Your search resulted in 27 documents. Displaying 25 entries per page.
Influence of aliphatic acids on spore germination of wood decay fungi
1984 - IRG/WP 2224
Influences of eight saturated fatty acids (C5-C10, C12 and C16) on spores of four isolates of wood decaying basidiomycetes (white rot fungi: Poria tenuis and Trametes hispida; brown rot fungus: Gloeophyllum trabeum [two isolates]) were observed in-vitro. Spore response after 24 hr on malt extract agar containing 10, 10² , or 10³ ppm of each fatty acid included: no effect on normal germination, delayed germination or restricted mycelial growth, vacuolation and degeneration of spore cytoplasm, or germination inhibition without loss of spore integrity. C7-C10 acids destroyed spores of all fungi at 10² ppm whereas spores remained 'intact' at 10³ ppm of the same acids. C12 destroyed spores of the brown rot isolates but not the white rot fungi, and C16 lacked effect on all fungi at all concentrations. C5 and C6 destroyed spores only at 10³ ppm.
E L Schmidt
Preliminary study of the fungicidal and structural variability in copper naphthenates and naphthenic acids
1996 - IRG/WP 96-30114
Copper naphthenates, an oil-borne wood preservative listed by the American Wood-Preservers' Association (AWPA), is manufactured by complexing copper(II) with naphthenic acids. Prior to AWPA listing as a wood preservative, field experiments showed that copper naphthenates generally had good stability and were active against wood-destroying organisms. Recently, however, there have been reports of some copper naphthenate-treated poles rapidly failing. One possible explanation for the varying effectiveness could be that the structure, and resulting biological activity, of the naphthenic acids used to make copper naphthenate may vary. To test this hypothesis several naphthenic acids and copper naphenates were obtained and their fungicidal activity against three wood-destroying fungi measured. In addition, the chemical structure of the naphthenic acids were examined by proton- and carbon- NMR. Different activities were observed, especially against a copper-tolerant fungus. Some apparent correlations were seen between the fungicidal activity and chemical structures for the few samples studied.
T Schultz, D D Nicholas, L L Ingram Jr, T H Fisher
Durability of larch (Larix spp.) wood against brown-rot fungi
1997 - IRG/WP 97-10228
Durability of the heartwood of Larix decidua, L. sibirica, L. gmelinii, L. gmelinii var japonica, L. gmelinii var olgensis and L. sibirica x decidua against brown rot fungi Coniophora puteana, Poria placenta and Gloeophyllum trabeum was tested according to EN 113 test method. Parallel samples were used to study the amount and composition of wood extractives. The sample trees originated from the research forest of Punkaharju Research Station. The average age of the trees was 60 years. In addition, from L. sibirica also trees at 25 and 102 years were used. Results show that the durability of larch is depending on species, age of the tree, the wood part (inner or outer heartwood) and fungus. The average durability of larch heartwood was equal to class 3 or 4 (moderately or slightly durable, according to the standard EN350:2) and comparable with the durability of pine heartwood (Pinus sylvestris L). However, the durability of L. gmelinii var olgensis and L. sibirica (102 years old) was on the higher level than that of the other studied species but the durability varied even within the same board. Also the durability of wood from L. sibirica grown in the Russian side (Siberia) was studied. It was equal to that of the trees grown in Finland. The average amount of resin acids of larch heartwood was only about 0.1% (dry weight). In contrast, the heartwood of scots pine may contain up to 4.0% of resin acids. Resin acids are found to inhibit the linear growth of certain fungi. Interestingly, the largest amounts of resin acids (0.3%) were found in the heartwood of L. gmelinii which also showed high durability. The concentration of water soluble extracts (mainly arabinogalactan) of larch heartwood was quite large, varying between 3.2 - 20.5%. The concentration of water soluble extracts in the heartwood increased along the age of the trees. Lowest level of extractives were found in Larix decidua which was also the least decay resistant species. The durability of wood in different targets and the role of different chemical compounds of larch heartwood on decay resistance needs to be clarified.
H Viitanen, L Paajanen, P Saranpää, P Viitaniemi
Addendum to Document No: IRG/WP/428
1977 - IRG/WP 437
A J Emery
End grain sealants for wood preservation studies
1985 - IRG/WP 3341
The results of tests with possible end grain sealants for wood preservation studies are reported. The epoxy resins used gave satisfactory performance on wet or dry Sitka spruce and have been used with success for diffusion treatment studies.
