A comparison of gas-liquid separators for the determination of mercury by cold-vapour sequential injection atomic absorption spectrometry

Four different designs of gas-liquid separators were compared for the determination of mercury by cold-vapour generation atomic absorption spectrometry using the sequential injection technique for mixing the reacting solutions. Two atom cells were also compared, one with windows and one without. The results indicate that the use of a “detuned” nebulizer gave the poorest results. Similar results were obtained with a home-made separator based on a frit and a Perkin-Elmer FIAS Chemifold system with a small dead volume. The use of an atom cell with windows provided the best signals for the determination of mercury.     

Comparison of digestion procedures for the determination of mercury in soils by cold-vapour atomic absorption spectrometry

Five digestion procedures were investigated for the determination of mercury in soils by cold-vapour atomic absorption spectrometry. These methods included three acid leaching procedures in open systems and two acid digestion procedures in closed decomposition vessels. The closed vessels were heated in a conventional laboratory oven or a laboratory microwave oven. In the open systems, digestion with concentrated acids at elevated temperatures led to considerable losses of (organo) mercury compounds, while digestion at ambient temperature gave incomplete oxidation of the sample matrix. To prevent any losses of mercury and to obtain complete oxidation, the use of a closed decomposition system at elevated temperatures appeared to be necessary. The results obtained with these closed systems were in good agreement with those obtained by neutron activation analysis. Heating in a microwave oven appeared to be a considerable improvement over conventional thermal heating.     

The determination of traces of mercury in solid fuels by high-temperature combustion and cold-vapour atomic absorption spectrometry

A high-temperature combustion technique is described for the determination of mercury in coal, coal products including ash, and other samples of environmental interest. The liberated mercury is absorbed in an acidified potassium permanganate solution and determined by cold-vapour atomic absorption spectrometry. The vapour generation assemblage is constructed of standard ground-joint glassware, and is designed to produce non-transient signals suitable for either analog or digital recording devices. Accuracy and precision for 1-g coal samples is 0.02 μg g^-1.     

The accuracy of the vapour-injection calibration method for the determination of mercury by amalgamation/cold-vapour atomic absorption spectrometry

A vapour-injection method is described for the calibration of mercury determinations. Its accuracy depends mainly on the temperature of the mercury-saturated air, which must be lower than the ambient temperature. By preconditioning the syringe, initial irreproducible measurements caused by sorption are avoided. Under optimal conditions, the precision of the injection in the range 1–100 ng of mercury is generally better than 1%.     

Indirect determination of perchlorate by atomic absorption spectrometry

A liquid-liquid extraction and determination of perchlorate by atomic absorption spectrometry is described. The method involves extraction of perchlorate with the Schiffs base complex [Co(BPTC)₂]⁺, where BPTC = 2-benzoyl pyridine thiosemicarbazone, in methyl isobutyl ketone in acidic medium and subsequent analysis of cobalt in flame AAS, hence indirectly for perchlorate. The extraction efficiency is 98%. The calibration graph was found to be linear for 1.0–11.4 g ClO ₄ ^– per ml of solvent, and the limit of detection is 30 ng ml^–1. The present method is free from interference of large number of foreign ions. The method has been applied for determination of perchlorate in human blood serum samples spiked with perchlorate, urine and commercial potassium chlorate sample.     

Interfering effects on the determination of low concentrations of mercury in geological materials by cold-vapour atomic absorption spectrometry

Gold, platinum, selenium and tellurium interfere with the determination of mercury in geological materials by cold-vapour atomic absorption spectrometry. These elements can be reduced together with mercury by tin(II) chloride, and surface adsorption and amalgamation then hinder the vaporization of mercury from acidic media. In strongly alkaline media, the interfering effect does not appear even when considerable concentrations of these elements are present.     

The misbehaviour of mercury(I) ions in cold-vapour atomic absorption spectrometry

The behaviour of mercury(I) ion in the cold-vapour atomic absorption spectrometry under nonreducing conditions is discussed. The signal obtained corresponds to about 35% of total mercury present. Under the same conditions, the same quantity of Hg²⁺ is found by dithizone spectrophotometry. Thus the cold-vapour signal is due entirely to disproportionation of mercury(I), which is not inhibited by chloride at mercury concentrations less than 120 μg l^?1. The cold-vapour signal si pH-dependent and at low hydrogen ion concentration, approaches the value expected from complete disproportionation.     

