Storage sampling

Sample transportation logistics Freezer storage sample processing j capabilities... 

An important consideration prior to sample collection is transportation and storage. Samples should be treated so as to retain the integrity of the sample from the moment of collection to the time of analysis. The physico-chemical characteristics of a sediment sample change during drying, with effects on the sorption-desorption behavior of chemicals. 

Crop samples, 0.5-2 kg, are chopped into small pieces and homogenized thoroughly in a food processor. A typical analytical sample size is <50 g. To prevent the potential degradation of the analytes during sample storage, samples should be frozen immediately after collection and maintained frozen until analyzed. 

MacKinnon [92] carried out a very detailed study in which sample collection and storage, sample preparation, the dry oxidation procedure, water corrections, adsorption effects, and precision and accuracy are all discussed in detail. 

Representative Samples and Sample Storage. Sample Concentration and Clean-up Solid Phase Extraction. 

Determining the occurrence of a chemical in the environment should be viewed as an integral process that involves several steps including sampling, storage, sample preparation, and ultimately detection of the chemical(s) of interest. Each of these steps has profound effects on the whole analytical and detection process of PPCPs in the... 

Uncontrolled species transformations during analysis form another source of error. For methylmercury determinations in sediments it was demonstrated that errors of up to 80% resulted from the formation of the compound from inorganic mercury during separation and analysis [28, 29], For the study of possible species transformations during analysis multiple isotope dilution could be used as a diagnostic tool for identifying the error and bias inherent in specific methods of storage, sample preparation and measurement [30, 31]. 

Possibility of storage samples at room temperature over long periods... 

Sample transport and storage Sample containers Cross-contamination from other samples... 

Sample stability 3x Freeze-thaw cycles for samples between -70 °C and room temperature 4-24 h at room temperature long-term storage sample stock and postpreparation stability. 5-10 ng/Lx6 at <6 °C for 28 days NA 3x Freeze-thaw cycles for samples between -20 °C and room temperature Ambient and 4 °C for 7 days... 

HU-synchronized root meristems were fixed for 24 h with acetic acid/chloroform/ethanol (6 3 1) and trace iron, then stored before analysis at -20 °C for at least 3 days. After storage, samples were hydrolyzed with hot 1N HCI for 25... 

Storage Samples were collected and analyzed in duplicate after 1, 2, 7, and 14 days storage at room temperature. The concentrations were about 1 mg/m. The results are presented in Table 3. They show that samples may be stored for at least 7 days. Tubes can probably be stored for significantly longer periods if they are tightly capped. 

TABLE 17.2. Summary of Quality Control Measures for Storage, Sample Preparation and Derivatization... 

In analysis of marine samples by AAS problems are encountered in sampling procedure, sample storage, sample treatment and measurement procedures. Analytical difficulties arise from the low concentration of most elements and complex matrices in marine samples. In this chapter, a general discussion on marine analysis by AAS will be provided in terms of seawater, marine organisms and sediments. 

Solid Fat Content. Similar method as described previously (3) was used. In this method, the samples were melted in nuclear magnetic resonance (NMR) tubes therefore it was essentially the lUPAC method 11.B.6 (4). To measure changes in solid fat content during storage, samples were not melted but instead, they were transferred to the NMR tubes using a rod and a piston. Measurements were taken directly at ambient temperature (23°C) at weeks 4, 8, and 12 of storage. 

Degradants (Stability Samples) Accelerated challenge samples (40 C/75% 50°C/20% RH) Long term storage samples (30°C/60% RH - 2 to 5 yrs) Isolated components... 

While specific details may differ, the general analytical procedures described in the following and summarised in Scheme 1 apply to most monitoring exercises. Firstly, the purpose of the monitoring exercise must be clearly set out, then an appropriate method of sampling must be chosen, followed (where applicable) by the choice of suitable methods for sample storage, sample preparation or preconcentration and sample separation. Lastly, identification and/or quantification of the components are performed [12]. 

Caution must be exercised to minimise errors at every stage of the characterisation. Therefore, quahty assurance/quality control principles must be apphed to sampling, sample storage, sample reconcentration and sample analysis. 

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