R J Murphy, N A Summers
An investigation into the stability of TBTO in LOSP-treated radiata pine
1987 - IRG/WP 3459
Nuclear magnetic resonance (NMR) spectroscopy and reverse phase paper chromatography were used to characterise the organotin compounds found in radiata pine treated with bis (tri-n-butyl) tin oxide (TBTO). Preliminary results indicate that the preservative is remarkably unstable in wood after light organic solvent preservative (LOSP) treatment. Significant decomposition of TBTO occurs in a matter of hours. White crystalline material observed on the surface of treated wood was identified as tributyltin acetate (TBTA). Other tributyltin esters, dibutyltin ethers, and butyltin chlorides were also identified.
K J Archer, R Meder
Effect of fatty acid removal on treatability of Douglas-fir
1993 - IRG/WP 93-40008
Treatment of Douglas-fir with chromated-copper-arsenate (CCA) poses a major challenge. Several hypotheses based on the anatomical aspects as well as chemical reactivity of the preservative formulations with cell wall constituents and deposits have been proposed. Techniques to prevent pit aspiration or slow fixation reactions have, however, not significantly improved treatment. The presence of high molecular weight fatty acids have been reported to be responsible for higher hydrophobicity in some wood species. These acids can react with Cu+2/Cr+3 ions to form insoluble metallic soaps, thereby immobilizing Cu/Cr and increasing wood hydrophobicity by a mechanism similar to that employed in paper sizing. The effect of fatty acids on treatability was explored by removing these components via several extraction methods. In general, extracted wood had higher gross solution absorptions and chemical retentions, but preservative penetration was largely unaffected. The results suggest that removal or disruption of fatty acids can improve treatability of Douglas-fir heartwood.
S Kumar, J J Morrell
The formation of organotin carboxylates in bis(tributyltin) oxide - treated Pinus sylvestris sapwood
1990 - IRG/WP 3618
Tributyltin compounds have been successfully used for many years as wood preservatives, although their chemical nature in timber have not been fully elucidated. This study by 119Sn and 13C NMR spectroscopy has shown that, on impregnation into Pinus sylvestris sapwood, bis(tributyltin) oxide, (Bu3Sn)2O, is rapidly converted to tributyltin carboxylates, Bu3SnOCO·R, via reaction with components of the wood resin. It is further suggested that the formation of these species is a prerequisite for the known disproportionation reaction which occurs in (Bu3Sn)2O - treated timber.
S J Blunden, R Hill
Solvent extraction of CCA-C from out-of-service wood
1998 - IRG/WP 98-50107
Elimination of CCA from decommissioned wood prior to disposal is a major environmental issue. One approach is to extract CCA from treated wood, then reuse the 'clean' (may contain CCA, but below hazardous level) wood materials for manufacturing wood-based composites. In the present paper, we focus on effective leaching processes, selection of leaching agents and optimum leaching process parameters (temperature, time and reagent concentrations). These factors are crucial in obtaining high strength 'environmentally clean used wood substrate' suitable in manufacturing boards. Some leaching agents selectively leach certain components of CCA. Different combinations and sequences of leaching were evaluated. All treatments leave significant amounts of some CCA components in the wood, although some combinations of solvents can extract about 90% of all CCA components in 4 hours at a temperature of 50°C. Sequential extraction using formic acid and oxalic acid was one especially effective combination. Solution temperature, concentration and leaching time affect CCA component removal in different ways, depending on the solvent and element extracted. It should be possible to optimize extraction by manipulating these variables.
