Determination Of Free Acidity Research Articles

High frequency of fraud in honey without sanitary inspection illegally sold in São Paulo State

The aim of this study was to analyze honey from São Paulo State according to its physical and chemical properties. Determination of free acidity, moisture, hydroxymethylfurfural, Lund test, diastase test, and Fiehe reaction were performed in 73 samples (32 illegal honey, without sanitary inspection, and 41 legal honey, with sanitary inspection). An ANOVA test was applied to evaluate differences in the samples. Three samples had humidity greater than 20%, and one sample had a positive profile in the qualitative analysis of HMF (Fiehe) and quantitative analysis above 60 mg/kg. A total of 21 (65%) illegal honeys had at least one parameter outside the legislation. The irregularities presented were in the acidity, followed by the increase of HMF, negative Lund, high acidity, and high moisture. Significant differences were observed when comparing illegal and legal honey for acidity and hydroxymethylfurfural analysis (p < 0.05). The Fiehe test was positive in 2.44% of legal honeys and 64.52% of illegal honeys. No legal honey was negative for the Lund test, and 22.58% of illegal honeys had a negative profile. The results showed that illegal honey is not suitable for consumption, being outside the standard of identity and quality determined by the Codex Alimentarius Commission and the legislation.

A remote conductometric titration method for simultaneous determination of uranium and nitric acid concentrations at elevated temperatures

The determination of free acidity and uranium in a radioactive uranyl nitrate solution inside a hot cell has to be done remotely. It generally involves the addition of complexing agents or the application of sophisticated analytical methods and modelling. To make the analyses uncomplicated, a simple acid–base conductometric titration method was developed to determine the free acidity and the uranium concentration simultaneously. Uranyl nitrate solutions containing nitric acid from 0.02 to 0.83 mmol and uranium from 0.32 to 15.90 mg per aliquot were determined by this method. The precision and accuracy of the method were found to be within ± 5%. For the titrations carried out at higher temperatures, the bias was found to be within ± 10%.

Design and in-house validation of a portable system for the determination of free acidity in virgin olive oil

Nutritional and healthy values are well known properties of virgin olive oil (VOO). The product quality, in terms of belonging to a specific quality grade (extra virgin, virgin, lampante), is defined by a set of chemical-physical and sensory measurements. According to the official regulation of the European Union (EU Reg. 1348/2013) the free acidity is the first parameter that has to be determined by analysts; it gives information about the quality of the olives used to produce the VOO as well as the hydrolytic state of VOO just produced and stored. The official procedure is based on an acid-base titration that needs to be carried out in a chemical laboratory.In this paper a portable battery-operated electronic system to measure olive oil free acidity is presented: the system can be used for quick “in situ” tests in a production environment (olive oil mills or packaging centers) by people without particular training. The working principle of the system is based on the creation of an emulsion between oil and a hydroalcoholic solution: the free acidity is estimated on the value of the emulsion electrical conductance.The proposed system has been calibrated and in-house validated showing good results in terms of limit of detection and quantification, precision and accuracy. Moreover, a good correlation (R2adj = 0.97) with free acidity data obtained applying the official method on 30 olive oil samples belonging to different commercial categories (extra virgin, virgin and lampante olive oil) has been evidenced.

A novel electroanalytical approach based on the use of a room temperature ionic liquid for the determination of olive oil acidity

In this paper, a novel voltammetric/amperometric approach for the direct determination of free acidity (FFA, expressed as mass percentage of free oleic acid) in olive oil samples is presented. The method is based on the reduction processes occurring at a platinum microdisk electrode involving the free fatty acids present in the matrices. To overcome problems related to the low conductivity of the samples investigated, olive oils were mixed with suitable amounts of the room temperature ionic liquid (RTIL), tri-hexyl(tetradecyl)phosphonium bis (trifluoromethylsulfonyl) imide ([P14,6,6,6]+[NTf2]−), which acted as a supporting electrolyte. Conditions for a reliable quantification of the acids were preliminarily investigated by performing voltammetric and chronoamperometric measurements in RTIL solutions containing oleic acid at different concentrations. Oleic acid (OA) was chosen as a model compound as it is the main component of the FFA content in olive oils. In order to establish the effect of oxygen on the electroanalytical responses, the reduction process of OA was investigated under both deoxygenated and oxygenated conditions. It was found that, in both situations, the current arising from the electrode process of OA depended linearly on the OA concentration over a wide range varying from 0.1% to 8% OA (w/w). This range includes FFA values which can be found on all categories of commercially available oil samples, including extra-virgin, virgin and lampante oils. Voltammetric and chronoamperometric experiments were also performed in oil/RTIL samples artificially acidified (extra-virgin olive oils with known addition of oleic acid) and in natural olive oils from some commercial categories. The results obtained indicated that the electrochemical procedure developed was satisfactory in terms of both sensitivity and detection limits. The reliability of the proposed approach for the detection of FFA was finally assessed by comparison of the voltammetric/chronoamperometric values with those obtained by the official method for quantification of olive oil acidity, which is an acid/base volumetric titration.

