固相萃取-柱后衍生-反相高效液相色谱法测定脱水蒜粉中的亚硫酸盐

建立了测定脱水蒜粉中亚硫酸盐含量的柱后衍生-反相高效液相色谱分析方法.样品用HCl/甘露醇缓冲溶液提取,经固相萃取(SPE)小柱净化本底并富集待测物后,与甲醛缓冲液反应生成稳定的化合物羟甲基磺酸盐,采用高效液相色谱柱及柱后衍生分离,紫外检测器检测,外标法定量.色谱柱为:Agila Venusil MP-C18(4.6 mm×250 mm),流动相为0.005 mol/L四丁基氢氧化铵离子溶液(pH 4),检测波长为450 nm,结果表明,检出限为2.0 mg/kg,在0.1～10.0 μg/mL范围内线性关系良好,相关系数R2=0.9998,样品添加回收率为86.5%～97.6%,RSD为2.2%～4.0%(n=5).     

Determination of added sulfites in dried garlic with a modified version of the optimized Monier-Williams method

The optimized Monier-Williams method is slightly modified so that it could be applied for determining sulfite content in dried garlic. Dried garlic sample is directly acidified in a reactor at a pH below 3. At this pH level, the alliinase enzyme activity is irreversibly blocked, and the sulfur-containing amino acids such as alliin (the most abundant) present in dried garlic cannot be transformed into corresponding thiosulfinates such as allicin, which is absent in dried garlic. This prevents allicin from reacting with added sulfites and being probably converted to S-allyl thiosulfate, which is not volatile and has no taste. It is found that at a pH below 2.4 and at boiling water temperature, allicin produces sulfur dioxide in adequate quantity to explain the false-positive results when utilizing the optimized Monier-Williams method with allicin suppression for unsulfited dried garlic samples. Finally, when garlic samples are stabilized in a phosphoric acid buffer at a final pH around 2.4, no sulfite is produced during the Monier-Williams distillation, which is further proof there are no naturally occurring sulfites in unsulfited dried garlic under these mild conditions.     

Determination of sulfite in Oriental herbal medicines

Sulfite was detected in 7 varieties of Oriental herbal medicines (Pueraria radix, Zingiberis rhizoma, Platycodon radix, Adenophora radix, Pinellia tuber, Astragalus radix, and Paeonia radix) on the Korean market. Sulfiting of commercial Oriental herbal medicines by fumigation with burning bituminous coal was simulated, and the accumulation of sulfite was investigated by using fresh Platycodon radix roots obtained from a growing field. The sulfite level reached a plateau in 9 h, and the maximum sulfite level found by the Monier-Williams (MW) method (AOAC 990.28) was 1020 ppm. The sulfite content in the simulated Platycodon radix sample determined by alkali extraction followed by ion-exclusion chromatography with electrochemical detection (AOAC 990.31) was approximately 17% lower on average than the MW results. Free-sulfite levels determined by acid extraction and ion-exclusion chromatography with electrochemical detection were between 19 and 49% of the MW results. The advantages of different methods for sulfite determination and the significance of the results are discussed.     

高效液相色谱柱后衍生测定脱水蔬菜中的亚硫酸盐

建立了检测脱水蔬菜中亚硫酸盐的反相硅胶柱净化-柱后衍生-高效液相色谱方法.样品经甲醛提取,通过反相硅胶固相萃取小柱净化,采用Discover ODS-C18柱,流动相为0.005 mol/L氢氧化四丁基铵和乙腈,在碱性条件下以5,5’-二硫代双(2-硝基苯甲酸)为柱后衍生化试剂,445 nm检测.实验结果表明,在0.050～50.00 mg/L浓度范围内,相关系数为0.9987,方法的检出限和定量限分别为1 mg/kg和2 mg/kg,添加浓度在2～900mg/kg范围内,平均添加回收率为62％～88％,相对标准偏差不大于7.8％.该法能有效地避免脱水蔬菜中亚硫酸盐测定的假阳性结果,可满足实际检测工作的需要.     