K M F Kazi, P A Cooper
A preliminary comparison of GC, HPLC and ELISA analysis of resin acids in pulp mill effluents
1997 - IRG/WP 97-20120
Resin acids are naturally occurring diterpenoid carboxylic acids present in most Canadian softwoods. There are eight common resin acids that are classified into two groups; the abietanes and the pimaranes. During processing of wood products they can be released into the environment where they are of concern because of their acute toxicity toward fish and other aquatic life. Traditionally resin acids are analyzed by gas chromatography (GC) which requires extraction of analytes from a sample matrix, derivatization to increase analyte volatility and separation by solid phase extraction. This process is difficult, tedious and expensive but provides quantification of the individual resin acids with low detection limits. Recently a fast and simple high performance liquid chromatography (HPLC) method was developed to analyze dehydroabietic acid (DHA) directly from pulp mill effluents. Our laboratory has developed an enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies that was successfully used to directly quantify the abietanes in CTMP effluent.. We compared the three techniques by analysing effluent samples from the Quesnel River Pulp Mill at various stages of the pulping process. Preliminary results showed good agreement for DHA analysis between the HPLC and GC methods. Since it analyzed for all the abietanes, ELISA measured a greater proportion of the resin acids in the samples than the HPLC. The merits and disadvantages of each method will be further discussed.
A N Serreqi, K Stark, Xiumei Feng, J N Saddler, C Breuil
Influence of carboxylic acids on LEACHING of copper amine based preservatives
2005 - IRG/WP 05-30365
The importance of chromium free preservatives is increasing. Leaching of copper from wood preserved with such solutions is still higher compared to leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic acids (octanoic, 2-etilheksanoic, decanoic) were added to copper/amine/boron aqueous solutions. Experiment of leaching of copper from Norway spruce (Picea abies) was performed according to the modified standard procedure (EN 1250). Results presented in this paper showed, that carboxylic acids significantly improve copper fixation. The best one was determined at specimens impregnated with the preservative solutions consisting of copper, ethanolamine, boric acid and octanoic acid.
M Humar, P Kalan, F Pohleven
Animal blood protein as a component of new, non-toxic wood preservatives fixing organic active compounds in wood
2003 - IRG/WP 03-30312
Application of natural organic compounds and simple physico-chemical treatments in wood conservation has, as its objective, not only its protection against biological agents but, equally importantly, protection of natural environment by gradual abandonment of toxic constituents still applied commonly on a wide scale. The introduction into wood of new, non-toxic impregnation agents manufactured on the basis of animal proteins aims to create an effective protection against biological factors, primarily the reduction of the degree of leaching out of the impregnation agent from wood. Experiments were carried out on the effectiveness of mixtures of carboxyl acids with animal blood protein against Coniophora puteana fungus. The object of the performed investigations was sapwood of Scots pine (Pinus sylvestris L.) impregnated with mixtures of carboxyl acids and animal blood plasma. Directly after impregnation, wood was subjected to thermal treatment with the aim to denaturate proteins. Mycological investigations were carried out using an accelerated agar-block method according to procedures described in EN 113 and EN 84 standards. The objective of the performed studies was to assess the effectiveness of blood protein as a constituent reducing the process of washing out of preservatives from wood. A low weight loss of samples saturated with the formulation containing propionic and ethyl buthyl acids and animal protein applied in the form of SOLUTEINTM preparation was demonstrated. The degree of leaching of carboxyl acids as active constituents from wood saturated with tested mixtures was estimated applying a mycological test as well as on the basis of chemical analysis of aqueous extracts from the leaching process. The performed experiments showed good protection properties of protein, which reduced effectively the extent of leaching of the active substance from wood.
B Mazela, I Polus
Screening of fungal strains for wood extractive degradation
1998 - IRG/WP 98-10254
Fungal strains were screened for their ability to degrade apolar extractives in wood from scots pine. The degradation of total wood extractives by 91 different strains was monitored in stationary batch assays incubated for 6 weeks. The results obtained show that the ability of wood-inhabiting fungi to utilize wood extractives varied greatly, even for different isolates of the same species. Fungal pretreatment provided up to 70% total resin reduction. Outstanding strains included mainly white-rot fungi. Several sapstain strains were also efficient extractive degraders. Apolar extractives are well known for their inhibitory effect to fungal growth. However, our findings show that wood extractives can serve as carbon source for numerous wood-inhabiting fungi. Furthermore, these results indicate the potentials of wood-inhabiting fungi in biotechnological processes for pulp and paper manufacturing, ie., wood chip depitching and biodetoxification.
