Organic Acids Analysis in Environmental Samples, Ion Chromatography for Determination of
Notice bibliographique
Résumé
Abstract The analysis of environmental samples typically focuses on aliphatic short‐chain organic acids. The origin of these organic acids and the motivation for their analyses are unique for each type of matrix. Environmental sample matrices are very diverse and can range from air and atmospheric precipitation such as fog, rain or snow to wastewater, drinking water or landfill leachates and soil pore water. This diversity in matrix leads to substantial differences in organic acid concentrations and different organic acid distributions in the various types of environmental samples. Hence, the analytical techniques employed have to be adapted to the particular matrix under investigation. Ion chromatography is one of the most commonly used techniques for organic acid analysis. Competing ion chromatographic methodologies are anion (ion)‐exchange chromatography (IC) and ion exclusion chromatography (ICE). The separation principles underlying each of these techniques are very different and may be used to their advantage. In IC, anions are separated by anion exchange processes between the cationic exchange groups on the resin and the eluent. Hence, inorganic anions and carboxylate anions may be analyzed at the same time (e.g. rain). Limitations of this technique set in when the inorganic anion concentration is much larger than the carboxylate concentration. As a consequence, inorganic anion peaks may mask or co‐elute with the analyte of interest. However, techniques have been developed to handle this problem, for example in drinking‐water analysis. The separation mechanism in ICE is much more complex than in IC involving Donnan exclusion, adsorption and steric exclusion. ICE is generally used for the separation of weak organic acids since strong organic acids elute in the system peak in the front of the chromatogram. Hence, large concentrations of strong inorganic anions, for example sulfate or chloride, will not interfere with the analysis of weak organic acids. However, organic acids with relatively low p Ka values may be difficult to separate from the system peak. In addition, weak inorganic acids such as carbonate have the potential to interfere with the analysis of certain organic acids if present in large enough concentrations. Other techniques than ion chromatography have been used for organic acid analysis. Direct injections of samples into a gas chromatograph are very common for measuring volatile fatty acids (VFAs) in wastewater. More complex gas chromatography (GC) methods, which include concentration and derivatization steps, have been employed to analyze for specific types of organic acids such as dicarboxylic acids in rain. Capillary electrophoresis (CE) is a newer technique, which has not been used widely in routine analysis. However, speciality applications such as the determination of organic acids in a single raindrop show the potential of this type of methodology.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,021 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».