High-resolution determination of H+ by ion chromatography. Application to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain.

An ion chromatographic (IC) method was developed for the high-resolution determination of a sample's free hydrogen ion concentration (H+). Highly purified lithium dodecyl sulfate was used as the stationary phase, a slightly acidified aqueous LiCl solution was used as the mobile phase and conductivity was used for analyte detection. An electrical double layer (EDL) containing H+ was established on the stationary phase by using a slightly acidified electrolyte solution as the eluent. H+ in the EDL protonated any weak acid groups (i.e., silanols) on the stationary phase so that H+ from the sample could be retained/separated purely by dodecyl sulfate. The optimum molar ratio of H+:Li+ in the EDL for this IC system was obtained by using an aqueous solution containing 40.0 mM LiCl and 0.07 mM H2SO4 as the eluent. After separation, H+ was detected by direct conductimetric measurement. An H+ detection limit of better than 8.2 x 10(-6) M was obtained from the analysis of standard aqueous H2SO4 solutions. Other monovalent cations could also be separated with this method, giving detection limits of 7.4 x 10(-5), 4.3 x 10(-5) and 4.2 x 10(-5) M for Na+, NH4+ and K+, respectively. The method was applied to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain. The results obtained showed a significant improvement in reproducibility when compared with those from a conventional pH-meter. Acid rain samples with a pH < 5 could be analyzed with this IC system.     

Development of an HPLC method for determining the alpha 2-adrenergic receptor agonist brimonidine in blood serum and aqueous humor of the eye

A procedure for determining brimonidine [5-bromo-6-(2-imidazolidinylideneamino) quinoxaline] in biological samples using a reversed-phase isocratic HPLC method is described. The application in blood serum and eye aqueous humor of patients treated with the Alphagan ophthalmic solution was carried out by enrichment of samples in brimonidine with solid-phase liquid extraction. Brimonidine reached maximum levels in aqueous humor and serum within 2-2.5 h, whereafter a declining pattern was obtained. An approximate 50% level of brimonidine was identified in serum at 12 h after ocular administration, whereas in aqueous humor this percentage was determined after a period of 4-5 h.     

原子吸收法测定环境水样中化学需氧量

在Ｈ２ＳＯ４介质中用Ｋ２Ｃｒ２Ｏ７同ＣＯＤ水样反应,反应后水相中过量的Ｃｒ（Ⅵ）以Ｃｒ２Ｏ２－７形式被ＴＯＡ萃入有机相中,而生成的Ｃｒ（Ⅲ）则留在水相,用ＡＡＳ测定有机相中的Ｃｒ（Ⅵ）或水相中的Ｃｒ（Ⅲ）都可求得ＣＯＤ含量。本法简便快速、需样量少、且测定结果同标准方法（ＣＯＤＣｒ法）一致,回收率为９８％～１０８％,平均标准偏差为３．３％。     

Determination of total gaseous lead in the atmosphere by honeycomb denuder/electrothermal atomic absorption spectrometry.

A technique is described for the determination of total gaseous lead in the atmosphere by honeycomb denuder collection, followed by an electrothermal atomic absorption spectrometry (ETAAS) measurement. The collection efficiency of the honeycomb denuder in which a solution containing 2% HNO3/2% glycerine/1% ammonium dihydrogenphosphate was coated for trapping the gaseous lead in the atmosphere was 98.8%. The linear absorbance response was obtained for a concentration range of 0-1.39 microg m(-3) of lead in the atmosphere. A precision of 4.8% RSD (peak-height absorbance, n = 11) for an aqueous solution of 1 ng of lead standard, characteristic masses (CM) of 23 pg and detection limit (3sigma) of 54 pg for an aqueous solution of 0.01 ng lead standard was achieved with 100 microg ammonium dihydrogenphosphate as a chemical modifier. The average recovery of lead in three standard samples prepared by the independent digestion of NIST SRM 1648 (Urban Particulate Matter) using our analytical system was 97.8%. The total content of the gaseous lead in the atmosphere of our laboratories was 0.35-0.38 microg m(-3).     