J Dorado, M J Martinez-Inigo, T A van Beek, F W Claassen, J B P A Wijnberg, R Sierra-Alvarez
Feeding stimulants to enhance bait acceptance by Formosan termites
1994 - IRG/WP 94-10055
Four nitrogenous compounds were found to increase feeding by Coptotermes formosanus Shiraki in the laboratory. Cardboard disks dipped in urea solutions were consumed significantly more than untreated cardboard disks. Cardboard dipped in 8% urea showed a significant change in weight due to termite feeding over other urea treated cardboards. Examination of 15 amino acids in no choice feeding tests indicated that three, L-lysine, L-proline, and L-isoleucine, were feeding stimulants to Coptotermes formosanus. A fast screening method for feeding stimulant detectian was developed and is discussed. Using this method on 18 amino acids showed that L-proline and L-lysine were the best feeding stimulants.
G Henderson, M Kirby, J Chen
Detoxification of salt impregnated wood by organic acids in a pulping process
1993 - IRG/WP 93-50012
The paper descibes a novel method to detoxify pine wood (Pinus silvestris L.) treated with CCB-, CCF- CC-, and Cu-HDO-type salt preservatives. In the process of biological detoxification organic acids produced by strains of Antrodia vaillantii and other brown rot fungi are used for the dissolution of the previously fixed inorganic compounds. These findings are the basis for applying an acid pulping process (FORMACELL) developed by Nimz and Schone (1992) at the BFH, Hamburg, to detoxify salt impregnated wood waste with a mixture of acetic and formic acid. First results achieved with wood chips from treated poles after approximately 20 years of service life show that the obtained pulp contains less than 100 ppm of Cr and Cu. The pulp properties were neither influenced by the Cr and Cu ions nor by the age of the poles. The extracted quantities of Cr and Cu remain with the lignin whereas the acids are evaporated and recycled in the pulping process.
I Stephan, H H Nimz, R D Peek
Copper based wood preservative - A new approach using fixation with resin acids of rosin
2000 - IRG/WP 00-30249
Copper soaps with carboxylic acid groups of resin acids of rosin were shown to be potential long-term wood preservatives. The principle involved is the attachment of copper to the network formed by the inorganic part of the preservative (rosin) through the -COOH groups. The mechanisms of fixation have been studied, and it has been shown that this association could be obtained : (1) by forming the salt (a mix of rosin and NaOH where CuSO4 is added), and then impregnate (with a vacuum/pressure system) the wood with this product dissolved in ethanol, or (2) by using a double impregnation system with water solutions of the mix rosin-NaOH first, and a CuSO4 solution second, the salt being then formed within the timber. The biocidal mechanisms are based on the realease of Cu2+ by hydrolysis of the -(COO - )2Cu2+ when very humid conditions occur, this being reversible when wood moisture content is decreasing. Treated wood mini-blocks have shown good performances when leached, and biological tests assessed the good durability of such treated and leached timber.
C Roussel, J P Haluk, A Pizzi, M-F Thévenon
The degradation of wood surfaces by dilute acids
1985 - IRG/WP 3326
Thin radial/longitudinal sections(~100 µ) of Corsican Pine (Pinus nigra) and Lime (Tilia vulgaris), were exposed to Sulphuric, Sulphurous, nitric, acetic, and formic acid at 40°C in the pH range 2-6. After about 3 months exposure to Sulphuric, nitric, acetic and formic acid at pH 2.0 Pine lost some 20-25% of its tensile strength. Losses in tensile strength due to sulphurous acid were greater being about 60-70%. Further prolonged exposure to sulphurous acid for 12 months led to some 90% tensile strength loss in Pine and 95% in Lime. Tensile strength losses also occurred at pH 2.5 and 3.0. For Pine strength losses of some 40% and 20% occurred at pH 2.5 and 3.0 after 12 months exposure. For Lime the losses were somewhat greater being about 70% at pH 2.5 and 50% at pH 3.0. For both species even greater losses in toughness occurred after this period of exposure in the pH range 2-3. Signficant but more erratic losses in toughness also occurred at pH 3.5. The strength losses noted above are over and above those resulting due to exposure of the controls to deionized water alone. During a similar time period exposure to deionized water led to losses in tensile strength for both species of some 15-20%. Losses in toughness were even greater being in the range 20-40%. Lime specimens tested wet showed a tendency to fail by inter-fibre shear in the middle lamella region. Scanning electron micrography also showed degradation of the middle lamella in Pine. It is believed that the degradational phenomena reported here are due to physico-chemical processes and that they may contribute to the degradation of paints and other finishes from wood surfaces.
