反相离子对色谱-电感耦合等离子体质谱联用技术测定水中痕量Cr(Ⅲ)与Cr(Ⅵ)

建立了反相离子对色谱(RPIPC)与电感耦合等离子体质谱(ICP-MS)联用技术快速分离测定水中痕量Cr(Ⅲ)和Cr(Ⅵ)的方法.通过考察流动相的pH值、离子对试剂及甲醇的浓度和EDTA的添加等对不同形态铬的保留时间及分离度的影响,确定当流动相组成为2.0 mmol/L TBA,5%(V/V)甲醇,pH=5.5时,Cr(Ⅲ)与Cr(Ⅵ)可达最佳分离.ICP-MS测定时选用碰撞池技术以消除40Ar12C+与35Cl16OH+对52Cr+的谱学干扰;进样100 μL时,Cr(Ⅲ)与Cr(Ⅵ)的检出限分别为0.15 μg/L和0.16 μg/L.加标回收率在93.6%～106.2%之间; RSD<4%(n=3).以本方法分析了某市自来水、雨水及某品牌纯净水中Cr(Ⅲ)与Cr(Ⅵ)的含量,结果令人满意.     

Ethylammonium formate as an organic solvent replacement for ion-pair reversed-phase liquid chromatography

Ethylammonium formate (EAF), an inexpensive and easily synthesized room-temperature ionic liquid, acts like a conventional organic solvent for reversed-phase liquid chromatography (LC). In this report, the use of standard ion-pair reagents with this ionic liquid LC mobile phase and a polystyrene-divinylbenzene PRP-1 column is explored. Starting with the column equilibrated with a methanol mobile phase, the required equilibration time of the column by the EAF ion-pair mobile phase is determined by the plate number profile. Chromatograms of six aromatic carboxylic acids, with either methanol or EAF as the mobile phase, at room temperature (in the absence of an ion-pairing agent) lack resolution with significant peak overlap of nitro-substituted benzoic acids. The addition of 30mM tetrabutylammonium ion to the EAF or methanol mobile phase provides baseline resolution for all peaks in approximately 10 min. Analogous studies using a mixture of four aromatic amines, including protonated tyramine, diphenhydramine, and neutral nitroanilines in the absence or presence of 30mM sodium dodecylsulfate (SDS) in the mobile phase are similar to those for the aromatic acids, indicating baseline resolution with only the ion-pair reagent. Raising the column temperature to 55 degrees C improves the plate count by a factor of approximately 1.2 when using the EAF mobile phase. The retention factor profiles for either the carboxylic acids or the amines, as a function of the organic modifier percentage or ion-pair reagent concentration, are similar for both EAF and methanol. The polymerized acyl monoglycinate surfactant, poly(sodium-N-undecenoyl glycinate), is used for the first time as an LC ion-interaction reagent and is about as effective as SDS for the resolution of organic amines.     

离子对反相液相色谱同时测定家兔血浆中的外源性磷酸肌酸及其代谢产物肌酸

建立了离子对反相高效液相色谱法(IP-RP-HPLC)同时测定家兔血浆中外源性磷酸肌酸(PCr)及其代谢产物肌酸(Cr)的方法,用于研究外源性PCr在家兔体内的药代动力学。以含离子对试剂四丁基硫酸氢铵(TBA)的磷酸盐缓冲液-甲醇为流动相,在Kromasil-C18色谱柱上进行梯度洗脱。采用内标法定量、以基线扣除法计算外源性PCr和Cr的浓度。PCr和Cr的线性范围分别为10～7500 mg/L和10～1500 mg/L;日内和日间精密度均≤6.2%,准确度分别为99.7%~102.2%和96.5%~102.4%;萃取回收率均大于92%。静脉注射PCr后,血浆中PCr的消除为二室模型,消除半衰期为(20.4±2.7) min;表观分布容积为(0.179±0.037) L/kg;清除率为(0.019±0.002) L/(kg\5min);静脉注射PCr后血浆中迅即出现降解产物Cr,其达峰时间为30 min;消除半衰期为(43.7±4.5) min。本方法的专属性强,准确度和精密度高,能特异性地测定家兔血浆中的PCr和Cr。实际应用结果表明,该方法完全符合PCr药代动力学生物分析方法学的要求。     

