Nitrite in environmental water samples is reduced at room temperature to nitric oxide in acidic medium containing vanadium (III). Nitrate is also rapidly reduced after heating to 80-90 degrees C. Nitric oxide is removed from the reaction solution by scrubbing with helium carrier gas and is detected by means of a chemiluminescence NOx analyzer. Nanogram detection limits are obtained. The method has the advantage of not requiring highly acidic solutions for nitrate reduction and has been applied to the analysis of a variety of environmental waters, sediment, plant materials, and human urine and blood serum.
Environmental samples were analyzed for arsenate and arsenite ions and the methylarsenic acids in nanogram amounts. Dimethylarsinic acid and methylarsonic acid were found in natural waters, bird eggshells, seashells, and human urine.
Analytical methods have been developed for the determination of trace amounts of inorganic tin and methyltin compounds. Tin compounds in aqueous solution at pH 6.5 are converted to the corresponding volatile hydride, SnH4, CH3SnH3, (CH3)2SnH2, and (CH3)3SnH, by reaction with sodium borohydride. These are scrubbed from solution, cryogenically trapped on a U-tube, and separated upon warming. Detection limits are approximately 0.01 ng as Sn when using a hydrogen-rich, hydrogen-air flame emission type detector (SnH band). Parts-per-trillion concentrations of methyltin compounds were found in a variety of natural waters and in human urine.
Tungstic acid surfaces chemisorb NH, and HNOa. Coilectlon of these gases is posslbie by sampling with a hollow tube, the interior of which is coated wlth tungstic acid. Under conditions of laminar flow, the gases diffuse to the wail and are chemisorbed while particles are carried through the tube. Particles are collected with an in-line tube packed with tungstic acid coated sand. Thermal desorption followed by a simple separation and detection by a chemiluminescent NO, analyzer permits analyses at the parts per bllllon and lower concentration range for gaseous and particulate forms of the analytes. Detection limits are 1-3 nglsampie. The precision of analyses of ambient air samples is in the 5-10% relative standard deviation range. Coated hollow tubes conform sufficiently to the mathematical model of tube gas dynamics so as to permit reasonable determination of gaseous diffusion coefficients at ambient concentrations.Ammonia, nitric acid, and sulfuric acid aerosol are important factors influencing the acidity of air and acidity of rain. Ammonium nitrate and ammonium sulfate are solid compounds resulting from atmospheric acid-base reactions of the three acid rain components. Thus, both gaseous and particulate forms of ammonia and nitric acid are expected to be present in air.The determination of gaseous ammonia and nitric acid at the trace concentrations (0.1-5.0 pg/m3) present in comparatively nonpolluted, ambient air as well as discrimination of gaseous from particulate forms is a difficult task. A number of workers have noted particle to gas or gas to particle conversion reactions on filters used to separate particles from the gas phase. A discussion of this aspect of previous work is given in our companion article (I).Analytical procedures for gaseous ammonia have involved absorption on an oxalic acid treated surface as in the ring oven technique of Shendrikar and Lodge (2) modified by Cattell and DuCross (3). Gillett and Ayers (4) report the detection limit of this method to be near 0.05 pg/sample in routine use. Ferm (5) has used an oxalic acid coated diffusion tube to collect NH3 later determined by ion-selective electrode. McClenny and Bennett (6) have reported a method for gaseous ammonia based upon absorption on Teflon beads after filtration to remove particulate ammonia. Collected gaseous ammonia was desorbed by heating and detected by using a photoacoustic detector. The detection limit was approximately 5 ng/sample.Gaseous nitric acid has been collected on sodium chloride impregnated filters after removal of particles by a nontreated prefilter (7,8). Total gaseous and particulate nitrates can be collected on filter combinations such as, for example, a quartz fiber filter and a nylon filter (9). Shaw et al. (IO) developed a method for nitric acid in air employing two parallel sampling lines, one of which includes a diffusion denuder tube to eliminate "OB.Both total and particulate HN03 are determined and the difference is gaseousThe work reported here started with a preliminary study of new approaches t...
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