Determination Of Sulfite Research Articles

Determination of sulfite and antimicrobial residue in imported shrimp to the USA

Incorrect usage of grow out and post-harvest products in shrimp aquaculture can lead to problems such as residue from veterinary drugs and melanosis prevention. These residues can be a serious concern for human health during handling and consumption of the shrimp. In an effort to determine if banned antimicrobial drugs were present in commercial shrimp, imported shrimp from India, Thailand, Indonesia, Vietnam, China, Bangladesh and Ecuador were purchased from retail stores in Baton Rouge, LA, USA and screened for the presence of veterinary drug residues (oxytetracycline, nitrofurantoin, chloramphenicol, fluoroquinolone and malachite green) using ELISA test kits. Additional screening with the Alert sulfite detection kit was used to determine if sulfite residue was over the legal limit of 100 ppm. Screening analysis revealed that samples were positive for nitrofurantoin (70 %), malachite green (5 %), oxytetracycline (7 %), and fluoroquinolone (17 %). No samples contained chloramphenicol residue. Using LC-MSMS validation, one sample tested positive for 60 ppm of oxytetracycline and 4 ppb of ciprofloxacin. Most samples tested positive for sulfite residue (43 %), but were within the US Food and Drug Administration (USFDA) limit (10−100 ppm). However, sulfites were not listed on any of labels of the 51 packages of imported shrimp. These drug residues and sulfites can have negative effects on human health. Results of this study confirm that veterinary drug residue is present in imported shrimp sold in the USA and all labeling rules are not followed.

Determination of sulfur compounds in biological desulfurization system by high performance liquid chromatography

Biological desulfurization is a process in which sulfur compounds are removed from gas and oil using microorganisms. It is a simple process that has mild operating conditions, high desulfurization efficiency, low energy consumption and less environmental pollution. However, there is still a lack of simple and efficient analytical methods for quantitatively analyzing the sulfur compounds in the biological desulfurization process. In order to solve this problem, the analytical method for the simultaneous determination of sulfite, thiosulfate and sulfide in biological desulfurization solutions by pre-column fluorescence derivation using high performance liquid chromatography (HPLC) was developed. The standard curves of sulfur species in this analytical method had good linear relationships with correlation coefficients of 0.999 5, 0.999 7, and 0.999 7 for sulfite, thiosulfate and sulfide, respectively. The detection limits of these sulfur compounds were 0.000 6, 0.000 7 and 0.001 1 μmol/L; the range of recovery rates were 98.17 to 101.9%, 100.9 to 102.6%, and 101.1 to 104.2%; which had good repeatability and stability. The analytical method was simple, efficient and accurate, and could be used to simultaneously determine the sulfur compounds in different biological desulfurization systems.

Method development and validation for the determination of sulfites and sulfates on the surface of mineral atmospheric samples using reverse-phase liquid chromatography

Earlier studies suggest that SO2 gas reacts at the surface of mineral dust and forms sulfites or bisulfites, which are then converted to sulfates. In order to monitor and quantify the amounts of both sulfites and sulfates formed on the surface of mineral dusts of volcanic and desert origins an accurate and precise reversed-phase liquid chromatography method was developed and validated to extract, stabilize and individually analyze sulfites and sulfates initially present on the surface of dusts exposed to SO2. The method was developed on a 25 mm Restek Ultra Column C18, Particle size: 5 μm, I.D. 4.60 mm column which was dynamically coated with 1.0 mM cetylpyridinium chloride in 7% acetonitrile solution to produce a charged surface as recommended in the literature. Mobile phase used: 1 mM Potassium Hydrogen Phthalate at pH 6.5 at a flow rate of 1.0 ml/min with negative UV–Vis detection at 255 nm in 15 min. The method was validated for specificity, linearity and range, injection repeatability, stability, robustness, limit of detection and limit of quantitation, and sample preparation and extraction reproducibility. The method was adapted for straight sulfite and sulfate quantification: (i) of environmental samples, and (ii) natural samples additionally exposed to SO2 gas in a dedicated laboratory setup. The method was then successfully applied to quantify sulfites and sulfates on natural volcanic and a desert dust samples both collected in the environment and additionally exposed to SO2 gas in the laboratory. The method can be efficiently used to identify sulfites and sulfates on fresh volcanic ash following an eruption, on aeolian desert dust exposed to industrial pollutants, as well as for laboratory investigations of sulfite and sulfate formation on the surface of minerals and natural dusts of different origins.

