咪唑离子液体用于反相色谱流动相添加剂分析苯甲酸和山梨酸

开展了咪唑离子液体用于反相色谱流动相进行苯甲酸和山梨酸分析的研究。考察了咪唑离子液体种类与浓度、甲醇浓度、紫外检测波长等因素对分离、检测苯甲酸和山梨酸的影响,并探讨了2种分析物的保留规律。建立了以咪唑离子液体为流动相添加剂的反相色谱测定苯甲酸和山梨酸的分析方法。采用Agilent ZORBAX ODS反相色谱柱,以甲醇-0.2 mmol/L氯化1-丁基3-甲基咪唑水溶液(40∶60,体积比)为流动相,紫外检测波长230 nm,流速1.0 mL/min,色谱柱温度35℃时,可在7.0 min内实现苯甲酸和山梨酸的分离和检测。苯甲酸和山梨酸的线性范围为1.0～100.0 mg/L,相关系数(r)高于0.999 5,检出限均为0.02 mg/L。将方法应用于饮料样品中苯甲酸和山梨酸的测定,加标回收率为93.9%～104%,相对标准偏差(RSD)不大于4.0%,满足定量分析的要求。     

离子色谱-紫外检测法分离测定吡啶离子液体阳离子

建立了用离子色谱-紫外检测法分离测定3种吡啶离子液体阳离子(N-乙基吡啶、N-丁基吡啶和N-丁基四甲基吡啶)的方法。采用磺酸型阳离子交换柱,以乙二胺-柠檬酸-乙腈为流动相,考察了流动相和色谱柱温度对离子保留的影响,探讨了保留规律。实验发现,吡啶阳离子的保留过程是放热过程。优化的色谱条件为：流动相是0.2 mmol//L乙二胺-0.3 mmol//L柠檬酸-0.5%(v/v)乙腈(pH 4.2),流速1.0 mL/min,柱温30℃。在此条件下可以基线分离3种吡啶阳离子。所测阳离子的检出限(S/N=3)分别为0.01、0.01、0.02 mg/L,峰面积的相对标准偏差(n=5)小于0.8%。将此方法应用于分析实验室合成的吡啶离子液体样品,加标回收率在96.3%～103.7%之间。本方法准确、可靠、快速,具有较好的实用性。     

高效液相色谱-串联质谱法测定食品中6种人工合成甜味剂

建立了食品中6种人工合成甜味剂(甜蜜素、糖精钠、安赛蜜、阿斯巴甜、阿力甜、纽甜)的高效液相色谱-串联质谱检测方法。样品经甲醇-水溶液(1:1, v/v)提取,以C18柱为分离柱,0.1%(v/v)甲酸-5 mmol/L甲酸铵溶液/乙腈为流动相,经高效液相色谱分离,采用电喷雾串联四极杆质谱进行检测。结果表明,6种人工合成甜味剂在20～500 μg/L范围内定量离子对的响应峰面积和样品质量浓度之间有良好的线性关系(相关系数＞0.998)。在3个添加水平下,样品平均回收率为81.3%～106.0%,相对标准偏差小于11%。该方法简单、灵敏、准确,可用于食品中6种人工合成甜味剂的同时检测。     

离子液体作高效液相色谱流动相添加剂分离测定芳香族羧酸

以离子液体作反相高效液相色谱流动相添加剂,建立了分离测定对氨基苯甲酸、邻苯二甲酸、对羟基苯甲酸、水杨酸、苯甲酸、邻甲苯甲酸6种芳香族羧酸的方法。以C18反相色谱柱为分离柱,采用紫外检测方法,以离子液体作高效液相色谱流动相添加剂,考察了检测波长、甲醇含量、离子液体溶液的pH值、离子液体烷基链长度以及离子液体溶液浓度等分离及测定条件。优化得到的色谱条件为:以甲醇和1.0mmol/L 1-丁基-3-甲基咪唑四氟硼酸盐水溶液(pH 3.0)(体积比40∶60)为流动相;检测波长240 nm;流速1.0 mL/min;柱温30℃。在优化条件下对6种芳香族羧酸进行梯度洗脱,约在16.5 min内分离完全;在5~120 mg/L范围内,线性系数均在0.999以上;检出限为0.026~0.082 mg/L。方法的平均加标回收率为98.3%~103.8%,相对标准偏差不高于0.63%。将该方法应用于药品复方紫荆皮水杨酸溶液和足君清酊剂中芳香族羧酸的测定,结果满意。     

