固相萃取-HPLC法同时测定肉制品中苋菜红、胭脂红、日落黄和诱惑红的含量

建立了利用固相萃取-高效液相色谱法同时测定肉制品中4种合成色素的检测方法.样品经乙醇、氨水和水溶液(7∶2∶1,mlm)提取后,固相萃取净化,经C18柱分离,用紫外检测器检测.结果表明:4种合成色素分离良好,加标平均回收率为66.7％～99.7％,相对标准偏差1.9％～3.6％.该方法准确度和精密度较高,可应用于测定肉制品中的合成色素.     

Development and Validation of a Method for Determination of Residual Nitrite/Nitrate in Foodstuffs and Water After Zinc Reduction

An environmentally friendly and cost-effective spectrophotometric method to analyze nitrate and/or nitrite was developed. The method is based on reduction of nitrate with zinc powder (instead of the cadmium or enzymes used in the standard methods approved by ISO/CEN). The initial nitrite concentration and total nitrite after reduction are determined by the very sensitive and widely used diazotization-coupling Griess reaction. A single-laboratory validation was applied in five different matrices (vegetable, meat product, baby food, dairy product, and surface water). The results show that the new method fulfills the international criteria for precision and recovery. The limit of detection for several matrices, calculated using fortified samples, ranged from 3 to 5 mg/kg for both nitrite and nitrate. Furthermore, the results obtained were in good agreement with those obtained using the CEN method (HPLC) and the ISO method (Cd reduction).     

固相萃取-高效液相色谱法测定水产品中的苯巴比妥

建立水产品中苯巴比妥残留量测定的固相萃取-高效液相色谱方法。样品经乙酸乙酯提取,正己烷脱脂,通过C18固相萃取小柱富集和净化,高效液相色谱仪进行检测。苯巴比妥在0.05～4.0μg/mL内线性范围良好,相关系数为0.9999。当添加量在30～200μg/kg时,加标回收率在80.49%～102.42%,相对标准偏差为1.52%～10.15%,方法检出限10μg/kg,定量限30μg/kg。研究结果表明本方法操作简单、准确度高,能满足水产品中苯巴比妥残留量的测定及确证工作的需要。     

Simultaneous Determination of Alpha-Tocopherol and Alpha-Tocopheryl Acetate in Dairy Products,Plant Milks and Health Supplements by Using SPE and HPLC Method

A solid phase extraction technique for sample cleanup and extraction of α-tocopherol and α-tocopheryl acetate is described and applied to their simultaneous HPLC analysis in dairy products, plant-based milks, infant formulas, and pharmaceutical colostrum. The proposed method includes sample pretreatment by using ethanol, followed by solid-phase extraction of the organic supernatant on C18 cartridges. The identification and quantification were done by reversed-phase HPLC with fluorescence detection (ex 295 nm, em 330 nm) for tocopherol and with UV detector set at 220 nm for tocopheryl acetate. The mobile phase consisted of 100% acetonitrile. The linear ranges were from 0.02–0.40 μg/mL (dairy products) and 0.50–5.00 μg/mL (plant milks, infant formulas, powdered products) for α-tocopherol and those of α-tocopheryl acetate were from 0.20–2.00 μg/mL (dairy products) and 1.00–10.0 μg/mL (plant milks, infant formulas, powdered products). The LOD and LOQ of α-tocopherol were 0.1 and 0.4 μg/mL, while those of the α-tocopheryl acetate were 2.0 μg/mL for LOD and 6.0 μg/mL for LOQ. The method gave extraction recoveries from 73–94% with RSDs values being 5–10%. This method is simple, SPE procedure is fast and HPLC analysis time is less than 10 min. The total time of performing analysis per sample is less than 1 h. The important advantage of the proposed method is the capability of determining and reporting α-tocopherol and α-tocopheryl acetate separately. Moreover, the developed method is suitable for fast screening of the synthetic form of vitamin E in dairy products, plant-based milks, infant formulas, and pharmaceutical colostrum.     

Effect of adding smoke-flavouring to frankfurters on nitrite and nitrate levels

Different concentrations of sodium nitrite, potassium nitrate or both together were used to prepare four standard solutions and four frankfurter formulations. These were elaborated with and without the addition of 2 g/kg of a commercial solid smoke-flavouring preparation. Monitoring of nitrite and nitrate residual levels in standard solutions stored at 3 °C showed that smoke-flavouring addition results in a depletion of nitrite levels and/or reduction of nitrate to nitrite. In a much more complex system such as meat products, nitrite and nitrate, incorporated in the formulation separately or combined, were also rapidly depleted when smoke-flavouring was added.     

