Water iron determination

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. 

International Standard Organization. 1988. Water quality. Determination of iron. Spectrometric method using 1, 10-phenanthroline. ISO 6332. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

The Pacific Scientific (PSCO) simple regression analysis, based on Draper and Smith (il) was applied to the absorbance data itself and to the 1st and 2nd derivative data using as constituent data total iron determined by XRF, and water by gravimetric measurement. Regressions reported here were performed at the wavelength selected by the computer as giving the best correlation and also at a number of additional wavelengths associated with prominent spectral features. 

Dissolved metal determinations with a large range of sensitivities are also possible. Manganese can be determined colorimetrically with dihy-droxyiminomethane (formaldioxime) (46). An iron determination with an amperometric detector that can resolve iron(II) and iron(III) has been reported (36). Dissolved iron can also be determined with ferrozine (47). The detection limits obtained with these analyses are on the order of 1 [xM. This level is not low enough for work in open ocean water, but the analyses would be of use in anoxic water and the interstitial water of sediments. 

Ammonium acetate buffer for iron determination Dissolve 25 g ammonium acetate (Sigma) in 10 ml water, add 70 ml glacial acetic acid and adjust volume to 100 ml with water. 

A FIA method using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol was developed for the simultaneous determination of Fe and Zn in human hair [21]. The metod using sulfosalicyclic acid was developed for the determination of Fe in oil [22]. Iron(II) and total Fe in natural waters was determined with 3-(2-pyridyl)-5,6-diphenyl-l,2,4-triazine [23]. 

Iron concentrations in extracts were measured in triplicates with a Hitachi-Z8100 atomic absorption spectrophotometer equipped with a Zeeman correction system. The flame atomizer was used for extracts from total digestions and acid extractions the flameless graphite furnace was used for extracts of sulfidic iron. The contents of iron from sequential extractions were corrected for water contents (but not for salt contents) in sediments in order to get concentrations on a dry weight basis. Accuracy and precision for Fe analysis were checked by replicate extraction analysis (n = 5) of standard reference material BCSS-1, which is issued by the National Research Council, Canada and has a certified iron content of 3.287 0.098% our analytical value was 3.266 0.056%, indicating good accuracy of our analyses. The relative precision for iron determination in this study is better than 5%. 

In the ferro-alloy industry the PAH emission is due to contact between hot metal and tarry products in electrodes and shutters. Only data for PAH emissions to water has been found for this source (29). However, assuming equal emission to water and air (50% efficiency in the wet scrubbers), this source has an emission factor of 10 g PAH per ton alloy. In a study in a Norwegian iron work, emissions to water were determined (29). PAH emission is due to the use of Soderberg electrodes. Making the same assumptions as above with the scrubber efficiency, the iron works emit 60 g PAH per ton produced iron. 

Iron determination samples include pharmaceutical products, drinking and natural water, aluminum alloys, multivitamins, and infant milk products. 

Students also gain experience with calibration curves in the course. A common theme of all the early experiments is determining the calibration curve for every experiment. When determining iron concentrations in water, students were surprised not only because the iron determination showed a concentration below the detection limit, but also the calculated values were calculated to be less than zero. Here the students ask "How can 1 have a value less than zero " This was an excellent chance to reinforce the concept of establishing the zero intercept with a calibration curve. 

Ugo P, Moretto LM, Rudello D, Bitriel E, Chevalet J (2001) Trace iron determination by cyclic and multiple square-wave voltammetry at nafion coated electrodes. Application to pore-water analysis. Electroanalysis 13 661-668... 

Methanol can be converted to a dye after oxidation to formaldehyde and subsequent reaction with chromatropic acid [148-25-4]. The dye formed can be deterruined photometrically. However, gc methods are more convenient. Ammonium formate [540-69-2] is converted thermally to formic acid and ammonia. The latter is trapped by formaldehyde, which makes it possible to titrate the residual acid by conventional methods. The water content can be determined by standard Kad Eischer titration. In order to determine iron, it has to be reduced to the iron(II) form and converted to its bipyridyl complex. This compound is red and can be determined photometrically. Contamination with iron and impurities with polymeric hydrocyanic acid are mainly responsible for the color number of the merchandized formamide (<20 APHA). Hydrocyanic acid is detected by converting it to a blue dye that is analyzed and deterruined photometrically. 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Environmental. The toxicity of cyanide in the aquatic environment or natural waters is a result of free cyanide, ie, as HCN and CN . These forms, rather than complexed forms such as iron cyanides, determine the lethal toxicity to fish. Complexed cyanides may revert to free cyanide under uv radiation, but the rate is too slow to be a significant toxicity factor. Much work has been done to estabhsh stream and effluent limits for cyanide to avoid harmful effects on aquatic life. Fish are extremely sensitive to cyanide, and the many tests indicate that a free cyanide stream concentration of 0.05 mg/L is acceptable (46), but some species are sensitive to even lower concentrations. 

---