Microvolume UV Vis Spectrophotometry Research Articles

Application of a Deep Eutectic Solvent for Dispersive Liquid–Liquid Microextraction of Trace Amount of Pb (II) in Water Samples and Determination by Microvolume UV–Vis Spectrophotometry

Application of a Deep Eutectic Solvent for Dispersive Liquid–Liquid Microextraction of Trace Amount of Pb (II) in Water Samples and Determination by Microvolume UV–Vis Spectrophotometry

Micro-spectrophotometric determination of nickel in Gentiana rigescens after switchable hydrophilicity solvent-based ultrasound-assisted liquid phase microextraction

In this work, switchable hydrophilicity solvent-based ultrasound-assisted liquid phase microextraction (SHS-UA-LPME) was combined with micro-volume UV-vis spectrophotometry for the determination of trace nickel in the medicinal plant Gentiana rigescens Franch. ex Hemsl. (G. rigescens) samples for the first time. Micro-volume spectrophotometry has the characteristics of microanalysis, economy and low operation cost, which is feasible to be combined with miniaturized enrichment method. Dipropylamine (DPA) as a switchable solvent completed the extraction during the phase conversion process. It was changed from hydrophobic to hydrophilic under the action of HCl, and then completed phase transition under the action of NaOH. The parameters influencing the extraction efficiency were investigated. Under the optimal conditions, the enhancement factor (EF), the limit of detection (LOD), the limit of quantitation (LOQ) and relative standard deviation (RSD, n = 7) were 28, 0.02 µg/L, 0.067 µg/L and 1.4%, respectively. The established method was applied to the determination of G. rigescens samples collected from the local field with satisfactory results.

Eco-friendly trace analysis of silver in beer/wine samples using a new co-polymeric nanocomposite based-ultrasound assisted-cloud point extraction combined with spectrophotometry

In this study, a new magnetic nanocomposite based on the tris(2-hydroxymethyl)aminomethane-modified poly(styrene-co-N-maleimide) copolymer and Fe3O4 nanoparticles were prepared as a new micellar interface for pre-concentration of trace levels of silver from aqueous solutions by ultrasound assisted-cloud point extraction (UA-CPE). The structure of the nanocomposite was characterized by using some instrumental tools in detail. The method is selectively based on charge transfer among silver and reagents at pH 5.0, and detection by micro-volume UV–vis spectrophotometry at 346 nm. The main variables affecting extraction efficiency were evaluated and optimized in detail. Under the optimized conditions, the method shows good linear relationships in ranges of 2.5−125 μg L−1 and 4−160 μg L−1 by two calibration curves (established in solvent and beer/wine matrices) with a better determination coefficient (r2) than 0.992. The limits of detection, repeatability/intermediate precision (as RSDs%, 5, 25 and 100 μg L-1, n: 5) and recovery percentages were 0.85/1.21 μg L-1, 3.5–7.1% and 91.5–98.5%, respectively. From pre-concentration of 25-mL sample solution, a pre-concentration factor was found to be 62.5 with sensitivity enhancement of 23.2-fold in calibration. A matrix effect was not observed for the triplicate measurements of 100 μg L−1 Ag+ in the presence of various interfering species. The method accuracy was validated with the outcome of validation that was carried out. The method after two sample preparation procedures was successfully applied to reliable determination of total Ag in beer and wine samples. The total Ag levels were in range of 2.5–4.2 and 2.7–5.5 μg L−1 in beer and wine samples, respectively.

Application of a novel poly(SMAm)-Tris-Fe3O4 nanocomposite for selective extraction and enrichment of Cu(I) /Cu(II) from beer, soft drinks and wine samples, and speciation analysis by micro-volume UV–Vis spectrophotometry