Fast Determination of Sodium Monofluoroacetate in Liquid Milk and Dairy Powder by Hydrophilic Interaction Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Manufactured sodium monofluoroacetate is a rodenticide with high acute toxicity. A fast and sensitive analytical method in liquid milk and dairy powder was developed both for routine analysis and for fast tackling the terrorist threat. Monofluoroacetate was extracted from liquid milk using acetonitrile and from dairy powder with water and acetonitrile, cleaned using a solid phase extraction (SPE) cleanup procedure with polymeric anion exchange (PAX) cartridge, and measured by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). The conditions for the monofluoroacetate extraction, SPE cleanup, and instrument injection solvent were optimized. A BEH amide chromatographic column with hydrophilic interaction was used to directly separate monofluoroacetate under basic conditions. The limits of detection in liquid milk and dairy powder were 1 and 2 μg kg^-1, respectively. The recoveries at three spiking levels (10, 50, and 200 μg kg^-1) were 72.5–97.6 % with relative standard deviations (RSDs) of 4.7–5.9 % for liquid milk and 70.1–92.8 % with RSDs of 4.7–6.8 % for dairy powder. The method has been applied to analyze sodium monofluoroacetate in dairy products including infant formula.     

高效液相色谱串联质谱法测定蔬菜中苯醚甲环唑的残留量

建立高效液相色谱-串联质谱检测蔬菜中苯醚甲环唑残留的分析方法。样品采用乙腈提取,经石墨碳黑-氨基串联固相萃取(GCB/NH2 SPE)柱净化,液相色谱分离多反应监测模式下测定,外标法定量。结果显示：苯醚甲环唑质量浓度在1～500ng/mL范围内线性关系良好。苯醚甲环唑在不同基质中平均回收率为79.3%～108.0%,相对标准偏差为2.7%～8.5%,检出限为0.001mg/kg。该方法灵敏度高,准确度、精密度好,满足样品测定的定性、定量要求。     

Phospholipids in milk and dairy products

A rapid HPLC method has been developed for the analysis of the phospholipids in milk and dairy products. A concentrate of the phospholipids was obtained by chromatography on a cartridge of silica gel. The relative proportions of the different phospholipids were then determined by HPLC, and by means of the addition of an internal standard, dipalmitoyl phosphatidyldimethylethanolamine, the absolute amounts present were also measured. After the reproducibility of the method was demonstrated with fresh whole milk, it was applied to skimmed milk, buttermilk and various products of ultra-high temperature processing. Small differences only were seen in the relative compositions of phospholipids in different milk products, but the absolute amounts varied appreciably. In some samples, it was tentatively concluded that the phospholipids had undergone extensive autoxidation.     

Determination of free fatty acids in milk and dairy products by reversed-phase HPLC with fluorescence detection

A highly sensitive HPLC with fluorescence detection was developed for the determination of free fatty acids (FFAs) in milk and dairy products. For this purpose, the FFAs were extracted from small amounts of milk (1.0 mL), cheese (0.5 g) and butter (0.5 g) using Sep-Pak cartridge columns, and then derivatized to 9-anthrylmethyl esters with 9-anthryldiazomethane (ADAM). Good separations of the ADAM derivatives of 16 FFAs (C4-C18) that exist in milk, cheese and butter, which permitted quantitative estimation of their individual FFAs, were achieved by HPLC on a C18 column (Cadenza CD-C18, 150 x 3 mm i.d.) using gradient elution with methanol and water. The acid values calculated from the contents of individual FFAs were in good agreement with those obtained by the conventional titration method. These results demonstrate that the present HPLC method is simple, sensitive and precise, and could be utilized widely for determination of the FFAs in milk and dairy products.     

Evaluation of a solid phase extraction procedure for the determination of pesticide residues in foodstuffs

An evaluation of a method based on solid phase extraction (SPE) as a clean‐up stage for the determination of pesticide residues in composite vegetable and cabbage samples is presented. Samples are extracted with acetonitrile and the extract is loaded onto an SPE cartridge. The pesticides are eluted with a mixture of acetonitrile/toluene (3:1 v/v) and determined by GC–MS or HPLC with fluorescence detection. Acceptable recoveries were obtained for 31 pesticides. An investigation of the effect of partial, as opposed to exact, matrix matching of standards in GC–MS analysis is also presented. While the variation using unmatched standards is visibly greater, the difference is not such as to require exact matrix matching for residue‐screening work. The procedure removes the need for chlorinated solvents, reduces the volumes of other solvents used and allows increased sample throughput compared with liquid–liquid extraction procedures. © 1999 Society of Chemical Industry     

