[Study on simultaneous determination of nitrate and sulfate in air of residential areas by ion-chromatography].

Objective: A method for determination of nitrate (NO3(-)) and sulfate (SO4(2-)) in air of residential areas by ion-chromatography (IC) was established.

Methods: The anions in aerosol samples collected with filter member were extracted by ultrasonic leaching and separated on IonPac AS11-HC analytical column and IonPac AG11-HC guard column with 20.0 mmol/L potassium hydroxide eluted at 1.

[Analysis of sugars by high performance anion-exchange chromatography with pulsed amperometric detection].

High performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) is a powerful method of recent development for the analysis of sugars. The separation of sugars by HPAEC and the detection of sugars using PAD, including stationary phase and mobile phase, and waveform of detection, are reviewed. Applications of the method are described in detail.

[Analyse of sugars in beer and wort using high performance anion-exchange chromatography coupled with pulsed amperometric detection].

The method of the simultaneous and direct analysis of eleven sugars, including monosaccharides, disaccharides and oligosaccharides, was established using high performance anion-exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD) using an Au working electrode and a pH-Ag/AgCl reference electrode. The separation was accomplished on a CarboPac PA-100 column by using gradient elution consisting of water, 0.25 mol/L NaOH and 1 mol/L NaAc as mobile phase at a flow rate of 0.

Ion chromatographic determination of some anions and alkaline cations in liquid crystal materials after ultraviolet irradiation.

A method was developed for the quantitative determination of inorganic cations and anions present in liquid crystal materials pretreated with ultraviolet irradiation by ion chromatography. The samples were irradiated at less than 20+/-2 degrees C and then pretreated with OnGuard RP and P cartridges to remove the interferential organic compounds prior to ion chromatographic analysis for both cations and anions. With a high capacity and very hydrophilic anion exchange column, four anions (fluoride, chloride, bromide, iodide) were determined in 20 min with gradient of sodium hydroxide.

Analysis of phthalates via HPLC-UV in environmental water samples after concentration by solid-phase extraction using ionic liquid mixed hemimicelles.

Ionic liquid mixed hemimicelles-based solid-phase extraction for the preconcentration of five phthalates in environmental water sample was investigated in this paper. A comparative study on the use of room temperature ionic liquids (RTILs) 1-hexyl-3-methylimidazolium bromide ([C(6)mim]Br) and 1-dodecyl-3-methylimidazolium bromide ([C(12)mim]Br)-coated silica as sorbents was presented. Owing to having bigger adsorption amounts for analytes [C(12)mim], Br-coated silica was selected as SPE material and the five analytes di-ethyl-phthalate (DEP), di-n-propyl-phthalate (DnPP), di-n-butyl-phthalate (DnBP), di-cyclohexyl-phthalate (DcHP) and di-(2-ethylhexyl)-phthalate (DEHP) can be quantitatively extracted under optimal conditions.

Cetyltrimethylammonium Bromide-coated magnetic nanoparticles for the preconcentration of phenolic compounds from environmental water samples.

The research presented in this paper investigates the adsorption of cation surfactants--cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)--onto magnetic nanoparticles and the application of this mixed hemimicelles solid-phase extraction (SPE) method for the preconcentration of several typical phenolic compounds-bisphenol A (BPA), 4-tertoctylphenol (4-OP), and 4-n-nonylphenol (4-NP)--from environmental water samples. In this novel SPE method, the charged surfactants CTAB and CPC form mixed hemimicelles on Fe3O4 nanoparticles (Fe3O4 NPs), which causes retention of analytes by strong hydrophobic and electrostatic interactions. The SPE method combines the advantages of mixed hemimicelles and magnetic nanoparticles.

Mixed hemimicelles solid-phase extraction based on cetyltrimethylammonium bromide-coated nano-magnets Fe3O4 for the determination of chlorophenols in environmental water samples coupled with liquid chromatography/spectrophotometry detection.

Mixed hemimicelles solid-phase extraction (SPE) based on cetyltrimethylammonium bromide (CTAB)-coated nano-magnets Fe3O4 was investigated for the preconcentration of four chlorophenols (CPs) in environmental water samples prior to HPLC-spectrophotometry determination in this paper. By the rapid isolating (about 5 min) of Fe3O4 nanoparticles (NPs) through placing a Nd-Fe-B strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conversional SPE method with a column can be avoided. The unique properties of Fe3O4 NPs such as high surface area and strong magnetism were utilized adequately in the SPE process.

