Acid In Soft Drinks Research Articles

Ce4+/Ce3+ as the switch of AIE-copper nanoclusters for highly selective detection of ascorbic acid in soft drinks

An ultrasimple “turn-on” sensor for indirectly detecting ascorbic acid (AA) was prepared using N-acetyl-L-cysteine stabilized copper nanoclusters (NAC-CuNCs) via the AIE (aggregation-induced emission) effect controlled by Ce4+/Ce3+ redox reaction. This sensor fully utilizes the different properties of Ce4+ and Ce3+. Non-emissive NAC-CuNCs were synthesized by a facile reduction method. NAC-CuNCs easily aggregate in the presence of Ce3+ due to AIE, resulting in fluorescence enhancement. However, this phenomenon cannot be observed in the presence of Ce4+. Ce4+ possesses strong oxidizing ability and produces Ce3+ by reacting with AA via a redox reaction, followed by switching on the luminescence of NAC-CuNCs. Moreover, the fluorescence intensity (FI) of NAC-CuNCs increases with the concentration of AA in the range of 4–60 µM, with the limit of detection (LOD) as low as 0.26 µM. This probe with excellent sensitivity and selectivity was successfully used in the determination of AA in soft drinks.

Ascorbic acid as an alternative coreactant for luminol reaction and sensitive chemiluminescence determination of ascorbic acid in soft drinks

Ascorbic acid can serve as an efficient coreactant for luminol chemiluminescence (CL) reaction. An observable CL emission is produced when mixing ascorbic acid with luminol in an alkaline condition. The CL signal is further dramatically enhanced by cobalt(II) ions. This CL system was exploited as a new method for direct determination of ascorbic acid with a flow injection mode. A good linear response is acquired between the CL signal and ascorbic acid concentration in 5.0–1000.0 ng/mL range with a detection limit of 1.3 ng/mL. The relative standard deviations are 2.3% for intra–day (n = 11) and 3.7% for inter–day (n = 3) by parallel determination of 0.5 μg/mL ascorbic acid solution. The method has good selectivity for ascorbic acid since no obvious responses are observed for a variety of inorganic ions and biological substances. The practicability of the method has been demonstrated by the analysis of ascorbic acid in some soft drinks.

An Electrochemical Sensor for Quantitation of the Oral Health Care Agent Chlorogenic Acid Based on Bimetallic Nanowires with Functionalized Reduced Graphene Oxide Nanohybrids.

Chlorogenic acid (CGA), a phenolic acid from coffee, has been regarded as a powerful ingredient against oxidative stress and inflammation. Meanwhile, its healing feature to interfere with periodontal disease (PD) makes it a promising drug candidate. However, the existing methods for chlorogenic acid detection limit its practical application in purification and further pharmacological study in stomatology due to their lack of accuracy and productivity. Therefore, it is crucial to find a forceful approach to precisely evaluate CGA for an in-depth anti-PD study. In this work, we reported a facile and controllable synthesis of Pt@Pd nanowires (NWs) in a non-compacted core–shell structure with high electrocatalytic activity. In addition, polyethylenimine (PEI)-capped reduced graphene oxide (rGO) nanoflakes provided large binding sites for a network structure composed of interweaved Pt@Pd nanowires and protected hemin from self-destruction, which empowered Pt@Pd NWs-Hemin-PEI-rGO nanohybrids to own a large electroactive surface area and great electrochemical property for CGA detection. The enzyme-free electrochemical sensor based on Pt@Pd NWs-Hemin-PEI-rGO displayed a favorable capacity for trace CGA detection with a detection limit of 7.8 nM and a wide linear range of 0.5 μM to 4 mM. The exceptional sensitivity and selectivity of the sensor made it accomplish the measurements of chlorogenic acid in soft drinks and coffee with high consistency of HPLC results. The satisfactory performance of the obtained sensor enables it to be used for quality control and study of drug metabolism in PD treatments.

