Mercury, methyl, determination

However, using the biphasic system the methyl mercury was determined in 10-70 ppb, which corresponds to 18-63% of inhibition with y = 1.5+1.2x where x is the concentration of methyl mercury in ppb and R — 0.991, the relative standard deviation is equal to 5%. 

Stordal M. C. and Gill G. A. (1995) Determination of mercury methylation rates using a 203-Hg radiotracer technique. Water Air Soil Pollut. 80, 125—TiA. 

The between bottle homogeneity was verified by the determination of total and methyl mercury on sample intakes of 0.2 g. For the determination of total mercury, the samples were mineralised by digestion using nitric acid. The final determination was performed by CVAAS. Methyl mercury was determined by CGC/ECD after extraction of 0.2 g fish powder in toluene, back extraction with a cysteine acetate solution and further extraction with toluene. Calibrations were performed by standard additions. The study showed that the two materials are homogeneous at an analytical portion of 0.2 g and above for total and methyl mercury [7]. 

Bottles were kept at respectively -20°C, +20°C and +40°C over a period of 12 months and total and methyl mercury were determined at regular intervals during the storage period. No instability could be demonstrated [7],... 

To perform the instrument validation and determine analytical figures of merit, stock standard solutions of dimethyl mercury, methyl mercury chloride, and ethyl mercury chloride were prepared by dissolving the pure compounds in HPLC Grade toluene. Each solution was prepared to approximately 100 jug/g of the mercury compoimd. These solutions were obtained... 

Mercury speciation in hair samples has been carried out using reverse phase chromatography following a digestion at room temperature." " Methyl and inorganic mercury were determined using this method in less than 7 min, which is a vast improvement on lengthy extractions used previously to remove methyl mercury from hair. 

Procedure (indirect method). Weigh out accurately 0.1-0.2 g of the ammonium salt into a 500 mL Pyrex conical flask, and add 100 mL of standard 0.1M sodium hydroxide. Place a small funnel in the neck of the flask in order to prevent mechanical loss, and boil the mixture until a piece of filter paper moistened with mercury(I) nitrate solution and held in the escaping steam is no longer turned black. Cool the solution, add a few drops of methyl red, and titrate with standard 0.1M hydrochloric acid. Repeat the determination. 

The organo-corrinoids show similar behavior, but also additional complications. Rate constants have been determined 84) for the attack of mercury(II) acetate on various organocobalt cobinamides (X = H2O or absent) and cobalamins (X = 5,6-dimethylbenziminazole). The first complication, which has to be born in mind when comparing the cobinamides with the cobalamins or DMG complexes, is that the organocobin-amides are partly (R = vinyl and methyl) or wholly (R = Et, -Pr, t-Pr,... 

DeWild JF, Olson ML, Olund SD. 2002. Determination of methyl mercury by aqueous phase ethylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection, U.S. Geological Survey Open File Report 01 45, 23 p. 

Quevauviller Ph, and Maier EA (1999) Interlaboratory studies and certified reference materials for environmental analysis - the BCR approach. Elsevier, Amsterdam Quevauviller Ph, Drabaek I, Muntau H, Biahchi M, Bortoli A, and Griepink B (1996a) Certified reference materials (CRMs 463 and 464) for the quafity control of total and methyl mercury determination in tuna fish. Trends Anal Chem 15 160-167. 

Horvat, M., Bloom, N.S., and Liang, L., Comparison of distillation with other current isolation methods for determination of methyl mercury compounds in low level environmental samples, Part II, Water Analytica Chimica Acta, 282, 153-168, 1993. 

Yamamoto et al. [60] determined picogram quantities of methyl mercury and total mercury in seawater by gold amalgamation and atomic absorption spectrometry. Methyl mercury was extracted with benzene and concentrated by a succession of three partitions between benzene and cysteine solution. Total mercury was extracted by wet combustion of the sample with sulfuric acid and potassium permanganate. The proportion of methyl mercury to total mercury in the coastal seawater sampled was around 1%. 

A number of workers have described methods for the determination of mercury in which the mercury is first reduced to the element or collected as the sulfide on a cadmium sulfide pad. It is then volatilized into a chamber for measurement. These techniques are extremely sensitive. Thillez108) recently described a procedure for urinary mercury in which the mercury is collected on platinum and then volatilized into an air stream. Rathje109) treated 2 ml of urine with 5 ml of nitric acid for 3 min, diluted to 50 ml, and added stannuous chloride to reduce the mercury to the element. A drop of Antifoam 60 was added and nitrogen was blown through the solution to carry the mercury vapor into a quartz end cell where it is measured. Six nanograms of mercury can be detected. Willis 93) employed more conventional methods to determine 0.04 ppm of mercury in urine by extracting it with APDC into methyl-n-amyl ketone. Berman n°) extracted mercury with APDC into MIBK to determine 0.01 ppm. 

The overall process given by reaction (1) and reaction (2) is common to all mechanisms proposed for the decomposition of this alkyl. Whether this process occurs as written or by the simultaneous release of both methyl radicals is uncertain. Gowenlock et al.66 tried to resolve this problem and the similar problem that arises with other mercury alkyls by determining D(RHg-R) [R = CH3, C2H5, (CH3)2CH, CH3CH2CH2CH2] from appearance potential measurements. 

Kimura and Miller [28] have also studied the decomposition of organic fungicides in soil to mercury vapour and to methyl- or ethylmercury compounds and devised methods for the determination of these compounds in the vapours liberated from the soil sample. The mixed vapours of mercury and organomercury compounds is passed successively through bubblers containing a carbonate-phosphate solution to absorb organic... 

In the 1960s, organic residues (e.g. DDT, PCBs, methyl mercury) began to be detected in several species of shellfish, fish and fish-eating birds [1,2]. Since then, assessment of the bioaccumulation of chemicals has been considered decisive for determining the potential hazard and environmental risk it is regulated by various official organisations such as the OECD [3], EPA [4,5] and ASTM [6],... 

The Joint FAO/WHO Expert Committee determined that PTWI for mercury via all possible physiological routes should not exceed 5 pg per g of body weight, and only two thirds may be in the form of a methyl derivative (WHO, 1993). 

In mercury speciation studies, pressurized liquid extraction (PLE), microwave-assisted extraction (MAE), and supercritical fluid extraction (SEE) are employed [33]. In particular, methyl-mercury is extracted by the Westoo method [33,34], which consists in a leaching process with hydrochloric acid, the extraction of the metal chloride into benzene or toluene, the addition of ammonium hydroxide that converts the metal species to hydroxide and the saturation with sodium sulfate. Most of the HPLC methods reported in literature for the determination of organomercury compounds (mainly monomethyhnercury, monoethyhnercury, and monophenylmercury) are based on reversed... 

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