Capacitively coupled contactless conductivity detection as an alternative detection mode in CE for the analysis of kanamycin sulphate and its related substances

A method was developed to determine simultaneously kanamycin, its related substances and sulphate in kanamycin sulphate using capacitively coupled contactless conductivity detection. Kanamycin is an aminoglycoside antibiotic that lacks a strong UV-absorbing chromophore. Due to its physicochemical properties, CE in combination with capacitively coupled contactless conductivity detection was chosen. The separation method uses a BGE composed of 40 mM 2-(N-morpholino)ethanesulphonic acid monohydrate and 40 mM L-histidine, pH 6.35. A 0.6 mM N-cetyltrimethyl ammonium bromide (CTAB) solution was added as electroosmotic flow modifier in a concentration below the critical micellar concentration (CMC). Ammonium acetate 50 mg/L was used as internal standard. In total, 30 kV was applied in reverse polarity on a fused-silica capillary (65/41 cm; 75 μm id). The optimized separation was obtained in less than 6 min with good linearity (R(2)=0.9999) for kanamycin. It shows a good precision expressed as RSD on the relative peak areas equal to 0.3 and 1.1% for intra-day and inter-day precision, respectively. The LOD and LOQ are 0.7 and 2.3 mg/L, respectively. Similarly, for sulphate, a good linearity (R(2)=0.9996) and precision (RSD 0.4 and 0.6% for intra-day and inter-day, respectively) were obtained.     

Rapid and selective micellar electrokinetic chromatography for simultaneous determination of amikacin, kanamycin A, and tobramycin with UV detection and application in drug formulations

A simple and selective micellar electrokinetic chromatography (MEKC) with UV detection is described for simultaneous determination of amikacin, tobramycin, and kanamycin A, performed in Tris buffer (180 mM; pH 9.1) with 300 mM sodium pentanesulfonate (SPS) as an anionic surfactant. Under this condition, good separation with high efficiency and the required short analysis time is achieved. The linear ranges of the method for the determination of amikacin, tobramycin, and kanamycin A were 0.1-0.5 mg / mL, 0.4-2.0 mg / mL, and 0.4-2.0 mg / mL, respectively; the detection limits (signal-to-noise ratio = 3; injection, 0.5 psi 5 s) were 0.08, 0.2, and 0.2 mg / mL, respectively. The small amount of sample required and the expeditiousness of the procedure allow content uniformity to be determined in individual commercial products.     

Development of a fully buffered molybdate electrolyte for capillary electrophoresis with indirect detection and its use for analysis of anions in Bayer liquor

A new counterion-buffered molybdate electrolyte was developed and optimized for simultaneous quantitative determination of up to eight anions (chloride, sulphate, oxalate, fluoride, formate, malonate, succinate, and acetate) in Bayer liquor by capillary electrophoresis with indirect detection at 214 nm. The separation parameters were optimized in respect to separation of the critical analyte group fluoride-formate-malonate, with the optimal electrolyte prepared from molybdic trioxide containing 5.0 mmol/L MoO3, 1.3 mmol/L cetyltrimethylammonium bromide (CTAB), and buffered with diethanolamine (DEA) to pH 9.2 (ca. 20 mM DEA). Total length of separation capillary was 80 cm, resulting in run time of under 4 min. The method is suitable for a wide concentration range of the analytes (1-50 mg/L) with linear calibration plots (R2 = 0.9983-0.9999). Relative standard deviations were 0.05%-0.07% for migration times and 0.67%-2.04% for peak areas. The detection limits were in the range of 0.17-0.51 mg/L or 2-10 micromol/L (hydrostatic injection of 30 s of 1000 x diluted sample). Due to its good buffering capacity, the electrolyte exhibited an excellent ruggedness and good tolerance to the alkaline samples. Consequently, Bayer liquor samples could be diluted as little as 100 x which allows more sensitive determination of minor components over previous methods. The method was successfully applied to analysis of Bayer liquor samples with recoveries in the range of 95-105%.     

