Spectroscopic quantifiication of preservatives in different food matrices using QuEChERS extraction and multivariate calibration with comparison against liquid chromatography

The application of QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction procedure has recently received significant attention, particularly for quantifying food additives in complex food matrices. A reliable analytical method based on QuEChERS extraction, UV spectroscopic measurement at 200–320 nm and partial least square regression PLS1 was outlined to determine two classes of preservatives in different processed food products. Examined additives were sodium benzoate SB, potassium sorbate PS, propylparaben PP, and methylparaben MP which showed highly overlapping UV spectra. The method indicated high detection of preservatives down to 1.1–2.4 mg/kg, recoveries between 97 and 102%, and RSD ≤ 7.0%. The efficient extraction of preservatives by QuEChERS from real matrices has improved the snentivity of spectral measurement and the detection of the analytical procedure. Methylparaben, MP, was detected in most samples with levels of 24.5, 74.3 and 393.7 mg/kg in liquid drinks, corn flakes, and soya sauce, respectively. The levels of preservatives were found to be within the regulated limits in all tested items. The outlined QuEChERS along with PLS1 calibration of spectroscopic data is proved to be a suitable alternative for liquid chromatography to monitor different types of preservatives in complex food matrices. The validity of the proposed method was checked against standard liquid chromatography.     

Rapid, Direct Quantitation of the Preservatives Benzoic and Sorbic Acid (and Salts) Plus Caffeine in Foods and Aqueous Beverages Using Supercritical Fluid Chromatography

The preservatives benzoate and sorbate, plus caffeine were rapidly separated and quantified, in just over 2 min, in a wide range of beverages and foods, using supercritical fluid chromatography (SFC). Fifteen beverages and 10 semi-liquid foods were evaluated. The benzoate and sorbate were originally present in the samples as the acid, or the sodium, or potassium salt. The aqueous samples were diluted 3:1 with acidified methanol, to insure the acids were protonated, then directly injected. The solutes were isocratically eluted from a 4 × 250 mm, 5 μm Diol column with 3.5 mL min^?1 of 8.5 % methanol containing 0.3 % acetic acid at 50 °C and a column outlet pressure of 150 bar. The real samples exhibited remarkably little interference. All the beverages were accurately labeled. However, many of the foods, such as salad dressings, mustard, etc., were mislabeled. The method was linear over a wide range with correlation coefficients for all three solutes >0.999. RSD’s were generally less than 1 %. The results agreed with the caffeine content on the labels within a few percent. Surprisingly, this appears to be the first published separation of benzoic and sorbic acid preservatives in food, and beverages using SFC, and one of a very few SFC applications where aqueous samples were simply diluted and injected. Compared to published references, the SFC method was found to be up to 7 times faster than HPLC, and eliminated the use of acetonitrile.     

Validation of a high-performance liquid chromatographic method for the simultaneous determination of tramadol and its impurities in oral drops as a pharmaceutical formulation

The novel, rapid high performance liquid chromatographic method for the determination of tramadol hydrochloride and its three impurities was developed and validated. The method can simultaneously assay potassium sorbate, used as preservative, and saccharin sodium, used as sweetener in tramadol pharmaceutical formulation. The separation was carried out on a C(18) XTerra (150 mm x 4.6 mm, 5 mm) column using acetonitrile-0.015 M Na(2)HPO(4) buffer (2:8, v/v) as mobile phase (pH value 3.0 was adjusted with orthophosphoric acid) at a flow rate 1.0 ml min(-1), temperature of the column 20 degrees C and UV detection at 218 nm. The method was found to be linear (r > 0.999) in the range of 0.05-0.8 mg ml(-1) for tramadol hydrochloride, 0.1-1.2 mg ml(-1) for impurities B and C and for impurity A (r > 0.995) in the range 0.15-2.4 mg ml(-1). The low RSD values indicate good precision and high recovery values indicate excellent accuracy of the HPLC method. Developed method was successfully applied to the determination of tramadol hydrochloride, its investigated impurities and potassium sorbate in commercial formulation. The recovery of tramadol hydrochloride was 98.25% and RSD was 1.80%. The method is rapid and sensitive enough to be used to analyse Trodon oral drops.     

