Total Sulfite Research Articles

Quantification of Total Sulfites in Shrimp by BIOFISH 300/3000 SUL Method, Collaborative Study: Final Action 2021.09.

In December 2021, the BIOFISH 300 SUL method for the determination of total sulfites in shrimp was adopted as First Action Official Method of AnalysisSM by the AOAC INTERNATIONAL. A collaborative study was conducted in February 2023 in order to test the reproducibility of the method. The method is based on the use of a benchtop biosensor device that relates the concentration of sulfite to a quantifiable electric current signal. The sensing element, the Biotest, harbors an enzyme that specifically oxidizes sulfite, and the reaction products are electrochemically detected by the device in less than 3 minutes. The sulfite is extracted from the solid using an aqueous based buffer solution, which ensures that all sulfite is present as a free anion. 11 collaborators participated in the study of nine different shrimp samples. Values of RSDr and RSDR obtained from the statistical analysis of valid data ranged from 2.1-8.1% and 7.5-14.3%, respectively, for shrimp samples above the quantification limit of the method, set at 7 mg/kg. These results showed good repeatability and reproducibility of the method, even at concentrations below the legal threshold for sulfite in food, where the reference Optimised Monier-Williams method shows relatively high imprecision.

Electrochemical Removal of Dissolved Oxygen for the on-Site Sensing of Free Sulfites in Wines

Sulfites are a commonly used anti-oxydants, food preservatives and anti-browning agents in the food industry (dried fruits and vegetables, pickles and beverages). Sulfites play also an important role in the preservation of wines as they are used at various stages of the winemaking process to protect the wine from oxidation and help the preservation of its flavors, aromas, and color. Sulfites are present in wines as ‘free’ or they can be bound to carbohydrates, lipids, or proteins. Only the free form is active in the wine protection. Winemakers must check, the ‘free’ and total sulfite content of their wine to make sure that the concentration of sulfite is sufficiently high to protect the wine and that the total sulfite concentration is not above the maximum authorized concentration. Samples are thus sent regularly to specialized laboratories for analysis. We report here the development of an electrochemical sensor for the on-site detection of free sulfites in wine.The electrochemical determination of free sulfite can be achieved by either oxidation or reduction. The presence of many interferents (ascorbates, polyphenols) complexifies the determination based on its oxidation, while determination by reduction is simpler as dissolved oxygen is the sole interferent. However, the electrochemical signal of sulfite reduction may be hidden by the reduction of dissolved oxygen. In laboratory conditions, the interference of dissolved oxygen is usually eliminated by displacement through the bubbling of an inert gas (e.g. Ar or N2). However, as sulfite is a gas under acidic conditions, nitrogen bubbling may also remove it from the samples. We report here the principle of the electrochemical removal of dissolved oxygen in the vicinity of a sensing electrode, making on-site detection possible [1]. The local elimination of dissolved oxygen was achieved at a platinum mesh electrode distant from the sensing electrode by 250 µm. The reduction potential was carefully optimized to allow the diffusion of sulfite through the mesh and its detection at the sensor electrode. With such an experimental set-up, the amperometric response for free sulfite in wines was linear in the 7.5 – 200 mg L-1 concentration range and with a limit of detection of 7.5 mg L-1. The samples were analyzed in less than 5 minutes without the need for solution purging with an inert gas, confirming the advantage of local elimination of dissolved oxygen for on-site analysis. A series of 27 wines (14 reds and 13 whites) from various regions of France was analyzed and the results were validated by conventional iodometric titration. Our amperometric sensor demonstrated that there were no interferences other than the one from dissolved oxygen, which is removed. Even ascorbic acid, which is a major interferent for the iodometric method, did not alter the amperometric response [2].The electrochemical system was tested in an independent winery (Dahlenheim, France) to confirm the ability to perform on-site analysis in a representative working environment. The on-site results were validated by both amperometric and iodometric analysis in the lab. The ease of use and versatility of the sensor open possibilities to use this method for the detection of other food additives (e.g. nitrite), which determination is hindered by the presence of dissolved oxygen, in other types of foodstuff.[1] M. Etienne, T.X.H. Le, T. Nasir, G. Herzog, Electrochemical Filter To Remove Oxygen Interference Locally, Rapidly, and Temporarily for Sensing Applications, Anal. Chem. 92 (2020) 7425–7429. https://doi.org/10.1021/acs.analchem.0c00395.[2] J. Gajdár, G. Herzog, M. Etienne, Amperometric Sensor for Selective On-Site Analysis of Free Sulfite in Wines, ACS Sensors. 7 (2022) 2209–2217. https://doi.org/10.1021/acssensors.2c00611.

