Analysis

A large number of methods are available to determine organic acids in various environmental matrices. Factors such as type of organic acid, their concentrations, and sample matrix, determine largely which analytical methods are suitable for a certain sample. The overall analysis process comprises a sequence of steps starting with sampling and sampling preservation followed by sample preparation and finally instrumental analysis and data interpretation. All these steps are discussed in the following sections and put in context with environmental matrices. Table 13.3

gives an overview of methods available for organic acid analysis organized by matrix and instrumentation.

A. Sampling and Sample Preservation

Sampling is an important part of the overall analytical process. The ideal sampling technique is adapted to the matrix, prevents contamination, and results in an unaltered sample which reflects the

Sample Preparation Instrumentation

Annular denuder, aqueous extraction Cryogenic trapping

Collection on filters, freezer, aqueous extraction Collection on filters and denuder, aqueous extraction, CHCl3 preservation Scrubber, filters, aqueous extraction, CHCl3 preservation Varied

Collection on filters, freezer, ultrasonic extraction Collection on filters, ultrasonic aqueous extraction Filters, film, aqueous extraction Aqueous extraction of filters

Aqueous extraction of filters, filtration

IEC/cond.

AEC/cond.

AEC/cond.

AEC/cond., IEC/cond.

AEC/cond.

AEC/cond.

AEC/cond.

AEC/cond.

CZE/ind. UV

Acids Determined3 Detection Limits

AIR Including Atmospheric Precipitation

Formic, acetic acid

Formic, acetic, pyruvic, oxalic acid

Formic, acetic acid

Formic, acetic, glycolic, pyruvic, oxalic, (3-hydroxybutyric acid

Formic, acetic, pyruvic, glyoxylic, succinic, malonic, oxalic acid

Formic, acetic acid

C2-C5 dicarboxylic, glyoxylic acid

Formic, acetic, oxalic acid

C2-C5 dicarboxylic acids

C2-C10 dicarboxylic acids

C!-C4 moncarboxylic, glycolic, lactic, (3-hydroxybutyric acid

1-50 mg/l standards b

0.1 ppbvb

45-102 mg/l (standards)13

0.07-0.19 ppbvb b

10-50 ngb b

Comments Ref.

Gas phase, sample preservation with CHCl3 55

Gas and particulate phase, filters stored in 57

freezer

Gas and particulate phase, confirmation 58

with CZE

Gas and particulate phase organic acids, 59

confirmation with IEC

Gas and particulate phase, comparison 60

of different sampling techniques

Particulate phase 61

Particulate phase, investigated sonochemical 62

processes during extraction

Size segregated particulate phase, measured 63

also inorganic anions

Particulate phase, compared different 2

electrolytes

Particulate phase, developed and compared 64

AEC and CZE methods, investigated coelution n

0 era S

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