Determination of glycyrrhizin in liqueurs by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

An on-line coupled capillary isotachophoresis-capillary zone electrophoresis method for the determination of glycyrrhizin in liqueurs is described. The optimised electrolyte system was 5 mM HCl+11 mM varepsilon-aminocaproic acid+0.05% hydroxyethylcellulose+30% methanol (leading electrolyte), 5 mM caproic acid+30% methanol (terminating electrolyte) and 20 mM caproic acid+10 mM histidine+0.1% hydroxyethylcellulose+30% methanol (background electrolyte). Method characteristics, i.e., linearity (20-500 ng/ml), accuracy (recovery 99+/-4%), intra-assay repeatability (2%), intermediate repeatability (3.8%) and detection limit (8 ng/ml) were determined. Speed of analysis, low laboriousness, high sensitivity and low-running cost are the typical attributes of the capillary isotachophoresis-capillary zone electrophoresis method. Developed method was successfully applied to analysis of liqueurs with liquorice extract and some foods (sweets and food supplements) containing liquorice. Found levels of glycyrrhizin in liqueurs, sweets and food supplements varied between 1-16 mg/l, 850-1050 mg/kg and 1.6-1.8 g/kg, respectively.     

Determination of domoic acid by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

An on-line coupled capillary isotachophoresis--capillary zone electrophoresis (cITP-CZE) method for the determination of domoic acid in shellfish and algae is described. The optimised cITP-CZE electrolyte system was 10 mM HCl + 20 mM beta-alanine (BALA) + 0.05% hydroxyethylcellulose (leading electrolyte), 5 mM caproic acid (terminating electrolyte) and 20 mM caproic acid + 20 mM BALA + 0.1% HPMC (background electrolyte). A clear separation of the domoic acid from the other components of methanolic sample extract was achieved within 25 min. Method characteristics, i.e., linearity (0-200 microg/l), accuracy (recovery 101+/-3%), intra-assay repeatability (2.4%) and detection limit (1.5 microg/l) were determined. Speed of analysis, low laboriousness, high sensitivity and low running cost are the typical attributes of the cITP-CZE method. Developed method was successfully applied to analysis of shellfish samples and food supplements containing algae extract.     

超高效液相色谱-串联质谱法测定茶叶中游离氨基酸成分

建立了使用超高效液相色谱-串联质谱（UHPLC-MS/MS）高效、快速直接测定茶叶中游离氨基酸的方法。通过对质谱、色谱条件及氨基酸提取条件的优化，以含0.2%（体积分数）甲酸的5 mmol/L乙酸铵水溶液和甲醇为流动相进行梯度洗脱，在电喷雾离子（ESI）源正离子扫描模式下检测，通过UHPLC-MS/MS测定，共解析了茶叶中的20种氨基酸。结果表明，茶氨酸（Thea）、Arg、Asn和Asp在50~500 μg/L范围内线性关系良好，其他氨基酸在10~250 μg/L范围内线性关系良好，相关系数均大于0.99；加标回收率为92.3%~109.2%，相对标准偏差为2.00%~9.88%，检出限为0.001~0.011 mg/L，定量限为0.010~0.053 mg/L。该方法灵敏、准确，具有良好的重复性和稳定性，可有效检测出茶叶中的20种氨基酸及氨基类成分。     

Rapid analysis of amino acids in Japanese green tea by microchip electrophoresis using plastic microchip and fluorescence detection

Microchip electrophoresis for the short-time analysis of amino acids in Japanese green tea was developed. The amino acids in Japanese green tea were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). The derivatives were filtered and directly analyzed by electrophoresis on a plastic microchip with a 31-mm long separation channel with fluorescence detection. Amino acid analysis of Japanese green tea was improved by removing polyphenols using a polyvinylpolypyrrolidone pretreatment. Elution profiles of NBD-amino acids were examined under different running buffer conditions, and the sodium dodecyl sulphate in the running buffer exhibited a dramatically high-separation efficiency of amino acids by inhibiting their adsorption on the channel walls. Under the optimized conditions (5 mM phosphate buffer (pH 5.5) containing 0.05 mM sodium dodecylsulfate as running buffer), the main amino acids contained in Japanese green tea were well separated within 2 min, and theanine (1475 mg/100 g tea leaf), Arg (408 mg/100 g tea leaf) and Gln (217 mg/100 g tea leaf) were detected in Japanese green tea.     

