ejmech.2016.01.042DOI Listing
March 2016

Walnuts (Juglans regia) Chemical Composition and Research in Human Health.

Crit Rev Food Sci Nutr 2016 Jun;56(8):1231-41

a School of Pharmacy, La Trobe University , Victoria , Australia.

Walnuts are among the most widely consumed commercially grown tree nuts in the world. Many health benefits have been claimed for the consumption of these, including reduced risk of cardiovascular disease, coronary heart disease, type II diabetes treatment, and prevention and treatment of certain cancers, and the lessening of symptoms attributed to age-related and other neurological disorders. The health-promoting benefits of walnut consumption are ascribed to its fatty acid profile, which is rich in polyunsaturated fatty acids with a particularly high ω3:ω6 ratio-the highest among all the tree nuts. The content of polyphenols and other phytochemicals in walnuts, with their claimed cytotoxic properties, also make them an attractive candidate for research for the prevention of free radical-induced nucleic acid damage. Research of walnut consumption in humans and animals employing a range of data sets and statistical methods suggest that walnuts may be considered a safe potential nutraceutical or possibly pharmaceutical substance. Nevertheless, few reviews of scientific research on the proposed benefits of these nuts exist, in spite of the numerous claims attributed to them in the lay media. This brief review article attempts to disseminate much of the information surrounding walnut consumption, and human health benefits, to other scientists and the interested general reader.
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http://dx.doi.org/10.1080/10408398.2012.760516DOI Listing
June 2016

Surface complexation modeling of inositol hexaphosphate sorption onto gibbsite.

J Colloid Interface Sci 2015 Feb 15;440:282-91. Epub 2014 Nov 15.

La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia. Electronic address:

The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, (31)P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. (31)P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, -6, -13 and -21ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and (31)P MAS NMR data, IP6 sorption to gibbsite was modeled with an extended constant capacitance model (ECCM). The adsorption reactions that best described the sorption of IP6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex: ≡AlOH + IP₆¹²⁻ + 5H⁺ ↔ ≡Al(IP₆H₄)⁷⁻ + H₂O, ≡3AlOH + IP₆¹²⁻ + 6H⁺ ↔ ≡Al₃(IP₆H₃)⁶⁻ + 3H₂O, ≡2AlOH + IP₆¹²⁻ + 4H⁺ ↔ (≡AlOH₂)₂²⁺(IP₆H₂)¹⁰⁻. The inner-sphere complex involving three surface sites may be considered to be equivalent to a surface precipitate. Thermodynamic parameters were obtained from equilibrium constants derived from surface complexation modeling. Enthalpies for the formation of inner-sphere surface complexes were endothermic, while the enthalpy for the outer-sphere complex was exothermic. The entropies for the proposed sorption reactions were large and positive suggesting that changes in solvation of species play a major role in driving the sorption process.
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http://dx.doi.org/10.1016/j.jcis.2014.10.065DOI Listing
February 2015

Synthesis, DNA-PK inhibition, anti-platelet activity studies of 2-(N-substituted-3-aminopyridine)-substituted-1,3-benzoxazines and DNA-PK and PI3K inhibition, homology modelling studies of 2-morpholino-(7,8-di and 8-substituted)-1,3-benzoxazines.

Eur J Med Chem 2012 Nov 5;57:85-101. Epub 2012 Sep 5.

School of Pharmacy and Applied Science, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia.

A number of new 2-(pyridin-3-ylamino)-4H-(substituted) benz[e]-1,3-oxazin-4-ones were synthesized 10a-g. These were then reacted with the hydro-halogen salt of 2, 3 and 4-(halo-methyl) pyridine in the presence of Cs(2)CO(3) to give eighteen new 2-(N-substituted (pyridin-3-ylmethyl) amino)-substituted-1,3-benzoxazines (compounds 11a-i, 13a-c, and 15a-f). X-ray crystallography was used to confirm that the 2-N-substituted structures 11 and 13 were formed rather than the 3-N-substitution analogues 12 and 14. Eleven of the new compounds were tested for their effect on collagen induced platelet aggregation and it was found that the most active inhibitory compound was 8-methyl-2-(pyridin-3-yl(pyridin-3-ylmethyl)amino)-7-(pyridin-3-ylmethoxy)-4H-benz[e]-1,3-oxazin-4-one 15e with an IC(50) of 10 ± 2 μM. DNA-dependent protein kinase (DNA-PK) inhibition data for 12 previously prepared 2-morpholino substituted-1,3-benzoxazines (compounds 19-31) were measured and showed high to moderate activity where the most active compound was compound 27 with an IC(50) of 0.28 μM. Furthermore DNA-PK inhibition data for six newly prepared 2-(N-substituted (pyridin-3-ylmethyl) amino)-substituted-1,3-benzoxazines (compounds 11b, 13a-b, 15a-b and 15e) and 8-methyl-7-(pyridin-3-ylmethoxy)-3-(pyridin-3-ylmethyl)-2H-benz[e]-1,3-oxazin-2,4(3H)-dione 17d were measured and moderate to low inhibitory activity was observed, with the most active of the compounds in this series being 8-methyl-2-(pyridin-3-yl(pyridin-3-ylmethyl)amino)-7-(pyridin-3-ylmethoxy)-4H-benz[e]-1,3-oxazin-4-one 15e with an IC(50) of 2.5 μM. PI3K inhibition studies revealed that compound 27 is highly potent (IC(50) for PI3Kα = 0.13 μM, PI3Kβ = 0.14 μM, PI3Kγ = 0.72 μM, PI3Kδ = 2.02 μM). Compound 22 with 7-[2-(4-methylpiperazin-1-yl)ethoxy] group shows greater inhibition of DNA-PK over PI3K. Docking of some 2-morpholino-substituted-1,3-benzoxazine compounds 19-31 within the binding pocket and structure-activity relationships (SAR) analyses were performed with results agreeing well with observed activities.
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http://dx.doi.org/10.1016/j.ejmech.2012.08.035DOI Listing
November 2012