In this study, a novel functional nanocomposite was synthesized, characterized and selectively used in pH-controlled separation, pre-concentration and speciation analysis of Cu(I) and Cu(II) from sample matrices where extraction is assisted, facilitated and greatly enhanced by ultrasound energy. The hydrophilic composite material functionalized with tris(2-hydroxymethyl)aminomethane (Tris) and Fe3O4 NPs was characterized in detail by ATR-FT-IR, 1H NMR, XRD, EDX peaks and SEM images. After optimization of the main variables influencing extraction efficiency such as pH, volumes of buffer, modified copolymer in acetone, CTAB and Triton X-114 at fixed concentrations including sonication conditions, the Cu(I) and Cu(II) were monitored against a blank at 347 nm by micro-volume UV–vis spectrophotometer. A good linearity was obtained in the range of 2–140 and 5–150 μg L−1 for Cu(II) and Cu(I) with r2 ≥ 0.993. The limits of detection (LODs) of 0.66 and 1.60 μg L−1 for each analyte, were obtained from a pre-concentration of 70-fold. After validation, the method was applied to speciation of Cu(I), Cu(II), and total Cu in the pre-treated and diluted beverage samples before and after pre-oxidation of Cu(I) to Cu(II) due to be more sensitive of extraction process to Cu(II) at pH 6.0. The results were also compared with those obtained by FAAS analysis to ensure the reliability of the results. It was observed that there was a statistically good agreement between the results of both methods.

Selective extraction and enrichment of 5-hydroymethylfurfural from honey, molasses, jam and vinegar samples prior to sensitive determination by micro-volume UV-vis spectrophotometry

In this study, a new method was developed for the extraction/enrichment of 5-hydroxymethylfurfural (5-HMF) from sample matrix prior to analysis. The method is based on the selective formation of the imine adduct and ion-pair between 5-HMF and phenosafranine (weak base, PSF+) in the presence of sodium dodecyl sulfate (SDS) at pH 5.5 by the base induced disproportionation. Then, the complexes were enriched into the micellar phase of Triton X-114, diluted with ethanol, and detected at 532 nm by micro-volume UV–vis spectrophotometry. The variables affecting extraction efficiency were optimized. In optimal conditions, the calibration curves were over the range of 2−100 and 2−200 μg L−1 with the detection limits of 0.53 and 0.75 μg L−1 using 0.2 and 3.0 mL of 1.0 × 10-3 mol L−1 SDS. From enrichment of 15-mL sample, an enrichment factor of 37.5-fold was obtained. The accuracy/ precision studies after spiking were performed, and observed to be in range of 97.3–102.3 % and 2.5−3.8% (10, 25 and 75 μg L−1, n: 5). After validation, the method was applied to the analysis of the selected foods. From the results, it was observed that 5-HMF levels were in the range of 1.05–18.10 mg kg−1 with a RSD% of 3.0–4.2 % and recovery of 95.5–98.0 % by sample extraction with sonication while they ranged from 1.15–18.05 mg kg−1 with a RSD% of 3.0–4.2 % and recovery of 95–99 % without sonication. Finally, it was observed that the results obtained were in agreements with those of the modified White method, statistically validating the method.

Coupling of ion pair ultrasound assisted-cloud point extraction to microvolume UV-Vis spectrophotometry for speciation analysis of ionic NO2-,NO3- and total NO2-/NO3- without and with reduction in the selected beverage and food matrices

ABSTRACT This study proposes a simple, low-cost, easy to use, fast, accurate and reliable ultrasound assisted-cloud point extraction (UA-CPE) method for the enrichment and speciation analysis of low levels of ionic NO2 −, NO3 − and total NO2 −/NO3 − without and with reduction by micro-volume UV-vis spectrophotometry. The method relies on the reaction of NO2 − with excess iodide at pH 5.5 to form triiodide, and then the extraction of the oxidation product formed by charge transfer into micellar phase of Triton X-114 using cationic redox-sensitive phenazine dye, neutral red (NRH+) as ion-pairing in absence and presence of 1.5 mL of 1.0 × 10−3 mol L−1 Br− ions. The main variables affecting extraction efficiency were studied and optimised in detail. Under the optimal conditions, the calibration curves in solvent were linear over the ranges of 5–100 and 100–1280 µg L−1 with a detection limit of 1.32 µg L−1 while the matrix-matched calibration curves prepared from sample extracts were linear over the ranges of 5–125 and 125–1350 µg L−1 with a detection limit ranging from 1.15 to 1.50 µg L−1 for sample matrices. From pre-concentration of 25-mL sample, pre-concentration and sensitivity enhancement folds of 62.5 and 76.5 were obtained. The accuracy/precision studies after spiking were performed, and observed to be in range of 96.5–99.6% and 1.9–5.7% (15, 75 and 250 µg L−1, n: 5). The speciation analysis of ionic NO2 −, NO3 − and total NO2 −/NO3 − was performed from artificially prepared binary mixtures after reduction with a mixture of Zn and NaCl in acidic media. The free NO3 − contents of samples were calculated from difference between free NO2 − and total NO2 −/NO3 − contents. After validation by analysis of a certified sample, the method was successfully applied to the speciation analysis of the beverage, cured meat, vegetable and milk samples. After pre-treatment with two sample preparation steps, it was observed that the results obtained were also compatible with each other, statistically validating the method.

