离子转换色谱-紫外检测法测定啤酒中的无机阴离子和有机酸

建立了离子转换色谱与紫外检测器联用检测啤酒中无机阴离子与有机酸的新方法。在传统的离子色谱基础上引入两根离子转换柱,无机阴离子与有机酸经过两步转换,定量转换成有相同紫外响应的碘酸盐,然后用紫外检测器代替电导检测器进行定量分析。在Dionex AS11-HC阴离子色谱柱上,采用KOH梯度淋洗方式实现了12种无机阴离子与有机酸的分离。结果表明,12种无机阴离子和有机酸检出限（S/N=3）与定量限（S/N=10）分别为6.168~29.01 μg/L与20.56~66.30 μg/L;线性关系良好（r在0.9994以上）,回收率为89.0%~117.0%,RSD均小于1.0%,该方法与传统的电导检测器检测结果相当。该方法简单快捷,只需采用少数标准曲线,就可以实现啤酒中无机离子与有机酸的定量测定。     

食品中有机酸的高效液相色谱分析法

对离子交换色谱法、离子排斥色谱法和反相高效液相色谱法分析食品中有机酸的特色和近几年的研究与应用状况作一综述。     

离子交换色谱法同时测定啤酒中有机酸和无机阴离子

建立了用亲水性阴离子交换分离柱,KOH为淋洗液等浓度泵作梯度淋洗,电导检测,同时分离和检测16种无机阴离子和低分子量有机酸的离子色谱法。方法对所测无机阴离子和有机酸检出限在9．3～32μg/L之间;线性范围均在2个数量级以上;回收率在90．2％～107．2％之间。方法用于啤酒样品的分析,结果满意,样品的RSD小于5．3％(n=7)。     

Ion chromatographic determination of some organic acids, chloride and phosphate in coffee and tea

An ion chromatographic method for the simultaneous determination of organic acids and inorganic ions is described. Acetic, malic, ascorbic, citric, malic and succinic acids, chloride and phosphate were determined in coffee and tea samples. The separation is performed on an anion-exchange column operated at 40 °C within 25 min by an isocratic elution with 0.6 mM aqueous potassium hydrogenphthalate (pH 4.0) solution containing 4% (v/v) acetonitrile as eluent and determination by conductivity detection. The method does not need a special sample treatment and was successfully applied to the analysis of black, green and oolong tea samples. Also, green and roasted coffee samples from the varieties arabica and robusta were analyzed.     

Application of co-electroosmotic capillary electrophoresis for the determination of inorganic anions and carboxylic acids in soil and plant extract with direct UV detection

Summary Indirect UV detection in capillary zone electrophoresis (CZE) is frequently used for the determination of inorganic anions and carboxylic acids. However, there are few reports on direct UV detection of these solutes in real samples. This paper describes the use of direct UV detection of inorganic anions and organic acids in environmental samples using co-electroosmotic capillary zone electrophoresis (co-CZE) at 185 nm. The best separation and detection of the solutes was achieved using a fused silica capillary with an electrolyte containing 25 mM phosphate, 0.5 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile (v/v) at pH 6.0. Four common inorganic anions (Cl⁻, NO₂ ⁻, NO₃ ⁻ and SO₄ ²⁻) and 11 organic acids (oxalic, formic, fumaric, tartaric, malonic, malic, citric, succinic, maleic, acetic, and lactic acid), were determined simultaneously in 15 min. Linear calibration plots for the test solutes were obtained in the range 0.02–0.5 mM with detection limits ranging from 1–9 μM depending on the analyte. The proposed method was successfully used to determine inorganic anions and carboxylic acids in soil and plant tissue extracts with direct injection of the sample.     

Separation of unmodified α-amino acid enantiomers by reverse phase HPLC

Summary A novel chiral phase system is presented for the resolution of unmodified α-amino acid racemates which is composed of a reverse phase packing coated with N-alkyl-L-hydroxyproline (where alkyl is n-C₇H₁₅-, n-C₁₀H₂₁- and n-C₁₆H₃₃-) and a hydro-organic eluent containing copper(II)acetate. The factors controlling retention and enantioselectivity such as concentration of Cu(II)ion and pH of the eluent, addition of NH₄Ac to the eluent, type and content of organic solvent of hydro-organic eluent and column temperature were examined. The extremely high enantioselectivity observed (α up to 16) is assumed to be caused by a three site sorbate-sorbent interaction involving bidentate coordination of two amino acids to a Cu(II)ion and hydrophobic attractions between hydrocarbon side chains of amino acids and the n-octadecyl groups of the support. The efficiency and selectivity of the system permits resolution of up to 7 racemic amino acids into enantiomers within 35 minutes on a conventional HPLC apparatus. 13th publication in the series dealing with the ligand-exchange chromatography. Previous publication: ref. [1].     

