On-line liquid-liquid extraction system using a new phase separator for flame atomic absorption spectrometric determination of ultra-trace cadmium in natural waters

A robust flow injection (FI) on-line liquid-liquid extraction (LLE) preconcentration/separation system associated with a newly designed gravitational phase separator, coupled to flame atomic absorption spectrometry (FAAS) was developed. The performance of the system was illustrated for cadmium determination at the μg l⁻¹ level. The non-charged cadmium complex with ammonium pyrrolidine dithiocarbamate (APDC) was extracted on-line into isobutyl methyl ketone (IBMK). The organic phase was effectively separated from a large volume of aqueous phase and is led into a 100 μl loop of an injection valve before its introduction into the nebulizer. The system was optimized and offered good performance characteristics with unlimited life time of phase separator, greater flow rate ratios and improved flexibility, as compared with other solvent extraction preconcentration systems. With a sampling frequency of 33 h⁻¹, the enhancement factor was 155, the detection limit was 0.02 μg l⁻¹, the relative standard deviation was 3.2% at 2.0 μg l⁻¹ Cd concentration level and the calibration curve was linear over the concentration range 0.06-6.0 μg l⁻¹. The accuracy of the proposed method was evaluated by analyzing a certified reference material of water and by recovery measurements on spiked samples. Finally, it was successfully applied to the analysis of tapwater, river and seawater samples.     

Flow injection wetting-film extraction system for flame atomic absorption spectrometric determination of cadmium in environmental waters

A newly simple flow injection wetting-film extraction system coupled to flame atomic absorption spectrometry (FAAS) has been developed for trace amount of cadmium determination. The sample was mixed on-line with sodium diethyl dithiocarbamate and the produced non-charged Cd(II)-diethyl dithiocarbamate (DDTC) chelate complex was extracted on the thin film of diisobutyl ketone (DIBK) on the inner wall of the PTFE extraction coil. The wetting-film with the extracted analyte was then eluted by a segment of the cover solvent, and transported directly to the FAAS for evaluation. All the important chemical and flow parameters were optimized. Under the optimized conditions an enhancement factor of 35, a sample frequency of 22 h⁻¹ and a detection limit of c_L = 0.7 μg l⁻¹ Cd(II) were obtained for 60 s preconcentration time. The calibration curve was linear over the concentration range 1.5-45.0 μg l⁻¹ Cd(II) and the relative standard deviation, R.S.D. (n = 10) was 3.9%, at 10.0 μg l⁻¹ concentration level. The developed method was successfully applied to cadmium determination in a variety of environmental water samples as well as waste-water sample.     

On-line electrolytic dissolution of solid metal samples and determination of copper in aluminium alloys by flame atomic absorption spectrometry

A flow-injection system was developed in which alloy metal samples are electrolytically dissolved and the dissolved samples are analysed by flame atomic absorption spectrometry (FAAS). The effects of electrolyte composition and electrolysis parameters on the dissolution of the sample were studied. The method was used for the determination of copper in aluminium alloys. Electrolyte solutions consisting of 0.2–1.0 M nitric acid are better than other electrolytes tested with regard to both alloy sample dissolution and determination of copper by FAAS. The peak height increases linearly with the electrolysis time or current within a certain range. The detection limit depends on the sensitivity of the detector used, and can be improved by increasing the electrolysis time or current. Generally, aluminium alloys containing 0.5–10% copper can give suitable signals for FAAS determination. The reproducibility of electrolysis and determination is about 4% for the same sampling points and 5% for different sampling points on the alloy sample.     