A rapid,simple method for the determination of total mercury in fish and hair by cold-vapour atomic absorption spectrometry

Fuming nitric acid and acidified potassium permanganate are used to pre-digest fish or hair samples in Pyrex culture tubes. Cold-vapour atomic absorption spectrometry is used to detect the elemental mercury which is generated by reduction in a syringe. The absolute detection limit of the method is 0.66 ng Hg, and at levels of 0.14 and 0.60 parts per million (ppm) the standard deviations are ± 0.009 and ±0.008 ppm, respectively. One person can handle batches of 50–100 samples per day including standards and blanks.     

Breakdown of organic mercury compounds by hydrochloric acid—permanganate or bromine monochloride solution for the determination of mercury by cold-vapour atomic absorption spectrometry

Hydrochloric acid—potassium permanganate and bromine monochloride are examined for the decomposition of methylmercury(II) chloride, Ceresan, phenylmercury(II) borate and thiomersal added to waters. Both procedures give quantitative recovery of mercury. Bromine monochloride has many advantages: blanks are low, the limit of detection (3σ) is 0.06 μg Hg l^?1, routine work is simplified because only two reagents are needed and the reaction time is 5–10 min. The reagent also acts as a preservative. Common contaminants (chloride, bromide, sulphide, alcohols, benzene) do not interfere.     

Use of additives in pyrolytic separation of mercury from industrial samples for cold-vapour atomic absorption spectrometry

The role of filter materials and additives in the thermal volatilization of mercury from industrial samples (copper concentrates, lead and zinc oxides and kaolin) is studied. Alumina is shown to be most effective but the calcination temperature and the sodium content of the additive can influence its effectiveness because of changes in surface properties.     

The use of alkaline permanganate in the preparation of biological materials for the determination of mercury by atomic absorption spectrometry

Biological materials when treated with 1.5 M potassium hydroxide, rapidly disintegrate, and become dispersed in the aqueous phase. Addition of potassium permanganate causes rapid and almost complete sample oxidation. Dissolution is completed by addition of sulphuric acid, and excess of oxidant is reduced with oxalic acid. The homogenization step allows representative subsampling. The procedure is applicable to human hair, fingernails, urine, fish products, plant material, rat fur, blood and liver.     

The determination of mercury by non-flame atomic absorption and fluorescence spectrometry.

An isotopic dilution method has been developed for the determination of ²²⁶Ra and ²²⁸Ra in sea water and sediments with ²²³Ra as a yield tracer. An alternative procedure which obviates the need for ²²³Ra is demonstrated for sediments by the assay of ²²⁴Ra and ²²⁸Th which occur naturally in sediments. In addition, a direct method for β-counting ²²⁸Ra–²²⁸Ac is proposed. Radium, polonium, thorium and uranium isotopes and ²¹⁰Pb are coprecipitated from sea water with aluminum phosphate carrier. The radium and lead-210 are coprecipitated with lead nitrate in sediment leachings. All radium procedures utilize identical chemical isolation and the cathodic electrodeposition of radium. Subsequently, the α-radiation emitted by ²²⁶Ra, ²²³Ra and ²²⁴Ra is determined by pulse-height analysis: the ²²⁸Ra-²²⁸Ac and ²¹⁰Pb-²¹⁰Bi are measured by low background anticoincidence β-counting techniques. This method was used for samples containing 10^-11–0.5 · 10^-12 g of ²²⁶Ra and 10^-13–10^-15 g of ²²⁸Ra and gave a precision of 3–6% and 5–10% respectively, even though radium levels an order of magnitude less can be measured. The ²²⁶Ra method is applicable to all environmental samples, whereas ²²⁸Ra determinations are limited to applications where the ${}^{228}\text{Ra}{}^{226}\text{Ra}$ activity ratio is greater than 0.1. This method is especially attractive for studies of parent-daughter disequilibria.     

The rapid determination of water of hydration in magnesium perchlorate desiccant

The efficiency of “anhydrous” magnesium perchlorate as a desiccant, and its capacity in absorption of water vapour, ammonia gas, alcohol vapour, and other highly volatile organic vapours, is dependent upon the extent to which its water of hydration is removed in preparation for commercial distribution. American Chemical Society “Reagent Chemicals” specifications call for not more than 10% water as a maximum tolerance. The product is, by intent, not ordinarily manufactured for distribution in the completely dehydrated form and regularly contains approximately 5% unremoved water of hydration. This is the regular practice to insure a less friable granular structure than would result from complete dehydration. The method here described for the determination of its water content is rapid in application, sufficiently accurate for all practical demand, and requires very simple apparatus and manipulative details.     

