Flame photometric detector operation

The Oxamyl in this extract is then determined by gas chromatography using on-column reaction with trimethylphenyl ammonium hydroxide, the derivative so formed being determined by a flame photometric detector operated in the sulphur mode. Both Oxamyl and Oxamyl oxime in the soil react with trimethylphenyl ammonium hydroxide to form the same methoxime derivative (CH3)2NCOC(SCH3) -NOCH3. 

Analytical Procedures. The extracts from exposure pads, hand rinses, and apple leaves were evaporated to dryness in the 40-45°C water bath, and the carbaryl residues were determined by the procedure of Maitlen and McDonough (4). In this procedure, the residues were hydrolyzed with methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate derivative by reaction with methanesulfonyl chloride. The carbaryl mesylate was quantitated with a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped with a flame photometric detector operated in the sulfur mode. The GLC column was a 122 cm x 4.0 mm I.D. glass column packed with Chromosorb G (HP) coated with 5% OV 101. The column was operated at a temperature of 205°C with a nitrogen flow rate of 60 ml/min. 

In the case of crop residues, GC determination is carried out on the hydrolyzed product, i.e., methomyl oxime, instead of alanycarb to make effective use of its substantially higher response to the flame photometric detector. In order to prevent vaporization loss of methomyl oxime, ethylene glycol must be added prior to concentration in Section 6.3. In all other concentration operations, full account must also be taken of the high volatility of both alanycarb and methomyl oxime, especially in the process of removal of the last traces of solvents. Alanycarb residue in the sample is stable under storage condition at -20 °C for at least 100 days. 

Instrument and column conditions. A Tracor 222 gas chromatograph equipped with a flame photometric detector (FPD) operating in the phosphorus mode (526 mu) filter was used. The operating conditions of the flame photometric gas chromatographic analyses were as follows ... 

Furthermore, GC samples were separated on a Carlo Erba type 4200 gas chromatograph fitted with a normal FID and with a flame photometric detector (FPD) operating in the sulfur-mode at 394 nm. Again, the dead-volume free "glass-cap-cross" was used in order to split the carrier gas flow. By means of these sulfur chromatograms mass spectral evaluation could be focussed on certain compounds in very complex mixtures. 

A more expensive alternative is to use standard AutoAnalyser type systems, based on multichannel peristaltic pumps, to pump samples and reagents and/or diluents at the desired rates to give automatic mixing at the desired ratio. Flame photometric detectors have been used for many years with AutoAnalysers, especially in clinical laboratories. Curiously, in the past, this approach has less often been routinely used in environmental analytical laboratories employing flame spectrometry, perhaps because an attractive feature of flame spectrometry is the speed of response when used conventionally. Over the past few years, however, there has been an increasing tendency towards fully automated, unattended operation of flame spectrometers. This undoubtedly reflects, at least in part, the improvements in safety features in modern instruments, which often incorporate a comprehensive selection of fail-safe devices. It also reflects the impact of microprocessor control systems, which have greatly facilitated automation of periodic recalibration. 

In the early 1990s Amirav et al. introduced a new strategy for the operation of FPD based on a pulsed flame instead of a continuous flame for the generation of flame chemiluminescence. This pulsed flame photometric detector (PFPD) is characterized by the additional dimension of a light emission time and the ability to separate in time the emission of sulfur species from those of carbon and phosphorus, resulting in considerable enhancement of detection selectivity. In addition, detection sensitivity is markedly improved, thanks to ... 

FIGURE 10.8 Combustor and wall gas pathways in PFPD. (From Operator s Manual Model 5380 Pulsed Flame Photometric Detector, OI Analytical, Texas, 1997.)... 

Sarin in water may be analyzed by gas chromatography after extraction with chloroform. Using an internal standard linearity was determined to faU in the range 10-1000 ppb with flame photometric detector (Shih and Ellin 1986). Flame photometric or a nitrogen-phosphorus detector should be operated in the phosphorus-specific mode. A fused-silica capillary GC column should be effi-cienf in separation. Sarin may be analyzed by GC/MS. The primary mass ion is 99. Ofher characteristic mass ions are 125, 81,43, and 79. 

A Tracor MT-220 gas chromatograph was used with operating temperatures of Inlet - 230 C, detector - 180 C, and oven -198°C. Injections (5 Pi) were made onto a lOZ carbowax 20 M 20% KOH column and swept through by nitrogen at a rate of 68 ml/mln. The flame photometric detector was operated In the sulfur mode and flow rates of gasses used were 100 ml/mln for hydrogen, 100 ml/mln for air, and 10 ml/mln for oxygen. 

Of the many available detectors, the most common (Table 3) are thermal conductivity detector (TCD), flame ionization detector (FID), electron-capture detector (ECD), alkali-flame ionization detector (AFID or NPD), flame photometric detector (FPD), and mass selective detector. The TCD and FID are usually considered universal detectors as they respond to most analytes whereas the ECD, AFID, and FPD are the most useful selective detectors and give differential responses to analytes containing different functional groups. Note that this does not imply that the magnitude of the response of the universal detectors is constant to all analytes. The mass selective detector has the advantage of operation in either universal or selective detection mode whilst an infrared detector is a powerful tool for distinguishing isomers. 

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 semiportable or stationary thermal desorption/gas chromatographic type of instrument with flame photometric detector, this device is operable in field environments. It is designed for the detection of a long list of TICs and nerve and blister agents down to or below AEL levels through the use of different modules equipped with various signal detectors. 

---