Photometric detectors connectivity

Andreae [89] investigated two different apparatus configurations. One consisted of a reaction-trapping apparatus connected by a six-way valve to a gas chromatograph equipped with a flame ionisation detector the other apparatus combined the trapping and separation functions in one column, which was attached to a flame photometric detector. The gas chromatographic flame ionisation detector system was identical to that described by Andreae [89] for analysis of methylarsenicals, with the... 

Mallet et al. [174] used an automated gas chromatographic system which consisted of a gas chromatograph mounted with an automatic sample interfaced to an integrator. A Melpar flame photometric detector (phosphorus mode) was connected with the flame gas inlets in the reverse configuration to prevent solvent flame-out. The detector was... 

A spectrophotometric technique has been used for quantifying pg/mL levels of free and acid-labile (chemically bound) carbon disulfide in the blood of rats (Lam and DiStefano 1982, 1983). This technique is based on measuring the absorbance at 430 nm of a yellow cupric diethyldithiocarbamate complex that is formed by reacting carbon disulfide in blood with Viles reagent in the presence of acid and heat. A headspace sampler connected to GC equipped with a sulfur-specific flame photometric detector (FPD) has been developed for measuring low levels of free and acid-labile carbon disulfide in the blood of shift workers exposed to carbon disulfide (Campbell et al. 1985). A detection limit of 15.2 pg of carbon disulfide/L of blood was achieved. Concentrations of free and acid-labile carbon disulfide have also been determined by GS/MS (Brugnone et al. 1993, 1994 Perbellini et al. 1994). 

Once assembled, the cell was loaded into a custom-made furnace and connected to the process and sweep gas supply Hues. The exit gas from the cathode was routed to a Beckman IR scanner for reading CO, levels. A Hewlett/Packard gas chromatograph fitted with a thermal conductivity detector was used for reading H,S levels greater than 100 ppm and a flame photometric detector was used for HjS levels less than 100 ppm. A gold reference electrode was placed on the sur ce of the membrane away firom either process electrode and supplied with a low flow rate of a 15% CO,/ 3% 0, / balance N, mixture to maintain a stable thermodynamic reference potential by reaction (26). 

The connection to an appropriate detector flame ionization detector, thermal conductivity detector, flame photometric detector, nitrogen phosphorous detector (FID, TCD, FPD, NPD, etc.) is achieved via the four- or six-port valve being operated manually or electronically. The carrier gas (helium, nitrogen, argon, artificial air, etc.) flows via the valve only through the sampling column, at low flow rates (e.g., 25 cm /min) held constant during the experiments. 

A major advantage to this technique is that inorganics can be detected to low levels (1-2 pg) using a nondestructive detector. This means that the P1D can be connected in series with other detectors and is ideal for odor analysis. The sensitivity of the detector is directly related to the efficiency of ionization of the compound. The PID is about 5-10 times more sensitive to aliphatic hydrocarbons, 50-100 times more sensitive to ketones than FID, and 30 times more sensitive to sulfur compounds than flame photometric detection. Several reviews on the PID and its sensitivity have been published [94-97]. 

A dual beam 254 nm photometric absorbance detector with a cell volume of 6.3 yl was used for absorbance measurement. The exit port of the photometric absorbance detector cell was connected in series to a 70 y-liter flow cell in an Aminco Fluoromonitor. The Fluoromonitor s excitation light source consisted of a... 

Thermionic, flame photometric, and electron capture detectors can be connected to a LC column. The LC eluent can either be transported into the GC detector or be directly introduced. Suppressor must be incorporated. 

In spectrophotometric methods which incorporate an on-line dialysis system, the acceptor streams are almost always connected to the detector after merging with the appropriate reagents. Dialysis is used mostly to remove interferents, such as suspended or colloidal materials, which interfere physically with the photometric detection but the technique is also often used to achieve different degrees of dilutions automatically. As an early example, Basson and van Staden [14] used an on-line dialyzer to achieve deproteination and dilution of serum samples in the determination of calcium by a cresolpthalein complexone FI photometric method. Owing to the dilution effects and the exclusion of potential interferents, interferences from Schlieren effects, such as those encountered in sorption separation systems (cf. Sec. 4.6.6) were not experienced in on-line dialysis spectrophotometric systems. 

Linares et al.[49] proposed a FI system with on-line gas-diffusion for the simultaneous determination of carbon dioxide and sulphur dioxide in wines. The two gaseous constituents were separated from the acidified sample in a sandwich-type membrane gas diffusion separator, and collected in an acceptor stream. Two detectors, one potentiome-tric, responsive to both analytes, and the other photometric, responsive only to sulphur dioxide (after reaction with a p-rosaniline-formaldehyde solution) were connected in series to determine the two constituents in the acceptor. The method was applied to the determination of carbon dioxide and sulphur dioxide in different types of fruity wines and the analytical results were in good agreement with those obtained by standard methods. 

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