Selective extraction of Cu+ and Cu2+ ions from mushroom and lichen samples prior to analysis by micro-volume UV-Vis spectrophotometry: Application of a novel poly (SMIm)-Tris-Fe3O4 nanocomposite

In this study, a novel poly (SMIm)-Tris-Fe3O4 nanocomposite was prepared for selective extraction of Cu+ and Cu2+ ions by ultrasound assisted-cloud point extraction (UA-CPE). The nanocomposite was characterized by analysis of ATR-FT-IR, 1H NMR and XRD. After optimization of the extraction conditions, the copper ions were independently detected against sample blank at 347 nm by micro-volume UV–vis spectrophotometer. Under the optimal conditions, good linear relationship was obtained in the ranges of 0.3−150 and 10−350 μg L−1 for each ion at pH 7.0 and pH 5.0, respectively, with a better regression coefficient than 0.992. The method detection limits, accuracy and precision were 0.095 and 3.03 μg L−1, 91.5−96.0 % and 93.0−98.5 %, and 2.5–4.5 and 3.8–7.1 % (n:5, 25 and 100 μg L−1) for Cu+ and Cu2+ ions, respectively. A preconcentration of 70-fold was obtained from 35-mL of sample. After validation, the method was successfully applied to determination of total Cu levels in lichen and mushroom samples after pre-reduction at pH 7.0, and the recoveries in the range of 90−96 % were obtained by two calibration approaches after spiking with 10 μg L−1. The results were also statistically compared with those obtained by FAAS analysis to ensure accuracy and precision.

Use of new polymeric composites for preconcentration of trace Ag+ ions from the selected mushroom/vegetables by ultrasound-assisted cloud-point extraction coupled to microvolume UV-Vis spectrophotometry

ABSTRACT The magnetic nano-composites based on the tris(hydroxymethlmethyl)aminomethane-modified maleic anhydride-co-styrene copolymers and Fe3O4 nano-particles were prepared as new potential chelating agents for ultrasound-assisted-cloud point extraction (UA-CPE) and pre-concentration of trace levels of Ag+ ions from aqueous solutions. The structures of the nano-composites were characterised via FT-IR, 1H-NMR and XRD analysis. After structural characterisation of composites, Ag+ ions were detected by micro-volume UV-vis spectrophotometry at 347 nm. The variables affecting complex formation and extraction efficiency for separation/pre-concentration of the Ag+ ions from various food matrices were evaluated and optimised in detail. Under the optimised conditions, the method shows a good sensitivity with linearity range from 10 to 350 µg L−1 and 4 to 160 µg L−1 for amidic and imidic composites, respectively, with a better correlation coefficient than 0.9825. The limits of detection, intra- and inter-day precision (as RSDs%) and recovery rates for six replicate determinations of Ag+ ions at levels of 25 and 100 μg L−1 were 4.28/1.21 μg L−1, 2.4–4.1% and 92–98% for the modified copolymers, respectively. The pre-concentration factor for Ag+ ion from pre-concentration of 35-mL sample was 70. A significant matrix effect was not observed for the triplicate measurements of 100 µg L−1 Ag+ in the presence of various interfering species below their maximum concentrations allowed in this method, for Ag+ ions. The accuracy of the method was confirmed by analysis of the two certified samples. The method was successfully applied to determine low levels of Ag+ ions in mushroom and vegetable samples, and satisfactory recoveries were obtained in the range of 91-97% with lower RSD than 5.1% for the spiked samples.

