Titration

pH is one of the key parameters that determines heavy metal mobility in soils, sediments and waste materials. In many respects leaching behaviour as reflected by the pH stat leaching tests provide a better means of assessing environmental impact than analysis of total elemental composition. This paper discusses the use of pH stat leaching tests as a tool to assess the potential mobilisation of trace metals from soils, sediments and waste materials. The possibilities of pH stat leaching tests are illustrated by means of different examples.

A systematic density functional theory study supported by extended X-ray absorption fine structure (EXAFS) and infrared spectroscopic data was conducted to elucidate how structure and vibrational spectra of aqueous desferrioxamine B (DFOB) metal complexes vary with the metal ion identity. Structural parameters derived from EXAFS analyses and trends in metal binding constants are well reproduced and validated by the applied computational model. Vibrational mode analysis guides determination and recognition of crucial structureand metal-sensitive infrared marker bands. The key marker bands, CO and CN stretching modes, dominate the infrared spectra in the 1400-1650 cm −1 region. The modes are sensitive to the stability and size of the metal core (first coordination shell) and indicative of its deformation from the octahedral symmetry. The results shed light on the fundamental structural and electronic factors that control metal binding by siderophores, and drive their potentially rich and largely unexplored interactions with trace metals.

Biosorption can be an efficient low-cost process to remove toxic heavy metals from wastewater. This study investigated the uptake of Pb 2+ by processed orange peels, a pectin-rich byproduct of the fruit juice industry. Potentiometric titrations showed a significantly higher negative surface charge of protonated peels compared to original peels, with acidic groups around pH 4, 6, and 10. FTIR spectra of peels were similar to those of pectin. The carboxylic group peak shifted from 1636 to 1645 cm −1 after Pb 2+ binding, indicated the involvement of carboxyl groups in Pb 2 binding. Depending on the particle size, equilibrium was achieved in 30 min to 2 h. The first-order model was inferior to second-or third-order models. The obtained rate constants were much higher for smaller particles, while the capacity was similar for all sizes. Low pH, increased ionic strength, or competing co-ions reduced Pb 2+ binding at low sorbent dosages, but at high sorbent dosages removal remained above 90%. The Pb 2+ uptake at 300 ppm was 2 mmol/g (40% of the dry weight). Due to high uptake, favorable kinetics and good stability, citrus peel biosorbents hold high promise for industrial applications.

Biosorption by cheaply and abundantly available materials such as citrus peels can be a cost efficient method for removing heavy metals from wastewater. To investigate the role pectin plays in metal binding by citrus peels, native orange peels, protonated peels, depectinated peels, and extracted pectic acid were compared. Kinetic experiments showed that equilibrium was achieved in 1 h. The 1st-order model was more effective in describing the kinetics than the 2nd-order model. Titrations showed two acidic sites with pK a values around 4 (carboxyl) and 10.5 (hydroxyl), respectively. The pH dependent surface charge was described well by a two-site model. Sorption isotherms were best modeled assuming a 1:2 binding stoichiometry, followed by the Langmuir and the Freundlich model. The binding capacity was highest for pectic acid (2.9 mequiv./g) followed by protonated peels and native peels, being lowest for depectinated peels (1.7 mequiv./g). This showed the importance of pectin in metal binding by citrus peels. However, even depectinated peels were still good sorbents which still provided carboxyl groups that were involved in metal binding. FTIR spectra confirmed the presence of carboxyl and hydroxyl groups in all materials and their involvement in metal binding.

The determination of the acid content of wine plays an important role in the area of oenology, because it the properties and quality of wine, especially the color and the flavor. Tartaric acid is the principal organic compound present in wines that typically ranges from 0.2 -1.0 %. This experiment aimed to apply the principles of standardization, determine the % tartaric acid content of wine sample and apply the concept of acid-base titration. Furthermore, this experiment seeks to find out the molar concentration of an unknown KHP solution.

The purpose of this experiment was to determine the experimental mass of acetylsalicylic acid (ASA) tablets. The 3 parts of this experiment were: (1) preparation of a standard 0.150 M solution of KHP, (2) standardization of a NaOH solution by titration of NaOH into the primary standard KHP, and (3) titration of the secondary standard NaOH into a solution of a dissolved aspirin tablet. We found the concentration of NaOH was 0.147 M. Using basic stoichiometry, we found the empirical mass of ASA in a tablet to be 337 mg. The percent yield on an average ASA tablet was therefore 104%. Neglecting sources of error, this indicates that the quantity of ASA in a tablet is 4% higher than advertised.

