Sample storage impact on the assimilable organic carbon (AOC) bioassay (original) (raw)
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Measurements of assimilable organic carbon (AOC) in high saline conditions using P17
Water Science & Technology: Water Supply, 2013
Biofouling caused by the deposition or growth of microorganisms on the membrane surface is one of the major concerns in nanofiltration (NF) and reverse osmosis (RO) processes. Assimilable organic carbon (AOC) has been a useful index to assess the growth potential of bacteria. In the case of drinking water, the AOC assay method has been widely applied to estimate growth or regrowth potential of bacteria in distribution and storage systems. However, studies on AOC measurement for high salinity water samples such as brackish water and seawater are rather scarce. The objective of this research is to investigate the influence of water salinity on the conventional AOC assay method. AOC samples with different salt concentrations were prepared by varying NaCl concentration from 0 to 35,000 mg/L, while the acetate concentration was held at 100 μg/L. The number of cells produced in water samples was measured by the heterotrophic plate count (HPC) method using R2A agar. The result showed that ...
Considerations for Stability of Environmental Samples in Storage for Long-Term Studies
Analytical Chemistry - Advancement, Perspectives and Applications, 2021
It is often advantageous to store collected environmental samples for future retrospective analyses. However, information about sample stability is necessary to determine if there will be analyte loss or gain or degradation under the specified storage conditions and storage period. Failure to evaluate stability could result in inaccurate results and biased exposure assessments. As part of the National Children’s Study pilot, we considered which types of environmental samples could be stored for extended periods of time. We conducted an extensive literature review and considered the conduct of long-term stability studies for environmental samples. We present our findings and experience below as guidance for consideration by the environmental research community.
Iranian Red Crescent Medical Journal, 2015
Results of arterial blood gas analysis can be biased by pre-analytical factors, such as time interval before analysis, temperature during storage and syringe type. Objectives: To investigate the effects of samples storage temperature and time delay on blood gases, bicarbonate and PH results in human arterial blood samples. Patients and Methods: 2.5 mL arterial blood samples were drawn from 45 patients via an indwelling Intraarterial catheter. Each sample was divided into five equal samples and stored in multipurpose tuberculin plastic syringes. Blood gas analysis was performed on one of five samples as soon as possible. Four other samples were divided into two groups stored at 22°C and 0°C. Blood gas analyses were repeated at 30 and 60 minutes after sampling. Results: PaO 2 of the samples stored at 0°C was increased significantly after 60 minutes (P = 0.007). The PaCO 2 of the samples kept for 30 and 60 minutes at 22°C was significantly higher than primary result (P = 0.04, P < 0.001). In samples stored at 22°C, pH decreased significantly after 30 and 60 minutes (P = 0.017, P = 0.001). There were no significant differences in other results of samples stored at 0°C or 22°C after 30 or 60 minutes. Conclusions: In samples stored in plastic syringes, overestimation of PaO 2 levels should be noted if samples cooled before analysis. In samples stored in plastic syringes, it is not necessary to store samples in iced water when analysis delayed up to one hour.
Assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC)
Water Research, 2001
FThe objective of this study was to evaluate the necessity of measuring both assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC) as indicators of bacterial regrowth potential. AOC and BDOC have often been measured separately as indicators of bacterial regrowth, or together as indicators of bacterial regrowth and disinfection by-product formation potential, respectively. However, this study proposes that both AOC and BDOC should be used as complementary measurements of bacterial regrowth potential. In monitoring of full-scale membrane filtration, it was determined that nanofiltration (NF) removed over 90% of the BDOC while allowing the majority of the AOC through. Heterotrophic plate counts (HPC) remained low during the entire period of monitoring due to high additions of disinfectant residual. In a two-year monitoring of a water treatment plant that switched its treatment process from chlorination to chlorination and ozonation, it was observed that the plant effluent AOC increased by 127% while BDOC increased by 49% after the introduction of ozone. Even though AOC is a fraction of BDOC, measuring only one of these parameters can potentially under-or overestimate the bacterial regrowth potential of the water.
Investigation of assimilable organic carbon (AOC) in flemish drinking water
Water Research, 2005
The aim of the study was to investigate the drinking water supplied to majority of residents of Flanders in Belgium. Over 500 water samples were collected from different locations, after particular and complete treatment procedure to evaluate the efficiency of each treatment step in production of biologically stable drinking water. In this study assimilable organic carbon (AOC) was of our interest and was assumed as a parameter responsible for water biostability. The influence of seasons and temperature changes on AOC content was also taken into account.
