Mercury cold vapour method

With mercury, Hg° is formed instead of the hydride. A special cell, which does not need to be put into the flame is used. This is called the cold vapour method, and requires specialised instruments (reduction by SnCI2). 

Many other household products can be analysed in similar ways to those described above for chemicals. Household bleach is essentially an inorganic chemical. There has been concern expressed about mercury levels in hypochlorite bleach because of the way it is manufactured. The cold vapour reduction/aeration method referred to above is a good way of determining low mercury levels with minimal matrix problems [82]. In the past organo-mercurial compounds have been used (e.g. as bactericides) in some household products these may be selectively determined by extraction with an organic solvent (e.g. carbon tetrachloride or benzene), and then application of the cold-vapour method following the addition of cysteine acetate, or by coupled gas chromatography/atomic absorption [83],... 

Metallic mercury formed during the reaction is determined by the cold vapour method. The detection limit is about 5 ng SOs ". 

The hydride generation and cold vapour methods for the determination of the gaseous hydride forming elements and mercury, and gas chromatographic methods are discussed in Section 6. 

Mercury can be determined in plasma AES by reducing it first to elemental mercury and then transporting the mercury vapour into the plasma. The same reduction methods may be used as for AAS. Commercial hydride generation systems can be adopted to the cold vapour method. The detection limit is about 0.02 mgP ... 

Cold Vapour Method. The capability of the cold vapour technique for the determination of mercury has been examined by using non-dispersive instruments. Mercury is first reduced with tin(ii) chloride to metallic mercury, and the mercury vapour is fed in an argon stream to the excitation cell. A mercury lamp is used for the excitation measurement, and the fluorescence signal is detected by a photomultiplier. A monochromator or filter is required in this technique. 

Mercury AAS with cold vapour method Principle of the method... 

Mercury ions are reduced to metallic mercury with tin(II) chloride. The metallic mercury is transferred into a quartz cuvette with the aid of a current of inert gas and the absorption of the atoms is measured in the beam of an atomic-absorption spectrometer (cold vapour method). 

A) Cold vapour technique. This procedure is strictly confined to the determination of mercury,45 which in the elemental state has an appreciable vapour pressure at room temperature so that gaseous atoms exist without the need for any special treatment. As a method for determining mercury compounds the procedure consists in the reduction of a mercury(II) compound with either... 

MDHS 14 General method for the gravimetric determination of respirable and total dust MDHS 15 Carbon disulphide MDHS 16 Mercury vapour in air Laboratory method using hopcalite adsorbent tubes, and acid dissolution with cold vapour atomic absorption spectrometric analysis MDHS 17 Benzene in air Laboratory method using charcoal adsorbent tubes, solvent desorption and gas chromatography MDHS 18 Tetra alkyl lead compounds in air Continuous on-site monitoring method using PAC Check atomic absorption spirometry... 

Mercury was determined after suitable digestion by the cold vapour atomic absorption method [40]. Lead was determined after digestion by a stable isotope dilution technique [41-43]. Copper, lead, cadmium, nickel, and cobalt were determined by differential pulse polarography following concentration by Chelex 100 ion-exchange resin [44,45], and also by the Freon TF extraction technique [46]. Manganese was determined by flameless atomic absorption spectrometry (FAA). 

This method consists of suspending for a standard time 70 mussels (Mytilus edulis), each of a standard weight, in a plastic coated wire cage 2 m below the surface. Mercury in the mussels was determined by cold vapour atomic... 

Agemian and Chau [55] have described an automated method for the determination of total dissolved mercury in fresh and saline waters by ultraviolet digestion and cold vapour atomic absorption spectroscopy. A flow-through ultraviolet digester is used to carry out photo-oxidation in the automated cold vapour atomic absorption spectrometric system. This removes the chloride interference. Work was carried out to check the ability of the technique to degrade seven particular organomercury compounds. The precision of the method at levels of 0.07 pg/1, 0.28 pg/1, and 0.55 pg/1 Hg was 6.0%, 3.8%, and 1.00%, respectively. The detection limit of the system is 0.02 pg/1. 

Jurka and Carter [50] have described an automated determination of down to O.lpg L 1 mercury in river sediment samples. This method is based on the automated procedure of El-Awady [51] for the determination of total mercury in waters and waste waters in which potassium persulphate and sulphuric acid were used to digest samples for analysis by the cold vapour technique. These workers proved that the use of potassium permanganate as an additional oxidizing agent was unnecessary. 