高效离子排斥色谱法测定蔬菜中的马来酰肼

建立了马铃薯、洋葱、大蒜中马来酰肼(MH)的高效离子排斥色谱(HPIEC)检测方法。样品经提取、净化、过滤后进行色谱分析,以3 mmol/L 甲酸水溶液-乙腈(70:30, v/v)为流动相,流速0.8 mL/min,采用Ionpac ICE-AS1(250 mm×9 mm)HPIEC色谱柱分离,紫外检测波长205 nm,外标法定量。结果表明,MH的线性范围为0.006～1.0 mg/L,相关系数为0.9999,回收率为91%～103%,相对标准偏差(RSD)均小于3%,检出限为0.002 mg/L (S/N=3)。该方法灵敏度高,前处理简便,可用于马铃薯、洋葱、大蒜中MH的检测。     

离子对色谱法同时分离测定吡啶及咪唑离子液体阳离子

建立了用紫外检测的反相离子对色谱梯度淋洗同时分离测定4种吡啶离子液体阳离子和5种咪唑离子液体阳离子的方法。实验采用ZORBAX Eclipse XDB-C18反相色谱柱,以离子对试剂水溶液(用柠檬酸调节pH值)+乙腈为流动相,考察了离子对试剂种类和浓度、乙腈浓度和色谱柱温度对保留的影响,探讨了相关保留规律,确定最佳色谱条件为:流速1.0 mL/min、柱温30℃,以1.0 mmol/L庚烷磺酸钠水溶液(pH 4.0)-乙腈为淋洗液进行梯度洗脱。在此条件下,4种吡啶阳离子和5种咪唑阳离子在15 min内达到基线分离。检出限(S/N=3)为0.31～0.54 mg/L,峰面积的相对标准偏差为0.10%～0.75%。将该方法用于实验室合成的离子液体样品分析,加标回收率为94%～98%。该方法准确、可靠,具有较好的实用性。     

离子色谱-直接电导检测法测定离子液体的阴离子p-甲苯磺酸根

建立了离子液体阴离子p-甲苯磺酸根的离子色谱-直接电导检测分析方法。采用Shim-pack IC-A3季铵型阴离子交换色谱柱,考察了流动相种类和色谱柱温度对分离测定p-甲苯磺酸根的影响。确定最佳色谱条件为:以1.2 mmol/L柠檬酸-15%乙腈混合水溶液(pH 5.0)为流动相,流速1.0 mL/min,柱温45℃。在此条件下,p-甲苯磺酸根与常见无机阴离子(氟离子、氯离子、溴离子和硝酸根)可以获得很好的分离。该方法测定p-甲苯磺酸根的线性范围为4～100 mg/L,检出限(S/N=3)为1.22 mg/L,保留时间和峰面积的相对标准偏差(n=5)分别为0.42%和1.8%。将方法用于离子液体中p-甲苯磺酸根的测定,加标回收率为99.6%。     

高效液相色谱法同时测定软饮料中20种食品添加剂

建立了高效液相色谱同时测量软饮料中20种食品添加剂（咖啡因、3种甜味剂、9种防腐剂和7种着色剂）的方法。确定的最佳分离条件为:C₁₈反相色谱柱（250 mm×4.6 mm×5μm）,流动相为0.10 mol/L乙酸铵缓冲溶液（pH 7.2）和乙腈-甲醇混合有机相（10:90,V/V）,梯度洗脱,二极管阵列检测器在190～700 nm监测。20种食品添加剂浓度在0.10～300 mg/L范围内具有良好的线性,相关系数大于0.998;20种食品添加剂的检出限在0.005～0.110 mg/L范围内;20种食品添加剂的加标回收率为91.4%～100.5%;相对标准偏差计为0.6%～4.0%。本方法可应用于16个品牌的软饮料中食品添加剂的检测。     

