Micellar electrokinetic capillary chromatography of methylxanthines‐containing beverages: discussion of the molecular species involved

Micellar electrokinetic capillary chromatography (MECC) experimental conditions were applied to 12 samples of methylxanthine‐containing infusions of different commercial brands of yerba mate, coffee, tea and cocoa as well as two cola drinks. The best resolution in this mode of automated high‐performance capillary electrophoresis (HPCE) was achieved here when using 15 kV voltage in an uncoated fused‐silica capillary of 45 cm length (40 cm effective length), 50 mM sodium dodecylsulfate, 90 mM pH 8.5 borate buffer and UV detection. Theobromine, caffeine and theophylline were separated, and the peak splitting due to tautomeric species was observed. Experimental conditions were controlled, keeping constant the size of the elution window in each analysis. The limit of detection was less than 1 mg l^?1, the limit of quantitation was 2.5 mg l^?1 and the work range was 2.5–300 mg l^?1. This HPCE–MECC system has proved suitable for the analysis/quality control of xanthines in beverages for consumption. Roles of various parameters as well as distinctly charged species of each xanthine and the origin of peak splitting in this MECC system are discussed. Copyright © 2004 Society of Chemical Industry     

5-Hydroxymethylfurfural content in foodstuffs determined by micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) has been applied for the determination of 5-hydroxymethylfurfural in several foodstuffs. A 75 mM phosphate buffer solution at pH 8.0 containing 100 mM sodium dodecylsulphate was used as background electrolyte (BGE), and the separation was performed by applying +25 kV in a 50 μm I.D. uncoated fused-silica capillary. Good linearity over the range 2.5–250 mg kg⁻¹ (r² ? 0.999) and run-to-run and day-to-day precisions at low and medium concentration levels were obtained. Sample limit of detection (0.7 mg kg⁻¹) and limit of quantification (2.5 mg kg⁻¹) were established by preparing the standards in blank matrix. The procedure was validated by comparing the results with those obtained with liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). Levels of HMF in 45 different foodstuffs such as breakfast cereals, toasts, honey, orange juice, apple juice, jam, coffee, chocolate and biscuits were determined.     

Quantification of 5-Hydroxymethylfurfural in Coated Deep-Fried Products: Optimization of the Extraction Procedure by Using Statistical Design

This study describes for the first time the development and validation of an extraction procedure for the quantification of 5-hydroxymethylfurfural (HMF) in coated deep-fried products by liquid chromatography with photodiode array detection. The method entailed the extraction of HMF with ethyl acetate/hexane (4:1) followed by a concentration step with 40 mM sodium formate (pH?=?3)/methanol (1:1). The optimum combination of the extraction variables was achieved by response surface methodology. Sample amount and concentration solvent volume showed a notable influence on HMF yield, while the effect of extraction solvent volume seemed to be less marked. From experimental results, 5 g of sample, 10 ml of the extraction solvent, and 550 μl of the concentration solvent were selected as optimal combination. The consistency between predicted and experimented values as well as in the quality parameters was observed. Quantities of HMF in coated deep-fried fish products were 1.25?±?0.21 μg g^?1.     

An Aqueous High-Performance Liquid Chromatographic Procedure for the Determination of 5-Hydroxymethylfurfural in Honey and Other Sugar-containing Materials

ABSTRACT: A new, all aqueous high-performance liquid chromatography (HPLC) procedure for the determination of 5-hydroxymethylfurfural (HMF) in honey and other sugar-containing materials was developed without harmful chemicals. The method involved dilution of the sample in water and the analysis of the diluent using an HPLC system equipped with an absorbance detector and a 30-mm sulfonated poly(styrene-divinylbenzene) cation exchange column. Water was used as the mobile phase at a high flow rate of 2.00 mL/min Using this high flow rate in conjunction with a column heater set at 55°C, HMF eluted in less than 4 min. Overall precision was less than 1% relative standard deviation, recovery of HMF from spiked samples was approximately 99%, and there were no interferences from similar compounds such as 2-furfural and 5-methylfurfural. Several sugar-containing materials were analyzed by this method where the results compared well with the classic Winkler spectrophotometric procedure, but not as well with a commonly used reverse-phase HPLC technique. In addition, several consumer products were also analyzed for their HMF content.     

