Elimination of SAS Interferences in Catalytic Adsorptive Stripping Voltammetric Determination of Cr(VI) by Means of Fumed Silica

In the work the procedure of chromium(VI) determination by catalytic adsorptive stripping voltammetry (CAdSV) with application of fumed silica, is presented. Two variants of the method are proposed: in the first fumed silica is put directly to the electrolytic cell containing tested solution, in the second the silica is shaken with the sample and next centrifuged. The effectiveness of many surface‐active substances removal from synthetic solutions as well as natural water samples, is studied. In the experiments the fumed silica (Sigma‐Aldrich) of the specific surface area in the range 200–390 m² g^?1 was used. Two types of the working electrodes were applied, i.e., hanging mercury drop electrode (HMDE) and cyclic renewable mercury film electrode (Hg(Ag)FE). In the silica presence i) the relative standard deviation (RSD) for 0.1 μg L^?1 Cr(VI) is <2% (HMDE) and <5% (Hg(Ag)FE), n=7, ii) the detection limits estimated deposition time 20 s were respectively 14 ng L^?1 (HMDE) and 22 ng L^?1 (Hg(Ag)FE). The accuracy of the method was tested by studying the recovery of Cr(VI) from spiked natural water samples.     

Simultaneous Determination of Palladium, Platinum and Rhodium by On-Line Column Enrichment and HPLC with 4-Hydroxy-1-Naphthalthiorhodanine as Pre-Column Derivatization Reagents

In this paper, 4-hydroxy-1-naphthalthiorhodanine (HNTR) was synthesized, and a new method for the simultaneous determination of palladium, platinum and rhodium ions as metal-HNTR chelates was developed using rapid column high-performance liquid chromatography combined with on-line enrichment. The palladium, platinum and rhodium ions were pre-column derivatized with HNTR to form colored chelates. The Pb-HNTR, Pt-HNTR and Rh-HNTR chelates could be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [ZORBAX Stable Bound, 4.6 × 10 mm, 1.8 μm] with a buffer solution of 0.05 mol L⁻¹ sodium acetate-acetic acid (pH 4.0) as mobile phase. After enrichment, and by switching the six-ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. Separation of these chelates on the analytical column [ZORBAX Stable Bound, 4.6 × 50 mm, 1.8 μm] was satisfactory with 68% acetonitrile (containing 0.05 mol L⁻¹ of pH 4.0 sodium acetate-acetic acid buffer salt and 0.1% of tritonX-100) as mobile phase. Palladium, platinum and rhodium were separated completely within 2 min. The detection limits (S/N = 3) of palladium, platinum and rhodium are 1.2 ng L⁻¹, 1.5 ng L⁻¹ and 1.8 ng L⁻¹, respectively. This method was applied to the determination of palladium, platinum and rhodium in water, urine and soil samples with good results.     

Microwave-assisted solid phase extraction prior to ICP-MS determination of Pd and Pt in environmental and biological samples

A sensitive and selective microwave-assisted solid phase extraction procedure coupled to inductively coupled plasma-mass spectrometry (ICP-MS) is proposed for palladium (Pd) and platinum (Pt) quantification in environmental and biological samples. Pd and Pt were quantitatively retained on commercial thioureido propyl functionalised silica gel packed inside a home-made glass microcolumn, and later eluted with 0.5% thiourea solution under microwave irradiation, followed by ICP-MS determination. The main variables affecting the procedural stages (i.e., sorption and desorption) and ICP-MS determination were optimised. The best conditions found were: (a) sorption: sample acidity, 1?M HCl; sample flow rate, 3?mL?min^?1; (b) desorption: microwave radiation, power 800?W; eluent concentration, 0.5% thiourea; eluent flow rate, 0.5?mL?min^?1; (c) ICP-MS determination: nebuliser feeding, free aspiration (0.3?mL?min^?1); internal standard, Rh (5?µg?L^?1). Analyte recoveries were higher than 90% and concentration factors up to 90 and 92 were achieved for Pd and Pt, respectively. Depending on the conditions, the methodological limits of detection were down to 0.2?ng?L^?1 for both analytes and repeatability, expressed as RSD%, varied between 1.3 and 11.0%. A method selectivity evaluation showed that most of the ICP-MS interferents were either quantitatively separated or more than 86% eliminated, except for Cu (elimination efficiency around 30%). Finally, the method was successfully used to determine Pd in certified reference materials (i.e. human urine and serum) and Pd and Pt in PM₁₀ airborne particulate matter fractions.     