P D Evans, W B Banks
The fixation of copper in Pinus sylvestris using the sodium salts of two polyhydroxycarboxylic acids
1992 - IRG/WP 92-3706
As part of the research concerned with the development of fixed, copper based preservatives, the salts of polyhydroxycarboxyIic acids, have been used in copper sequestration studies and fixation trials in Pinus sylvestris splinters. Selected compounds have been shown to be effective sequestrants at low concentrations allowing alkaline solutions to be formulated. Leaching trials following a 48 hour wet fixation period at 40°C showed that aximum copper fixation can be achieved from formulations within the pH 7 to pH 9.0 range, providing sequestrant concentrations are optimised.
M Bacon, J A Cornfield
Degradation of resin constituents in various wood species by the white rot fungus Bjerkandera sp. strain BOS55
1999 - IRG/WP 99-10301
In previous studies, the white-rot fungus Bjerkandera sp. strain BOS55 was shown to cause extensive degradation of lipophilic extractives (resin) in Scots pine wood. Further research was carried out in order to investigate the ability of Bjerkandera sp. for reducing resinous constituents in various softwood (Douglas fir, larch and spruce) and hardwood species (birch, beech and poplar). The greatest resin reduction occurred in beech (79% in two weeks). High levels of resin elimination were also observed in softwood species like spruce (36%) or Scots pine (35%), as well as in hardwood species like poplar (32%) or birch (24%). In contrast, Bjerkandera sp. only caused a negligible loss of resin components in Douglas fir wood chips. HPLC analysis of acetone extracts from control and fungal-treated samples showed a rapid elimination of triglycerides, diglycerides, free fatty acids and sterols. Toxic constituents in softwood species like resin acids were partially removed in Scots pine, spruce and larch (29-34% in two weeks).
J Dorado, T A Van Beek, F W Claassen, R Sierra-Alvarez
Water repellency and dimensional stabilIty of wodd treated with waterborne resin acids/TOR
2007 - IRG/WP 07-40364
Wood used in above ground applications such as decking undergoes undesired dimensional changes leading to the lumber warping, cupping, splitting, etc. This is a major concern to consumers but it can be reduced by treating lumber with a water repellent. The ability of resin acids, hydrophobic compounds naturally present in southern yellow pines, was examined as a possible water repellent. A waterborne resin acid or a commercial source of resin acids called tall oil rosin or TOR provided similar water repellency in laboratory tests to wax treatments, while minimal water repellency was observed with solventborne resin acids. Leaching partially reduced the water repellency of wood treated with TOR but not with a pure resin acid. Decking or laminated lumber treated with TOR and exposed outdoor above-ground had reduced moisture content, checking, cupping and mold growth than untreated boards. We previously found that southern pine sapwood has a wide natural variation in resin acid content, and untreated sapwood samples had assorted water repellency and decay resistance. The intrinsic water repellency and decay resistance of southern pine sapwood may be correlated to the amount of resin acids present.
T P Schultz, D D Nicholas, J Shi
Wood preservation by a mixed anhydride treatment: Using simple models of polymeric wood compounds
2008 - IRG/WP 08-30457
Treatment of wood by a mixed aceto/oleic (or other fatty acid residue) anhydride promoted as a safe and environment friendly wood preservation system has been examined quantitatively by liquid phase 13C NMR and solid phase MAS-DEC (proton decoupling) 13C NMR through all its different stages to determine which reactions occur with simple model compounds of the polymeric constituents of wood. The preparation of the mixed aceto/oleic anhydride under different conditions has been followed too. The anhydride forms but its percentage yield was found to be of the order of only 30%. The mix composed of unreacted acetic anhydride, the mixed aceto/oleic anhydride, and great proportions of free acetic acid and free oleic acid which is used for wood preservation yields acetylation of the lignin model compound (i) by reaction of the acetic anhydride with it and (ii) by reaction of the acetic part of the mixed anhydride. In this reaction the whole mixed anhydride is consumed and nothing of it is left. The oleic part of the mixed anhydride apparently is not able to form esters on lignin being far less reactive than the acetic part. Carbohydrates appears much less readily esterified, being polar enough to be repellent to the oleic residue, some acetylation occurring and some traces, and no more than traces, of carbohydrates oleic acid ester occurring too under some conditions. This system of treatment through a mixed anhydride boils down to being just an acetylation with acetic anhydride, mixed with some oleic acid as water repellent, both already known processes.