On-line sequential injection dispersive liquid-liquid microextraction system for flame atomic absorption spectrometric determination of copper and lead in water samples

A simple, sensitive and powerful on-line sequential injection (SI) dispersive liquid-liquid microextraction (DLLME) system was developed as an alternative approach for on-line metal preconcentration and separation, using extraction solvent at microlitre volume. The potentials of this novel schema, coupled to flame atomic absorption spectrometry (FAAS), were demonstrated for trace copper and lead determination in water samples. The stream of methanol (disperser solvent) containing 2.0% (v/v) xylene (extraction solvent) and 0.3% (m/v) ammonium diethyldithiophosphate (chelating agent) was merged on-line with the stream of sample (aqueous phase), resulting a cloudy mixture, which was consisted of fine droplets of the extraction solvent dispersed entirely into the aqueous phase. By this continuous process, metal chelating complexes were formed and extracted into the fine droplets of the extraction solvent. The hydrophobic droplets of organic phase were retained into a microcolumn packed with PTFE-turnings. A portion of 300 μL isobutylmethylketone was used for quantitative elution of the analytes, which transported directly to the nebulizer of FAAS. All the critical parameters of the system such as type of extraction solvent, flow-rate of disperser and sample, extraction time as well as the chemical parameters were studied. Under the optimum conditions the enhancement factor for copper and lead was 560 and 265, respectively. For copper, the detection limit and the precision (R.S.D.) were 0.04 μg L⁻¹ and 2.1% at 2.0 μg L⁻¹ Cu(II), respectively, while for lead were 0.54 μg L⁻¹ and 1.9% at 30.0 μg L⁻¹ Pb(II), respectively. The developed method was evaluated by analyzing certified reference material and applied successfully to the analysis of environmental water samples.     

Flow injection sorbent extraction with dialkyldithiophosphates as chelating agent for the determination of cadmium, copper and lead by flame atomic absorption spectrometry

Using octadecyl functional groups (C₁₈) bonded to silica gel as sorbent and methanol as eluent, the flow injection sorbent extraction features of dialkyldithiophosphates (RO)₂P(S)S⁻ as the chelating agent for cadmium, copper and lead was investigated in respect of the effects of pH, alkyl substituent group, reagent concentration and masking agent, with flame atomic absorption spectrometric detection. The elements are quantitatively extracted with the short-alkyl-chain reagents (R up to propyl) in acidic medium. The extractability decreases with the number of carbon atoms in the alkyl groups of the reagents and with the reagent concentration when the alkyl groups are larger than butyl, but masking agents increase the extractability. An explanation proposed for this effect is the formation of polynuclear chelates. Diethyldithiophosphate can be used for the selective determination of cadmium, copper and lead in digested solid environmental samples. With 20 s sample loading at 8.7 ml min⁻¹, the enhancement factors are 35 for cadmium and copper or 26 for lead; the detection limits (3σ) are 0.8, 1.4 and 10.0 μg 1⁻¹ for cadmium, copper and lead, respectively.     

Flow injection on-line hydrophobic sorbent extraction for flame atomic absorption spectrometric determination of cadmium in water samples

A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was formed on-line in 0.1 mol L⁻¹ HNO₃ and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized. By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h⁻¹. For 30 s preconcentration time the detection limit was 0.3 μg L⁻¹ and the relative standard deviation at 5.0 μg L⁻¹ Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 μg L⁻¹. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water). Good recoveries were obtained for spiked natural-water and waste-water samples. Correspondence: Aristidis N. Anthemidis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, GR-Thessaloniki 54124, Greece     

Coupling continuous ultrasound-assisted extraction, preconcentration and flame atomic absorption spectrometric detection for the determination of cadmium and lead in mussel samples

Continuous ultrasound-assisted extraction has been coupled with preconcentration and flame atomic absorption spectrometry for the determination of cadmium and lead in mussel samples. Experimental designs were used for the optimisation of the leaching and preconcentration steps. The use of diluted nitric acid as extractant in the continuous mode at a flow rate of 3.5 ml min⁻¹ and room temperature was sufficient for quantitative extraction of these trace metals. A minicolumn containing a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was proved as an excellent material for the quantitative preconcentration of cadmium and lead prior to their flame atomic absorption detection. A flow injection manifold was used as interface for coupling the three analytical steps, which allowed the automation of the whole analytical process. A good precision of the whole procedure (2.0 and 2.3%), high enrichment factors (20.5 and 11.8) and a detection limit of 0.011 and 0.25 μg g⁻¹ for cadmium and lead, respectively, were obtained for 80 mg of sample. The sample throughputs were ca. 16 and 14 samples h⁻¹ for cadmium and lead, respectively. The accuracy of the analytical procedures was verified by using a standard reference material (BCR 278-R, mussel tissue) and the results were in good agreement with the certified values. The method was successfully applied to the determination of trace amounts of cadmium and lead in mussel samples from the coast of Galicia (NW, Spain).     