Determination of trace amounts of formaldehyde in acetone

A method to quantify sub-ppm levels of formaldehyde in acetone has been developed and it is reported here. In this method, the different reactivities and stabilities of sulfite with formaldehyde and acetone are used to separate the two carbonyl compounds. Sulfite reacts with formaldehyde to form hydroxymethanesulfonate (HMS), the non-volatile and stable nature of which allows its separation from bulk acetone solvent. The resulting HMS is then converted back to formaldehyde under basic conditions, and formaldehyde is derivatized with 2,4-dinitrophenylhydrazine (DNPH) and quantified in its DNP hydrazone form using high-performance liquid chromatography-UV detection. The method detection limit at the 99% confidence level was 0.051 mg L⁻¹. A batch of samples can be processed within 4 h. The method has been applied to quantify the amount of formaldehyde in an analytical-grade acetone and in a commercial nail polish remover and the level of formaldehyde was found to be 0.175 and 0.184 mg L⁻¹, respectively.     

Direct, sensitive and selective detection of free fatty acids by high-performance liquid chromatography with post-column ion-pair extraction and absorbance detection

Free fatty acids (C8-C18) are separated by reversed-phase liquid chromatography and detected using a simple post-column dynamic extraction system in which the acids are extracted as ion pairs with chloroform from the aqueous acetonitrile (gradient: 79-99% acetonitrile) mobile phase after the post-column addition of aqueous Methylene Blue solution. The chloroform phase containing the ion pairs is monitored with an absorbance detector at 651 nm. The detection limits ranged from 26 to 83 ng, depending upon the acid, with coefficients of variation of 1.2-14%. Application of the method to butter and margarine samples permitted detection of free fatty acids down to 35 ppm and in orange juice, down to 0.5 ppm using only an organic solvent extraction without further sample clean-up for isolation of the fatty acids.     

Determination of sulfite with emphasis on biosensing methods: a review

Sulfite is used as a preservative in a variety of food and pharmaceutical industries to inhibit enzymatic and nonenzymatic browning and in brewing industries as an antibacterial and antioxidizing agent. Convenient and reproducible analytical methods employing sulfite oxidase are an attractive alternative to conventional detection methods. Sulfite biosensors are based on measurement of either O₂ or electrons generated from splitting of H₂O₂ or heat released during oxidation of sulfite by immobilized sulfite oxidase. Sulfite biosensors can be grouped into 12 classes. They work optimally within 2 to 900 s, between pH 6.5 and 9.0, 25 and 40 °C, and in the range from 0 to 50,000 μM, with detection limit between 0.2 and 200 μM. Sulfite biosensors measure sulfite in food, beverages, and water and can be reused 100–300 times over a period of 1–240 days. The review presents the principles, merits, and demerits of various analytical methods for determination of sulfite, with special emphasis on sulfite biosensors.     

Spectrophotometric Flow Injection Analysis of Sulfite and Formaldehyde In Aqueous Micellar Medium Using 5,5′-Dithiobis(2-Nitrobenzoic Acid)

Abstract

Aqueous sulfite and formaldehyde were quantitated in the nanomole range using the reaction of 5,5′-dithiobis(2-nitrobenzoic acid), DTNB, with sulfite. Cationic micelles were used and found to greatly increase the sensitivity, bathochromically shifting the absorption spectra as well as lowering the pK of the reaction. the method was adapted to flow injection analysis, allowing more than 100 samples to be analyzed per hour with a relative standard deviation of less than 1.5% in all cases studied. the method is simple, fast and more sensitive than any available methods. the great flexibility of the choice of pH, surfactant concentration and buffer concentration contributes much to the high precision that could be achieved.     