A low consumption air-segmented sequential injection vapor generation system for the determination of mercury by atomic absorption spectrometry

A sequential injection system for the determination of mercury by vapor generation atomic absorption spectrometry (VGAAS) using tetrahydoborate reductant was developed, characterized by prevention of sample and reagent mixing in the holding coil using small air segments and initiation of the vapor generation in a flow-through gas-liquid separator. Extremely small volumes of reductant of 15-30 mul (0.2-1.0% NaBH(4)) and sample acidity as low as 0.05 mol l(-1) HCl were sufficient for achieving performance similar to flow injection (FI) VGAAS systems. A sample throughput of 90 h(-1) was achieved with 400 mul samples with a precision of 2.0% RSD at 10 mug l(-1)Hg, and a detection limit of 0.1 mug l(-1) (3sigma). Reagent consumption was reduced by a factor of 25 in comparison to the FI-VGAAS system. Good agreement with the certified value was obtained for the determination of mercury in seawater in a standard reference sample.     

On-line microwave sample pretreatment for the determination of mercury in blood by flow injection cold vapor atomic absorption spectrometry

A method for on-line treatment of whole blood in a microwave oven and determination of mercury by flow injection cold vapor atomic absorption spectrometry was developed. After dilution of the whole blood and addition of oxidant, all further treatment and measurement were performed automatically, on-line. Recoveries of five mercury compounds were complete. Good agreement between measured and recommended values of mercury in whole blood reference materials was obtained. Measured mercury values also agreed with results from other accepted methods. Sample throughput was about 45 measurements/hr. Detection limit (3s) in diluted sample was 0.1 μg/l corresponding to 1μg/l Hg in whole blood. The RSD value at 0.5 μg/l Hg in the diluted sample was 6–7% (11 measurements and 0.5 ml sample volume). Mercury concentrations between 1 and 150 μg/l in whole blood can be measured using this method. For three replicate measurements, 0.5 ml of whole blood is required.     

Trace determination of mercury in biological materials by flameless atomic absorption spectrometry

A new rapid wet-ashing procedure for biological material is described. The samples are boiled for 5–10 min in a mixture of nitric and hydrobromic acid under reflux. Mercury is then determined by the flameless cold-vapour, atomic absorption technique and complete release is shown to occur even when the fat present is not fully decomposed. The results are discussed with regard to the normal bromine and iodine content of marine samples. The enhancement obtained with bromine can easily be compensated by digesting the standards. Iodine, however, reduces the peak heights and the content of this element must be judged separately for samples other than fish, which can always be safely analysed without interference.     

The determination of mercury in soils and related materials by colc-vapour atomic absorption spectrometry

A method for the determination of mercury in soils and related materials, by the cold-vapour, reduction-aeration absorption technique, is described. The mercury in the reduced sample solution is partitioned, by agitation, between the liquid phase and a fixed volume of air which is then blown through an absorption cell for measurement. Three preparative methods were developed, two of which use acid digestion and wet oxidation and the other direct oxidation in an oxygenflask combustion technique. Comparative analysis of natural samples by the three methods was used to validate the techniques developed, since no authenticated reference samples were available. For 1-g samples, the analytical range was 0.01–0.5 p.p.m.     

Determination of nanomole quantities of lower aldehydes by cold-vapour atomic absorption spectrometry

A method is described for the determination of 10–100 nmole of methanal and 20–150 nmole of ethanal and propanal. The method is based on the oxidation of aldehydes to the corresponding acids by mercuric ion which in turn is reduced to elemental mercury, followed by cold-vapour atomic absorption spectrometry. Calibration plots were constructed between the concentration of each aldehyde and absorbance, while the calibration from the conventional cold vapour procedure was used for total aldehydes determination. The method is selective and can be used for aldehyde determination in the presence of ketones, acetals, alcohols, acids, esters, ethers, organic chlorides and epoxides. This simple method is characterised by 98–102% recoveries and standard deviations of 3%.