Capillary electrophoretic analysis of brimonidine in aqueous humor of the eye and blood sera and relation of its levels with intraocular pressure

The aim of this study was the development of a capillary electrophoretic method for the determination of the levels of the selective alpha(2)-adrenergic receptor agonist brimonidine in aqueous humor of the eye and blood sera and their relation to its efficacy in reducing the intraocular pressure (IOP). Analysis of brimonidine was performed by capillary zone electrophoresis using 20 mM borate, pH 9.3, as operating buffer and detection at 255 nm. Brimonidine levels were determined in aqueous humor and blood sera from seven patients admitted for cataract extraction following ocular administration of the ophthalmic Alphagantrade mark solution. Levels of brimonidine and IOP values were recorded for a 24 h period. Alphagantrade mark administration resulted in a significant reduction of IOP, from within 30 min up to 4-5 h, whereafter a stepwise increase was recorded until 24 h, where mean IOP value returned to that before administration. The IOP reduction was related to the levels of brimonidine in aqueous humor, where maximal levels (80-100%) were obtained within 1-3 h. A 50% amount of the solution was determined after 4-5 h, whereas it reached the minimum level after 12 h. Serum levels reached maximum within 3-4 h, a 50% reduction was recorded in 12 h and minimum level in 24 h. It is concluded that brimonidine administration may significantly reduce IOP in patients when its level is maintained >/=50% of the maximum present in aqueous humor, i.e within a 4-6 h period. Since at this time the level of brimonidine in blood serum has reached maximum value, administration of brimonidine every 6 h may be used to obtain adequate brimonidine levels to maintain a constantly lowered IOP.     

Determination of monovalent inorganic anions in high-ionic-strength samples by electrostatic ion chromatography with suppressed conductometric detection

A new ion chromatographic (IC) system has been established by using micelles of 3-(N,N-dimethylmyristylammonio)propanesulfonate (Zwittergent 3-14) loaded onto a reversed-phase packed column as the separation column with an electronic rotary switching valve packed-bed suppressor for conductometric detection of inorganic anions. An aqueous H3BO3-Na2B4O7 solution has been demonstrated to be the most desirable eluent for this IC system. The relationship between retention time and the concentration of the borate eluent was determined for a series of model anionic analytes and this relationship was found to be opposite to that exhibited in a conventional anion-exchange IC system. The rapid elution and complete separation of monovalent inorganic anions were obtained by initially using a high-concentration borate solution as the eluent for a short-period, and then switching to a lower-concentration borate eluent to complete the separation. Detection limits for nitrite, bromide, nitrate, and chlorate were 0.85, 0.88, 0.95 and 4.8 microM, respectively, when a 7.0 mM Na2B4O7 eluent was used. Moreover, the ability to directly detect these monovalent anions in samples containing high concentrations of sulfate and/or chloride ions provided a major advantage of this approach.     

A unified ion chromatographic system for the determination of acidity and alkalinity.

A unified ion chromatographic (IC) system was developed for the determination of acidity or alkalinity. Separation column used was a reversed-phase ODS packed column, which had been modified by saturating it with lithium dodecylsulfate. A slightly acidified LiCl (50 mM LiCl and 0.05 mM H2SO4) aqueous solution was used as the eluent. By conditioning the separation column in this way, both H+ and Li+ ions became bound to the stationary phase. Dodecylsulfate groups with Li+ counterions acted as cation-exchange sites for the separation of hydrogen ions (free acidity determination). The remaining dodecylsulfate groups, with H+ counterions acted as a titrant, which reacted with basic species (total alkalinity determination). The acidity or alkalinity of each sample was measured according to the change in conductance from the eluent baseline level. A positive peak was observed from those samples with a free acidity greater than their total alkalinity, due to the separation/elution of free H+ ions. A negative peak was observed from those samples with a free acidity less than their total alkalinity. This was due to an equivalent amount of eluent H+ ions being re-supplied to the stationary phase while the "solid titrant" consumed by the acid-base reaction was regenerated. The retention time for the peak corresponding to the acidity or alkalinity was governed by the retention time for H+ ions in this IC system. Samples with a free acidity greater than 2.25 microM (tested by determination of H+ ions in pure water in equilibrium with atmospheric CO2) could be analyzed by this method. A very similar detection level was obtained for alkalinity (tested by analyzing standard aqueous NaHCO3 solutions). Aqueous solutions of some strong-acid/strong-base inorganic salts were found to be slightly alkaline. This was measured as a percentage, relative to an NaHCO3 solution at the same concentration. Solutions of NaClO4, Na2SO4, NaI, NaNO3, and NaCl, gave comparative alkalinity values of 8.75%, 1.83%, 0.42%, 0.35%, and 0.33%, respectively.     