The elemental composition of superconductor oxides YBa2Cu308_x were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and complexometric titration. Samples were dissolved in dilute HCl. A sequential PU 7000 Philips inductively coupled plasma atomic emission spectrometer was used for the measurements. A comparison of the different atom and ion emission lines of yttrium, barium and copper was carried out. The effect of changes of forward radio frequency (RF) power coupled into the plasma on emission intensity of various spectral lines was studied. The RF power was changed from 0.8 to 1.2 kW. The changes in the net intensities (%) of the emission lines of Cu(1) at 324.754 nm, Cu(I1) at 224.7OOnm. Ba(I1) at 455.403, Ba(II) at 493.409nm, Y(I1) at 371.030nm and Y(II) at 360.073nm were calculated. The indicator 1-(2-Pyridylazo)-2-Naphthol (PAN) and different buffers were used for the complexometric titration of Cu, Y and Ba. No statistically significant differences were found between the results of ICP-AES and chemical methods of analysis.

The classic technique for sulfate analysis in an undergraduate quantitative analysis lab involves precipitation as the barium salt with barium chloride, collection of the precipitate by gravity filtration using ashless filter paper, and removal of the filter paper by charring over a Bunsen burner. The entire process is time-consuming, hazardous, and frequently yields poor results. Titrimetric methods are much faster, but a good indicator has not been found for sulfate titrations. However, because the relative concentrations of ions in solution change during a titration sequence, monitoring conductivity during the progress of a titration produces a signal which can be used to indicate the equivalence point. A conductometric titration protocol has been developed which is relatively rapid, inexpensive, and can produce results as accurate as the classic technique in an undergraduate laboratory.

Research Question: Which type of key ingredients of antacids; NaHCO3 , CaCO3 , or MgCO3 is the most efficient in treating pyrosis based on acid-base back titration with 20cm3 of 2.0M HCl and the volume of CO2 gas produced from water displacement method?

In this report a gravimetric micro-Winkler titration method for determination of dissolved oxygen concentration in water is presented. Mathematical model of the method taking into account all influence factors is derived and an uncertainty analysis is carried out to determine the uncertainty contributions of all influence factors. The method is highly accurate: the relative expanded uncertainties (k = 2) are around 1% in the case of small (9-10 g) water samples. The uncertainty analysis carried out in characterizing the uncertainty of the method is the most comprehensive published for a micro-Winkler method, resulting in experimentally obtained estimates for all uncertainty sources of practical significance (around 20 uncertainty sources altogether).

Purpose: No study has assessed the titration success of CPAP therapy in patients with obesity hypoventilation syndrome (OHS) and an apnea-hypopnea index (AHI) <30 event/h. This study aimed to assess the titration success of CPAP therapy under polysomnography and subsequent short-term adherence (1 month) in patients with OHS and an AHI <30 event/h.
Methods: Consecutive OHS patients with an AHI <30 events/h between 2010 and 2019 were included (n=54). All OHS patients were first started on CPAP during the therapeutic sleep-study. If the therapeutic-study showed that the SpO2 remained < 90% for 20% of the total sleep time, a second therapeutic study was arranged with bi-level PAP (BPAP). Thirty patients agreed to participate in the 1-month follow-up adherence study. We applied the American-Thoracic-Society criteria for PAP adherence.
Results: The mean age was 54.8±14.6 years, and the mean BMI was 45.9±12.2 kg/m2. Successful titration on CPAP was attained in 36 (66.7%) patients, and 18 (33.3%) required BPAP. Patients who failed the CPAP trial had a significantly higher PaCO2 and bicarbonate, a more restrictive respiratory pattern on spirometry,  and a significantly higher time with SpO2<90 % (mins) during sleep. The only independent correlate of CPAP-titration success on the multivariable regression analysis was the desaturation index (OR: 1.33 [1.033-1.712]). More than 80% of the participants were using CPAP therapy after one-month with no differences in adherence between the CPAP and BPAP groups.
Conclusions: The current results suggest that CPAP therapy could be an acceptable alternative therapy to BPAP in patients with OHS without severe OSA.

