Use of zwitterionic micelles in the eluent II: a new approach to ion chromatographic analysis of inorganic cations in biological fluids with direct sample injection

A new ion chromatographic (IC) technique has been developed for the determination of inorganic cations in biological fluids with direct sample injection. This involved the use of a mixed zwitterionic-micelle/electrolyte solution as an eluent. The proteins in the sample became bound to the zwitterionic micelles in the eluent and were thus eliminated from the column. The cations were separated by cation exchange. This method is ideal for the on-line, simultaneous determination of common inorganic cations (Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺) in urine and serum samples. Such an application was demonstrated experimentally. Non-suppressed conductivity was used for analyte detection. The detection limits obtained using this IC system were 2.94, 5.22, 34.9, 32.6, and 56.7 μg/L for Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺, respectively.     

Preparation of a hybrid monolithic stationary phase with allylsulfonate for the rapid and simultaneous separation of cations in capillary ion chromatography

A hybrid monolithic column with sulfonate functionality was successfully prepared for the simultaneous separation of common inorganic cations in ion‐exchange chromatographic mode through a simple and easy single‐step preparation method. The strong cation‐exchange moieties were provided directly from allylsulfonate, which worked as an organic monomer in the single‐step reaction. Inorganic cations (Li⁺, Na⁺, K⁺, NH₄⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, and Sr²⁺) were separated satisfactorily by using CuSO₄ as the eluent with indirect UV detection. The allysulfonate hybrid monolith showed a better performance in terms of speed and pressure drop than the capillary packed column. The number of theoretical plates achieved was 19 017 plates/m (in the case of NH₄⁺ as the analyte). The relative standard deviations (n = 6) of both retention time and peak height were less than 1.96% for all the analyte cations. The allysulfonate hybrid monolithic column was successfully applied for the rapid and simultaneous separation of inorganic cations in groundwater and the effluent of onsite domestic wastewater treatment system.     

Capillary ion electrophoresis-capacitively coupled contactless conductivity detection of inorganic cations in human saliva on a polyvinyl alcohol-coated capillary

Capillary ion electrophoresis–capacitively coupled contactless conductivity detection (CIE-C4D) with a polyvinyl alcohol chemically coated capillary (PVA capillary) was used to analyze inorganic cations (Na⁺, K⁺, NH₄⁺, Mg²⁺, and Ca²⁺) commonly found in human saliva. The PVA capillary, which was made by our laboratory, minimized electro-osmotic flow in the wide pH range of the background electrolyte (BGE), and the PVA layer adsorbed to capillary wall did not affect the conductimetric background level. In this study, we determined an optimized BGE of 30 mM lactic acid/histidine plus 3 mM 18-crown-6 for the CIE-C4D system using the PVA capillary, which could simultaneously improve the separation of Mg²⁺ and Ca²⁺ from Na⁺ and that of K⁺ from NH₄⁺. This system obtained highly reproducible separation of cations in human saliva samples within 8 min at 20 kV without deprotonation. The quantifiability of cations in human saliva samples on the CIE-C4D system was demonstrated through identification by ion chromatography with satisfactory results.     

On‐site sampling of inorganic contamination on the metal surface and analysis with capillary electrophoresis

Pipes are the primary structural elements used for transporting fluid in various industries. The most common damage mechanism is corrosion, which occurs in pipes surface of turbine. The corrosive compounds for pipes are inorganic ion (Na⁺, Cl^?, NH₄⁺, NO₃^?, etc.) and grinding oil. For rapid and quantitative detection of inorganic ions on site, more reliable and reproducible analytical methods are demanded. A highly efficient solid–liquid sampling collection system is introduced in this work. Papering on the sample surface, inorganic cations and anions were simultaneously collected and analyzed by capillary electrophoresis with indirect ultraviolet detection. As a result, five cations (Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺) and three anions (Cl^?, NO₃^?, SO₄^2?) were completely separated. The efficiency of the sampling and ability of capillary electrophoresis analysis were presented by the determination of trace‐level (mg/m²) contaminants. The recoveries of cations and anions on the paper from metal surface were between 86.6 and 107.2%, and the relative standard deviations were less than 12.85%.     