Determination of quercetin in the presence of tannic acid in soft drinks based on carbon nanotubes modified electrode using chemometric approaches

In the present study, determination of quercetin (QU) was studied in the presence of unexpected electroactive interference (tannic acid, TA) using electrochemical and chemometric methods. At first, the oxidation peak current of QU was optimized in the presence of TA by multivariate optimization strategy. The analysis was performed at the surface of a multi-walled carbon nanotubes modified carbon paste electrode (MWCNTs/CPE). Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of the four variables on the determination of QU in the presence of TA. After modification, determination of QU was investigated in the presence of TA by differential pulse voltammetry (DPV). But the two components showed intense overlapping voltammetric peaks. Therefore, it was impossible to analyze the two analytes by DPV technique. For overcoming the problem chemometric methods were assisted with voltammetric techniques. Multivariate curve resolution with alternating least squares (MCR-ALS) was applied for resolving of these voltammograms. Then, limit of detection (LOD) for QU at the present of TA was obtained 1.96 nM. The results indicated that MWCNTs/CPE could be employed for the determination of QU in presence of TA in soft drinks with satisfactory results.

New approach to H-point standard addition method for detection and elimination of unspecific interferences in samples with unknown matrix

A novel method for correction of unknown unspecific (additive) interferences was developed in sequential injection analysis (SIA) using a Lab on Valve module (LOV) with spectrophotometric detection. The method implements a novel idea to calibrate by the standard addition method in several different chemical conditions created in such a way to measure different signal for an analyte and unchanged signal for interferents causing additive effect. This approach, being an enhancement of the H-point standard addition method (HPSAM), enables to quantify unbiased concentration of an analyte in the presence of unknown interferences. The method was tested on the example of the determination of ascorbic acid in soft drinks and juices basing on reduction of Fe(III) to Fe(II) and reaction of the latter with o-phenanthroline to the ferroin complex absorbing at 512.0nm. The analytical utility of the method has been verified and confirmed by the spectrophotometric determination of total acidity in rose and red wines in the presence of bromothymol blue absorbing at 616.0nm. Calibration solutions were prepared automatically in the designed flow system. Ascorbic acid was determined with LOD of 1.4mgL−1 and LOQ of 4.2mgL−1 within linear working range up to 80mgL−1, while in case of the determination of total acidity the values of 4.2, 11.8 and 100, respectively, were obtained. A sample was consumed in volumes of 400 and 1000µL in both cases. The analyses are simple, “green”, and non-expensive. The developed method is readily applicable to analysis of real samples of complex unknown matrices and adaptable to different analytical methods.

Levels of Benzoic Acid in Soft Drinks and Fruit Juices in Ghana

Benzoic acid is one of the most commonly used food preservatives in the food and beverage industry in Ghana. The maximum accepted level of benzoic acid in beverages stipulated by national and European legislation is 150 ppm. Thirty four (34) different brands of soft drinks and 16 brands of fruit juices available on the markets and shops in Ghana were analysed for benzoic acid by high performance liquid chromatography with a UV detector. Chromatographic separation was achieved with phenomenex synergi 4μ polar – RP 80A 150×2mm 4 micron column with ammonium acetate buffer (pH = 4.4) and acetonitrile (90:10) as the mobile phase with a flow rate of 0.4 mL/min. The objective of this work was to determine the levels of benzoic acid in soft drinks and fruit juices on the markets of Ghana. The concentration of benzoic acid in the samples was calculated by external standard method and the level of benzoic acid ranged from not detected to 564.00 mg/L for the soft drinks and from not detected to 148 mg/L for the fruit juice respectively. The mean recoveries for both soft and fruit drinks ranged from 107 to 110%. Six (17.60%) of the soft drink samples contained levels of benzoic acid above the 150 mg/L which is the limit set by World Health Organization (WHO). The levels of benzoic acid in the fruit juice samples were within stipulated limit. From the results, the Ghana Food and Drugs Authority needs to monitor and regulate levels of preservatives used by some of the soft drinks manufacturers in Ghana especially those whose products exceeded the set limit.

