The Electrolytic Conductivity Detector ELCD

Heteroatom selective [for organic compounds with halogen (X) substituents, or N or S atom] destructive mass-flow detector requires liquid reagents good sensitivity and linearity response is directly proportional to flow rate of the X, N, or S atoms. 

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In the electrolytical conductivity detector (ELCD) the eluate from the GC column passes into a Ni reactor in which all substances are completely oxidized or reduced at an elevated temperature (about 1000 C). 

The analytes separated on GC column are determined by a halogen-specific detector, such as an electrolytic conductivity detector (ELCD) or a microcoulo-metric detector. An ECD, FID, quadrupole mass selective detector, or ion trap detector (ITD) may also be used. A photoionization detector (PID) may also be used to determine unsaturated halogenated hydrocarbons such as chlorobenzene or trichloroethylene. Among the detectors, ELCD, PID, and ECD give a lower level of detection than FID or MS. The detector operating conditions for ELCD are listed below ... 

The electrolytic conductivity detector is a good alternative to the FPD for selective sulfur detection. The ELCD has a larger linear dynamic range and a linear response to concentration profile. The ELCD in most cases appears, under ideal conditions, to yield slightly lower detection limits for sulfur (about 1-2 pg S/sec), but with much less interference from hydrocar-... 

Element selective detectors Element selective detectors applicable in pesticide residue analysis include electron capture detector (ECD), electrolytic conductivity detector (ELCD), halogen-specific detector (XSD), nitrogen phosphorus detector (NPD), flame photometric detector (FPD), pulsed flame photometric detector (PEPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED). To cover a wider range of pesticide residues, a halogen-selective detector (ECD, ELCD, XSD) in conjvmction with a phosphorus- (NPD, FPD), nitrogen- (NPD), and/or sulfur-selective detector (FPD, SCD) is commonly used. A practical approach is to spht the column flow to two detectors that reduces the number of injections however, the reduced amoimt of analyte that reaches the detector must be considered. 

There are a number of other GC detectors commercially available. Photoionization detectors (PIDs) are primarily used for the selective, low-level detection of the compounds which have double or triple bonds or an aromatic moiety in their structures. Electrolytic conductivity detectors (ELCDs) are used for the selective detection of chlorine-, nitrogen-, or sulfur-containing compounds at low levels. Chemiluminescence detectors are usually employed for the detection of sulfur compounds. The atomic emission detectors (AEDs) can be set up to respond only to selected atoms, or group of atoms, and they are very useful for element-specific detection and element-speciation work. 

Selective GC detectors aid in the detection and identification of compounds containing specific elements halogens with electron capture detector (BCD) or electrolytic conductivity detector (ELCD) nitrogen and phosjAorus with nitrogen-phosphorus detector (NPD) sulfur and phosphorus with flame photometric detector (FPD) and sulfur with sulfur chemiluminescence detector (SCD). The development of the atomic... 

Two of the more recently developed detectors, namely, the Hall electrolytic conductivity detector (ELCD) and the photoionization detector (PID) are recommended by the EPA for the analysis of volatile and semivolatile halogenated organic compounds and low molar mass aromatics. Chemical emission based detectors, such as the thermal energy analyzer (TEA) for its determination of... 

Several detectors are used for VOCs analysis by GC flame ionization detector (FID), photo ionization detector (PID), electron capture detector (BCD), electrolytic conductivity detector (ELCD), mass spectrometer detector (MSD or MS), and Fourier-transform infrared detector (FTIRD). For the in-depth reviews of the detectors, readers are directed to Refs. [52-54]. Examples of ICP-MS or microwave-induced plasma atomic emission spectrometry (atomic emission detector, AED) have been reported as detection technique after chromatographic separation [55,56]. Current trends and developments in GC analysis of VOCs have been recently reviewed by the group of Dewulf [16,57]. Mass spectrometer detectors allow low detection limits in single/selected ion monitoring (SIM) and a qualitative confirmation by full scan mode or by means of other ion selected as qualifier. 

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 ... 

Detection systems Halogen-containing herbicides are detected at the picogram level with the BCD ( Ni). Low limits are also obtained in some cases with selective nitrogen-phosphorus detector (NPD) or electrolytic conductivity (Hall) detector (ELCD) detection (Ing). Mass spectrometric detection is widely used due to its universal character as well as for its intrinsic sensitivity and selectivity. Both FI and Cl (using methane or isobutane as reagent gases) are used for ionization. Specific ions monitored in the... 

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