Methanolic Potassium Hydroxide Research Articles

Optimization of Base-Catalyzed Transesterification in Biodiesel Production from Refined Palm Oil via Circulation Process through Static Mixer Reactor

In this work, response surface methodology (RSM), with 5-level and 2-factor central composite design (CCD) was used to optimize the condition of base-catalyzed transesterification from refined palm oil. The two main parameters; methanol concentration and potassium hydroxide concentration, were varied to investigate the effect on the methyl ester purity. The result indicated that the KOH concentration was the most significant to produce methyl ester (the lowest p-values occurs in all response models). From excel solver, full quadratic model was obtained for predicting the response surface models. The suitable condition: 23.81 vol.% methanol and 11.80 wt.% KOH under temperature of 60°C and reaction time of 60 min, is the optimum condition.

Cинтез и антибактериальная активность производных 5-тиометилфуран-2-карбоновой кислоты

Синтезированы метиловые эфиры 5-(1Н-1,2,4-триазол-3-илсульфанилметил)фуран-2-карбоновых кислот, содержащие в положении 5 триазольного кольца алкильный или 2(4)-алкоксифенильный заместитель. Щелочным гидролизом эфиров получены соответствующие кислоты. Методом рентгеноструктурного анализа доказано, что осциллирующий атом водорода в триазольном кольце метилового эфира 5-[5-(2-этоксифенил)-1Н-1,2,4-триазол-3-илсульфанилметил]фуран-2-карбоновой кислоты локализован у N1 атома. Изучены антибактериальные свойства эфиров и кислот.

Novel μ2-oxo-bridged dinuclear aryltelluronic triorganotin(IV) esters: syntheses, structural characterizations, and in vitro cytotoxicity

Four new μ2-oxo-bridged dinuclear aryltelluronic triorganotin esters [ArTe(μ-O)(OH)(OSnR3)2]2 (Ar = n-propyl-Ph, R = Me: 1, R = Ph: 2; Ar = i-propyl-Ph, R = Me: 3, R = Ph: 4) were synthesized by reaction of μ2-oxo-bridged dinuclear aryltelluronic acids and the corresponding R3SnCl (R = Me, Ph) with potassium hydroxide in methanol. The complexes were characterized by X-ray crystallography, elemental analysis, FT-IR, and NMR (1H, 13C, 119Sn) spectroscopy. The structural analysis indicates that these complexes are isostructural and crystallized as Sn4Te2 molecules, in which the asymmetric four-membered Te2(μ2-O)2 units are situated in the center. The geometry of tellurium is described as a distorted octahedron and each tin is described as a distorted tetrahedron. Complex 2 has a 2-D network structure connected by intermolecular C–H⋯π interactions. Complexes 1–4 were tested for in vitro cytotoxicity against human lung cancer cells (A549) and human hepatocellular carcinoma cells (HepG2).

Determination of Optimum Reaction Temperature and Reaction Time for Biodiesel Yield from Coconut (Cocos nucifera) Oil

The determination of optimum reaction temperature and time for biodiesel yield from Coconut (Cocos nucifera) oil was studied. The oil was transesterified using potassium hydroxide (KOH) in methanol as catalyst to obtain the crude biodiesel. For the reaction time, the biodiesel production was carried out at 30 min, 45 min, 60 min, 75 min and 90 min while their temperature (60oC), oil to alcohol ratio (6:1) and catalyst concentration (0.65%) were kept constant. For the reaction temperature, the reaction was carried out at 45oC, 50oC, 55oC, 60oC and 65oC, while their reaction time (60 min), oil to alcohol ratio (6:1) and catalyst concentration (0.65%) were kept constant. The crude biodiesel were purified by washing with water severally to obtain the relatively pure biodiesel. They were dried using solar dryer for a period of four (4) days to obtain moisture-free pure biodiesel. They were subsequently analyzed for various parameters; Kinematic viscosity, acid value, free fatty acid (FFA), specific gravity, iodine value, ash value and flash point. The different Original Research Article International Research Journal of Pure & Applied Chemistry, 4(1): 108-117, 2014 109 variants gave results of the parameters analyzed comparable to International standards of biodiesel (ASTM) methods. The results of the study showed that for the reaction time, the optimum yield was obtained at 45 min giving a biodiesel yield (after purification) of 88% while for the reaction temperature, the optimum yield was obtained at 45oC with a biodiesel yield of 87.4%. General results obtained showed that the optimum yield of biodiesel obtainable from Coconut oil when transesterified using KOH/methanol is about 88%. Overall results indicate that Coconut oil can serve as a veritable feedstock for biodiesel production.