Use of Ionic liquids as additives in ion exchange chromatography for the analysis of cations

The behavior of acids (citric acid, nitric acid, oxalic acid, tartaric acid) as a mobile phase and imidazolium ionic liquids (the bromides, tetrafluoroborates and hexafluorophosphates of 1‐ethyl, 1‐butyl, and 1‐hexyl‐3‐methylimidazolium) as additives in ion exchange chromatography for cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) separation were studied. The results showed that nitric acid and 1‐hexyl‐3‐methyl‐imidazolium hexafluorophosphate offered the most interesting features in the separation of cations, such as lower retention time and better resolution. The selected optimal conditions were achieved by adding 0.10 mM 1‐hexyl‐3‐methyl‐imidazolium hexafluorophosphate in 4.0 mM HNO₃ mobile phase for the separation of four cations with the flow rate of 0.9 mL/min at room temperature (25°C). The linear regression equations of Na⁺, K⁺, Mg²⁺, Ca²⁺ were S  = 4.4763c  + 0.0209, S  = 3.8903c  – 0.0087, S  = 6.3974c  – 0.0173, and S  = 7.601c  – 0.0339 and the limits of detection of Na⁺, K⁺, Mg²⁺, Ca²⁺ were 0.296, 4.98, 0.0970, and 1.22 μg/L, respectively. In this work, four cations in samples were successfully detected.     

Electromembrane extraction and capillary electrophoresis with capacitively coupled contactless conductivity detection: Multi‐extraction capabilities to analyses trace metals from saline samples

Simultaneous electromembrane extraction (EME) of six trace metal cations (Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺, Pb²⁺, Cd²⁺) from saline samples was investigated. CE with capacitively coupled contactless conductivity detection (C⁴D) was used to determine the metals in acceptor solutions due to its excellent compatibility with the minute volumes of acceptor solutions. Bis(2‐ethylhexyl)phosphate (DEHPA) was selected as a suitable nonselective modifier for EME transport of target metal cations. Both, the individual effect of each major inorganic cation (Na⁺, K⁺, Ca²⁺, Mg²⁺) and their synergistic effect on EME of the trace metal cations were evaluated. In both cases, a decrease in extraction efficiency was observed when major inorganic cations were present in the sample. This effect was more significant for Ca²⁺ and Mg²⁺. The system was optimized for simultaneous extractions of the six target metals from saline samples (50 mM Na⁺, 5 mM Mg²⁺, 1 mM K⁺, and 1 mM Ca²⁺) and following EME conditions were applied. Organic phase consisted of 1‐nonanol containing 1% (v/v) DEHPA, acceptor solution was 1 M acetic acid (HAc) and sample pH was adjusted to 5. Sample was stirred at 750 rpm and EMEs were carried out at extraction potential of 10 V for 20 min. The method presented a repeatability between 8 and 21.8% (n = 5), good linearity in 0.5–10 μM concentration range (R² = 0.987‐0.999) and LOD better than 2.6 nM. Applicability of the EME–CE–C⁴D method to the analyses of metal cations in drinking water, seawater, and urine samples was also demonstrated.     

Portable,lightweight, low power,ion chromatographic system with open tubular capillary columns

Basic operation principles of a lightweight, low power, low cost, portable ion chromatograph utilizing open tubular ion chromatography in capillary columns coated with multi-layer polymeric stationary phases are demonstrated. A minimalistic configuration of a portable IC instrument was developed that does not require any chromatographic eluent delivery system, nor sample injection device as it uses gravity-based eluent flow and hydrodynamic sample injection adopted from capillary electrophoresis. As a detection device, an inexpensive commercially available capacitance sensor is used that has been shown to be a suitable substitute for contactless conductivity detection in capillary separation systems. The built-in temperature sensor allows for baseline drift correction typically encountered in conductivity/capacitance measurements without thermostating device. The whole instrument does not require any power supply for its operation, except the detection and data acquisition part that is provided by a USB port of a Netbook computer. It is extremely lightweight, its total weight including the Netbook computer is less than 2.5 kg and it can be continuously operated for more than 8 h. Several parameters of the instrument, such as detection cell design, eluent delivery systems and data treatment were optimized as well as the composition of eluent for non-suppressed ion chromatographic analysis of common inorganic cations (Na⁺, NH₄⁺, K⁺, Cs⁺, Ca²⁺, Mg²⁺, transition metals). Low conductivity eluents based on weakly complexing organic acids such as tartaric, oxalic or pyridine-2,6-dicarboxylic acids were used with contactless capacitance detection for simultaneous separation of mono- and divalent cations. Separation of Na⁺ and NH₄⁺ cations was optimized by addition of 18-crown-6 to the eluent. The best separation of 6 metal cations commonly present in various environmental samples was accomplished in less than 30 min using a 1.75 mM pyridine-2,6-dicarboxylic acid and 3 mM 18-crown-6 eluent with excellent repeatability (below 2%) and detection limits in the low micromolar range. The analysis of field samples is demonstrated; the concentrations of common inorganic cations in river water, mineral water and snow samples were determined.     