Reversed phase ion-pair high performance liquid chromatographic gradient separation of related impurities in 2,4-disulfonic acid benzaldehyde di-sodium salt

A reversed phase ion-pair gradient liquid chromatographic method has been developed and validated for purity determination of the hydrophilic compound 2,4-disulfonic acid benzaldehyde di-sodium salt (2,4-DSAD) containing both hydrophilic and more lipophilic related impurities. Mixtures of acetonitrile-phosphate buffer containing tetrahexylammonium hydrogen sulfate as the ion-pairing reagent were used as the mobile phase. A linear gradient, which generated simultaneous change in the concentration of organic modifier, buffer concentration and the concentration of ion-pairing reagent, was applied. The method allows detection of impurities at low levels (0.01% w/w). Excellent repeatability for both retention time (RSD< or =0.3%, n = 6) and detector response (RSD = 0.03%, n = 6 for the main peak and RSD = 6%, n = 6, for an impurity at 0.01 area% level) was obtained. The method was shown to be robust for routine analysis and has been successfully transferred to the quality control laboratory.     

Ion-pair chromatography on a porous graphitic carbon stationary phase for the analysis of twenty underivatized protein amino acids

The analysis of twenty underivatized protein amino acids has been achieved on porous graphitic carbon packing material (Hypercarb). Five perfluoroalkyl carboxylic acids (trifluoroacetic, heptafluorobutyric, nonafluoropentanoic, tridecafluoroheptanoic and pentadecafluorooctanoic acid) have been studied as ion-pairing reagent. Several parameters (equilibration time, quantities adsorbed onto the chromatographic support, concentration and nature of the ion-pairing reagent, as well as temperature effect) have been studied leading to the complete separation of these compounds in gradient elution mode. Evaporative light scattering detector has allowed the detection of these non UV–visible absorbent molecules. The chromatographic methodology developed can also be easily coupled with pneumatically assisted electrospray mass spectrometry.     

Determination of 20 underivatized proteinic amino acids by ion-pairing chromatography and pneumatically assisted electrospray mass spectrometry.

A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The need for chromatographic separation before mass spectrometry determination is demonstrated based on the study of several amino acid pairs which have some similar characteristics. Two suitable LC-MS systems are proposed for amino acid analysis. A preliminary optimization of these systems has been investigated using evaporative light scattering detection as these two detection modes have the same chromatographic requirements. The amino acid separation was achieved on a Purospher RP-18e or a Supelcosil ABZ+Plus column with tridecafluoroheptanoic acid or pentadecafluorooctanoic acid as volatile ion-pairing reagent in an acetonitrile-water mobile phase. In order to elute the most retained amino acids, an elution gradient based on simultaneously increasing the concentration of acetonitrile and decreasing the concentration of the ion-pairing reagent was used. The detection limits of the present work (without specialized optimization) varied from 0.5 to 1 mg 1(-1).     

Speciation of arsenical species by anion-exchange and ion-pair reversed-phase liquid chromatography

Summary Speciation and quantitative analysis of arsenical compounds are performed by using high-performance liquid chromatography (HPLC) with direct UV detection. Ion chromatography has been used to separate mixtures of arsenical compounds (arsenite, MMA, DMA, arsenate) on an anion-exchange column using phosphate buffer (1 mmol/l, pH=5.3) as eluent. Ion -pair reversed-phase chromatography has been investigated to resolve mixtures of arsenite, arsenate, MMA, DMA, arsenobetaine and arsenocholine on an octadecyl-bonded silica column using water as mobile phase (pH=7.3) and tetrabutylammonium cation as ion-pairing reagent. The influence of several parameters (pH, the ion-pairing reagent concentration or the amount of methanol in the mobile phase) has been studied to determine the best chromatographic conditions.     