Synthesis, structure and supramolecular features of cobalt(III) and cobalt(II) complexes, [CoHxL](ClO4)y (x = y = 3, 2, 1.50, 1.45, 1 and 0 and x = 3, y = 2) of a triprotic imidazole containing Schiff base ligand. Effect of protonation state on supramolecular structure

Aerial reaction of cobalt(II) perchlorate with H3(1) {H3(1) is the tripodal ligand derived from the condensation of tris(2-aminoethyl)amine with three equivalents of 4-methyl-5-imidazolecarboxaldehyde} in acidic methanol results in isolation of both the orange [CoH3(1)](ClO4)2 (trace) and red [CoH3(1)](ClO4)3 (2 pseudopolymorphs). An analogous reaction in methanol gives [CoH2(1)](ClO4)2. Reaction of [CoH2(1)](ClO4)2 (generated in situ) with aqueous sodium hydroxide gives [CoH(1)](ClO4) (two pseudopolymorphs) and a trace amount of [CoH1.45(1)](ClO4)1.45. Reaction of [CoH3(1)](ClO4)3 with 1.5 equivalents of hydroxide gives [CoH1.5(1)](ClO4)1.5. Reaction of [CoH(1)](ClO4) with methanolic potassium hydroxide in acetonitrile gave [Co(1)] (two pseudopolymorphs). Complexes were characterized by EA and IR if available in sufficient amounts. All ten complexes were structurally characterized and their metrical parameters are consistent with a high spin cobalt(II) for [CoH3(1)](ClO4)2 and low spin cobalt(III) for all of the cobalt(III) complexes. [CoH3(1)](ClO4)2 and one polymorph of [CoH3(1)](ClO4)3 dimerize by hydrogen bonding through three perchlorate anions. [CoH2(1)](ClO4)2 and one of the pseudopolymorphs of [CoH(1)](ClO4) form intermolecular imidazole-H…imidazolate hydrogen bonds resulting in hetero and homochiral 1D zig-zag chains, respectively. [CoH1.5(1)](ClO4)1.5 forms a tetrahedral array of octahedral cobalt complexes held together by intermolecular imidazole-H…imidazolate hydrogen bonds. [CoH1.45(1)](ClO4)1.45 forms a hexameric structure with a large central channel containing solvent and perchlorate anions. [CoH(1)](ClO4) and both polymorphs of [Co(1)] form no intermolecular imidazole-H…imidazolate hydrogen bonds but do exhibit extensive hydrogen bond formation with water.

FAT SOLUBLE VITAMINS AND FATTY ACIDS COMPOSITION OF BLACK SEA CYSTOSEIRA BARBATA

Brown alga Cystoseira barbata is the most widely distributed seaweed in the Black Sea. There is limited information about fat soluble vitamins content and fatty acids composition of this specie from Bulgarian Black Sea coast. The aim of this study was to determine fat soluble vitamins, pigments, total lipid and fatty acid composition of Cystoseira barbata. Fat soluble vitamins (vitamin E and D), pigments (β-carotene and astaxanthin) and total cholesterol were analyzed simultaneously using HPLC/UV/FL system equipped with RP analytical column. Sample preparation procedure includes alkaline saponification, followed by liquid-liquid extraction. Brown seaweed Cystoseira barbata contained high amounts of α-tocopherol and β-carotene. Lipids were extracted by following the method of Bligh and Dyer. The residual lipid fraction was methylated using base-catalyzed transmethylation with methanolic potassium hydroxide. Fatty acid composition was analyzed by GC/MS. Cystoseira barbata was rich in linoleic (C18:2n6) and eicosopentaenoic acid (C20:5n3) although total lipid content was generally low. High levels of α-tocopherol correlate with high levels of polyunsaturated fatty acids. As an antioxidant α-tocopherol preserves tissue PUFA from oxidation.

