Simultaneous determination of artificial sweeteners, preservatives, caffeine, theobromine and theophylline in food and pharmaceutical preparations by ion chromatography.

A novel ion chromatographic method was proposed for the simultaneous determination of artificial sweeteners (sodium saccharin, aspartame, acesulfame-K), preservatives (benzoic acid, sorbic acid), caffeine, theobromine and theophylline. The separation was performed on an anion-exchange analytical column operated at 40 degrees C within 45 min by an isocratic elution with 5 mM aqueous NaH2PO4 (pH 8.20) solution containing 4% (v/v) acetonitrile as eluent, and the determination by wavelength-switching ultraviolet absorbance detection. The detection limits (signal-to-noise ratio 3:1) for all analytes were below the sub-microg/ml level. Under the experimental conditions, several organic acids, including citric acid, malic acid, tartaric acid and ascorbic acid, did not interfere with the determination. The method has been successfully applied to the analysis of various food and pharmaceutical preparations, and the average recoveries for real samples ranged from 85 to 104%. The levels of all analytes determined by this method were in good agreement with those obtained by the high-performance liquid chromatographic procedure. The results also indicated that ion chromatography would be possibly a beneficial alternative to conventional high-performance liquid chromatography for the separation and determination of these compounds.     

Simultaneous determination of preservatives,sweeteners and antioxidants in foods by paired-ion liquid chromatography

Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous -hydroxy-isobutyric acid solution (pH 4.5) (2.2 3.4 or 2.4 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C₁₈ column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 g. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and -hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.     

高效液相色谱法同时测定蜜饯中的16种食品添加剂

建立了同时检测蜜饯中16种食品添加剂(安赛蜜、糖精钠、苯甲酸、山梨酸、脱氢乙酸、新红、诱惑红、柠檬黄、苋菜红、胭脂红、日落黄、亮蓝、赤藓红、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯)含量的高效液相色谱法.选用Athena C18-wp色谱柱(4.6 mm×250 mm,5 μm),以0.02mol/L乙酸铵...     

High-performance liquid chromatography utilization of ionic liquids as mobile phase additives for separation and determination of the isomers of amino benzoic acids

For the isomers of amino benzoic acid, including o-, m-, p-amino benzoic acid, the beneficial effects of using the ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF₄]), as mobile phase additives on retention behavior and separation were investigated. Chromatographic separation of the o-, m-, p-amino benzoic acid was performed on a reversed-phase C18 column by ultraviolet detection at 245 nm. The effects of several chromatographic parameters, concentrations and pH values of [BMIm][BF₄] solutions, methanol concentration and length of alkyl chain on different ionic liquids, on the separation and determination of the isomers were evaluated. The optimized chromatographic conditions were established using an aqueous 0.5 μmol/L [BMIm][BF₄] solution (pH 3.0)/methanol (40:60, v/v) as mobile phase without need of gradient elution, with separation of three amino benzoic acids achieved within four min. The calibration curve showed good linearity over the tested range of 2 mg/L to 120 mg/L for the three isomers with a correlation coefficients of 0.9999. The recoveries of the three amino benzoic acids of spiked components were between 99.8% and 100%. The method has been successfully applied to the determination of p-amino benzoic acid in the pharmaceutical, Bromine Mitag Procaine Injection.     

Renewable stationary phase liquid magnetochromatography: determining aspartame and its hydrolysis products in diet soft drinks

A new chromatographic modality that does not require high pressures and also allows renewal of the stationary phase as desired is reported. The technique is based on a thin layer paramagnetic stationary phase (Fe₃O₄–SiO₂) retained on the inner wall of a minicolumn through the action of an external magnetic field, which also plays an important role in separating the analytes. Accordingly, the name “renewable stationary phase liquid magnetochromatography”, or RSP-LMC, has been proposed for it. The technique was used to separate and quantify the sugar substitute α-aspartame and its constituent amino acids (hydrolysis products), L-aspartic acid and L-phenylalanine, in diet fizzy soft drinks. When the results obtained for α-aspartame were compared with those obtained using HPLC as a reference method, no significant differences were observed. The system proposed is fully automated, making it an economic, competitive alternative to conventional methods of determining α-aspartame and its amino acid components.     