手性衍生-高效液相色谱法拆分和定量测定茶氨酸对映体

建立了以1-氟-2,4-二硝基苯基-5-L-丙氨酰胺（FDAA）为手性衍生试剂、高效液相色谱拆分茶氨酸对映体的方法。采用的色谱条件为：Kromasil C18色谱柱;三乙胺-磷酸缓冲液和乙腈为流动相,梯度洗脱，流速1.0 mL/min;检测波长为340 nm;柱温为35 ℃。L-茶氨酸的进样量在1.732×10-3～2.077 μg范围内峰面积与进样量之间的线性关系良好，加标回收率为97.3%～102.0%,检测限为4.973×10-4 μg,定量限为1.223×10-3 μg。D-茶氨酸的进样量在1.696×10-3～2.044 μg范围内峰面积与进样量之间的线性关系良好,加标回收率为97.2%～103.2%,检测限为5.871×10-4 μg,定量限为1.236×10-3 μg。该方法灵敏度高,分析过程中不发生消旋化。     

Selectivity control in the non-aqueous capillary electrophoretic separation of amino acids

The separation of dansylated amino acids and underivatized amino acids in non-aqueous electrolytes was evaluated with direct and indirect UV detection. Different migration orders were achieved for dansylated amino acids in methanol compared to aqueous electrolyte systems. A reversed migration order was observed for some dansylated amino acids. Separation selectivity was different under acidic and basic conditions and was also a function of the solvation properties of the solvent. Underivatized amino acids were separated in basic and acidic electrolytes in methanol; different separation selectivities and, for some amino acids, a reversed migration order were also observed in these electrolyte systems. Analytical merits of the separation of both derivatized and underivatized amino acids were briefly evaluated; detection limits for dansylated amino acids were in the range of 2·10⁻⁷–4·10⁻⁷ mol/l and, for underivatized amino acids, were 2·10⁻⁶–4·10⁻⁵ mol/l.     

Determination of egg white lysozyme by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

An on-line coupled capillary isotachophoresis - capillary zone electrophoresis method for the determination of lysozyme in selected food products is described. The optimized electrolyte system consisted of 10 mM NH(4)OH + 20 mM acetic acid (leading electrolyte), 5 mM epsilon -aminocaproic acid +5 mM acetic acid (terminating electrolyte), and 20 mM epsilon -aminocaproic acid +5 mM acetic acid +0.1% m/v hydroxypropylmethylcellulose (background electrolyte). A clear separation of lysozyme from other components of acidic sample extract was achieved within 15 min. Method characteristics, i.e., linearity (0-50 micrograms/mL), accuracy (recovery 96+/-5%), intra-assay (3.8%), quantification limit (1 microgram/ml), and detection limit (0.25 microgram/mL) were determined. Low laboriousness, sufficient sensitivity and low running costs are important attributes of this method. The developed method is suitable for the quantification of the egg content in egg pasta.     

QuEChERS净化-液相色谱-串联质谱法测定茶叶中氯噻啉

建立了茶叶中农药氯噻啉残留的液相色谱-串联质谱检测方法。茶叶样品用乙腈提取,提取液经QuEChERS法净化,利用PSA(N-丙基乙二胺)、C₁₈、GCB(石墨化炭黑)等吸附剂材料进一步去除杂质,净化液经过离心后取上清液以水等体积稀释。以乙腈-0.1%(v/v)甲酸水溶液为流动相,在0.30 mL/min流速下梯度洗脱,用C₁₈色谱柱进行液相色谱分离,电喷雾正离子模式电离(ESI⁺),选择反应监测(SRM)模式检测,外标法定量。结果表明:氯噻啉在1~500 μ g/L范围内线性关系良好(相关系数r为0.9999),定量限为0.01 mg/kg(S/N≥10),在乌龙茶和绿茶中3个添加水平(0.01、0.3和3 mg/kg)的平均回收率为87.0%~101.0%,相对标准偏差(RSD, n=7)在2.1%~13.1%之间。对多种茶叶的测定结果表明,该方法操作简便、成本低、准确性高、特异性好、分析速度快,可以对茶叶中氯噻啉残留进行定性和定量检测。     

Direct UV detection of underivatized amino acids using capillary electrophoresis with online sweeping enrichment

This is an original report proposed a CE method for direct analysis of the underivatized amino acids using UV detection with relatively higher sensitivity, which was based on coordination interactions between amino acids and Cu (II) ions. In addition, an online sweeping preconcentration technique was easily combined to improve the detection sensitivity. Satisfying separations of the amino acids were obtained under optimized conditions: 50 mmol/L CuSO₄–0.05% HAc–H₂O (pH 4.5), and the separation voltage of 15 kV. The LODs for the analytes ranged from 0.1 to 0.5 μmol/L. The linearity of detection for all analytes was two orders of magnitude with the correlation coefficients greater than 0.99. The repeatability was displayed with an RSD less than 3% for migration time and peak height (n = 5). Moreover, some amino acids in real samples of human saliva and green tea were analyzed by this direct UV detection CE method with acceptable sensitivity.     