Production of Biodiesel from Yellow Oleander (Thevetia peruvian) Oil and its Biodegradability

Thevetia peruviana (Yellow Oleander) seed oil was extracted with n-hexane in a soxhlet extractor. The ethanolysis and methanolysis of the oil were carried out with 50% of potassium hydroxide in ethanol and methanol respectively by weight of oil, as catalyst. The biodiesel was tested for biodegradability using E. coli. The percentage yield of the FAEE and FAME were 84.8% and 91.6% respectively. The biodegradability values of 81.4% and 86.2% were obtained for FAEE and FAME respectively after a period of 28 days. Other fuel quality parameters determined are the cetane index of 47.19 (FAEE) and 58.97 (FAME), flash point of <TEX>$198^{\circ}C$</TEX> (FAEE) and <TEX>$175^{\circ}C$</TEX> (FAME), kinematic viscosity at <TEX>$40^{\circ}C$</TEX> of 5.21 <TEX>$mm^2s^{-1}$</TEX> (FAEE) and 5.10 <TEX>$mm^2s^{-1}$</TEX>(FAME), pour point of <TEX>$4^{\circ}C$</TEX> (FAEE) and <TEX>$-2^{\circ}C$</TEX> (FAME) and a cloud point of <TEX>$6^{\circ}C$</TEX> (FAEE) and <TEX>$3^{\circ}C$</TEX> (FAME). Thus, Thevetia peruviana oil has a high potential for use in production of environmentally friendly biodiesel.

Robotized method for the quantification of fatty acids by gas–liquid chromatography

Analysis of fatty acid profile in fats and oils is conventionally performed by gas–liquid chromatography (GLC) as their fatty acid methyl ester (FAME) derivatives. Accurate quantification can be achieved by adding internal standard(s) prior to the derivatization step and calibration of the system using certified FAME mixture. GLC instruments equipped with online sample preparation units became recently commercially available and in theory can be used to improve laboratory productivity and safety. However, studies showing that this type of approach can be used to obtain reliable results are scarce. In the present study, we developed a method suitable for quantitative analysis of fatty acids in fats and oils by robotic preparation and online GLC analysis of FAME using methanolic potassium hydroxide as transmethylation reagent. The method has been validated on different fats and oils including milk fat, palm kernel, rapeseed and long‐chain polyunsaturated fatty acids containing oil samples. Method performance has been compared to the corresponding manual procedure and results show good repeatability [CV(r)&lt;5%] and good intermediate reproducibility [CV(iR)&lt;5%] in accordance with FDA guidelines. The results obtained show that transmethylation and GLC analysis of fats and oils can be robotized while remaining accurate and providing fatty acid data expressed as g of fatty acid per 100 g of sample. Compared to conventional methods, the volume of reagent and solvent is three times lower per sample analyzed with the robotized version which contributes to the reduction of waste and chemical risk exposure.

Development of a rapid, high-throughput method for quantification of zeaxanthin in Chinese wolfberry using HPLC–DAD

A rapid, high-throughput method was developed to evaluate zeaxanthin levels in Chinese wolfberry fruit, based on the official AOAC (970.64) method. The sample preparation was optimized from the AOAC method with supporting material added to disperse the sample thoroughly. An HPLC method was adopted to replace the time-consuming column separation and spectrophotometric method used previously. Dried Chinese wolfberry fruit was extracted and saponified, simultaneously, in a volumetric flask with a four-solvent blend of hexane:ethanol:acetone:toluene (10:6:7:7); and 40% methanolic potassium hydroxide in order to convert the extracted zeaxanthin dipalmitate to free zeaxanthin in a single step. The flask was placed in a 56°C water bath and shaken at 200rpm for 20min. A normal-phase HPLC method was developed on a silica gel column with an isocratic mobile phase of hexane and ethyl acetate (70:30, v:v). Zeaxanthin was determined to be the dominant carotenoid in Chinese wolfberry fruit. This method was found to be rapid, sensitive and cost-effective for quantitating zeaxanthin in wolfberries compared to the column separation and the spectrophotometric methods traditionally used.Using the developed method, a total of 30 Chinese wolfberry samples from different growers/locations of China were investigated as potential sources of zeaxanthin. The fruit produced in the Ningxia Hui autonomous region had the highest level of zeaxanthin at greater than 1500mg/kg. The zeaxanthin content was not positively correlated to the size of fruit; suggesting that the low cost, smaller fruits may be an economical source for zexanthin extraction.