Inhibition of uranium(VI) sorption on titanium dioxide by surface iron(III) species in ferric oxide/titanium dioxide systems.

Environ Sci Technol 2012 Oct 5;46(20):11128-34. Epub 2012 Oct 5.

Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia.

Uranium (U(VI)) sorption in systems containing titanium dioxide (TiO(2)) and various Fe(III)-oxide phases was investigated in the acidic pH range (pH 2.5-6). Studies were conducted with physical mixtures of TiO(2) and ferrihydrite, TiO(2) with coprecipitated ferrihydrite, and with systems where Fe(III) was mostly present as crystalline Fe(III) oxides. The presence of ferrihydrite resulted in decreased U(VI) sorption relative to the pure TiO(2) systems, particularly below pH 4, an unexpected result given that the presence of another sorbent would be expected to increase U(VI) uptake. In mixtures of TiO(2) and crystalline Fe(III) oxide phases, U(VI) sorption was higher than for the analogous mixtures of TiO(2) with ferrihydrite, and was similar to U(VI) sorption on TiO(2) alone. X-ray absorption spectroscopy of the TiO(2) system with freshly precipitated Fe(III) oxides indicated the presence of an Fe(III) surface phase that inhibits U(VI) sorption-a reaction whereby Fe(III) precipitates as lepidocrocite and/or ferrihydrite effectively blocking surface sorption sites on the underlying TiO(2). Competition between dissolved Fe(III) and U(VI) for sorption sites may also contribute to the observed decrease in U(VI) sorption. The present study demonstrates the complexity of sorption in mixed systems, where the oxide phases do not necessarily behave in an additive manner, and has implications for U(VI) mobility in natural and impacted environments where Fe(III) (oxyhydr)oxides are usually assumed to increase the retention of U(VI).
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http://dx.doi.org/10.1021/es302574jDOI Listing
October 2012

An investigation of the mode of sorption of inositol hexaphosphate to goethite.

J Colloid Interface Sci 2012 Feb 2;367(1):436-42. Epub 2011 Oct 2.

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia.

Adsorption of inositol hexaphosphate (IP(6)) on goethite has been studied as a function of pH and concentration, and by use of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). While adsorption was highest at low pH, a significant amount remained adsorbed above pH 10 where, in the absence of IP(6), the surface is expected to have a net negative charge. The adsorption isotherm at pH 5.5 indicated strong binding to the surface with each adsorbed species occupying about 2.5 nm(2). ATR-FTIR spectra of IP(6) solutions in the pH range from 2 to 12 were fitted with a single set of IR bands which were assigned primarily by analogy with phosphate spectra. From its variation in intensity with pH the band at 1040 cm(-1) was assigned to the effect of hydrogen bonding on the PO vibration. No additional bands were required to fit the spectra of IP(6) adsorbed to goethite, indicating that adsorption occurs by outer-sphere complexation in this system. At all pH values studied the band associated with hydrogen bonding was more intense for the adsorbed species than in solution at the corresponding pH indicating that hydrogen bonding plays an important role in binding IP(6) to goethite.
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http://dx.doi.org/10.1016/j.jcis.2011.09.066DOI Listing
February 2012

Synthesis, structural elucidation, DNA-PK inhibition, homology modelling and anti-platelet activity of morpholino-substituted-1,3-naphth-oxazines.

Bioorg Med Chem 2011 Jul 24;19(13):3983-94. Epub 2011 May 24.

School of Pharmacy and Applied Science, La Trobe University, Bendigo, Australia.