Retention behaviour of an homologous series of oligodeoxythymidilic acids using reversed-phase ion-pair chromatography

Summary The retention behaviour of an homologous series of phosphorylated oligodeoxythymidylic acid (pd(T)_5–18) oligonucleotides was studied using reversed-phase ion-pair chromatography with isocratic elution conditions. The effects of temperature, pH, eluent ionic strength, percentage organic modifier, concentration and alkyl chain length of the ion-pairing reagent were investigated. The retention behaviour was generally explicable by current theoretical models of ion-pair chromatography. However, the marked effect of mobile phase pH on the retention of the oligonucleotides was unexpected, and this was ascribed to the presence of ionisable residual silanols on the surface of the reversed-phase packing material.     

Insights into the mechanism of separation of heparin and heparan sulfate disaccharides by reverse-phase ion-pair chromatography

Reverse-phase ion-pair high performance liquid chromatography (RPIP-HPLC) and ultra-performance liquid chromatography (RPIP-UPLC) are increasingly popular chromatographic techniques for the separation of organic compounds. However, the fine details of the RPIP separation mechanism are still being debated. Many factors including type and concentration of the ion-pairing reagent, mobile phase pH, organic modifier, ionic strength, and stationary phase all play a role in the overall efficiency and optimization of ion-pairing separations. This study investigates the role that competition between ion-pairing reagents with different steric bulk and hydrophobicity plays in the separation of structural isomers of heparin and heparan sulfate (HS) disaccharides. In addition to providing insights into the mechanism by which RPIP-HPLC can resolve closely related disaccharides, the use of competition between ion-pairing agents could lead to new methods for the separation of larger heparin and HS oligosaccharides. This approach should also be applicable to the analysis of other compound classes, and could lead to a general approach for the chromatographic resolution of mixtures of charged analytes having similar structures.     

Determination of fluorescent whitening agents in laundry detergents and surface waters by solid-phase extraction and ion-pair high-performance liquid chromatography

A simple method was developed to detect four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in household laundry detergents and surface waters by ion-pair high-performance liquid chromatography. The FWA concentrations in detergents were measured directly. The contents of FWAs in water samples were extracted by solid-phase extraction (C18-SPE) with ion-pairing reagent, and were then determined by an isocratic ion-pair chromatography (IPC) using a C18 column, applying tetrabutylammonium hydrogensulfate (TBA) as the ion-pairing reagent in mobile phase, and equipped with fluorescence detection. Water samples at various pH conditions for SPE were evaluated. Experimental results indicate that the proposed method is precise and sensitive in analyzing FWAs, and enables quantitation of 0.01-0.1 microg/l in 100 ml water samples. The recovery rates of FWAs in spiked water samples were between 73 and 89%, and the precision (RSD) ranged from 2.6 to 8.9%. Over 7200 microg/g of 4,4'-bis(2-sulfostryl)-biphenyl (DSBP) and 2320 microg/g of 4,4'-bis[(4-anilino-6-morpholino-1,3,5-triazine-2-yl)-amino]stilbene-2,2'-disulfonate (DAS1) were detected in household laundry detergents. Trace amounts of DSBP were detected in surface water samples ranging from 0.2 to 3.7 microg/l.     

高效液相色谱-串联质谱法同时检测血液中3种季铵盐类肌松剂

维库溴铵、罗库溴铵和泮库溴铵是一类广泛使用的非去极化肌松剂,使用过程中引起过敏反应甚至死亡的情况时有发生,快速检测血液中该类肌松剂的浓度,可为临床早期诊断提供有价值的信息。该类肌松剂为强极性的季铵盐类化合物,在反相色谱柱上难以保留,主要采用离子对色谱法进行分离。采用离子对色谱法时,加入的离子对试剂有离子抑制作用,可降低质谱灵敏度,还会污染质谱系统。该文建立了高效液相色谱-串联质谱(HPLC-MS/MS)同时检测血液中3种季铵盐类肌松剂的检测方法。血液样品经稀释、高速离心后,上清液过Bond Elut AL-N固相萃取柱净化,用0.45 μm的微孔滤膜过滤后检测。采用ZIC-cHILIC色谱柱(50 mm×2.1 mm, 3.0 μm)分离,以乙腈和0.1%甲酸水溶液为流动相,梯度洗脱,在ESI⁺、多反应检测(MRM)模式下检测。3种季铵盐类肌松剂在血液中的基质效应为88.1%~95.4%,在各自范围内线性关系良好,相关系数(R²)均大于0.996,检出限为0.2~0.8 ng/mL,定量限为0.5~2.0 ng/mL,加标回收率为92.8%~110.6%,相对标准偏差(RSD)为3.2%~9.4%。该方法灵敏度高,准确性好,操作简便,可用于血液样品中维库溴铵、罗库溴铵和泮库溴铵的快速检测。     