高效毛细管电泳法同时测定药品中苯甲酸和山梨酸钾

建立了毛细管电泳-紫外检测法测定硝酸咪康唑乳膏、小儿止咳糖浆及复方苦参水杨酸散中苯甲酸和山梨酸钾的方法。在230nm波长处以焦性没食子酸为内标物,分离电压为20kV,分离温度为25℃,用20mmol/L硼砂缓冲液(pH9.2)作毛细管电泳的运行液,被测组分与内标物得到快速分离。苯甲酸和山梨酸钾的进样质量浓度在1～400mg/L范围内与电泳峰面积呈良好的线性关系,相关系数r均为0.9999,检出限均为0.15mg/L。方法可用于药品中苯甲酸和山梨酸钾含量的测定。     

Analytical monitoring of citrus juices by using capillary electrophoresis

A capillary electrophoretic method was developed to analyze simultaneously most citrus juice components in a single procedure. After filtration, sample components are separated with an uncoated capillary tubing and a 35 mM sodium borate buffer (pH 9.3) containing 5% (v/v) acetonitrile. Analyses were run at 21 kV and 23 degrees C. Compounds monitored regularly were the biogenic amine synephrine, some flavonoids (didymin, hesperidin, narirutin, neohesperidin, and naringin), the polyphenol phlorin, 3 UV-absorbing amino acids (tryptophan, phenylalanine, and tyrosine), ascorbic acid, an unidentified peak generated by heat and storage, and the preservatives sorbate and benzoate that can be added to citrus products. Separation can be achieved in 20 min, and each compound can be subsequently quantitated. Didymin, narirutin, and phlorin peaks were used with an artificial neural network to assess the volume of added pulp wash, a by-product of juice preparation. This method allows rapid monitoring of citrus juices, giving information on quality, freshness, and possible adulteration of the product. Similar procedures could be used to monitor other fruit juices and quantitate diverse juice blends.     

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.     

Simultaneous determination of sweeteners and preservatives in preserved fruits by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary method for the simultaneous determination of the sweeteners dulcin, aspartame, saccharin, and acesulfame-K and the preservatives sorbic acid; benzoic acid; sodium dehydroacetate; and methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutyl-p-hydroxybenzoate in preserved fruits is developed. These additives are ion-paired and extracted using sonication followed by solid-phase extraction from the sample. Separation is achieved using a 57-cm fused-silica capillary with a buffer comprised of 0.05 M sodium deoxycholate, 0.02 M borate-phosphate buffer (pH 8.6), and 5% acetonitrile, and the wavelength for detection is 214 nm. The average recovery rate for all sweeteners and preservatives is approximately 90% with good reproducibility, and the detection limits range from 10 to 25 microg/g. Fifty preserved fruit samples are analyzed for the content of sweeteners and preservatives. The sweeteners found in 28 samples was aspartame (0.17-11.59 g/kg) or saccharin (0.09-5.64 g/kg). Benzoic acid (0.02-1.72 g/kg) and sorbic acid (0.27-1.15 g/kg) were found as preservatives in 29 samples.     

Capillary electrochromatographic analysis of aliphatic mono- and polycarboxylic acids

The parameters influencing the electrochromatographic separation of aliphatic organic acids in a capillary column with a wall-coated macrocyclic polyamine have been studied. Indirect detection using chromate, pyromellitate, trimellitate, o-phthalate, benzoate and acetate as background electrolytes has been tested. A complete separation of polyprotic acids could be achieved with pyromellitate buffer (7.5 mM, pH 6.5), and satisfactory results for the simultaneous separation of monoprotic acids and polyprotic acids were found using a capillary column of 70 cm (50 cm effective length)x75 microm inner diameter, electrokinetic injection (-10 kV, 10 s), benzoate buffer (6 mM, pH 4.6), separation voltage of -10 kV, and detection at 220 nm. For the separation of the geometric isomers fumarate and maleate, acetate buffer was found the best choice among the background electrolytes tested. The method so established has been applied to the determination of organic acids in soy sauce, brandy, lemon juice, spinach juice and cigarette. From the retention behavior, it was found that the separation mechanism on the bonded phase was influenced by the macrocyclic effect, electrostatic attraction, hydrogen bonding, van der Waals forces, and anion exchange, in addition to the differences in electrophoretic mobility.     