On-line collection/concentration and detection of sulfur dioxide in air by flow-injection spectrophotometry coupled with a chromatomembrane cell.

A simple and rapid procedure for SO2 determination in air was developed by using a flow injection analysis (FIA) system coupled with a 3-hole chromatomembrane cell (CMC). The CMC was applied for the on-line collection/concentration of SO2 from air into a solution of 2 g l(-1) triethanolamine (TEA) solution as an absorbing solution: SO2 was converted to SO3(2-) in the alkaline absorbing solution. The solution containing absorbed SO2 was introduced into the carrier stream of the FIA system. The amount of SO3(2-) in the absorbing solution was measured by spectrophotometry with a mixed reagent of pararosaniline and formaldehyde, and was converted to the concentration of SO2 in the air sample. A calibration graph prepared by using standard sodium sulfite aqueous solutions was adopted for the determination of SO3(2-) in the absorbing solution. The SO2 concentration in indoor air examined was found to be 22.7 +/- 0.2 ppbv using 20 ml of air sample with the air flow rate of 5 ml min(-1), where the relative standard deviation was 1.7%. The detection limit for aqueous solutions and air samples were 6.9 x 10(-8) M and 0.48 ppbv, respectively. The measuring time for one sample was about 10 min when a 20 ml air sample was used. The interferences from common anionic species, formaldehyde and acetaldehyde, were also examined.     

高效液相色谱-二极管阵列检测器同时测定化妆品中的九种染料及中间体

建立了用高效液相色谱-二极管阵列检测器(HPLC-PDA)同时检测9种染料及中间体的系统方法。首先采用超声提取的方法处理样品,对提取溶剂和提取时间进行了选择,确定用甲醇-0.01 mol/L 乙酸铵(体积比为2∶1)作提取溶剂,超声提取20 min。然后,采用C18柱,以甲醇-0.01 mol/L乙酸铵(pH 6.2)为流动相梯度洗脱,用PDA检测。以保留时间定性,并以紫外吸收光谱图辅助定性,以外标法定量。定量检测波长为230 nm,15 min内可对9种目标物同时进行测定,且各化合物都达到基线分离(分离度大于1.5)。经测定,该方法的平均回收率(n=8)为81.0%～105.6%,相对标准偏差（RSD）为0.8%～4.9%,检出限(以信噪比为3计)为0.1～2 μg。该方法简单、快速,能有效提取和分离测定化妆品中9种染料及中间体。将该方法用于实际化妆品样品的检测,结果令人满意。     

Simultaneous determination of methotrexate and metoclopramide in physiological fluids using RP-HPLC with ultra-violet detection; application in evaluation of polymeric nanoparticles

Methotrexate (MTX) is an anticancer drug while metoclopramide (MCP) is an antiemetic agent. Both the drugs are commonly coprescribed to avoid the emesis caused by anticancer drug. In this study, a novel, rapid, sensitive, and cost-effective reverse-phase high-performance liquid chromatography method was developed and validated for simultaneous determination of the methotrexate and metoclopramide in biological and pharmaceutical samples using sparfloxacin as internal standard. The analytes were separated on a Kromasil 100-5C18 RP (250?×?4.6?mm, 5?µm) column, methanol, and 0.05% trifloroacetic acid (36:64?v/v) as mobile phase with a flow rate of 1?mL/min, detection wavelength of 290?nm, and column oven temperature at 40°C. Both the analytes were extracted from physiological fluids (bovine aqueous humor, vitreous humor, and human plasma) using mixture of methanol and 10% perchloric acid (50:50 v/v). The method was linear over the concentration range of 0.025–1.0?µg/mL for methotrexate and 0.030–1.0?µg/mL for metoclopramide. The % recovery from human plasma was 98.57 and 96.74% for MTX and MCP, respectively, while from aqueous humor and vitreous humor was 95.84 and 98.51% for MTX.