F Lyon, M-F Thevenon, A Pizzi, G Tondi, A Despres, J Gril, S Rigolet
Microwave-Assisted Organic Acids Extraction of Chromate Copper Arsenate (CCA)-Treated Southern Pine
2010 - IRG/WP 10-50267
The extraction effects of acid concentration, reaction time and temperature in a microwave reactor on recovery of CCA-treated wood were evaluated. Extraction of copper, chromium, and arsenic metals from chromated copper arsenate (CCA)-treated southern pine wood samples with two different organic acids (i.e., acetic acid and oxalic acid) was investigated using a microwave reactor. Oxalic acid was effective in removing 100% of the chromium and arsenic at 160ºC and 30 min. reaction time. Acetic acid could remove 98% of the copper and arsenic at the same condition. Oxalic acid significantly improved the extraction efficiency of arsenic and chromium when time was prolonged from 10min. to 30min. The HSAB (Pearson acid base concept) concept was applied to explain why oxalic acid removed more chromium and less copper compared with acetic acid. Acetic acid also showed an improved ability to remove arsenic and copper when the reaction temperature was increased from 90ºC to 160ºC.
Bin Yu, Chung Y Hse, T F Shupe
Above Ground Field Evaluation and GC-MS Analysis of Naturally Durable Wood Species
2012 - IRG/WP 12-10764
Nine wood species are being evaluated in above ground field studies in Mississippi and Wisconsin. Candidate naturally durable wood (NDW) species are being rated at yearly intervals for resistance to decay, cupping, and checking. Field ratings after 12 months exposure are presented. To date, Paulownia tomentosa (PAW) and southern yellow pine (SYP) are least durable and cedars are the most durable in above ground exposure. Wood samples are being taken from the deck-boards and subjected to chemical analysis using GC-MS. Fatty acids from NDW species were extracted, derivatized, and analyzed along with commercial fatty acid methyl ester (FAME) standards. With few exceptions, results indicate that FAMEs are more abundant in NDW species. However, preliminary bioassays found no inhibition of select wood decay fungi by FAMEs at naturally occurring concentrations.
G T Kirker, A B Blodgett, S T Lebow, C A Clausen
Short-term protection of palm wood against moulds and decay fungi by environment-friendly organic acids
2015 - IRG/WP 15-10843
Felled palm trunks are susceptible to fungi as long as their moisture content is above fibre saturation. During this period, it has to be protected against moulds and decay fungi. The study tested environmental-friendly organic acids for their protecting efficiency. Small samples of Date palm (Phoenix dactylifera) and Oil palm (Elaeis guineensis) wood were treated with weak organic acids and subsequently infected by moulds and wood-decay fungi. Short dipping of the samples in solutions of 5% acetic acid and propionic acid, respectively, protected all samples for two months from colonization by Aspergillus niger, Penicillium sp., Cladosporium sp., and by a natural infection. Boric acid (4%) used in practice for protection was ineffective. Decay tests with the white-rot fungus Pleurotus ostreatus, the brown-rot species Coniophora puteana and the soft-rot fungus Chaetomium globosum showed that both acids prevented most samples from fungal colonization and reduced decay considerably during two months.
M Bahmani, O Schmidt
Prevention of fungal damage of oil and date palm wood by organic acids
2017 - IRG/WP 17-10877
Felled palm trunks are susceptible to fungi as long as their moisture content is above fibre saturation. During this period, palm wood has to be protected against mould and rot fungi. Environmental-friendly organic acids are suitable. Small samples of oil palm (Elaeis guineensis) and date palm (Phoenix dactylifera) wood were treated with 1 to 10% solutions of acetic acid and propionic acid, respectively, and subsequently infected by moulds, blue-stain and wood-decay fungi. Short dipping of the samples in 2% solutions of both acids protected all samples for two months from colonization and discolouration by Aspergillus niger, Penicillium commune, Mucor sp., and a natural infection. A blue-stain fungus was inhibited by 5% solutions. Decay tests with the white-rot fungus Pleurotus ostreatus, the brown-rot species Coniophora puteana and the soft-rot fungus Chaetomium globosum showed that 5 and 10% solutions of both acids reduced degradation.
M Bahmani, O Schmidt