(4-Hydroxy-2-oxo-2H-chromen-3-yl)methyl pyrrolidine-1-carbodithioate as a novel, highly selective and sensitive ligand for determination of copper in water and food samples by dispersive liquid–liquid microextraction coupled with microvolume UV–Vis spectrophotometry

In this research, a fast, simple, selective, and sensitive spectrophotometric method based on dispersive liquid–liquid microextraction (DLLME) was developed for the ultratrace determination of copper(II) using newly synthesized chromogenic reagent (4-hydroxy-2-oxo-2H-chromen-3-yl)methyl pyrrolidine-1-carbodithioate (HCDTC). The affecting factors in complexation and microextraction steps were investigated and optimized. HCDTC forms highly sensitive yellow-colored complex with copper(II) (1:4 [copper(II): ligand]) in the wide pH range which shows maximum absorbance at 445 nm. In direct determination, Beer’s law was obeyed in the concentration range from 0.1 to 5.0 mg L−1. Molar absorptivity and Sandell’s sensitivity values for Cu(II)–HCDTC complex were 1.3 × 104 and 0.0047 µg cm−2, respectively. However, by applying DLLME, a detection limit as low as 0.3 µg L−1 with preconcentration factor of 92 and relative standard deviation (n = 6) less than 3.5% were achieved. Moreover, calibration graph was linear in the range of 1.0–200 µg L−1. Finally, the proposed method was successfully applied for preconcentration and determination of the Cu(II) in some water and fruit juice samples, and satisfactory results were obtained. Accuracy and reliability of the method were also verified by GF-AAS.

Ultra-Trace Determination of Silver in Water, Soil and Radiology Film Samples Using Dispersive Liquid-Liquid Microextraction and Microvolume UV–Vis Spectrophotometry

In this research, a Dispersive Liquid-Liquid MicroExtraction (DLLME) method coupled to UV-vis spectrophotometry was developed for the indirect determination of silver ion. The method is based on the catalytic effect of the silver ion on the oxidation of congo red by potassium peroxodisulphate and extraction with DLLME procedure using chloroform (extraction solvent) containing cetyltrimethyl ammonium bromide which provides counter ion and also acts as a disperser. After extraction, the phase separation is performed with a centrifugation, and the silver ion is determined in the enriched phase by UV-Vis spectrophotometry. Several factors affecting the microextraction efficiency, such as pH of the solution, extraction time, type and volume of extraction solvent were investigated. Under optimum conditions, a linear calibration graph in the range of 0.5-105.0 ng/mL of silver ion in the initial solution with r2 = 0.9987 (n=10) was obtained. Detection limit of the method was 0.2 ng/mL and the Relative Standard Deviation (RSD) for 3 and 70 ng/mL of silver ion was 3.5 and 1.7 (n=10), respectively. The enrichment factor was 54. The method was successfully applied to the determination of trace amounts of Ag(I) in radiology film and environmental matrices.

Effervescence assisted dispersive liquid–liquid microextraction followed by microvolume UV-Vis spectrophotometric determination of surfactants in water

ABSTRACTThe novel and simple methods for the sensitive determination of cationic and anionic surfactants in water based on effervescence assisted dispersive liquid–liquid microextraction and microvolume UV-Vis spectrophotometry have been developed. The method involves ion-pair extraction of cationic and anionic surfactants with organic dyes (methyl orange and azure A, respectively) during the dispersion of extraction solvent (CHCl3) by CO2 bubbles which are formed by the injection of a mixture of the extraction solvent and proton donor solvent into the sample solution which contains carbonate-ions as effervescency agent. The analytical performance of the proposed procedure was compared with the conventional dispersive liquid–liquid microextraction. Appropriate experimental conditions for both methods were investigated. The absorbances of the colored extracts at wavelengths of 440 and 625 nm obey Beer's law within the range of 0.1–5.0 mg/L for both cationic and anionic surfactants. The limit of detection (LOD) obtained using the effervescence assisted extraction method was 30 µg/L for cationic and anionic surfactants. The proposed methods were successfully applied to determination of surfactants in water samples.

