Rapid high-performance liquid chromatography method for the analysis of sodium benzoate and potassium sorbate in foods

A rapid and reliable method is presented for the determination of the preservatives sodium benzoate and potassium sorbate in fruit juices, sodas, soy sauce, ketchup, peanut butter, cream cheese, and other foods. The procedure utilizes high-performance liquid chromatography (HPLC) followed by UV diode array detection for identification and quantitation of the two preservatives. Liquid samples were prepared by diluting 1 ml of the sample with 10 ml of an acetonitrile/ammonium acetate buffer solution. Samples of viscous or solid foods were prepared by blending the sample with the same buffer solution in a 1:5 ratio followed by a dilution identical to liquid samples. All samples were filtered to remove particulate matter prior to analysis. The HPLC determination of the preservatives was performed using a reversed-phase C18 column and UV detection at 225 nm for sodium benzoate and 255 nm potassium sorbate. The percentage of preservative in the sample was calculated by external standard using authentic sodium benzoate and potassium sorbate. Apple juice, apple sauce, soy sauce, and peanut butter, spiked at 0.10 and 0.050% for both sodium benzoate and potassium sorbate, yielded recoveries ranging from 82 to 96%. The method can detect 0.0010% (10 mg/l) of either preservative in a juice matrix.     

Poly(styrene‐co‐N‐methacryloyl‐l‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles as sorbents for the analysis of sodium benzoate in beverages

In this study, poly(styrene‐co‐N‐methacryloyl‐l ‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles were constructed and used as magnetic solid‐phase extraction sorbents for analysis of food preservatives in beverages. To prepare the poly(amino acid)‐based sorbents, N‐methacryloyl‐l ‐phenylalanine methyl ester, and styrene served as the functional monomers and modified onto the magnetic nanoparticles via free radical polymerization. Interestingly, compared with propylparaben and potassium sorbate, the proposed poly(amino acid)‐based sorbents showed a good selectivity to sodium benzoate. The adsorption capacity of the sorbents to sodium benzoate was 6.08 ± 0.31 mg/g. Moreover, the fast adsorption equilibrium could be reached within 5 min. Further, the resultant poly(amino acid)‐based sorbents were applied in the analysis of sodium benzoate in real beverage samples. The results proved that the proposed magnetic solid‐phase extraction sorbents have a great potential for the analysis of preservatives in food samples.     

UPLC-PDAD Analysis for Simultaneous Determination of Ten Synthetic Preservatives in Foodstuff

A novel and quick ultra performance liquid chromatography-photo diode array detector method has been developed and validated for the simultaneous determination of ten synthetic preservatives in foodstuff. An Acquity BEH C18 column (50 × 2.1 mm i.d., 1.7 μm particle size) was used. The mobile phase consisted of a mixture of acetonitrile and 20 mM potassium dihydrogen phosphate/phosphoric acid (pH 4.29) buffer at the gradient elution program. The ten compounds behaved linearly in the 0.100–20.0 μg mL^?1 concentration range, with correlation coefficient >0.999. The precision inter- and intra-day of the ten synthetic preservatives at three concentration levels were 0.11–5.75% (RSD). The recoveries at three different concentrations were 88.7–99.0%, with coefficients of variation <6.3%. The method was applied to the determination of preservatives in cola beverages, fruit-flavoured carbonate beverages and fruit juice beverages, and proved its suitability for quick and reliable quality control.     

基于金属有机骨架材料的磁固相萃取与高效液相色谱-紫外检测法分析饮料和方便面中4种防腐剂

通过简单的搅拌共混方式制备了磁性氨基功能化的金属有机骨架化合物（MOFs）材料,得到的复合材料磁性和热稳定性良好,比表面积大,被用于不同极性防腐剂（苯甲酸、山梨酸、对羟基苯甲酸丙酯和对羟基苯甲酸丁酯）的萃取。优化磁固相萃取及解吸条件后,将解吸液引入高效液相色谱-紫外检测分析仪器,采用Purospher^® STAR LP C18色谱柱（250 mm×4.6 mm,5 μm）分离,以甲醇-10 mmol/L醋酸铵水溶液（50：50,v/v）为流动相进行梯度洗脱。结果表明,目标防腐剂的检出限为0.51~1.89 μg/L;苏打水、维生素饮料和方便面面饼中目标防腐剂的加标回收率为72.2%~109%。该方法简单快速,准确可靠,适用于饮料和食品中不同极性防腐剂的分析,为食品安全及质量监控提供了有效的技术有段。     