固相萃取-离子色谱法测定甘蔗糖蜜及糖蜜酒精废液中的非氮有机酸和无机阴离子

建立了固相萃取-离子色谱测定甘蔗糖蜜及糖蜜酒精废液中乙酸、乳酸、琥珀酸、苹果酸、酒石酸、草酸、富马酸、柠檬酸、乌头酸等非氮有机酸和盐酸根、硫酸根、磷酸根等3种无机阴离子的方法。样品稀释液经强阴离子(SAX)固相萃取小柱净化除去糖类和色素等干扰基质,再用稀KOH溶液洗脱,经0.45 μm水膜过滤后,用IonPac AS15阴离子分离柱、KOH溶液梯度淋洗-抑制电导检测分离分析。考察了固相萃取小柱对待测离子的保留和洗脱条件。实验结果表明,除乙酸和乳酸的分离不完全、苹果酸与琥珀酸的组分重叠外,其余组分可达到完全分离,被测组分的浓度与其峰高在一定的范围呈良好的线性关系,检出限均低于0.20 mg/L,相对标准偏差(RSD)小于6.7%。测定了2种甘蔗糖蜜和1种糖蜜酒精废液中有机酸及无机阴离子,结果满足检测的要求,样品中各组分的加标回收率为94%～109%。     

Determination of water-soluble inorganic and organic species in atmospheric fine particulate matter

The use of ion chromatography (IC) in conjunction with ultrasonic extraction is described for the routine analysis of water-soluble major inorganic ions and organic acids in atmospheric fine particles (PM_2.5). Both the extraction method and the IC analysis were validated using NIST SRM 1648 (urban particulate matter). In addition, the reliability of the IC method was established by intercomparison of results obtained with those from suitable alternative analytical techniques (atomic absorption spectrometry (AAS), proton-induced X-ray emission (PIXE) spectrometry, and UV-Visible spectrophotometry). The validated IC method was successfully applied for field monitoring of PM_2.5 particles collected in Singapore over an extended period of time. The IC analysis revealed that the concentrations of individual ions were in the order, SO₄²⁻ > NH₄⁺ > NO₃⁻ > Na⁺ > K⁺ > Cl⁻, respectively. Among the major ionic components, SO₄²⁻ contributed 50% to the measured water-soluble aerosol mass followed by NH₄⁺ (16.5%) and NO₃⁻ (9.0%). The cations Na⁺, K⁺, Mg²⁺, and Ca²⁺ accounted for 24% of the total water-soluble mass. The IC analysis was performed to quantify the organic acids, which typically account for a small fraction of water-soluble organic compounds in PM_2.5. Oxalate was found to be the dominant species among the organic acids measured in this work.     

Densitometric determination of unsaturated fatty acids with p-hydroxybenzaldehyde by HPTLC

A rapid method for the detection and quantltatlve determlnation of unsaturated fatty acids by TLC is presented. After separation on HPTLC-RP₁₈-plates, reaction wlth p-hydroxybenzaldehyde is carried out by a dipping procedure. Nanogram amounts of unsaturated fatty acids can be determined with good reproducibility.     

High-performance liquid chromatographic determination of major organic acids in apple juices and ciders

Summary A reversed-phase high-pressure liquid chromatographic method is presented for the simultaneous separation and determination of malic, citric, lactic, succinic and ascorbic acids in apple juices and ciders. After filtration and/or degasification, the organic acids in the sample are separated on a LiChrosorb/C₁₈ column and quantified by using a rapid diode array detector. The method is considered to be a suitable choice for the accurate and precise determination (C.V. 5%) of these compounds.     