On-line sorptive preconcentration platform incorporating a readily exchangeable Oasis HLB extraction micro-cartridge for trace cadmium and lead determination by flow injection-flame atomic absorption spectrometry

A simple, sensitive and inexpensive flow injection solid phase extraction (SPE) system was developed for automatic determination of trace level concentrations of metals. The potentials of this novel scheme, coupled to flame atomic absorption spectrometry (FAAS), were demonstrated for trace cadmium and lead determination in environmental water samples. The method was based on on-line chelate complex formation of target species with ammonium diethyldithiophosphate (DDTP), retention onto the surface of reversed-phase poly(divinylbenzene-N-vinylpyrrolidone) co-polymeric beads (Oasis HLB) and elution with methanol prior to atomization. A special PVC adapter was designed for easy and rapid replacement of the commercially available SPE cartridge. All main chemical and hydrodynamic parameters affecting the complex formation, sorption and elution of the analyte were optimized thoroughly. Moreover, the effect of potential interfering species occurring in environmental samples was also explored.For 90 s preconcentration time, enhancement factors of 155 and 180, detection limits (3s) of 0.09 μg L^− 1 and 0.9 μg L^− 1 and relative standard deviations (R.S.D.) of 2.9% (at 4.0 μg L^− 1) and 2.6% (at 20.0 μg L^− 1) were obtained for cadmium and lead, respectively, with a sample throughput of 24 h^− 1. The measurement trueness of the developed method was evaluated by analyzing a certified reference material and spiked environmental water samples. The proposed method is well suited to detect the target elements at concentration levels below the maximum allowed concentrations endorsed by the European Framework Directive (2008/105/EC) in inland and coastal waters.     

Evaluation of polychlorotrifluoroethylene as sorbent material for on-line solid phase extraction systems: determination of copper and lead by flame atomic absorption spectrometry in water samples

Polychlorotrifluoroethylene (PCTFE) in the form of beads was applied, as packing material for flow injection on-line column preconcentration and separation systems coupled with flame atomic absorption spectrometry (FAAS). Its performance characteristics were evaluated for trace copper determination in environmental samples. The on-line formed complex of metal with diethyldithiophosphate (DDPA) was sorbed on the PCTFE surface. Isobutyl methyl ketone (IBMK) at a flow rate of 2.8 mL min⁻¹ was used to elute the analyte complex directly into the nebulizer-burner system of spectrophotometer. The proposed sorbent material reveal, excellent chemical and mechanical resistance, fast adsorption kinetics permitting the use of high sample flow rates up to 15 mL min⁻¹ without loss of retention efficiency. For copper determination, with 90 s preconcentration time the sample frequency was 30 h⁻¹, the enhancement factor was 250, which could be further improved by increasing the loading (preconcentration) time. The detection limit (3s) was c_L = 0.07 μg L⁻¹, and the precision (R.S.D.) was 1.8%, at the 2.0 μg L⁻¹ Cu(II) level. For lead determination, the detection limit was c_L = 2.7 μg L⁻¹, and the precision (R.S.D.) 2.2%, at the 40.0 μg L⁻¹ Pb(II) level. The accuracy of the developed method was evaluated by analyzing certified reference materials and by recovery measurements on spiked natural water samples.     

On-line electrochemical preconcentration and flame atomic absorption spectrometric determination of manganese in urine samples