Quantification of Total Sulfite in Shrimps by BIOFISH 300 SUL Method: First Action 2021.09.

Sulfite is the oldest and most widely used additive in our food supply with antioxidant and preservative properties. Due to its allergenic-like reactions and other adverse health effects, its use is regulated by international regulatory bodies. Therefore, food industries as well as regulatory laboratories must ensure that the maximum concentration of sulfite permitted is not exceeded. The AOAC INTERNATIONAL-approved official method for the quantification of sulfites is the Optimized Monier-Williams Method (AOAC Official Method 990.28), which consists of a time-consuming titration. The present study aims to demonstrate the reliability of the BIOFISH 300 SUL, a simple, fast, and accurate method, as an alternative, for the quantification of total sulfites in shrimp, with a lower LOQ than that of the OMA 990.28, set at 10 mg/Kg. The BIOFISH 300 SUL method is a highly specific biosensor based on its proprietary enzyme-based electrode, for the rapid quantification of total sulfite. The test kit consists of an electrochemical reader (biosensor BIOFISH 300) and disposable electrodes (Biotest) that are capable of providing an electrical signal proportional to the amount of sulfite in the sample analyzed. The method mainly consists of the extraction of sulfite from the solid matrix in an aqueous solution, and its subsequent quantification by the device in less than 3 min. Comparative studies between BIOFISH 300 SUL and OMA 990.28 were conducted for naturally contaminated and spiked samples of raw and boiled shrimp with sulfite levels covering the 7-150 mg/kg range in order to determine linearity, recovery, repeatability, intermediate reproducibility, and accuracy. The BIOFISH 300 SUL method demonstrated high accuracy and precision for the whole range of quantification (7-150 mg/kg). Its ease of use and fast response make it the ideal technology to be implemented by the industry. BIOFISH 300 SUL was adopted as a First Action Official MethodSM by the AOAC Expert Review Panel for Sulfites in Seafood Methods in February 2021 after rigorous review.

Physicochemical and Sensory Properties of Wine Produced from Blended Cactus Pear (Opuntia ficus-indica) andLantana camara(L. camara) Fruits

Blending different fruits as well as adding medicinal herbs improves important physicochemical and sensorial properties of fruit wine. The present study aimed at investigating prominent physicochemical and sensory properties of wine produced from cactus pear andLantana camarafruit juice blend. Both fruit juices were characterized based on pH, sugar, titratable acidity, total phenol, and organic acid contents. The fermentation process was made at previously optimized fermentation temperature of 24.8°C, pH of 3.4, inoculum concentration (Saccharomyces cerevisiae) of 10.16% (v/v), andLantana camarafruit juice concentration of 10.66% (v/v). The final wine was characterized as having pH of 3.47 ± 0.04, 4.6 ± 0.02 g/L sugar equivalent to dextrose, 0.33 ± 0.006% titratable acidity (w/v citric acid), total phenol of 696.1 ± 22.1 mg/L equivalent to gallic acid, and 4.35 ± 0.4 mg/mL organic acid equivalent to citric acid composition. Predominant color intensity, ethanol, methanol, total sulfite, and sensory value of the final wine were measured as 48.07 ± 2.66% of yellowish color, 8.6 ± 0.68% (v/v), 124.4 ± 9.5 mg/L, 129.94 ± 4.04 mg/L, and 8.65 ± 0.92, respectively. The blendedLantana camarafruit enhanced total phenol, color, and sensory value of the final wine. Titratable acidity and methanol and sulfite contents of the final wine are in an acceptable limit compared to standards for commercial wines. Utilizing cactus pear fruit by incorporatingLantana camarafruit for health-enhancing functional food development such as fruit wines could solve the current postharvest loss of both fruits and be a means of alternative beverage.