糖的高效毛细管电泳分离及其在烟草分析中的应用

简要介绍了糖类化合物的毛细管电泳分析技术 ,包括毛细管区带电泳 (CZE)、毛细管凝胶电泳 (CGE)和胶束电动毛细管色谱 (MECC)等分离模式 ,以及近年来毛细管电泳技术在烟草中糖类化合物分析中的应用。     

HMF Formation during Heat-treatment of Milk-type Products as Related to Milkfat Content

Homogenized lactose/caseinate model systems and milk with different fat content were heated at 110 to 150 °C for up to 30 min. Free and total hydroxymethylfurfural (HMF) were measured by reverse-phase high-performance liquid chromatography. Multifactor analysis of variance was applied to determine whether milkfat content contributed to free and total HMF formation. There was a negative effect of milkfat on the formation of total HMF in both systems. However, free HMF formation was promoted by higher milkfat content in milk, but not in the lactose-caseinate model. Milkfat affected also the free and total HMF formation in commercial pasteurized milk, ultra heat-treated milk, and bottle-sterilized milk.     

Determination of HMF in Vinegar and Soy Sauce Using Two-Step Ultrasonic Assisted Liquid–Liquid Micro-Extraction Coupled with Capillary Electrophoresis-Ultraviolet Detection

A new, rapid, and inexpensive method using two-step ultrasonic assisted liquid–liquid micro-extraction (UALLME) coupled with capillary electrophoresis-ultraviolet (CE-UV) was developed for 5-hydroxymethylfurfural (HMF) analysis in high ion strength samples (like vinegar and soy sauce). The factors affecting the extraction efficiency were optimized such as the extraction volume, the ultrasonic time, and the power density of ultrasonic. Under the optimum conditions, the limit of detection (LOD) and the limit of quantification (LOQ) for HMF were 0.03 and 0.10 mg/L, respectively. The relative standard deviations (RSD %) for HMF were ranging from 0.53 to 3.17%, and the recoveries of HMF were ranging from 91.24 to 109.39%. The results turned out that two-step UALLME-CE-UV was applicable to analyze HMF in vinegar and soy sauce. Eleven brands of vinegar and soy sauce were tested by two-step UALLME-CE-UV, and the results showed that the method had a potential application in analysis of foodstuffs. The two step UALLME method was effective to improve the selectivity and sensitivity of CE-UV method for HMF analysis in vinegar and soy sauce.     

LIF-HPCE法检测食品中的黄曲霉毒素B1

采用自行设计搭建的激光诱导荧光(LIF)- 高效毛细管电泳(HPCE)检测平台,建立LIF-HPCE 法对食品中的黄曲霉毒素B1(AFB1)进行高灵敏度检测。AFB1 在胶束电动毛细管电泳(MECC)模式下分离,LIF 检测,375nm 激光进行激发,检测波长440nm,操作电压15kV,电流104μA。AFB1 在0.5～50μg/kg 浓度范围内线性关系良好,r ＝ 0.9994;最低检出质量1.7 × 10-13g(S/N ＝ 3),最低定量限5.6 × 10-13g(S/N ＝ 10),方法精密度和重复性的相对标准偏差为5% 左右。测定食品中粮油等食品样品,加标回收率为84.1%～96.1%。所建立的方法无需进行衍生反应和荧光标记,快速灵敏,绿色环保,10min 左右完成分析,适用于食品中黄曲霉毒素的高灵敏度检测。     

N-TERMINAL AMINO ACIDS OF BRAZIL NUT 7S PROTEIN1

N-terminal analysis of Brazil nut (Bertholettia excelsa) 7S protein was carried out using the dansyl chloride method and micellar electrokinetic capillary chromatography (MECC) for analysis of the dansyl-amino acids. Lysine, arginine and proline were identified as the N-terminal amino acids of the 7S protein. Subunits of the 7S protein, isolated by preparative SDS-PAGE, were also analyzed. The results are discussed in terms of the subunit composition of the protein.     