Micellar electrokinetic capillary chromatography for the determination of Viagra and its metabolite (UK-103,320) in human serum

Micellar electrokinetic capillary chromatography (MEKC) was investigated for the determination of Viagra (sildenafil citrate, SC) and its metabolite (UK-103,320) in human serum in a concentration range of clinical interest. For MEKC, human serum samples spiked with SC and UK were obtained directly after elution with methanol from a tC18 cartridge. The extract was evaporated and regenerated in a solution 1 mM of phosphate buffer (pH 12.3) which contained a methanol percentage of 20% that was analyzed using phosphate buffer (pH 12.3, 10 mM) containing 30 mM sodium dodecyl sulfate (SDS) as separation electrolyte and a fused-silica capillary. This method gave satisfactory interday precision with respect to migration times relative standard deviation (RSD < 1%) and linear responses for the concentration ranges investigated (0.50-3.50 mg L(-1) for the compound SC and 0.90-4.60 mg L(-1) for UK). An intraday RSD (n = 5 graphs) between the slopes of the calibration graphs was acceptable (6.40%) for SC and (3.37%) for UK. A satisfactory interday precision between slopes was also obtained (RSD 4.10% for SC and a RSD 2.72% for UK) which demonstrated the ruggedness of this method. Detection limits (S/N = 3) were about 200 ng/mL for both compounds in human serum. MEKC was shown as a good method with regards to simplicity, precision and sensitivity.     

在线扫集-胶束毛细管电动色谱法测定复方氨酚烷胺胶囊中的3种有效成分

以在线扫集-胶束毛细管电动色谱法(Sweeping-MEKC)测定了复方氨酚烷胺胶囊中的马来酸氯苯那敏、咖啡因和对乙酰氨基酚3种有效成分。考察了缓冲溶液pH值、SDS浓度、分离电压及进样时间等对分离效果的影响。优化条件:以未涂层熔融石英毛细管(55 cm×50μm,有效柱长35 cm)为分离柱;环境温度25℃;80 mmol/L十二烷基磺酸钠+20 mmol/L NaH2PO4(pH 2.2)+15%乙腈为缓冲体系,分离电压-20kV,进样时间60 s(H=20.0 cm),测量波长210 nm。在该条件下氯苯那敏、咖啡因和对乙酰氨基酚在25min内出峰,峰面积RSD均小于4%;线性范围分别为2.45～39.17、1.61～25.76、1.58～25.28 mg/L;检出限(S/N=3)分别达139、34、24μg/L,回收率分别为96%～101%、98%～102%、96%～102%。     

Simultaneous determination of Fe(II) and Fe(III) in waters by capillary isotachophoresis

An ITP method for the simultaneous determination of Fe(II) and Fe(III) in waters, based on separation of their EDTA and fluoride complexes, respectively, was developed. The leading electrolyte used consists of chlorides, La(III) as co-counter ion and is buffered with beta-alanine to pH = 3.5. The terminating electrolyte contains caproic acid and L-histidine (pH = 4.5). The method was validated and tested with samples of artificial, ground and treated water with good results, comparable to those obtained by other analytical techniques. Fe(II) and Fe(III) up to 20 mg/L were measured with an RSD = 1.4-1.5% and detection and determination limits of 0.8-0.9 and 3.0-3.5 mg/L, respectively. The ITP method can be recommended for routine utilization in hydroanalytical laboratories.     