Simple Flow-Based System with an In-Line Membrane Gas-liquid Separation Unit and a Contactless Conductivity Detector for the Direct Determination of Sulfite in Clear and Turbid Food Samples.

This study presents a simple flow-based system for the determination of the preservative agent sulfite in food and beverages. The standard method of conversion of sulfite ions into SO2 gas by acidification is employed to separate the sulfite from sample matrices. The sample is aspirated into a donor stream of sulfuric acid. A membrane gas–liquid separation unit, also called a ‘gas-diffusion (GD)’ unit, incorporating a polytetrafluoroethylene (PTFE) hydrophobic membrane allows the generated gas to diffuse into a stream of deionized water in the acceptor line. The dissolution of the SO2 gas leads to a change in the conductivity of water which is monitored by an in-line capacitively coupled contactless conductivity detector (C4D). The conductivity change is proportional to the concentration of sulfite in the sample. In this work, both clear (wine) and turbid (fruit juice and extracts of dried fruit) were selected to demonstrate the versatility of the developed method. The method can tolerate turbidity up to 60 Nephelometric Turbidity Units (NTUs). The linear range is 5–25 mg L−1 SO32− with precision <2% RSD. The flow system employs a peristaltic pump for propelling all liquid lines. Quantitative results of sulfite were statistically comparable to those obtained from iodimetric titration for the wine samples.

Fabrication of Conductive Polypyrrole Doped Chitosan Thin Film for Sensitive Detection of Sulfite in Real Food and Biological Samples

AbstractIn this study, we reported electrochemical synthesis of conductive polypyrrole‐chitosan (PPY‐CHI) thin film for sensitive detection of sulfite in real samples. The synthesized PPY‐CHI film was characterized in terms of surface morphology, optical property, binding energy, conductivity and electrochemical properties. The synthesized copolymeric PPY‐CHI film displayed good electrocatalytic behaviour towards oxidation of sulfite. The synthesized PPY‐CHI film was used for sulfite detection using differential pulse voltammetric technique with detection limit, sensitivity and linearity of 0.21 μM (S/N=3), 15.28 μA μM cm−2 and 50–1100 μM respectively. In addition, the current responses of PPY‐CHI film towards sulfite were repeatable, reproducible response and unaffected by selected electroactive interferents. Finally, the synthesized PPY‐CHI was successfully and satisfactorily applied for determination of sulfite in real food and biological samples. The results obtained from this study highly placed PPY‐CHI film as a promising sensor for sensitive and accurate detection of sulfite in food and biological samples for human health protection.

Rapid method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis

Since seafood is susceptible to decomposition, additives may be used to maintain its quality. However, some additives may be improperly used to disguise spoilage, thus resulting in food fraud. Market growth demands faster and more reliable quality control tools that incorporate the most common additives in a single analysis. This study developed a rapid analytical method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis with indirect UV–Vis detection. Electrophoretic separation was achieved in less than 3.5 min. The background electrolyte consisted of 20 mmol L−1 of benzenesulfonic acid and 45 mmol L−1 of aminocaproic acid. After validation, the method was applied for 24 seafood real samples. Citrate was found in five samples. Four samples presented higher phosphate and sulfite concentrations than those permitted by Brazilian legislation. Good analytical performance indicates that the method is a viable alternative for food control in routine analysis.

Investigation of food products containing garlic or onion for a false positive sulphite response by LC-MS/MS

ABSTRACTIn the US, sulphites must be declared on the label if they are present in concentrations greater than 10 mg/kg (determined as) SO2 because an allergic-like response has been reported in a small subset of the population upon consumption of sulphite-containing products. The most widely used method for sulphite determination, the optimised Monier-Williams (OMW), produces false positive results with vegetables from the Allium (garlic) and Brassica (cabbage) genera due to extraction conditions that are thought to cause endogenous sulphur compounds to release SO2. Recently, an LC-MS/MS method was developed for sulphites but has only been tested with samples that are 100% Allium or Brassica. Since regulatory samples may contain these vegetables as ingredients, additional investigations were necessary to determine the potential extent of false positives. Four blank matrices, chips, phyllo shells, hummus, and quinoa were spiked with various concentrations of onion and garlic powders. The sulphite concentrations were determined using an LC-MS/MS method. The matrix is extracted with a buffered formaldehyde solution, converting free and reversibly bound sulphite to the stable formaldehyde adduct, hydroxymethylsulfonate (HMS). It was determined that even at concentrations up to 8% garlic powder or 2% onion powder, the measured sulphite concentration was below the 10 mg/kg SO2 labelling threshold. Commercial dried garlic powders were evaluated to determine the variation in responses that might be encountered in future regulatory samples. Recovery studies were conducted to determine if these methods would detect added sulphite. The ability to eliminate false positives due to these ingredients will result in a greater reliability in the accurate determination of added sulphite to ensure compliance with labelling requirements.