Determination of sorbate and benzoate in beverage samples by capillary electrophoresis-Optimization of the method with inspection of ionic mobilities

The aim of this study was to develop a fast capillary electrophoresis method for the determination of benzoate and sorbate ions in commercial beverages. In the method development the pH and constituents of the background electrolyte were selected using the effective mobility versus pH curves. As the high resolution obtained experimentally for sorbate and benzoate in the studies presented in the literature is not in agreement with that expected from the ionic mobility values published, a procedure to determine these values was carried out. The salicylate ion was used as the internal standard. The background electrolyte was composed of 25mmolL(-1) tris(hydroxymethyl)aminomethane and 12.5mmolL(-1) 2-hydroxyisobutyric acid, at pH 8.1. Separation was conducted in a fused-silica capillary (32cm total length and 8.5cm effective length, 50mum I.D.), with short-end injection configuration and direct UV detection at 200nm for benzoate and salicylate and 254nm for sorbate ions. The run time was only 28s. A few figures of merit of the proposed method include: good linearity (R(2)>0.999), limit of detection of 0.9 and 0.3mgL(-1) for benzoate and sorbate, respectively, inter-day precision better than 2.7% (n=9) and recovery in the range 97.9-105%. Beverage samples were prepared by simple dilution with deionized water (1:11, v/v). Concentrations in the range of 197-401mgL(-1) for benzoate and 28-144mgL(-1) for sorbate were found in soft drinks and tea.     

A Weak Cation-Exchange Monolithic SPE Column for Extraction and Analysis of Caffeine and Theophylline in Human Urine

A weak cation-exchange monolithic column has been prepared in stainless steel tubing and used as the solid-phase extraction material in quantitative analysis of caffeine and theophylline in urine. Column switching, with water as mobile phase, was used for on-line cleaning and screening of human urine samples. Reversed-phase high-performance liquid chromatography was then performed on a C₁₈ column with methanol–water 30:70 (v/v) as mobile phase at a flow rate of 0.5 mL min^?1. Ultraviolet detection was performed at 274 nm. Good linear relationships were obtained between response and concentrations of caffeine and theophylline in the range 0.1–50 μg mL^?1. Absolute recovery ranged from 77.4 to 82.3% and inter-day and intra-day relative standard deviations were less than 5%. The method was suitable for analysis of caffeine and theophylline in human urine, because it eliminated tedious pretreatment and enabled rapid, economic, repeatable, and effective assay of traces of the drugs in biological samples.     

A Weak Cation-Exchange Monolithic SPE Column for Extraction and Analysis of Caffeine and Theophylline in Human Urine

A weak cation-exchange monolithic column has been prepared in stainless steel tubing and used as the solid-phase extraction material in quantitative analysis of caffeine and theophylline in urine. Column switching, with water as mobile phase, was used for on-line cleaning and screening of human urine samples. Reversed-phase high-performance liquid chromatography was then performed on a C₁₈ column with methanol–water 30:70 (v/v) as mobile phase at a flow rate of 0.5 mL min⁻¹. Ultraviolet detection was performed at 274 nm. Good linear relationships were obtained between response and concentrations of caffeine and theophylline in the range 0.1–50 μg mL⁻¹. Absolute recovery ranged from 77.4 to 82.3% and inter-day and intra-day relative standard deviations were less than 5%. The method was suitable for analysis of caffeine and theophylline in human urine, because it eliminated tedious pretreatment and enabled rapid, economic, repeatable, and effective assay of traces of the drugs in biological samples.

     

Synthetic ceramic clay material as stationary phase in packed column supercritical fluid chromatography

Summary A novel inorganic synthetic clay material (SC) has been evaluated as the stationary phase in packed-column, supercritical fluid chromatography (SFC). The molecular recognition capability of the SC stationary phase in SFC for polycyclic aromatic hydrocarbons has been evaluated using carbon dioxide and carbon dioxide modified with methanol as the mobile phase. This recognition derives from the layer structure of the SC material which acts as a slit to distinguish non-planar solutes from the molecular-molecular interaction between solute and stationary phase and leads to smaller retention for non-planar solutes. The recognition capability is also dependent on the SFC conditions such as column pressure and column temperature.     