The developed method was applied for in vitro release of MTX from polymeric nanoparticles and can be applied for analysis of pharmaceutical and biological samples containing both the drugs.     

High Performance Liquid Chromatographic Assay of Methoclopramide in Plasma Using a Silica Gel Column and An Aqueous Meobile Phase

Abstract

A high performance liquid chromatographic method for quantitating matoclopramide in plasma is presented. Proteins ara precipitated from the plasma sample with acetonitri la containing the internal standard, procainamida. The treated samples ara than analyzad using an Ultrasphere Si column, an aqueous solution at pH 7 of 65% CH³CN and 5.0 mM (NH₄)₂HPO₄ as a mobile phase, and a fluorescence detector. The retention times for drug and intarna1 standard ara 11.2 and 13.2 min, respectively. The caibration curve is Linear from 0.89 to 44.5 ng/ml. The detection limit is 0.89 ng/ml [signaL/hoisa = 31] for 0.2 ml plasma samples Pracision is measured by intraday and intarday coefficients o f variation, which are less than 10%. This method is currently being used for pharmacokinetic studies of methoclopramide.     

酸性媒染紫-示波计时电位法测定天然水和饮用水中铝

报道酸性媒染紫（ＳＶＲＳ）－示波计时电位法测定天然水及饮用水中铝。在０．８５ｍｏｌ／Ｌ　ＮＨ３·Ｈ２Ｏ－ＮＨ４Ｃｌ－５×１０－５ｍｏｌ／Ｌ ＳＶＢＳ（ｐＨ８．８）底液中,Ａｌ－ＳＶＲＳ络合物在－１．０５Ｖ电位处产生灵敏切口,切口深度与铝浓度成正比,可用于定量分析。线性范围为１×１０－７～６×１０－６ｍｏｌ／Ｌ． ＲＳＤ为５．５％ （ｎ＝１０,２×１０－７ｍｏｌ／Ｌ）,检测限为５×１０－８ｍｏｌ／Ｌ。本法特点为：在碱性条件下,无需加热,无需通氮除氧,无需预富集,大大减少了分析时间。仪器简单,方法灵敏准确,特别适用于天然水和饮料中Ａｌ的分析。对实际水样进行了分析,与ＩＣＰ／ＡＥＳ法所测结果基本一致。     

水合偏硼酸钾的热化学研究

Hydrated potassium monoborate(KBO₂·4/3H₂O) was obtained from an aqueous solution in a mole ratio of K₂O∶B₂O₃=2∶1 and characterized by powder X-ray diffraction(XRD)， infrared spectroscopy(FT-IR) and Raman spectroscopy. The enthalpy of solution of hydrated potassium monoborate， KBO₂·4/3H₂O， in approximately 1mol·dm^-3 aqueous hydrochloric acid was determined. Together with the previously determined enthalpies of so-lution of H₃BO₃ in approximately 1mol·dm^-3 HCl(aq) ，and of KCl in aqueous(hydrochloric acid+boric acid)， the standard molar enthalpy of formation of -(1411.11±0.84)kJ·mol^-1 for KBO₂·4/3H₂O was obtained from the standard molar enthalpies of formation of KCl(s)， H₃BO₃(s)， and H₂O(l). The standard molar entropy of formation of -422.94J·K^-1·mol^-1 and standard molar entropy of 163.47J·K^-1·mol^-1 for KBO₂·4/3H₂O were calculated from the thermodynamic relations. A group contribution method is applicable to KBO₂·4/3H₂O.     