Simultaneous determination of silicon and phosphorus in soil and plants by reversed-phase ion-pair chromatography

A reversed-phase ion-pair high-performance liquid chromatographic method, using tetrabutylammonium bromide (TBABr) as ion-pair reagent, has been developed for the simultaneous analysis of silicon (Si) and phosphorus (P) as heteropoly acids in soil and plant samples. The effect of the concentrations of ion-pair reagent, acetate buffer and organic modifier as well as the pH of buffer on separation was made clear. The reaction conditions and stability of heteropoly acids were investigated. Furthermore, the phenomenon occurred in the optimized process was also further researched. The separation was performed on a reversed-phase C(18) column within 11 min with 40:60 (v/v) 0.1M acetate buffer (pH 3.9)-acetonitrile (ACN) containing 0.8 mM TBABr as a mobile phase. The linear ranges of the peak area calibration curves for Si and P were 0.08-50 mg/L and 0.40-50 mg/L, respectively. The detection limits calculated at S/N=3 were 0.0057 mg/L and 0.0280 mg/L for Si and P, respectively. The method was successfully applied to the analysis of soluble and total contents of Si and P in soil and plant samples.     

微流控芯片非接触电导法测定药品中的精氨酸布洛芬含量

建立了微流控芯片非接触电导检测快速测定精氨酸布洛芬含量的方法。考察了缓冲液种类和浓度、添加剂、分离电压以及进样时间等因素对分离检测的影响。优化条件为:20 mmol/L Tris-20 mmol/L H3BO3(p H 8.6)为缓冲溶液、不加添加剂、分离电压2.0 k V、进样时间10.0 s,在45.0 s内可实现精氨酸布洛芬的快速分离测定。结果表明,布洛芬和精氨酸在80.0~1.00×103mg/L范围内线性关系良好,相关系数(r)分别为0.998和0.997,检出限(S/N=3)为60 mg/L,相对标准偏差分别为1.9%和1.8%,加标回收率分别为97.9%~103%和97.3%~102%。该方法快速、简便,为精氨酸布洛芬非甾体抗炎药物的分析和质量控制提供了一种新方法。     

Measurement of serum salicylate levels by solid-phase extraction and desorption/ionization on silicon mass spectrometry

The applicability of the matrix-free laser desorption/ionization on silicon mass spectrometry (DIOS-MS) to measuring serum drug levels was examined by analyzing serum salicylic acid. The optimized and simple solid-phase extraction (SPE) allowed good recovery, 88.9 +/- 5.8%, for 1.4 mM (200 mg/L) of salicylic acid in serum. The negative ion MS allowed measurements of deprotonated molecules without interference from other signals. Using a deuterium-labeled internal standard, good linearity was obtained in the 0.14 to 4.2 mM (20-600 mg/L) range, which was sufficient for monitoring the therapeutic anti-inflammatory dose. SPE followed by DIOS-MS is anticipated to be a method of measuring drug levels in blood and may allow high throughput analysis.     

Speciation of chromium (III) and chromium (VI) by capillary electrophoresis with contactless conductometric detection and dual opposite end injection

A sensitive, rapid and inexpensive capillary electrophoretic method for the determination of Cr(III) and Cr(VI) species is presented. The method is based on the dual opposite end injection principle and contactless conductometric detection. The sample containing cationic and anionic species is injected into the opposite ends of the separation capillary and after the high voltage is applied, the analytes migrate towards the capillary center, where the cell of a contactless conductivity detector is placed. The method does not require any sample pretreatment, except dilution with deionized water. The separation of Cr(III), Cr(VI) and other common inorganic anions and cations is achieved in less than 4 min. The parameters of the separation electrolyte solution, such as pH and concentration of L-histidine, were optimized. Best results were achieved with electrolyte solution consisting of 4.5 mM L-histidine, adjusted to pH 3.40 with acetic acid. The detection limits achieved for Cr(III) and Cr(VI) were 10 and 39 microg.L(-1), respectively. The repeatability of migration times and peak areas was better than 0.3% and 2.8%, respectively. The developed method was applied to the analyses of rinse water samples from the galvanic industry. The results for the determination of Cr(III) and Cr(VI) were in good agreement with the results obtained by certified differential spectrophotometric method using diphenylcarbazide (CN 83 0520-40) and with the results for the total chromium concentrations determined by electrothermal atomic absorbance spectrometry (ET-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS).     