Affinity capillary electrophoresis employed for determination of stability constants of antamanide complexes with univalent and divalent cations in methanol

Affinity capillary electrophoresis (ACE) and pressure‐assisted ACE were employed to study the noncovalent molecular interactions of antamanide (AA), cyclic decapeptide from the deadly poisonous fungus Amanita phalloides, with univalent (Li⁺, Na⁺, K⁺, and NH₄⁺) and divalent (Mg²⁺ and Ca²⁺) cations in methanol. The strength of these interactions was quantified by the apparent stability constants of the appropriate AA‐cation complexes. The stability constants were calculated using the nonlinear regression analysis of the dependence of the effective electrophoretic mobility of AA on the concentration of the above ions in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pH_MeOH 7.8, containing 0–50 mM concentrations of the above ions added in the form of chlorides). Prior to stability constant calculation, the AA effective mobilities measured at actual temperature inside the capillary and at variable ionic strength of the BGEs were corrected to the values corresponding to the reference temperature of 25°C and to the constant ionic strength of 10 mM. From the above ions, sodium cation interacted with AA moderately strong with the stability constant 362 ± 16 L/mol. K⁺, Mg²⁺, and Ca²⁺ cations formed with AA weak complexes with stability constants in the range 37–31 L/mol decreasing in the order K⁺ > Ca²⁺ > Mg²⁺. No interactions were observed between AA and small Li⁺ and large NH₄⁺ cations.     

Development of a fast capillary electrophoresis method to determine inorganic cations in biodiesel samples

The aim of this study was to develop a fast capillary electrophoresis method for the determination of inorganic cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) in biodiesel samples, using barium (Ba²⁺) as the internal standard. The running electrolyte was optimized through effective mobility curves in order to select the co-ion and Peakmaster software was used to determine electromigration dispersion and buffer capacity. The optimum background electrolyte was composed of 10 mmol L⁻¹ imidazole and 40 mmol L⁻¹ of acetic acid. Separation was conducted in a fused-silica capillary (32 cm total length and 23.5 cm effective length, 50 μm I.D.), with indirect UV detection at 214 nm. The migration time was only 36 s. In order to obtain the optimized conditions for extraction, a fractional factorial experimental design was used. The variables investigated were biodiesel mass, pH, extractant volume, agitation and sonication time. The optimum conditions were: biodiesel mass of 200 mg, extractant volume of 200 μL and agitation of 20 min. The method is characterized by good linearity in the concentration range of 0.5-20 mg kg⁻¹ (r > 0.999), limit of detection was equal to 0.3 mg kg⁻¹, inter-day precision was equal to 1.88% and recovery in the range of 88.0-120%. The developed method was successfully applied to the determination of cations in biodiesel samples.     

Precise analysis of thyroxine enantiomers in pharmaceutical formulation by mobility difference based on cyclodextrin