Determination of naringin and neohesperidin in orange juice by liquid chromatography with UV detection to detect the presence of grapefruit juice: Collaborative Study

Fifteen collaborating laboratories were sent 9 samples of citrus juice mixtures as blind duplicates for determination of naringin and neohesperidin by liquid chromatography. Two sample pairs were 100% orange juice and did not contain any naringin or neohesperidin. The remaining 7 sample pairs contained naringin at levels ranging from 3.9 to 46.5 ppm and neohesperidin at levels ranging from 0.14 to 35.6 ppm. Five sample pairs consisted of orange juice mixtures containing 1, 3, and 5% grapefruit juice; 5% sour orange; and 5% K-Early citrus variety. Two sample pairs were orange juice spiked with naringin, neohesperidin, sodium benzoate, and potassium sorbate. Data were received from 13 laboratories. Data from 1 collaborator were eliminated because the method protocol was not followed. Neohesperidin values from another laboratory were also not used because of problems with a coeluting component. Repeatability relative standard deviations ranged from 2.95 to 15.23% for naringin and from 3.00 to 11.74% for neohesperidin. Reproducibility relative standard deviations ranged from 11.34 to 31.94% for naringin and from 10.45 to 26.17% for neohesperidin. The method is reliable for detecting the presence of grapefruit juice in orange juice as indicated by a finding of > or =10 ppm naringin and < or =2 ppm neohesperidin. The method was adopted First Action by AOAC INTERNATIONAL.     

Rapid determination of cyclamate in foods by solid-phase extraction and capillary electrophoresis

A method for the determination of cyclamate in food was developed using solid-phase extraction (SPE) and capillary electrophoresis (CE) with indirect ultraviolet (UV) detection. A 5-10 g sample in 0.1 mol/L hydrochloric acid was homogenized and made up to a volume of 50 mL with 0.1 mol/L hydrochloric acid. After the sample was centrifuged, 25 mL of supernatant was loaded into an Oasis HLB SPE cartridge. The cartridge was washed with 2 mL of demineralized water followed by 2 mL of 50% aqueous methanol, and cyclamate was eluted with 4.5 mL of 50% aqueous methanol. The eluate was added to a solution of sodium propionate (internal standard) for CE analysis. The cyclamate in the eluate was electrophoresed on a fused-silica capillary using 1 mmol/L hexadecyltrimethylammonium bromide and 10 mmol/L potassium sorbate as a running buffer. Detection and reference wavelengths of cyclamate determined with a UV detector were 300 and 254 nm, respectively. The calibration curves for cyclamate showed good linearity in the range of 2-1000 microg/mL and the limits of detection in beverage, fruit in syrup, jam, pickles and confectionary are sample dependent and ranged from 5-10 microg/g. The recovery of cyclamate added at a level of 200 microg/g to various kinds of foods was 93.3-108.3% and the relative standard deviation was less than 4.9% (n=3). A number of commercial samples were analyzed using the proposed method. Cyclamate was detected in one waume, two pickles, and two sunflower seeds. The quantitative values determined with CE correlated to those from high-performance liquid chromatography (HPLC) (the detected values of cyclamate in a sunflower seed measured by CE and HPLC were 3.40 g/kg and 3.51 g/kg, respectively). This analytical method for cyclamate using CE is especially suitable for use in the field.     

Simultaneous determination of nine UV filters and four preservatives in suncare products by high-performance liquid chromatography

HPLC method for quantitative determination of four preservatives and nine UV filters worldwide authorized in commercial suncare product was developed and validated, and then 101 samples of commercial suncare products were analyzed for the UV filters and preservatives using the proposed method. The mobile phase was acetonitrile-water containing 0.5% acetic acid using a gradient elution at a flow rate of 0.9 mL/min and UV measurements were carried out at 320 nm for UV filters and 254 nm for preservatives. The correlation coefficients of each calibration curves were mostly higher than 0.999. The percent relative standard deviations (%RSD) ranged from 0.97% to 6.1% for five sample aliquots. The recoveries from the spiked solutions were 98-102%. 2-ethylhexyl-p-methoxycinnamate (EHMC) was detected in 96 of 101 commercial suncare products and the concentration was in the range of 3.08-8.16% and 18 samples were found to exceed the 7.5% which has been defined as the maximum allowed concentration in Korea. Methyl paraben was detected in 81 of 101 samples and the next-most often detected preservatives were propyl paraben (25), ethyl paraben (18), and butyl paraben (4). Three samples of 101 suncare products exceeded the maximum allowed concentration (i.e., 0.58-0.79%). The proposed HPLC method allows efficient and simultaneous analysis of preservatives and UV filters suitable for quality control assays of commercial suncare products.     