Relative efficiencies of substituted aromatic monocarboxylic acids as eluents in ion chromatographic separation of inorganic and organic anions

The eluent strengths of para, ortho and meta substituted hydroxy-, nitro-, amino- and sulfobenzoic acids in single column ion chromatographic separations of inorganic and organic anions have been evaluated and compared with benzoic acid.o-Sulfobenzoic acid turns out to be a stronger and efficient eluent compared to others for the separation and determination of monovalent (Cl^–, NO ₂ ^– , Br^–, NO ₃ ^– ) and divalent (SO ₄ ^2– , SeO ₄ ^2– , S₂O ₃ ^2– , S₂O ₆ ^2– ) inorganic anions. In addition it also functions as an appropriate mobile phase for the detection and quantification of some substituted benzoate ions in an aqueous medium.     

Determination of organic acids in air by capillary electrophoresis and ion-exclusion chromatography

Summary A capillary electrophoretic (CE) method for the determination of organic acids in the low ppm range is described. The buffer consisted of 5 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium bromide, pH 5.6. The former served as background electrolyte for indirect UV detection at 200 nm, whereas the latter was used to reverse electroosmotic flow. In <5 min 8 low molecular mass organic acids (oxalic, formic, malonic, glutaric, glycolic, acetic, lactic and propanoic) and two inorganic acids (hydrochloric and sulphuric) were separated. Detection limits for anions tested were 0.04 mg L⁻¹ (lactic acid) to 0.6 mg L⁻¹ (malonic acid). The method was applied to the determination of organic acids in air samples. The CE results when compared with ion-exclusion chromatography (IEC) agreed well. The use of electrokinetic injection in CE proved beneficial for preconcentration of organic acids in real samples. Using electrokinetic injection, preconcentration factors ranging from 14 (hydrochloric acid) to 3 (propanoic acid) were obtained. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

单柱阴离子色谱法同时测定无机阴离子、无机阳离子和有机酸的研究

自Small等首次采用双柱阴离子色谱法测定无机阴离子以来,单柱阴离子色谱法已被用于测定无机阴离子、有机酸,并利用金属阳离子与EDTA形成的阴离子配合物分离测定阳离子。但用单柱阴离子色谱法同时测定无机阴离子、无机阳离子和有机酸尚未见报道。本文采用EDTA为淋洗液的单柱阴离子色谱法研究了无机阴离子、无机阳离子和有机酸的同时分析测定。     

Determination of trans-fatty acids in food samples based on the precolumn fluorescence derivatization by high performance liquid chromatography

Trans-fatty acids are unsaturated fatty acids that are considered to have health risks. 1,3,5,7-Tetramethyl-8-butyrethylenediamine-difluoroboradiaza-s-indacene is a highly sensitive fluorescent labeling reagent for carboxylic acids developed by our lab. In this study, using this precolumn fluorescent derivatization reagent, a rapid and accurate high-performance liquid chromatography with fluorescence detection method was developed for the determination of two trans-fatty acids in food samples. Under the optimized derivative conditions, two trans-fatty acids were tagged with the fluorescent labeling reagent in the presence of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide at 25°C for 30 min. Then, the baseline separation of trans- and cis-fatty acids and their saturated fatty acid with similar structures was achieved with less interference using a reversed-phased C₁₈ column with isocratic elution in 14 min. With fluorescence detection at λ_ex/λ_em = 490 /510 nm, the linear range of the TFAs was 1.0-200 nM with low detection limits in the range of 0.1–0.2 nM (signal-to-noise ratio = 3). In addition, the proposed approach was successfully applied for the detection of trans-fatty acids in food samples, and the recoveries using this method ranged from 96.02 to 109.22% with low relative standard deviations of 1.2–4.3% (n = 6).     

Preparation of Amides of Carboxylic Acid Herbicides for Gas Chromatographic Analysis

Abstract

Amides of 14 carboxylic acid herbicides were prepared by reacting the free acid with the amine in toluene for 1 hr at 80[ddot]C in the presence of PCl₃ or P₂I₄. The acids include phenoxyacetic acids, arylacetic acids, and benzoic acids. Aniline, o-toluidine, 3,5-bis(trifluoromethyl)aniline, piperidine, and tetrahydroquinoline were the amine components. Excess of reagents and by-products of the reaction were removed by partitioning into aqueous acid and base. Retention times relative to 2,4-D anilide on 1% OV-22 and FSOT RSL-150 columns are listed for the anilides and should be useful for confirmation purposes. The anilides of 2,4-D, silvex and 2,4,5-T were obtained in better than 90% yield.     