A number of new angular 2-morpholino-(substituted)-naphth-1,3-oxazines (compound 10b), linear 2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 13b-c), linear 6, 7 and 9-O-substituted-2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 17-22, 24, and 25) and angular compounds 14-16 and 23 were synthesised. The O-substituent was pyridin-2yl-methyl (15, 18, and 21) pyridin-3yl-methyl (16, 19, and 22) and 4-methylpipreazin-1-yl-ethoxy (23-25). Twelve compounds were tested for their inhibitory effect on collagen induced platelet aggregation and it was found that the most active compounds were compounds 19 and 22 with IC(50)=55±4 and 85±4 μM, respectively. Furthermore, the compounds were also assayed for their ability to inhibit DNA-dependent protein kinase (DNA-PK) activity. The most active compounds were 18 IC(50)=0.091 μM, 24 IC(50)=0.191 μM, and 22 IC(50)=0.331 μM. Homology modelling was used to build a 3D model of DNA-PK based on the X-ray structure of phosphatidylinositol 3-kinases (PI3Ks). Docking of synthesised compounds within the binding pocket and structure-activity relationships (SAR) analyses of the poses were performed and results agreed well with observed activity.
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http://dx.doi.org/10.1016/j.bmc.2011.05.032DOI Listing
July 2011

Measuring 'hydrophobicity' of filamentous bacteria found in wastewater treatment plants.

Colloids Surf B Biointerfaces 2009 Sep 3;72(2):289-94. Epub 2009 May 3.

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia.

Attempts to measure the hydrophobicity of the cell surfaces of Gordonia amarae and Rhodococcus erythropolis, filamentous bacteria found in wastewater treatment plants, by several methods--microbial adhesion to hydrocarbons (MATH) or bacterial adhesion to hydrocarbons (BATH), contact angle, and micro-sphere adhesion to cells (MAC)--were unsuccessful. The results were erratic and inconsistent. This was in part because of the filamentous growth habit of G. amarae, but it was also a consequence of the fact that the 'hydrophobicity' of bacterial cells is not a clearly defined quantity. A technique is introduced in which bacteria are suspended in solutions of synthetic surfactants (non-ionic, cationic and anionic), and the suspensions aerated under defined conditions. The partitioning of bacterial cells between the foam and liquid phases was reproducible. The method was tested in model systems in which the bacteria were replaced by silica particles with defined surface modifications. Although this technique is not a direct measure of 'hydrophobicity', the partitioning of cells depends in part upon their surface hydrophobicity. In addition, qualitative information is gained about ionic interactions between the bacteria and the bubble surface. The results are pertinent to the problem of foaming in wastewater treatment plants.
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http://dx.doi.org/10.1016/j.colsurfb.2009.04.019DOI Listing
September 2009

The effect of filamentous bacteria on foam production and stability.

Colloids Surf B Biointerfaces 2008 May 4;63(1):21-6. Epub 2007 Nov 4.

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia.

Bacteria have been implicated in the formation of viscous brown foams that can appear suddenly on wastewater treatment plants. Three strains of the filamentous bacterium Gordonia amarae, isolated from wastewater treatment plants, were investigated to determine their effect on foam formation and stabilisation. During the exponential phase of the bacterial growth a biosurfactant was formed, causing a significant drop in the surface tension of the filtered medium and the formation of persistent foam. Foaming tests in the presence and absence of bacteria showed that bacteria increased foam persistence, most probably by reducing the drainage from the lamellae between bubbles. Experiments showed that > or =55% of the three bacterial strains partitioned into the foam produced by the biosurfactant, indicating that their surfaces were hydrophobic. The extent of partitioning was independent of the growth stage, suggesting that the cell surface hydrophobicity did not change with age, or with cell viability. This work shows that, although the G. amarae cells themselves do not cause foaming, they do produce biosurfactant, which aids foam formation, and they stabilise the foam by reducing the rate of drainage from the foam lamellae.
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http://dx.doi.org/10.1016/j.colsurfb.2007.10.011DOI Listing
May 2008

Sorption of chlorpyrifos to selected minerals and the effect of humic acid.

J Agric Food Chem 2007 Sep 4;55(18):7527-33. Epub 2007 Aug 4.

