Homogeneity of samples

Chili fruits Homogenization of sample with benzene isopropanol (3 1) clean-up extract using carbon celite (1 1) GC/ECD 0.005 pg per sample 96.4 ( endosulfan) 97 ( endosulfan) 96.2 (endosulfan sulfate) Pokharkar and Dethe 1981... 

Fruits vegetables Homogenization of sample with acetonitrile and clean-up on Florisil column GC/ECD <1 ppm (mg/kg) 101.5B103.6 ( endosulfan) 100B102 ( endosulfan) 92.9 (endosulfan sulfate) Mitchell 1976... 

The sample is put in a 4He cryostat and enclosed by a shield thermally connected to the liquid helium reservoir. A second thermal shield connected to a liquid nitrogen reservoir encloses all the liquid helium system, allowing for a slow warming-up cycle in order to ensure thermal homogeneity of sample and holder. A window in the dewar enables the laser beam to enter the chamber and to reach the sample through small bores in both thermal shields. The sample is fixed onto a copper support that is in good thermal contact... 

Inczedy proposed a measure for homogeneity of samples, assuming a sinusoidal... 

Homogenization of sample (adding water if needed) and adsorption on activated Florisil to produce a free-flowing powder. Elution with ethyl acetate or methylene chloride. 

Homogenization of sample and extraction with acetonitrile, filtration, addition of salt and solvent evaporation. Redissolution of residue in acetone for analysis. 

Before an extraction procedure may commerce, Ure sample must be prepared so that it is in a condition for extraction of the analyte( s). This is particularly relevant for complex matrices such as animal-derived foods, the nature of which determines the kind of pretreatment step required. When analyzing semi-solid food samples, such as muscle, liver, and skin, a pretreatment step may be required. The analyte(s) must be exposed to extracting solvents to ensure maximum extraction. This may be accomplished by mechanical dispersion using a mincer/homog-enizer. The most popular approach for tissue break-up is the homogenization of samples in water or an aqueous buffer. Addition of anhydrous sodium sulfate to the tissue samples, to combine with the water present, has been carried out for facilitating the extraction of dimetridazole (379, 380). 

Extraction of lipid from small amounts (<1 g) of sample, such as that of rotifers, artemia, and larvae, may be achieved using an alternate procedure. In this approach, homogenization of sample is achieved using a vortex due to the delicate nature of tissues involved and the ease of their disintegration. The recovered lipids, similar to that in the original protocol (see Basic Protocol 2), may be used for further analysis. 

Human lung, liver, kidney, and adipose tissue (CDDs) Homogenization of sample saponification with KOH/ethanol washing with H2S04 and water extraction with hexane/acetonitrile clean-up on alumina column, elution with hexane/CH2CI2 addition of [13C]1,2,3,4-TCDD HRGC/LRMS (SIM) 10 ppt 35-115 Takizawa and Muto 1987... 

Foods (CDDs) Homogenization of sample, addition of 1,3,7,8-TCDD, and digestion with KOH/ethanol solution extraction with HRGC/ECD No data 85-106 Jasinski 1989... 

Fish tissue Homogenization of sample digestion with HCI extraction HRGC/MS/MS 2-38 pg 85-12,500 Bobbie et al. 

Fish and shell fish (methyl mercury) Homogenization of sample removal of organics by washing with acetone and benzene addition of HCI to release protein-bound methyl mercury and extraction into benzene analysis for methyl mercury chloride GC/ECD No data No data AOAC 1984 (methods 25.146-25.157)... 

Mustard seeds are small and may be difficult to detect visually in a mixture of foods substances such as herbs, spices, or grains. The seeds need to be broken open to allow efficient extraction and detection of their proteins when using ELISA techniques. Thorough homogenization of samples is needed to allow accurate determination of mustard concentration levels. 

Computer control of the room temperature shim currents that control the field homogeneity, of sample spinning rates, autosamplers, pulse sequences, and many other aspects of the instrument operation is a necessity. 

The disruption or homogenization of samples is key to obtaining good extractability of residues from test samples. This has been highlighted by McCracken et al. when comparing four different disruption techniques (probe blender, Stomacher, ultrasonic bath, and end-over-end mixer) for isolating chlortetracycline, sulfadiazine, and flumequine residues from incurred and spiked chicken muscle. An apparatus has been developed for tissue disruption, and several vendors have developed equipment to automate this technique, which was until recently a manual operation. A more detailed discussion on sample disruption can be found in the paper by Kinsella et al. ... 

In the analysis of coatings of dry paint film, the components can be characterized using microscopic techniques that can be applied to the study of the homogeneity of samples and require only small amounts of material. 

Since negative thermal ion mass spectrometry (N-TIMS) for rhenium/osmium dating (see O Sect. 17.18) was developed about 1990, not too much work has been published. This is probably due to the high rhenium blanks from the current generation of clean platinum filaments and to problems in achieving isotopic exchange and equilibrium between sample and spike for osmium. Another drawback is the non-homogeneity of samples. Because of this, rhenium and osmium concentrations may vary hy up to 40% in the same sample. 

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