Kinetics of 3-deoxy-D-erythro-hexos-2-ulose in unifloral honeys

In this study, for the first time, the amount of 3-deoxy-D-erythro-hexos-2-ulose (3-DG) in fresh citrus and chestnut honeys was determined. 3-DG was measured as the corresponding quinoxalines after derivatization with orthophenylenediamine using reverse-phase high-performance liquid chromatography (RP-HPLC). Notwithstanding the freshness of the samples, high levels of 3-DG were detected in both honeys. The comparison of 3-DG and 5-hydroxymethylfurfural (HMF) concentrations, which was also quantified by RP-HPLC, showed that citrus honeys had the lowest amount of 3-DG (107 mg/kg) and the highest of HMF (16.7 mg/kg), while chestnut honeys had the opposite (398 and 1.2 mg/kg, respectively). During thermal treatment, different 3-DG and HMF trends were highlighted between the citrus and chestnut honeys; at the end, 3-DG formation was more favored with respect to HMF formation. Moreover, in citrus honeys, a good correlation between 3-DG and HMF levels was observed, which was not found in chestnut honeys, suggesting a role of the high pH values of these honeys on the degradation routes. The kinetic analysis showed the highest k value for 3-DG and HMF formation in chestnut and citrus honeys, respectively. The lowest Ea values related to 3-DG formation and the highest to HMF formation, indicating that the key intermediate 3-DG is easily formed at low temperatures, whilst the formation of HMF requires higher temperatures. For this reason, 3-DG seems to be an aging index rather than a thermal index and its use, at least for honeys at high pH values, together with HMF, could improve their quality assessment.     

Characterization of molds isolated from smoked paprika by PCR-RFLP and micellar electrokinetic capillary electrophoresis

Molds are common contaminants of paprika meat products. The drying and storage stages of paprika processing are critical because they can provide molds with the conditions particularly appropriate for their growth and proliferation. Thus, an efficient and accurate characterization of the toxigenic molds of paprika is necessary. An RFLP analysis of the rRNA genes was performed by using a TaqI restriction enzyme. In addition, a micellar electrokinetic capillary chromatography (MECC) method was tested to analyze secondary metabolites produced by mold strains commonly found in paprika. This study was confirmed with a 5.8S-ITS region sequence analysis. A total of 31 isolates were identified by RFLP and MECC analysis. These showed stable RFLP profiles that were clearly different for the different genera and species, and were grouped into clusters together with the profiles of the 16 reference strains. MECC analysis provided additional characteristic peak patterns for the characterization of the mold species present. The characterized isolates were species of the genera Fusarium spp., Aspergillus spp., Penicillium spp., Cladosporium spp., Mucor spp. and Phlebia spp. The identifications were confirmed by the 5.8S-ITS region sequence analysis and by a BLAST search of the GenBank database. RFLP patterns with TaqI restriction enzyme and MECC profiles, either singly or combined, could be of great interest to distinguish molds in paprika.     

Characterization of molds from dry-cured meat products and their metabolites by micellar electrokinetic capillary electrophoresis and random amplified polymorphic DNA PCR

Molds are common contaminants of dry-cured meat products in which mycotoxins could be synthesized if stored under favorable conditions. Thus, efficient and accurate characterization of the toxigenic molds from dry-cured meat products is necessary. A micellar electrokinetic capillary chromatography (MECC) method was tested to analyze secondary metabolites produced by 20 mold strains commonly found in dry-cured meat products. In addition, their random amplified polymorphic DNA (RAPD) genotypes were determined by using a PCR method. Although peak profiles of the secondary metabolites differed among mold strains of different species, they were similar in the same species. MECC analysis showed that 10 of the 20 molds tested produced mycotoxins, including patulin, penicillic acid, cyclopiazonic acid, mycophenolic acid, aflatoxin B1, sterigmatocystin, and griseofulvin. The RAPD analysis yielded a different pattern for each of the mold species tested. However, strains of the same species showed similar RAPD profiles. A high correlation between RAPD analysis and MECC was observed, since strains of the same species that showed similar RAPD patterns had similar profiles of secondary metabolites. RAPD patterns with primer GO2 and MECC profiles, either singly or combined, could be of great interest to distinguish toxigenic from nontoxigenic molds in dry-cured meat products.     