Miniaturizing and automation of free acidity measurements for uranium (VI)-HNO3 solutions: Development of a new sequential injection analysis for a sustainable radio-analytical chemistry

A miniaturized and automated approach for the determination of free acidity in solutions containing uranium (VI) is presented. The measurement technique is based on the concept of sequential injection analysis with on-line spectroscopic detection. The proposed methodology relies on the complexation and alkalimetric titration of nitric acid using a pH 5.6 sodium oxalate solution. The titration process is followed by UV/VIS detection at 650nm thanks to addition of Congo red as universal pH indicator. Mixing sequence as well as method validity was investigated by numerical simulation. This new analytical design allows fast (2.3min), reliable and accurate free acidity determination of low volume samples (10µL) containing uranium/[H+] moles ratio of 1:3 with relative standard deviation of <7.0% (n=11). The linearity range of the free nitric acid measurement is excellent up to 2.77molL−1 with a correlation coefficient (R2) of 0.995. The method is specific, presence of actinide ions up to 0.54molL−1 does not interfere on the determination of free nitric acid. In addition to automation, the developed sequential injection analysis method greatly improves the standard off-line oxalate complexation and alkalimetric titration method by reducing thousand fold the required sample volume, forty times the nuclear waste per analysis as well as the analysis time by eight fold. These analytical parameters are important especially in nuclear-related applications to improve laboratory safety, personnel exposure to radioactive samples and to drastically reduce environmental impacts or analytical radioactive waste.

Sequential Determination of Free Acidity and Plutonium Concentration in the Dissolver Solution of Fast-Breeder Reactor Spent Fuels in a Single Aliquot.

A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the plutonium concentration by a direct spectrophotometric method using a single aliquot was developed. Interference from the major fission products, which are susceptible to hydrolysis at lower acidities, had been investigated in the free acidity measurement. This method is applicable for determining the free acidity over a wide range of nitric acid concentrations as well as the plutonium concentration in the irradiated fuel solution prior to solvent extraction. Since no complexing agent is introduced during the measurement of the free acidity, the purification step is eliminated during the plutonium estimation, and the resultant analytical waste is free from corrosive chemicals and any complexing agent. Hence, uranium and plutonium can be easily recovered from analytical waste by the conventional solvent extraction method. The error involved in determining the free acidity and plutonium is within ±1% and thus this method is superior to the complexation method for routine analysis of plant samples and is also amenable for remote analysis.

Pesticide Formulations as a Key Factor Affecting Chlorpyrifos-Ethyl and Lambda-Cyhalothrin Performance against Spodoptera littoralis (Boisd.)