Simultaneous determination of ethanol and total sulfite in white wine using on-line cone reservoirs membraneless gas-liquid separation flow system

This work presents the use of a single membraneless vaporization unit (MBL-VP unit) in a flow system for the simultaneous determination of ethanol and total sulfite in white wine. The flow system comprises a MBL-VP unit with three cone-shaped reservoirs and two in-house detectors, a paired emitter-detector diodes (PEDD) and a capacitively coupled contactless conductivity detector (C4D). The sample of white wine is first acidified in the flow system. Then 200-μL of the acidified sample is delivered to the donor reservoir of the MBL-VP unit in which the two acceptor reservoirs contain 200-μL of the gas acceptor reagents, viz. acidic permanganate solution and deionized water. Vaporization of ethanol and SO2(g) (converted from sulfite) from the donor into the acceptor reservoirs is carried out for 15 s. The two acceptor solutions are then simultaneously transferred for separate detection at the PEDD and C4D detectors. Decolorization of the permanganate solution by the reduction reaction with absorbed ethanol gives an increase in the PEDD signal, whereas dissolution of the SO2(g) in the water acceptor leads to an increase in conductivity and detected by the C4D. Linear calibrations were obtained in the range of 5.0–15.0% (v/v) for ethanol (PEDD signal = ((4.0 ± 0.03) × 10−2) · (%(v/v) ethanol) – ((1.85 ± 0.35) × 10−2): r2 = 0.999) and 10–200 mg L−1 for sulfite (C4D signal = ((0.64 ± 0.015) × 10−2) · (mg L−1 sulfite) – ((3.25 ± 1.64) × 10−2): r2 = 0.999). The analysis is rapid with total analysis time of 2.5 min. Percentage of recoveries were 81–104% and 88–110% for ethanol and sulfite, respectively. The method was compared with gas chromatographic analysis and iodometric titration for ethanol and sulfite, respectively, with no statistically significant difference for the analysis of seven white wine samples.

Establishing a method of HPLC involving precolumn derivatization by 2,2'-dithiobis (5-nitropyridine) to determine the sulfites in shrimps in comparison with ion chromatography.

Although sulfites are widely used in shrimp processing, the contents of residual sulfite need to be strictly controlled due to their potential toxicity. In this paper, a novel method was developed for determination of the free and total sulfites in shrimps. Major procedures of the method includes separation of free and total sulfites with ultrasound‐assisted extraction and pH adjustment for 20 min, then a precolumn derivatization was conducted by 2,2′‐Dithiobis (5‐nitropyridine) and verified by LC‐MS, and finally HPLC coupled with an ultraviolet (UV) detector was carried out. Results indicated that the UV absorption wavelength shifted from 213 (sulfites) to 320 nm (new disulfide compounds), significantly reducing the interference of natural occurring compounds and solvents in the matrix. The standard curves exhibited a good linear range of 3.2–51.2 mg/L (R 2 = 0.9996). The limit of detection (LOD) and limit of quantification (LOQ) were 0.3 and 1.0 mg/L, respectively. The contents of free and total sulfite in frozen shrimps were 26.58 ± 0.48 and 31.44 ± 0.83 mg/kg calculated by SO2, respectively. These were similar (p > 0.05) to the data obtained by the method of ion chromatography. In conclusion, the new developed method has been proved to be a reliable and economic method for effective determination of free and total sulfites in the shrimps, and the method could be expanded in determination of the sulfites in other food products.

Determination of free and total sulfur(IV) compounds in coconut water using high-resolution continuum source molecular absorption spectrometry in gas phase

This work proposes a method for the determination of free and total sulfur(IV) compounds in coconut water samples, using the high-resolution continuum source molecular absorption spectrometry. It is based on the measurement of the absorbance signal of the SO2 gas generate, which is resultant of the addition of hydrochloric acid solution on the sample containing the sulfating agent. The sulfite bound to the organic compounds is released by the addition of sodium hydroxide solution, before the generation of the SO2 gas.The optimization step was performed using multivariate methodology involving volume, concentration and flow rate of hydrochloric acid. This method was established by the sum of the absorbances obtained in the three lines of molecular absorption of the SO2 gas. This strategy allowed a procedure for the determination of sulfite with limits of detection and quantification of 0.36 and 1.21mgL−1 (for a sample volume of 10mL) and precision expressed as relative standard deviation of 5.4% and 6.4% for a coconut water sample containing 38.13 and 54.58mgL−1 of free and total sulfite, respectively.The method was applied for analyzing five coconut water samples from Salvador city, Brazil. The average contents varied from 13.0 to 55.4mgL−1 for free sulfite and from 24.7 to 66.9mgL−1 for total sulfur(IV) compounds. The samples were also analyzed employing the Ripper´s procedure, which is a reference method for the quantification of this additive. A statistical test at 95% confidence level demonstrated that there is no significant difference between the results obtained by the two methods.