Development and validation of a glass-silicon microdroplet-based system to measure sulfite concentrations in beverages

Sulfite is often added to beverages as an antioxidant and antimicrobial agent. In fermented beverages, sulfite is also naturally produced by yeast cells. However, sulfite causes adverse health effects in asthmatic patients and accurate measurement of the sulfite concentration is therefore very important. Current sulfite analysis methods are time- and reagent-consuming and often require costly equipment. Here, we present a system allowing sensitive, ultralow-volume sulfite measurements based on a reusable glass-silicon microdroplet platform on which microdroplet generation, addition of enzymes through chemical-induced emulsion destabilization and pillar-induced droplet merging, emulsion restabilization, droplet incubation, and fluorescence measurements are integrated. In a first step, we developed and verified a fluorescence-based enzymatic assay for sulfite by measuring its analytical performance (LOD, LOQ, the dynamic working range, and the influence of salts, colorant, and sugars) and comparing fluorescent microplate readouts of fermentation samples with standard colorimetric measurements using the 5,5′-dithiobis-(2-nitrobenzoic acid) assay of the standard Gallery Plus Beermaster analysis platform. Next, samples were analyzed on the microdroplet platform, which also showed good correlation with the standard colorimetric analysis. Although the presented platform does not allow stable reinjection of droplets due to the presence of a tight array of micropillars at the fluidics entrances to prevent channel clogging by dust, removing the pillars, and integrating miniaturized pumps and optics in a future design would allow to use this platform for high-throughput, automated, and portable screening of microbes, plant, or mammalian cells.

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In vivo role of sulfite in photocontrol of urocanase from Pseudomonas putida

Abstract— Urocanase from Pseudomonas putida becomes inactive in growing and resting cells and is activated by UV radiation. Sulfite addition to the bound nicotinamide adenine dinucleotide coenzyme has previously been shown to inactivate the enzyme in vitro. The enzyme released sulfite upon photoactivation. Whether sulfite addition and dissociation is involved in the in vivo photoregulation of urocanase was examined in this study. The dark reversion (inactivation) in cultures was markedly enhanced by growth at 32°C rather than at 24°C; cells grown at 32°C and resting cells were used to obtain in Wvo-inactivated urocanase. We purified the in vivo-inactivated enzyme and quantitated the amount of sulfite released through photodissociation. One mole of sulfite was released per mole of urocanase. This is based on a molecular weight of 110000 confirmed by gel electrophoresis and a protein estimation method validated by our data. Our previous report of sulfide inactivation of urocanase in vitro is now shown to have been mistaken; the inactivation resulted from the oxidation of sulfide to sulfite, which occurred in solution.     

Substituierte Alkylsulfonate durch Addition von Natriumhydrogensulfit an Chalkone

Substituted Alkyl Sulfonates by Addition of Sodium Hydrogen Sulfite to Chalcones Sodium hydrogen sulfite adds to the C, C double bond of chalcones to give substituted alkyl sulfonates 1. Reaction of methyl iodide with the pyridyl substituted alkyl sulfonates 1b–1e yields the inner salts 2–4 .     

Direct determination of sulfite in food samples by a biosensor based on plant tissue homogenate

In the work described here, a biosensor was developed for the determination of sulfite in food. Malva vulgaris tissue homogenate containing sulfite oxidase enzyme was used as the biological material. M. vulgaris tissue homogenate was crosslinked with gelatin using glutaraldehyde and fixed on a pretreated Teflon membrane. Sulfite was enzymatically converted to sulfate in the presence of the dissolved oxygen, which was monitored amperometrically. Sulfite determination was carried out by standard curves, which were obtained by the measurement of consumed oxygen level related to sulfite concentration. Several operational parameters had been investigated: the amounts of plant tissue homogenate and gelatin, percentage of glutaraldehyde, optimum pH and temperature. Also, some characterization studies were done. There was linearity in the range between 0.2 and 1.8 mM at 35 °C and pH 7.5. The results of real sample analysis obtained with the biosensor agreed well with the enzymatic reference method using spectrophotometric detection.     

Flow Injection Analysis of Hydrogen Peroxide,Sulfite, Formaldehyde and Hydroxymethanesulfonic Acid in Precipitation Samples

Abstract

Hydroxymethanesulfonic acid (HMSA), the reaction product of sulfite and formaldehyde plays an important part in the aqueous phase conversion of sulfite to sulfate. HMSA is fairly stable under acidic conditions and in presence of hydrogen peroxide. Sulfite is unstable under these conditions.

