Determination of inorganic ions in mineral water by gradient elution moving boundary electrophoresis

A sensitive method was developed for the determination of the major inorganic ions in commercial mineral waters using gradient elution moving boundary electrophoresis with capacitively coupled contactless conductivity detection. This application was the first to demonstrate the separation of cations and anions simultaneously using gradient elution moving boundary electrophoresis. Seven ionic analytes (calcium, chloride, magnesium, nitrate, potassium, sodium, and sulfate) were separated in less than 7 min with detection values in the low μmol/L to sub-μmol/L range. Calculated values of the major ions in three commercial mineral waters were compared to reported values with good correlation. In another application, phosphate and arsenate were separated in less than 2 min with limits of detection of 300 and 140 nmol/L, respectively. For all standard analyses, the RSD for migration times and peak areas were under 3%.     

High-sensitivity microchip electrophoresis determination of inorganic anions and oxalate in atmospheric aerosols with adjustable selectivity and conductivity detection

A sensitive and selective separation of common anionic constituents of atmospheric aerosols, sulfate, nitrate, chloride, and oxalate, is presented using microchip electrophoresis. The optimized separation is achieved in under 1 min and at low background electrolyte ionic strength (2.9 mM) by combining a metal-binding electrolyte anion (17 mM picolinic acid), a sulfate-binding electrolyte cation (19 mM HEPBS), a zwitterionic surfactant with affinity towards weakly solvated anions (19 mM N-tetradecyl,N,N-dimethyl-3-ammonio-1-propansulfonate), and operation in counter-electroosmotic flow (EOF) mode. The separation is performed at pH 4.7, permitting pH manipulation of oxalate's mobility. The majority of low-concentration organic acids are not observed at these conditions, allowing for rapid subsequent injections without the presence of interfering peaks. Because the mobilities of sulfate, nitrate, and oxalate are independently controlled, other minor constituents of aerosols can be analyzed, including nitrite, fluoride, and formate if desired using similar separation conditions. Contact conductivity detection is utilized, and the limit of detection for oxalate (S/N = 3) is 180 nM without stacking. Sensitivity can be increased with field-amplified sample stacking by injecting from dilute electrolyte with a detection limit of 19 nM achieved. The high-sensitivity, counter-EOF operation, and short analysis time make this separation well-suited to continuous online monitoring of aerosol composition.     

Identification of inorganic ions in post‐blast explosive residues using portable CE instrumentation and capacitively coupled contactless conductivity detection

Novel CE methods have been developed on portable instrumentation adapted to accommodate a capacitively coupled contactless conductivity detector for the separation and sensitive detection of inorganic anions and cations in post‐blast explosive residues from homemade inorganic explosive devices. The methods presented combine sensitivity and speed of analysis for the wide range of inorganic ions used in this study. Separate methods were employed for the separation of anions and cations. The anion separation method utilised a low conductivity 70 mM Tris/70 mM CHES aqueous electrolyte (pH 8.6) with a 90 cm capillary coated with hexadimethrine bromide to reverse the EOF. Fifteen anions could be baseline separated in 7 min with detection limits in the range 27–240 μg/L. A selection of ten anions deemed most important in this application could be separated in 45 s on a shorter capillary (30.6 cm) using the same electrolyte. The cation separation method was performed on a 73 cm length of fused‐silica capillary using an electrolyte system composed of 10 mM histidine and 50 mM acetic acid, at pH 4.2. The addition of the complexants, 1 mM hydroxyisobutyric acid and 0.7 mM 18‐crown‐6 ether, enhanced selectivity and allowed the separation of eleven inorganic cations in under 7 min with detection limits in the range 31–240 μg/L. The developed methods were successfully field tested on post‐blast residues obtained from the controlled detonation of homemade explosive devices. Results were verified using ion chromatographic analyses of the same samples.     

