Electrolytic conductivity detectors

COLUMN 0.2% CARBOWAX 1500 ON CAR80PACK-C PROGRAM 60°C-3 MINUTES 8 /MINUTE TO DETECTOR ELECTROLYTIC CONDUCTIVITY %... 

Volatile aromatic and chlorinated compounds are usually analyzed with the photoionization detector/electrolytic conductivity detector (PID/ELCD) combination in EPA Method 8021. In this method, the PID detects aromatic compounds, typically the volatile constituents of petroleum fuels (BTEX) and oxygenated additives, and the ELCD detects chlorinated solvents. Both detectors are considered to be selective for the target analytes of EPA Method 8021. But are they sufficiently selective for making unambiguous decisions on the presence and the concentrations of these analytes ... 

Analysis of environmental samples is similar to that of biological samples. The most common methods of analyses are GC coupled to MS, ECD, a Hall s electrolytic conductivity detector (HECD), or a flame-ionization detector (FID). Preconcentration of samples is usually done by sorption on a solid sorbent for air and by the purge-and-trap method for liquid and solid matrices. Alternatively, headspace above liquid and... 

ECD = electron capture detector FID = flame ionization detection GC = gas chromatography HECD = Hall electrolytic conductivity detector HRGC = high-resolution gas chromatography HSD = halogen-specific detector H2SO4 = sulfuric acid MS = mass spectrometry NR = not reported PID = photoionization detection UV = ultraviolet detection... 

Gas chromatograph [Flewlett-Packard (FIP) 5890 or 6890 GC with HP 7673 or 6890 Series injector and OI Analytical Model 5220 electrolytic conductivity detector or 5360 halogen-specific detector HP 5890 or 6890 equipped with HP 7673 or 6890 Series injector and HP 5970 or 5972 mass-selective detector]... 

Analytical 5220 electrolytic conductivity detector, halogen mode... 

The most widely used element-selective electrochemical detector is the Hall electrolytic conductivity detector (HECD) [98,116,206]. This is an improved version of an earlier design by Coulson [207,208]. In both detectors the reaction products are swept from the furnace into a gas-liquid contactor trtiere they are mixed with an appropriate solvent. The liquid phase is separated from insoluble gases in a gas-liquid separator and then passed through a conductivity cell. The Coulson detector employed a... 

Figure 3.16 Schenatic diagran of a Hall electrolytic conductivity detector with an expanded view of the bipolar pulsed differential conductivity cell.

ELCD, HECD Electrolytic conductivity (Hall) detector Thermal generation of inorganic ions... 

The Bellar et al. [219] purge and trap method has been applied to the determination of vinyl chloride in seawater. Using the Hall electrolytic conductivity detector, no response was obtained for the acetone used to prepare the vinyl chloride standard solution. 

Most detectors are of the differential type, that is their response is proportional to the concentration or mass flow rate of the eluted component. They depend on changes in some physical property of the gas stream, e.g. thermal conductivity, density, flame ionization, electrolytic conductivity, P-ray ionization, in the presence of a sample component. The signal from the detector is fed to a chart recorder, computing integrator or... 

VDU screen via suitable electronic amplifying circuitry where the data are presented in the form of an elution profile. Although there are a dozen or more types of detector available for gas chromatography, only those based on thermal conductivity, flame ionization, electron-capture and perhaps flame emission and electrolytic conductivity are widely used. The interfacing of gas chromatographs with infrared and mass spectrometers, so-called hyphenated techniques, is described on p. 114 etseq. Some detector characteristics are summarized in Table 4.11. 

AOAC = Assocition of Official Analytical Chemists ASTM = American Society for Testing and Materials Cl = chemical ionization ECD = electron capture detection ELCD = electrolytic conductivity detector EPA = Environmental Protection Agency GC = gas chromatography GPC = gel permeation chromatography ... 

ECD = electron capture detection ELCD = electrolytic conductivity detector EPA = Environmental Protection Agency GC = gas... 

The best sensitivity for 1,2-dibromoethane quantification is obtained by either electron capture detector (ECD) or Hall electrolytic conductivity detector (HECD) in the halide detection mode, since these detectors are relatively insensitive to nonhalogenated species and very sensitive to halogenated species. Another common detection device is a mass spectrometer (MS) connected to a GC. The GC/MS combination provides unequivocal identification of 1,2-dibromoethane in samples containing multiple components having similar GC elution characteristics (see Table 6-2). To date, GC equipped with either ECD or HECD has provided the greatest sensitivity for detecting... 

ECO = electron capture detector ED = electrochemical detector FID st flame ionization detector GC = gas chromatography HECD = Hall s electrolytic conductivity detector HPLC = high performance liquid chromatography MEC = molecular emission cavity analysis MS - mass spectrometry HD = photo-ionization detector... 

Eopez-Avila V, Heath N, Hu A. 1987. Determination of purgeable halocarbons and aromatics by photoionization and Hall electrolytic conductivity detectors connected in series. J Chromatog Sci 25 356-363. 

B Aromatic and Halogenated Volatiles by GC using Photoionization and/or Electrolytic Conductivity Detectors 8031 Acrylonitrile by GC... 

Table I contains a list of some of the compounds that have been submitted to this type of analysis. The recovery data is intended to be illustrative only since recoveries depend strongly on several important method variables. Recoveries are expressed as a percentage of the amount added to organic free water. The purge time was 11-15 minutes with helium or nitrogen, the purge rate was 20 ml/minute at ambient temperature, and the trap was Tenax followed by Silica Gel. Data from the 5 ml sample was obtained with a custom made purging device and either flame ionization, microcoulo-metric, or electrolytic conductivity GC detectors. Data from the 25 ml sample was obtained with a Tekmar commercial liquid sample concentrator and a mass spectrometer GC detector using CRMS.

The halogen selective microcoulometric and electrolytic conductivity detectors have been applied extensively to the analysis of halogenated compounds in drinking water. Both have adequate sensitivity for the application and sufficient selectivity to allow reasonably accurate identifications with the retention time data. However, these detectors are also best applied to well defined samples where the probability of unexpected compounds is low. 

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