不同剂型药用抑肽酶纯度的胶束电动毛细管测定

 以十六烷基三甲基溴化铵 (CTAB)为阳离子表面活性剂 ,用胶束电动毛细管 (MECC)分别对抑肽酶粉针剂和抑肽酶注射液进行纯度测定。实验中选择了最佳缓冲液 (含 4mmol/LCTAB的 80mmol/LNa2 HPO4 H3 PO4,pH 7 0 0 ) ,考察了进样量与样品中高浓度盐对分离的影响。并对毛细管区带电泳、MECC和高效液相的分离效果加以比较 ,表明MECC的分离效果最佳。     

An optimized on-line preconcentration system for analysis of trace gold in ore samples

A flow injection on-line preconcentration technique, combined with graphite furnace atomic absorption spectrometry for the determination of gold in ore samples has been presented. An alpha-amino pyridine resin (AP) was loaded onto a microcolumn as the preconcentration reagent and a solution of 90% acetone-5% HCl-5% H(2)O was used for the gold elution. The Scaled Simplex Method was employed to optimize the flow injection manifold. The selected factors were optimized by the simultaneous consideration of two responses, absorbance and column retention efficiency, with only 12 tests. A detection limit of 0.065 mug Au/l (3sigma) with a relative standard deviation of 4.3%, was achieved. Ore samples containing gold have been analysed successfully using the proposed method.     

A facile and sensitive chemiluminescence detection of amino acids in biological samples after capillary electrophoretic separation

It was found that native amino acids enhanced the chemiluminescence (CL) reaction between luminol and BrO(-) in an alkaline aqueous solution. This has led to the development of a facile and highly sensitive CL detection scheme for the determination of amino acids in biological samples after capillary electrophoretic (CE) separation. The CE-CL conditions were optimized. An electrophoretic buffer of 2.5 x 10(-2) M sodium borate (pH 9.4) containing 1 x 10(-4) M luminol was used. The oxidizer solution of 8 x 10(-4) M NaBrO in 0.1 M sodium carbonate buffer solution (pH 12.5) was introduced post-column. Under the optimal conditions, the detection limits were 1.0 x 10(-7) M for glutamic acid (Glu) and 1.3 x 10(-7) M (S/N = 3) for aspartic acid (Asp). The relative standard deviations (RSDs) of peak area and migration time were in the ranges of 3.8-4.3% and 1.4-1.6%, respectively. The present method was applied to the determination of excitatory amino acids (i.e., Asp and Glu) in rat brain tissue and monkey plasma. The levels of these major excitatory amino acids in monkey plasma were quantified for the first time and found to be 1.17 +/- 0.17 x 10(-5) M (mean +/- SD, n = 6) for Glu and 1.64 +/- 0.19 x 10(-6) M for Asp, which were comparable with the levels in human plasma.     

Determination of chlorophenols in environmental water samples using directly suspended droplet liquid-liquid-liquid phase microextraction prior to high-performance liquid chromatography

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5?mL acidic donor phase, (pH 2, P1) into an organic phase, 350?µL?of benzene/1-octanol (90?:?10 v/v, P2) and then were back-extracted into a 7?µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe and neutralised by adding of 7?µL HCl 0.1?M. The total amount was eventually injected into the HPLC system with UV detection at 225?nm for further analysis. Parameters such as the organic solvent, phases volumes, extraction and back-extraction times, stirring rate and pH values were optimised. The calibration graphs are linear in the range of 10–2000?µg?L^?1 with r?≥?0.9973. The enrichment factors were ranged from 115 to 170, and the limit of detection (LOD, n?=?7) varied from 5 to 10?µg?L^?1. The relative standard deviations (RSDs, n?=?5) were found 6.8 to 7.4 at S/N?=?3. All experiments were carried out at room temperature, (22?±?0.5°C).     