Synthesis and Biological Activities of Some New 3,6-Disubstituted 1,2,4-Triazolo[3,4-b]1,3,4-thiadiazole Derivatives

A series of aromatic hydrazides 3a-j were prepared by refluxing esters 2a-j with hydrazine hydrate in methanol, which were prepared by the esterification of 1a-j. Acetohydrazides 3a-j upon treatment with carbon disulfide and methanolic potassium hydroxide yielded potassium dithiocarbazate salts 4a-j, which on refluxing with hydrazine hydrate yielded substituted 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones 5a-j. The target compounds 6a-j were synthesized by condensing furan-3-carboxylic acid in the presence of polyphosphoric acid under reflux. The structures of newly synthesized compounds were characterized by IR, 1 H NMR, 13 C NMR, elemental analysis and mass spectrometric studies. All the synthesized compounds were screened for their urease, acetylcholine esterase inhibition, antioxidant and alkaline phosphatase inhibition activity. Almost all of the compounds 6a-j showed good to excellent activities against urease and acetylcholine esterase more than the reference drugs. Compounds 6f and 6g were more potent scavenger of free radicals than the reference n-propyl gallate. Compound 6b and 6h showed excellent activities of alkaline phosphatase as compare to the reference KH2PO4.

Bio‐antifelting of wool based on mild methanolic potassium hydroxide pretreatment

Covalently bound lipids cover the wool surface and make enzymatic degradation of wool scales very difficult. In this paper, methanolic potassium hydroxide (MPH) pretreatment was used prior to enzymatic treatment of wool with protease, aiming at hydrolyzing the outmost lipids on the wool surface and promoting the subsequent proteolytic reaction. The efficacy of lipid removal from the fiber surface and the properties of the protease‐treated wool were evaluated. The results indicated that mild MPH pretreatment with 0.10 mol/L MPH for 10 min improved the wettability of the wool without adverse impacts on its mechanical properties. The wetting time and area shrinkage of the wool fabric reached 0.5 s and 5.6%, respectively, and the strength loss was within the acceptable range. Pretreatment with high concentrations of MPH for longer times led to significant damage to the wool fibers and caused heavy strength loss, without improving the antifelting properties after protease treatment. Thus, the combination of mild MPH and protease treatments endowed the wool with desirable properties in contrast to the treatment with protease alone.

Synthesis and Structural Characterization of Triorganotin(IV) Derivatives with 2,2′-Thiodiglycolic Acid and 3,3′-Thiodipropionic Acid

The synthesis and structural characterization of four novel triorganotin(IV) complexes, {(R3Sn)2[C2H4S(COO)2]} n (R = Me: 1), {(R3Sn)4[C2H4S(COO)2]2} n (R = nBu: 2), {(R3Sn)2[C4H8S(COO)2]} n (R = Me: 3; nBu: 4) were obtained by the reaction of 2,2′-thiodiglycolic acid, 3,3′-thiodipropionic acid and the corresponding R3SnCl (R = Me, nBu) with potassium hydroxide in methanol. All the complexes were characterized by elemental analysis, Fourier transform infrared and nuclear magnetic resonance (1H, 13C, 119Sn) spectroscopies, X-ray crystallography and thermogravimetric analyses. The crystal structures show that 1 has 2D network structure in which 2,2′-thiodiglycolic acid acts as a tetradentate ligand coordinating to the trimethyltin(IV) ions. Complexes 2, 3, and 4 are 3D metal-organic framework structures in which the deprotoned acids act as a tetradentate ligand afforded by four oxygen atoms.

