Open vessel technique

Bernstein, "Determination of Moisture Content of Lead Azide", PicArsnGenLab Rept 51-H1-2331 (1951) (Comparison of closed and open vessel techniques) 9)US Rubber Co, Kankakee Ordnance Works, Joliet,... 

CA 40, 2764(1946) (Polaro-graphic detn of azide ion in general and in LA in particular) 5)D.F. Vasil ev, Trudy-KomissiiAnalKhim, OtdelKhimNauk, 2, [5], 90-5(1949) CA 44, 9300-1(1950) (Polarogra-phic detn of Pb content of LA) 6)US Military Specification MIL-L 3055(1949) and Amendment 1 (1952) (Requirements for crystalline LA intended for use in manuf of detonators, fuzes and priming compns) 7)W.H. Rinkenbach A. J.Clear, "Standard Laboratory Procedures for Sensitivity, Brisance and Stability of Explosives , PicArsnTech Rept 1401 (1944), Revised in 1950 8)J. Bernstein, "Determination of Moisture Content of Lead Azide , PicArsnGenLab Rept 51-H1-2331 (1951) (Comparison of closed and open vessel techniques) 9)US Rubber Co, Kankakee Ordnance Works, Joliet,... 

Sharma et al. [13] synthesized the 2-oxazolines (iii) using the microwave assisted open vessel technique. The synthetic protocol involved the direct condensation of carboxylic acids with excess of 2-amino-2-methyl-l-propanol (i) at 170 °C. 

Method detection limit (MDL) Prepare seven samples at 3-5 times the estimated MDL concentration, as described in the U.S. ERA regulations at 40 CFR, Part 136, Appendix B, for the digestion of samples using the open-vessel technique. Note that the MDL samples should be prepared in the synthetic FGDW matrix. Analyze the MDL standards in triplicate. Calculate the standard deviation of the concentration(s) in pg/L for each analyte. The MDL is calculated as the student s t-value for the degrees of freedom (i.e., 3.143 for 6 degrees of freedom) multiplied by the standard deviation. 

Microwave-assisted synthesis of 2-oxazolines from carboxylic acids using the open vessel technique has been reported (Sharma et al., 2009). This method involves direct condensation of carboxylic acids with excess 2-amino-2-methyl-l-propanol at 170 °C to give the corresponding 2-oxazolines in moderate to excellent yields. This also proved to be simple and efficient for the conversion of carboxylic acids into 2-oxazolines. 

In modern microwave synthesis, a variety of different processing techniques can be utilized, aided by the availability of diverse types of dedicated microwave reactors. While in the past much interest was focused on, for example, solvent-free reactions under open-vessel conditions [1], it appears that nowadays most of the published examples in the area of controlled microwave-assisted organic synthesis (MAOS) involve the use of organic solvents under sealed-vessel conditions [2] (see Chapters 6 and 7). Despite this fact, a brief summary of alternative processing techniques is presented in the following sections. 

Alternative procedures are paddle dyeing for sensitive skins in an open vessel, and immersion dyeing, in which the leather passes through a dye solution and is subsequently squeezed by a roller. Spraying and roller machines have mostly replaced other techniques such as traditional brush dyeing, which colors the surface only. 

Atmospheric MAE system This second technique employs solvents with low dielectric constants. Such solvents are essentially microwave-transparent they thus absorb very little energy, and extraction can therefore be performed in open vessels. The temperature of the sample increases during extraction because it usually contains water and other components with high dielectric constants the process is thereby enhanced. Because extraction conditions are milder, this mode of operation can be used to extract thermolabile analytes. 

Gawalko and coworkers elucidated the characteristics of closed-vessel and focused open-vessel MW sample preparation techniques for the subsequent determination of Cd, Cu, and Pb, and Se in wheat, wheat products, corn bran, and rice flour by ET-AAS with transverse-heated graphite furnace [23]. Both techniques were evaluated using a total of 15 CRMs for the three food types. In the case of rice, these were the NIES 10a, 10b, and 10c Rice Flour and the NRC Rice Flour. The two techniques were equivalent in terms of agreement with the certified figures. Up to 12 samples could be processed with the closed system with minimal amounts of acid and reduced risk of contamination. Larger masses of samples could be treated by the open-vessel system. 

Open vessel acid digestion, one of the oldest techniques, is undoubtedly the most common method of sample decomposition or dissolution of organic and inorganic sample material used in chemical laboratories. This very inexpensive technique is of inestimable value for routine analysis because it can easily be automated all the relevant parameters (time, temperature, introduction of decomposition reagents) lend themselves to straightforward control. 

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