Formulation is a term used in various senses in various applications, and its fundamental meaning is the putting together of components in an appropriate relationships or structures, according to a formula. Several prepared formulations for chlorpyrifos-ethyl and lambdacyhalothrin as Emulsifiable Concentrate (EC) formulation were subjected to WHO chemical tests to find out which formulation is matching the requirements. The physicochemical properties of the standard commercial formulation versus the prepared formulation were determined. The emulsion stability test was determined according to WHO specification method. Besides, the determination of free acidity and alkalinity as well as, viscosity and surface tension. The results of emulsion stability test indicated that the ml separation in the prepared formulation of chlorpyrifos was 0.1 ml cream after 1 hr in the case of hard water and 0.9 ml in soft water for chlorpyrifos 48% + Calcium dodecyl benzene sulfonate (CaDBS) 2.6% + Triton X-100 2.4% (F1) compared to < 0.1 ml and < 0.3 ml in hard and soft water respectively in the second formulation which consists of chlorpyrifos 48% + dodecyl benzene sulfonate (CaDBS) 2.8% + Triton X-100 2.2% (F2).The most successful prepared formulation was (F3) which consists of chlorpyrifos 48% + Calcium dodecyl benzene sulfonate (CaDBS) 3% + Triton X-100 2% with < 0.05 ml in both hard and soft water. While the ml separation in the commercial formulation of chlorpyrifos was 0.1 ml in hard water and 0.2 ml in soft water. The cream separation in emulsion stability test of prepared formulation of lambda-cyhalothrin was not observed after 1 hr in both hard and soft water for lambda-cyhalothrin 5% + dodecyl benzene sulfonate (CaDBS) 1.8% + Triton X-100 3.2% (F1) so it was the most successful prepared formulation compared to 0.9 ml in hard water and 0 ml in soft water in the second formulation which consists of lambda-cyhalothrin 5% + dodecyl benzene sulfonate (CaDBS) 2% + Triton X-100 3% (F2). While the ml separation in the commercial formulation of lambda-cyhalothrin was 0.4 ml cream + 0.3 ml oil in hard water and 0.7 ml cream + 0.2 ml oil in soft water. The most successful formulations were tested against susceptible and field strains of Spodoptera littoralis (Boisd.). The efficiency of the two prepared formulations were determined; in comparison with the standard (commercial) formulations of chlorpyrifos-ethyl and lambda-cyhalothrin respectively, against the susceptible and field strains of S. littoralis (Boisd.). Also, the effect of adding the synergist (Sylgard 309®) to each treatment was determined. In the susceptible strain after 48 hours bioassay; LC50 value for the prepared formulation of chlorpyrifos was10.12 ppm and after adding Sylgard 309® the result was found to be 7.14 ppm, while LC50 values for its commercial formulation alone and/or with Sylgard 309® were 13.74 and 9.61 ppm, respectively. LC50value for the prepared formulation of lambda-cyhalothrin was 85.70 ppm; after adding Sylgard 309® became 68.34 ppm, while LC50 for the commercial formulation of lambdacyhalothrin alone and/or with Sylgard 309® were 152.54 and 108.52 ppm, respectively. In the field strain after 48 hours bioassay; LC50 value for the prepared formulation of chlorpyrifos was 17.89 ppm, but with the addition of Sylgard 309®the result showed a magnificent effect as of 13.77 ppm. For its commercial formulation only and/or in addition to Sylgard 309® LC50 values were found to be 163.19 and 154.28 ppm respectively. LC50 value for the prepared formulation of lambda-cyhalothrin was 1212.62 ppm; with the addition of Sylgard 309® was slightly decreased to 1208.23 ppm, while LC50values for the commercial formulation only and/or in addition to Sylgard 309® were 1925.87 and 1914.77 ppm, respectively. The calculation of Resistance Factor (RF) after 48 hours bioassay revealed that the field strain compared to the susceptible one of S. littoralis showed a real case of resistance to both of the commercial formulations of chlorpyrifos and lambda-cyhalothrin while the prepared formulations of each showed either the natural tolerance or the vigor tolerance case, in respect.

配位剂在测量游离酸时的应用和研究进展

游离酸度的测量是在经过合适的方法去除水解离子干扰后用碱量滴定法进行的，这些方法包括离子交换、沉淀分离、溶剂萃取和配位剂抑制。配位掩蔽法操作简单、快速、准确、重现性好和实用，特别适用于快速化学分析水解离子干扰的溶液酸度。本文综述了过去几十年文献中报道游离酸度测定时抑制水解离子的配位剂的种类和应用，以及配位剂在酸度测定中的重要性，并结合实际提出了今后的发展前景。 The determination of free acidity is carried out using alkalimetric titration after the removal of the hydrolysable ion by a suitable method such as ion exchange, precipitation or solvent extraction or suppression by complexing the metal ions. The method for masking hydrolysable ions with complexing agent is simple, fast, accurate, reproducible and practical. It is especially applicable to fast chemical analysis for the free acidity measurement of solutions containing hydrolysable metal ions. The present review gives an overview of the literature which reported categories and appli-cations of complexing agent for the suppression of hydrolysis over the past several decades. Im-portance of complexing agent has been given to free acidity measurement in the presence of hy-drolysable metal ions. According to the actual situation, the application status and the developing prospect of complexing agent is put forward.