Recovered Gases and Bacteria from the <i>Clostridium</i> Genus as Ecological Condition Indicators of Bottom Sediments of the Eastern Donbass Small Rivers

The results of determination of methane, total hydrogen sulfide and sulfite reducing clostridia in bottom sediments of small rivers and reservoirs of the Eastern Donbass are presented. The horizontal and vertical distribution of levels of reduced gases in bottom sediments is analyzed. The ecological condition of the bottom sediments was estimated by the clostridia titer and the methane index. The ranking of the ecological condition of bottom sediments according to the content of total hydrogen sulfide in them is performed. The relationship between pH and Eh values, methane and hydrogen sulfide concentrations and the number of sulfite reducing clostridia was studied, which allowed to discover new sides of the metabolic cycle of reduced gases in bottom sediments of freshwater ecosystems located in the zone of anthropogenic influence. The researches carried out allow to draw a conclusion about significant prolonged anthropogenic impact, mainly of domestic and industrial wastewater on water objects of the Eastern Donbass.

Green analytical flow method for the determination of total sulfite in wine using membraneless gas–liquid separation with contactless conductivity detection

New and green automated flow-method based on membraneless vaporization technique suitable for monitoring of total sulfite in wine.

A model for performance of sulfite oxidation of ammonia-based flue gas desulfurization system

A mathematical model was developed to simulate the oxidation of total sulfite in the holding tank of ammonia-based flue gas desulfurization (FGD) system. The model could provide predictions of the oxidation ratio of total sulfite at different operating condition such as pH, concentration of total sulfur, air flow and residence time. The calculation results of an ammonia-based FGD system for 2 × 150 MW boilers by this model were compared to that of corresponding measured values. The comparison results show that the simulated oxidation ratio of total sulfite agrees well with the measured data. The difference between calculated values and measured data is below 4.2%. This model appears to be beneficial for optimizing design and operation of total sulfite oxidation of an ammonia-based FGD system.

In vitro antioxidant activity and phenolic composition of Georgian, Central and West European wines

Georgia is a traditional country of viticulture and winemaking but only a few studies have been focused on wines originating from this area. In this study, we compared antioxidant effect, total sulfite content and concentration of 14 phenolic compounds of some native Georgian red and white wines with wines commonly produced in Central and Western Europe. Georgian red wines exhibited higher antioxidant capacity in DPPH, ORAC and total phenolic content assay. Further, Georgian red wines were richer in quercetin, kaempferol and syringic acid content, while the concentration of trans-resveratrol was lower than in Central and West European red wines. While differences among red wines from different origins and cultivars were observed, winemaking technology was the most important factor in the case of white wines. Kakhetian method increased antioxidant effect and levels of some phenolic compounds in comparison with white wines prepared by common European method. Our findings suggest that Georgian wines deserve further attention because of their high content of phenolics and high antioxidant capacity.

Determination of Free and Total Sulfite in Red Globe Grape by Ion Chromatography

Determination of Free and Total Sulfite in Red Globe Grape by Ion Chromatography

Physico-chemical and microbiological properties of manna (gezo) samples collected from retailers in south-east of Turkey

Manna (gezo) is a traditional sweet, which is commonly consumed in south-east of Turkey. However, there is a myth about the sweet that it is strongly believed by the people within the region that manna is treated as a magical substance that rains down from the sky and it was thought that it could cure some diseases. In this study, totally 30 manna samples were analyzed. The contamination rate of total mesophilic aerob bacteria, coliform bacteria, Bacillus cereus, mold, yeast, osmophilic yeast and sulfite reducing anaerobe bacteria were found 100, 26.66, 23.33, 23.33, 76.66, 96.66 and 36.66%, respectively. Salmonella spp., Listeria spp., Staphylococcus-Micrococcus and Escherichia coli could not be determined in any of the samples. Mean value of pH and moisture, dry matter, ash, protein, fat and crude cellulose of the manna samples were found 5.86, 3.49, 96.51, 13.77, 0.39, 0.79 and 8.99%, respectively. As a result, important pathogens were not determined in the manna samples. However, some indicator bacteria of hygiene such as coliform were detected. It was concluded that during the production of the manna samples might be contaminated with some microorganisms from different sources and these contaminations caused health risks.