Amperometric Glucose Biosensor Based on Rhodium Dioxide‐Modified Carbon Ink

An amperometric method for the determination of glucose using a screen printed carbon electrode is reported. The electrode material was bulk modified with rhodium dioxide and the enzyme glucose oxidase immobilized in a Nafion‐film on the electrode surface and investigated for its ability to serve as a detector of glucose in flow injection analysis. The sensor exhibited a linear increase of the amperometric signal with the concentration of glucose in the range of 1–250 mg L^?1 with a detection limit (evaluated as 3σ) of 0.2 mg L^?1 under optimized flow rate of 0.4 mL min^?1 in 0.1 M phosphate buffer (pH 7.5) carrier. At the potential applied (?0.2 V vs. Ag/AgCl), interferences from redox species present in the sample matrix were negligible. The biosensor reported here retained its activity for more than 40 injections or 4 months of storage at 6 °C. The RSD was determined as 1.8% for a glucose concentration of 25 mg L^?1 (n=5) with a typical response time of about 28 s.     

Dispersive Solid-Phase Extraction of Rhodium from Water,Street Dust,and Catalytic Converters Using a Cellulose–Graphite Oxide Composite

A cellulose–graphite oxide composite was synthesized and characterized as an adsorbent for dispersive solid-phase extraction of rhodium from various samples before atomic absorption detection. The pH, adsorbent volume, centrifugation time and rate, eluent concentration, volume and type, adsorption and elution contact time, sample volume, and matrix interferences were optimized. The developed method is simple, rapid, and inexpensive. The tolerance limits for rhodium were 10,000?mg?L^?1 sodium, 25,000?mg?L^?1 potassium, 10,000?mg?L^?1 magnesium, and 20,000?mg?L^?1 calcium. The recovery for rhodium exceeded 95%. Elution was performed with 10?mL of 2.5?mol?L^?1 H₂SO₄. The adsorption and elution contact times were 30 and 60?s, respectively. The detection limit of the method for rhodium was 5.4?µg?L^?1 and the precision as the relative standard deviation was 1.6%. A certified reference material 2556 (used auto catalyst pellets) and fortified samples were analyzed to evaluate the accuracy of the method. The optimized method was used for the preconcentration of rhodium from tap water, well water, wastewater, seawater, catalytic converters, and street dust.     

Simple and rapid surface-enhanced Raman Spectroscopy assay for safranine T and its application in highly sensitive determination of mercury (Ⅱ)

A simple and sensitive surface-enhanced Raman spectroscopy (SERS) method for the detection of safranine T (ST) and Hg²⁺ using silver nanoparticles (AgNPs) as substrate was developed. ST can absorb on the surface of AgNPs through electrostatic interaction, the electromagnetic effect combined with chemical adsorption effect give a notable Raman enhancement for ST. The presence of Hg²⁺ well decreased the absorbed ST molecules on AgNPs, leading to a significant decrease of SERS signals thus enabling to detect Hg²⁺. The determination conditions for SERS, including the amount of AgNPs, the concentration of NaCl, the concentration of HCl, the concentration of ST and the reaction time, were optimised. Under the optimised experimental conditions, good linear responses were obtained for ST and Hg²⁺ in the concentration ranges of 0.01–4.0 μmol L^?1 (3.5–1403.4 ng mL^?1) and 0.01–2.0 μmol L^?1 (2.0–401.2 ng mL^?1), the limit of detection were 3.0 nmol L^?1 (1.1 ng mL^?1) and 2.0 nmol L^?1 (0.4 ng mL^?1), respectively. The present method was subsequently applied to the determination of ST in tomato sauces and Hg²⁺ in environmental waters, the recoveries of ST and Hg²⁺ in spiked samples are 95.5–107.8% and 91.4–110.8 %, respectively.     