离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的离子对色谱-直接电导检测法分析

建立了同时测定离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的反相离子对色谱-直接电导检测方法。采用Diamonsil C18分离柱,以离子对试剂-苹果酸-乙腈水溶液为流动相,从流动相组成和色谱柱温度两方面讨论并确定了优化的色谱条件,即以0.15 mmol/L氢氧化四丁铵-0.099 mmol/L苹果酸-20%(v/v)乙腈混合水溶液(pH 6.5)为流动相,柱温25 ℃。在此条件下,三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子均达到基线分离,且不受其他常见阴离子氟离子、氯离子、溴离子、硝酸根、硫酸根的干扰。三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子的检出限(信噪比为3)分别为0.21、0.07、0.36、0.12 mg/L。将方法应用于测定离子液体中三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子,加标回收率为95.0%～104.6%。该法简便、快速、灵敏度较高,可满足离子液体样品的检测要求。     

离子交换色谱分离-紫外检测法测定吡啶离子液体阳离子

建立了用离子交换色谱分离-紫外检测法测定N-乙基吡啶、N-丁基吡啶和N-丁基四甲基吡啶3种吡啶离子液体阳离子的方法。采用磺酸型阳离子交换柱,以乙二胺-柠檬酸-乙腈为流动相,研究了流动相和色谱柱温度对离子保留行为的影响和规律。实验发现,吡啶阳离子的保留过程是放热过程。优化后的色谱条件:流动相为乙二胺(0.2 mmol//L)-柠檬酸(0.3 mmol//L)-乙腈(0.5%,v/v,pH=4.2),流动相流速为1.0mL/min,色谱柱为Shim-pack IC-C1阳离子交换柱,色谱柱温度为30℃。在此条件下3种吡啶阳离子可以达到基线分离。所测阳离子的检出限(S/N=3)分别为0.01、0.01、0.02mg/L,峰面积的相对标准偏差(n=5)小于0.8%。紫外检测法测定化学实验室合成的吡啶离子液体样品,样品加标后测得的加标回收率在96.3%~104%。方法准确、可靠、快速,具有较好的实用价值。     

Modeling of ion-exclusion and vacancy ion-exclusion chromatography in analytical and concentration overload conditions

Ion-exclusion chromatography (IEC) finds applications in various different analytical separations of weak acids. Pure, deionized water or a diluted, aqueous solution of a strong mineral acid (such as, e.g., sulphuric acid) is used as the mobile phase, whereas a typical stationary phase is a strongly acidic resin in the H(+) form (e.g., the sulfonated polystyrene-divinylbenzene resin with a high ion-exchange capacity, provided by the sulfonic acid groups). When pure water is used as the mobile phase, then the characteristic leading (i.e., frontally tailing) peaks are obtained, and the retention depends mainly on the concentration of the analyte. An alternative technique is vacancy ion-exclusion chromatography (v-IEC), in which the column is equilibrated with the sample solution, flowing as the mobile phase through the system, and pure water is injected as the sample. In this case, the symmetrical vacant peaks are obtained. The aim of this paper is to describe the retention mechanism in IEC and v-IEC for the adsorptive and nonadsorptive acids in analytical and concentration overload conditions, with pure water and the diluted sulphuric acid solution as the two different mobile phases. The retention times and the peak shapes predicted by the derived equations remain in a good qualitative and quantitative agreement with the experimental data. The model proposed in this paper predicts the new features characteristic of IEC for the adsorptive acids. These are, namely, an increase in the retention time of the peak apexes (up to a certain level and concurring with an increase in the acid concentration), followed by a subsequent decrease of the retention time (with the further growth of the acid concentration in the eluent). Similar changes in the retention time observed for v-IEC in the specific adsorption conditions were also correctly predicted by the model.     

The effect of buffer concentration and cation type in the mobile phase on retention of amino acids and dipeptides in hydrophilic interaction liquid chromatography

The current work is focused on exploring the effect of buffer cation type and its concentration on retention of amino acids, dipeptides and their blocked analogues on two stationary phases, i.e., bare silica and amide-based in hydrophilic interaction liquid chromatography. Five different buffers of pH 4.0 composed of Tris/acetic acid, triethylamine/acetic acid, ammonium/acetic acid, Li⁺/acetic acid and Ba²⁺/acetic acid were used in various concentrations. Interestingly, an increase of the buffer concentration caused increasing, decreasing or stable retention of analytes, according to the cation type in the buffer. The buffers containing barium cations provided the highest retention of all the analytes in comparable mobile phases, i.e., buffers with the same ionic strength and pH on both columns. Moreover, using buffers with barium cation different selectivity for dipeptides was observed. The chromatographic systems with buffers consisting of triethylamine behaved differently compared to others.     