To implement an easy and automated means for chemical vapour generation procedures (hydride generation for arsenic, selenium, etc., and cold vapour mercury), which allows for a reduction on the interferences caused by first-row transition metals (such as copper and nickel). FI methods may be readily coupled with almost all the atomic-based spectroscopic techniques (including graphite furnace atomisers). 

O. Ertas and H. Tezel, A validated cold vapour-AAS method for determining mercury in human red blood cells, J. Pharm. Biomed. Anal., 36(4), 2004, 893-897. 

G. A. Zachariadis and J. A. Stratis, Optimisation of cold vapour atomic absorption spectrometric determination of mercury with and without amalgamation by subsequent use of complete and fractional factorial designs with univariate and modified simplex methods, J. Anal. At. Speetrom., 6(3), 1991, 239-245. 

Methods based on acid digestions of the soil with 7 M nitric acid [ 136] or sulfuric acid-nitric acid [137] have been described. Released mercury is absorbed in stannous chloride-sulfuric acid-hydroxylamine [ 136] or potassium permanganate-potassium persulfate-hydroxylamine-sodium chloride [137] prior to cold vapour atomic absorption spectrometry. 

Kuwae et al. [138] have described a rapid determination of mercury in soils by high-frequency induction heating (rf) followed by cold vapour atomic absorption spectrometry. The mercury released from the sample is absorbed in stannous chloride-hydroxylamine prior to atomic absorption spectrometry. Recovery of 99.4 to 99.8% mercury was obtained by this method from portions of sample containing between 0.025-0.15 p,g of mercury. 

Nicolson [139] has described a rapid thermal decomposition technique for the atomic absorption determination of mercury in soils. In this method, air is used to sweep mercury vapour from the heated (650-750 °C) sample onto gold foil. In the second stage, heating of the gold foil releases mercury vapour into a cold vapour atomic absorption spectrometer. 

Cold vapour (or flameless) atomic absorption spectrometry is the method of choice for the determination of mercury in soils [136-147]. Ure and Shand [ 141 ]... 

Hon et al. [34] describe a simple piece of equipment for the determination of down to 80 pg/1 of mercury by AAS using a static cold vapour procedure. In this method [35], the sample was digested with the sulfuric acid, a measured portion pipetted into the reduction vessel, and the vessel immediately capped. The reductant, comprising 1% stannous chloride, was introduced. The evolved elemental mercury in the headspace was then introduced into the absorption cell by water displacement. Maximum sensitivity is obtained when the volume of the displaced air is equal to the internal volume of the absorption cell, and the mercury solution is 9 M in sulfuric acid. The peak absorbance at 253.7 nm exhibited a marked decline for hydrochloric acid concentrations above 1.5 M and for nitric acid concentrations above 3 M. The calibration graph obtained for mercury(II) in 9M sulfuric acid is linear from 0 to 17ng/ml, and the sensitivity is 0.08 ng/ml. A windowless absorption cell can also be used with a narrower linear calibration range. 

Notes. The method removes the sulphide interference from the cold-vapour mercury signal. Concentrations of sulphide as high as 20mgr1 S2-(as Na2S) do not interfere with the recovery of inorganic mercury added to distilled water. However, the oxidation technique suffers from chloride interference. If chloride is present in the sample it utilises oxidant and is oxidised to chlorine which interferes with the cold-vapour detection by absorbing radiation at the same wavelength as mercury. 

Flameless AAS methods have so far made little impact in applied geochemistry, except for methods for the element mercury, for which cold-vapour AAS is uniquely effective [2]. A plethora of methods are now in use ranging from simple attachments to standard instruments, to fully portable specific mercury meters of high sensitivity incorporating ingenious methods of background correction [3]. 

Only mercury and the noble gases are commonly encountered as atoms in the gaseous state. This property of mercury is commonly exploited in the cold vapour, reduction-aeration method described elsewhere in this text. Monitors for mercury vapour are commercially available which consist... 

An example is the determination of mercury in foodstuffs using cold vapour atomic absorption spectroscopy. The organic matter in foodstuffs is destroyed by wet oxidation. The mercury in solution is then reduced to the metallic state and released as a vapour in a stream of air. The quantity of mercury vapour in the air stream is measured by cold vapour atomic absorption spectroscopy. This part off the method is called the end determination. Often, as in this example, the end determination is equivalent to the analytical technique for the method. 

Flame atomisation is not necessary for the atomic absorption spectrophotomehy of mercury. The cold vapour technique described here employs a reduction vessel (which may be purchased) to produce mercury vapour the vapour is led to a quartz absorption cell within the atomic absorption inshument. The method is applicable to inorganic and organic mercurial compounds in urine. 

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