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。     

手性配位体交换流动相添加剂法拆分对映体

综述了手性配合基交换色谱法通常采用三种手性相系统中的流动相添加剂方法。主要内容有：（Ａ）手性配合基交换机制,给出了描述对映体对在色谱系统中的保留时间和分离选择性的公式,包括手性选择剂在固定相和流动相中的各种不同情况。公式表明整个色谱往系统的对映体选择性不同于溶液中所存在的选择剂与被选择物作用的情况;（Ｂ）影响配合交换的参数,讨论了金属离子、金属离子／配位体比率、金属离子络合物浓度、固定相、流动相ｐＨ、洗脱顺序、有机调节剂、离子对试剂、流动相离子强度、温度、立体选择性和手性交互识别;（Ｃ）应用。     

整体柱离子对色谱-直接电导检测法快速测定微量碘酸根

建立了整体柱离子对色谱-直接电导检测快速测定微量碘酸根的方法.采用反相硅胶整体柱,以氢氧化四丁铵(TBA)-邻苯二甲酸-水-乙腈水溶液为淋洗液,分别讨论了淋洗液、流速及柱温对碘酸根保留的影响,并确定最佳色谱条件为:以0.25 mmol/L TBA-0.18 mmol/L邻苯二甲酸-3％乙腈(pH 5.5)水溶液为淋洗液...     

The effects of pH, ionic strength and buffer concentration of mobile phase onR F of acidic compounds in ion-pair TLC

Summary The effects of some factors important in ion-pair, high-performance liquid chromatography were studied in ion-pair, thin-layer chromatography. Tetramethyl and cetyltrimethylammonium salts were used as ion-pairing reagents. As stationary phases, silica gel and chemically bonded reversed-layers (C₁₈) were used. Layers were impregnated with ion-pairing reagent prior to chromatography. In some cases the stationary phase was treated with buffer at different concentrations. The mobile phase contained methanol and water, in one set of experiments buffer, salt for adjustment of ionic strength and ion-pairing reagent were added. The migration behaviour of different benzoic acids was studied. Several problems of ion-pair thin-layer chromatography are discussed. Passed away on 13^th of April, 1998 Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Rapid and simultaneous determination of piperidinium and pyrrolidinium ionic liquid cations by ion pair chromatography coupled with direct conductivity detection

A method of ion-pair chromatography with direct conductivity detection was developed on a silicabased monolithic column for the fast and simultaneous determination of piperidinium and pyrrolidinium ionic liquid cations. The effects of the mobile phase, column temperature and flow rate on the retention of the cations were investigated. The retention rules were discussed. As an ion-pair reagent, sodium heptanesulfonate is more suitable than sodium pentanesulfonate for the separation and determination of piperidinium and pyrrolidinium cations. The increase of ion-pair reagent concentration led to the increased retention time of the cations. When acetonitrile content and mobile phase flow were increased, the retention time of the cations became shorter. The retention of piperidinium and pyrrolidinium cations is an exothermic process, and the retention of the cations conforms to the carbon number rule. The chromatographic analysis was performed using the Chromolith Speed ROD RP-18e column, 0.5 μmol/L sodium heptanesulfonate-5% acetonitrile as the mobile phase at a flow rate of 3.0 mL/min and column temperature of 30℃. Separation of N-methyl-N-ethyl piperidinium, N-methyl-N-propyl piperidinium, N-methyl-N-butyl piperidinium and N-methyl-N-ethyl pyrrolidinium, N-methyl-N-propyl pyrrolidinium, N-methyl-N-butyl pyrrolidinium cations were achieved within 10 min. The detection limits (S/N=3) were between 0.19 and 3.08 mg/L. Relative standard deviations (n=5) for peak areas were less than 1.2%. The method has been applied to the determination of piperidinium and pyrrolidinium cations in ionic liquid samples. The spiked recoveries of ionic liquid cations were between 96% and 111%. The method is accurate, reliable, rapid, and has a better practicability.     