Enhanced spectrophotometric detection of Hg in water samples by surface plasmon resonance of Au nanoparticles after preconcentration with vortex-assisted liquid-liquid microextraction

This article presents an efficient, simple, and cost-effective method for the determination of trace amounts of Hg by vortex-assisted liquid-liquid microextraction (VALLME) coupled to microvolume UV–Vis spectrophotometry. This method correlates changes in the intensity of localized surface plasmon resonance (LSPR) of tetraoctylammonium bromide (TOABr) coated Au nanoparticles (NPs) after interaction with Hg2+ ion. Spectroscopic measurements of the TOABr-coated Au NPs phase with particular absorption properties (strong and well-defined absorption bands) after analyte extraction by VALLME, provide an accurate and sensitive determination of Hg in water samples, comparable with measurements obtained by atomic absorption spectrometry (AAS). Different variables including sample volume, extraction time, and TOABr-coated Au NPs dispersion volume were carefully studied; final experimental conditions were 5mL, 120μL and 5min respectively. The limit of detection (LOD) was 0.8ngmL−1. The calibration curve was linear at concentrations between the limit of quantification (LOQ) (4.9ngmL−1) and up to at least 120ngmL−1 of Hg. The relative standard deviation for six replicate determinations of 20ngmL−1 of Hg was 4.7%. This method exhibited an excellent analytical performance in terms of selectivity and sensitivity and it was finally applied for Hg determination in spiked tap and mineral water samples.

UV-vis spectrophotometric determination of trinitrotoluene (TNT) with trioctylmethylammonium chloride as ion pair assisted and disperser agent after dispersive liquid–liquid microextraction

In the present study, a simple, fast and inexpensive method based on dispersive liquid–liquid microextraction (DLLME) prior to microvolume UV-vis spectrophotometry was developed for the preconcentration and determination of trinitrotoluene (TNT). The procedure is based on the color reaction of TNT in alkaline medium and extraction into CCl4 as an ion pair assisted by trioctylmethylammonium chloride, which also acts as a disperser agent. Experimental parameters affecting the DLLME method such as pH, concentration of sodium hydroxide, amount of trioctylmethylammonium chloride, type and volume of extraction solvent were investigated and optimized. Under the optimum conditions, the limit of detection (LOD) was 0.9ng/mL and the calibration curve was linear in the range of 3–200ng/mL. The relative standard deviation for 25 and 100ng/mL of TNT were 3.7% and 1.5% (n=6), respectively. The developed DLLME method was applied for the determination of TNT in different water and soil samples.

Optimization of Auxiliary Solvent Demulsification Microextraction for Determination of Cyanide in Environmental Water and Biological Samples by Microvolume UV-Vis Spectrophotometry

A new, simple, rapid and efficient solvent terminated-auxiliary solvent-dispersive liquid-liquid microextraction (ST-AS-DLLME) technique for determination of cyanide ions by microvolume UV-Vis spectrophotometry was developed. Effective parameters on the extraction and absorbance of cyanide were optimized using two optimization methods: fractional factorial design (FFD) and central composite design (CCD). Zinc(II) tetraphenylporphyrine (ZnTPP) was used as a selective cyanide receptor agent. Methyl isobutyl ketone (MIBK), ethanol and 1-butanol were used as extraction solvent, dispersive solvent and demulsifier solvent, respectively. The method shows very good selectivity in presence of other species. The analytical curve was linear in the range of 4.0-130 μg L -1 with a limit of detection of 1.0 μg L -1 . Relative standard deviation (RSD) of the method for ten replicate measurements of 100 μg L -1 of cyanide was 1.1%. The method was successfully applied for determination of cyanide in natural water and plasma samples with good spike recoveries.