Simultaneous and Selective Electrochemical Detection of Sulfite and Nitrite in Water Sources Using Homogeneously Dispersed Ag Nanoparticles over PANI/rGO Nanocomposite

A comprehensive investigation on synthesis, characterization and application of AgNPs@PANI/rGO nanocomposite was carried out for the simultaneous detection of sulfite and nitrite in water sources. A well dispersed and modified silver nanoparticle of uniform size, dispersed on polyaniline/reduced graphene oxide nanocomposite was prepared in the absence of an external oxidizing agent through biphasic method. The synthesized nanocomposite was characterized by FT-IR, XRD, FE-SEM and TEM analysis. The nanocomposite exhibited enhanced catalytic current for simultaneous electrochemical oxidation of sulfite and nitrite with wider peak separation window. A well-defined oxidation peak was observed at +0.40 and + 0.90 V vs Ag/AgCl for sulfite and nitrite in 0.1 M phosphate buffer. A calibration graph was obtained in the concentration range of 2.7 to 24.4 μM and 1.0 to 28.2 μM with a detection limit (LOD) of 77 nM and 56 nM for the electrochemical determination of sulfite and nitrite, respectively. The present sensor can be used for the electrochemical detection of both analytes in water sources with greater sensitivity and lower detection limits. The results obtained from the present method were validated with the published results.

A label free colorimetric assay for detection of sulfite root based on Cu2+

The reaction between sulfite and hydrogen peroxide causes the absorbance decrease, which provides the basis to determine the sulfite content that is sensitive to the absorbance change. Cu2+ can catalyze the chemical reaction between hydrogen peroxide (H2O2) and the 2,2’-Azinobis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS) effectively, which will cause the change of absorbance. In this paper, we presented an experiment system to study the influence of pH value, H2O2 content, Cu2+ content and reaction time on the reaction system. The comparison of experiment system results indicated that the optimal condition was pH value of 7.0, H2O2 of 500 μM, Cu2+ of 250 μM and 5 minutes reaction time. Under the optimal conditions, the absorbance (Y) and SO32- content (C) have a linear relationship Y=-861.35C+0.8923. The coefficient of determination (R2) in the linear relationship is 0.9983, which indicates a strong correspondence between C and Y. Then, the established method was used to detect the sulfite in wine. The recovery rate was between 96.01% and 106.90%, which proves this method is efficient for sulfite determination.

An ultrasensitive electroanalytical sensor based on MgO/SWCNTs- 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide paste electrode for the determination of ferulic acid in the presence sulfite in food samples

This research focused on fabrication of an ultrasensitive nano-molar voltammetric sensor for the determination of ferulic acid (FA) in the presence of sulfite in food samples. For this goal, we incorporated MgO/SWCNTs nanocomposite and 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][Tf2N] into the carbon paste matrix to yield the modified CPE (MgO/SWCNTs-[Bmim][Tf2N]-CPE) as an electroanalytical tool. The MgO/SWCNTs-[Bmim][Tf2N]-CPE produced an improved analytical oxidation signal for FA which was 3 0.17 times more than the unmodified sensors. The electrode was found to produce distinct electro-oxidation signals for FA ΔEp=300 mV in the presence of sulfite with, which proves its applicability for the determination of FA in the presence of sulfite ions commonly present in food samples (e.g. red wine). The MgO/SWCNTs-[Bmim][Tf2N]-CPE proved to be a powerful tool for the determination of FA and sulfite ions (recovery data between 97.84%-103.1%) in the respective concentration ranges of 0.009–450 µM and 0.1–450 µM with detection limit of 3.0 nM and 50 nM, respectively. In the final step, the MgO/SWCNTs-[Bmim][Tf2N]-CPE was successfully used in the determination of FA and sulfite in food samples.