Risk assessment of additives through soft drinks and nectars consumption on Portuguese population: A 2010 survey

This study investigated whether the Portuguese population is at risk of exceeding ADI levels for acesulfame-K, saccharin, aspartame, caffeine, benzoic and sorbic acid through an assessment of dietary intake of additives and specific consumption of four types of beverages, traditional soft drinks and soft drinks based on mineral waters, energetic drinks, and nectars.The highest mean levels of additives were found for caffeine in energetic drinks, 293.5mg/L, for saccharin in traditional soft drinks, 18.4mg/L, for acesulfame-K and aspartame in nectars, with 88.2 and 97.8mg/L, respectively, for benzoic acid in traditional soft drinks, 125.7mg/L, and for sorbic acid in soft drinks based on mineral water, 166.5mg/L.Traditional soft drinks presented the highest acceptable daily intake percentages (ADIs%) for acesulfame-K, aspartame, benzoic and sorbic acid and similar value for saccharin (0.5%) when compared with soft drinks based on mineral water, 0.7%, 0.08%, 7.3%, and 1.92% versus 0.2%, 0.053%, 0.6%, and 0.28%, respectively. However for saccharin the highest percentage of ADI was obtained for nectars, 0.9%, in comparison with both types of soft drinks, 0.5%.Therefore, it is concluded that the Portuguese population is not at risk of exceeding the established ADIs for the studied additives.

PENETAPAN KADAR ASAM BENZOAT DALAM BEBERAPA MERK DAGANG MINUMAN RINGAN SECARA SPEKTROFOTOMETRI ULTRAVIOLET

Benzoic acid is one of the synthetic preservatives, work effectively at pH 2.5 to 4.0, therefore it is widely used in acidic food or drink. This study aims to determine benzoic acid content in some soft drink products, their conformity with Permenkes RI No.722/Menkes/Per/IX/88 on food additives, and to find out if there were any variance of benzoid acid content in a different kinds of soft drink products. Determination of benzoid acid levels was performed by ultraviolet spectrophotometry following solvent extraction of the benzoid acid with chloroform. Qualitatively, it was found that all of the sample contained benzoid acid. Quantitatively, the amount of benzoid acid in sample A was 227,73 mg/kg of materials; sample B was 182,38 mg/kg of materials; sampel C was 259,52 mg/kg of materials; sample D was 325,01 mg/kg of materials; sample E was 357,33 mg/kg of material. The result indicated that there were variance of benzoid acid content in different soft drink products. The use of benzoic acid in soft drinks was lower compaired to that of Permenkes RI No.722/Menkes/Per/IX/88 (600 mg/kg of materials).

Estimated intake of benzoic and sorbic acids in Denmark

The monitoring of food additives and recent dietary surveys carried out in Denmark have earlier been used to estimate the intake of sweeteners and nitrite in relation to acceptable daily intakes. The ubiquitous use of the preservatives benzoic and sorbic acids raises the question of the magnitude of the intake of these preservatives in relation to acceptable daily intakes. This area is explored in this paper. The content of benzoic and sorbic acids in all food groups, where they are allowed, was monitored in Denmark 17 times between 2001 and 2006 with a total of 1526 samples. Transgressions of maximum limits, illegal use or declaration faults were found in about 3% of samples. From repeated investigations on fat-based foods (salads and dressings), marmalade and stewed fruit, it is concluded that the amounts used in industry have been relatively stable throughout the whole period, although limited data for marmalade show some variation. Most foods in the categories soft drinks, dressings, fat-based salads, pickled herrings, and marmalade contain benzoic and sorbic acid, and sliced bread also contains in some cases sorbic acid. The median daily intake and intake distribution of benzoic and sorbic acids were calculated with data from the Danish National Survey of Dietary Habits and Physical Activity (age from 4 to 75 years) conducted in 2000–2004 with 5785 participants. The median intakes of both benzoic acid and sorbic acid are well below the acceptable daily intakes of 0–5 and 0–25 mg kg−1 body weight (bw) day−1 for benzoic and sorbic acid, respectively. However, the 90th percentile based on the average of the samples with a content of benzoic acid is higher than the acceptable daily intake for both men and women, with the highest value of 16 mg kg−1 bw day−1 for both boys and girls in the 4–6-year-old age group. Based on the average of all samples, the 95th percentile is over the acceptable daily intake for men up to 34 years and for women up to 24 years, and the 90th percentile for men up to 18 years and for women up to 10 years. Soft drinks, salads and dressings are the main contributors to benzoic acid intake. The sorbic acid intake based on the average of all samples is well below the acceptable daily intake. However, for the intake based on the average of samples with content, the 95th percentile exceeds the acceptable daily intake. This is caused by the dominating contribution to the intake of sorbic acid from sliced bread, but since only seven out of 42 samples have added sorbic acid, the calculation based on the average of samples with content will exaggerate the intake. With a built-in safety factor of 100 in the acceptable daily intakes and judging from the literature, the high intakes of benzoic acid should not cause any concern for ill-effects. However, there must be a reason to reconsider the maximum limits especially for benzoic acid in soft drinks, dressings and salads and for sorbic acid in sliced bread.