Ultra-High Performance Liquid Chromatography with Electrospray Ionization Tandem Mass Spectrometry for the Determination of Caffeine in Energy Drinks

A simple and highly sensitive method for the determination of caffeine in energy beverages was developed and validated. Sample preparation utilizing solid-phase extraction (SPE) was simple and reliable. Separation by isocratic ultra-high performance liquid chromatography (UPLC) with a reversed-phase C₁₈ column was performed within 6 min. The use of SPE with UPLC coupled with electrospray ionization-multiple tandem mass spectrometry detection (ESI-MSⁿ) was accurate, reproducible, and validated for the determination of caffeine in energy drink matrices. The limit of quantification for caffeine was approximately 2.1 ng mL^?1. The intra-day and inter-day precisions were less than 4%, and the accuracy of the measurements was between 85.1% and 93.2%. Results for caffeine concentrations in eighteen beverages were compared to the values on the labels. This paper describes the first use of the UPLC–ESI-ion trap MSⁿ technique for quality-control purposes of caffeine present in energy drinks.     

Simultaneous Determination of Theobromine,Paraxanthine, Theophylline,and Caffeine in Urine by Reversed-Phase High-Performance Liquid Chromatography with Diode Array UV Detection

A reversed-phase high performance liquid chromatographic method was improved for the simultaneous determination of theobromine, paraxanthine, theophylline, and caffeine in urine. The method includes a liquid-liquid extraction at alkaline pH with ethylacetate. The 7-(2,3-dihidroxypropyl) theophylline was used as an internal standard (ISTD). The separation was achieved on a C₁₈ column using 14:86 methanol:buffer (25 mM KH₂PO₄ adjusted to pH 4 with ortho-phosphoric acid) solution as mobile phase under isocratic conditions at a flow rate 1 mL min^?1. An ultraviolet absorption at 274 nm was monitored. In these conditions, the LOD was 0.03 μg mL^?1 for theobromine, 0.02 μg mL^?1 for paraxanthine, 0.04 μg mL^?1 for theophylline, and 0.08 μg mL^?1 for caffeine. The method has been applied to urine samples.     

反相液相制备色谱法结合超临界流体制备色谱法分离纯化海风藤中的化合物

建立了基于反相液相制备色谱和超临界流体制备色谱的组合方法,用于分离纯化醇提水沉后石油醚层中的海风藤。首先以甲醇作为改性剂,采用醇提水沉法去除海风藤甲醇提取物中的叶绿素,加入硅藻土后用石油醚回流富集目标成分。选用反相C18制备色谱柱将其分为18个组分,然后将组分在SFC模式下进行制备。选用酰胺色谱柱,以甲醇为改性剂,在柱温30℃、背压15.0 MPa的条件下进行分离。基于反相色谱和超临界流体色谱不同的分离选择性,最后分离得到6个高纯度化合物。该法展示了反相制备色谱和超临界流体制备色谱在海风藤分离纯化方面的优势,特别是超临界流体色谱在天然产物的分析和制备方面的巨大潜力。     

Simultaneous Determination of Paracetamol and Caffeine in Human Plasma by LC–ESI–MS

A rapid, selective and convenient liquid chromatography–mass spectrometric method for the simultaneous determination of paracetamol and caffeine in human plasma was developed and validated. Analytes and theophylline [internal standard (I.S.)] were extracted from plasma samples with diethyl ether-dichloromethane (3:2, v/v) and separated on a C₁₈ column (150 × 4.6 mm ID, 5 μm particle size, 100 Å pore size). The mobile phase consisted of 0.2% formic acid–methanol (60:40, v/v). The assay was linear in the concentration range between 0.05 and 25 μg mL^?1 for paracetamol and 10–5,000 ng mL^?1 for caffeine, with the lower limit of quantification of 0.05 μg mL^?1 and 10 ng mL^?1, respectively. The intra- and inter-day precision for both drugs was less than 8.1%, and the accuracy was within ±6.5%. The single chromatographic analysis of plasma samples was achieved within 4.5 min. This validated method was successfully applied to study the pharmacokinetics of paracetamol and caffeine in human plasma.     