Determination of Sulfite in Wine Using Differential Pulse Polarography

Sulfite determination plays an important role, since it is used in some food stuff as protecting agent. It is a known fact that higher values of sulfite in foods will create some health problems. Thus, its accurate determination has a vital importance. In this investigation a new and simple DP polarographic method is established for the determination of sulfite. The polarographic peak of sulfite was used for its determination. The polarograms of sulfite were taken in various electrolytes and pH values in the presence or absence of wine in order to find the best working conditions. It was possible to determine 2 × 10–6 M sulfite in pH 4 Hac–NaAc electrolyte. This method is applied to various wines and it was possible to determine the free and bound sulfite. The results obtained were also compared with an iodometric method used in TSE (Turkish standardization Institute).

Novel pararosaniline based optical sensor for the determination of sulfite in food extracts.

Sulfite, which is a protective agent in various food industries, also is known as an allergen. Therefore, sulfite content in food must be monitored and controlled. In this context, a novel optical sensor is designed for simple, rapid and sensitive determination of the sulfite content in food samples. Acidified pararosaniline (PRA) hydrochloride reagent in cationic form was immobilized on the surface of the Nafion cation exchanger membrane by electrostatic interactions. In formaldehyde medium, the pale purple PRA-Nafion film was converted to rich purple due to the highly conjugated alkyl amino sulfonic acid formation in the presence of sulfite and the absorbance change at 588 nm was recorded. The proposed optical sensor gave a linear response in a wide concentration range for sulfite. The limit of detection (LOD) and the limit of quantification (LOQ) values obtained for sulfite were 0.084 and 0.280 ppm SO2 equivalent, respectively. The proposed optical sensor was validated in terms of linearity, additivity, precision and recovery parameters. The sulfite contents obtained for real food extracts were found to be comparable to the conventional iodometric titration results (with the exception of highly colored samples containing reducing agents, where iodometry was shown to exhibit a systematic error while the proposed sensor could measure the true value). The proposed optical sensor is insensitive to positive interferences from turbidity and colored components of the sample. Sulfite determination in a complex food matrix can be performed using the rapid, simple and sensitive PRA-based sensor without a need for pre-treatment.

Exploring the sulfur species in wine by HPLC-ICPMS/MS

The recent development of the inductively coupled plasma tandem mass spectrometry (ICPMS/MS) offers exciting opportunities for non-metal speciation analysis. In this work, we report the first sulfur speciation study in wine by HPLC-ICPMS/MS. The major sulfur compounds were found to be sulfate (50–81 mg S L−1) followed by sulfite (18–24 mg S L−1 free sulfite & 41–63 mg S L−1 after base hydrolysis). We detected small amounts of methionine in wine (0.5–1.0 mg S L−1); Thiosulfate was below the detection limit of 0.1 mg S L−1 (injection volume 1.0 μL). A few unknown compounds (collectively 1.0–2.0 mg S L−1) were observed in the chromatograms. However, the sum of detected species accounted for only 65–77% of total sulfur concentration (105–165 mg S L−1). To investigate this gap between total sulfur and the sum of detected peaks, we performed several chemical treatments of wine including hydrolysis, oxidation, and enzymatic digestion and then re-examined the distribution of sulfur species. Furthermore, we developed a chromatographic method involving the direct determination of sulfite in white and red wine. The recovery was within the range of 98–106% and repeatability (RSD%) in the range of 6.9–9.4% in regular and “sulfite-free” red and white wine. The pH of the mobile phase drastically influenced the chromatographic behavior of the sulfite ion. At neutral pH a significant tailing and a more than 10-fold loss in peak area was observed. This effect was not previously reported and must be taken into consideration when attempting direct chromatography of sulfite.

Development of a Measuring Method for the Determination of Bisulfite and Sulfite in Seawater

AbstractIn conventional reverse osmosis processes for seawater desalination, a disinfection of the process stream with chlorine compounds is carried out for antifouling. After disinfection the reduction agent Na2S2O5 is used for the removal of residual chlorine in a strongly overstoichiometric way in order to protect the membranes from oxidational damages. To save chemicals a controlled dosing of Na2S2O5 based on a reliable concentration measurement is desirable. Therefore, a measuring method for the determination of the sulfur(IV) components bisulfite and sulfite in seawater is developed based on the combination of UV spectroscopy and a PLS regression method. Experimental results as well as the development of the regression model for sulfur species in ultrapure and seawater is described.