Location Depending Textures of the Human Dental Enamel

Dental enamel is the most highly mineralised and hardest biological tissue in human body [1]. Dental enamel is made of hydroxylapatite (HAP) - Ca5(PO4)3(OH), which is hexagonal (6/m). The lattice parameters are a = b = 0.9418 nm und c = 0.6875 nm [1]. Although HAP is a very hard mineral, it can be dissolved easily in a process which is known as enamel demineralization by lactic acid produced by bacteria. Also the direct consumption of acid (e.g. citric, lactic or phosphoric acid in soft drinks) can harm the dental enamel in a similar way. These processes can damage the dental enamel. It will be dissolved completely and a cavity occurs. The cavity must then be cleaned and filled. It exists a lot of dental fillings, like gold, amalgam, ceramics or polymeric materials. After filling other dangers can occur: The mechanical properties of the materials used to fill cavities can differ strongly from the ones of the dental enamel itself. In the worst case, the filling of a tooth can damage the enamel of the opposite tooth by chewing if the interaction of enamel and filling is not equivalent, so that the harder fillings can abrade the softer enamel of the healthy tooth at the opposite side. This could be avoided if the anisotropic mechanical properties of dental enamel would be known in detail, hence then another filling could be searched or fabricated as an equivalent opponent for the dental enamel with equal properties. To find such a material, one has to characterise the properties of dental enamel first in detail for the different types of teeth (incisor, canine, premolar and molar). This is here exemplary done for a human incisor tooth by texture analysis with the program MAUD from 2D synchrotron transmission images [2,3,4].

Occurrence of caffeine, saccharin, benzoic acid and sorbic acid in soft drinks and nectars in Portugal and subsequent exposure assessment

A reliable method for the determination of benzoic and sorbic acids, caffeine and saccharin in soft drink and nectars using high performance liquid chromatography and UV detection was validated. The chromatographic separation was achieved with a C18 column (250 × 4.6 mm) and one buffered mobile phase, KH 2PO 4 0.02 M/ACN (90:10)/phosphoric acid at pH 4.2. The effluent was monitored at 220 nm. Benzoic acid was detected in 19 soft drinks, being 11 traditional soft drinks and 8 based on mineral water, with mean concentrations of 158 and 148 mg/L, respectively. Fifteen samples, 7 traditional and 8 based on mineral water, contained sorbic acid, with mean concentrations of 172 and 188 mg/L, respectively. Saccharin and caffeine were not detected in soft drinks based on mineral waters. In contrast, 6 samples of traditional drinks contained both additives, with mean levels of 75 and 97 mg/L, respectively. The four additives were not detected in nectar samples. According to European Union and Portuguese legislation, the maximum permitted level (MPL) for benzoic acid was exceeded in 10 soft drinks, and the MPL for sorbic acid overlapped in 3 samples of the referred samples. Two samples exceeded the MPL for the sum of both preservatives, and in 1 sample the MPL for saccharin was overlapped. The estimated daily intakes (EDI) of benzoic, sorbic acid, and saccharin for the average consumer were below the acceptable daily intakes (ADIs). For benzoic acid, the EDIs were 0.25 and 0.32 mg/kg b.w./day, representing 4.9%, and 6.4% of the ADI, respectively for traditional soft drinks and soft drinks based on mineral water. A similar situation was observed for sorbic acid. In this way, the EDIs were 0.17 and 0.41 mg/kg b.w./day, representing only 0.68% and 1.6% of the ADI for the same kind of drinks. For saccharin, the EDI represents 1.28% of the ADI. The EDI for caffeine was 0.08 mg/kg b.w./day.