Unusual Catalysts from Molasses: Synthesis, Properties and Application in Obtaining Biofuels from Algae

Acid catalysts were prepared by sulfonation of carbon materials obtained from the pyrolysis of sugar beet molasses, a cheap, viscous byproduct in the processing of sugar beets into sugar. Conditions for the pyrolysis of molasses (temperature and time) influenced catalyst performance; the best combination came from pyrolysis at low temperature (420 °C) for a relatively long time (8-15 h), which ensured better stability of the final material. The most effective molasses catalyst was highly active in the esterification of fatty acids with methanol (100 % yield after 3 h) and more active than common solid acidic catalysts in the transesterification of vegetable oils with 25-75 wt % of acid content (55-96 % yield after 8 h). A tandem process using a solid acid molasses catalyst and potassium hydroxide in methanol was developed to de-acidificate and transesterificate algal oils from Chlamydomonas reinhardtii, Nannochloropsis gaditana, and Phaeodactylum tricornutum, which contain high amounts of free fatty acids. The amount of catalyst required for the de-acidification step was influenced by the chemical composition of the algal oil, thus operational conditions were determined not only in relation to free fatty acids content in the oil, but according to the composition of the lipid extract of each algal species.

Synthesis, urease inhibition, antioxidant and antibacterial studies of some 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones and their 3,6-disubstituted 1,2,4-triazolo[3,4-b]1,3,4-thiadiazole derivatives

A new series of 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones, bearing various methoxybenzyl- and methoxyphenethyl groups, was synthesized by refluxing potassium hydrazinecarbodithioate salts in dilute aqueous solution of hydrazine hydrate. These salts were formed by the reaction of acid hydrazides and carbon disulfide in methanolic potassium hydroxide solution at 0-5 °C. 4-Amino-5-aryl-3H-1,2,4-triazole-3-thiones were condensed with different substituted aromatic acids to yield 3,6-disubstituted-1,2,4-triazolo[3,4-b]1,3,4-thiadiazoles. The structures of the synthesized compounds were characterized by infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), elemental analysis and mass spectrometric (MS) studies. All the synthesized compounds were screened for their urease inhibition, antioxidant and antibacterial activities. Some compounds showed excellent urease inhibition activity, more than the standard drug. Others exhibited potent antioxidant activity. All the compounds showed significant antibacterial activities as compared to the standard drug.

ChemInform Abstract: Oximes as Products in the Reactions of 5‐Substituted 2‐Nitrothiophenes with Arylacetonitriles.

It has been shown that reactions 5-substituted 2-nitrothiophenes with arylacetonitriles in the presence of potassium hydroxide in methanol lead to the formation of the new [2-(hydroxyimino)-5-R-3(2H)-thienylidene](aryl)acetonitriles. Under proposed reaction conditions, the formation of thieno[2,3-c]isoxazole was not the case. J. Heterocyclic Chem., (2011).

IMPLICATIONS OF METHOD CHOSEN FOR ANALYSIS OF FATTY ACIDS IN MEAT: A REVIEW

The influence of the beef Fatty Acid (FA) profile on human health, has become a recurring concern. For an analysis of the lipid composition of food, it is necessary that the complex lipids be quantified in a suitable form for subsequent analysis of their composition by gas chromatography. The choice of appropriate methods of lipid extraction and esterification of fatty acids, is important in preventing chemical changes from within occurring in these molecules and the forming of artifacts. Among the methods used for quantification of lipids, those that use a mixture of polar and nonpolar solvents separate the lipids in the sample of the non-lipid components. As these methods were carried at ambient temperature, they most suitable for further analysis of the FA profile. These methods were extracted lipids efficiently and did not alter their chemical constitution. The methods of derivation of fatty acids for esterification could be catalyzed by acids or bases. The method was chosen to convert the lipids in Fatty Acid Methyl Esters (FAME) and allow their analysis by gas chromatography, should not lead to incomplete conversion of lipids into their FAME or form artifacts. The reagents commonly used in the transesterification of triacylglycerols in meat samples were the hydroxides of sodium or potassium hydroxide in methanol. Transesterification with these reagents could be developed at room temperature in a short period of time. It becomes a reliable technique for the identification of isomers of fatty acids such as conjugated linoleic acid. No single method performs optimally in all situations. The researcher must know the nature of the sample and select the appropriate method.