Ultrasound‐assisted dispersive liquid–liquid microextraction combined with gas chromatography‐mass spectrometry in negative chemical ionization mode for the determination of polybrominated diphenyl ethers in water

A simple and economical method for the determination of eight polybrominated diphenyl ethers (BDE‐28, 47, 99, 100,153,154,183, and 209) in water was developed. This method involves the use of ultrasound‐assisted dispersive liquid–liquid microextraction combined with GC‐MS in negative chemical ionization mode. Various parameters affecting the extraction efficiency, including the type and volume of extraction and dispersive solvents, salt concentration, extraction time, and ultrasonic time, were investigated. A volume of 1.0 mL of acetone (dispersive solvent) containing 10 μL tetrachloroethylene (extraction solvent) was injected into 5.0 mL of water samples and then emulsified by ultrasound for 2.0 min to produce the cloudy solution. Under the optimal condition, the enrichment factors for the eight PBDEs were varied from 845‐ to 1050‐folds. Good linearity was observed in the range of 1.0–200 ng L^?1 for BDE‐28, 47, 99, and 100; 5.0–200 ng L^?1 for BDE‐153, 154, and 183; and 5.0–500 ng L^?1 for BDE‐209. The RSD values were in the range of 2.5–8.4% (n = 5) and the LODs ranged from 0.40 to 2.15 ng L^?1 (S/N = 3). The developed method was applied for the determination of eight BPDEs in the river and lake water samples, and the mean recoveries at spiking levels of 5.0 and 50.0 ng L^?1 were in the range of 70.6–105.1%.     

The determination of platinum and palladium in rocks and soils by electrothermal atomic absorption spectrometry of extracts of their iodo complexes

The method developed for determining platinum and palladium in rocks and soils is based on extraction of iodo complexes of these elements into methyl isobutyl ketone (MIBK), followed by electrothermal atomic absorption spectrometry of the extracts. The limit of detection is 10 ng g^?1 for platinum and 3 ng g^?1 for palladium. Analysis of the standard noble metal ore PTC-1 with recommended values of 12.7 μg g^?1 for palladium and 3.0 μg g^?1 for platinum gave precisions of 4.4% and 5.6%, respectively, and deviations of 5.0% and 1.2% from the recommended values. The method is applicable to the determination of both elements in a wide variety of rocks and soils.     

Voltametric and Flow Injection Determination of Oxytetracycline Residues in Food Samples Using Carbon Fiber Microelectrodes

A voltammetric method for the determination of the antibiotic oxytetracycline (OTC) in food samples is reported. Carbon fiber microelectrodes (CFMEs), which allow voltammetric measurements to be performed in a small volume (1 mL) of the analyte extract from the samples, are employed. Repeatable electroanalytical responses were obtained with no need of applying cleaning treatments to the CFME. Under the optimized square‐wave conditions, a linear calibration plot for OTC was obtained in the 1.0×10^?6–1.0×10^?4 mol L^?1 range, with a detection limit of 2.9×10^?7 mol L^?1 (150 ng mL^?1) OTC. The determination of OTC by a flow‐injection method with amperometric detection using a homemade flow cell specially designed to work with CFMEs, was also evaluated using pure acetonitrile as the carrier. The SW voltammetric method was applied to the determination of OTC in spiked milk and eggs samples, at 100 ng mL^?1 and 200 ng g^?1 levels, respectively. The procedure involved the extraction of the analyte in ethyl acetate, evaporation of the solvent and reconstitution of the residue in acetonitrile ?5.0×10^?4 mol L^?1 tetrabutylammonium perchlorate medium. Recoveries of 96±8 and 91±8% were obtained for milk and eggs, respectively, by applying the standard additions method.     

