Water cooling detection

A hanging mercury drop electrodeposition technique has been used [297] for a carbon filament flameless atomic absorption spectrometric method for the determination of copper in seawater. In this method, copper is transferred to the mercury drop in a simple three-electrode cell (including a counterelectrode) by electrolysis for 30 min at -0.35 V versus the SCE. After electrolysis, the drop is rinsed and transferred directly to a prepositioned water-cooled carbon-filament atomiser, and the mercury is volatilised by heating the filament to 425 °C. Copper is then atomised and determined by atomic absorption. The detection limit is 0.2 pg copper per litre simulated seawater. 

Pour 2 ml of concentrated nitric acid into each of five test tubes. Secure the first test tube vertically in a clamp of a stand and, while heating the acid, lower a glowing piece of charcoal into it. What happens Drop a piece of sulphur into the second tube secured in a clamp of the stand and heat the tube. When the tube cools, pour out its contents into water and detect the presence of sulphuric acid. Write the equations of the reactions. Heat the third tube with nitric acid and introduce a piece of wool into it. Comment on your observations. 

The basic set-up and compounds of an ICP-AES and ICP-MS are shown in Fig. 2. The ICP part is almost identical for AES and MS as detection principle. The ICP torch consists of three concentric quartz tubes, from which the outer channel is flushed with the plasma argon at a typical flow rate of 14 1 min-1. This gas flow is both the plasma and the cool gas. The middle channel transports the auxiliary argon gas flow, which is used for the shape and the axial position of the plasma. The inner channel encloses the nebulizer gas stream coming form the nebulizer / spray chamber combination. This gas stream transports the analytes into the plasma. Both the auxiliary and the nebulizer gas flow are typically around 1 1 min-1. The plasma energy is coupled inductively into the argon gas flow via two or three loops of a water-cooled copper coil. A radio frequency of 27.12 or 40.68 MHz at 1-1.5 kW is used as power source. The plasma is... 

A solution of 10 g of the (S.y-unsauiratcd bicyclic ketone 55 (cf. Sch. 30) in lOOOmL of acetone was purged with argon and irradiated in a water-cooled quartz vessel placed in a Rayonet RPR-208 photochemical reactor equipped with RUL-3000 lamps (/. 300 nm). Irradiation was continued for 72 h and the reaction was monitored by tic. After 72 h of irradiation, the conversion was 98% and the only detectable compound was the ODPM rearrangement product, tricyclo[3.3.0.0.0]octane-3-one 57. The solvent was distilled off and the residue was chromatographed over silica gel using a benzene/ ether solvent mixture. The product which was eluted (8.6 g) was further distilled under vacuum (50 °C/1 mm) to get the pure ODPM rearrangement product (tricyclic ketone 57) in 81% yield with 99.5% purity. The quantum efficiency determined was found to be 4> = 1.0. 

West and co-workers11 achieved far greater sensitivity enhancement by trapping readily atomized elements, which had been nebulized conventionally for periods of up to a few minutes, onto the outer surface of a small bore, water-cooled quartz tube. If the water was then drained rapidly, the tube temperature quickly rose and the element was atomized off the surface. For cadmium in calcium chloride extracts of soil, for example, a detection limit of 4 ng (g soil) -1 was reported. A water-cooled double silica tube atom trap similarly has been very successfully employed for the determination of cadmium and lead in natural waters by flame AAS.12 Some further examples of applications of atom trapping are included in Chapter 7. 

Andreae described a method for the sequential determination of arsenate, arsenite, mono-, di- and trimethyl arsine, MMAA, DMAA and trimethylarsine oxide in natural waters with detection limits of several ng/1. The arsines are volatilized from the sample by gas stripping the other species are then selectively reduced to the corresponding arsines and volatilized. The arsines are collected in a cold trap cooled with liquid nitrogen. They are then separated by slow warming of the trap or by gas chromatography, and measured with atomic absorption, electron capture and/or flame ionization detectors. He found that these four arsenic species all occurred in natural water samples. 

Detection of carbon and hydrogen. The detection of carbon and hydrogen is based upon the formation of carbon dioxide and water when compounds containing these elements are heated with copper oxide. The formation of carbon dioxide is detected by passing the gases produced through a solution of barium or calcium hydroxide, whereby barium or calcium carbonate is precipitated. The formation of water is detected by the appearance of droplets in the upper (cool) part of the ignition tube. 

The homogeneity has been verified at the level of intake of 0.25 g. The method uncertainty was measured by seven replicate analysis of dissolutions of a coal CRM (NBS 1632a). F and Cl were determined by ion chromatography after oxygen combustion and absorption in water cooled in ice. No in-homogeneity was detected for fluorine. For Cl, a significant difference between the CV of the method and the CV between-bottles was demonstrated the very low Cl content led to a large uncertainty of measurements which could, however, not explain the differences observed in the within- and... 

---