Comparison of methods with respect to efficiencies, recoveries, and quantitation of mercury species interconversions in food demonstrated using tuna fish

Abstract

Eight different analytical extraction procedures commonly used to extract mercury species from biological samples were evaluated by analyzing Tuna Fish Tissue Certified Reference Material (ERM-CE464) certified for the content of total mercury and methylmercury. Speciated isotope dilution mass spectrometry (SIDMS; US Environmental Protection Agency's method 6800) was utilized to evaluate and effectively compensate for potential errors during measurement and accurately quantify mercury species using all the extraction methods. SIDMS was used to accurately evaluate species transformations during sample pretreatment, preparation and analysis protocols. The extraction methods tested in this paper were based on alkaline extraction with KOH or tetramethylammonium hydroxide; acid leaching with HCl, HNO(3) or CH(3)COOH; extraction with L: -cysteine hydrochloride; and enzymatic digestion with protease XIV. Detection of total mercury and mercury species from all extraction methods was carried out by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography-ICP-MS, respectively. Microwave-assisted extraction and ultrasound-assisted extraction were found to be the most efficient alkaline digestion protocols that caused the lowest levels of transformation of mercury species (6% or less). Extraction with 5 M HCl or enzymatic digestion with protease resulted in the second-highest extraction efficiency, with relatively lower transformation of methylmercury to inorganic mercury (3 and 1.4%, respectively). Despite frequent use of acid leaching for the extraction of mercury species from tuna fish samples, the lowest extraction efficiencies and the highest mercury species transformation were obtained when microwave-assisted extraction with 4 M HNO(3) or CH(3)COOH was used. Transformations as high as 30% were found using some literature protocols; however, all the extractions tested produced accurate quantitation when corrected in accordance with the SIDMS method standardized in the US Environmental Protection Agency's method 6800. [figure: see text]

Robust microwave-assisted extraction protocol for determination of total mercury and methylmercury in fish tissues

“…In addition, recent definitive studies of the interconversion of mercury species during sample preparation for biological tissues using tuna fish tissue samples call into question the accuracy of results using previously reported analytical procedures [20]. Hence, reliable and rapid extraction methods for the determination of mercury species in complex matrices are of considerable interest.…”

“…Although this extraction technique offers significant benefits in terms of time, efficiency, solvent consumption and minimal risk of losing volatile compounds, only few applications have been described for mercury species in biological tissues [9,10,14]. Speciated isotope dilution mass spectrometry (SIDMS) [20,[24][25][26][27][28] a part of EPA Method 6800 [29] is a technique created specifically to account for these potential changes in native species distribution can greatly assist in the evaluation of analytical methods. SIDMS provides highly accurate and precise data as well as information regarding possible species transformations that occur during and/or after sample preparation.…”

Hg2+ion-imprinted polymers sorbents based on dithizone–Hg2+chelation for mercury speciation analysis in environmental and biological samples

“…[1][2][3][4] Among them, mercury (Hg) has become an attractive research area [1][2][3][4][5][6] because it has negative impacts on humans usually due to exposure through food, especially sh. 7,8 Its toxicity depends on its chemical forms; organic mercury compounds are generally much more toxic than inorganic mercury due to their strong lipophilic characteristics. [7][8][9][10] Hence, speciation analysis of mercury ion (Hg 2+ ) and its organic species is being increasingly investigated because the monitoring and remediation of heavy metal pollution has become a crucial global issue.…”

“…7,8 Its toxicity depends on its chemical forms; organic mercury compounds are generally much more toxic than inorganic mercury due to their strong lipophilic characteristics. [7][8][9][10] Hence, speciation analysis of mercury ion (Hg 2+ ) and its organic species is being increasingly investigated because the monitoring and remediation of heavy metal pollution has become a crucial global issue. The speciation and determination of mercury species is generally performed using chromatographic techniques, such as gas chromatography (GC), liquid chromatography (LC), ion chromatography (IC) and capillary electrophoresis (CE) for separation, 5,6,8,11 which are oen coupled with element selective detectors, e.g.…”

Validation of an analytical method for the determination of mercury in shrimp and fish

“…The difference between this kind of warming and the conventional systems is that the digestion is produced in the bosom of the dissolution and not for convection from an external source, producing an homogeneous and effective warming (Reyes, Mizanur Rahman, Fahrenholz & Skip Kingston, 2008). The advantage of the digestion with MW oven versus the digestion in a conventional open glass is the possibility of controlling the parameters of pressure and temperature, or the possibility of digest the sample in reduced times; hence the speed of warming is very high.…”