Estimation of free acidity in some hydrolysable metal ions present in reprocessing streams by fiber optic aided spectrophotometry

A fiber optic aided spectrophotometric technique has been developed for the determination of free acidity in nuclear fuel reprocessing streams. In this method, nitric acid forms yellow colour complex with chrome azurol s. The system obeys Lambert–Beer’s law at 542 nm in the range of acidity 4–14 M. The molar absorption coefficient (e) and Sandell’s sensitivity (S) of complex are 5.23 × 103 L.mol−1.cm−1 and 1.91 × 10−4 µg/cm2 respectively. Relative standard deviation is less than 1 % and correlation coefficient is 0.999. Results of the present method are in good agreement with those obtained by the standard procedure.

Determination of free acidity in aluminium sulphate and alum using hexamine and potassium fluoride as complexing agent

The paper describes a modification effected in respect of the conventional fluoride method for determination of free acidity in aluminium sulphate and alum, by using hexamine as an acid binder in addition to potassium fluroide as complexing agent.

Free acidity measurement – A review

Free acidity is an important parameter especially in the presence of hydrolysable ions. Several methods have been developed for the determination of free acidity, attributing due importance to the accuracy and the precision of the measurement with the aim of the easiness of the methodology as well as post-measurement recovery in mind. This review covers important methods for the determination of free acidity with emphasis on actinide containing solutions, reported in the literature over the past several decades classifying them into different categories.

Potentiometric determination of free acidity in presence of hydrolysable ions and a sequential determination of hydrazine

A simple potentiometric method for the determination of free acidity in presence of hydrolysable ions and sequential determination of hydrazine is developed and described. Both free acid and hydrazine are estimated from the same aliquot. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 1.2% relative standard deviation. Hydrazine content has also been determined in the same aliquot with a recovery of nitric acid is 99% with 2% relative standard deviation. The major advantage of the method is that generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal.

Sequential determination of free acidity and hydrazine in presence of hydrolysable ions

Abstract A simple method for the sequential determination of free acidity and hydrazine in presence of hydrolysable ions is developed and described. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 3% relative standard deviation. The major advantage of the method is that it uses sodium carbonate a primary standard as titrant and generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal.

Sequential determination of uranium (IV), free acidity and hydrazine in a single aliquot

A simple analytical procedure for the sequential determination of uranium (IV), free acidity and hydrazine in presence of hydrolysable ions is developed and described. In this method, first, uranium (IV) is determined using fiber optic aided spectrophotometry then same solution is used for determination of free acidity and hydrazine. Free acid is titrated with standard sodium carbonate solution after uranium (IV) is masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. The overall recovery of uranium (IV), nitric acid and hydrazine is 98% with 3% relative standard deviation respectively. The major advantage of the method is that it uses sodium carbonate a primary standard as titrant and generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal.

A robust multisyringe system for process flow analysis. Part II. A multi-commuted injection system applied to the photometric determination of free acidity and iron(III) in metallurgical solutions.

A new software-controlled volume-based system for sample introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one or two additional commutation valves, the multi-commuted injection of precise sample volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Three configurations were implemented in order to achieve two different tasks: the single injection of a sample in a two- or three-channels manifold, and the dual injection into different streams. The two channel flow system using the single injection was applied to the determination of free acidity in diluted samples containing high levels of iron(III), by employing the single point titration methodology. The precipitation of ferric hydroxide was prevented using the ammonium and sodium salts of oxalate and acetate as buffer titrant. Methyl Red was employed as indicator. The procedure allows determination of acid concentration in solutions with a Fe(III)/H+ molar ratio up to 0.2. Samples with higher Fe(III)/H+ molar ratios were spiked with a known strong acid at dilution. The three-channel configuration was applied to the determination of ferric ions, using, as reagent, a merging mixture of sulfuric acid and potassium thiocyanate. The double injection system was implemented in series in a single (three-channel) manifold in such a way that a different injection volume and a changed reagent were used for each analyte. It was applied to the separated or sequential determination of free acidity and ferric ions. In this configuration, iron(III) was determined using 0.5-0.7% (w/v) sodium salicylate solution as reagent. The systems can operate at up to 100, 84 and 78 injections per hour, respectively. Determinations on synthetic and process samples compared well with the reference values and procedures. Recoveries of 95-102% with a maximum RSD value of 5.4% were found for acidity. The respective values obtained for iron determinations were 96-105% and 4.3%.