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

Sorption of chlorpyrifos (CPF) from 2.85 microM (1 mg/L) aqueous solutions in 0.01 M NaCl to montmorillonite, kaolinite, and gibbsite was investigated at 25 degrees C. Uptake of CPF by kaolinite and gibbsite was generally <10%, with pH having at most a small effect. Sorption to montmorillonite was significantly greater, with approximately 50% of the initial CPF being removed from solution below pH 5. Above pH 5 the sorption decreased to about 30%. About 70% of CPF was sorbed to kaolinite and gibbsite after 30 min, whereas on montmorillonite only 50% sorbed in an initial rapid uptake (approximately 30 min) followed by slower sorption, with a maximum achieved by 24 h. Although CPF desorbed completely from kaolinite in methanol, only about two-thirds was desorbed from montmorillonite. CPF has only a weak affinity for the surfaces of kaolinite and gibbsite. In the case of montmorillonite, sorption is significantly stronger and may involve a combination of sorption to external surfaces and diffusion into microporous regions. At pH >6 increased negative surface charge results in a lower affinity of CPF for the external surface. In the presence of 50 mg/L humic acid (HA) the amount of CPF sorbed on gibbsite and kaolinite was 3-4 times greater than that in the binary systems. The HA forms an organic coating on the mineral surface, providing a more hydrophobic environment, leading to enhanced CPF uptake. The HA coating on montmorillonite may reduce access of CPF to microporous regions, with CPF tending to accumulate within the HA coating.
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http://dx.doi.org/10.1021/jf071084zDOI Listing
September 2007

31P solid-state nuclear magnetic resonance study of the sorption of phosphate onto gibbsite and kaolinite.

Langmuir 2007 Mar 1;23(6):3205-13. Epub 2007 Feb 1.

Colloid and Environmental Chemistry Laboratory, La Trobe University, P. O. Box 199, Bendigo, Victoria 3552 Australia.

Sorption of phosphate onto gibbsite (gamma-Al(OH)3) and kaolinite has been studied by both macroscopic and 31P solid-state NMR measurements. Together these measurements indicate that phosphate is sorbed by a combination of surface complexation and surface precipitation with the relative amounts of these phases depending on pH and phosphate concentration. At low pH and high phosphate concentrations sorption is dominated by the presence of both amorphous and crystalline precipitate phases. The similarity between the single-pulse and CP/MAS NMR spectra suggests that the precipitate phases form a thin layer on the surface of the particles in close contact with protons from surface hydroxyl groups or coordinated water molecules. While the crystalline phase is only evident on samples below pH 7, amorphous AlPO4 was found at all pH and phosphate concentrations studied. As pH was increased the fraction of phosphate sorbed as an inner-sphere complex increased, becoming the dominant surface species by pH 8. Comparison of sorption and NMR results suggests that the inner-sphere complexes form by monodentate coordination to singly coordinated Al-OH sites on the edges of the gibbsite and kaolinite crystals. Outer-sphere phosphate complexes, which are readily desorbed, are also present at high pH.
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http://dx.doi.org/10.1021/la062765bDOI Listing
March 2007

Influence of temperature on the adsorption of mellitic acid onto kaolinite.

Langmuir 2006 Apr;22(9):4208-14

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of mellitic acid (benzene-1,2,3,4,5,6-hexacarboxylic acid) onto kaolinite was investigated at five temperatures between 10 and 70 degrees C. Mellitic acid adsorption increased with increasing temperature at low pH (below pH 5.5), but at higher pH, the effect of increasing temperature was to reduce the amount adsorbed. Potentiometric titrations were conducted, adsorption isotherms were measured over the same temperature range, and the data obtained were used in conjunction with adsorption edge and ATR-FTIR spectroscopic data to develop an extended constant capacitance surface complexation model of mellitic acid adsorption. A single set of reactions was used to model all data at the five temperatures studied. The model indicates that mellitic acid sorbs via outer-sphere complexation to surface hydroxyl (SOH) groups on the kaolinite surface rather than to permanent charge sites. The reactions proposed are SOH + L6- + 2H+ <-->[(SOH2)+(LH)5-]4- and SOH + L(6-) <--> [(SOH)(L)6-]6-. Thermodynamic parameters calculated from the temperature dependence of the equilibrium constants for these reactions indicate that the adsorption of mellitic acid onto kaolinite is accompanied by a large entropy increase.
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http://dx.doi.org/10.1021/la0534571DOI Listing
April 2006

Optimization of silylation using N-methyl-N-(trimethylsilyl)-trifluoroacetamide, N,O-bis-(trimethylsilyl)-trifluoroacetamide and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide for the determination of the estrogens estrone and 17alpha-ethinylestradiol by gas chromatography-mass spectrometry.

J Chromatogr A 2006 Mar 30;1108(1):121-8. Epub 2006 Jan 30.

Colloid and Environmental Chemistry Laboratory, La Trobe University, Bendigo, Vic. 3552, Australia.