离子色谱同时分离测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子

建立了离子色谱-直接电导检测同时测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子(F-,Cl-,Br-,NO3-,SO24-)的方法。实验采用Shim-pack IC-A3阴离子交换色谱柱,分别选用对羟基苯甲酸-三(羟甲基)氨基甲烷-硼酸,邻苯二甲酸-三(羟甲基)氨基甲烷,邻苯二甲酸氢钾为淋洗液,考察了淋洗液种类,浓度及色谱柱温度对分离测定三氟甲烷磺酸根,氟硼酸根及常见无机阴离子的影响。最佳色谱条件为:以1.2mmol/L邻苯二甲酸氢钾为淋洗液,柱温30℃,流速1.0mL/min。在此条件下,可同时基线分离7种阴离子,且色谱峰形对称。所测阴离子的检出限(S/N=3)为0.02～1.88mg/L,保留时间和峰面积的相对标准偏差(n=5)分别小于0.17%和2.05%。应用本方法测定离子液体中三氟甲烷磺酸根,氟硼酸根及常见无机阴离子,加标回收率在97.0%～102.8%之间。本方法简单,准确,可靠,具有较好的实用性。     

Simultaneous analysis of six cardiovascular drugs by capillary electrophoresis coupled with electrochemical and electrochemiluminescence detection,using a chemometrical optimization approach

CE coupled with dual electrochemical (EC) and electrochemiluminescence (ECL) detection was optimized for simultaneous analysis of six cardiovascular drugs (alprenolol, propafenone, acebutolol, verapamil, atenolol and metoprolol) via central composite design. Following this study, three critical electrophoretic factors governing the CE separation were investigated: Tris‐H₃PO₄ buffer concentration, buffer pH value and separation voltage. A modified chromatographic response was adopted for evaluating CE separation quality. Optimum conditions were achieved using Tris‐H₃PO₄ buffer 35.6 mM (pH 2.3) separated at 13.9 kV, which was employed experimentally and led to the successful simultaneous separation of the above six drugs. The good agreement of the chromatographic response was observed between predicted data and actual experimental results using these optimized conditions (RSD=3.75%). The proposed method was validated for linearity, repeatability and sensitivity, and subsequently successfully applied to determine six basic drugs in urine samples.     

Determination of ammonium,calcium, magnesium,potassium and sodium in drinking waters by capillary zone electrophoresis on a column-coupling chip

This work deals with simultaneous determination of ammonium, calcium, magnesium, sodium and potassium in drinking waters by capillary zone electrophoresis (CZE) on a column-coupling (CC) chip with suppressed hydrodynamic and electroosmotic transports. CZE separations were carried out in a propionate background electrolyte at a low pH (3.2) containing 18-crown-6-ether (18-crown-6) to reach a complete resolution of the cations. In addition, triethylenetetramine (TETA) coated the inner wall surface of the chip channels. The concentration limits of detection (cLOD) for the studied cations ranged from 4.9 to 11.5 μg/l concentrations using a 900 nl volume of the sample injection channel. 93–106% recoveries of the cations in drinking waters indicate a good predisposition of the present method to provide accurate analytical results.     

Low-cost and versatile analytical tool with purpose-made capillary electrophoresis coupled to contactless conductivity detection: Application to antibiotics quality control in Vietnam

In this study, the development of our purpose-made capacitively coupled contactless conductivity detection (C⁴D) for CE is reported. These systems have been employed as a simple, versatile, and cost-effective analytical tool. CE-C⁴D devices, whose principle is based on the control of the ion movements under an electrical field, can be constructed even with a modest financial budget and limited infrastructure. A featured application was developed for quality control of antimicrobial drugs using CE-C⁴D, with most recent work on determination of aminoglycoside and glycopeptide antibiotics being communicated. For aminoglycosides, the development of CE-C⁴D methods was adapted to two categories. The first one includes drugs (liquid or powder form) for intravenous injection, containing either amikacin, streptomycin, kanamycin A, or kanamycin B. The second one covers drugs for eye drops (liquid or ointment form), containing either neomycin, tobramycin, or polymyxin. The CE-C⁴D method development was also made for determination of some popular glycopeptide antibiotics in Vietnam, including vancomycin and teicoplanin. The best detection limit achieved using the developed CE-C⁴D methods was 0.5 mg/L. Good agreement between results from CE-C⁴D and the confirmation method (HPLC- Photometric Diode Array ) was achieved, with their result deviations less than 8% and 13% for aminoglycoside and glycopeptide antibiotics, respectively.     