Determination of cobalt in the presence of high concentrations of zinc by differential pulse polarography

Summary Cobalt(II) can be determined in 0.1 mol/l Na₃citrate + 0.1 mol/l NH₄Cl + 0.08% dimethylglyoxime as supporting electrolyte in the presence of a 50 000-fold excess of zinc by differential pulse polarography. The limit of determination is 4.2×10^–5 mol/l Co (2.5 mg/l). Linear calibration curves are obtained within the range of 1×10^–7 to 5×10^–6 mol/l cobalt without zinc and in the presence of 5×10^–3 mol/l Zn. The analytical method developed is suitable for the determination of cobalt in zinc plant solutions.

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Cobaltbestimmung in Gegenwart hoher Zinkkonzentrationen mit Hilfe der Differential-Puls-Polarographie

     

Determination of biogenic amines by capillary zone electrophoresis with conductometric detection

A capillary zone electrophoresis (CZE) method with conductometric detection of biogenic amines (cadaverine, putrescine, agmatine, histamine, tryptamine and tyramine) is described. The optimised background electrolyte was the following: 15 mM histidine + 5 mM adipic acid + 1.5 mM sulphuric acid + 0.1 mM ethylenediaminotetraacetic acid + 0.1% hydroxyethylcellulose + 50% methanol. A clear separation of six biogenic amines from other components of acidic sample extract was achieved within 10 min. Method characteristics, i.e., linearity (0-100 micromol/ml), accuracy (recovery 86-107%), intra-assay repeatability (2-4%), and detection limit (2-5 micromol/l) were evaluated. Low laboriousness, sufficient sensitivity, speed of analysis, and low running cost are important attributes of this method. The developed method was successfully applied on the determination of biogenic amines in selected food samples.     

Protective Effects of L-Theanine on IPEC-J2 Cells Growth Inhibition Induced by Dextran Sulfate Sodium via p53 Signaling Pathway

L-theanine is a nonprotein amino acid found in tea leaves and has been widely used as a safe food additive in beverages or foods because of its varied bioactivities. The aim of this study was to reveal the in vitro gastrointestinal protective effects of L-theanine in DSS-induced intestinal porcine enterocyte (IPEC-J2) cell models using molecular and metabolic methods. Results showed that 2.5% dextran sulfate sodium (DSS) treatment inhibited the cell proliferation of IPEC-J2 and blocked the normal operation of the cell cycle, while L-theanine pretreatment significantly preserved these trends to exert protective effects. L-theanine pre-treatment also up-regulated the EGF, CDC2, FGF2, Rb genes and down-regulated p53, p21 proliferation-related mRNA expression in DSS-treated cells, in accompany with p53 signaling pathway inhibition. Meanwhile, metabolomics analysis revealed that L-theanine and DSS treated IPEC-J2 cells have different metabolomic profiles, with significant changes in the key metabolites involved in pyrimidine metabolism and amino acid metabolism, which play an important role in nucleotide metabolism. In summary, L-theanine has a beneficial protection in DSS-induced IPEC-J2 cells via promoting proliferation and regulating metabolism disorders.     

Differentiation of Al3+ and Al species in environmental samples by isotachophoresis

An isotachophoretic method for the determination of free [Al(H2O)6]3+ ions in different aluminium salt solutions was developed. The electrolyte system consists of 0.01 M sodium acetate (leading system) and 0.01 M tris(hydroxymethyl)amino-methane (terminating system). Separation was effected with a precapillary tube (diameter 0.05 cm) followed by a main capillary tube of length 20 cm and of smaller cross-section. The detection limit for [Al(H2O)6]3+ ions was 0.05 mg/l. The method was applied to the determination of free Al3+ ions ([Al(H2O)6]3+) in soil leachates and aqueous soil extracts.     

Determination of potassium in sea-water by capillary isotachophoresis

Summary A new analytical procedure for the determination of potassium in sea-water was developed using capillary isotachophoresis and ion-exchange. After the sea-water sample was passed through the column packed with an ammonium form cation-exchange resin, sodium ion was removed with 2×10^–2 mol/l ammonium chloride solution and then potassium ion was eluted with 3×10^–1 mol/l ammonium chloride solution. Simultaneous determination of potassium and sodium ions was performed with a newly developed electrolyte system; the leading electrolyte was 5 mmol/l cesium hydroxide containing 2 mmol/l 18-crown-6, 0.01% hydroxypropyl methylcellulose (HPMC) and 70% methanol; the terminating electrolyte was 5 mmol/l tetrabutylammonium bromide containing 0.01% HPMC and 70% methanol. A large amount of ammonium in the eluate did not interfere with the isotachophoretic measurement of potassium and sodium ions. A linear working curve was obtained for artificial sea-water samples containing up to 700 mg/l potassium ion. The proposed method was applied to the determination of potassium in surface and bottom sea-water samples.

