Sample preparation homogenisation

Figure 5.1.2 Matrix solid-phase dispersion (MSPD) extraction as a micro-preparative extraction technique for an on-flow LC-NMR-MS screening. Since the latter requires only sample amounts in the 0.5-2 mg range, the sample preparation can be achieved by fast small-scale extraction procedures, such as MSPD. This is a sample preparation technique that combines both sample homogenisation and extraction of compounds of interest in one single step starting from the intact sample material. Thus, it simplifies the extraction and clean-up steps, reduces the sample manipulation and is much faster than conventional techniques. It is therefore very well suited for a rough separation of extracts into classes of compounds of similar polarities, which can then be submitted to LC-NMR-MS analysis...

Samples, as taken, are often unsuitable for direct analytical measurement. These samples will require some pre-treatment. Sample pre-treatment is a term used to encompass a variety of sample preparation procedures, including pre-concentration, clean up, extraction, dissolution, digestion and homogenisation. 

Four 680 L polyethylene containers (two for each solution) to be used for the sampling, preparation and homogenisation of the candidate CRMs were cleaned with detergent, rinsed with distilled water and soaked with diluted pro-analysis nitric acid (1 10). The containers were rinsed again with Milli-Q water and soaked with Milli-Q water for a period of at least one month prior to the use of the containers. Tubings used for filtration and homogenisation were also cleaned at the same time as the container cleaning procedure. 

An alternate sample pre-extraction preparation was to blend the composite sample without the addition of water. Then, the analytical sample was weighed, ethyl alcohol was added, the sample was homogenised again, diatomaceous earth was added, and finally the pre-treated, chopped sample was placed in the thimble. At this point, the sample should not be dried in an oven due to the fire hazard with ethyl alcohol. The ethyl alcohol wiU be extracted away in the first few minutes of the dynamic extraction. It may be preferable to carry out the alcohol drying step of the SFE at a low density (lower than 0.40 g/mL) and a temperature of perhaps 80 C. The pre-treated sample - enveloped in the filter paper - was input to the SFE where extraction and reconstitution proceeded. 

This book attempts to cover chemical and ecotoxicological analysis related to routine contaminated land investigations. It does not cover analysis related to research or specialist one-off project type investigations. The following chapter deals with soil analysis method requirements, how methods should be validated and the need for all methods to meet clearly defined performance requirements. It also covers quality assurance/quality control aspects. Chapter 3 covers the key, and problematic area of sample homogenisation and the initial sample preparation. Chapter 4 covers the analysis of metals and elemental... 

As well as sampling, another important aspect of sample preparation for drug analyses is the homogenisation of a subsequent extraction of the sample. This step is necessary, particularly if we have a powder that is not homogenous. A number of homogenisation techniques are available in drug analysis and these are summarised in Table 11.1. 

To prepare real samples for voltammetric and spectroscopic analyses, each vegetable sample was accurately washed many times using Milli-Q deionised water. Then all samples were lyophilised, powdered, homogenised, dried at 80 °C for 24h and mineralised for the analyses as described above (see section 5.2 Sample Preparation ). 

Protein concentration can be determined using a method introduced by Bradford,4 which utilises Pierce reagent 23200 (Piece Chemical Company, Rockford, IL, USA) in combination with an acidic Coomassie Brilliant Blue G-250 solution to absorb at 595 nm when the reagent binds to the protein. A 20 mg/1 bovine serum albumin (Piece Chemical Company, Rockford, IL, USA) solution will be used to prepare a standard calibration curve for determination of protein concentration. The sample for analysis of SCP is initially homogenised or vibrated in a sonic system to break down the cell walls. 

Preparation of AIR and extraction of pectic fractions For the preparation of the alcohol-insoluble residue (AIR) the apples were peeled, cut into small pieces and boiled in 96% ethanol for lOmin. After this enzyme inactivation step, the sample material was blended, homogenised and filtered through a G3 sintered glass niter funnel. The residue was washed with 96% ethanol, followed by acetone and diethyl-ether, dried overnight at 40°C under vacuum and stored at -20°C in the dark. Portions of about lOg of AIR were fractionated according to the method of Selvendran et al. [10] as shown in figure 1. 

Three peat samples (2 m each) were taken at two peat production areas in Finland, namely Kailasuo and Piipsanneva. They were homogenised and prepared as pieces of different density and diameter with laboratory-scale machines. Peat properties are shown in Table 3. Aho classified the peat into three groups with respect to degree of decomposition of chemical structure. The peat types were denoted by S for low decomposition degree, C for medium and LS for high degree of decomposition. 

The material from an appropriate bulk supply of the matrix material is weighed into a suitable container and homogenised. Where appropriate, portions of the matrix material are tested for the analytes of interest and for possible interferences. Pesticide and environmental test samples are usually prepared by spiking known amounts of substances of specified chemical purity into the bulk sample matrix. The spiking process is witnessed and cross-checked by a second scientist and full records of the process and of reference standard solutions used are maintained so that they can be verified if required. 

After preparation and final homogenisation, the prepared samples are sub-divided and packaged into labelled, individual test samples. 

---