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.

Spectrophotometric determination of sulphite and thiamin hydrochloride using proton transfer reaction-application to water sample and pharmaceutical formation

In this research, an easy, acurate and rapid spectrophotometric method for determination of sulphite and thiamine hydrochloride is described. This method used proton transfer reaction between sulphite ion with alizarine at (pH 6.73) to develop red colour adduct that bears maximum absorption at 524 nm. This method was developed to determination of thiamine hydrochloride by bleaching the red colour (alizarine-sulphite product) at the optimum conditions established for the determination of sulphite. Beer’s law is obeyed in the concentration range (10-1000) μg/25ml (0.4-40) of sulphite and 10-1500, μg/25ml (0.4-60) for thiamine hydrochloride at the selected wavelength, the molar absorbtivity 2.6×104 l.mol-1.cm-1 for SO32- and 3.37×104 l.mol-1.cm-1 for thiamine hydrochloride, Sandell's index for sensitivity 0.00307 μg .cm-2 for sulphite and 0.0100 μg .cm-2 for B1, the precision (RSD) of the method is ±0.23- ± 0.51% sulphite and ±0.15- ±0.25 thiamine hydrochloride. Good recoveries of sulphite and thiamine hydrochloride from water samples and pharmaceutical formation are achieved using the proposed method.

A modified screen printed electrode based on La3+-doped Co3O4 nanocubes for determination of sulfite in real samples

A new La3+-doped Co3O4 nanocubes based screen printed electrochemical sensor was effectively used to determine sulfite. The electrochemical oxidation activity of sulfite was considered in PBS (pH 7.0) with voltammetry method. The obtained results presented that the new electrode has an electrocatalytic behavior in oxidizing sulfite resulting in a significant enhancement in its oxidation current. There is a linear correlation between the peak currents and the level of sulfite in the range of 0.7–1000.0 μM with a limit of detection of 0.090 (±0.001) μM. The suggested sensor showed good selectivity, sensitivity and outstanding recovery results for real samples with considerable constancy and precision suggesting practical efficacy of the La3+-doped Co3O4 nanocubes/SPE as an efficient and reliable electrochemical sensor for determining sulfite.

Comparison and optimization of three commercial methods with an LC–MS/MS method for the determination of sulfites in food and beverages

Sulfites are food additives found in a large variety of food products to help reduce oxidation and browning. A small subset of the population has “allergic-like” symptoms upon consumption of sulfite containing foods. There are several sulfite detection methods available in the literature that vary in analysis time and required instrumentation. There are also rapid screening tests available that have not been tested extensively for accuracy and precision. In this study, four different methods (an LC–MS/MS method, a spectrophotometric method, a test strip method and a spot test method) were used to determine the sulfite concentration of 10 different commercially sulfited products. Of these methods, the LC–MS/MS and the spectrophotometric method had the most comparable results. The test strips were only accurate at concentrations greater than 50 mg/kg (ppm) SO2. The spot test method was found to be inaccurate with both standard solutions and samples.

Combination of paper-based thin film microextraction with smartphone-based sensing for sulfite assay in food samples

Herein, a simple, green, and novel paper-based headspace-thin film microextraction in combination with smartphone-based on-cell detection was introduced. Sulfite was selected as a model compound to study the performance of the method. The method was based on converting sulfite to SO2 by acidification of the sample solution. A piece of cellulose paper impregnated with Fe(III), 1,10-phenanthroline, and acetate buffer (pH = 5.5) was used for headspace-thin film microextraction. The sulfur dioxide adsorbed on the thin film reduced Fe(III) to Fe(II). The red color complex formed between Fe(II) and 1,10-phenanthroline was on-cell detected by a smartphone. The effect of various parameters on the method sensitivity was investigated. The method had three individual linear ranges (0.1–1.0, 1–50, and 50–700 µg L−1) with a detection limit of 0.04 µg L−1. The method provided a simple and green assay for the determination of sulfite in food samples. Recoveries were higher than 94% with the relative standard deviations lower than 4.8%. Expensive and complicated facilities were not required in the method.