Separation of polythionates and the gold thiosulfate complex in gold thiosulfate leach solutions by ion-interaction chromatography

A method for the separation of the polythionates (SxO6(2-), x = 3-5) in gold thiosulfate leach solutions using ion-interaction chromatography with conductivity and ultraviolet (UV) detection is described. Polythionates were eluted within 18 min using an eluent comprising an acetonitrile step gradient at 0.0 min from 15% v/v to 28% v/v, 3 mM TBAOH, and 2.5 mM sodium carbonate, operated using a Dionex NS1-5 micron column with guard. The developed method was capable of separating the gold thiosulfate complex ion in standard solutions, but quantification of this species in realistic leach solutions proved impractical due to a self-elution effect that caused the gold peak to be eluted as a broad band. Detection limits for polythionates using a 10 microL injection volume ranged between 1-6 mg L(-1) (5-23 microM) for conductivity and 0.8-13 mg L(-1) (4-68 microM) for UV detection, based on a signal-to-noise ratio of 2. Calibration was linear over the ranges 5-2000, 10-2000 and 25-2500 mg L(-1) for trithionate, tetrathionate and pentathionate, respectively. The technique was applied successfully to leach liquors containing 0.5 M ammonium thiosulfate, 2 M ammonia, 0.05 M copper sulfate and 20 % m/v gold ore.     

A simple and sensitive HPLC-fluorescence method for quantification of MDMA and MDA in blood with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label

A sensitive high-performance liquid chromatographic method with fluorescence detection to determine 3,4-methylenedioxymethamphethamine (MDMA) and 3,4-methylenedioxyamphethamine (MDA) in human and rat whole blood or plasma samples was developed by using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. MDMA and MDA in a small amount of blood sample (ca 100 microL) were extracted by liquid-liquid extraction with ethyl acetate, and were derivatized with DIB-Cl under mild conditions (10 min at room temperature). A good separation of DIB-derivatives could be achieved within 45 min using a commercially available ODS column with an isocratic eluent of 10 mM citric acid-20 mM Na(2)HPO(4) aqueous buffer (pH 4.0)-CH(3)CN-CH(3)OH (50:45:5, v/v/v %). The calibration curves prepared with 1-methyl-3-phenylpropylamine (MPPA) as an internal standard showed good linearity (r = 0.999) with 0.36-0.83 ng/mL detection limit at a signal-to-noise ratio of 3. MDMA and MDA in rat whole blood could be monitored for 6 h after a single administration of MDMA (2.2 mg/kg, i.p.). The pharmacokinetic parameters for MDMA and MDA obtained by triplicate measurements were 426 +/- 23 and 39 +/- 6 ng/mL (C(max)), 20 +/- 5 and 100 +/- 10 min (T(max)), respectively.     

Separation and on-line concentration of bisphenol A and alkylphenols by micellar electrokinetic chromatography with cationic surfactant

The separation and on-line concentration of bisphenol A and three alkylphenols were investigated by micellar electrokinetic chromatography with cationic surfactant. Tetradecyltrimethylammonium bromide was used as surfactant and the separation conditions were optimized by the addition of the organic solvents and cyclodextrins to the running solution. The separation of hydrophobic analytes and 4-nonylphenol isomers was improved by the addition of 20% acetonitrile and 20 mM beta-cyclodextrin to the running solution. When the sweeping with the running solution used as the on-line concentration procedure, 56-, 67- and 29-fold increase in detection sensitivity of bisphenol A, 4-tert.-butylphenol and 4-(1,1,3,3-tetramethylbutyl)phenol, respectively. The detection limits were 0.030, 0.098 and 0.159 mg/l, respectively.     