Rapid titrimetric determination of free acidity in process samples of uranyl nitrate

A simple titrimetric method for the rapid determination of free nitric acid associated with process stream samples of uranyl nitrate is described. The hydrolysable ions present in the samples are protected from interference by complexing them with sodium fluoride or potassium oxalate. Sodium hydroxide is used as the titrant for the free acid. A mixed indicator of Bromothymol Blue and Neutral Red with a transformation point at pH 7.2 is used for the detection of the end-point when sodium fluoride is the complexant. Another mixed indicator of Methyl Red and Methylene Blue with a transformation point at pH 5.4 is used when potassium oxalate is used as the complexant. A precision of 0.02 mol l–1 is attainable in both cases. The results obtained compared well with those obtained using potassium hexacyanoferrate(II) as the complexant. For samples containing larger amounts of soluble silica, potassium oxalate is preferred over sodium fluoride as the latter reacts with silica, releasing hydroxyl ions and leading to lower values of free acidity. Also, potassium oxalate is superior to sodium fluoride as it generates no corrosive analytical waste.

Titrimetric determination of free and total acidity and the subsequent deduction of zirconium content in process samples of zirconium nitrate

A simple titrimetric method for the rapid determination of free nitric acid concentration and total acidity in process samples of zirconium nitrate is described. This paper also details a theoretical method of deducing the zirconium oxide content of these samples based on the free and total acidity values. Sodium fluoride is used to complex the hydrolysable ions and sodium hydroxide is used as the titrant for the free acid. A mixed indicator of Bromocresol Purple and Bromothymol Blue (sodium salt, 0.1% each in water) was used to detect the endpoint where there is a sharp change in colour from yellow to deep blue. A precision of ±0.02 mol l–1 and ±0.5 g l–1 is attainable for acidity values and zirconium oxide concentrations, respectively. The free acidity values are in good agreement with those calculated, based on the total acidity and total concentration of the hydrolysable ions present in the medium. The zirconium throughput values calculated from the total and free acidities compared favourably with the gravimetric values estimated by precipitating zirconium (hafnium) as mandelate followed by ignition to produce the oxide. Applicability of various ligands such as oxalate, tartrate, citrate and ethylenediaminetetraacetic acid as alternative complexants is also investigated and it is observed that the zirconium complexes formed with these complexants (except that with cupferron) hydrolyse significantly and cannot be used as complexants for the direct determination of free acidity. The use of cupferron was found to be limited because of poor precision.

A constant current coulometric method for the determination of free acidity in uranium solutions

A method for the determination of free acidity in process solutions containing hydrolyzable ions like U(VI), Pu(IV), etc., has been developed. This method involves the titration of the free acid with electrogenerated hydroxide ions to a preset value of pH after complexing the metal ions with sodium sulfate. This method can by easily automated, requires small sample volumes and gives accurate results with good precision for samples with [UI]/[acid] mole ratios ranging from 0.25 to 16.

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions using sulfate as complexing agent

In this paper free acid and uranium present together in the range of 0.05–3.0 meq and 20–250 mg, respectively, have been determined by potentiometric titration, using Na2SO4 and (NH4)2SO4 complexants and NaOH and Na2CO3 as titrants. The results are presented as percentage recovery of free acidity and uranium over the range studied. It has been shown that percentage recovery of free acidity suggests a bias which varied from −5% to +74% at different free acidity and uranium concentrations for the Na2SO4−NaOH, Na2SO4−Na2CO3 and (NH4)2SO4−NaOH complexant — titrant combinations. The percentage recovery of uranium always showed a positive bias which could be up to +8% for extreme free acidity — uranium ratios in the case of Na2SO4−Na2CO3 complexant — titrant combination. For the other Na2SO4−NaOH and (NH4)2SO4−NaOH complexant — titrant combinations a positive bias of up to only +4% has been noticed.

Determination of free and total acidity in small volumes ? development of a FIA-gradient mixing technique

Flow injection analysis associated with a gradient mixing technique can be used for the determination of free acidity and total acidity (sum of free and bonded hydrogen ions) in a few microliters by reaction with suitable acid/base indicators and UV/VIS-detection. A rapid analysis of the two parameters in single raindrops in dependence on their size is possible [1].