Study on the Performance of the Headspace Liquid-Phase Microextraction, Gas Chromatography−Mass Spectrometry in the Determination of Sorbic and Benzoic Acids in Soft Drinks and Environmental Water Samples

A simple, efficient and virtually solventless headspace liquid-phase microextraction (HS-LPME) technique, combined with gas chromatography-mass spectrometry (GC-MS), was developed for the analysis of sorbic acid (SA) and benzoic acid (BA) in soft drinks and environmental water samples. A microdrop of organic solvent was suspended from the tip of a microsyringe needle over the headspace of the stirred sample solution, containing the analytes for a desired time. The microdrop was then retracted into the microsyringe and directly injected into the GC-MS, without any further pretreatment. Initially, microextraction efficiency factors were optimized, and the optimum experimental conditions found were as follows: 2.5 microL toluene microdrop exposed for 20 min over the headspace of a 6.5 mL aqueous sample (45 degrees C), containing 3 M of NaCl with pH of 1.5 and stirred at 1000 rpm. Under the optimized extraction conditions, preconcentration factors of 154 and 198, limits of detection of 0.3 and 0.1 microg L(-1) (S/N=3) with dynamic linear ranges of 1-500 and 0.5-500 microg L(-1), were obtained for SA and BA respectively. A good repeatability (RSD<10.3%, n=8) and satisfactory linearity (r(2) >or= 0.99) of results were achieved. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 90 to 113%. The method proved to be rapid and cost-effective and is a green procedure for screening purposes.

Acid-base titration curves in an integrated computer learning environment

The topic of acid-base reactions is a regular component of many chemistry curricula that requires integrated understanding of various areas of introductory chemistry. Many students have considerable difficulties understanding the concepts and processes involved. It has been suggested and confirmed by research that students may benefit from computer-supported activities such as data logging, simulation and modeling. In this paper we review the different methods of using computer acquisition and modeling to examine acid-base titration and we discuss how a versatile, integrated computer learning environment can be successfully applied to this end. The environment integrates, amongst other things, measurement, a control tool, and a modeling tool: using an inexpensive step-motor buret, automated pH measurement in acid-base titration can be realized and measured data can then be compared graphically and in tabular form with data computed via the (text-based or graphical) system dynamics modeling tool. In this paper we discuss concrete examples, taken from an in-service teacher training course and culminating in the student practical investigation of analysis of acid in soft drinks. We also show how computer algebra can assist to find the mathematical formulas needed for computing a titration curve. We discuss the design of instructional materials and the didactical approach of integrating data logging and modeling in acid-base chemistry education.