Increased Sensitivity Spectrophotometric Flow Analysis Method for Copper Determination in Water Samples

A reverse configured flow injection system was developed for the determination of copper in water samples. In this study, a bathocuproine disulfonic acid copper complexing reagent was used. In the presence of a reducing agent (hydroxylamine), the formation of complex was monitored at 484 nm. The determination range extended from 1 to 40 µg L^?1, with an applicable determination rate of 40 h^?1. The developed method was applied to the determination of copper in water samples (estuarine, river, and drinking water) and showed good accuracy (z-score below 2). The detection limit of 0.7 µg L^?1 copper is consistent with the requirement of the target water samples. The developed method was also used for the comparison of different spectrophotometric flow cells. Alternative flow cells (U, Z shaped, and the liquid waveguide capillary cell) were compared in terms of their sensitivity and response to refractive index changes.     

Simultaneous determination of inorganic arsenic,antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of ⁷⁵As, ⁸²Se, ¹²¹Sb and ¹²⁵Te by ICP-MS for amounts less than 10?µg?L^?1. Internal standards such as ⁷²Ge and ²⁰⁹Bi were successfully used for the suppression of both influence of macro elements Na⁺, K⁺, Ca²⁺, Mg²⁺ or Al³⁺, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH₂, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L^?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L^?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L^?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method.     

Determination of Platinum with Thiosemicarbazide by Catalytic Adsorptive Stripping Voltammetry (AdSV)

This work describes a very sensitive and selective voltammetric procedure for the determination of platinum. Instead of commonly used hydrazine, thiosemicarbazide as a component of supporting electrolyte was applied. The method is based on adsorption of platinum‐thiosemicarbazone complex, formed in situ in voltammetric cell from thiosemicarbazide and formaldehyde, coupled with a hydrogen catalytic reaction at a hanging mercury drop electrode. The linear relation between platinum concentration and height of analytical signal was observed up to 1.5×10^?9 mol L^?1 with the detection limit calculated as 1.5×10^?13 mol L^?1 (3 s of the blank) after 50 s of accumulation time. The effect of various interferences from other ions was studied. Described method was applied for platinum determination in hydroponically cultivated plants after microwave decomposition.     

Sensitive Simultaneous Determination of o-Nitrophenol and p-Nitrophenol in Water by Surfactant-Mediated Differential Pulse Voltammetry

A simple, low-cost and sensitive electroanalytical method was developed for the simultaneous determination of p-nitrophenol and o-nitrophenol isomers in water samples at a glassy carbon electrode (CGE) in the presence of cationic surfactant. The electrochemical behavior of p-nitrophenol and o-nitrophenol was studied by cyclic voltammetry (CV) in 0.1?mol L^?1 acetate/acetic acid buffer (pH 3.70) in the presence and absence of cetylpyridinium bromide. The resolution of overlapped cathodic peaks potentials (E_pc) of isomers was successfully improved in the presence of 100.0?µmol L^?1 cetylpyridinium bromide, thus making this approach ideal for the simultaneous determination of isomers. Under the optimized conditions in 0.05?mol L^?1 HEPES buffer at pH 7.0 using differential pulse voltammetry (DPV) at a scan rate of 45?mV s^?1, pulse amplitude of 220?mV and modulation time of 10?ms, limits of detection 0.59?µmol L^?1 for p-nitrophenol and 1.14?µmol L^?1 for o-nitrophenol were obtained with linear ranges from 2.0 to 60.0?µmol L^?1 and 3.0 to 60.0?µmol L^?1, respectively. The intraday precision was assessed as relative standard deviation (%) for 20.0 and 40.0?µmol L^?1 concentrations were 4.30% and 2.41% for p-nitrophenol and 4.87% and 2.20% for o-nitrophenol, respectively. The developed method was applied for the determination of the isomers in lake water samples. The accuracy was attested by comparison with high-performance liquid chromatography with diode array detection (HPLC-DAD) as a reference analytical technique. Recovery values ranging from 90.3% to 111.8% also attested to the accuracy of method for analysis of real samples.     