Redox equilibria are previously explained by the Nernst equation (Section 5), which could be applied in many electrochemical systems to estimate quantities, such as potentials and concentrations of redox species in solution. This section 6 is devoted to applications of the Nernst equation in electrochemical systems, including energy (consumption or generation), corrosion, redox titration, as well as study of solubility, precipitation, and complexation reactions.

En el presente informe se exponen los resultados de la práctica de laboratorio en la cual se valoró el ácido acético de una muestra de vinagre. Para ello fue necesario preparar una solución de hidróxido de sodio 0,15 M, la cual se estandarizó con biftalato de potasio, con la que se realizó tres ensayos de valoración a una muestra diluida de vinagre gastando un volumen promedio de 9,4 ml del NaOH, obteniendo una concentración calculada de 0,071 M del ácido acético. En la segunda parte, se realizó una valoración potenciométrica a otra muestra de la misma solución del vinagre, con la cual se calculó y se trazó la respectiva curva de titulación que se expone posteriormente.

The purpose of this experiment is to determine the total hardness of water at the university’s Chemistry Laboratory using a standardized titrant, ethylenediaminetetraacetic acid, by applying the principles of complexometric and displacement titrimetric analysis. Using five drops of Eriochrome Black T as the indicator, the molarity of EDTA was determined by titrating it with the standard CaCl2 solution using 99.0% pure CaCO3 as the primary standard. Then, a 100.0-mL water sample was obtained from the faucet in the laboratory sink and was titrated with EDTA solution to determine its total hardness. According to American Water Works Association (Hem, 1985), an ideal water should not contain more than 80 mg/L. However, in this experiment, an average of 188.95±3.53 mg CaCO3/L was calculated indicating the water is very hard. This implies that the water system in the laboratory should be treated to avoid further plumbing problems, but this does not necessarily implies that it imposes a health risk, it is could be only alarming if other heavy metals are present, thus, further tests should be done.

Water hardness can be defined as a measure of the amount of calcium and magnesium salts present in water. A titration technique, complex-formation titration, was used in this study. An indicator was added to a sample, that was tested, which turned red signifying that magnesium is present in the sample and blue indicating that calcium ions are present. The overall aim of this study is to improve adeptness with quantitative titrimetric determinations and to be familiar with a method for determination of total hardness of water and metal ions using (ethylenediamminetetraacetic acid) EDTA, a chelating agent. And also to determine the total hardness the tap water obtained from College of Arts and Sciences (CAS) building, University of the Philippines, Miagao, Iloilo City, which is predicted to be extremely high compared to commercial mineral water. As for the procedure, in the preparation of the EDTA solution, 2g of Na2H2Y·2H2O was added with 10mL MgCl·6H2O solution and diluted with 100mL distilled water in a 500mL volumetric flask. For the standardization and analysis, a 0.2g of 1° saturated CaCO3 was added with 50mL distilled water in a 250mL volumetric flask and added with 1:1 HCl, drop wise. Then it was diluted to the mark and mixed thoroughly. With 50mL CaCO3 solution, 5mL of NH¬4++NH4Cl buffer and 5 drops of EBT indicator was added and then titrated with EDTA until the endpoint. These were performed in triplicate to obtain three samples. It was found that the total hardness of the water sample obtained met with the hypothesized outcome in which a high amount of hardness was observed.

When two or more halides are determined in solution by precipitation titration with silver nitrate as the titrant, significant errors can occur at the first equivalence point as a result of coprecipitation. Errors of up to 33% were found for the first equivalence point for solutions containing mixtures of halides at micromolar levels. The addition of a flocculating agent to the solution reduced coprecipitation by increasing the rate of exchange between the precipitated silver halide and the halide ion remaining in solution. A logarithmic relationship was observed between the charge of the flocculating agent and the logarithmic concentration of the agent needed to minimise coprecipitation. Although flocculating agents reduced coprecipitation, they do not, however, completely eliminate equivalence point errors. Here a new method is presented which effectively eliminates the problem of coprecipitation during precipitation titrations for solutions containing two halides. In order to decrease the possibility of coprecipitation, we used selective complexation of the precipitation ion Ag in order to control the AgX solubility. For example, in the case of CF q 3 by acidification of the solution to a pH less than 6. The titration is then continued and the second equivalence point determined. Equivalence point errors were reduced to less than 1.5% with careful application of the method. ᮊ