Identification and determination of chiral pharmaceutical residues is still a challenging analytical puzzle. In this work, a simple, rapid, and effective method for chiral D/L-tetraiodothyronine (T4) separation and quantitative was developed based on host–guest recognition using ion mobility spectrometry-mass spectrometry (IMS-MS). The D/L-T4 enantiomers were mobility separated by their diastereomeric complexes through mixing with cyclodextrin (CD) and metal ions. D/L-T4 was first separated by complexing with host molecule (α-, β-, γ-CD), observing weak peak-to-peak resolution (R_p-p) by the formed binary complex [CD + D/L-T4-H]⁺, and the R_p-p decreased with the CD size increasing. However, the separation effect of D/L-T4 was much improved with the addition of divalent metal ions (G²⁺) by the formed ternary complex [CD + D/L-T4 + G]²⁺. In comparison, α-CD related complexes can possess the best separation effect for D/L-T4 in most cases. Considering the high selectivity, non-toxic, and chemically stable of β-CD, [β-CD + D/L-T4 + Ca]²⁺ was selected for D/L-T4 analysis (R_P-P = 0.764). Whereafter, chemical theoretical conformations for [β-CD + D/L-T4 + H]⁺ and [β-CD + D/L-T4 + Ca]²⁺ were optimized, discovering similar micro-interaction modes between [β-CD + D-T4 + H]⁺ and [β-CD + L-T4 + H]⁺; while with the addition of Ca²⁺, significantly different interaction modes were observed between [β-CD + D-T4 + Ca]²⁺ and [β-CD + L-T4 + Ca]²⁺. And theoretical collision cross section (CCS) trends for the complexes were consistent with that of the experimental results. Additionally, calibration curves were linear within 1.00 to 10⁴ ng mL^?1 with coefficient (R² > 0.99), gaining the limit of detection (LODs) calculation of 0.11 ng mL^?1, and the detection range between D-T4 and L-T4 of 45.6:1 to 1:59.8. Finally, the method was applied for D/L-T4 detection in Levothyroxine tablets, the detection content has good consistency on drug labeling. Because the proposed method exhibited good analytical performance in terms of speed, selectivity, sensitivity, and reproducibility of the measurements, that can be a promising strategy for effective D/L-T4 detection in pharmaceutical industries or other practical samples.     

Ion-exchange chromatography using vanadyl and vandate salts as mobile phases with indirect detection

Summary Vanadyl sulfate, VOSO₄, was characterized as the mobile phase for the ion exchange separation of Li⁺, Na⁺, NH ₄ ⁺ , and K⁺ using indirect photometric detection at 254 nm. Detection limits ranged from 0.2 ppm for Li⁺ to 1 ppm for K⁺. Indirect electrochemical detection of these separated cations by reduction of VO (II) to V³⁺ was compared to spectrophotometric detection. The potential of the vanadate species, HVO ₄ ^2– , for the separation of F^–, Cl^–, and SO ₄ ^2– , with indirect photometric detection was also demonstrated.     

A portable lab‐on‐a‐chip instrument based on MCE with dual top–bottom capacitive coupled contactless conductivity detector in replaceable cell cartridge

A new design for a compact portable lab‐on‐a‐chip instrument based on MCE and dual capacitively coupled contactless conductivity detection (dC⁴D) is described. The instrument is battery powered with total dimension of 14 × 25 × 8 cm³ (w × l × h), and weighs 1.2 kg. The device consists of a front electrophoresis compartment which has the chip holder and the chip, the associated high‐voltage electrodes for electrophoresis injection and separation and the detector. The detection cell is integrated into the device housing with an exchangeable plug‐and‐play cartridge format. The design of the dC⁴D cell has been optimized for maximum performance. The cartridge includes the top–bottom excitation and pick up electrodes incorporated into the cell and connected to push‐pull self‐latching pins that are insulated with plastic. The metal frame of the cartridge is grounded completely to eliminate electronic interferences. The cartridge is designed to clamp a thin fluidic chip at the detection point. The cartridges are replaceable whereby different cartridges have different detection electrode configurations to employ according to the sensitivity or resolution needed in the specific analytical application. The second compartment consists of all the electronics, data acquisition card, high‐voltage modules of up to ±5 kV both polarity, and batteries for 10 h of operation. The improved detector performance is illustrated by the electrophoresis analysis of six cations (NH₄⁺, K⁺, Ca²⁺, Na⁺, Mg²⁺, Li⁺) with a detection limit of approximately 5 μM and the analysis of the anions (Br^?, Cl^?, NO₂^?, NO₃^?, SO₄^2?, F^?) with a detection limit of about 3 μM. Analytical capabilities of the instrument for food and medical applications were evaluated by simultaneous detection of organic and inorganic acids in fruit juice and inorganic cations and anions in rabbit blood samples and human urine samples are also demonstrated.     