Simultaneous determination of some food additives in soft drinks and other liquid foods by flow injection on-line dialysis coupled to high performance liquid chromatography

Flow injection on-line dialysis was developed for sample pretreatment prior to the simultaneous determination of some food additives by high performance liquid chromatography (FID-HPLC). A liquid sample or mixed standard solution (900 μL) was injected into a donor stream (5%, w/v, sucrose) of FID system and was pushed further through a dialysis cell, while an acceptor solution (0.025 mol L⁻¹ phosphate buffer, pH 3.75) was held in the opposite side of the dialysis membrane. The dialysate was then flowed to an injection loop of the HPLC valve, where it was further injected into the HPLC system and analyzed under isocratic reverse-phase HPLC conditions and UV detection (230 nm). The order of elution of five food additives was acesulfame-K, saccharin, caffeine, benzoic acid and sorbic acid, respectively, with the analysis time of 14 min. On-line dialysis and HPLC analysis could be performed in parallel, providing sample throughput of 4.3 h⁻¹. Dialysis efficiencies of five food additives were in ranges of 5-11%. Linear calibration graphs were in ranges of 10-100 mg L⁻¹ for acesulfame-K and saccharin, 10-250 mg L⁻¹ for benzoic acid and 10-500 mg L⁻¹ for caffeine and sorbic acid. Good precisions (RSD < 5%) for all the additives were obtained. The proposed system was applied to soft drink and other liquid food samples. Acceptable percentage recoveries could be obtained by appropriate dilution of the sample before injecting into the system. The developed system has advantages of high degrees of automation for sample pretreatment, i.e., on-line sample separation and dilution and low consumption of chemicals and materials.     

高效液相色谱法同时测定榨菜中的10种食品添加剂

建立了高效液相色谱法直接测定榨菜中的防腐剂、甜味剂、合成着色剂的方法.采用C18柱以甲醇-乙酸按(0.02 mot/L)为流动相,紫外检测波长为230,254 nm,可在25 min内将苯甲酸、山梨酸、脱氮乙酸、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、糖精钠、乙酰磺胺酸钾(安赛蜜)、天门冬酰苯丙胺酸甲酯(阿斯巴甜)、柠檬黄...     

高效液相色谱法同时测定多种食品添加剂

 采用反相高效液相色谱法 ,一次进样、同时测定食品中的人工合成甜味剂 (糖精钠、安赛蜜、甜味素 )、防腐剂(苯甲酸、山梨酸 )、咖啡因、可可碱和茶碱。以AlltechEconosphereC18柱 (15 0mm× 4 6mmi.d .,3μm)为分离柱 ,10mmol/LNaH2 PO4 (pH 4 0 0 ) 乙腈 (体积比为 90∶10 )为流动相 ,采用二极管阵列检测器进行检测。整个分离过程在 2 3min内完成。样品平均加标回收率为 78 5 %～ 10 7 2 %。     

HPLC法同时测定黄酒中4种非法食品添加剂

建立高效液相色谱同时测定黄酒中安赛蜜、苯甲酸、山梨酸和糖精钠4种非法食品添加剂的方法。黄酒中的待测物质经提取后,采用C18柱分离,以甲醇–乙酸铵溶液为流动相进行洗脱,在波长230 nm处用高效液相色谱–二极管阵列检测器进行测定。安赛蜜、苯甲酸、山梨酸和糖精钠的质量浓度在0.5～200.0μg/mL范围内与其色谱峰面积的线性关系良好(r0.999 7),检出限为0.29～0.74μg/L。在0.5,1.0,2.5,5.0,7.5 mg添加水平时的平均回收率在95.6%～104.0%范围内,测定结果的相对标准偏差为0.3%～1.5%(n=6)。该方法操作简便,分离效果好,灵敏度高,结果稳定可靠,适合于黄酒中安赛蜜、苯甲酸、山梨酸和糖精钠的同时测定。     

MLC Determination of Preservatives in Cranberry Foodstuffs

Optimized conditions for the determination of 14 food preservatives were selected by using interpretative optimization strategy and Derringer’s desirability function for combining three main chromatographic goals: resolution, separation time and ruggedness. The best mobile phase for separation by micellar liquid chromatography contains 0.045 M SDS and 1.0% (v/v) 1-pentanol at pH 2.5 adjusted with trichloroacetic acid. The accuracy of the method was confirmed by analysis of spiked samples and is useful for routine analysis of food preservatives in drinks due to simple sample preparation, safety and low cost of micellar mobile phases. Presented in part by A.P. Boichenko at the 4th Black Sea Basin Conference on Analytical Chemistry, 19–23 September, 2007, Sunny Beach, Bulgaria.     

Effects of ionic liquid as additive and the pH of the mobile phase on the retention factors of amino benzoic acids in RP-HPLC

As an organic salt, ionic liquids are widely used as new solvent media. In this paper, three positional isomers, such as o-amino benzoic acid, m-amino benzoic acid, and p-amino benzoic acid are separated with four different ionic liquids as additives to the mobile phase using reversed-phase (RP) high-performance liquid chromatography (HPLC). Amino benzoic acids are biologically active substances; the p-isomer is present in a group of water-soluble vitamins and is widely known as a sunscreen agent. The ionic liquids used are 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium methylsulfate, and 1-octyl-3-methylimidazolium methylsulfate. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of the ionic liquid, and the effect of the pH of the mobile phase on the retention factor of the amino benzoic acid isomers are studied. Separation with the ionic liquid in the eluent was better than the separation without the ionic liquid. The pH mainly affected the retention and elution order of the solutes in RP-HPLC.     