Aim: This experiment is intended to experiment on and investigate the transition pH reactivity of acid-base indicators. Because an indicator is also a weak acid or a weak base it has acidic properties and tends to change its colour when the acidity of environment changes. As a result, generally all of the indicators have specific pH levels to provoke the colour change. So, in this experiment, it has been tried to observe the specific pH range of Methyl Orange, Alizarine Yellow, Phenolphtalein, Bromocresol Green and Bromothymol Blue indicators. Research Question: How does the effects of different indicators; Methyl Orange, Alizarine Yellow, Phenolphtalein, Bromocresol Green, Bromothymol Blue with different pH range on the neutralization titration of NH 3 in Burette and HCl in Erlenmeyer Flask occurs under constant pressure and in constant temperature? Hypothesis: As the indicators change, while the titration occurs, the colour of the indicator changes according to the pH level of the solution in the Erlenmeyer flask, thus showing different pH activity. Null Hypothesis: As the indicators change, there will be no colour change interval for different indicators, so all of them will change their colour in the same pH level. Independent Variable: Type of indicator (Methyl Orange, Alizarine Yellow, Phenolphtalein, Bromocresol Green, Bromothymol Blue) Dependent Variable: pH of the colour change interval of the indicator Constant Variables:

Dengue is a disease caused by infection with one of the four dengue virus serotypes . The virus is transmitted to humans by Aedes sp. mosquitoes. This enveloped virus contains a positive single-stranded RNA genome. Clinical manifestations of dengue can have a wide range of outcomes varying from a mild febrile illness to a life-threatening condition. New techniques have largely replaced the use of DENV isolation in disease diagnosis. However, virus isolation still serves as the gold standard for detection and serotyping of DENV and is common practice in research and reference laboratories where clinical isolates of the virus are characterized and sequenced, or used for a variety of research experiments. Isolation of DENV from clinical samples can be achieved in mammalian and mosquito cells or by inoculation of mosquitoes. The experimental methods presented here describe the most common procedures used for the isolation, serotyping, propagation, and quantification of DENV. Curr. Protoc. Microbiol. 27:15D.2.1-15D.2.24. C 2012 by John Wiley & Sons, Inc.

Univariate (zero-order), multivariate (first-order) and multiway (second-order) calibrations were assayed for the determination of vinegar acidity using a mechanized procedure based upon vibrational spectroscopy and the emerging multicommutation methodology. The second-order methodology relies on the use of a flow system based on multicommutation and binary sampling. The flow network comprises a set of threeway solenoid valves, computer-controlled to provide facilities to handle the sample and to generate a time-dependent pH gradient using two carrier solutions. The procedure is based on the volumetric fraction variation approach that maintains the same volume of sample solution and dynamically varies its pH. The analysis of second-order absorbance-pH matrices was performed using parallel factor analysis (PARAFAC). Results were compared with first-order absorbance data analyzed with linear calibration and partial least squares regression (PLS) and they were employed for a discussion of the relative advantages of the applied chemometric tools. As excellent accuracy is obtained without the need of any sample pre-treatment, the procedure can be fully mechanized (i.e., by means of an auto-sampler device).

Phosphoric acid anodizing solutions are routinely titrated to monitor their concentrations; however, after successive anodizations of aluminum metal, increasing amounts of dissolved aluminum interfere with the neutralization titration. The true concentration of phosphoric acid is determined by a correction factor based on the concentration of the dissolved aluminum, which is determined industrially by flame atomic absorption spectrometry. The academic determination of a correction factor for aluminum as well as copper can be designed as a traditional or a problem-based learning exercise.

Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l (1 was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l (1 ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid Á/base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2 Á/8% w v (1 of acetic acid with a relative standard deviation of 4.8% (5.0% w v (1 acetic acid, n 0/11) was obtained. Sample throughputs of 60 h (1 were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively. #

Background In a clinical setting of gene therapy, quantitative methods are required to determine recombinant viral titres and transgene mRNA expression, avoiding the use of reporter genes. Methods We describe procedures based on quantitative polymerase chain reaction (qPCR) designed to assess functional titres of murine leukaemia virus (MLV) vectors, determine proviral copy numbers in transduced cells, and estimate retroviral transgene expression in both target cell lines and mice with transduced chimeric haematopoiesis. Results Compared to EGFP titration, proviral DNA detection by qPCR was more accurate in assessing the number of infective particles in supernatants, such that average viral titres in terms of proviral copies per cell were twofold higher. Transgene mRNA expression was directly determined from the vectors used without the need for reporter assays. A new parameter, defined here as the 'transcription index' (TI), served to establish the association between transcribed transgenic mRNA and each proviral insertion. The TI represents the potential expression of every vector or insertion in each cell type, and is thus useful as a control parameter for monitoring preclinical or clinical protocols. Conclusions The practical use of qPCR is demonstrated as a valuable alternative to reporter genes for the assessment and surveillance of insertion numbers and transgene expression. In combination with protein expression, this approach should be capable of establishing safer therapeutic gene doses, avoiding the potential side effects of high transduction and expression levels.

