Analysis methods water extraction

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

RAPID PHOTOMETRIC METHODS FOR WATER ANALYSIS IN FIELD. EXTRACTION-FREE RAPID PROCEDURES FOR THE DETERMINATION OF TRACES OF REGULATED METALS WITH l-(2-PYRIDYLAZO)-NAPHTOL-2... 

Supercritical fluid extraction (SFE) and Solid Phase Extraction (SPE) are excellent alternatives to traditional extraction methods, with both being used independently for clean-up and/or analyte concentration prior to chromatographic analysis. While SFE has been demonstrated to be an excellent method for extracting organic compounds from solid matrices such as soil and food (36, 37), SPE has been mainly used for diluted liquid samples such as water, biological fluids and samples obtained after-liquid-liquid extraction on solid matrices (38, 39). The coupling of these two techniques (SPE-SFE) turns out to be an interesting method for the quantitative transfer... 

EPA. 1997e. Methods and guidance for analysis of water. Method 508.1 Determination of chlorinated pesticides, herbicides, and organohalides by liquid-solid extraction and electron capture gas chromatography. U.S. Environmental Protection Agency, Washington, DC. EPA 821-C-97-001. 

A sequential analysis protocol includes three steps (1) extraction in water or other appropriate solvent for the colorant, (2) purification or concentration of the colorant, and (3) separation coupled with detection of the target molecule. Different methods of extracting synthetic colorants from foods have been developed using organic solvents followed by SPE protocols using as adsorption support RP-C18, amino materials, or Amberlite XAD-2. Eor qualitative evaluations, the easiest option for separating colorant molecules from unwanted ingredients found in an extract is SPE on polyamide or wool. 

Other extraction methods use an SPE disk and SPME. The analysis of water samples using SPE disks (SPE-Cig disk) was performed according to the methodology described by Albanis and Hela. Generally, the SPME method is a more reliable technique than SPE for trace analysis that can shorten the analytical procedure. 

Applications The method is in use for the determination of water extractable organics in PA6 and PA4.6, and for alkane extraction of waxes from HDPE (in nitrogen atmosphere to prevent oxidation) [156]. Ethylene-bis-stearamide (EBA) can be extracted from ABS in 30 min using intermittent extraction in this case quantitative Soxhlet extraction was not possible. Nelissen [157] has used intermittent extraction with MTBE for the analysis of the flame retarder system of Tribit 1500 GN30. 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

A method for extraction, purification and preconcentration of dialkyldimethylammo-nium compounds and other detergents before determining their concentration in sewage water and activated sludge was described. It consists of a series of LLE and LC operations, the details of which are dependent of the original matrix, and end analysis was by HPLC-ELCD406. 

All extract preparation and analysis methods have biases and potential weaknesses. For example, most of the methods described above recover polar, water-soluble compounds poorly if at all, very volatile compounds may be obscured by solvent peaks during analysis, or compounds may degrade during extraction or analysis (e.g., [25]). 

HPLC has been shown as an effective method in the fractionation and preparation of AHLs for structural analysis. Preparation of AHL-containing samples for HPLC analysis requires their extraction with organic solvents such as dichloromethane or ethyl acetate [37]. Usually, C8 reverse-phase columns are employed and samples eluted with either gradient or isocratic mobile phases, e.g. acetonitrile-water. Fractions are analysed for the presence of AHLs using the biosensors described in the previous section. AHLs from active fractions can then be identified using more powerful techniques (see following sections). 

For most analyses, it is necessary to separate the analytes of interest from the matrix (i.e., soil, sediment, and water). Extraction of analytes can be performed using one or more of the following methods (1) extracting the analytes into a solvent (2) heating the sample, as may be necessary to remove the solvent and for the analysis of volatile compounds and (3) purging the sample with an inert gas, as is also used in the analyses of volatile compounds. 

---