HPLC behavior and hydrophobic parameters of some anilides

Summary The chromatographic behavior ofpara substituted anilides of 2,2-dimethylpropanoic, benzoic and α-phenyl acetic acid has been studied by reversed-phase high performance liquid chromatography. HPLC was performed on a C-18 column with various aqueous methanol mobile phases. The influence on the retention of anilide type and additional substituents in the molecule is discussed. Several chromatographic hydrophobicity parameters (CHP) have been calculated by linear correlation between logk of the investigated compounds and the concentration of methanol in the mobile phase. The chromatographic hydrophobicity parameters were compared with the logP values calculated by Rekker's fragmental method. The results show moderate correlations of CHP with logP. Thus, multiple linear regressions have been applied. It was found that besides logP even the electronic effects of individual polar groups capable of hydrogen bonding proced to be very important in hydrophobic characterization of the molecule.     

Simultaneous determination of fangchinoline and tetrandrine in Stephania tetrandra S. Moore by using 1-alkyl-3-methylimidazolium-based ionic liquids as the RP-HPLC mobile phase additives

A reversed phase high performance liquid chromatography (RP-HPLC) method for simultaneous determination of fangchinoline (FAN) and tetrandrine (TET) in Stephania tetrandra S. Moore was established by using 1-hexyl-3-methylimidazolium tetrafluoroborate as the mobile phase additives in this paper. Four types of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) were used as additives of the mobile phase to separate FAN and TET by RP-HPLC. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of IL and the pH of the mobile phase, which influenced the chromatographic behaviors of FAN and TET, were investigated in detail. The linearity, sensitivity, accuracy and repeatability of the proposed method were also investigated. The probable mechanism of the separation with ILs as the mobile phase additives was explored and discussed.     

Use of the Synthesized Titania Monolith to Determine Benzoic Acid and Vanillin in Foodstuffs by HPLC

A simple and reliable HPLC method for the determination of benzoic acid and vanillin in food samples has been developed, in which a pure titania monolithic column synthesized through a template-free sol-gel synthesis route was used as chromatography column. To fully understand the retention mechanism of benzoic acid and vanillin on titania, acetonitrile (ACN) percentage, buffer concentration, and buffer pH of the mobile phase were investigated. The retention mechanism of benzoic acid and vanillin on the titania monolith column belongs to hydrophilic interaction and ligand exchange. When the high %ACN and appropriate acetate existed in eluent, the hydrophilic interaction was the dominant retention mode. Benzoic acid and vanillin in preserved fruit and jelly samples were successfully determined and quantitative analysis was carried out by external standard method with correlation coefficient (R ² ) of 0.9994 for benzoic acid and 0.9989 for vanillin. The relative standard deviations (RSDs) of benzoic acid and vanillin were 0.94% and 1.50%, respectively. The developed titania-based HPLC method is simple, rapid, accurate, and competent for the separation of polar and hydrophilic compounds, and this work has also promoted the application of titania monolith in chromatographic separation.     

高效液相色谱法同时测定肉制品中的6种食品添加剂

建立了同时测定肉制品中化学性质差异较大的6种常用食品添加剂的高效液相色谱(HPLC)分析方法。根据6种添加剂(苯甲酸(钠)、山梨酸(钾)、糖精钠、安赛蜜、诱惑红和胭脂红)的化学性质,对HPLC分析条件进行了详细的优化。结果表明:以ZORBAX Eclipse Plus C18柱(150mm×4.6mm,5μm)为分析柱,以甲醇和20mmol/L醋酸铵溶液(pH为6.9)为流动相进行梯度洗脱,在235nm波长下进行检测,可以在18min内完成6种添加剂的同时测定。在高、低两个加标浓度下,样品的回收率为80.7%～94.4%,相对标准偏差(n=3)为2.0%～7.1%。结果表明,该方法快速、准确,能够同时分析测定肉制品中上述6种食品添加剂。     

高效液相色谱法同时测定食品中的8种添加剂

建立高效液相色谱法同时测定食品中的安赛蜜、苯甲酸、山梨酸、苋菜红、脱氢乙酸、胭脂红、日落黄、诱惑红8种添加剂。样品采用Agilent zorbax sb–C_(18)色谱柱梯度洗脱,紫外检测器检测,外标法定量分析。结果表明,8种添加剂的质量浓度在0.5~20μg/m L范围内与其色谱峰面积线性关系良好,相关系数均大于0.999,方法检出限为0.06~0.18 mg/kg。样品的加标回收率为91.3%~101.1%,测定结果的相对偏差为0.47%~1.35%(n=6)。该方法操作简单,灵敏度高,结果准确可靠,适用于食品添加剂的常规分析。     