A flow injection set-up was developed, which allows the determination of H₂O₂, sulfite, formaldehyde and hydroxymethanesulfonic acid.

H₂O₂ analysis by amperometric detection offers the possibility of a simple, robust field instrument. The detection limit is 5μg/l and the method is linear up to 5mg/l.

Based on the 4,4-dithiodipyridine/sulfite reaction selective and sensitive spectrophotometric detections were developed for sulfite, formaldehyde and hydroxymethanesulfonic acid. The detection limit of these compounds is 50μg/l and the method is linear up to 5mg/l.

A large fraction of S(IV) is present as HMSA in fog, dew and precipitation samples in The Netherlands.     

New Spectrophotometric Method for Sulfite Determination

Abstract

A highly selective spectrophotometric method for the determination of aqueous sulfite was developed. Sulfite was found to react with o-phthaldialdehyde in presence of ammonia yielding a deep blue colored complex the absorbance of which is sensitive to trace sulfite concentrations. The method is simple, very sensitive, and convenient for the determination of as little as 5X10^?6 M sulfite. The molar absorptivity of the colored complex is about 1.2X10⁴ L cm^?1 mol^?1. The proposed method is more sensitive and selective for sulfite than the widely used Ellman reagent method. Absorbance is measured at 628 nm which is the best of the two absorption maxima that are exhibited by the compound.     

Determination of phenol in the presence of sulfite (sulfur dioxide) by the 4-aminoantipyrine spectro-photometric method

The interference of sulfite (sulfur dioxide) with the 4-aminoantipyrine (4-AAP) spectrophotometric method for phenol is discussed for procedures without distillation, and with distillation in the absence and presence of copper(II) sulfate. Sulfite represses the color development in all these procedures. Without chloroform extraction, the maximum tolerable amounts of sulfite in the procedures without distillation, distillation without copper(II) sulfate, and distillation with copper(II) sulfate are 15, 10, and 20 mg/100 ml, respectively. For the extraction method, the limits are 4.0, 4.0, and 10 mg/ 100 ml, respectively. Copprer(II) sulfate catalyzes the air-oxidation of sulfite. Phenol can be determined in the presence of large amounts of sulfite by treating with sulfide to form polythionates and thiosulfate; excess of sulfide is removed with copper(II) sulfate, sulfuric acid is added, the phenol is distilled, and the 4-AAP method is applied. Improvements are made in the overall accuracy of the 4-AAP method.     

Amperometric determination of sulfite with sulfite oxidase immobilized at a platinum electrode surface

Sulfite oxidase is immobilized on collagen membrane at the surface of a platinum electrode and catalyzes the oxidation of sulfite to sulfate with stoichiometric production of hydrogen peroxide. The hydrogen peroxide is detected amperometically at the platinum electrode at an applied potential of 700 mV. The system responds linearly to sulfite in the range 1–150 μM, with a detection limit of 0.2 μM. The enzyme retains over 95% of its activity for three weeks if stored at ?20° C when the probe is not in use.     

Real-time quantification for sulfite using a turn-on NIR fluorescent probe equipped with a portable fluorescence detector

Sulfur dioxide and its derivative sulfite widely existed in air, water as the environment pollutant. Sulfite is also commonly used as preservative and additive in fresh fruits, vegetables, wines and pharmaceutical materials. Due to sulfite is closely related with human diseases, it is very urgent for the sensitive and rapid quantification of sulfite in various samples. In our study, a turn-on near infrared (NIR) fluorescent probe (MDQ) was developed for sulfite detection based on a Michael addition reaction, with high sensitivity (LOD 4.16 nmol/L), selectivity and fast response time (400 s). Using MDQ, a quantify method for sulfite in traditional Chinese medicines (TCMs) was developed with the advantages of high precision, accuracy and convenient operation. Furthermore, according to the photophysical property of MDQ, a portable fluorescence detector is designed to quantify sulfite for TCMs and surface water in Dalian city of China. Therefore, the developed fluorescent probe MDQ and portable fluorescent detector as a rapid inspection instrument were successfully used to real-time monitor the sulfite in various complex samples.     