Development of a rapid assimilable organic carbon method for water
Applied and environmental microbiology, 1993
A rapid method for measurement of assimilable organic carbon (AOC) is proposed. The time needed to perform the assay is reduced by increasing the incubation temperature and increasing the inoculum density. The ATP luciferin-luciferase method quickly enumerates the test organisms without the need for plate count media or dilution bottles. There was no significant difference between AOC values determined with strain P17 for the ATP and plate count procedures. For strain NOX, the plate count procedure underestimated bacterial levels in some samples. Comparison of AOC values obtained by the Belleville laboratory (by the ATP technique) and the Stroud Water Research Center (by plate counts) showed that values were significantly correlated and not significantly different. The study concludes that the rapid AOC method can quickly determine the bacterial growth potential of water within 2 to 4 days.
Marine Pollution Bulletin, 1997
All tions on the contents of chlorobiphenyls (CBs), DDT rights reserved components and mercury (Hg) in biological samples. Wet cod liver and wet plaice muscle tissue were stored Keywords: biological tissue; storage; quality assurance; in screw-cap jars at-5,-25 and-70°C and a PCBs; mercury; lipid. freeze-dried plaice sample was stored in the dark at ambient temperature. Contents of CBs, DDT compo-Concentrations of organochlorine compounds, such as nents and Hg were measured in the samples at 0, 4, 12 chlorobiphenyls (CBs) and organochlorine pesticides, and 24 months. Additionally, changes in the matrix and trace metals are determined in numerous environwere studied by measuring the total and extractable mental laboratories. A large number of these analytes lipid content, dry-weight content, peroxide number, are determined in biological samples, such as shellfish rancidity and by recording HPLC fat fingerprints, or fish tissue, within the framework of monitoring Homogeneity was tested by determining the K and Na programmes (Anon, 1994). concentrations in a number of samples. For several reasons there is, in many cases, a Except for CBII8 in wet plaice and Hg in cod liver, considerable period of time between the sampling and no significant changes in the concentrations of CBs, the final determination. For example, samples taken DDT components and Hg were observed. For on-board ship, where laboratory facilities are often not p,p'-DDT the study was hampered by low levels in the available, are transported to the laboratory for analysis. samples. In some laboratories, analyses of specific compounds The total lipid determination, using the method of are only carried out in batches; therefore, some Bligh and Dyer (1959), showed constant results for all samples have to be stored for a period of time. In some storage conditions, whereas extractable lipid contents cases, analyses have to be repeated and these are done were affected in wet plaice samples stored at-5 and on stored samples. Frequent repetition of the analyses-25°C. The lower extractable lipid contents coincided can require repeated thawing of the samples. In all with the transformation of triglycerides to fatty acids, "FABLE 1 found in the lipid fingerprints by HPLC, which Na and K contents of plaice muscle and cod liver (determined by suggests that fatty acids are less efficiently extracted flame AAS). by Soxhlet extraction with medium polar solvent mixtures. The peroxide numbers of wet samples at-5 RSD (%) and-25°C demonstrated that oxidation of lipids took Material Within sample Between sample place and confirmed deterioration of the matrix. With regard to the determination of CBs and DDE Plaice muscle (wet) Na 7
Journal of AOAC International
The AOAC sporicidal method (966.04) recommends the use of porcelain penicylinders and black waxed silk sutures as carriers for demonstrating the sporicidal activity of sterilants. However, the silk carriers are not suitable for evaluating the sporicidal efficacy of oxidizing agents, and an inert polyester material (Dacron) is recommended as an alternative. Dacron provides an equivalent microbial and physical challenge to silk. Microbiologically, both materials demonstrated similar HCI resistance, which is required by the AOAC test, as well as equivalent spore loading and spore wash-off. Electron microscopy showed that both materials present the same braided microstructure, providing an equivalent physical challenge to the test sterilant. Dacron was more consistent than silk, and did not require extraction prior to spore loading. The extraction method for black waxed silk was variable and incomplete, which may compromise the activity of oxidizing sterilants and add to method variabil...
Biodegradable fraction of organic carbon estimated under oxic and anoxic conditions
Water Research, 2003
The biodegradability of water samples is usually estimated with bioassays under oxic conditions. In order to overcome some of the drawbacks linked to the incubation of the samples in aerobic batches, a new protocol is proposed and tested, which is based on an organic carbon (OC) balance after a 45 days incubation under anoxic conditions with excess nitrate. The biodegradable fractions of organic matter obtained with the anoxic protocol are slightly lower than those obtained under oxic conditions. Several possible reasons for a systematic underestimation of the biodegradable organic matter under anoxic conditions are evaluated and discussed: a reduced microbial metabolic potential, significantly reduced degradation rates for the slowly biodegradable organic matter, an additional production of refractory organic compounds during the incubation, or the inhibition of the recycling of the organic matter stored in bacterial biomass. Nevertheless, the 7% difference observed on the biodegradable total OC estimations keeps low enough so that the anoxic protocol can be proposed as a convenient alternative to the oxic one. r