Methods quantitative for determination of water-soluble vitamins in premixes and fortified food products by micellar electrokinetic chromatography on short end of the capillary

It was purposed new technique by micellar electrokinetic chromatography on short end of the capillary (capillary electrophoresis system Agilent 3D CE, DAD, quartz capillary HPCE stndrd cap 56 cm, 50 microm, 50 mM borate buffer pH=9,3, 100 mM sodium dodecil sulfate) for simultaneous determination of water-soluble vitamins (B1, B2, B6, B12, PP, B5, B9, C, B8) in fortified food products and premixes. It was observed on 6 samples of vitamin premixes and 28 samples of fortified food products using this technique. Our findings are consistent with the results of research on certain vitamins, conducted by other methods. The developed technique can be used in analysis of water-soluble vitamins in premixes and fortified food products.     

Capillary Zone Electrophoresis and Micellar Electrokinetic Capillary Chromatography for Determining Water-Soluble Vitamins in Commercial Capsules and Tablets

ABSTRACT: A rapid method was developed for simultaneously determining thiamine, riboflavin, pyridoxine, nicotinamide, nicotinic acid, and ascorbic acid. It was tested on 15 samples. The peaks of all components were cleanly separated with good resolution by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MECC). CZE was performed with 0.02 M borate buffer, and MECC was performed with 4% acetonitrile in 0.02 M borate/phosphate buffer containing 0.1 M sodium dodecyl sulfate. Average recoveries for all components were 80.3% to 103.7% with coefficients of variation being less than 5%. Thiamine, nicotinic acid, and pyridoxine contents were consistent with those labeled on the packages, but nicotinamide, riboflavin, and ascorbic acid contents of some samples were less.     

Determination of histamine in fish products by capillary electrophoresis and ion‐pair liquid chromatography with diode‐array detection

A method for histamine determination in fish and fish products by capillary electrophoresis and ion‐pair liquid chromatography has been developed. Histamine was extracted from different fish samples with 10% trichloroacetic acid, and the filtrate was directly applied to capillary electrophoresis apparatus. A preliminary purification through a solid phases extraction cartridge (Sep‐pak C₁₈) was necessary for HPLC analysis. Histamine was detected ‘on‐line’ at 210 nm by both approaches. HPLC procedure allowed accurate (±2.2%) and repeatable (±1.6%) determination of histamine in fish products at appropriate levels (20–100 mg kg⁻¹) to meet current regulations. © 1999 Society of Chemical Industry     

Optimization analysis by capillary electrophoresis of thiamine in meat: comparison with high perfomance liquid chromatography

 A new capillary electrophoresis (CE) method for the analysis of thiamine in meat is proposed. Samples were submitted to acidic and enzymatic hydrolysis and the extracts were purified using ethanol and an ion exchange column. The thiamine content was determined by CE using 100 mM sodium tetraborate, 50 mM sodium phosphate (pH 7.6), 50 mM sodium dodecyl sulphate and 10% isopropyl alcohol as a separation buffer solution. The analysis was carried out at 15 kV and 50  °C in a 70 cm effective length× 75 μm i.d. fused-silica capillary using on-column UV detection at 254 nm and 7 s injection time (27 nl injection volume). The results obtained by CE for thiamine contents in meat were compared to those obtained by HPLC using an ion-pair reverse phase column with post-column derivatization and fluorescence detection. Received: 24 August 1998 / Revised version: 21 January 1999     

Development of high‐performance liquid chromatography and non‐aqueous capillary electrophoresis methods for the determination of fenoxycarb residues in wheat samples