A systematic study of the desorption of different ion-pairing reagents on reversed phase thin-layers

Summary The absolute concentrations and the concentration distribution of different cationic ion-pairing reagents, such as tetramethylammonium bromide, tetrabutylammonium bromide, cetyltrimethylammonium bromide and trioctylmethylammonium chloride were studied after chromatographic development on physically and chemically bonded reversed-phase layers. The combination of the chromatographic conditions involved three variations. Untreated layers were chromatographed with mobile phases containing the ion-pairing reagent. Several layers were treated with the ion-pairing reagent prior to the chromatographic run, and methanol-water mixtures were used as mobile phase. In a third set of experiments both the layer and the mobile phase contained the ion-pairing reagent. The chromatographic behaviour of acid, neutral and basic model compounds were also studied. For the determination of different reagents remaining on the layer after the chromatographic run, spectrophotometric, potentiometric methods and capillary electrophoresis were used. The performance of the analytical methods was evaluated. Results obtained for the absolute concentrations and distribution of the reagents and the retention data were compared to those obtained on silica gel layers. A discussion of the retention mechanism is given. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Effect of some parameters on the liquid chromatographic separation of biogenic amines and their metabolites

The liquid chromatographic separation of some biogenic amines and their metabolites with a reversed-phase ion-pair system has been optimized. The effects of the nature of the stationary phase, the column temperature, the pH, and the ion-pair reagent concentration of the mobile phase have been investigated. The most striking result is the influence of the column temperature on selectivity.     

Determination of Nimesulide by Ion Pair High-Performance Liquid Chromatography Using Tetrabutylammonium as the Counterion

A new method for nimesulide was developed using ion-pair reversed phase liquid chromatography and tetrabutylammonium hydrogen sulfate as the ion-pairing reagent. The influence of the ion pair forming reagent concentration, pH, and mobile phase composition on the retention time of nimesulide were studied. The optimum experimental conditions included a C18 column, a mobile phase of a 50/50 (v/v) mixture of acetonitrile and 15 mM phosphate buffer (pH 8.00) containing 6 mM tetrabutylammonium hydrogen sulfate, 25°C, isocratic elution, a flow rate of 1 mL/min, a run time of 10 minutes, and photodiode array detection at 404 nm. From the analysis of the results, the mechanism for the separation of nimesulide was also established. The retention time for nimesulide was 4.76 ± 0.05 min. The method was linear between concentrations of 9 µg/mL to 64 µg/mL, with limits of detection and quantification of 1.111 µg/mL and 3.390 µg/mL, respectively. The method is simple, rapid, accurate, and precise, and successfully applied for the determination of nimesulide in pharmaceutical products.     

Determination of ethambutol by ion-pair reversed phase liquid chromatography with UV detection

An ion-pair reversed phase liquid chromatography method for the antituberculosis drug ethambutol hydrochloride was developed using sodium 1-heptanesulfonate (4.0 mg/ml) as an ion-pairing (IP) reagent. To enable detection of the ethambutol with a UV detector without sample pretreatment, the pH 4.5 aqueous tetrahydrofuran (THF) (25%, v/v) mobile phase contained 1.0 mM Cu(II), which forms a UV-absorbing complex with the analyte. At a column temperature of 35 °C, ethambutol gives a symmetrical peak with a retention time of 5 min. Chromatographic conditions were optimized through study of the effects of mobile phase composition and pH, Cu(II) and IP reagent concentration, and column temperature. The method is shown to be simple, precise, efficient, robust, linear up to at least 0.25 mg/ml, and to have a limit of quantitation of 6 μg/ml.