This paper reports an improved silylation procedure for simultaneous determination of the steroid hormones 17alpha-ethinylestradiol (EE2) and estrone (E1) using gas chromatography-mass spectrometry (GC-MS). This follows a re-assessment of some of the popular silylation procedures using N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), N-O-bis-(trimethylsilyl)-trifluoroacetamide (BSTFA) and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA), which lead to the formation of trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBS) derivatives. Silylation of EE2 using MSTFA or BSTFA+1% TMCS in ethyl acetate, acetonitrile and dichloromethane solvents produced multiple peaks corresponding to TMS-E1, and 3-mono-TMS-EE2 and/or 3,17-di-TMS-EE2 in variable proportions depending on the solvent used. When pyridine or dimethyl formamide solvents were used in the silylation of EE2 under the same reaction conditions, only 3,17-di-TMS-EE2 derivative was formed. Derivatization using MTBSTFA reagents using ethyl acetate, acetonitrile, dichloromethane, pyridine and dimethyl formamide resulted in almost 100% conversion of mono-TBS-EE2 to the TBS-E1. Therefore, typical methods used in some previous GC-MS determinations of E1 and EE2 in environmental water and/or sediment samples are subject to speculation. However, we can confirm that any of the TMS reagents can be used with either pyridine or dimethyl formamide under suitable reaction conditions.
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http://dx.doi.org/10.1016/j.chroma.2005.12.098DOI Listing
March 2006

Sorption of bisphenol A, 17alpha-ethynylestradiol and estrone to mineral surfaces.

J Colloid Interface Sci 2006 May 18;297(1):62-9. Epub 2005 Nov 18.

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

Sorption of the endocrine disrupting chemicals (EDCs) bisphenol A (BPA), 17alpha-ethynylestradiol (EE2) and estrone (E1) from 3 microM aqueous solutions in 10 mM KNO3 to goethite, kaolinite and montmorillonite was investigated at 25 degrees C. Uptake of the EDCs by goethite and kaolinite suspensions was <20%, and little affected by pH. Sorption by montmorillonite was greater, ranging from 20 to 60%, and steadily increased from about pH 7. The amount of EDC sorbed to the mineral phases generally increased in the order of decreasing solubility (BPA
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http://dx.doi.org/10.1016/j.jcis.2005.10.039DOI Listing
May 2006

The influence of temperature on the adsorption of mellitic acid onto goethite.

J Colloid Interface Sci 2006 Apr 18;296(1):30-40. Epub 2005 Nov 18.

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of mellitic acid (benzene-1,2,3,4,5,6-hexacarboxylic acid) onto goethite was investigated at five temperatures between 10 and 70 degrees C. Mellitic acid adsorption increased with increasing temperature below pH 7.5, but at higher pH the effect of increasing temperature was to reduce the amount adsorbed. Potentiometric titrations were conducted and adsorption isotherms were measured over the same temperature range, and the data obtained were used in conjunction with adsorption edge data to develop an Extended Constant Capacitance Surface Complexation Model of mellitic acid adsorption. A single set of reactions was used to model the adsorption for the three different experiment types at the five temperatures studied. The adsorption reactions proposed for mellitate ion (L(6-)) adsorption at the goethite surface (SOH) involved the formation of two outer-sphere complexes: SOH + L(6-) + 3H+ <==> [(SOH2)+ (LH2)(4-)]3-, 2SOH + L(6-) + 2H+ <==> [(SOH2)2(2+) (L)(6-)]4-. This mechanism is consistent with recent ATR-FTIR spectroscopic measurements of the mellitate-goethite system. Thermodynamic parameters calculated from the temperature dependence of the equilibrium constants for these reactions indicate that the adsorption of mellitic acid onto goethite is accompanied by a large entropy increase.
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http://dx.doi.org/10.1016/j.jcis.2005.07.066DOI Listing
April 2006

The sorption of anthracene onto goethite and kaolinite in the presence of some benzene carboxylic acids.

J Colloid Interface Sci 2002 Mar;247(2):282-9

La Trobe University, Bendigo, P.O. Box 199, Bendigo, Victoria, 3552, Australia.

The uptake of anthracene from dilute aqueous solutions onto goethite and kaolinite was investigated at 25 degrees C, first in the absence and then in the presence of three benzene carboxylic acids: phthalic acid (benzene-1,2-dicarboxylic acid), trimesic acid (-1,3,5-), and mellitic acid (-1,2,3,4,5,6-). Carboxylic acid concentrations were 0.20, 0.10, and 0.05 mM. Anthracene (0.20 microM) did not adsorb strongly onto the pure mineral surfaces, but in the presence of phthalic acid a substantial increase in anthracene uptake was observed, particularly for the goethite systems. Trimesic and mellitic acids did not enhance anthracene uptake. Phthalate and proton adsorption data have been used to model phthalate adsorption onto the mineral surfaces using an extended constant capacitance surface complexation model. This model was then successfully adapted to account for the observed increase in anthracene uptake, where anthracene molecules were assumed to interact with adsorbed phthalate. We propose that the enhancement of anthracene adsorption in the presence of phthalic acid is due to an increase in the hydrophobicity of the mineral surface once phthalic acid molecules adsorb. The same effect was not observed for the other benzene carboxylates because of their greater polarity.
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http://dx.doi.org/10.1006/jcis.2001.8133DOI Listing
March 2002

Modeling the adsorption of Cd(II) onto Muloorina illite and related clay minerals.