A sensitive and selective method was developed for the determination of traces of manganese in urine using on-line electrochemical preconcentration followed by flame atomic absorption spectrometry detection. A home made flow-through polypropylene cell (4.5 cm long × 0.8 cm diameter filled with glass marbles) with an effective inner volume of 0.5 ml containing a working and a counter electrode, both of glassy carbon and a Pt pseudo reference electrode was located in a flow injection manifold specially designed for the purpose of this work. The manganese was deposited from buffer solution of NH₃/NH₄Cl at pH 9.00 through an oxidizing process at a current of 400 mA during 7 min. A flow of HCl 0.1 mol l⁻¹ at 4 ml min⁻¹ through the cell, chemically dissolved the deposit. A small portion (15 μl) of the concentrate was introduced in a continuously flowing system by means of a timing device and was then carried to the detector for the manganese quantification. All electrochemical and spectroscopic variables as well as possible interferences in both systems were systematically studied. The relative standard deviations for ten consecutive measurements of manganese solutions of 2.0 and 20 μg l⁻¹ were of 2.3 and 1.5%, respectively, while for a sample processed five times was less then 5%. The accuracy of the developed procedure was evaluated by adding known amounts of manganese standard to urine samples and following the whole procedure. Recoveries within the range 97.2-102.8% were obtained. To further prove the accuracy, a Seronorm Trace Elements in Urine, Batch 403125 sample with a reported concentration of 13 μg Mn l⁻¹ was also analyzed. The experimental value obtained was of 12.7 ± 0.1 μg l⁻¹, which does not differ significantly from the reported amount (p < 0.05). A preconcentration factor of 40, a linear range between 0.015 and 60 μg l⁻¹ and a limit of detection of 15 ng l⁻¹ permitted the determination of manganese in real urine samples from non-exposed subjects in the range 0.5-2.8 μg l⁻¹.     

Coupling of flow injection wetting-film extraction without segmentation and phase separation to flame atomic absorption spectrometry for the determination of trace copper in water samples

A flow injection wetting-film extraction system without segmentor and phase separator has been coupled to flame atomic absorption spectrometry for the determination of trace copper. Isobutyl methyl ketone (MIBK) was selected as coating solvent and 8-hydroxyquinoline (oxine) as the chelating reagent. By switching of a 8-channel valve and alternative initiation of two peristaltic pumps, MIBK, sample solution containing copper chelate of oxine, and air-segment sandwiched eluting solution (1.0 mol l⁻¹ nitric acid) were sequentially aspirated into an extraction coil made of PTFE tubing of 360 cm length and 0.5 mm i.d. The formation of organic film in the wall of the extraction coil, extraction of the copper chelate into the organic film and back-extraction of the analyte into the eluting solution occurred consecutively when these zones aspirated into the extraction coil were propelled down the extraction coil by a carrier solution at a flow rate of 2 ml min⁻¹. After leaving the extraction coil, the concentrated zone was transported to the nebulizer at its free uptake rate for atomization. Under the optimized conditions, an enrichment factor of 43 and a detection limit of 0.2 μg l⁻¹ copper were achieved at a sample throughput rate of 30 h⁻¹. Eleven determinations of a standard copper solution of 60 μg l⁻¹ gave a relative standard deviation of 1.5%. Foreign ions possibly present in tap water and natural water did not interfere with the copper determination. The developed method has been successfully used to the determination of copper content of tap water and river water.     

Flow injection on-line displacement/solid phase extraction system coupled with flame atomic absorption spectrometry for selective trace silver determination in water samples

A novel flow injection (FI) on-line displacement solid phase extraction preconcentration and/or separation method coupled with FAAS in order to minimize interference from other metals was developed for trace silver determination. The proposed method involved the on-line formation and subsequently pre-sorption of lead diethyldithiocarbamate (Pb-DDTC) into a column packed with PTFE-turnings. The preconcentration and/or separation of the Ag(I) took place through a displacement reaction between Ag(I) and Pb(II) of the pre-sorbed Pb-DDTC. Finally, the retained analyte was eluted with isobutyl methyl ketone (IBMK) and delivered directly to nebulizer for measuring. Interference from co-existing ions with lower DDTC complex stability in comparison with Pb-DDTC, was eliminated without need for any masking reagent. With 120 s of preconcentration time at a sample flow rate of 7.6 mL min−1, an enhancement factor of 110 and a detection limit (3 s) of 0.2 μg L−1 were obtained. The precision (RSD, n = 10) was 3.1% at the 10 μg L−1 level. The developed method was successfully applied to trace silver determination in a variety of environmental water samples and certified reference material.     