An overview of the interaction between charged macromolecules in aqueous solution is presented.
The starting point is the dielectric continuum model and the Debye-H¨uckel equation.
The usefulness of the simple theory is emphasized in particular for biological macromolecules,
whose net charge or surface charge density often is low. With more highly charged macromolecules
or aggregates it may be necessary to go beyond the simple Debye-H¨uckel theory and
invoke the non-linear Poisson-Boltzmann equation or even to approach an exact solution using
Monte Carlo simulations or similar techniques. The latter approach becomes indispensable
when studying systems with divalent or multivalent (counter)-ions. The long range character of
the electrostatic interactions means that charged systems of varying geometry - spheres, planes,
cylinders... - often have many properties in common. Another consequence is that the detailed
charge distribution on a macromolecule is less important. Many biological macromolecules contain
titratable groups, which means that the net charge will vary as a consequence of solution
conditions. This gives an extra attractive contribution to the interaction between two macromolecules,
which might be particularly important close to their respective isoelectric points.
The treatment of flexible polyelectrolytes/polyampholytes requires some extra efforts in order
to handle the increasingly complex geometry. A theoretical consequence is that the number of
parameters - chain length, charge density, polydispersity etc - prohibits the presentation of a
simple unified picture. An additional experimental, and theoretical, difficulty in this context
is the slow approach towards equilibrium, in particular with high molecular weight polymers.
A few generic situations where polyelectrolytes can act both as stabilizers and coagulants can,
however, be demonstrated using simulation techniques.

Univariate (zero-order), multivariate (first-order) and multiway (second-order) calibrations were assayed for the determination of vinegar acidity using a mechanized procedure based upon vibrational spectroscopy and the emerging multicommutation methodology. The second-order methodology relies on the use of a flow system based on multicommutation and binary sampling. The flow network comprises a set of threeway solenoid valves, computer-controlled to provide facilities to handle the sample and to generate a time-dependent pH gradient using two carrier solutions. The procedure is based on the volumetric fraction variation approach that maintains the same volume of sample solution and dynamically varies its pH. The analysis of second-order absorbance-pH matrices was performed using parallel factor analysis (PARAFAC). Results were compared with first-order absorbance data analyzed with linear calibration and partial least squares regression (PLS) and they were employed for a discussion of the relative advantages of the applied chemometric tools. As excellent accuracy is obtained without the need of any sample pre-treatment, the procedure can be fully mechanized (i.e., by means of an auto-sampler device).

This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH 2 -, SO 3 H-or COOHfunctionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.

In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589 nm to quantify NaCl. A series of standard bread sample pellets containing various concentrations of NaCl (0.025-3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concentrations, which showed good linearity in the range of 0.025-3.5% NaCl and 0.01-1.4% Na concentrations with correlation coefficients (R 2 ) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69 ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique.

Polycation-sensitive membrane optodes based on the chromoionophore 2 ,7-dichlorofluorescein octadecylester (DCFOE) have previously been developed and used for determination of heparin via a titrimetric method. In this study, it is shown that some other important polyanions such as PPS (pentosan polysulfate), DNA, xanthan, Na-alginate, and carrageenan (food additive) can also be readily determined by using DCFOE-based microtiter plate-format optodes (MPOs) and polycationic titrants that bind these polyanionic species. The optical sensors are prepared with poly(vinyl chloride) (PVC), polyurethane (PU), bis(2-ethylhexyl)sebacate (DOS), and 2 ,7-dichlorofluorescein octadecylester (DCFOE) and exhibit reproducible and sensitive absorbance changes in response to the varying polycationic titrant concentrations. Three different polycations; protamine, poly-l-lysine and poly-l-arginine, are employed as titrants. The method has a detection limit of 1 g mL −1 , and a dynamic range of 1-40 g mL −1. After the quantitative determinations are successfully demonstrated in buffered solutions, similar titrations are also performed in real samples. The method is validated by recovery studies in these samples. The average polyanion recoveries were quantitative [99.7(±1.3) % for pastry cream with vanillin (protamine titrant); 100.4 (±3.3) % for pastry gel with strawberry(PLA titrant), and 102.9(±2.0) % for pastry gel with strawberry (PLL titrant)].