钼矿石物相分析及催化极谱法测定钼

为测定钼矿中钼的总量,将矿样与盐酸加热后加硝酸-硫酸(8+2)混合酸蒸发冒烟至干。用150 g.L-1氢氧化钠溶液溶解残渣取代了常用的碱融熔法,在所得上清液中测定总钼量。为溶解钼矿中不同相态,另取一份矿样先用氨水处理以溶解钼华矿(MoO3),在每次分相溶解中所得的残渣先后用40 g.L-1酒石酸溶液和150 g.L-1碳酸钠溶液处理依次溶解出钼钨钙矿[Ca(W,Mo)O4]和钼酸铅矿(PbMnO4),在溶解分去钼酸铅矿后的残渣中存在有辉钼矿(MoS2)。将其在580℃灼烧后按测定总钼的溶解方法处理,在所得溶液中测定辉钼矿的钼量。采用催化极谱法测定上述各溶液中的钼量,所用底液为含有氯酸钾、二苯羟乙酸、二苯胍及硫酸的混合液。按所提方法分析了3个钼矿标准样品,所测得每一试样中各物相中钼量之和与该样品的总钼量测定值一致,其相对标准偏差(n=5)均小于3.5%。     

Potentiometric flow-injection determination of trace hydrogen peroxide based on its induced reaction in iron(III)-iron(II) potential buffer containing bromide and molybdenum(VI)

A rapid and highly sensitive potentiometric flow-injection method for the determination of trace hydrogen peroxide was developed by use of an Fe(III)-Fe(II) potential buffer solution containing bromide and Mo(VI). The analytical method was based on a linear relationship between a concentration of hydrogen peroxide and a largely transient potential change of an oxidation-reduction potential electrode due to bromine generated by the reaction of hydrogen peroxide with the potential buffer solution. The oxidation of bromide to bromine by hydrogen peroxide occurred very rapidly with the assistance of Mo(VI) when Fe(II) existed in the potential buffer solution. It was estimated by batchwise experiments that hydroxyl radical, OH., was generated by the reaction of hydrogen peroxide with Fe(II) as an intermediate, and subsequently oxidized bromide to bromine. In a flow system, analytical sensitivities to hydrogen peroxide obtained by the detection of the transient change of potential were enhanced about 75 fold compared with those obtained by using the potential change caused by the reaction of hydrogen peroxide with the potential buffer solution without bromide and Mo(VI). Sensitivities increased with decreasing concentration of the Fe(III)-Fe(II) buffer in the reagent solution. The detection limit (S/N = 3) of 4 x 10(-7) M (13.6 ppb) was achieved by using the 1 x 10(-4) M Fe(III)-Fe(II) buffer containing 0.4 M NaBr, 1.0 M H(2)SO(4) and 0.5% (NH(4))(6)Mo(7)O(24). Analytical throughput was approximately 40 h(-1) and the RSD (n = 6) was 0.6% for measurement of 4 x 10(-6) M hydrogen peroxide. The proposed method was applied to the determination of hydrogen peroxide in real rainwater samples, and was found to provide a good recovery for H(2)O(2) added to rainwater samples.     

Non-instrumental immunochemical tests for rapid ochratoxin A detection in red wine

Gel-based and membrane-based flow-through immunoassay formats were investigated for rapid ochratoxin A (OTA) detection in red wine. The flow-through set-up consisted of an antibody containing gel or membrane placed at the bottom of a standard solid-phase extraction column (i.e. the flow-through column), combined with a clean-up column. Different clean-up methods were studied for red wine clarification and purification. The optimal method consisted of passing wine, diluted with an aqueous solution containing 1% polyethylene glycol (PEG 6000) and 5% sodium hydrogencarbonate, through strong anion exchange (SAX) silica. An immunoassay for OTA detection in red wine was optimized and a cut-off level at 2 μg L⁻¹ according to EU legislation was achieved with both formats. A more significant colour difference between blank and spiked samples was observed for the gel-based assay making this superior to the membrane-based assay. The proposed rapid gel-based test was compared with a standard immunoaffinity column - high-performance liquid chromatography - fluorescent detection (IAC-HPLC-FLD) method and a good correlation of the results was obtained for naturally contaminated wine samples.