Arsenic speciation in water and biota samples at trace levels by ion chromatography inductively coupled plasma-mass spectrometry

A sensitive, reliable, simple and rapid analytical method was developed for the determination of arsenite [As(III)], arsenate [As(V)] and arsenobetaine (AsB) species using ion chromatography combined with inductively coupled plasma-mass spectrometry (IC-ICP-MS). Inorganic and organic arsenic species were separated with an anion exchange column (Dionex AS9) and a 50 mM sodium bicarbonate mobile phase (pH 10) at a flow rate of 1.0 mL min^?1. %RSD values were found to be lower than 5.1% for all arsenic species. The limits of detection (LOD) obtained for As(III), As(V) and AsB were 16.5 ng L^?1, 14.1 ng L^?1 and 6.2 ng L^?1, respectively. The developed analytical method was tested using AsB certified reference material (NMIJ CRM 7901-a), and spring water certified reference material (UME CRM 1201) for accuracy check. This method was applied for the quantitative determination of arsenic species in different water samples and chicken samples as a solid matrix.     

Ultra-trace arsenic and mercury speciation and determination in blood samples by ionic liquid-based dispersive liquid-liquid microextraction combined with flow injection-hydride generation/cold vapor atomic absorption spectroscopy

A simple, fast, and sensitive method for speciation and determination of As (III, V) and Hg (II, R) in human blood samples based on ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) and flow injection hydride generation/cold vapor atomic absorption spectrometry (FI-HG/CV-AAS) has been developed. Tetraethylthiuram disulfide, mixed ionic liquids (hydrophobic and hydrophilic ILs) and acetone were used in the DLLME step as the chelating agent, extraction and dispersive solvents, respectively. Using a microwave assisted-UV system, organic mercury (R-Hg) was converted to Hg(II) and total mercury amount was measured in blood samples by the presented method. Total arsenic content was determined by reducing As(V) to As(III) with potassium iodide and ascorbic acid in a hydrochloric acid solution. Finally, As(V) and R-Hg were determined by mathematically subtracting the As(III) and Hg(II) content from the total arsenic and mercury, respectively. Under optimum conditions, linear range and detection limit (3σ) of 0.1–5.0 µg L^?1 and 0.02 µg L^?1 for As(III) and 0.15–8.50 µg L^?1 and 0.03 µg L^?1 for Hg(II) were achieved, respectively, at low RSD values of < 4% (N = 10). The developed method was successfully applied to determine the ultra-trace amounts of arsenic and mercury species in blood samples; the validation of the method was performed using standard reference materials.     

Solid phase extraction of trace amounts of Pb(II) in opium, heroin, lipstick, plants and water samples using modified magnetite nanoparticles prior to its atomic absorption determination

A new, simple, fast and reliable solid-phase extraction method has been developed for separation/preconcentration of trace amounts of Pb(II) using dithizone/sodium dodecyl sulfate-immobilized on alumina-coated magnetite nanoparticles, and its determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after eluting with 4.0?mol?L^?1 HNO₃. Optimal experimental conditions including pH, sample volume, eluent concentration and volume, and co-existing ions have been studied and established. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of Pb(II) using FAAS technique were 280 (for 560?mL of sample solution), 0.28?ng?mL^?1, 1.4?C70?ng?mL^?1 and 4.6% (for 10?ng?mL^?1, n?=?10), respectively. These analytical parameters using GFAAS technique were 300 (for 600?mL of sample solution), 0.002?ng?mL^?1, 0.006?C13.2?ng?mL^?1 and 3.1% (for 5?ng?mL^?1, n?=?10), respectively. The presented procedure was successfully applied for determination of Pb(II) content in opium, heroin, lipstick, plants and water samples.     

Determination of biocides in different environmental matrices by use of ultra-high-performance liquid chromatography–tandem mass spectrometry