Simultaneous Determination of Paracetamol, Caffeine, Guaifenesin and Preservatives in Syrups by Micellar LC

A micellar liquid chromatographic technique allowing the separation and simultaneous determination of the active ingredients paracetamol, caffeine, and guaifenesin, and preservatives benzoic acid, methyl and propyl paraben is described. The separation was effective by using the Kromasil C18 column (150 mm × 4.6 mm, 5 μm) and a mobile phase of 1-butanol:water (1:99, v/v), containing 0.04 M sodium dodecyl sulfate and 0.1% (v/v) trichloroacetic acid, for eluting all compounds. The detection wavelength was set as 260 nm. The column heater was also used, set at 40 °C for these determinations. Under these conditions, separation of the six components was achieved in less than 30 min. The specificity of the method was demonstrated. Analytical characteristics such as limit of detection, limit of quantification, linear range, accuracy, precision (repeatability) and the influence of the various method parameters (robustness study) were evaluated. The developed method was applied to the determination of paracetamol, caffeine, guaifenesin, benzoic acid (sodium benzoate), methyl and propyl paraben in cough-drop syrups. Presented at the International Conference “Modern physical chemistry for advanced materials (devoted to the 100th birthday of Professor Nikolai Izmailov)”, Kharkov, Ukraine, June 2007.     

Demonstration of High Speeds with Low Pressure Drops Using 1.8 μm Particles in SFC

The literature contains few, if any, references to the use of sub-2 μm particles in supercritical fluid chromatography (SFC). In this study, the use of 1.8 μm particles in SFC is demonstrated, producing high efficiency chromatograms, less than 1 min long for each of a diverse range of solute families, including steroids, sulfonamides, profens, nucleic acids and xanthenes. Most of the solutes eluted from bare silica with surprisingly good peak shapes. The 3 × 100 mm column packed with 1.8 μm spherical silica particles, produced as many as 22,400 plates (80% of theoretical). Column head pressure did not exceed 410 bar and pressure drops did not exceed 240 bar, even at flows of 3 mL min^?1, or modifier concentration as high as 65%. Such performance produced the fastest solvation based chromatography (LC–SFC) reported to date. The chromatographic hardware requirements are met by older (400 bar max.) LC equipment. The speeds observed exceed even ultra high performance liquid chromatography (UHPLC), which requires dramatically higher pressure capability. Sub 2-μm particles appear suitable for routine use, employing common 400 bar LC equipment, only slightly modified to perform SFC, although faster detectors and smaller flow cells enhance performance.     

Determination of 19 Preservatives in Various Matrices by High-Performance Liquid Chromatography

A simple and sensitive high-performance liquid chromatography (HPLC) method was developed for the determination of 19 preservatives in cosmetic matrices. The composition of the mobile phase was optimized as a gradient to achieve a lower detection limit when compared to previously validated methods, and sample preparation conditions were investigated to optimize separation of the 19 preservatives. A C18 column was used with methanol, 0.05 mol/L ammonium acetate buffer, and water as the mobile phase under gradient elution conditions. Preservatives in cosmetics were extracted with 70% methanol using an ultrasonicator, after which they were analyzed with an HPLC-photodiode array detector. All preservatives were separated within 55 min. The recoveries ranged from 94.9% to 102.8%, with relative standard deviations of less than 3.2% and no correlation coefficients lower than 0.9986. Additionally, the developed method has a low detection limit, which makes it possible to analyze trace levels of compounds in various cosmetic and ingredient matrices.     

高效液相色谱法同时测定食品中6种对羟基苯甲酸酯

建立了同时检测食品中6种对羟基苯甲酸酯的高效液相色谱-二极管阵列检测器( HPLC-DAD)定量分析方法.样品用乙腈提取,经LC-C18固相萃取柱净化,采用Agilent C18色谱柱分离,甲醇/水溶液梯度洗脱,二极管阵列检测器检测,外标法定量.结果表明:6种对羟基苯甲酸酯在1.0～500.0 mg/L范围内线性关系良好(r≥0.9997);检出限为0.0016～0.0081 mg/L(S/N=3);6种对羟基苯甲酸酯各添加水平在经表面处理的新鲜蔬菜、水果、醋、碳酸饮料及牛奶,食品馅料中的回收率为85.1％～95.4％;相对标准偏差为3.6％～10.9％.     