Cetyltrimethylammonium bromide-coated titanate nanotubes for solid-phase extraction of phthalate esters from natural waters prior to high-performance liquid chromatography analysis.

As a novel nanomaterial, titanate nanotube has attracted considerable attention recently. However, most of the research work is focused on the preparation of this nanomaterial, and there is lack of information about its application in the fields of environmental monitoring and analytical chemistry. The purpose of our study is to investigate the feasibility of titanate nanotubes as an adsorbent for solid-phase extraction of several phthalate esters.

Determination of sugars and alditols in tobacco with high performance anion-exchange chromatography.

Sugars, alditols, and alcohols in tobacco products were quantified utilizing a method of high-performance anion-exchange chromatography-pulsed amperometric detection (HPAEC-PAD). The optimized analytical method can be used to classify different tobaccos and control the quality of tobaccos. To substantiate the applicability of the method, the analysis of 27 tobacco samples with satisfactory linearity, repeatability, and accuracy had been demonstrated.

Perchlorate in sewage sludge, rice, bottled water and milk collected from different areas in China.

As a new emerging environmental contaminant, perchlorate has prompted people to pay more attention. The presence of perchlorate in the human body can result in improper regulation of metabolism for adults. Furthermore, it also causes developmental and behavioral problems for infants and children because it can interfere with iodide uptake into the thyroid tissue.

Evaluation of carbon nanotubes as a solid-phase extraction adsorbent for the extraction of cephalosporins antibiotics, sulfonamides and phenolic compounds from aqueous solution.

The adsorptive potential of carbon nanotubes (single-walled carbon nanotubes and multi-walled carbon nanotubes) for solid-phase extraction of three groups of highly polar compounds (namely cephalosporins antibiotics, sulfonamides and phenolic compounds) was tested in this article. The analytes were strongly retained by the carbon nanotubes. And acceptable recoveries were obtained with the addition of ammonium acetate into eluents.

Determination of perfluorinated compounds in wastewater and river water samples by mixed hemimicelle-based solid-phase extraction before liquid chromatography-electrospray tandem mass spectrometry detection.

A comparative study on the use of cetyltrimethylammonium bromide (CTAB)-coated silica and sodium dodecyl sulphate (SDS)-coated alumina mixed hemimicelles-based solid-phase extraction (SPE) for the pre-concentration of six perfluorinated compounds (PFCs) in environmental water samples was presented. The six analytes heptafluorobutyric acid (HFBA), perfluoroheptanic acid (PFHeA), perfluorooctanic acid (PFOA), perfluorooctanic sulfonic (PFOS), perfluorononanic acid (PFNA) and perfluorodecanic acid (PFDeA) were quantitatively retained on both sorbent materials. The cationic surfactant (CTAB adsorbed onto silica) was more appropriate for SPE of PFCs.

Determination of trace levels of bromate in flour and related foods by ion chromatography.

In this paper, a method of determining trace levels of bromate in flour and related foods by ion chromatography with large volume injection has been proposed. The detection of bromate was performed with a suppressed conductivity detector after separation on an IonPac AS19 column with KOH as the gradient eluent. Parameters affecting the extraction efficiency of bromate, such as the flour-to-water ratio, extraction time, and temperature, were studied in detail.

Selenium speciation by high-performance anion-exchange chromatography-post-column UV irradiation coupled with atomic fluorescence spectrometry.

A technique for the speciation of selenomethylcysteine (SeMeCys), selenocystine (SeCys), selenite [Se(IV)] and selenomethionine (SeMet) was established in this paper using high-performance anion-exchange chromatography coupled with atomic fluorescence spectrometry (HPAEC-AFS). Analytes were separated on an AminoPac PA10 column and then digested by on-line ultraviolet (UV) irradiation, which destroyed organic compound structure. Hydride generation was used as an available sample introduction technique for atomic fluorescence detection.

Direct amino acid analysis method for speciation of selenoamino acids using high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection.