Determination of benzoic acid in soft drinks by gas chromatography with on-line pyrolytic methylation technique

A new application of pyrolytic methylation was developed to determine benzoic acid in soft drinks by gas chromatography (GC) without using any pretreatment procedures and special pyrolyzer. With the on-line pyrolytic methylation by tetramethylammonium hydroxide (TMAH), benzoic acid was converted into its corresponding methyl ester in the injector at 280 °C. Thus, samples containing benzoic acid could be well determined by direct-injection in GC on the medium polar stationary phase column. To obtain optimum methylation conditions, important factors were investigated and then applied to the following experiments. The results were obtained as following: 280 °C as reaction temperature, 2:1 as the proportion of TMAH to benzoic acid. The storage time of mixed solution had no obvious effect on the area of benzoic acid methyl ester peak. With the p-xylene as an inter-standard, GC behaviors were investigated under these optimum conditions. The linear range achieved for benzoic acid was 1–10,000 mg/l with the correlation coefficient of 0.9985. The precision was quite high with the R.S.D. of 2.8% and the limit of detection reached 0.1 mg/l. The potential of the proposed method was assessed by applying it to the determination of benzoic acid in soft drinks. The results obtained coincided with the statement on the labels and all of the detected data were below the maximum permitted concentration of the European Union Legislation. This on-line pyrolytic methylation technique was proved to be simple to implement, sensitive and selective.

Flow injection spectrophotometric determination of ascorbic acid in soft drinks and beer.

Two spectrophotometric methods, a photochemical and a non-photochemical, for the determination of ascorbic acid in soft drinks and beer using a flow-injection system are proposed. The non-photochemical method is based on the redox reaction that takes place between ascorbic acid and Fe(III), yielding dehydroascorbic acid and Fe(II). Fe(II) reacts with 1,10-phenantroline, originating the reddish orange Fe(phen)3(2+) complex (ferroin). This complex is spectrophotometrically monitored at 512 nm, and the signal is directly related to the concentration of ascorbic acid in the sample. The photochemical method has the same basis, nevertheless, uses the irradiation with visible light to enhance the redox reaction and so achieve higher sensitivities in the analysis. The non-photochemical method shows a linear range between 5 and 80 microg mL(-1), with a relative standard deviation of 1.6% (n = 11), a detection limit of 2.7 microg mL(-1) and a sample throughput of 60 samples h(-1). The photochemical method shows a linear range between 1 and 80 microg mL(-1), with a relative standard deviation of 1.0% (n = 11 ), a detection limit of 0.5 microg mL(-1) and a sample throughput of 40 samples h(-1).

Determination of citric acid in soft drinks using flow injection with potentiometric detection

A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with copper (II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations of citric acid in the range of 1 × 10–3 mol/L – 1 × 10–2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0% to 101.0%. The system allows a sampling frequency of 60 samples/h.

Ion Chromatographic Determination of L-Ascorbic Acid, Sulfite, Sulfide and Thiosulfate Using a Cation-Exchanger of Low Crosslinking

L-Ascorbic acid, sulfite, sulfide and thiosulfate have each been completely separated from their mixtures by a single run of ion chromatography using columns of a sulfonated styrenedivinylbenzene copolymeric cation-exchange resin of low crosslinking (1%) and an eluent of 2.3×10-3M (M=mol dm-3) sulfuric acid containing 4%(v/v) acetonitrile. L-Ascorbic acid and sulfite as sulfurous acid were eluted early by an ion-exclusion effect of the cation-exchanger in the hydrogen form, but both the sulfide as hydrogen sulfide and the thiosulfate ion were eluted late, owing to their adsorption onto the resin bed. The sample species in the effluent were monitored by photometric measurement of the excess of iodine (as triiodide) for its postcolumn reaction with each species separated. The chromatograms obtained gave negative peaks, based on the decrease in the absorbance from background. Calibration graphs for the four species, plotted as peak-heights vs. concentrations, were linear up to 3.00×10-5M for L-ascorbic acid, 1.25×10-4M for sulfite, 5.00×10-4M for sulfide and 1.20×10-4M for thiosulfate, respectively. Detection limits as S/N=3 were 1.00×10-7M for L-ascorbic acid, 1.15×10-6M for sulfite, 1.80×10-6M for sulfide and 6.80×10-6M for thiosulfate. The proposed method was successfully applied to the determination of L-ascorbic acid in soft drinks, sulfide in hot-spring waters and sulfite in wines.

