Sensitivity atomic emission detector

Three different detection methods (gas chromatography with electron capture, mass spectrometric and atomic emission detectors) have been compared for the determination of polychlorobiphenyls in highly contaminated marine sediments [74], Only atomic emission detection in the chlorine-selective mode provided excellent polychlorobiphenyl profiles without interferences. However, the lower sensitivity of the atomic emission detector, compared to the other two detectors required a 10 to 20g sample size for most analyses. 

Atomic emission detectors (AEDs) and mass selective detectors (MSDs) are also being used to enhance selectivity and sensitivity for air analyses (Yamashita et al. 1992). 

Eluate from a chromatography column can be passed through a plasma to atomize and ionize its components and measure selected elements by atomic emission spectroscopy or mass spectrometry. An atomic emission detector directs eluate through a helium plasma in a microwave cavity. Every element of the periodic table produces characteristic emission that can be detected by a photodiode array polychromator (Figure 20-14). Sensitivity for sulfur can be 10 times better than the sensitivity of a flame photometric detector. 

F. David and P. Sandra, Comparison of the Sensitivity of the Flame Photometric Detector and the Atomic Emission Detector for the Analysis of Thiazone, Hewlett-Packard Application Note 228-136, Publication No. (43) 5091-1933E, USA, August 1991. 

Depending on target analytes to be determined, different detectors can be used, e.g., electron capture detector which offers high sensitivity and selectivity for halogenated compounds,MS which permits the analysis of a large number of compounds,and atomic emission detector which has been used for the analysis of environmental samples. Increasingly, however, P T is coupled to GC with MS detection. This technique, described and vali-... 

The use of an atomic emission detector (AED) coupled to a GC may provide under ideal conditions information about the empirical formula of the analyte corresponding to a GC peak. However, it was found that the AED responses of C, Cl and O of a series of phenols is related to the working condition of the AED. The elemental response of Cl is independent of molecular structure, but those of C and O are not, probably due to formation of CO in the plasma. The O response is also affected in nitrophenols, probably due to NO2 formation. A novel detector, based upon hyperthermal negative surface ionization, shows up to 100-fold higher sensitivity than that of the FID for alcohols and phenolic compounds. ... 

GC has high sensitivity and a good separation efficiency down to very low levels for 1,3,5-triazines. They can be determined by a thermoionization detector <88MI 6l2-02>. GC with an atomic emission detector can also be used <90JC131>. 

The gas chromatograph may be interfaced with atomic spectroscopic instruments for specific element detection. This powerful combination is useful for speci-ation of different forms of toxic elements in the environment. For example, a helium microwave induced plasma atomic emission detector (AED) has been used to detect volatile methyl and ethyl derivatives of mercury in fish, separated by GC. Also, gas chromatographs are interfaced to inductively coupled plasma-mass spectrometers (ICP-MS) in which atomic isotopic species from the plasma are introduced into a mass spectrometer (see Section 20.10 for a description of mass spectrometry), for very sensitive simultaneous detection of species of several elements. 

Detectors Various detectors can be used in combination with GC for the determination of mercury species. An ECD is a sensitive detector with an absolute detection limit of a few picograms. It does not, however, measure mercury directly, but responds to the halide ion attached to the CH3Hg ion. The identification of small methylmercury peaks can sometimes be subject to a positive systematic error owing to coeluting contaminants. The use of a plasma atomic emission detector, a mass spectromet-ric detector, CV-AAS, CV-AFS, or ICP-MS can avoid such problems, since mercury is measured directly. 

Online applications are by far the most important utilization of diode array spectrometry. High-performance liquid chromatography, supercritical fluid chromatography, capillary electrophoresis, and flow-injection techniques produce enhanced sensitivity and structure-related information due to coupling with diode-array-based detectors. Emission of the microwave-induced plasma generated in atomic emission detectors for capillary gas chromatography is also analyzed by means of UV-Vis diode array instruments. 

Sulfur compounds play a major role in determining the flavor and odor characteristics of many food substances. Often sulfur compounds are present in trace levels in foods making their isolation and quantification very difficult for chromatographers. This study compares three gas chromatographic detectors the flame photometric detector, sulfur chemiluminescence detector and the atomic emission detector, for the analysis of volatile sulfur compounds in foods. The atomic emission detector showed the most linearity in its response to sulfur the upper limit of the linear dynamic range for the atomic emission detector was 6 to 8 times greater than the other two detectors. The atomic emission detector had the greatest sensitivity to the sulfur compounds with minimum detectable levels as low as 1 pg. 

Element-specific chromatograms using an atomic emission detector (AED) have provided information on the types of additives in a variety of polymer extracts. The high resolution of capillary GC and the selectivity and sensitivity of the AED complemented mass... 

One of the latest developments in hyphenated techniques is the atomic emission detector. The availability of a bench-top model CGC -AED enables the use of this powerful technique in routine analysis. Detectabilities of this element-specific detector are of the order of 0.1 pg/s for organo-metallic compounds, 0.2 pg/s for carbon (more sensitive than FID), 1 pg/s for sulfur, and 15 pg/s for nitrogen, to mention only a few. The power of the technique lies in its supreme selectivity all elements can be detected selectively. As opposed to ECD, AED allows differentiation between var-... 

When gas chromatography is used to separate organometallic compounds, a number of detectors can be used. Conunon detectors such as Ihe FID, FPD, ECD, and MS have been employed. The most sensitive and selective detector for organometallic species is the atomic emission detector (113). The effluent from the GC enters a small chamber, and a microwave radiation is used to generate plasma. The intensity of the atomic emission radiation from the metal is monitored at a specific wavelength. Sometimes gas chromatography is interfaced with other instrumentation, such as atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICPAES), inductively coupled plasma mass spectrometry (ICPMS), to detect the metal species. 

This test method provides sample clean up and instrumental conditions necessary for the determination of Aroclors. Gas chromatography (GC) using capillary column separation technique and electron capture detector (BCD) are described. Other detectors, such as atomic emission detector (AED) and mass spectrometry (MS), may be used if sufficient performance (for example, sensitivity) is demonstrated. 

Atomic emission spectroscopy can be employed, generally with an inductively coupled plasma for thermal excitation. The sample is introduced into the plasma as a mist of ultrafine droplets, and the monochromator and detector are set to measure the intensity of an atomic emission line characteristic of the element. This technique is powerful, general, sensitive, linear, and able to measure over 70 elements, and, as a result, is widely used. Response is typically linear over four orders of magnitude in concentration with relative standard deviations of 1 to 3%. In low-salt aqueous solutions, detection limits range from 10 to 1000 nanomolar without preconcentration. Significant problems with saline samples remain, but use of Babington nebulizers alleviates these problems somewhat. 

Ultraviolet-visible (UV-Vis) spectrophotometric detectors are used to monitor chromatographic separations. However, this type of detection offers very little specificity. Element specific detectors are much more useful and important. Atomic absorption spectrometry (AAS), inductively coupled plasma-atomic emission spectroscopy (ICPAES) and inductively coupled plasma-mass spectrometry (ICP-MS) are often used in current studies. The highest sensitivity is achieved by graphite furnace-AAS and ICP-MS. The former is used off-line while the latter is coupled to the chromatographic column and is used on-line . 

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