Uniformly sized molecularly imprinted polymer for d-chlorpheniramine. Evaluation of retention and molecular recognition properties in an aqueous mobile phase

Rapid separation and determination of mixtures of L-ascorbic acid, nitrite, sulfite, oxalate, iodide and thiosulfate by conventional ion chromatography is often difficult due to incomplete separation of L-ascorbic acid and nitrite from the water peak when using eluents giving short elution times for iodide and thiosulfate. Separation of the six species within about 15 min has been achieved by isocratic elution using a resin-based ion-exchange column with a carbonate eluent containing a trace amount of 1,3,5-benzenetricarboxylic acid (BTA) and fluorescence measurement of cerium(III) formed via postcolumn reactions of the separated sample species with cerium(IV). Calibration plots of peak height versus concentration were linear up to 10.0 microM (1.76 ppm) for L-ascorbic acid, 8.0 microM (0.37 ppm) for nitrite, 8.0 microM (0.70 ppm) for oxalate, 80.0 microM (10.2 ppm) for iodide and 25.0 microM (2.80 ppm) for thiosulfate, whilst the sulfite calibration was linear up to 25.0 microM (2.00 ppm) when peak area was plotted against concentration. Detection limits (defined as S/N = 3) were 18 ppb for L-ascorbic acid, 4 ppb for nitrite, 16 ppb for sulfite, 7 ppb for oxalate, 72 ppb for iodide and 37 ppb for thiosulfate. The proposed method was applied successfully to the determination of L-ascorbic acid, nitrite, sulfite, oxalate, iodide or thiosulfate in water samples.     

Determination of biothiols by a novel on-line HPLC-DTNB assay with post-column detection

A novel on-line HPLC-DTNB method was developed for the selective determination of biologically important thiols (biothiols) such as l-cysteine (Cys), glutathione (GSH), homocysteine (HCys), N-acetylcysteine (NAC), and 1,4-dithioerythritol (DTE) in pharmaceuticals and tissue homogenates. The biothiols were separated on C18 column using gradient elution, reacted with the postcolumn reagent, DTNB in 0.5% M-β-CD (w/v) solution at pH 8, to form yellow-colored 5-thio-2-nitrobenzoic acid (TNB), and monitored with a PDA detector (λ = 410 nm). With the optimized conditions for chromatography and the post-column derivatization, 40 nM of NAC, 40 nM of Cys, and 50 nM of GSH can be determined. The relative standard deviations of the recommended method were in the range of 3.2–5.4% for 50 μM biothiols. The negative peaks of biothiol constituents were monitored by measuring the increase in absorbance due to TNB chromophore. The detection limits of biothiols at 410 nm (in the range of 0.04–0.58 μM) after post-column derivatization with DTNB + M-β-CD were much lower than those at 205 nm UV-detection without derivatization, and were distinctly lower than those with post-column DTNB alone. The method is rapid, inexpensive, versatile, nonlaborious, uses stable reagents, and enables the on-line qualitative and quantitative estimation of biothiol constituents of biological fluids and pharmaceuticals.     

新型WO3/HMS催化剂的制备及其对环戊烯选择氧化反应的催化性能

 采用草酸络合方法将WO3固载到六方介孔全硅分子筛HMS上,制得新型WO3/HMS非均相催化剂. 利用SEM,TEM,N2吸附,XRD及激光拉曼光谱等手段对催化剂进行了表征,研究了催化剂在环戊烯选择性氧化合成戊二醛反应中的催化性能. 结果表明,在WO3/HMS催化下环戊烯和H2O2的转化率均可达100%,戊二醛的选择性可达72%. WO3以高分散状态存在于催化剂表面. 单次反应后钨的溶脱量(5.5 μg/ml)很小,对反应几乎没有影响. 催化剂具有较高的稳定性,可以重复套用6次. 失活后的催化剂可通过简单焙烧的方式再生.