A new method of thin-layer chromatography with controlled vapor phase

A new version of thin-layer chromatography with controlled vapor phase is described. It has no analogues in planar and liquid chromatography. The method is based on a dynamic change in the physicochemical properties of a chromatographic system as a result of the contact of the plate bearing analytes with a vapor phase of certain composition created in the chromatographic chamber. The active vapor phase is created either by pumping a gas through the chromatographic chamber or by introducing a solvent vapor from another part of the chamber. The composition and properties of the mobile phase are controlled immediately in the course of separation by means of absorption or adsorption of one or another gas with the mobile or stationary phase. By the examples of benzoic acids and nitroaniline isomers in the presence of carbon oxide and vapors of acetic acid, ammonia, and ethanol, it was shown that this procedure utilizes the difference in the protolytic and solvation properties of adsorbates for changing the adsorption equilibrium and the selectivity and efficiency of separation.     

Ionic liquids as mobile phase additives for determination of thiocyanate and iodide by liquid chromatography

An analytical method was developed for the simultaneous determination of thiocyanate and iodide by reversed‐phase liquid chromatography with UV detection using imidazolium ionic liquids as mobile phase additives. The chromatographic behaviors of the two anions on a C₁₈ column were studied and compared with four types of reagents including imidazolium ionic liquids, pyridinium ionic liquids, 4‐aminophenol hydrochloride and tetrabutylammonium as mobile phase additives. The effects of the concentrations of imidazolium ionic liquids, organic solvents and detection wavelength on separation and detection of the anions were investigated. The role of ionic liquids, retention rules and mechanisms were discussed. The separation of the anions was performed on the C₁₈ reserved‐phase column using acetonitrile‐0.3 mmol/L 1‐amyl‐3‐methylimidazolium tetrafluoroborate (10:90, v/v) as mobile phase, with column temperature of 35°C, flow rate of 1 mL/min and detection wavelength of 210 nm. Under these conditions, the two anions can be completely separated within 6 min. The limits of detection were 0.05 mg/L. The method was applied for the determination of thiocyanate and iodide in ionic liquid samples and iodide drugs, and the spiked recoveries ranged from 97 to 101%. The method is simple, accurate and meets the requirements of quantitative analysis for thiocyanate and iodide.     

Simultaneous determination of antioxidants, preservatives and sweeteners permitted as additives in food by mixed micellar electrokinetic chromatography.

A micellar electrokinetic chromatography method was developed to simultaneously analyse commonly used food additives. The additive mixture, comprising propyl gallate, octyl gallate, dodecyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid ethyl ester, benzoic acid, sorbic acid, saccharin, aspartame and acesulfame-K, was not resolved using single surfactant micellar systems consisting of sodium dodecyl sulfate (SDS), sodium cholate (SC) or sodium deoxycholate (SDC). The separation of these additives using mixed micellar systems, involving SDS/SC, SDS/SDC and SC/SDC, was investigated. Organic solvents were added to the mixed micellar phases to optimise the separation. The mixture was successfully separated using a 20 mM borate buffer with 35 mM SC, 15 mM SDS and 10% methanol added at pH 9.3. Additives in cola beverages and low-joule jam were investigated and quantified using this method.     

High performance liquid chromatographic separation of cholesterol oxidation products

Summary A fast, sensitive, high performance liquid chromatographic method for the simultaneous determination of cholesterol hydroperoxides and other major oxysterols, using two different detection systems (ultraviolet at 210 nm and light scattering), is here described. The hydroperoxy derivatives were obtained by cholesterol photoxidation, isolated by thin layer chromatography and joined with a standard mixture of 10 oxysterols (epoxy, hydroxy and keto derivatives). Aliquots were directly injected onto a 5-μm particle size, 25×0.46 cm i.d. Spherisorb S5 CN normal phase column, usingn-hexane/anhydrous ethanol (97:3, v/v) as mobile phase and a flow rate of 0.8 mL min⁻¹. This method allowed, in a single isocratic analysis, the separation and quantification of the primary and secondary cholesterol oxidation products in 30 minutes. The light scattering detector was particularly useful for the determination of nonderivatized 5,6-epoxides and cholestane-3β,5α,6β-triol. The sensitivity of both detectors was very similar for most of the oxysterols, except for the 5,6-epoxides and the 7-ketocholesterol. The method suitability for the determination of cholesterol oxidation products in food matrices was successfully tested on a saponified lipid extract from egg yolk powder.