Improved determination of taurine by high-performance anion-exchange chromatography with integrated pulsed amperometric detection (HPAEC-IPAD)

The advantages of the high selectivity of high-performance anion-exchange chromatography (HPAEC) and the sensitive response of taurine at a gold electrode with integrated pulsed amperometric detection (IPAD) have been combined, in order to establish a new analytical method for its determination in real matrices. Potential-time settings of the potential waveform were optimized in order to get the highest amperometric response. The separation of taurine in milk samples was achieved using an alkaline eluent (100 mM NaOH) containing 1 mM Ba(OAc)₂ and a column temperature of 15 °C. The inherent merits of using a barium-modified eluent, in terms of taurine separation and detection, are demonstrated. The enhancement in sensitivity under these experimental conditions makes it suitable for taurine determination in milk. Indeed, this method allows high recovery of taurine and satisfies the necessary requirements with respect to accuracy, repeatability and sensitivity with a detection limit of 50 nmol/L, which corresponds to 2.5 pmol. The taurine content in milk samples of some common mammals was evaluated, including human milk. In goats milk, the taurine content ranged from 46 to 91 mg/L, whereas human and buffalo milk samples exhibited an average content of 18 mg/L and 23 mg/L, respectively.     

Determination of mannitol and sorbitol in infusion solutions by capillary zone electrophoresis using on-column complexation with borate and indirect spectrophotometric detection

Capillary zone electrophoresis with indirect UV detection at 215 nm was applied for the separation and determination of mannitol (MA), sorbitol (SO) and xylitol in the form of anionic borate-polyol complexes. The separation was carried out in a fused silica capillary (total length 60 cm, effective length 50 cm, I.D. 50 microm) at 25 kV. The optimized background electrolyte was 200 mM borate buffer (pH 9.3, adjusted with triethylamine) containing 10 mM 3-nitrobenzoate as the chromogenic co-ion. The separation took approximately 13 min. The rectilinear calibration range was 0.2-2 mg mL(-1) for MA and SO when using xylitol (1 mg mL(-1)) as the internal standard. The limit of detection at a S/N of 3 was approximately 30 microg mL(-1) for either analyte. The method was used for the assay of MA or SO in pharmaceutical infusion solutions. The RSD values were 0.15% or 1.07% (n=6) when determining 100 mg mL(-1) of MA or 50 mg mL(-1) of SO in commercial infusion solutions. The results were in good agreement with those of pharmacopoeial iodimetric titration.     

Analysis of choline and atropine in hairy root cultures of Cannabis sativa L. by capillary electrophoresis-electrospray mass spectrometry

We describe a capillary zone electrophoresis method coupled to electrospray ionization (ion trap) mass spectrometry (CZE-ESI-MS) for the identification and determination of choline and atropine compounds in hairy root extracts from Cannabis sativa L. Fused-silica capillary and an alkaline solution of 20 mM ammonium acetate at pH 8.5 are used being the most suitable for the analysis of choline and atropine in less than 10 min. Under the optimized conditions, including CE and ESI-MS parameters, the method resolved both compounds with very high sensitivity. The system exhibited good linear response in the range of 25-500 mg/L and 500-1000 microg/L for choline and atropine, respectively. The detection limit of choline was 18 mg/L and 320 microg/L for atropine. Finally, the developed method was applied to the analysis of these compounds in transgenic root cultures of Cannabis sativa L.     

Simultaneous determination of Fe(II) and Fe(III) in waters by capillary isotachophoresis

An ITP method for the simultaneous determination of Fe(II) and Fe(III) in waters, based on separation of their EDTA and fluoride complexes, respectively, was developed. The leading electrolyte used consists of chlorides, La(III) as co-counter ion and is buffered with β-alanine to pH = 3.5. The terminating electrolyte contains caproic acid and L-histidine (pH = 4.5). The method was validated and tested with samples of artificial, ground and treated water with good results, comparable to those obtained by other analytical techniques. Fe(II) and Fe(III) up to 20 mg/L were measured with an RSD = 1.4–1.5% and detection and determination limits of 0.8–0.9 and 3.0–3.5 mg/L, respectively. The ITP method can be recommended for routine utilization in hydroanalytical laboratories.     