J Colloid Interface Sci 2003 Jan;257(1):31-40

La Trobe University, Bendigo, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of Cd(II) onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. As the pH was increased, adsorption onto goethite occurred mainly in the pH range 5.5-8, whereas adsorption onto kaolinite occurred in two stages, separated by a plateau in the pH region 5.5 to 7. Adsorption onto illite increased steadily as the pH was increased, with far less Cd(II) adsorbing onto illite than onto goethite or kaolinite per m(2) of mineral surface area. Potentiometric titrations of suspensions of each mineral, with and without Cd(II) present, were also completed. Results from all three types of experiments were modeled using an extended constant- capacitance surface complexation model. The reactions [Formula: see text] [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto goethite, while [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto kaolinite. A combination of the first, second, and fourth of these reactions best fitted the data for Cd(II) adsorption onto illite. In each case the model fitted all experimental data well. The results suggest that adsorption onto the variable charge (SOH) sites on illite more closely resembles adsorption onto goethite than onto kaolinite.
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http://dx.doi.org/10.1016/s0021-9797(02)00031-0DOI Listing
January 2003

Cosorption of Zn(II) and 2-, 3-, or 4-aminopyridine by montmorillonite.

J Colloid Interface Sci 2005 Apr;284(2):400-7

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

Data from acid-base titrations at 25 degrees C of Zn(NO(3))(2) and 2-, 3-, or 4-aminopyridine in 10 mM KNO(3) as background electrolyte suggested that soluble complexes ZnL(2+) and Zn(OH)L(+) form, where L represents aminopyridine. Zinc-hydroxyaminopyridine complexes have not been reported previously. The cosorption of Zn(II) with each of the aminopyridines to K-saturated Wyoming (SWy-K) and Texas (STx-K), and Ca-enriched Texas (STx-Ca) montmorillonites was measured at 25 degrees C, with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as background electrolyte. Comparison with previous data for sorption of Zn(II) and the aminopyridines separately and surface complexation modeling of the cosorption data showed that under acid conditions competition between Zn(2+) and aminopyridinium ions for the permanent negatively charged sites of montmorillonite results in suppression of the uptake of each sorbate by the other, but only when a large excess of the competing sorbate is present. Under alkaline conditions the sorption of Zn(II) was not affected by the presence of even a large excess of aminopyridine, but the sorption of 4-aminopyridine in particular was slightly enhanced when a large excess of Zn(II) was present. The enhancement was attributed to the formation of metal-bridged ternary surface complexes at the variable-charge sites on the edges of the montmorillonite crystals.
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http://dx.doi.org/10.1016/j.jcis.2004.10.059DOI Listing
April 2005

Surface complexation modeling of the sorption of 2-, 3-, and 4-aminopyridine by montmorillonite.

J Colloid Interface Sci 2005 Apr;284(2):383-92

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The sorption of 2-, 3-, and 4-aminopyridine on K-saturated Wyoming (SWy-K) and Texas (STx-K) and Ca-enriched Texas (STx-Ca) montmorillonite was measured at 25 degrees C with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as the background electrolyte. The aminopyridines adsorbed to montmorillonite at low pH, but not at high pH. Extended constant capacitance surface complexation models (ECCMs) and attenuated total reflectance-FTIR data indicate that aminopyridines sorb to the silica-like faces by cation exchange, forming outer-sphere complexes between aminopyridinium ions and permanent negatively charged surface sites (X(-)). X-ray diffraction data and sorption kinetics suggest that sorption occurs not only at external X(-) sites but also at those in the interlayer spaces. Differences in the sorption behaviors of 2-, 3-, and 4-aminopyridine result from differences in their pK(a)s. The extent of sorption of aminopyridines by the montmorillonite samples (SWy-K>STx-K>STx-Ca) results from the higher cation-exchange capacity of SWy-K, and from the fact that Ca(2+) is much more effective than K(+) in competing with protonated aminopyridines for the X(-) sites.
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http://dx.doi.org/10.1016/j.jcis.2004.10.027DOI Listing
April 2005

The effect of aspartic acid on the binding of transition metals to kaolinite.