Extraction and quantification of SO2 content in wines using a hollow fiber contactor

Sulfites [Formula: see text] or sulfur dioxide (SO2) is a preservative widely used in fruits and fruit-derived products. This study aims to propose a membrane contactor process for the selective removal and recovery of SO2 from wines in order to obtain its reliable quantification. Currently, the aspiration and Ripper methods offer a difficult quantification of the sulfite content in red wines because they involve evaporation steps of diluted compounds and a colorimetric assay, respectively. Therefore, an inexpensive and accurate methodology is not currently available for continuous monitoring of SO2 in the liquids food industry. Red wine initially acidified at pH < 1 was treated by membrane extraction at 25 ℃. This operation is based on a hydrophobic Hollow Fiber Contactor, which separates the acidified red wine in the shell side and a diluted aqueous sodium hydroxide solution as receiving solution into the lumenside in countercurrent. Sulfite and bisulfite in the acidified red wine become molecular SO2, which is evaporated through the membrane pores filled with gas. Thus, SO2 is trapped in a colorless solution and the membrane contactor controls its transfer, decreasing experimental error induced in classical methods. Experimental results using model solutions with known concentration values of [Formula: see text] show an average extraction percentage of 98.91 after 4 min. On the other hand, two types of Chilean Cabernet Sauvignon wines were analyzed with the same system to quantify the content of free and total sulfites. Results show a good agreement between these methods and the proposed technique, which shows a lower experimental variability.

Modeling and Simulation of Sulfur Dioxide Abatement with Ammonia Absorbent in the Spray Scrubber

In this paper, a model of ammonia-based wet flue gas desulfurization system was developed to simulate the process of absorption of SO2 and oxidation of total sulfite. The influence of pH, liquid-gas ratio, flue gas velocity and SO2 concentration on the desulfurization process were analyzed. The calculated desulfurization efficiency of the ammonia-based WFGD system for 2×210 t•h-1 boilers unit in China were compared to that of corresponding measured ones. The results show that the simulated values agreed well with the measured values for the operating conditions of pH, liquid/gas ratio and SO2 concentration. Corresponding amount of air needed for oxidation of total sulfite formed in SO2 absorption process was also calculated.

Determination of Sulfite in Beer Based on Fluorescent Derivatives and Liquid Chromatographic Separation

A method was developed for quantification of sulfite in beer based on derivatization with the maleimide-derived probe ThioGlo 1 followed by separation of fluorescent adducts by reversed-phase high-performance liquid chromatography and fluorescence detection. Sulfite gave two ThioGlo 1 derivatives and it was shown by mass spectrometry that both had identical mass spectra. Matrix effects were observed when constructing sulfite standard curves in different beers and, therefore, use of a matrix-matched calibration curve is proposed. ThioGlo 1 was found to generate fluorescent adducts with both bound and free sulfite, providing a quantification of the total sulfite content in beer. The limit of quantification of sulfite was 0.6 mg/L and the method can be used for quantification of sulfite in highly colored beers.

Determination of Main Categories of Components in Corn Steep Liquor by Near-Infrared Spectroscopy and Partial Least-Squares Regression

Corn steep liquor (CSL) is an important raw material that has a high nutritional value and serves as a nitrogen source. This study aimed to develop a fast, versatile, cheap, and environmentally safe analytical method of quantifying the total acidity (TA) of CSL as well as its contents of dry matter (DM), total sugars (TS), total reducing sugars (TRS), total free amino acids (TFAA), total nitrogen (TN), and total sulfite (TSu). The near-infrared (NIR) spectroscopy measurements of 66 samples (22 batches) of CSL were analyzed by partial least-squares regression using several spectral preprocessing methods. Multivariate models developed in the NIR area showed good predictive abilities for DM, TA, TS, TRS, TFAA, TN, and TSu determination. These results confirm the feasibility of the multivariate spectroscopic approach as a replacement for expensive and time-consuming conventional chemical methods. Thus, a convenient and feasible method for the quality control of fermentation raw materials for food additives and fine chemicals, especially in CSL, is established.