离子色谱法测定豆奶粉中硝酸盐、亚硝酸盐含量

为了建立离子色谱测定豆奶粉中硝酸盐、亚硝酸盐的含量的方法。样品用去离子水提取,固相萃取后,采用离子色谱法测定豆奶粉中硝酸盐、亚硝酸盐的含量。结果表明：硝酸盐或亚硝酸盐的线性范围分别为1～50、1～25mg/mL,回收率分别为89.3%～98.9%、89.6%～102.0%,检出限分别为0.16、0.11mg/kg。该法灵敏、准确,前处理简单易行,可用于豆奶粉中的硝酸盐、亚硝酸盐含量测定。     

Analysis of benzo[a]pyrene content from smoked food products in Korea

The content of benzo[a]pyrene (BaP) was evaluated from 100 smoked food products commonly consumed in Korean market with HPLC. Analysis method for BaP content on smoked food products was evaluated and validated. For validation, the efficiency of saponification time and solid phase extraction cartridges were evaluated. During 1–4 h of saponification, recovery of BaP was ranged from 90.17 to 98.87%. Among the 5 tested cartridges including florisil, silica gel, and alumina cartridges (acidic, basic, and neutral), the most efficient cartridge was florisil cartridge and the recovery of BaP was 98.87%. Limit of detection and limit of quantification was 0.03 and 0.09, respectively. As a result of BaP content analysis from smoked food products, the average BaP content was 0.45 μg/kg and the highest content of BaP was 2.87 μg/kg detected in smoked salmon product.     

基于高效液相色谱法对农产品中吡虫啉的提取和净化

基于高效液相色谱法,对不同农产品中吡虫啉的不同提取和净化方法进行比较,建立农产品中吡虫啉农药残留的检测方法。样品经乙腈提取后,采用WondaSep GC-e/PSA固相萃取柱净化,以乙腈-0.1%磷酸为流动相梯度洗脱,XBridge C18色谱柱进行分离,二极管阵列检测器检测,外标法定量。考察不同农产品加水或不加水提取对吡虫啉提取的影响,以及固相萃取和QuEChERS对干扰基质的净化效果。研究表明：不同提取方法和净化方法,对不同农产品影响差异较大。该方法中吡虫啉在0.05～10.0 μg/mL范围内线性关系良好（R2≥0.999）,平均回收率在88.3%～109.1%之间,相对标准偏差不大于3.5%。本研究可为农产品中吡虫啉农药残留的监测提供技术支持。     

Evaluation of the stable reaction products of histidine with formaldehyde or with other carbonyl compounds in dairy products

Combined formaldehyde (FA) can be evaluated in cheese and other dairy products by determining spinacine (6-carboxy-1,2,3,4-tetrahydroimidazopyridine), an imino acid arising from the reaction of FA with the -amino group of histidine. Other carbonyl compounds usually produced by fermentations can react themselves with histidine, forming molecules which interfere with the determination of spinacine. A sensitive (minimum detectable amount, 5 fmol spinacine) and interferencefree HPLC method, with precolumn derivatization with o-phtalaldehyde (OPA) and 9-fluorenylmethylchloroformate (FMOC), to evaluate these histidine reaction-compounds in dairy products is described. The clean-up of the FMOC-derivatized sample has been performed for the first time with solid-phase extraction (SPE) on an amino cartridge. The method was applied to samples of casein and differently ripened cheese, the origins of which were either known or commercial, in order to quantify the natural level of spinacine (0.7–2.7 ppm) probably deriving from biogenic FA, and to detect whether FA was used in processing.     

The development of burfi sweetened with aspartame

Sucrose was successfully replaced with the sweetener aspartame for the preparation of the indigenous dairy product burfi . Analytical conditions were standardised for the solid phase extraction of aspartame and its degradation products from burfi followed by their reverse phase HPLC. Recovery using this method was 90–97%. Aspartame at a level of 0.065% of milk w/w scored highest in terms of sweetness perception and resembled control burfi in sweetness. Storage studies at 6–8°C revealed that aspartame-sweetened burfi resembled the control burfi in retaining the sensory profile, but showed an increase in acidity and microbial load and could not retain the texture. High-performance liquid chromatography analysis revealed no degradation of aspartame in burfi , establishing its stability and hence its sweetness on storage.     