Determination of ascorbic acid in soft drinks, preserved fruit juices and pharmaceuticals by flow injection spectrophotometry: Matrix absorbance correction by treatment with sodium hydroxide

Two flow injection systems for the spectrophotometric determination of ascorbic actid at 245 nm have been described. On treatment with sodium hydroxide a fraction of the ascorbic acid was decomposed into substances, which do not absorb in UV region, and the decrease in signal measured. This was directly related to the amount of ascorbic acid present. The calibration graph was linear over the range 1–25 and 1–50 μg/ml in the two methods with a correlation coefficient of 0.9981 and 0.9994, respectively. The detection limit (2σ) was 0.5 and 0.2 μg/ml, respectively. The RSD for 1 μg/ml standard was 2.5 and 1.8% ( n = 6) in the two methods, and the sampling throughput 30/hr. The methods permitted the use of 6 μg/ml of 2-mercaptoethanol as an anti-oxidant and stabilizer for ascorbic acid, which is difficult to handle at its μg/ml level. Upon matrix absorbance correction, spiked samples that are known to contain UV-absorbing substances produced an average recovery of 101% with a RSD of 1.2%. The methods were used for the rapid and simple determination of ascorbic acid in soft drinks, preserved fruit juices and pharmaceuticals and the results thus produced compared with those obtained by previously checked methods involving titration with iodine, chloranil 2,6-dichlorophenolindophenol, and HPLC. When there was a disagreement between the results, this was traced to the presence of substances which are known to interfere in comparison methods.

High-Performance Liquid Chromatographic Determination of Ascorbic Acid in Soft Drinks and Apple Juice Using Tris(2,2′-bipyridine)ruthenium(II) Electrochemiluminescence

The electrochemiluminescence of tris(2, 2′-bipyridine)ruthenium(II) [Ru(bpy)32+] was applied to high-performance liquid chromatographic determination of ascorbic acid. Ascorbic acid was separated by a C18 reversed-phase column with a mobile phase containing 15mM NaH2PO4-K2HPO4 (pH 6.5). The eluted ascorbic acid was mixed with 0.5mM Ru(bpy)32+ within the flow tube. The solution then passed through a thin layer flow cell equipped with a glassy carbon electrode and both ascorbic acid and Ru(bpy)32+ were oxidized at +1.5V (vs. Ag/AgCl). The reaction of electrolytically formed Ru(bpy)33+ with oxidized ascorbic acid emitted light. The detection limit was 10pmol for ascorbic acid at an S/N ratio of 3, and the linear calibration range was 0.06-80nmol. The method was successfully applied to determination of ascorbic acid in soft drinks and apple juice.

Chapter 1: Introduction and Methods

This study investigated whether the Portuguese population is at risk of exceeding ADI levels for acesulfame-K, saccharin, aspartame, caffeine, benzoic and sorbic acid through an assessment of dietary intake of additives and specific consumption of four types of beverages, traditional soft drinks and soft drinks based on mineral waters, energetic drinks, and nectars.The highest mean levels of additives were found for caffeine in energetic drinks, 293.5 mg/L, for saccharin in traditional soft drinks, 18.4 mg/L, for acesulfame-K and aspartame in nectars, with 88.2 and 97.8 mg/L, respectively, for benzoic acid in traditional soft drinks, 125.7 mg/L, and for sorbic acid in soft drinks based on mineral water, 166.5 mg/L.Traditional soft drinks presented the highest acceptable daily intake percentages (ADIs%) for acesulfame-K, aspartame, benzoic and sorbic acid and similar value for saccharin (0.5%) when compared with soft drinks based on mineral water, 0.7%, 0.08%, 7.3%, and 1.92% versus 0.2%, 0.053%, 0.6%, and 0.28%, respectively. However for saccharin the highest percentage of ADI was obtained for nectars, 0.9%, in comparison with both types of soft drinks, 0.5%.Therefore, it is concluded that the Portuguese population is not at risk of exceeding the established ADIs for the studied additives.