Sample boat

Heat Stability of 2,3,7,8-Tetrachlorodibenzo- -dioxin. A sample boat containing 1-3 mg of 2,3,7,8-tetrachlorodibenzo-p-dioxin was placed in a Sargent Tube Heater (Model J-807) which contained a 1/2 inch i.d. quartz tube. Air was aspirated through the tube at a velocity of 0.02 ft/sec. This velocity gave a residence time of 21 sec. (Residence time was extended by connecting a second heater in series with the first.)... 

Thallium has been determined in 10 ml of ashed serum or in urine by extracting with sodium diethyldithiocarbamate into MIBK n°). More recently, Savory and co-workers 1131 described a wet digestion procedure for 50 ml of urine or 5 ml of serum in which the thallium is separated by extracting the bromide into ether, evaporating the ether and then taking up in dilute acid for aspiration. As little as 0.1 ppm is determined in urine. Curry et al.114) determined less than 1 ng of thallium in 200 /d of urine by using the tantalum sample boat technique. The sample in the boat is dried by holding the boat 1 cm from the flame and then it is inserted into the flame where it is vaporized. A similar procedure is used for >3 ng of thallium in 50-100/al of blood, except that the blood is preashed with 3 drops of nitric acid. Since the tantalum boat method is susceptible to interelement interferences, the method of standard additions is used for calibration. 

Ag, Zn, Pb Soil samples Treat w/HN03 -HC1, take up in H2O. Use Ta sampling boat for measurement. 253)... 

A chloric acid digestion was used by Backer 2 391 for the preparation of tissue samples. The digest is simply diluted to determine iron, zinc, and copper. The tantalum sampling boat technique was used by Emmermann and Luecke 2531 to measure lead, zinc, and silver in prepared soil solutions. White 1S81 treated ashed plants with hydroxylamine in IN hydrochloric acid to reduce and dissolve oxides of manganese, prior to its determination by atomic absorption spectroscopy. 

The Dohrmann DX 20B system is based on combustion of the sample to produce the hydrogen halide, which is then swept into a microcoulometric cell and estimated. It is applicable at total halide concentrations up to lOOOpl-10 with a precision of 2% at the lOpg L-1 level. The detection limit is about 0.5pg L-1. Analysis can be performed in 5 min. A sample boat is available for carrying out analysis of solid samples. The instrument has been applied to waste waters, soils and sediments. 

Place the weighed specimen in the sample boat, insert into the oven with the aid of tweezers provided with the instrument and close the oven... 

Turn combustion tube to horizontal, and carefully insert loaded sample boat into open end of tube. Slide or push boat, without spilling contents, until it reaches the trademark. Raise open end until tube forms a 60° to 70° angle to the horizontal plane. Tap or vibrate combustion tube on bench top while rotating tube between thumb and forefinger. Raise open end of tube and add 1 vol of Co304 and 1 vol of CuO fines equal to volume of sample. 

Raise open end until tube forms a 60° to 70° angle add additional CuO-Pt catalyst 12 mm above the sample boat. Tap or vibrate gently to eliminate voids. Add CuO-Pt catalyst to within 20-mm top of tube, again tapping or vibrating gently to eliminate voids. 

Bis[trifluoromcthyl] Ditellurium8 2.6 g (20 mmol) of tellurium tetrachloride are placed in a sample boat which is then inserted into the reaction chamber of a plasma apparatus. After evacuation, hexafluoroethane is passed through the system at a rate of 15 m//min and radiofrcqucncy power (23 watt) is applied. The products are collected in two cold traps maintained at — 78° and — 196°, and separated by trap-to-trap fractionation. The fractions are condensed on Porapak P and fractionally distilled therefrom. The fractions are then purified using a Dobson low temperature distillation apparatus yield 1.3 g (33%) red liquid b.p. — 53° m.p. -73° (Ref.12). 

The use of a rectangular graphite tube makes possible the placing of the solution in a sample boat (Fig. 5). The authors propose two changes reduction of the size of the sample space, and use of a very pure graphite from emission spectroscopy (RW-O) instead of the relatively expensive pyrolytic... 

The modification of the standard procedure involves the use of a disposable sample boat. A piece of copper foil approximately 1 X i in. in size is shaped manually into boat form. It is flamed in a Bunsen burner and dipped into methanol. After this cleaning operation, the boat is placed in a glass tube and heated briefly with a Bunsen flame while being swept with a stream of hydrogen (caution ) it is then ready for use in the procedure described by Oliver. Some typical results are given in Table I. Anal. Calcd. for CarHaoClOPzRh O, 2.32. Found 0, 2.30, 2.34. By checkers Calcd C, 64.32 H, 4.38 mol. wt., 691. Found C, 64.49 H, 4.61 mol. wt., 688 4. Calcd. for Cj7H3oC10As2Rh O, 2.05. Found O, 1.95, 2.10. By checkers Calcd C, 57.06 H, 3.88 , mol. wt., 778. Found C, 57.65 H, 4.43 mol. wt., 790 13. 

When a sample is removed from the combustion tube, care must be taken to prevent oxidation of the reduced sample. Before a sample boat is removed from the capped tube, it is allowed to cool to room temperature. This is accomplished by repositioning the combustion tube so that the sample boat is moved from the center of the furnace to a position outside of the furnace. The sample is allowed to remain in this position for one-half hour with the gas stream flowing over it before the end cap is removed and the boat is taken out. 