毛细管电泳-激光诱导荧光法测定草甘膦、草胺膦及氨甲基膦酸

建立了一种快速、有效的毛细管电泳分离-激光诱导荧光检测有机磷除草剂草甘膦、草胺膦和草甘膦的代谢物氨甲基膦酸的方法。将荧光衍生试剂5-(4, 6-二氯三嗪基)氨基荧光素(DTAF)成功用于衍生上述3种化合物。最佳衍生条件: DTAF的浓度为1.0 μmol/L,以50 mmol/L硼酸(pH 9.5)作为缓冲溶液,在30 ℃下反应40 min。以pH 9.5的30 mmol/L硼酸缓冲溶液(含15 mmol/L Brij-35)作为电泳背景电解质,3种衍生物得到基线分离。在优化的条件下,草甘膦、草胺膦、氨甲基膦酸的检出限分别为3.21、6.14和1.99 ng/kg。将该方法应用于环境水样和土壤中除草剂及代谢物的测定,回收率为91.3%～106.0%。该方法准确、灵敏,可满足环境样品中有机磷农药及其代谢物残留的检测要求。     

梯度淋洗-电导抑制离子色谱法同时测定果汁中26种有机酸和阴离子

通过对色谱柱类型、流速、柱温、pH值、淋洗液浓度等影响因素的研究,建立了多级梯度淋洗-电导抑制离子色谱同时测定果汁中26种有机酸和阴离子的分析方法。结果表明,当流速为1.00 mL/min、柱温为30℃、pH值为5.5~6.8时,26种组分的测定结果更准确。26种组分在0.02~10.0 mg/L范围内具有良好的线性关系（r均大于0.995）,检出限（S/N=3）为0.17~52.0 μg/L;在0.20~2.00 mg/L添加水平下的回收率为85.58%~108.86%,相对标准偏差为0.15%~7.65%（n=6）。该方法简便快速、灵敏度好、准确度高,适于果汁中26种组分的痕量分析。     

Simultaneous determination of diclofenac and its common counter‐ions in less than 1 minute using capillary electrophoresis with contactless conductivity detection

This paper presents a method for fast and simultaneous determination of diclofenac (DCF) and its common counter‐ions (potassium, sodium, and diethylammonium) using CE with capacitively coupled contactless conductivity detection (CE‐C⁴D). On the basis of a single electropherogram (about 50 s), the proposed method allows the determination of the stoichiometry, absolute quantification and evaluation of the degradation degree of the active pharmaceutical ingredient (DCF). A linear working range from 100 to 500 μmol/L was obtained for all analytes in an equimolar TRIS/TAPS (10 mmol/L) solution as the background electrolyte as well as adequate LOD (7, 6, 7, and 10 μmol/L for K⁺, Na⁺, diethylammonium, and DCF, respectively). The proposed method was applied to the analysis of pharmaceutical formulations (tablets and spray form) with similar results to those achieved by HPLC (DCF) or flame photometry (K and Na) at a 95% confidence level.     

Pressure-assisted capillary electrophoresis for cation separations using a sequential injection analysis manifold and contactless conductivity detection

Pressure assisted capillary electrophoresis in capillaries with internal diameters of 10 μm was found possible without significant penalty in terms of separation efficiency and sensitivity when using contactless conductivity detection. A sequential injection analysis manifold consisting of a syringe pump and valves was used to impose a hydrodynamic flow in the separation of some inorganic as well as organic cations. It is demonstrated that the approach may be used to optimize analysis time by superimposing a hydrodynamic flow parallel to the electrokinetic motion. It is also possible to improve the separation by using the forced flow to maintain the analytes in the capillary, and thus the separation field, for longer times. The use of the syringe pump allows flexible and precise control of the pressure, so that it is possible to impose pressure steps during the separation. The use of this was demonstrated for the speeding up of late peaks, or forcing repeated passage of the sample plug through the capillary in order to increase separation.     