Les équilibres redox sont expliqués précédemment par l'équation de Nernst, qui pourrait être appliquée dans de nombreux systèmes électrochimiques pour estimer ses quantités, telles que les potentiels et concentrations des espèces redox en solution. Cette section est consacrée aux applications de l'équation de Nernst dans les systèmes électrochimiques, y compris les cellules énergétiques (consommation ou génération), corrosion, titrages redox, ainsi que l'étude des réactions de solubilité, précipitation et complexation.

A sequential injection analysis (SIA) titration method has been developed for acid-base titrations. Strong and weak acids in different concentration ranges have been titrated with a strong base. The method is based on sequential aspiration of an acidic sample zone and only one zone of the base into a carrier stream of distilled water. On their way to the detector, the sample and the reagent zones are partially mixed due to the dispersion and thereby the base is partially neutralised by the acid. The base zone contains the indicator. An LED-spectrophotometer is used as detector. It senses the colour of the unneutralised base and the signal is recorded as a typical SIA peak. The peak area of the unreacted base was found to be proportional to the logarithm of the acid concentration. Calibration curves with good linearity were obtained for a strong acid in the concentration ranges of 10 − 4 -10 − 2 and 0.1 -3 M. Automatic sample dilution was implemented when sulphuric acid at concentration of 6 -13 M was titrated. For a weak acid, i.e. acetic acid, a linear calibration curve was obtained in the range of 3 × 10 − 4 -8× 10 − 2 M. By changing the volumes of the injected sample and the reagent, different acids as well as different concentration ranges of the acids can be titrated without any other adjustments in the SIA manifold or the titration protocol.

pH is one of the key parameters that determines heavy metal mobility in soils, sediments and waste materials. In many respects leaching behaviour as reflected by the pH(stat) leaching tests provide a better means of assessing environmental impact than analysis of total elemental composition. This paper discusses the use of pH(stat) leaching tests as a tool to assess the potential mobilisation of trace metals from soils, sediments and waste materials. The possibilities of pH(stat) leaching tests are illustrated by means of different examples. The mathematical fitting of metal leaching behaviour from soils and sediments enabled a distinction between 5 groups of elements with a different leaching behaviour, which could be related to &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;pools&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; with different reactivity. Contrary to single and sequential extractions, where pH is difficult to control, the reactivity and mobility of metals at a user-defined pH can be investigated. Moreover, the potential buffering capacity of the sample and its sensitivity to pH changes as a result of external stresses (e.g. soil acidification, liming) can be estimated. A multidisciplinary approach combining mineralogical analysis (X-ray diffraction) with chemical analysis, pH(stat) leaching tests and geochemical modelling (MINTEQA2) can provide information on the solid-phase speciation and reactivity of heavy metals in soils, sediments and waste materials. Besides the influence of pH on heavy metal leaching behaviour, additional information on heavy metal leachability and retention by the solid matrix was obtained from the kinetics of metal release during a pH(stat) test.

Tujuan yang ingin dicapai dalam penelitian ini adalah untuk menghasilkan alat titrasi sederhana yang mampu mengukur kadar vitamin C secara otomatis untuk mengurangi tingkat kesalahan pengukuran kadar vitamin C pada larutan. Metode yang digunakan untuk mengukur kadar vitamin C adalah metode titrasi asam basa yaitu larutan vitamin C yang bersifat asam dititrasi oleh larutan NaOH yang bersifat basa, dimana jumlah asam pada larutan setara dengan jumlah basa. Penelitian ini mengambil dua puluh sampel larutan vitamin C yang dilarutkan dengan 100 ml aquadest. Data dikumpulkan pada bulan April 2009, data yang diperoleh kemudian dianalisis dan hasilnya dibandingkan dengan hasil pengukuran kadar Vitamin C pada alat spektrofotometer untuk menentukan ketelitian pada alat ukur kadar vitamin C dengan menggunakan metode titrasi asam basa.Dari hasil pegujian terhadap alat ukur kadar  vitamin C baik pengontrol mikrokontroller AT89S51, maupun liquid cristal display (LCD) dapat disimpulkan bahwa dengan menggunakan alat kadar vitamin C metode titrasi asam basa dapat mengukur kadar vitamin C sesuai dengan hasil perbandingan nilai kadar vitamin C pada alat spektrofotometer. Pengukuran kadar vitamin C dengan menggunakan metode titrasi asam basa menunjukkan nilai kesalahan relatif sebesar 1,4601%.