Microemulsion electrokinetic chromatography for the separation of retinol, cholecalciferol, delta-tocopherol and alpha-tocopherol

A microemulsion electrokinetic chromatographic method was used to separate fat-soluble vitamins. The separation of retinol, cholecalciferol, and delta- and alpha-tocopherol was performed using a microemulsion containing 0.75% (v/v) n-heptane, 30 mM bis(2-ethylhexyl)sodium sulfosuccinate (AOT), 5% (v/v) 1-butanol, 15% (v/v) 1-propanol and 15% (v/v) methanol in 20mM boric acid-sodium borate buffer. The effect of the different microemulsion constituents was studied, including the type and concentration of surfactant, buffer, oil and co-surfactants. The presence of methanol in the microemulsion was found to be necessary to achieve the separation of the tocopherols. Detection was carried out at 200, 265 and 325 nm for the tocopherols, cholecalciferol and retinol, respectively. Calibration curves and precision data were obtained for each analyte. Good linear relationships were found between the analytical signal and the analytes concentration in the 25-500 mg L(-1) for retinol and cholecalciferol, and 25-300 mg L(-1) for tocopherols ranges. The precision of the method afforded relative standard deviations in the 4.0-10% range.     

Multielemental determination of arsenic, selenium and chromium(VI) species in water by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

A new method for the simultaneous chromatographic separation and determination of arsenite, arsenate, mono-methylarsonic acid, dimethylarsinic acid, selenite, selenate and hexavalent chromium in water is presented. Speciation was achieved by on-line coupling of anion-exchange LC and inductively coupled plasma mass spectrometry (ICP-MS). Optimisation of the chromatographic conditions led to baseline separation of the seven species in 14 min using gradient elution with NH4NO3 20 mM, pH 8.7-NH4NO3 60 mM, pH 8.7 as mobile phase. Detection limits are in the range 40-60 ng l(-1) for arsenic species, around 130 ng l(-1) for Cr(VI), and higher for Se(IV) and Se(VI) (1.2 and 1.4 microg l(-1) respectively). The method showed good accuracy and repeatability, and no interference of chloride on 75As, 77Se or 53Cr was observed. The developed method was applied to the analysis of several environmental surface water samples.     

Micellar electrokinetic chromatography profiles of human high-density lipoprotein phospholipids

A simple and fast micellar electrokinetic chromatography (MEKC) method was developed to investigate phospholipids isolated from human high-density lipoproteins (HDL). To optimize the MEKC conditions, several factors including bile salt concentration and organic modifier concentration in the separation buffer as well as temperature have been examined. The optimal separation buffer chosen was a mixture of 50 mM bile salts, 30% v/v 1-propanol and 10 mM sodium phosphate (pH 8.5). The applied voltage and temperature selected were 25 kV and 40°C, respectively. Meanwhile, high-salt stacking has been performed for sample pre-concentration to enhance peak sensitivity. Several factors including organic modifier concentration and salt concentration in the sample matrix as well as sample injection time have been optimized. The optimal sample buffer selected was a mixture of 100 mM NaCl and 20% 1-propanol, and the optimal sample injection time selected was 32 s under a pressure of 0.5 psi. Several phospholipid standards including lysophosphatidyl choline, phosphatidyl choline (PC), sphingomyelin, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl serine and phosphatidic acid have been studied using the optimal MEKC method. The MEKC profile of the mixed phospholipid standards showed good separation and reproducibility. The linear ranges for PC and sphingomyelin were 0.025-1.2 and 0.025-2.0 mg/mL, respectively. The concentration limits of detection of PC and sphingomyelin were 0.0156 and 0.0199 mg/mL, respectively. Using phosphatidic acid as an internal standard, precision and accuracy have been measured for PC and sphingomyelin. The intraday and interday quantitative analysis showed good results. The new MEKC method has been used to characterize native, in vitro oxidized and glycated human HDL phospholipids within 16 min. At absorbance 200 nm, two similar peaks were observed for native and oxidized HDL phospholipids, but three peaks were observed for glycated HDL phospholipids. Interestingly, at absorbance 234 nm, distinctively different MEKC profiles were observed for the three HDL phospholipids.