J Colloid Interface Sci 2004 May;273(1):6-13

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The effect of aspartic acid on the adsorption of Pb(II), Cu(II), Zn(II), Co(II), and Mn(II) on kaolinite at 25 degrees C in the presence of 5 mM KNO3 was investigated by means of potentiometric titrations and adsorption measurements over a range of pH and concentration. Data were modeled by extended constant capacitance models. Aspartic acid slightly enhanced the adsorption of Pb(II), Zn(II), and Co(II) at low pH, but inhibited the adsorption of all the metal ions at higher pH. Adsorption of Cu(II) and Co(II) was inhibited strongly. Because aspartic acid is adsorbed only weakly by kaolinite, inhibition of metal ion adsorption depends on the ability of aspartic acid to form complexes with the various metal ions together with the adsorption characteristics of these complexes. In particular suppression of adsorption at high pH arises from competition between surface sites and dissolved aspartate ions for the available metal ions. Cu(II) and Co(II) form complexes with aspartic acid more strongly than the other metals. As these complexes do not adsorb, Cu(II) and Co(II) suffer greater suppression from aspartic acid than the other metals. There was no evidence of adsorption of aspartic acid complexes to the permanently charged kaolinite faces.
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http://dx.doi.org/10.1016/j.jcis.2004.01.060DOI Listing
May 2004

Adsorption of aspartic acid on kaolinite.

J Colloid Interface Sci 2004 May;273(1):1-5

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The interaction of aspartic acid with kaolinite was studied by potentiometric titrations and by adsorption measurements both at constant aspartate concentration (but varying pH) and at a constant pH of 5.5. The temperature was 25 degrees C, and the ionic medium 5 mM KNO3. Aspartic acid dissociation constants estimated from titrations agreed with those from the literature. The adsorption of aspartic acid to kaolinite was weak and varied only slightly with pH; 10-18% of 100 microM aspartic acid adsorbed to kaolinite at 100 m(2)L(-1) between pH 3 and 10. Data from the titrations and adsorption experiments were fitted closely by an extended constant-capacitance surface complexation model, in which monodentate outer-sphere complexes formed between deprotonated aspartic acid molecules and protonated sites on the variable-charge edges of the kaolinite crystals. There appeared to be no adsorption to the permanently charged crystal faces.
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http://dx.doi.org/10.1016/j.jcis.2004.01.061DOI Listing
May 2004

Suitability of N,O-bis(trimethylsilyl)trifluoroacetamide and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide as derivatization reagents for the determination of the estrogens estrone and 17alpha-ethinylestradiol by gas chromatography-mass spectrometry.

J Chromatogr A 2004 Feb;1026(1-2):295-300

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Vic. 3552, Australia.

This paper describes apreviously unreported problem with the use of N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) to derivatise the natural hormone estrone (E1) and the synthetic estrogen 17alpha-ethinylestradiol (EE2). The resulting trimethylsilyl (TMS) and t-butyldimethylsilyl (TBS) derivatives of EE2 were partially converted to their respective El derivatives. Therefore, these reagents may not be suitable for simultaneous determination of estrogens in environmental samples, which raises questions about the reliability of results from some earlier studies.
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http://dx.doi.org/10.1016/j.chroma.2003.10.110DOI Listing
February 2004

Modeling the adsorption of Cd(II) onto kaolinite and Muloorina illite in the presence of citric acid.

J Colloid Interface Sci 2004 Feb;270(1):86-93

Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of cadmium onto kaolinite and Muloorina illite in the presence of citric acid has been measured as a function of pH and cadmium concentration at 25 degrees C. When citric acid is present in the systems cadmium adsorption is slightly enhanced below pH 5, but significantly suppressed between pH 5 and 8, for both substrates. At higher citric acid concentrations very little cadmium adsorbs onto kaolinite from pH 5 to 8. Above pH 8 adsorption of Cd(II) onto illite is enhanced in the presence of citric acid, especially at lower concentrations, but this does not occur for kaolinite. Adsorption and potentiometric titration data were fitted by simple extended constant-capacitance surface complexation models for the two substrates. Enhancement of adsorption at lower pH values was ascribed to the ternary reaction [X(-)--K(+)](0)+Cd(2+)+L(3-)+2H(+) right arrow over left arrow (0)+K(+) involving outer-sphere complexation with permanently charged X(-) sites on the "silica" faces of both clay minerals. The models suggested that suppression of adsorption in the intermediate pH range was due to the formation of a strong CdL(-) solution complex which adsorbed neither on the permanently charged sites nor on the surface hydroxyl groups at the edges of the clay crystals. At higher pH values the dominant solution complex, CdLOH(2-), apparently adsorbed as an outer-sphere complex at surface hydroxyl groups on illite, SOH+2Cd(2+)+L(3-) right arrow over left arrow [SOCd(+)--CdOHL(2-)](-)+2H(+), but not on kaolinite. This difference in behavior results from the presence of =FeOH groups on the illite surface which can form surface complexes with CdLOH(2-), while the =AlOH groups on the kaolinite surface cannot.
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http://dx.doi.org/10.1016/j.jcis.2003.09.009DOI Listing
February 2004

Modeling the adsorption of Cd(II) onto goethite in the presence of citric acid.