Study of elemental mercury re-emission in a simulated wet scrubber

Mercury is a toxic pollutant that has motivated environmental regulations for emissions reduction from coal-fired power plants. Acid gas wet scrubbers are known to provide the co-benefit of SO2 control and mercury removal, when mercury is found in the flue gas in the oxidized form. The aqueous ionic chemistry in the scrubbing solution can lead to transformation of the absorbed ionic mercury to the insoluble elemental mercury form, resulting in mercury re-emission and a reduction of the scrubber mercury capture efficiency. Laboratory-scale experiments were performed in a simulated batch scrubber. The experiments were carried out to simulate a forced oxidation limestone reactor. The effect of scrubber temperature and pH, ionic mercury concentration in the liquor, total sulfite, and chloride and bromide ion concentration in solution, and O2 and CO2 concentration in the gas on mercury re-emission was investigated. Of particular interest was the investigation of the impact of slurry temperature and CO2 concentration in the gas, under conditions typical of oxy-fuel combustion condition, on mercury re-emission. The results confirm that oxidized mercury is reduced by aqueous S(IV). Higher concentrations of sulfites, chloride and bromide ions inhibit oxidized mercury transformation to elemental mercury. Higher concentrations of ionic mercury in the liquor and increased scrubber temperature and pH value results in higher re-emission levels of elemental mercury. Additionally, on the impact of oxy-fuel conditions on mercury, it was found that high availability of excess oxygen in the flue gas in contact with the scrubbing solution was found to result in lower conversion of oxidized to elemental mercury. No impact from CO2 in the flue gas was found on elemental mercury re-emission. However, higher slurry temperatures under oxy-fuel combustion conditions would lead to increased elemental mercury re-emission. For completeness, the effectiveness of sulfide-based additives for abatement of elemental mercury re-emission was also demonstrated in this study. The suppression effectiveness of sodium hydrogen sulfide, sodium sulfide, TMT15® and the Nalco-8034 reagent was found at 99%, 97%, 93% and 99%, respectively. These additives promote precipitation of ionic mercury as mercury sulfide.

Kinetics of oxidation of total sulfite in the ammonia-based wet flue gas desulfurization process

Using bubbling apparatus, the kinetics of oxidation of total sulfite in ammonia-based wet flue gas desulfurization (FGD) process was investigated by varying concentrations of SO 3 2− and SO 4 2−, pH, temperatures and air flow. The concentration range of sulfite is 0.0044–0.026 gmol L −1 and that of sulfate is 0.5–2 gmol L −1. Experiments were conducted at pH level of 4.5–6.5 and air flow ranging from 50 to 200 L h −1. In the temperature range of 303.15–333.15 K, the reaction was found to be −0.5 order with respect to sulfite. The experimental findings also showed that the bisulfite could be oxidized easier than sulfite. Thus, keeping the pH level of the solution low is conducive to the oxidation of total sulfite. The apparent activation energy for the overall oxidation was calculated to be 28.0 kJ mol −1. A kinetic model has been derived according to the experimental results. The developed kinetic model, including the operating parameters SO 3 2− concentration, SO 4 2− concentration, pH, temperature and air flow, can be applied to simulate the oxidation of total sulfite. This model would be useful for the design of the ammonia-based wet FGD system.

Determination of Total Sulfite in Wine by Ion Chromatography after In-Sample Oxidation

Sulfur dioxide (SO2) or sulfites are the most common preservatives used in winemaking. The level of total SO2 is subject to regulation. Currently, the regulatory determination of total SO2 (including sulfites) is done by the optimized Monier-Williams (OMW) method, which includes time-consuming distillation and titration steps. This paper describes the development and application of an alternative, rapid, straightforward, and reliable method for the determination of total sulfite in wine. In this method, a simple oxidation step using alkaline hydrogen peroxide (H2O2) solution is followed by ion chromatographic (IC) analysis of sulfate coupled with conductometric detection. Thirteen wines were analyzed in order to compare the in-sample oxidation method with the OMW-procedure. A t-test revealed satisfying compliance regarding sample preparation, i.e., alkaline H2O2 treatment and acidic distillation (OMW method). Comparable results were also obtained between IC analysis and acid/base titration. Our results indicate that the novel method (limit of quantification: 4 mg SO2 L(-1)) is well suited for the cost-efficient monitoring of regulatory limits.