Washing of samples

Washing of samples to determine water soluble fraction or for ashing to determine organic content... 

Hair Washing of samples with acetone and water digestion with HN03 and heat oxidation with permanganate solution and heat cooling and addition of hydroxylamine hydrochloride reduction of mercury with SnCI2 purging to detector CVAAS NR 100-101 Pineau et al. 1990... 

Figure 13. Steps in the electrokinetically-controlled immunoassay. Arrows indicate flow direction. Solid arrows stand for major flows, and dashed arrows, minor flows, (a) Loading and incubation of samples. Sample solutions were dispensed from the sample weUs to the reaction region and discharged into the waste well, (b) Washing of samples. Buffer solution flushed sample solutions from the reaction region back into the sample wells, (c) Second washing of samples. Sample solutions having entered the antibody channel during the previous three steps were flushed into the waste well, (d) Loading and incubation of detection antibody, (e) Washing of detection antibody.

Precipitation and Purification. During the hydrolysis, control tests are made by turbidimetric titration of samples taken intermittently. When the desired degree of hydrolysis is reached, the ester is precipitated from the reaction solution into water. It is important for the precipitate to have the proper texture for subsequent washing to remove acid and salts for thermal stabilization. Before precipitation, the reaction solution is usually diluted with additional aqueous acetic acid to reduce the viscosity. If a flake texture is desired, the solution is poured into a vigorously stirred, 10—15% aqueous acetic acid. To precipitate the acetate in powder form, dilute acetic acid is added to the stirred reaction solution. In both cases, the precipitated ester is suspended in 25—30% aqueous acid solutions and finally washed with deionized water. The dilution, precipitation temperature, agitation, and strength of the acid media must be controlled to ensure uniform texture. 

Note in making up the chromic acid solution it is advisable to dissolve the silver nitrate separately and add it to the boiling chromic acid to prevent excessive crystallisation of the silver chromate. The chromic acid must be free from sulphate to avoid attack on the zinc. Immerse each specimen for 15 s in a 6% solution of hydriodic acid at room temperature to remove the remaining corrosion products. Immediately after immersion in the acid bath, wash the samples first in tap water and then in absolute methanol, and dry in air. This procedure removes a little of the zinc and a correction may be necessary. 

In view of the foregoing remarks, it is clear that all glassware used in the preliminary treatment of samples to be subjected to stripping voltammetry, as well as the apparatus to be used in the actual determination, must be scrupulously cleaned. It is usually recommended that glassware be soaked for some hours in pure nitric acid (6 M), or in a 10 per cent solution of pure 70 per cent perchloric acid, followed by washing with de-ionised water. 

A sample of PeRu (614 mg, 1 mmol) was suspended in molten 4,4 -bipyridine (4.7 g, 30 mmol) and the mixture was heated for 24 h at 120 "C. Excess ligand was removed either by washing of the mixture with EtOH or by high-vacuum sublimation at 90 C. A violet powder was obtained yield 926 mg ( 100%). 

After hybridization and washing, the samples were stained with DAPI (4, 6-di-amidino-2-phenylindole), which apparently associates in the minor groove of double-stranded DNA (Kapuscinski 1990). DAPI from Sigma was used. Binding of DAPI to double-stranded DNA occurs with about a 20-fold fluorescence enhancement, which usually does not occur with single-stranded DNA (Haugland 1992). 

Experimental conditions are listed in Table 2. After pyrolysis of samples at 1073K, the product char was washed with pure water and chlorine of the leachates was analyzed by ion chromatography. Refer to the reference [3] for a detailed experimental procedure. 

Tests should also be done in the presenee of organic matter (e.g. albumin) and in hard water. It is important to remember when performing viable counts that care must be taken to ensure that, at the moment of sampling, the disinfection process is immediately arrested by the use of a suitable neutralizer or ensuring inactivation by dilution (Table 11.4). Membrane filtration is an alternative procedure, the principle of whieh is that treated cells are retained on the filter whilst the disinfectant forms the filtrate. After washing in situ, the membrane is transferred to the surface of a solid (agar) reeoveiy medium and the eolonies that develop on the membrane are counted. 

Pretreatment of hair samples also includes an extraction, usually with an alkaline sodium hydroxide solution, followed by cleaning up with LLE with n-hexane/ethyl acetate. Instead of LLE, the employment of SPE is also possible. Furthermore, the solid phase microextraction (SPME) in combination with head-space analysis is usable [104-106]. In the case of using hair samples, possible external contamination (e.g., by passive smoking of Cannabis) has to be considered as false positive result. False positive results can be avoided by washing of the hair samples previous to extraction [107]. Storage of collected samples is another important fact that can cause false results in their content of A9-THC and metabolites [108-110]. 

Washes EasyFill transfer line with 1 mL of sample. 

A clean sampler should be used at different sampling points in order to prevent contamination as described earlier. A borer with a liner is recommended to minimize contamination. Using this type of sampling device, only the liner is exchanged. When a borer has to be re-used, it should be thoroughly washed and rinsed with distilled water. Other sampling instruments are dealt with in the same manner. 

The sample water container should be made of appropriate materials to avoid adsorption of the chemical of interest on the vessel surfaces. In most cases, a glass bottle may be better than a plastic bottle. The bottle is washed with an organic solvent in advance and also washed with sample water just before sampling. The bottle should be tilled to the limit with water and capped tightly with a Teflon seal to prevent contamination. The top 1-cm of water is not taken to prevent the mixing of floating materials such as oil. 

A short weathering time for hand wash and face wipe samples is appropriate since these types of samples taken from test volunteers are usually processed and frozen immediately and are not subjected to weathering as are the dosimeter or air matrices. 

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