The Surface Properties of Nanodiamonds As Examined by Gas Chromatography

Two samples of detonation nanodiamond (ND) were studied using gas chromatography. Sample ND-Cr was treated by boiling sulfochromic acid with liquid-phase acid purification. Sample ND-Oz was treated with gaseous ozone. The retention times determined for nine substances of different nature at various temperatures were used to calculate the specific retention volumes and the thermodynamic parameters of adsorption of test compounds on ND-Oz and ND-Cr. The adsorption heats of tested n-hydrocarbons on nanodiamond powders, especially on ND-Oz, are close to those on graphitized carbon black (GTB). For benzene and polar compounds, the specific interaction terms in the total energy of adsorption were determined. These terms are higher for ND-Oz than for ND-Cr; i.e., sample ND-Oz contains more reactive functional groups.     

Palladium-catalyzed stereospecific epoxide-opening reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters with an alkylboronic acid leading to gamma,delta-vicinal diols with double inversion of the configuration

A palladium-catalyzed stereospecific epoxide-opening reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters with an alkylboronic acid leading to gamma,delta-vicinal diols is described, which proceeds with retention of the configuration, i.e., via two consecutive S(N)2 processes, to afford the corresponding gamma,delta-cyclic boronates in high yields.     

Retention of opioids and their glucuronides on a combined zwitterion and hydrophilic interaction stationary phase

A stationary phase combining zwitterionic ion chromatography and hydrophilic interaction chromatography (ZIC-HILIC) from SeQuant was evaluated for the chromatography of some opiates and their polar metabolites. The effects of mobile phase constitution on retention and resolution were extensively evaluated. Different aspects of mobile phase constitution such as ion strength and type of buffer, type and amount of organic modifier and pH were examined. The selectivity and retention of the opiates compared to their glucuronides could be substantially altered with small changes of the mobile phase, especially when the type of buffer, i.e., formate or acetate and organic modifier, i.e., acetonitrile or methanol were changed. The retention on the ZIC-HILIC was dominated by hydrophilic interaction chromatography (HILIC) but considerable effects on the selectivity was observed, possibly caused by an ion exchange mechanism due to interactions with the charges on the stationary phase.     

Manufacturing of Fluff Pulp Using Different Pulp Sources and Bentonite on an Industrial Scale for Absorbent Hygienic Products

In this study, for the first time, a composite fluff pulp was produced based on the combination of softwood (i.e., long-length fiber), hardwood (i.e., short-length fiber), non-wooden pulps (i.e., bagasse) and bentonite, with specific amounts to be used in hygienic pads (e.g., baby diapers and sanitary napkins). After the defibration process, the manufactured fluff pulp was placed as an absorbent mass in diapers and sanitary napkins. Therefore, tests related to the fluff pulp, such as grammage, thickness, density, ash content, humidity percentage, pH and brightness, tests related to the manufactured baby diapers, such as absorption capacity, retention rate, retention capacity, absorption time and rewet, and tests related to the sanitary napkin, such as absorption capacity and rewet, were performed according to the related standards. The results demonstrated that increasing the amount of bagasse pulp led to increasing the ash content, pH and density of fluff pulp and decreasing the brightness. The addition of bentonite as a filler also increased ash content and pH of fluff pulp. The results also demonstrated that increasing of bagasse pulp up to 30% in combination with softwood pulp led to increasing absorption capacity, retention rate, retention capacity, absorption time and rewet of baby diapers and of sanitary napkins.     

Isocratic separations of closely-related mono- and disaccharides by high-performance anion-exchange chromatography with pulsed amperometric detection using dilute alkaline spiked with barium acetate.