Monolithic ODS-silica gel column for determination of hydrogen, sodium, ammonium and potassium in acid rain by lon chromatography

Summary A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was firstly used to separate monovalent cations simultaneously including H⁺, Na⁺, NH₄ ⁺ and K⁺ by ion-chromatography (IC). Using an acidified 60 mM LiCl solution (pH 3.95, containing 0.10 mM Li-DS) as eluent, these monovalent cations were separated well in the order of Na⁺<NH₄ ⁺<K⁺<H⁺ within 3 min at a flow rate of 2.0 mL min⁻¹. The detection limits of these cations by this method with conductivity detection were 20.0 μM for Na⁺, 12.0 μM for NH₄ ⁺, 9.84 μM for K⁺ and 6.20 μM for H⁺. Acid rain water samples with a pH value less than 5.00 could be analyzed directly with this IC system.     

Determination of hydrogen ion by ion chromatography (IC) with sulfonated cation-exchange resin as the stationary phase and aqueous EDTA (ethylenediamine-N,N,N′,N′-tetraacetic acid) solution as the mobile phase

An ion chromatographic (IC) method has been developed for determination of hydrogen ion (H⁺). It is based on the use of sulfonated cation-exchange resin as stationary phase, aqueous ethylenediamine-N,N,N′,N′-tetraacetic acid (dipotassium salt, EDTA-2K, written as K₂H₂Y) solution as mobile phase, and conductivity for detection. H⁺ was separated mainly by cation-exchange, but its elution was accelerated by the presence of EDTA. The order of elution for the model cations was H⁺ > Li⁺ > Na⁺ > NH₄ ⁺ > Ca²⁺ > > Mg²⁺. A sharp and highly symmetrical peak was obtained for H⁺ and this was attributed to the capacity of H₂Y₂ ^2– to receive and bind H⁺. H⁺ was detected conductiometrically and detector response (reduction in conductivity as a result of H⁺+H₂Y^2–→H₃Y^–) was linearly proportional to the concentration of H⁺ in the sample. The detection limit for H⁺ with this IC system was better than 4.7 μmol L^–1. A significant advantage of this method was the ability to separate and determine, in one step, H⁺ and other cations. The successful determination of H⁺ and other cation species in real acid-rain samples demonstrated the usefulness of this method.     

Evaluation of a microwave-assisted extraction technique for determination of water-soluble inorganic species in urban airborne particulate matter

A simple and rapid microwave-assisted extraction (MAE) technique has been developed for the determination of water-soluble inorganic species (cations: Na⁺, NH₄⁺, K⁺, Ca²⁺ and Mg²⁺ and anions: F^–, Cl^–, NO₃^–, PO₄^3– and SO₄^2–) in airborne particulate matter. The analytes were extracted under different treatment conditions such as microwave power and extraction time. They were quantified using ion chromatography. The observed concentrations and recovery yields obtained under different conditions were compared. The results of a comparison between this MAE and sonication using NIST SRM 1648 are also given in this paper. The optimized MAE technique gave results in good agreement with the values obtained by the sonication. For some ions, for example Mg²⁺ and K⁺, recovery was low with both techniques. The results demonstrated that the optimized MAE is fast and efficient compared with conventional ultrasonic extraction. Urban airborne particles were collected and subjected to the MAE followed by the IC analysis to determine the relative proportions of different water-soluble inorganic species. These results are briefly discussed.     

Cations Insertion in Molybdenum Cluster Compounds: Electronic Structure and Electrochemical Study Using Cavity Microelectrode

Owing to the high lability of cations in the three-dimensional framework of K_1+x Mo₁₂S₁₄ (0 ≤ x ≤ 1.6), first-principles calculations and electrochemical methods have been carried out to study the insertion of cations in the empty channels of this compound. The cavity microelectrode that is a suitable electrode for powder material analysis has been used in voltammetric experiments. Results obtained for Li⁺, Na⁺, Rb⁺, K⁺, Cs⁺ and NH₄ ⁺ cations are presented and discussed.     

The Application of Cryptand 22 as a Bifunctional Stationary Phase for Ion Chromatography

Poly (styrene/divinyl benzene) with cryptand 22 as an anchoring group was synthesized and applied as a bifunctional packing material for the separation of both cations and anions. At pH < 2, the resin can be protonated and applied as an anion exchanger for the separation of anions; with water as eluent, inorganic anions such as F^?, Cl^?, Br^?, NO₃^?”, I^? were well separated. After deprotonation at pH> 10, the resin became a cation exchanger and successfully separated alkali metal ions such as Li⁺, K⁺ and Cs⁺ with methanol as eluent. The effects of solvents, flow rate and temperature on the separation of various ions were also investigated.     