Separation of Natural Food Pigments in Saponified and Un-Saponified Paprika Oleoresin by Ultra High Performance Supercritical Fluid Chromatography (UHPSFC)

The natural pigments in paprika were rapidly and efficiently separated by ultra high performance supercritical fluid chromatography. The separation of both un-saponified and saponified mixtures of paprika oleoresin were optimized, with run times of 10.6 min. Three different C18 columns, a cyano, silica and diol column, all 3 × 100 mm, with 1.8 μm particles were compared. The best separation for the un-saponified sample was found with an SB-C18 column, while the saponified samples were best separated on a bare silica, RX-Sil column. A SB-CN column allowed near optimum separation of both the unsaponified, and saponified samples, with similar run times. The best mobile phase was carbon dioxide (CO₂) modified with isopropyl alcohol (IPA), with a composition gradient. Fingerprints of several commercial pepper products indicated that one appeared to be colored with artificial dyes, while the color of a chili powder may have been enhanced with a paprika extract. Spectra, using CO₂ with IPA as modifier, produced a single maximum at 453 nm, which appears to represent up to a 30 nm solvatochromic shift from the maxima in most organic solvents. Acetonitrile (ACN) as modifier produced spectra with two maxima and a similar solvatochromic shift. These results appear to be the first on saponified paprika oleoresin samples using SFC. It is also the first detailed report on the separation of un-saponified samples. The results are up to six times faster than comparable results by HPLC. It appears that SFC is a viable, superior alternative to HPLC for the analysis of this important commercial product, without using ACN, or chlorinated solvents.     

Preparation of Titania Monolith Column and Application in Determination of Benzoic Acid by HILIC

The titania monolith column has been synthesized through a template-free sol–gel route, and a simple and reliable method for the determination of benzoic acid by hydrophilic interaction liquid chromatography using the prepared titania monolith has been developed. The influences of acetonitrile, acetate buffer and buffer pH on the retention of benzoic acid were investigated. Benzoic acid in carbonated drinks and fruit beverages samples were determined within 5 min and quantitative analysis was carried out by external standard method with a correlation coefficient (R ²) of 0.9984. The relative standard deviation was 0.91 % and the recovery ranged from 92.5 to 101.3 %. The proposed method is suitable for the analysis of benzoic acid in beverage samples.

     

A molecular imprint-coated stirrer bar for selective extraction of caffeine, theobromine and theophylline

We have prepared a novel caffeine imprinted polymer on a stir bar that can be used for selective extraction of caffeine, theobromine and theophylline from beverages. The polymerization time and quantities of reagents (template, cross-linker, porogenic solvent) were optimized. The morphology of the molecularly imprinted polymer-coating was studied by scanning electron microscopy and Fourier transform IR spectroscopy. A rapid and sensitive method was worked out for the extraction of caffeine, theobromine and theophylline from beverages by using the molecularly imprinted stir bar followed by HPLC analysis. The effects of extraction solvent, stirring speed, desorption solvent, adsorption and desorption time were optimized. The method displays a linear response in the 5–150 μg L^?1 caffein concentration range, with a correlation coefficient of >0.9904. The recoveries for three analytes in tea, carbonated and functional beverages were 91–108 %, 90–110 % and 93–109 %, with relative standard deviations ranging from 3.6–5.7 %, 3.5–7.9 % and 3.2–7.9 %, respectively.

Validated LC-ESI-MS/MS Method for the Quantitation of Neopanaxadiol: a Novel Neuroprotective Agent from Panax ginseng and Its Application to a Pharmacokinetic Study in Rat Plasma

Neopanaxadiol (NPD), a new panaxadiol first obtained from the acid hydrolysate of the total ginsenosides of Panax ginseng C. A. Meyer (Araliaceae) in our laboratory, showed neuroprotective effect against glutamate-induced neurotoxicity in primary cultures of rat cortical cells (Tao et al. Chin Chem Lett 20:687–689, 2009). In this research, a sensitive and specifical method of ultra-performance liquid chromatography–electrospray mass spectrometry (UPLC-ESI-MS/MS) for the quantitative analysis of NPD in rat plasma was developed. The NPD and internal standard of panaxadiol were extracted from 200 μL of rat plasma samples with methanol, then the samples were injected in an UPLC (Waters BEH) with C18 column (50 mm × 2.1 mm i.d., 1.7 μm) and eluted with the mobile phase consisting of methanol–water–formic acid (80:20:0.2, v/v/v). Excellent linearity was found between 5 and 160 ng mL^?1 with a limit of quantitation of 4 ng mL^?1. Intra- and inter-day precision values (RSD) of QC samples were both below 7 %. This study was successfully utilized for the pharmacokinetic profiles of NPD in rats after oral administration and provided an experimental basis for the further pharmacology and clinical application of ginseng products.