高效液相色谱法测定强化食品中维生素C的含量

建立了强化食品(饮料、奶粉、含乳饮料、大米、果泥及果冻)中维生素C含量的高效液相色谱检测方法。优化了样品处理方法,在水浴控温和避光条件下处理样品,避免维生素C被氧化。选用Tech Mate C18–ST(250 mm×4.6 mm,5μm)反相色谱柱,以0.05 mol/L磷酸二氢钾缓冲溶液(p H 3)为流动相,流量为1.0m L/min,检测器为光电二极管阵列检测器,检测波长为266 nm。线性范围为0.2~100μg/m L,相关系数为0.999 6,果泥中维生素C的定量限为20 mg/kg,其它为100 mg/kg,加标回收率为82.2%~107%,测定结果的相对标准偏差为1.23%~6.86%(n=8)。该方法简单快速,其灵敏度、准确度和精密度均能满足强化食品中维生素C的检测要求。     

High performance liquid chromatographic determination of sodium benzoate, methylparaben and propylparaben as preservative components in nystatin suspensions

A simple and sensitive method was developed for the analysis of preservatives sodium benzoate, methylparaben and propylparaben in nystatin suspensions by reversed-phase high performance liquid chromatography (HPLC), equipped with a C18 column and PDA detector. The mobile phase was a mixture of acetonitrile and acetate buffer of pH 4.4 (35:65 v/v). Under the optimized experimental conditions, separation of the preservatives was achieved in less than 20 min. The limits of quantifications (LOQs) and the linear dynamic ranges (LDRs) of sodium benzoate, methylparaben and propylparaben were 0.3 and 50–1000 μg Ml^?1, 0.5 and 50–600 μg ml^?1 and 0.3 and 50–900 μg ml^?1, respectively; the respective precisions (%RSD) at 500 μg ml^?1 level were 0.72%, 0.73% and 0.51% (n = 6). The average recoveries of sodium benzoate, methylparaben and propylparaben for spiked nystatin samples were obtained as 98%, 97% and 98%, respectively.     

Determination of preservatives by integrative coupling method of headspace liquid-phase microextraction and capillary zone electrophoresis

An integrative coupling method of headspace liquid-phase microextraction (HS-LPME) and capillary zone electrophoresis (CZE) was proposed in this paper. In the method, a separation capillary was used to create a microextraction droplet of the running buffer solution of CZE, hold the droplet at the capillary inlet, extract analytes of sample solutions in the headspace of a sample vial, inject concentrated analytes into the capillary and separate the analytes by CZE. The proposed method was applied to determine the preservatives of benzoic acid and sorbic acid in soy sauce and soft drink samples, in which the running buffer solution of 50 mmol/L tetraborate (pH 9.2) was directly used to form the acceptor droplet at the capillary inlet by pressure, and the preservatives in a 6-mL sample solution containing 0.25 g/mL NaCl were extracted at 90°C for 30 min in the headspace of a 14-mL sample vial. Then the concentrated preservatives were injected into the capillary at 10 cm height difference for 20 s and separated by CZE. The enrichment factors of benzoic acid and sorbic acid achieved 266 and 404, and the limits of detection (LODs) were 0.03 and 0.01 μg/mL (S/N=3), respectively. The recoveries were in the range of 88.7-105%. The integrative coupling method of HS-LPME and CZE was simple, convenient, reliable and suitable for concentrating volatile and semi-volatile organic acids and eliminating matrix interferences of real samples.     

Rapid extraction of aflatoxin from creamy and crunchy peanut butter

A rapid extraction technique was developed for the isolation and subsequent liquid chromatographic determination of aflatoxins B1, B2, G1, and G2 in creamy and crunchy peanut butter. Peanut buftter samples were extracted with a methanol 15% sodium chloride (7 + 3) solution followed by a second extraction with methanol. The extract was subjected to a cleanup using a Vicam Aflatest immunoaffinity column. Control samples for both smooth and crunchy peanut butter were fortified at 4 different levels for aflatoxin B1, B2, G1, and G2. The average aflatoxin B1, B2, G1, and G2 recoveries from smooth peanut buffer were 95.2, 89.9, 94.1, and 62.4%, respectively, and 92.4, 84.3, 85.5, and 53.7%, respectively, from crunchy peanut butter. This extraction method and the official AOAC Method 991.31 produced comparable results for peanut butter samples. This method provides a rapid, specific, and easily controlled assay for the analysis of aflatoxins in peanut butter with minimal solvent usage. Organic solvent consumption was decreased by 85% and hazardous waste production was decreased by 80% in comparison with the AOAC method. Along with the decreased solvent consumption, significant savings in time were observed.     

