Dataset Information

Quantifying semi-volatile organic contaminants in solution by internal standard addition method requires prompt addition of the internal standards.

ABSTRACT: The precision and accuracy of quantifying semi-volatile organic compounds (SVOCs) in solution by GC/MS, particularly when volume errors are unpredictable or difficult to control, are improved by utilizing internal standards (IS). Not obvious though is the extent to which timing IS addition affects measurement. To illustrate this fact, the mean concentrations of 60 SVOCs (40 or 80 ?g/mL) in two identical solutions into which IS were added at different times are compared in this study. In one solution, IS were added promptly on preparation (reference); in the other, IS were added after 36 days of incubation (treatment). To investigate the role that temperature might play here as well, equal fractions of each solution were incubated at -?20 °C, 4 °C or 22 °C. Results, as determined by one-way ANOVA, show that there were no differences between the reference solutions at the beginning and after 36 days (F3,236?=?0.244, p?=?0.865), but that significant differences exist between the reference solutions collectively and the treatment irrespective of temperature (F6,413?=?6.76, p?=?1.99e-06). These results, confirmed by a post hoc analysis, suggest that uncertainty is introduced into SVOC quantitation when internal standards are not added promptly into SVOCs solutions on preparation.

SUBMITTER: Otim O

PROVIDER: S-EPMC7572397 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Quantifying semi-volatile organic contaminants in solution by internal standard addition method requires prompt addition of the internal standards.

Otim Ochan O Rocha Jesus J

Scientific reports 20201019 1

The precision and accuracy of quantifying semi-volatile organic compounds (SVOCs) in solution by GC/MS, particularly when volume errors are unpredictable or difficult to control, are improved by utilizing internal standards (IS). Not obvious though is the extent to which timing IS addition affects measurement. To illustrate this fact, the mean concentrations of 60 SVOCs (40 or 80 μg/mL) in two identical solutions into which IS were added at different times are compared in this study. In one solu ...[more]

PMID: 33077740

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Project description:An inherent issue in high-throughput rRNA gene tag sequencing microbiome surveys is that they provide compositional data in relative abundances. This often leads to spurious correlations, making the interpretation of relationships to biogeochemical rates challenging. To overcome this issue, we quantitatively estimated the abundance of microorganisms by spiking in known amounts of internal DNA standards. Using a 3-year sample set of diverse microbial communities from the Western Antarctica Peninsula, we demonstrated that the internal standard method yielded community profiles and taxon cooccurrence patterns substantially different from those derived using relative abundances. We found that the method provided results consistent with the traditional CHEMTAX analysis of pigments and total bacterial counts by flow cytometry. Using the internal standard method, we also showed that chloroplast 16S rRNA gene data in microbial surveys can be used to estimate abundances of certain eukaryotic phototrophs such as cryptophytes and diatoms. In Phaeocystis, scatter in the 16S/18S rRNA gene ratio may be explained by physiological adaptation to environmental conditions. We conclude that the internal standard method, when applied to rRNA gene microbial community profiling, is quantitative and that its application will substantially improve our understanding of microbial ecosystems.IMPORTANCE High-throughput-sequencing-based marine microbiome profiling is rapidly expanding and changing how we study the oceans. Although powerful, the technique is not fully quantitative; it provides taxon counts only in relative abundances. In order to address this issue, we present a method to quantitatively estimate microbial abundances per unit volume of seawater filtered by spiking known amounts of internal DNA standards into each sample. We validated this method by comparing the calculated abundances to other independent estimates, including chemical markers (pigments) and total bacterial cell counts by flow cytometry. The internal standard approach allows us to quantitatively estimate and compare marine microbial community profiles, with important implications for linking environmental microbiomes to quantitative processes such as metabolic and biogeochemical rates.

Dataset Information

Quantifying semi-volatile organic contaminants in solution by internal standard addition method requires prompt addition of the internal standards.

Publications

Quantifying semi-volatile organic contaminants in solution by internal standard addition method requires prompt addition of the internal standards.

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