On-line solid phase extraction coupled to flame atomic absorption spectrometry for the determination of trace copper and zinc in environmental and biological samples

In this work, bamboo charcoal (BC) was used as a sorbent for on-line solid phase extraction (SPE) coupling with flame atomic absorption spectrometry (AAS) for trace copper and zinc determination in environmental and biological samples. Under the optimum pH of 5.5 (for Zn) and 7.0 (for Cu), trace copper and zinc were effectively adsorbed on the microcolumn and the retained cations were efficiently eluted with HCl or HNO₃ with an appropriate concentration and flow rate for on-line AAS determination. With a sample loading time of 60 s at a sample flow rate of 7.6 mL min^?1, the enhancement factors of 39 (for Cu) and 30 (for Zn) and detection limits (3σ) of 0.60 µg L^?1 (for Cu) and 0.36 µg L^?1 (for Zn), respectively, were achieved. The sample throughput was 45 h^?1. At the level of 20 µg L^?1of Cu(II) and Zn(II), the precision (RSD, n?=?11) were found to be 0.26% and 1.6%, respectively. The proposed method has been successfully applied to the determination of copper and zinc in environmental and biological samples.     

On-line precipitation–dissolution in knotted reactor for thermospray flame furnace AAS for determination of ultratrace cadmium

A simple, environmentally friendly, cost-effective and sensitive method was developed for the determination of trace cadmium in rice and water by using flow injection (FI) on-line precipitation–dissolution in a knotted reactor (KR) as a preconcentration scheme for thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). The preconcentration was achieved by online merging the sample solution and the precipitating reagent in a KR and subsequently eluting the resultant precipitate of cadmium hydroxide with 1 mol/L HNO₃. The eluant was then introduced into TS-FF-AAS for the determination. A self-assembled FI system was employed to hyphenate the KR system with TS-FF-AAS. Under optimal chemical and instrumental conditions, a limit of detection of 0.04 μg/L and a sensitivity enrichment factor of 34 for cadmium was obtained with a total initial sample volume of 4 mL. The proposed method was applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with their certified values. Real rice samples and real water samples were also determined by the proposed method, with analytical results confirmed by inductively coupled plasma mass spectroscopy (ICP-MS).     

On-line solid phase extraction system using PTFE packed column for the flame atomic absorption spectrometric determination of copper in water samples

A new flow injection on-line adsorption preconcentration system adapted to flame atomic absorption spectrometry (FAAS) for copper determination at the mug l(-1) level was developed. Polytetrafluoroethylene (PTFE) turnings packed in a mini-column were used as sorbent material. The copper ammonium pyrrolidine dithiocarbamate (APDC) complex was sorbed on the PTFE turnings, from which it could be eluted on-line instantly by isobutyl methyl ketone (IBMK) into the flame at a flow rate of 2.3 ml min(-1). The system was optimized and offered good performance characteristics with practically unlimited life time, greater flow rates and improved flexibility, as compared with other sorbent materials and the knotted reactor preconcentration systems. With 1 min preconcentration time, and a sample frequency of 40 h(-1), the enhancement factor was 340, which could be further improved by increasing the preconcentration time. The detection limit was c(L)=0.05 mug l(-1), and the precision was 1.5%, at the 2.0 mug l(-1) Cu level. The method has been applied successfully to the analysis of potable, river and seawater, and its accuracy was tested by the analysis of certified reference materials and by recovery measurements on spiked samples. No significant interferences exist from other substances usually occurring in natural water.     

Ultrasound-assisted emulsification-microextraction combined with flame atomic absorption spectrometry for determination of trace cadmium in water samples

The process of ultrasound-assisted emulsification-microextraction (USAEME) was successfully applied for the first time for the extraction and pre-concentration of trace cadmium from water samples, followed by flame atomic absorption spectrometry (FAAS). In the proposed approach, sodium diethyldithiocarbamate trihydrate solution (NaDDTC·3H₂O) was used as a chelating agent and carbon tetrachloride was selected as extraction solvent. Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters included extraction solvent type as well as extraction volume, time, temperature, and pH, the amount of the chelating agent, and salt effect. Under optimum conditions, an enrichment factor of 95 was obtained from only 5.0 mL of water sample. The calibration graph was linear in the range of 10-600 μg L⁻¹ with a detection limit of 0.91 μg L⁻¹. The relative standard deviation (R.S.D) for ten replicate measurements of 50 and 500 μg L⁻¹ of cadmium were 2.56 and 1.62%. This proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries over the range of 96.5-101.7% were obtained.     