Nitrate and Nitrite Methods of Analysis and Levels in Raw Carrots, Processed Carrots and in Selected Vegetables and Grain Products

Methods for quantitative estimation of nitrate and nitrite were compared. Levels of these ions were measured in vegetables and grain products and effects of processing on nitrate and nitrite levels in carrots were measured. These data allow more accurate estimation of ingestion levels and suggest means to reduce exposure to these ions. High performance liquid chromatography (HPLC) had better precision and recoveries than either a classical Cd-Griess method nitrate or a Griess method for nitrite. Nitrate concentration by HPLC varied greatly within and between vegetables, ranging from 1 μmol/100g in mushrooms to 5000 μmol/100g in celery and averaging 9.7 ± 4.4 μmol/100g in grains. Nitrate levels in vegetables sold as “organic” were not different (p<0.05) from conventional vegetables. No nitrite was detected in either vegetables or grains. Nitrate was unevenly distributed in carrots with the core having the most. Storage of carrots at -18°C for 10 wk did not alter nitrate levels and no nitrite developed. Fifty-seven percent of nitrate was leached into cooking liquid when frozen carrots were boiled. Thirty-two percent of nitrate was lost during canning and 47% of the remainder was in the liquid. No nitrite developed during 10 wk of canned storage.     

Determination of bisphenol A in milk and dairy products by high-performance liquid chromatography with fluorescence detection

This study was conducted to develop a selective and sensitive method for the determination of bisphenol A (BPA) levels in milk and dairy products. A method based on solvent extraction with acetonitrile and solid-phase extraction (SPE) was developed for the analysis of BPA in milk, yogurt, cream, butter, pudding, condensed milk, and flavored milk, and a method using two SPE cartridges (OASIS HLB and Florisil cartridge) for skim milk was also developed. The developed methods showed good recovery levels (77 to 102%) together with low detection limits (1 microg/liter for milk, yogurt, pudding, condensed milk, flavored milk, and skim milk and 3 microg/liter for cream and butter). These methods are simple, sensitive, and suitable for the analysis of BPA in milk and dairy products. When 40 milk and dairy products were analyzed by the proposed methods, BPA was not identified in noncanned products, but its levels ranged from 21 to 43 microg/kg in canned products, levels that were 60- to 140-fold lower than the migration limits in the European Union and Japan.     

Simple analysis of maleic hydrazide in agricultural products by HPLC

A simplified HPLC determination method for maleic hydrazide in agricultural products was developed, and commercial agricultural crops were investigated. The homogenate of agricultural products was extracted with water. The crude extract was purified on an ACCUCAT Bond Elut extraction cartridge using water. Maleic hydrazide was analyzed by HPLC with UV detection (303 nm). The HPLC separation was performed on a ZORBAX SB-Aq column with acetonitrile-water-phosphoric acid(5:95:0.01) as the mobile phase. Recoveries of maleic hydrazide from 15 agricultural products fortified at 1.0 and 10 micrograms/g were in the ranges of 92.6-104.9% and 94.2-101.3%, respectively. The limit of detection was 0.5 microgram/g in samples. The proposed method was applied to the determination of 242 commercial vegetables and fruits. Maleic hydrazide was detected in 2 samples of imported onion at the levels of 4.9 and 7.2 micrograms/g.     

Nitrate Analysis in Meats; Comparison of Two Methods

A high performance liquid chromatographic method (HPLC) was compared to cadmium reduction-Griess (Cd-Griess). Nitrate and nitrite were measured in fresh and cured meats. Nitrate levels by HPLC ranged from 6.2 to 26.7 nmol/g in fresh meats and from 124 to 3018 nmol/g in cured meats. Nitrate contents by HPLC were significantly higher (p<0.05) than those by Cd-Griess. Small amounts of nitrite (0–7.3 nmol/g) were detected in fresh meat samples by Cd-Griess. Results were similar to those used by the National Academy of Sciences to estimate human exposure to nitrate from fresh meats. Results from HPLC methods may provide more accurate estimates of human exposure to nitrate and nitrite.     

毛细管电泳技术在乳制品营养与安全分析中的应用

乳制品的营养与安全一直广受世界范围内的关注,各种色谱及色谱-质谱联用技术在乳制品分析中得到广泛应用。毛细管电泳技术在乳制品的营养与安全分析中独具特色,成为不可或缺的分析技术。本文围绕毛细管电泳技术分析乳及乳制品中乳糖和半乳糖、胆碱、5’-单磷酸核苷酸、硝酸盐和亚硝酸盐、山梨酸和苯甲酸等小分子化合物的方法,结合本实验室利用毛细管电泳技术参加能力验证等方面的工作,从营养成分、限量物质、残留分析、禁用物质、复原乳识别和能力验证这6个方面,对近10年来毛细管电泳技术在乳制品营养与安全分析中有代表性的应用研究及其进展进行总结,并对其在乳制品中小分子化学物质分析中的发展趋势进行了展望。