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Kaliumbestimmung in Meereswasser durch Capillar-Isotachophorese

     

毛细管电泳高频电导法快速分离检测混合氨基酸

氨基酸(Am ino acids,AA s)是组成生物大分子的基本单元,与人的健康状况有极其密切的关系.在医学和生命科学研究中,微量氨基酸的分离检测具有重要意义.     

超高效液相色谱-高分辨质谱联用结合整合过滤策略全面分析茶树花中化学成分

茶树花与茶鲜叶同为茶树的生物产出,但茶树花往往被视为茶叶生产过程中的废物被舍弃,造成了茶树花资源的极大浪费.目前对于茶树花中化学成分的分析主要集中在氨基酸、茶多酚等单一类型化学成分上,对于茶树花中多类化学成分的同时分析仍鲜见报道.研究者对于茶树花中所含化学成分的种类和含量不完全清楚,成为制约茶树花深度开发与利用的重要原...     

聚氯乙烯膜修饰碳微电极的研制及应用

采用浸涂流延法制得ＰＶＣ膜修饰碳微电极,用Ｋ３Ｆｅ（ＣＮ）６的循环伏安图考察了电极的电化学性能,并用此电极建立了环境水样中痕量汞的阳极溶出伏安法测定。在０．０６ｍｏｌ／Ｌ ＫＳＣＮ＋０．０１ｍｏｌ／ＬＫＣｌ介质中,富集电位－０．８０Ｖ,搅拌富集时间３００ｓ,扫描电压范围－０．２０～０．４０Ｖ,扫描速率３１４ｍＶ／ｓ,咄峰电流与Ｈｇ＾２＋浓度在０．０１～２．０ｍｇ／Ｌ的范围内有良好的线性关系,本电极     

双水杨醛邻苯二胺柱前衍生-高效液相色谱法测定茶叶中的Pb~(2+)

建立了利用双水杨醛邻苯二胺希夫碱(SALOPHEN)作为衍生剂结合高效液相色谱(HPLC)测定茶叶中Pb~(2+)含量的方法。Hypersil ODS2 C18反相色谱柱(250 mm×4.6 mm,5μm)为固定相,甲醇-水(80∶20,v/v)为流动相,检测波长为226 nm,反应体系pH为10.0。结果表明,样品中Pb~(2+)的线性范围为0.1~30 mg/L,线性相关系数为0.998 8,检出限为0.01 mg/L,加标回收率为91.87%~96.96%。该方法具有较高的灵敏度和稳定性,适用于茶叶中Pb~(2+)的检测。     

Combining bar adsorptive microextraction with capillary electrophoresis—Application for the determination of phenolic acids in food matrices

In this contribution, bar adsorptive microextraction coated with a mixed‐mode anion exchange/RP followed by liquid desorption was combined for the first time with a capillary electrophoresis‐diode array detection system (BAμE(MAX)‐LD/CE‐DAD), for the determination of phenolic acids in food matrices, using chlorogenic, ferulic, cumaric, and caffeic acids as model compounds. Assays performed in aqueous media spiked at the 0.8 mg/L level yielded average recoveries up to 40% for all four phenolic acids, under optimized experimental conditions. The analytical performance showed also good precision (RSD < 15%), convenient LODs (18.0–85.0 μg/L) and linear dynamic ranges (0.8–8.0 mg/L) with convenient determination coefficients (r² > 0.9900). By using the standard addition method, the application to food matrices such as green tea, red fruit juice, and honey allowed very good performances for the determination of minor amounts of phenolic acids. The proposed methodology proved to be a suitable alternative for the analysis of polar to ionic compounds, showing to be easy to implement, reliable, sensitive, and requiring a low sample volume to determine phenolic acids in food samples.     

Amperometric detection of amino acids in a flow-injection system with a nickel(II)-modified electrode with an Eastman-AQ polymer film

Amperometic flow measurements were made at +0.55 V (vs. Ag/AgCl) in 0.1 mol l⁻¹ KOH electrolyte with an Ni(II) chemically modified electrode (CME) with an Eastman-AQ polymer film. The use and characteristics of a Ni(II)-containing crystalline and polymer-modified electrode obtained by a double coating step as a detector for amino acids in a flow-injection system using reversed-phase liquid chromatography are described. The detection of these analytes is based on the higher oxidation state of nickel (NiOOH) controlled by the applied potential. The electroanalytical parameters and the detection current for a series of amines and amino acids were investigated. The use of such a CME in the flow-injection technique was found to be suitable in a solution at low pH. The linear range for glycine is 5 × 10⁻⁶-0.1 mol l⁻¹ with a detection limit of 1.0×10⁻⁶ mol l⁻¹. A 1 × 10⁻⁴ mol l⁻¹ mixture of serine and tyrosine was also detected after separation on an Nucleosil C₁₈ column.