Electrochemical hydride generation atomic absorption spectrometry for determination of cadmium

An electrolytic hydride generation system for determination of another hydride forming element, cadmium, by catholyte variation electrochemical hydride generation (EcHG) atomic absorption spectrometry is described. A laboratory-made electrolytic cell with lead-tin alloy as cathode material is designed as electrolytic generator of molecular hydride. The influences of several parameters on the analytical signal have been evaluated using a Plackett-Burman experimental design. The significant parameters such as cathode surface area, electrolytic current, carrier gas flow rate and catholyte concentration have been optimized using univariate method. The analytical figures of merit of procedure developed were determined. The calibration curve was linear up to 20 ng ml⁻¹of cadmium. The concentration detection limit (3σ, n = 8) of 0.2 ng ml⁻¹ and repeatability (relative standard deviation, n = 7) of 3.1% were achieved at 10.0 ng ml⁻¹. It was shown that interferences from major constituents at high concentrations were significant. The accuracy of method was verified using a real sample (spiked tap water) by standard addition calibration technique. Recovery of 104% was achieved for Cd in the spiked tap water sample.     

Dithizone immobilized silica gel on-line preconcentration of trace copper with detection by flame atomic absorption spectrometry

A novel adsorbent-silica gel bound dithizone (H₂Dz-SG) was prepared and used as solid-phase extraction of copper from complex matrix. The H₂Dz-SG is investigated by means of FT-IR spectra and the SEM images, demonstrating the bonding of dithizone. The H₂Dz-SG quantitatively adsorb copper ions, and the retained copper is afterwards collected by elution of 10% (v/v) nitric acid. An on-line flow injection solid-phase extraction procedure was developed for trace copper separation and preconcentration with detection by flame atomic spectrometry. By loading 5.4 mL of sample solution, a liner range of 0.5-120 μg L⁻¹, an enrichment factor of 42.6, a detection limit of 0.2 μg L⁻¹ and a precision of 1.7% RSD at the 40 μg L⁻¹ level (n = 11) were obtained, along with a sampling frequency of 47 h⁻¹. The dynamic sorption capacity of H₂Dz-SG to Cu²⁺ was 0.76 mg g⁻¹. The accuracy of the proposed procedure was evaluated by determination of copper in reference water sample. The potential applications of the procedure for extraction of trace copper were successfully accomplished in water samples (tap, rain, snow, sea and river). The spiking recoveries within 91-107% are achieved.     

Extraction system for flame atomic absorption spectrometric analysis of high-purity bismuth compounds

Two new ligands, 2-(2-benzoxazolyl)cyanoacetaldehyde and 2-(2-benzoxazolyl)malonaldehyde are proposed for extractive separation and preconcentration. The extraction behaviour of Ag, Bi, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Pd, Pt, Sb and Zn with respect to pH, salt concentration and the presence of various masking agents was studied. A simple extraction procedure for the analysis of high-purity bismuth compounds was developed.     

Flow injection analysis-flame atomic absorption spectrometry system for indirect determination of cyanide using cadmium carbonate as a new solid-phase reactor

A new and simple flow injection system procedure has been developed for the indirect determination of cyanide. The method is based on insertion of aqueous cyanide solutions into an on-line cadmium carbonate packed column (25% m/m suspended on silica gel beads) and a sodium hydroxide with pH 10 is used as the carrier stream. The eluent containing the analyte as cadmiumcyanide complexes, produced from reaction between cadmium carbonate and cyanide, measured by flame atomic absorption spectrometry. The absorbance is proportional to the concentration of cyanide in the sample. The linear range of the system is up to 15 mg L⁻¹ with a detection limit 0.2 mg L⁻¹ and sampling rate 72 h⁻¹. The method is suitable for determination of cyanide in industrial waste waters with a relative standard deviation better than 1.22%.