高效液相色谱-双波长检测-梯度洗脱法同时测定小儿氨酚烷胺颗粒中的3种有效组分

建立了高效液相色谱(HPLC)-双波长检测-梯度洗脱同时测定小儿氨酚烷胺颗粒中对乙酰氨基酚、咖啡因和马来酸氯苯那敏含量的分析方法。采用的色谱条件: 以Diamonsil C18色谱柱(4.6×200 mm, 5 μm)为分离柱,以乙腈和0.1%三乙胺水溶液(用磷酸调pH至3.7±0.5)为流动相进行梯度洗脱,流速1.0 mL/min,检测波长为280 nm和210 nm,柱温为30 ℃,进样量为5 μL。结果表明,对乙酰氨基酚、咖啡因和马来酸氯苯那敏的线性范围均比较宽(依次为2.4～60、0.14～3.6、0.019～0.48 μg),平均加标回收率均不低于99.0%,而且方法操作简单,重现性好,测定结果准确,可用于更好地控制该制剂的质量。     

液液萃取-场放大进样-毛细管电泳非接触式电导分离检测酱油中的安赛蜜

采用场放大进样(FASI)-毛细管电泳非接触式电导检测法(CE-C⁴D),结合液液萃取(LLE)的样品净化预处理技术,分离检测了酱油中人工合成甜味剂安赛蜜。酱油样品经酸化后,用乙酸乙酯作为萃取剂,成功地消除了酱油中含有的大量无机盐等复杂基体对微量安赛蜜的干扰。实验对影响LLE萃取效率和FASI-CE-C⁴D分离检测的关键因素进行了讨论,特别是对样品净化前处理过程中萃取剂及用量、样品酸化pH值、萃取时间、萃取温度等条件进行了优化。结果表明,酱油中的安赛蜜可获得良好分离和灵敏检测,检出限和定量限分别为0.15 mg/kg和0.48 mg/kg。对市售酱油样品进行安赛蜜的加标回收测定,得到加标回收率为92.3%～108.1%,相对标准偏差<8.0%。该法具有简单快速、灵敏高效、分析成本低的优点,能满足酱油中安赛蜜的分析检测要求。     

Determination of Ca, K, Mg, Na, sulfate, phosphate, formate, acetate, propionate, and glycerol in biodiesel by capillary electrophoresis with capacitively coupled contactless conductivity detection

In this work, a new method employing capillary electrophoresis (CE) for the determination of several species in biodiesel is introduced. The concentrations of inorganic species (Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄²⁻, and PO₄³⁻) and glycerol are of interest to the regulatory authorities due to their ability to form undesirable compounds in engines. Additionally, other species of low molecular weight (e.g., acetate, formate, and propionate) are of interest because they contribute towards increasing the acidity. These species are formed by the degradation of biodiesel and cause damage to engines and the environment. The cation separation was performed in background electrolyte (BGE) composed of 30 mmol L⁻¹ of 2-(n-morpholino)ethanesulfonic acid (MES)/L-histidine (His), pH 6. The separation of anionic species was carried out in similar BGE with 0.2 mmol L⁻¹ cetyltrimethylammonium bromide (CTAB) added. For glycerol, a neutral species, its oxidation with periodate was employed. This well-known reaction is specific to polyols and generates iodate. The amount of iodate produced by the reaction was determined by CE. The separation was carried out in approximately 1 min using BGE composed of 30 mmol L⁻¹ acetic acid, pH 3. The analytical parameters evaluated were: linearity (r > 0.99), the RSD values for area and migration time were < 3.4% and 0.9%, respectively, and recovery was in the range of 89 to 107%.