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high‐voltage

An improved method for the concurrent determination and separation of cations and anions by microchip electrophoresis with capacitively coupled contactless conductivity detection (ME‐C⁴D) is described. Two kinds of microchip structures were designed. The first microchip has a long bent separation channel. And for the defects of the first microchip, the second microchip with a Y‐type separation channel has been proposed. The background electrolyte (BGE) composed of 20 mm His/MES and 0.01 mm CTAB was optimized for inhibiting the electroosmotic flow (EOF). Due to the low electroosmotic flow, the cations and anions migrate in opposite directions and can be separated from each other. With the precisely controlled high‐voltage, cations and anions can be migrated in microchannels according to our requirements and sequentially detected by a C⁴D detector built in‐house. Samples containing K⁺, Na⁺, Li⁺, Cl⁻, F⁻ and PO₄³⁻ were analyzed simultaneously in a single run (within 140 s) by both methods. The reproducibility obtained by both methods remained below 5% for migration time and within 3.5–9.1% for peak areas. The proposed concurrent determination methods are inexpensive, simple, fast, ease of operation, high degree of integration.     

Tris(2-ethylhexyl)phosphine oxide as an effective solvent mediator for constructing a serotonin-selective membrane electrode

A series of solvent mediators containing a phosphoryl (PO) group, such as tris(2-ethylhexyl)phosphate, bis(2-ethylhexyl) 2-ethylhexylphosphonate, 2-ethylhexyl bis(2-ethylhexyl)phosphinate, and tris(2-ethylhexyl)phosphine oxide, were used to construct serotonin-selective membrane electrodes. We found that replacing the alkoxy groups attached to phosphorus atoms in PO groups with alkyl groups strengthened the response of the electrode to serotonin, suppressing remarkably interference from inorganic cations, such as Na⁺. Thus, an electrode combining tris(2-ethylhexyl)phosphine oxide with an ion-exchanger, sodium tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate, gave a detection limit of 9 × 10⁻⁶ M with a slope of 55.2 mV per concentration decade in physiological saline containing 150 mM NaCl and 10 mM NaH₂PO₄/Na₂HPO₄ (pH 7.4). This is the best detection limit of any serotonin-selective electrode developed to date. The selectivity of this electrode for serotonin was over 10³ times that for inorganic cations, such as Na⁺ and K⁺, and lipophilic quaternary ammonium ions, such as acetylcholine and (C₂H₅)₄N⁺. Using the electrode, we measured the amount of serotonin released from platelets and found that the results agreed well with those obtained by a conventional fluorimetric assay of serotonin.     

Determination of inorganic and total mercury by vapor generation atomic absorption spectrometry using different temperatures of the measurement cell

A simple and inexpensive laboratory-built flow injection vapor generation system coupled to atomic absorption spectrometry (FI-VG AAS) for inorganic and total mercury determination has been developed. It is based on the vapor generation of total mercury and a selective detection of Hg^2 + or total mercury by varying the temperature of the measurement cell. Only the inorganic mercury is measured when the quartz cell is at room temperature, and when the cell is heated to 650 °C or higher the total Hg concentration is measured. The organic Hg concentration in the sample is calculated from the difference between the total Hg and Hg^2 + concentrations. Parameters such as the type of acid (HCl or HNO₃) and its concentration, reductant (NaBH₄) concentration, carrier solution (HCl) flow rate, carrier gas flow rate, sample volume and quartz cell temperature, which influence FI-VG AAS system performance, were systematically investigated. The optimized conditions for Hg^2 + and total Hg determinations were: 1.0 mol l^− 1 HCl as carrier solution, carrier flow rate of 3.5 ml min^− 1, 0.1% (m/v) NaBH₄, reductant flow rate of 1.0 ml min^− 1 and carrier gas flow rate of 200 ml min^− 1. The relative standard deviation (RSD) is lower than 5.0% for a 1.0 μg l^− 1 Hg solution and the limit of quantification (LOQ, 10 s) is 55 ng g^− 1. Certified samples of dogfish muscle (DORM-1 and DORM-2) and non-certified fish samples were analyzed, using a 6.0 mol l^− 1 HCl solution for analyte extraction. The Hg^2 + and CH₃Hg⁺ concentrations found were in agreement with certified ones.