Speciation analysis of selenomethylcysteine (SeMeCys), selenomethionine (SeMet) and selenocystine (SeCys) has been performed using a direct amino acid analysis method with high-performance anion-exchange chromatography (HPAEC) coupled with integrated pulsed amperometric detection (IPAD). Three selenoamino acids could be baseline-separated from 19 amino acids using gradient elution conditions for amino acids and determined under new six-potential waveform. Detection limits for SeMeCys, SeMet and SeCys were 0.

[Application of high performance anion exchange chromatography for trace analysis of polarizable anions].

Polarizable anions such as Br-, S2O3(2-), I- and SCN- were separated using 45 mmol/L sodium hydroxide solution as the mobile phase on a high hydrophilic IonPac AS16 column. With a pulsed amperometric detector, the detection limits were 0.5, 0.

Effect of temperature on the retention of amino acids and carbohydrates in high-performance anion-exchange chromatography.

Effect of temperature on the retention of amino acids and carbohydrates in high-performance anion-exchange chromatography (HPAEC) was investigated. Amino acids retention exhibited both exothermic and endothermic behavior. Significant selectivity variations of some weakly retained amino acids were achieved through changing temperature.

Optimizing the integrated pulsed amperometric multicycle step waveform for the determination of tetracyclines.

A method of modified integrated pulsed amperometric detection with multicycle step waveform (Multi-IPAD) following high-performance liquid chromatography (HPLC) was applied for the determination of tetracyclines (TCs) including dimethyltetracycline (DMTC), oxytetracycline (OTC) and tetracycline (TC). The key advantages of the Multi-IPAD are the abilities to enhance sensitivity and reproducibility and the ability to keep working electrode clean through the use of a high-frequent waveform alteration in integration step and the use of a cleaning potential, which is quite different from conventional three-step potential waveform. The analyses were carried out using the mobile phase of acetonitrile-water mixture solution (10:90, v/v) containing 1% perchloric acid on a C(18) column at a flow rate of 0.

Comparative study on the analytical performance of three waveforms for the determination of several aminoglycoside antibiotics with high performance liquid chromatography using amperometric detection.

A preliminary comparative study was carried out on the analytical performances of a new six-potential waveform and other two detection waveforms, triple-potential waveform and quadruple-potential waveform. The analytical performances compared included signal response, background noise, signal/noise ratio and signal stability. Compared with triple-potential waveform and quadruple-potential waveform, the new six-potential waveform had higher signal response, signal/noise ratio, and sensitivity.

Determination of several sugars in serum by high-performance anion-exchange chromatography with pulsed amperometric detection.

In this paper, a sensitive, simple and direct method for simultaneous determination of glucose, ribose, isomaltose and maltose in serum sample by high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection was developed. The four target analytes were easily and completely separated on an anion-exchange column at a flow-rate of 0.25 mL/min by binary step gradient elution in about 16 min and the two eluents were deionized water and 500 mM sodium hydroxide, respectively.

Comparisons of disposable and conventional silver working electrode for the determination of iodide using high-performance anion-exchange chromatography with pulsed amperometric detection.

The paper compared the performance of two kinds of silver working electrode in electrochemical detector-the disposable and conventional electrode for the determination of iodide using high-performance anion-exchange chromatography (HPAEC) hyphenated with pulsed amperometric detection (PAD). The comparisons were carried out on the time of equilibration, long and short-term reproducibility, limits of detection and linearity of calibration. Results showed that disposable working electrode manifested equal or better results than conventional working electrode and could be used for iodide analysis.

Multi-walled carbon nanotubes as a solid-phase extraction adsorbent for the determination of chlorophenols in environmental water samples.

Multi-walled carbon nanotubes (MWCNs) are used as adsorbent for solid-phase extraction (SPE) of several chlorophenols (CPs). CPs were adsorbed on MWCNs cartridge, then desorbed with pH 10.0 methanol, finally determined by HPLC.

[Determination of anions, cations and organic acids in the oil field water by ion chromatography].

A method for the determination of anions, cations and organic acids in the oil field water with high chloride and sodium ions was developed by ion chromatography (IC) with a conductivity detector. The separation of the cations was achieved on an IonPac CS12A column with H2SO4 as the eluent. The separation of the anions and organic acids was achieved on an IonPac AS11-HC column with KOH as the eluent, and the detection was performed by a conductivity detection mode.