F, Flame atomization P, plasma atomization S, spark exdtation, sample volume 50 /il N, nebulized sample, minimum volume o l.O ml C, carbon furnace or rod, sample volume 10 d Sb, sampling boat, sample volume 0.01-1.0 ml W, platinum or iridiiun wire, sample volume 0.005-5.0 m1 R, mercury salts in solution are reduced to the metal and the metal vapor carried to the absorption cell by a stream of gas. 

Kahn, H. L., Peterson, G. E., and Sohallis, J. E., Atomic absorption microsampling with the sampling boat technique. At. Absorption Newslett. 7, 35-39 (1968). Karoum, F., and Sandler, M., High resolution gas chromatographic anal3rsis of phenolic acids and alcohols using capillary columns. Clin. Chim. Acta 32, 391-397 (1971). 

The detection limit by F-AAS for volatile metals can be improved by use of a sampling-boat attachment. By this technique, sample volumes up to 1 mL can be evaporated and then almost instantaneously introduced into the flame and vaporized. This shall be compared with the sample uptake of 0.05-0.1 mL7s, of which only about 10 % reaches the flame through a conventional spray chamber. Mesman and Smith (1970) extracted APDC-complexed mercury from 50 mL aliquots of urine into 5 mL MIBK, and analyzed 0.2 mL of... 

Fleckenstein (1985) determined mercury in solid biological samples (1 mg) by use of a graphite furnace with a graphite sampling boat and ZBGC. He estimated the detection limit at about 0.1 mg/kg. A similar technique was used by Strubel et al. (1990) for the analysis of urinary calculi. 

Khan, H.L, Peterson, G.E. and Schallis, J.E. (1968) Atomic absorption microsampling with the "sampling boat" technique. Atom. Abs. Newsl., 7,35-39. 

The apparatus employed in the synthesis is shown in Fig. 3. The combustion tube (24 in. long and 1 - in. o.d-) is made of fused quartz and the sample boats (3 in. long, i in. wide, and in. deep) are of high-purity alumina. Pure gallium(III) oxide (1.5057 g. 0.00803 mol), obtained... 

The Sampling Boat. The author has had some success with a different approach. Here, the sample is loaded into a narrow boat-shaped vessel, made out of tantalum or a similar material, and dried. The boat is then placed into the middle of a standard air-acetylene flame. For lead, selenium, cadmium, silver, and zinc, encouraging results have been obtained. The detection limit for lead, for example, is about one-fifteenth that of conventional atomic absorption spectroscopy. However, at least at the present stage of development, drawbacks exist here also. Interferences are multiplied, because of the low temperatures at which atoipiza-... 

All water used in the analysis is deionized and polished with a Millipore Simplicity system, available from Millipore Corporation, Billerica, MA, USA. Two reagents are used in the sample boats to assist the combustion of organic materials. Additive B is a coarse aluminum oxide. Additive M is a 35 50 combination of calcium hydroxide and sodium carbonate. The additives, specially prepared by Wako Pure Chemical Industries, Ltd., Osaka, Japan, are available for purchase through NIC. The phosphate buffer in the scrubber vessel was prepared finm a powdered concentrate (Wako). 

Mercury free solvents were used to dilute heavy hydrocarbon samples, when necessary. HPLC Grade toluene. Optima Grade hexanes, and low odor kerosene (Fisher Scientific) were all found to have suitably low mercury concentrations for most work. Samples were caught in precleaned, 40-mL Volatile Organic Analysis (VOA) vials with Teflon lined septa (Fisher Scientific). The ceramic sample boats and high-form crucibles are available from NIC or other suppliers. A Hamilton Gastight Model 81000 lOO-jul syringe (Fisher Scientific) was used to withdraw crude oil sample from the VOA vials. 

Ceramic crucibles that contain the necessary amount of reagent for the expected analyses are placed in a muffle furnace at 750 C the prior day. Ceramic sample boats are similarly stored in the muffle furnace to keep them free of ambient mercury contaminatiorL The sample boats and reagents are allowed to cool before use in a covered pan that is over-pressured by dry, mercury-free, filtered air from the instrument. It is important to allow the surfaces that the sample contacts to reach ambient temperature to minimize loss of elemental mercury. 

The sample boat with reagents is placed at the entrance of the combustion tube and slid into the heated zone with a long fork. The cap at the entrance to the combustion tube is screwed into place, heating mode "3" is selected, and the start button is pressed. The mercury response values from this measuring cycle are discarded. While the first boat is being heated, a second sample boat is prepared with reagents in a similar manner. At the end of the cycle, the first boat is removed and allowed to cool in a covered tray. The second boat is also subjected to one heating cycle. 

The crude oil aliquot is obtained by piercing the septum on the container and slowly drawing the sample into a 100- fil syringe. The container is inverted to dispel bubbles from the syringe. A cooled sample boat, loaded with reagent, is placed at the entrance of the combustion tube. The crude sample is injected beneath the surface of the reagent, and the boat is quickly pushed into the combustion tube. The cap is replaced, heating mode "3" has been pre-selected, and the start button is quickly pressed. 

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