Ion chromatographic separation of alkylsulphonic acids with conductivity detection

Summary An ion chromatographic (IC) method has been developed for the separation of alkylsulphonic acid. Two different stationary phases, silica-based and polymer-based ion-exchange resins, were studied using pure ion exchange and/or hydrophobic interaction mechanisms. Correlations between analyte hydrophobicity and eluent polarity were made in order to investigate the possibility of changing the dominant separation mechanism by varying the eluent composition. The alkyl chain lengths of the sulphonic acids analysed ranged from C₁ to C₉. Detection limits in the submicromolar range were obtained by suppressed conductivity detection.     

Determination of caffeoylquinic acids and flavonoids inCynara scolymus L. by high performance liquid chromatography

Summary The main phenolic compounds in dried extracts fromCynara scolymus (artichoke)—monocaffeoylquinic acids, dicaffeoylquinic acid, and flavonoids–have been separated by high-performance liquid chromatography. By use of a narrow bore C₁₈ column and an acidic mobile phase this HPLC method enabled improved separation within 31 min with significantly reduced solvent consumption compared with other methods. The method was validated to demonstrate its linearity, precision, accuracy, and robustness. Twelve commercial samples were analyzed. Monocaffeoylquinic acids were the most abundant phenolic compounds; the amounts present ranged from 0.48 to 4.24%. The amounts of dicaffeoylquinic acids and flavonoids were smaller—from 0.03 to 0.52%. The method is a good combination of efficiency and economy and should be especially useful for commercial applications.     

Determination of glycuronic acids by high-performance anion chromatography with pulsed amperometric detection

Summary Acid hydrolysis (0.25M H₂SO₄) coupled with enzyme catalysis (pectolyase and β-D-glucuronidase) were employed to extract galacturonic and glucuronic acids from microbial polysaccharides, plant residues, animal wastes, sewage sludge and soil. The glycuronic acids were separated by high-performance anion chromatography (HPAC) on a strong anion-exchange column using 0.1M sodium hydroxide with 0.25M sodium acetate as the mobile phase and determined by pulsed amperometric detection (PAD). HPAC-PAD was found to be superior to high-performance liquid chromatography with ultra-violet (UV) detection in terms of resolution and sensitivity of glycuronic acids. HPAC-PAD was not subject to interferences present with low UV detection (210 nm) and was highly selective for glycuronic acids. Enzymatic hydrolysis after treatment with mild acid (0.25M H₂SO₄) released galacturonic acids from orange peel and pectin, while glucuronic acid was released from Acacia powder. Large amounts of glycuronic acids were also extracted from plant materials. Low levels of uronic acids were detected in poultry manure, sewage sludge and organic-amended soils.     

Ion chromatographic separation of alkylsulphonic acids with conductivity detection

Summary An ion chromatographic (IC) method has been developed for the separation of alkylsulphonic acid. Two different stationary phases, silica-based and polymer-based ion-exchange resins, were studied using pure ion exchange and/or hydrophobic interaction mechanisms. Correlations between analyte hydrophobicity and eluent polarity were made in order to investigate the possibility of changing the dominant separation mechanism by varying the eluent composition. The alkyl chain lengths of the sulphonic acids analysed ranged from C₁ to C₉. Detection limits in the submicromolar range were obtained by suppressed conductivity detection.     

离子排斥色谱法测定黄酒中的13种有机酸

建立了离子排斥色谱法（ion-exclusion chromatography,IEC）测定黄酒中有机酸含量的分析方法。使用Waters离子排斥色谱柱（300 mm×7.8 mm,7 μm）,流动相为H₂SO₄溶液（A）与乙腈（B）的混合溶液（体积比为98：2）,线性梯度程序：0~40 min,流动相A的浓度由0.01 mol/L 上升到0.02 mol/L;40~50 min,流动相A的浓度为0.01 mol/L ;流速为0.5 mL/min,柱温50 ℃,进样量10 μL,检测波长210 nm。结果表明,该方法可在30 min内实现草酸、马来酸、柠檬酸、酒石酸、苹果酸、抗坏血酸、琥珀酸、乳酸、富马酸、乙酸、丙酸、异丁酸和丁酸的完全分离与定量,13种有机酸在0.001~1.000 g/L范围内线性关系良好,回归方程的线性相关系数在0.9997以上。黄酒中13种有机酸的加标回收率为93.4%~103.8%,相对标准偏差为0.1%~1.5%（n=5）。该方法简单快捷、准确、重复性好,可用于黄酒中有机酸的测定。