A solid-contact Ca 2þ -selective electrode was used to study speciation of calcium in black liquor. During extended time of operation the standard potential was found to change, but the sensitivity of the electrode, and the selectivity coefficients remained unchanged. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) measurements showed sodium sorption to the electrode membrane during the measurement in black liquor. Linearization of the complexometric titration curves were used to determine the concentrations of Ca 2þ , CaOH þ as well as weak and strong calcium complexes. With inductively coupled plasma optical emission spectrometry (ICP-OES), similar total calcium concentrations were obtained as by the EDTA titration.

Conditions for eliminating systematic errors and minimizing random errors in the determination of water in methanol and α-alumina using Karl Fisher reagent with visual end-point detection are studied. The concentration dependence of the relative standard deviation of the determination of water by the Karl Fisher method is found to be linear in RSD–1/c coordinates. To exclude the effect of moisture contained in the titration flask, it is suggested to bind water with a titrant in the presence of a small amount of methanol. The methanol effect (that is, the dependence of the titration results on the water : methanol ratio and the total amount of the titrated water–methanol mixture) is shown to be eliminated in the presence of the products of water interaction with Karl Fisher reagent that form on the water binding stage. It is found that the use of a background dye, methylene blue, eliminates significant systematic errors in the determination of water by the Karl Fisher method,
particularly, at low concentrations. It is noted that the visual detection of the titration end-point has some advantages over the automated electrometric versions of the method; in particular, it is characterized by a better reproducibility of the determination of low concentrations of water.

Fox River water was supersaturated with respect to calcite; natural organic matter (NOM) might play a key role in this phenomenon. Fox River NOM (FRNOM) adsorption on the calcite surface is probably an important mechanism to explain this condition. Fox River water contained moderate ultraviolet absorbance (UVA) of NOM (0.19 1/cm), high concentration of calcium (70 mg/L), suspended solids with relatively high specific surface area (SSA) (6.9 m2/g), and moderate pH value (8.4) based on historical data. To test whether the phenomenon was caused by NOM adsorption, a series of experiments was conducted to explore the interaction between NOM and calcite in conditions similar to those of the Fox River. Suwannee River NOM (SRNOM) and Nordic Reservoir NOM (NRNOM) were used as surrogate NOM. The results show that SRNOM inhibited calcite dissolution significantly after 10 min based on measuring of the decrease in the free calcium concentration. The decrease in the free calcium was not solely due to formation of NOM-calcium complexes, because these complexes made up only about 3% of the total free calcium concentration. Therefore, NOM adsorption onto calcite was probably largely responsible for the inhibited calcite activity. Experimental results also showed that NOM adsorption increased with increasing NOM concentration in the range from 2 to 14 mg NOM/L, which is a common range for river water. Higher charge density also seems to promote sorption onto calcite; relative to NRNOM, SRNOM has a higher charge density and SRNOM has a higher affinity for calcite. Other factors that promoted NOM adsorption onto calcite included higher concentration of calcium and larger SSA of calcite seed. Based on water quality characteristics, the Fox River provides a suitable environment for NOM adsorption on calcite, and it seems likely that Fox River NOM (FRNOM) adsorption on calcite can inhibit calcite precipitation. This understanding of interaction between NOM and calcite could be used by WTPs along the Fox River for better optimization and improvement in treatment and operation

Virgin olive oil quality is assessed by chemical as well as sensory analysis. Two of the most important parameters that define the quality of virgin olive oils are the free acidity and the peroxide index. These chemical parameters are usually determined by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to support the quality grade assessment of virgin olive oil is presented. The system is battery operated and characterized by small dimensions, light weight and quick measurement response (about 30 s). The working principle is based on the measurement of the electrical conductance of an emulsion between a chemical reagent and the olive oil sample. Two different chemical reagents have been investigated: (1) a hydro-alcoholic solution (HAS), made of 60% ethanol and 40% distilled water; (2) 100% distilled water (DW). Tests have been carried out on a set of 40 olive oil samples. The results have shown how,...

