Hypercoulometric effect in an electron capture detector polarized with an additional voltage

Summary This paper reports measurements of the current characteristics and of the signal corresponding to a constant concentration of Freon F-11 for an electron-capture detector, supplied with a pulse voltage with a changeable pulse duration, amplitude and repetition time. It was found that an additional voltage applied to the detector cathode increased the detector signal by about 50% and that the maximal signal was observed at 5 V. The influence of the polarized voltage on the electron caputure efficiency coefficient (p) measured with two detectors in series was demonstrated and the reliability of the sample mass calculation by means of (p) is discussed.     

Voltammetric Detector for Liquid Chromatography: Determination of Triclosan in Rabbit Urine and Serum

A flow-electrolytic cell containing a strand of carbon fibers has been designed and characterized for use in a voltammetric detector for high-performance liquid chromatography. The detector was used for determination of triclosan (2,4,4-trichloro-2-hydroxydiphenyl ether) in rabbit serum and urine. Analysis of rabbit serum and urine 1 day and 1 to 5 days, respectively, after ingestion of oral triclosan revealed that the concentration of triclosan was higher than for control serum and urine. The concentration reached maximum levels after 6 h and 34 h or 44 h in serum and urine, respectively. When triclosan was determined in rabbit samples with the method proposed the results obtained were comparable with those obtained by high-performance liquid chromatography with ultraviolet detection.     

Highly sensitive determination of haloperidol in human serum by capillary gas chromatography using a surface ionization detector

A method has been developed for highly sensitive determination of haloperidol in human serum involving a simple extraction procedure followed by gas chromatographic separation. Target components were separated from the extracting solvents with a Van den Berg type solventless sample injector before introduction Into a DB-1 capillary separation column. A surface ionization detector (SID), which has highly selective sensitivity for Substituted amines, was employed for quantitation using bromperidol as an internal standard. Chloroform proved to be the best extracting solvent, yielding a quantitative detection limit of 5 ng/ml (S/N = 2). Comparison of the response to target compounds obtained by the SID, FTD (flame thermionic detector), and FID (flame ionization detector) showed the SID to be superior.     

Luminol chemiluminescence HPLC reaction detector for amino acids and other ligands

A detector for HPLC is based on suppression of chemiluminescence from the Cu(II)-luminol-peroxide reaction. Analytes which complex Cu(II) reduce the free Cu(II) concentration and thus the observed chemiluminescence intensity. The degree of chemiluminescence suppression is a measure of the analyte concentrations. Detection limits are in the range of 1 pmole-1 nmole for amino acids (both primary and secondary without derivatization), CN^–, amines, catecholamines, catechol, and aminoglycoside antibiotics. The detection approach is demonstrated with an ion-exchange separation of amino acids, a reverse phase separation of catecholamines, and an ion-pair separation of the three components of gentamicin C in commercial gentamicin sulfate.     

Fused silica capillary tube isotachophoresis using a multichannel photodiode array detector

Isotachophoresis carried out in a 0.25 mm i.d. fused-silica capillary tube yielded high resolution, compared with that in a fluorinated ethylene-propylene polymer tube. The use of an ultraviolet-visible multichannel spectrophotometer with photodiode array as detector together with a cross flow cell (volume 0.01 μl) was investigated. The system was successfully applied to the analysis of cationic dyes such as neutral red, bismarck brown, and basic fuchsine.     

Electrochemical detector with a 20 nl volume for micro-columns liquid chromatography

Summary A flow-through two electrode wall-jet cell with a platinum measuring electrode and a cell volume of 20 nl has been designed and evaluated. It has been used to detect phenols by reversed phase liquid chromatography using short micro bore columns. The linear dynamic range between the measured current and the concentration is greater than 10³ (1.5×10^–7–5×10^–4 mol/l) and the minimum analyzable amount was found to be 10 pg for pyrocatechol. A negligible broadening in the detector permits the use of micro columns down to 0.5 mm internal diameter, packed with 5 m particles, without any substantial distortion of eluted zones.Presented at the 14th International Symposium on Chromatography London, September, 1982     

微流控芯片化学发光检测系统研究

在微流控芯片上实现了鲁米诺-过氧化氢-Co2+化学发光反应及分析应用研究。探讨了分离电压对电泳图谱的影响,发现在选定实验条件下,Co2+检出限可达到2.0×10-6mol/L;并且在微流控芯片上实现了Co2+与Cu2+的快速分离及检测。     

Miniaturization of separation techniques using planar chip technology

Miniaturization of separation columns implies equally reduced vol- umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron-sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser-induced fluorescence detection at any capillary length of choice between 5 and 50 mm.     

A novel thin-layer amperometric detector based on chemically modified ring-disc electrode and its application for simultaneous measurements of nitric oxide and nitrite in rat brain combined with in vivo microdialysis

A novel thin-layer amperometric detector (TLAD) based on chemically modified ring-disc electrode and its application for simultaneous measurements of nitric oxide (NO) and nitrite (NO₂⁻) in rat brain were demonstrated in this work. The ring-disc electrode was simultaneously sensitive to nitric oxide (NO) and nitrite (NO₂⁻) by modifying its inner disc with electropolymerized film of cobalt(II) tetraaminophthalocyanine (polyCoTAPc)/Nafion and its outer ring with poly(vinylpyridine) (PVP), respectively. The ring-disc electrode was used to constitute a novel TLAD in radial flow cell for simultaneous measurements of NO and NO₂⁻ in rat brain combined with techniques of high performance liquid chromatography (HPLC) and in vivo microdialysis. It was found that the basal concentration of NO in the caudate nucleus of rat brain is lower than 1.0×10⁻⁷ mol l⁻¹, NO₂⁻ concentration is 5.0×10⁻⁷ mol l⁻¹ and NO exists in brain maybe mainly in the form of its decomposed product.     

Electron capture detector response to low electron affinity aromatic hydrocarbons using positive ion stabilization and alkyl chloride sensitization

The electron capture detector (ECD) response to numerous aromatic hydrocarbons of low electron affinity (EA) is shown to be detrimentally affected by two processes which compete with and typically overwhelm the electron capture reactions of these molecules. It is shown that the effects of these two undesired reactions can be eliminated by the permanent addition of trimethylamine and one of several alkyl monochlorides to the detector make-up gas. These modifications of the detector gas result in greatly increased sensitivity, increased linearity, and increased reproducibility of response. A kinetic model for the ECD responses of low EA resonance capture molecules is developed which appears to explain these improvements.