Mixtures of closely related mono- and disaccharides may be efficiently separated by high-performance anion-exchange chromatography (HPAEC) only when relatively dilute alkaline eluents are employed (i.e., < 20 mM NaOH). The main drawbacks of these eluent solutions are (i) column regeneration between runs, (ii) poor reproducibility of the retention times, and (iii) the need for post-column base addition for enhancing sensitivity. Here, we describe some examples of isocratic separations of carbohydrates by HPAEC coupled with pulsed amperometric detection (PAD) accomplished by carbonate-free alkaline eluents (i.e., 5-20 mM NaOH) obtained upon addition of Ba(OAc)2 (1-2 mM). These separations include aldohexoses (i.e., galactose, glucose, and mannose), aminohexoses (i.e., glucosamine and galactosamine) and their N-acylated derivatives (i.e., N-acetylglucosamine and N-acetylgalactosamine) along with some isomeric disaccharides (i.e., lactose, lactulose and epilactose). The separation of closely related isomers of trehalose, alpha,alpha, alpha,beta, and beta,beta, is also presented. It is recommended to add Ba(OAc)2 to NaOH solutions several hours before using the alkaline eluent (i.e., 12-24 h) to ensure complete barium carbonate precipitation in the eluent reservoir. Adopting such a simple strategy can be especially useful for performing carbohydrate separations under isocratic conditions in which no regeneration and or re-equilibration of column between runs is required. Excellent repeatability of retention data throughout a three-day working session was observed, with relative standard deviations ranging from 2.0 to 3.7%, and from 0.5 to 2.0%, as day-to-day and within-day values, respectively. In addition, there was no need for postcolumn addition of strong bases to the eluent, and successful applications of the present approach confirmed its validity and practicability with detection limits of simple carbohydrates in the picomole range.     

羧基甜菜碱型亲水作用色谱柱的制备及性能研究

以甲基丙烯酰氧乙基二甲基乙酸铵(CBMA)为功能单体,利用表面引发原子转移自由基聚合(Surface-initiated atom transfer radical polymerization, SI-ATRP)技术,将CBMA接枝到硅胶表面,得到接枝聚合物CBMA的亲水作用色谱固定相(Silica-CBMA).通过改变SI-ATRP反应体系中单体的浓度,制备了3种不同接枝量的亲水作用色谱固定相.考察了Silica-CBMA固定相对有机酸类化合物的分离性能以及流动相中pH值、盐浓度、水含量等因素对溶质保留行为的影响.结果表明,在亲水作用色谱模式下,Silica-CBMA固定相对有机酸类化合物的分离是离子交换作用与亲水作用的混合色谱模式.流动相中盐浓度增大,溶质保留减弱,符合离子交换作用特征;固定相和溶质的离子化程度受流动相pH值影响较大,pH值增大,溶质保留增强;而溶质的保留时间随流动相水含量增加而降低则是典型的亲水作用色谱特征.使用自制Silica-CBMA柱,建立了芦丁片中维生素C、芦丁含量的亲水作用色谱测定方法,操作方法简单,为强极性样品的分离测定提供了新方法.     

HPLC-Isocratic Study of the Separation and Determination of Phenolphthalein and Its Metabolite, Phenolphthalein-Glucuronic Acid, as Markers of Enterohepatic Circulation

An isocratic high-performance liquid chromatographic method for separation and determination of phenolphthalein and its metabolite, phenolphthalein-glucuronide, using bromocresol purple as an internal standard is described. The method uses a mobile phase of 50 mM phosphate buffer (pH 7.7)-methanol (52.5:47.5, v/v), a 3-μm reversed-phase C₁₈ column (50 × 4.6-mm i.d.), a flow rate of 1 ml/min, and UV detector wavelength of 230 nm. The most important variables that can affect the retention of these compounds (i.e., organic modifier concentration, buffer concentration, and pH) were systematically studied. Two different retention orders were observed, depending on buffer concentration and pH. The effects on retention of the addition of triethylamine or acetic acid to the mobile phase are also discussed. This method has been developed for future application to the determination of phenolphthalein and phenolphthalein-glucuronide in biological fluids such as plasma, bile, and urine of rats within a study involving a new model for enterohepatic recirculation and pharmacokinetics.     

Systematic characterisation of long-chain aliphatic esters of wool wax by gas chromatography-electron impact ionisation mass spectrometry

A detailed structural characterisation of the aliphatic high-molecular-mass esters extracted from raw wool based on high-temperature gas chromatography-electron impact ionisation mass spectrometry is described. The raw wool esters extracted are in the range of C37 to C54 (i.e., molecular mass 550-788). The selected ion chromatogram exhibited four isomers for the esters with an odd number of carbon atoms (i:a, i:n, a:n and n:n) and five for those with an even number of carbon atoms (i:i, a:a, i:n, a:n and n:n). Isomeric structural elucidation is discussed with respect to the long-chain fatty acid and long-chain fatty alcohol structures, on the basis of chromatographic retention behaviour and mass spectral information.