J Colloid Interface Sci 2004 Jan;269(1):37-45

Colloid and Environmental Chemistry Laboratory, La Trobe University, Bendigo, PO Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of cadmium onto goethite in the presence of citric acid was measured as a function of pH and cadmium concentration at 25 degrees C. Potentiometric titrations were also performed on the system. Cadmium adsorption onto goethite was enhanced above pH 4 in the presence of 50 microM, 100 microM and 1 mM citric acid. While there was little difference between the enhancements caused by 50 and 100 microM citric acid below pH 6, above pH 6 further enhancement is seen in the presence of 100 microM citric acid. When 1 mM citric acid was present, the enhancement of cadmium adsorption was greater below pH 6, with increased Cd(II) adsorption down to pH 3.5. However, above pH 6, 1 mM of citric acid caused slightly less enhancement than the lower citric acid concentrations. ATR-FTIR spectra of soluble and adsorbed citrate-cadmium species were measured as a function of pH. At pH 4.6 there was very little difference between the ternary Cd(II)-citric acid-goethite spectrum and the binary citric acid-goethite spectrum. However, spectra of the ternary system at pH 7.0 and 8.7 indicated the presence of additional surface species. Further analysis of the spectra suggested that these were metal-ligand outer-sphere complexes. Data from the adsorption experiments and potentiometric titrations of the ternary Cd(II)-citric acid-goethite system were fitted by an extended constant-capacitance surface complexation model. The spectroscopic data were used to inform the choice of surface species. Three reactions in addition to those for the binary Cd(II)-goethite and citric acid-goethite systems were required to describe all of the data. They were [formula in text], [formula in text], and [formula in text]. Neither the spectroscopy nor the modeling suggested the formation of a ternary inner-sphere complex or a surface precipitate under the conditions used in this study.
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http://dx.doi.org/10.1016/j.jcis.2003.08.041DOI Listing
January 2004

Modeling the adsorption of citric acid onto Muloorina illite and related clay minerals.

J Colloid Interface Sci 2003 Nov;267(1):49-59

Colloid and Environmental Chemistry Laboratory, La Trobe University, Bendigo, P.O. Box 199, Bendigo, Victoria 3552, Australia.

The adsorption of citric acid onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. The greatest adsorption was onto goethite and the least onto illite. Adsorption onto goethite was at a maximum below pH 5 and decreased as the pH was increased to pH 9. For kaolinite, maximum adsorption occurred between pH 4.5 and pH 7, decreasing below and above this pH region, while for illite maximum adsorption occurred between about pH 5 and pH 7, decreasing at both lower and higher pH. ATR-FTIR spectra of citrate adsorbed to goethite at pH 4.6, pH 7.0, and pH 8.8 were compared with those of citrate solutions between pH 3.5 and pH 9.1. While the spectra of adsorbed citrate resembled those of the fully deprotonated solution species, there were significant differences. In particular the C[bond]O symmetric stretching band of the adsorbed species at pH 4.6 and 7.0 changed shape and was shifted to higher wave number. Further spectral analysis suggested that citrate adsorbed as an inner-sphere complex at pH 4.6 and pH 7.0 with coordination to the surface most probably via one or more carboxyl groups. At pH 8.8 the intensity of the adsorbed bands was much smaller but their shape was similar to those from the deprotonated citrate solution species, suggesting outer-sphere adsorption. Insufficient citric acid adsorbed onto illite or kaolinite to provide spectroscopic information about the mode of adsorption onto these minerals. Data from adsorption experiments, and from potentiometric titrations of suspensions of the minerals in the presence of citric acid, were fitted by extended constant-capacitance surface complexation models. On the goethite surface a monodentate inner-sphere complex dominated adsorption below pH 7.9, with a bidentate outer-sphere complex required at higher pH values. On kaolinite, citric acid adsorption was modeled with a bidentate outer-sphere complex at low pH and a monodentate outer-sphere complex at higher pH. There is evidence of dissolution of kaolinite in the presence of citric acid. For illite two bidentate outer-sphere complexes provided a good fit to all data.
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http://dx.doi.org/10.1016/s0021-9797(03)00693-3DOI Listing
November 2003

Sorption of 17beta-estradiol onto selected soil minerals.

J Colloid Interface Sci 2003 Oct;266(1):33-9

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia.

Sorption of the endocrine-disrupting chemical 17beta-estradiol (E(2)) from aqueous solutions to goethite, an iron oxide, and the clay minerals kaolinite, illite, and montmorillonite (K and Ca forms) was measured at 25 degrees C. The clay minerals sorbed more E(2) than the oxide, with sorption capacity increasing in the order goethite
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http://dx.doi.org/10.1016/s0021-9797(03)00597-6DOI Listing
October 2003
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