BACKGROUND: Practical methods for the analysis of fenoxycarb residues in wheat samples were developed using high‐performance liquid chromatography (HPLC) and non‐aqueous capillary electrophoresis (NACE). RESULTS: Fenoxycarb residues in wheat were extracted with acetone by ultrasonication, followed by a clean‐up procedure with liquid–liquid extraction with 5% NaCl/dichloromethane. The HPLC was developed using C18 as column, MeOH/water (6:4, v/v) as the mobile phase and 199 nm as the detection wavelength. The optimal NACE condition was established with the running buffer of 20.0 mmol L^?1 NH₄Ac in 95% MeOH (pH* 9.0), and the applied voltage of 30 kV over a capillary of 50 µm i.d. × 48.5 cm × 40 cm effective length. Both methods gave the relatively lower limits of detection (0.008 mg kg^?1 for HPLC and 0.024 mg kg^?1 for NACE) and the higher recoveries (>85.0%). They were successfully applied to the determination of fenoxycarb in wheat samples. CONCLUSION: The results showed that the fenoxycarb residue gradually reduced to trace amounts after about 3 years, which implied that the pharmacological actions of fenoxycarb could last for about 3 years. Meanwhile, more effort should be made to control and reduce fenoxycarb residues because of its potential health risks to consumers. Copyright © 2007 Society of Chemical Industry     

MONITORING NONENZYMATIC BROWNING IN CAKES PREPARED WITH HIGH FRUCTOSE CORN SYRUP BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

The purpose of this study was to utilize high performance liquid chromatography (HPLC) and colorimetric methodology to monitor specified products of nonenzymatic browning in cakes prepared with high fructose corn syrup. Cakes were prepared with different concentrations of high fructose corn syrup (HFCS) as a sucrose replacement. Cream of tartar, an acidulant, was used to alter the pH of the batter and reduce nonenzymatic browning. Total browning, hydroxymethylfurfural (HMF), and furosine (a reducing sugar derivative) were analyzed. Analysis of variance for cakes prepared with different concentrations of HFCS, with and without an acidulant, showed significant differences among the different treatments (P ≤ 0.05) for HMF, furosine, and total browning.     

Hydroxymethylfurfural in fruit puree and juice: preconcentration and determination using microextraction method coupled with high-performance liquid chromatography and optimization by Box–Behnken design

In the present study, a sensitive and rapid method for separation and determination of hydroxymethylfurfural (HMF) in fruit puree and juices was proposed. Dispersive liquid–liquid microextraction (DLLME) coupled with high-performance liquid chromatography (HPLC) was used for extraction and quantitative determination of HMF in fruit puree and juices. The effective parameters such as the type and volume of extraction and dispersive solvents, pH and salt amount (NaCl) were studied and optimized with the aid of response surface methodology based on Box–Behnken design to obtain the best condition for HMF extraction. At the optimized conditions, parameter values were 60 µL extracting solvent, 600 µL dispersive solvent, 2 g NaCl and pH 5. Repeatability of the method, described as the relative standard deviation, was 3.1% (n?=?6) and the recovery was 98.4%. The limit of detection and limit of quantitation were 1.47 and 5.28 µg L^?1, respectively. The merit figures of DLLME–HPLC–UV method showed that the proposed method can be noticed as a new, fast and good alternative method for investigation of HMF in various fruit puree and juice samples.     

高效毛细管电泳法测定酱油中5'-单磷酸核苷酸

建立高效毛细管电泳同时分离测定酱油中两种核苷酸鸟嘌呤-5O`-单磷酸(GMP)和次黄嘌呤-5O`-单磷酸(IMP)的方法。电泳条件：以50μm×60.2cm(有效长度50cm)未涂敷石英毛细管为分离柱,30mmol/L硼砂＋30mmol/L碳酸钠＋60mmol/L羟丙基-β-环糊精为分离缓冲溶液,50mmol/L醋酸溶液为样品介质,检测波长为254nm。GMP及IMP的校正峰面积与质量浓度在5～100mg/L范围内具有良好线性关系,线性相关系数分别为0.9998和0.9997,检出限均为2mg/L,定量限均为5mg/L。用该法测定了9种酱油,并与文献报道的高效液相色谱法的结果进行比较,结果满意。