Ambient monitoring detector

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

Multi-band fire detector monitors monitor several wavelengths of predominate fire radiation frequencies by photocells. They compare these measurements to normal ambient frequencies through micro processing. Where these are found be above certain levels an alarm is indicated. False alarms may even be "recognized"... 

The synthesis of a new near-infrared cyanine dye was monitored by CE and fluorescence detection. The chemicals structure of the dye and its synthetic precursor are depicted in Fig. 3.165. The analysis of the dye was realized in fused-silica capillaries of 75 and 100 /an i.d. The total and effective lengths of capillaries were 75 and 60 cm, respectively. The separation voltage was 30 kV and separations were carried out at ambient temperature. The running buffer was 2.5 mM Na2B407 (pH = 9.2). A near-infrared laser-induced fluorescence detector was applied. Electropherograms illustrating the separation of the dye are shown in Fig. 3.166. 

The reaction between olefins and ozone produces light that can be measured and related to the concentration of the reactants. One of the preferred methods for measuring ambient ozone concentrations utilizes the chemiluminescence generated in the ozone-ethylene reaction for detection. Recently, Hills and Zimmerman (16) described the use of this detection principle for determining hydrocarbon concentrations. They utilized the chemiluminescence created when ozone reacts with isoprene for development of a continuous, fast-response isoprene analyzer. This real-time isoprene system is reported to be linear over three orders of magnitude and to have a detection limit of about 1 ppbv. Because the system doesn t include a preseparation of hydrocarbons, interferences from other olefins (ethylene, propylene, and so forth) could occur. Thus far the chemiluminescent detector has been used to monitor isoprene emissions under conditions in which the concentrations of olefins that could interfere are negligible compared to those of the biogenic hydrocarbon. 

Imazalil, OPP, and TBZ residues were determined using an HPLC system, consisting of a ternary HPLC pump attached to 250 X 4.6-mm-ID Hichrom RPB 5-/tm column with a 10 X 3.2-mm-ID guard cartridge column. The packing material of both columns was base-deactivated silica, fully endcapped with a bonded phase of Cg/C]8. The mobile phase was methanol/water at a flow rate of 1 ml/min at ambient temperature. Imazalil in the eluate was detected with UV detector at 204 nm a fluorescence detector was used to monitor OPP (excitation 285 nm, emission 350 nm) and TBZ (excitation 296 nm, emission 350 nm) (47). 

Continuous air monitoring for trace contaminants in ambient air has developed extensively since the mid-1960s as a result of stimulation from new air pollution measurement requirements. Workers expect that similar needs will develop as certain chemical constituents of particulate material are identified as factors in human health effects. Techniques for the continuous chemical characterization of particulate matter are slow in coming because the amounts of material sampled are small, often below the detection limits of instrumentation. In all cases so far, either a precollection method like filtration or a special detector of high sensitivity has been required. 

In-line detection. In the treatment of solutions containing americium the americium 241 content of solutions leaving the chromatography columns is continuously monitored. The gamma detector is a miniature Geiger-Muller tube placed in contact with the solution outlet pipe. The unit is shielded from ambient irradiation by lead. 

Protein digests were analyzed by reversed-phase on a 1090A/M Hewlett Packard HPLC equipped with a diode-array detector and Chemstation. They were analyzed (100-200 for PVDF and 20-30 p.L total volume for in-gel digests) on a SynChrom C4 (2.1 x 50 mm) column (3) at a flow rate of 0.146 mL/minute at ambient temperature, and monitored at 215 and 280 nm. When used, the anion exchange column was placed in series before the C4 column and removed approximately 7 minutes into the isocratic portion of the gradient. Buffer A was aqueous 0.1% TFA. Buffer B was 0.1% aqueous TFA in 90% acetonitrile. The gradient used was 3%B (0.01-10 minutes), 3-18%B (10-26 minutes), 18-55%B (26-86 minutes), 55-80%B (86-100 minutes). Peptides were collected manually for further analysis. 

Like the UV detector, the IR detector is relatively insensitive to fluctuations around a set temperature and therefore particularly suitable for SEC at temperatures far above ambient conditions. One of the main uses for this type of detector is in the detection of polyolefins which can only be chromatographed at temperatures in excess of 135°C. Infrared detection is also useful in measuring polymer stoichiometry as a function of molecular weight/mass. Here the detector is used to monitor specific functional groups in a copolymer. 

Clearly, the preferred method to use for the analysis of phosgene depends upon the particular application to hand. For routine use in the laboratory, for monitoring the ambient air, impregnated paper strips and Dra ger tubes can be recommended as both reliable and easy to use. On the plant, automatic methods for continuous analysis would be appropriate, and one of the electrical or automated spectroscopic techniques would be suitable. For accurate measurement of very low (p.p.b.) concentrations however, a gas chromatographic procedure using one of the special detectors is most suitable. 

Pranitis DM, Meyerhoff ME. 1987. Continuous monitoring of ambient ammonia with a membrane-electrode-based detector. Anal Chem 59 2345-2350. 

AMETEK s ProMaxion process mass spectrometer can monitor up to 32 components. Automated sample switching at the multiport allows unattended analysis of process and calibration gases. Different calibration and analysis methods can be assigned to each sample port. A membrane inlet system is incorporated for ambient gas sampling. The available mass range is 1-200 amu. The detection range is 10 ppm to 100 % with a Faraday cup detector lower LODs are possible with an electron multiplier. 

Comparison studies between luminol detection and BCD for PAN analysis have shown that either method can yield accurate, reliable, sensitive measurements of ambient PAN concentrations, with typical sensitivities on the order of 10 ppt. The advantages of the luminol detector over GC/ECD lie in the faster analysis times achievable. This makes luminol an attractive alternative for aircraft measurements, where time resolution translates into spatial resolution. The luminol detector also enables the simultaneous measurement of PANs and NO2 to monitor decomposition and formation processes in the atmosphere." " ... 

An example of an automatic analyser for the determination of organic pollutants is the Meloy HC 500-2C from Columbia Scientific Industries. It is a self-contained system for monitoring ambient concentrations of non-methane hydrocarbons (NMHC), methane and total hydrocarbons. Sample air Is first introduced directly into the flame ionization detector to yield a total hydrocarbon reading which Is stored In an electrical circuit. The pneumatic system Is automatically switched so that the sample air passes through a catalytic converter before It Is Introduced Into the detector, which converts ail the NMHC Into a non-detectable species. Hence, only the methane in the sample Is... 

Typical monitor data, such as response time, accuracy, or sensitivity, do not depend only on sensor characteristics. For example, the overall response time is composed of the sensor response time, of delays due to ambient influences such as water, of sample flow in the case of sidestream sensors, or of gas exchange time of the cell or detector volume. 

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