非线性优化迭代-紫外分光光度法同时测定苯甲酸钠和山梨酸钾

提出一种用连续波长的紫外光谱吸光度数据对两组分防腐剂（苯甲酸钠、山梨酸钾）混合物体系的定量分析方法。该方法利用连续波长信息将摩尔吸光系数和待测浓度同时作为自变量,建立非线性优化模型,对于组分浓度差较小的混合物体系经一次优化分析计算可得待测浓度;混合物中浓度差较大的体系经四次左右优化迭代,逐步降低误差得分析结果,相对误差可控制在1．52％之内。分析结果表明该法稳定、准确、简便快速、实用灵活,可对食品防腐剂进行定量测定。     

Determination of total soy isoflavones in dietary supplements, supplement ingredients, and soy foods by high-performance liquid chromatography with ultraviolet detection: collaborative study

An interlaboratory study was conducted to evaluate a method for determining total soy isoflavones in dietary supplements, dietary supplement ingredients, and soy foods. Isoflavones were extracted using aqueous acetonitrile containing a small amount of dimethylsulfoxide (DMSO) and all 12 of the naturally occuring isoflavones in soy were determined by high-performance liquid chromatography (HPLC) with UV detection using apigenin as an internal standard. Fifteen samples (6 pairs of blind duplicates plus 3 additional samples) of soy isoflavone ingredients, soy isoflavone dietary supplements, soy flour, and soy protein products were successfully analyzed by 13 collaborating laboratories in 6 countries. For repeatability, the relative standard deviations (RSDr) ranged from 1.07 for samples containing over 400 mglg total isoflavones to 3.31 for samples containing 0.87 mg/g total isoflavones, and for reproducibility the RSDR values ranged from 2.29 for samples containing over 400 mg/g total isoflavones to 9.36 for samples containing 0.87 mg/g total isoflavones. HorRat values ranged from 1.00 to 1.62 for all samples containing at least 0.8 mg/g total isoflavones. One sample, containing very low total isoflavones (< 0.05 mg/g), gave RSDR values of 175 and a HorRat value of 17.6. This sample was deemed to be below the usable range of the method. The method provides accurate and precise results for analysis of soy isoflavones in dietary supplements and soy foods.     

Single-laboratory validation of a method for the determination of furan in foods by using static headspace sampling and gas chromatography/mass spectrometry

A headspace gas chromatography/mass spectrometry method was developed and validated in-house for the determination of furan in foods. The method of standard additions with d4-furan as the internal standard was used to quantitate furan. The limit of detection and limit of quantitation (LOQ) values ranged from 0.2 and 0.6 nglg, respectively, in apple juice to 0.9 and 2.9 ng/g, respectively, in peanut butter. Recoveries were obtained at 0.5, 1, 2, and 3 times the LOQ. At 1, 2, and 3 times the LOQ, the recoveries ranged from 89.4 to 108%, and the relative standard deviations ranged from 3.3 to 17.3% for all the matrixes. For apple juice, chicken broth, and infant formula, the averaged coefficients of determination from the linear regression analyses were >0.99 with each food fortified at 0.5, 1, 2, and 3 times the LOQ. The coefficients of determination were >0.99 for green beans and 0.96 for peanut butter with the foods fortified at 1, 2, and 3 times the LOQ. Within-laboratory precision was determined by comparing the amounts of furan found in 18 samples by 2 analysts on different days with different instruments. For most of the foods, the difference between the amounts found by each analyst was <18%. The method was used to conduct a survey of >300 foods. The furan levels found ranged from none detected to 174 ng/g.     

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.     

Detection of Sulfamethazine Residues in Milk by High Performance Liquid Chromatography

Abstract

A simple high performance liquid chromatographic (HPLC) procedure for the detection of sulfamethazine residues in milk is described. Milk is extracted with chloroform, the extract evaporated to dryness and then redissolved in potassium phosphate buffer (pH 5.0). The chloroform extract, in buffer, is passed through a cyclobond I solid phase extraction (SPE) column. The SPE column is washed with 10 ml potassium phosphate buffer and then sulfamethazine is eluted with 2 ml aqueous (50%) methanol. The eluent is directly analyzed by HPLC with uv detection at 265 nm. The recoveries ranged from 83.2% to 88.2% in samples fortified between 5 to 40 ppb levels.