A sensitive and robust method using solid-phase extraction and ultrasonic extraction for preconcentration followed by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS–MS) has been developed for determination of 19 biocides: eight azole fungicides (climbazole, clotrimazole, ketoconazole, miconazole, fluconazole, itraconazole, thiabendazole, and carbendazim), two insect repellents (N,N-diethyl-3-methylbenzamide (DEET), and icaridin (also known as picaridin)), three isothiazolinone antifouling agents (1,2-benzisothiazolinone (BIT), 2-n-octyl-4-isothiazolinone (OIT), and 4,5-dichloro-2-n-octyl-isothiazolinone (DCOIT)), four paraben preservatives (methylparaben, ethylparaben, propylparaben, and butylparaben), and two disinfectants (triclosan and triclocarban) in surface water, wastewater, sediment, sludge, and soil. Recovery of the target compounds from surface water, influent, effluent, sediment, sludge, and soil was mostly in the range 70–120?%, with corresponding method quantification limits ranging from 0.01 to 0.31?ng?L^?1, 0.07 to 7.48?ng?L^?1, 0.01 to 3.90?ng?L^?1, 0.01 to 0.45?ng?g^?1, 0.01 to 6.37?ng?g^?1, and 0.01 to 0.73?ng?g^?1, respectively. Carbendazim, climbazole, clotrimazole, methylparaben, miconazole, triclocarban, and triclosan were detected at low ng?L^?1 (or ng?g^?1) levels in surface water, sediment, and sludge-amended soil. Fifteen target compounds were found in influent samples, at concentrations ranging between 0.4 (thiabendazole) and 372?ng?L^?1 (methylparaben). Fifteen target compounds were found in effluent samples, at concentrations ranging between 0.4 (thiabendazole) and 114?ng?L^?1 (carbendazim). Ten target compounds were found in dewatered sludge samples, at concentrations ranging between 1.1 (DEET) and 887?ng?g^?1 (triclocarban).     

Application of radioisotope XRF for the determination of noble metals in aqueous solutions

Radiometric methods of determination of platium and palladium (0.1 to 5% of Pt and 0.1 to 2% of Pd), gold and indium (0.01 to 1% of Au and 1 to 4 g In/l) and of platinum and rhodium (0.1 to 9% of Pt and 0.05 to 1% of Rh) in aqueous solution has been worked out. A suitable measuring device has been designed and constructed. The methods are based on the measurement of characteristic radiation of the L_α line for gold and platinum and of the K-series for indium, palladium and rhodium, as well as on the measurement of scattered radiation from a²³⁸Pu source. The r.m.s. error of the determination varies from 0.01 to 0.10% of Pt, 0.002 to 0.01% of Au and 0.01 to 0.15% of Pd depending on the concentration. In the case of Rh and In the errors are 0.008% and 0.04 g In/l, respectively.     

ABTS‐Multiwalled Carbon Nanotubes Nanocomposite/Bi Film Electrode for Sensitive Determination of Cd and Pb by Differential Pulse Stripping Voltammetry

A 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonate) diammonium salt (ABTS)‐multiwalled carbon nanotubes (MWCNTs) nanocomposite/Bi film modified glassy carbon (GC) electrode was constructed for the differential pulse stripping voltammetric determination of trace Pb²⁺ and Cd²⁺. This electrode was more sensitive than ABTS‐free Bi/GC and Bi/MWCNTs/GC electrodes. Linear responses were obtained in the range from 0.5 to 35 μg L^?1 for Cd²⁺ and 0.2 to 50 μg L^?1 Pb(II), with detection limits of 0.2 μg L^?1 for Cd²⁺ and 0.1 μg L^?1 for Pb²⁺, respectively. This sensor was applied to the simultaneous detection of Cd²⁺ and Pb²⁺ in water samples with satisfactory recovery.     

Anodic stripping determination of mercury in air with a glassy carbon electrode

A technique for stripping determination of mercury traces in air employing a glassy carbon electrode is described. The sample is passed at 2 liters min^?1 for 2 hr through an absorber containing 0.2 M potassium permanganate and 10% $\text{w}\text{v}$ sulfuric acid (1:1). After reduction with hydroxylamine hydrochloride, the determination is carried out in 0.12 M potassium thiocyanate at pH 2.0 ± 0.2 in the presence of 0.2 ppm of cupric ions. Calibration curves were found to be linear in the range 20 ppb-1 ppm Hg(II) in the cell. The accuracy of the method was tested over simulated samples and it was found to be better than 95%; the relative standard deviation was 5% or less. The limit of detection of mercury in air was approximately 10 μg m^?3.