Preservation additives storage

Stability of surfactants in a water matrix, even using different preservation agents, is poor and serious, quantitative and qualitative changes in sample integrity occur if the storage exceeds 7 days. The most suitable preservation additive is formaldehyde (minimum 3%) for non-ionic surfactants and LAS, and acidification to pH < 3 for benzene and naphthalene sulphonates. However, storage for longer than 7 days is not recommended. 

Ion chromatography high-performance liquid chromatography (HPLC) is the method of choice for the quantification of oxalate, glycolate, and glycerate [3,4]. In addition, preservation and storage of the liquid samples may influence the stability of oxalate and glycolate. Use of urinary filter spots is a practical alternative approach for the collection and safe transport of samples to be analyzed for many metabolic disorders [5]. 

Unfiltered and unpreserved groundwater water samples collected for total and dissolved metal analyses arrived to the laboratory in a cooler with ice three days after collection. On the fourth day after collection the laboratory filtered the samples for dissolved metal analysis and preserved all samples with nitric acid. The violation of the preservation requirements (no acid ice instead of ambient storage temperature) had a marginal effect on the concentrations of total metals as the addition of acid dissolved most of the metals that may have precipitated in the sample container. That is why the chemist accepts the total metal results, but qualifies them as estimated data. However, because improper preservation and storage have grossly compromised dissolved metal concentrations, the chemist rejects the dissolved metal results and requests that the water be resampled and reanalyzed. 

Water solutions of mercury in the fig/L concentration range have been found to be unstable due to absorption to the storage containers and/or evaporation after spontaneous reduction to Hg(0). Pretreatment of glass vessels with an acid-dichromate solution has been reported to considerably reduce loss of mercury from dilute (0.3 fig/L) standards, probably due to saturation of the available adsorption sites with chromium (Litman et al., 1975). Numerous other container treatment procedures and preserving additives have been suggested to avoid loss of mercury from aqueous samples (see section aqueous samples ). 

The manufacture of the HCT/P does not involve the combination of the cell or tissue component with a drug or a device, except for a sterilizing, preserving, or storage agent, if the addition of the agent does not raise new clinical safety concerns with respect to the HCT/P. 

Dispersions to be added to latex must have good storage stabiHty and be compatible with the latex the pH of each should be similar to that of the latex, eg, pH 8.5—11 for ammonia-preserved latex and pH 3.5 for cationic-preserved concentrates. Addition of low pH materials to high pH latex or vice versa generally results in mutual precipitation and coagulation of the suspended mbber particles. 

In many cases, there is difficulty in preserving residues in samples after collection and prior to pesticide analysis which coincides with a rapid further degradation and mineralization of the pesticide residues under most environmental conditions. Storage stability studies and studies on the reactivity of sample collection equipment in addition to field quality assurance procedures can help address some of these questions. Concerns are accentuated for compounds that have short half-lives in the environment but still have high acute toxicity. 

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