The preparation of well-defined organo-mineral assemblies under controlled conditions is required to improve our understanding of the formation and surface reactivity of micrometric aggregates, ubiquitous in soils and continental aquatic media. We aim at investigating the building of organo-mineral assemblies with a specific focus on the assembly mode and its consequence on the final properties of the micrometric aggregates. In this work, the preparation and detailed characterization of clay-size aggregates composed of a clay mineral (illite), organic polymer (Dextran polysaccharide) and iron (hydr)oxide are reported, with a focus on the structural organization of the generated aggregates. A step-by-step strategy was developed, and three sets of clay-size composites were prepared with illite particles as a starting material. In two first steps, two distinct sets of two-component composites were obtained according to different procedures. Illite-iron (hydr)oxide composites were obtained by alkaline hydrolysis of iron in the presence of illite particles, and illite-Dextran aggregates were obtained through the addition of Dextran polysaccharide to an illite suspension. In a third step, three-component micro-aggregates were obtained by subsequent addition of Dextran to suspensions containing the formed illite-iron (hydr)oxide composite. The so-prepared 2-and 3-component aggregates were investigated by electrophoresis, electron microscopy, X-ray absorption and FTIR spectroscopies. For materials containing Dextran, electrophoretic mobility measurements evidenced variations of surface charge, combined with an increase of aggregate size highlighted by dynamic light scattering. Electron microscopy and EXAFS at iron K-edge evidenced the precipitation of nanoparticles of iron (hydr)oxide onto clay mineral surfaces. FTIR data in transmission and diffuse reflectance modes supported not only the adsorption of Dextran but also the preferential localization of Dextran at the external surfaces of the aggregates. All in all, data collected on the two-and three-component materials demonstrated that the presence of iron (hydr)oxide nanoparticles on the surface of illite strongly modified the organization of organic and mineral constituents.

The pK a-cooperative aims to provide a forum for experimental and theoretical researchers interested in protein pK a values and protein electrostatics in general. The first round of the pK acooperative, which challenged computational labs to carry out blind predictions against pK a s experimentally determined in the laboratory of Bertrand Garcia-Moreno, was completed and results discussed at the Telluride meeting (July 6-10, 2009). This paper serves as an introduction to the reports submitted by the blind prediction participants that will be published in a special issue of PROTEINS: Structure, Function and Bioinformatics. Here we briefly outline existing approaches for pK a calculations, emphasizing methods that were used by the participants in calculating the blind pK a values in the first round of the cooperative. We then point out some of the difficulties encountered by the participating groups in making their blind predictions, and finally try to provide some insights for future developments aimed at improving the accuracy of pK a calculations. Keywords pKa; protein electrostatics; pH dependent properties of proteins; predicting pKa values in proteins STATEMENT OF PURPOSE OF THE pK a-COOPERATIVE Computational and experimental study of acid-base equilibria in proteins has reached a point where further progress in increasing the reliability of predicting pK a 's will require the development of new approaches that better describe the underlying physics regulating the system's structure and dynamics as well as any pH-dependent phenomena 1. Such improvements may be based on entirely novel algorithms or on combining the strongest components of existing approaches. To carry out the latter, an initial step will be the detailed analysis of the strengths and weaknesses of existing approaches. Toward that end participants in a workshop on protein electrostatics, organized by Marilyn Gunner and

This report describes a fast, reproducible, inexpensive and convenient assay system for virus titration in the 96-well format. The micromethod substantially increases assay throughput and improves the data reproducibility. A highly simplified variant of virus quantification is based on immunohistochemical detection of virus amplification foci obtained without use of agarose or semisolid overlays. It can be incorporated into several types of routine virological assays successfully replacing the laborious and time-consuming conventional methods based on plaque formation under semisolid overlays. The method does not depend on the development of CPE and can be accommodated to assay viruses with substantial differences in growth properties. The use of enhanced immunohistochemical detection enabled a five-to six-fold reduction of the total assay time. The micromethod was specifically developed to take advantage of multichannel pipettor use to simplify handling of a large number of samples. The method performs well with an inexpensive low-power binocular, thus offering a routine assay system usable outside of specialized laboratory setting, such as for testing of clinical or field samples. When used in focus reduction-neutralization tests (FRNT), the method accommodates very small volumes of immune serum, which is often a decisive factor in experiments involving small rodent models.