Detection of polycyclic aromatic hydrocarbons in different types of processed foods

Polycyclic aromatic hydrocarbons (PCAHs), particularly those with a high molecular weight, have been classified as probable carcinogens to humans. The aim of the present study is to determine the levels of PCAHs in samples of meat, fish, chicken, fried potato, and toasted bread, which will be thermally processed using conventional and microwave ovens. Different samples will be collected and analyzed for five PCAHs including pyrene, benzo(a)anthracene, benzo(e)pyrene, benzoflouroanthene, and benzo(a)pyrene. The analytical method involves saponification with methanolic potassium hydroxide, extraction with cyclohexane, and determination by high-performance liquid chromatography. The obtained results showed that there is a variation in the detected PCAHs in different foodstuffs. Fried potato processed by conventional oven or microwave oven showed none of the selected studied PCAHs. It was found that, chicken showed higher content levels of total PCAHs than the meat and fish. Data are the highest mean concentrations of fluoranthene and benzo(a)pyrene but within low limit. The obtained results were compared with international permissible levels to avoid pollution, which may cause hazardous effects on individual and society.

Synthesis of high‐molecular weight poly(vinyl alcohol) by low‐temperature emulsifier‐free emulsion polymerization of vinyl acetate and saponification

AbstractHigh‐molecular weight (HMW) poly(vinyl alcohol) (PVA) was prepared via an emulsifier‐free emulsion polymerization of vinyl acetate (VAc) using a redox initiation system in low temperatures, and the subsequent saponification with potassium hydroxide in methanol. The effect of the polymerization conditions on the conversion, molecular weight, and branching degree was investigated. PVA with maximum viscosity‐average degree of polymerization (DP) of 8270 could be prepared by saponification of poly(vinyl acetate) (PVAc), with DP of 10,660 obtained at temperature of 10°C, monomer concentration of 30%, potassium persulfate molar ratio to monomer of 1/2000, agitation speed of 160 rpm. The conversion was above 90%. From the emulsifier‐free emulsion polymerization of VAc in low temperature, PVAc with HMW and high linearity was effectively prepared, which might be useful for the preparation of high‐strength and high‐modulus PVA fiber. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of Different Seed Solutions on the Morphology and Electrooptical Properties of ZnO Nanorods

The morphology and electrooptical properties of ZnO nanorods synthesized on monoethanolamine‐based seed layer and KOH‐based seed layer were compared. The seed solutions were prepared in monoethanolamine in 2‐methoxyethanol and potassium hydroxide in methanol, respectively. Zinc acetate dihydrate was as a common precursor in both solutions. The nanorod‐ZnOs were synthesized via the spin coating of two different seed solutions on silicon substrates followed by their hydrothermal growth. The scanning electron microscopy (SEM), X‐ray diffraction (XRD), photoluminescence (PL), and Raman studies revealed that the ZnO nanorods obtained from monoethanolamine‐based seed layer had fewer defects, better crystals, and better alignment than those realized via KOH‐based seed layer. However, the current‐voltage (I‐V) characteristics demonstrated better conductivity of the ZnO nanorods obtained via KOH‐based seed layer. The current measured in forward bias was 4 mA and 40 μA for ZnO‐nanorods grown on KOH‐based seed layer and monoethanolamine‐based with the turn on voltage of approximately 1.5 V and 2.5 V, respectively, showing the feasibility of using both structures in optoelectric devices.

Analysis of Methylmercury Concentration in the Blood of Koreans by Using Cold Vapor Atomic Fluorescence Spectrophotometry

BackgroundMethylmercury is an organic form of mercury that is highly toxic to humans. Here, we present and establish a novel method to detect methylmercury concentrations in the blood of Koreans.MethodsMethylmercury concentration was analyzed with an automated methylmercury analytic system (MERX, Brooks Rand Co., USA) using cold vapor atomic fluorescence spectrophotometry (CVAFS). A variety of biological materials were digested in methanolic potassium hydroxide solution. The analysis method was validated by examination of certified reference material (955c, National Institute of Standard and Technology, USA). We randomly selected 30 Korean adults (age 20 yr or older) to analyze total blood mercury and methylmercury concentrations.ResultsThe detection limit and methylmercury recovery rate using this method were 0.1 pg/L and, 99.19% (range: 89.33-104.89%), respectively. The mean blood concentration of methylmercury was 4.54±2.15 µg/L (N=30). The mean proportion of methylmercury to the total mercury concentration was 78.27% (range: 41.37-98.80%).ConclusionsThis study is the first report to analyze blood methylmercury concentration using CVAFS in Korea. We expect that this method will contribute to the evaluation of mercury exposure and the assessment of the toxicological impact of mercury in future studies.