Determination of total iron in water and foods by dispersive liquid–liquid microextraction coupled with microvolume UV–vis spectrophotometry

A novel microvolume UV–vis spectrophotometry method was proposed for the rapid determination of total iron coupling with an efficient pretreatment method known as dispersive liquid–liquid microextraction (DLLME). The basis of the method is a quantitative colorimetric reaction between ferrous iron and 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol (5-Br-PADAP) after the reduction of Fe(III) to Fe(II) by using ascorbic acid as reducing agent. Parameters related to the efficiency of microextraction, such as pH, complexant concentration, the volume ratio of disperser solvent and extraction solvent were discussed and optimized in detail. Under the optimized conditions, the absorbance was in proportion to iron concentration in the range of 5–400μgL−1 with a correlation coefficient (R) of 0.9993. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.5μgL−1 and 5.2μgL−1, respectively. The relative standard deviation (RSD) for samples were 1.37– 4.42% (n=3). Good recoveries of iron were obtained in the range of 95.4–103.2% in food samples, 96.9–103.6% in water samples and 98.8–102.3% in Certified Reference Material. The proposed method was rapid, reliable and high-selective for the determination of total iron in food and water samples.

Determination of fungicide carbendazim in water and soil samples using dispersive liquid-liquid microextraction and microvolume UV–vis spectrophotometry

This article presents a new and sensitive method for the determination of trace amounts of fungicide carbendazim by dispersive liquid–liquid microextraction (DLLME) combined with UV–vis spectrophotometry. The method is based on the reduction of Fe(III) to Fe(II) by carbendazim, its reaction with potassium ferricynide to form a blue product and extraction into CCL4 by DLLME technique using methyltrioctylammonium chloride (Aliquat 336) as a disperser agent. Under the established optimum conditions, the calibration graph was linear in the range of 5–600ngmL−1 of carbendazim with a limit of detection of 2.1ngmL−1. The relative standard deviations for eight replicate determinations of 50 and 300ngmL−1 of carbendazim were 3.9% and 1.0%, respectively. The proposed method was successfully applied to determination of carbendazim in soil and water samples.

Dispersive liquid–liquid microextraction for the microvolume spectrophotometric determination of bismuth in pharmaceutical and human serum samples

A new dispersive liquid–liquid microextraction (DLLME) method coupled with microvolume UV-vis spectrophotometry was developed for the determination of trace amounts of bismuth.

Comparison of two novel in-syringe dispersive liquid–liquid microextraction techniques for the determination of iodide in water samples using spectrophotometry

Two new, rapid methodologies have been developed and applied successfully for the determination of trace levels of iodide in real water samples. Both techniques are based on a combination of in-syringe dispersive liquid–liquid microextraction (IS-DLLME) and micro-volume UV–Vis spectrophotometry. In the first technique, iodide is oxidized with nitrous acid to the colorless anion of ICl2- at high concentration of hydrochloric acid. Rhodamine B is added and by means of one step IS-DLLME, the ion-pair formed was extracted into toluene and measured spectrophotometrically. Acetone is used as dispersive solvent. The second method is based on the IS-DLLME microextraction of iodide as iodide/1, 10-phenanthroline-iron(II) chelate cation ion-pair (colored) into nitrobenzene. Methanol was selected as dispersive solvent. Optimal conditions for iodide extraction were determined for both approaches. Methods are compared in terms of analytical parameters such as precision, accuracy, speed and limit of detection. Both methods were successfully applied to determining iodide in tap and river water samples.

Dispersive liquid–liquid microextraction of thiram followed by microvolume UV–vis spectrophotometric determination

A novel and simple method for the sensitive determination of trace amounts of fungicide thiram is developed by combination of dispersive liquid–liquid microextraction (DLLME) and microvolume UV–vis spectrophotometry. The method is based on the conversion of thiram to a yellow product in the presence of ethanolic potassium hydroxide and copper sulfate, and its extraction into CCL4 using DLLME technique. In this method the ethanol existing in ethanolic KOH plays as disperser solvent and a cloudy solution is formed by injection of only CCl4 as extractant solvent into sample solution. Under the optimum conditions, the calibration graph was linear over the range of 25–1000ngmL−1 of thiram with limit of detection of 11.5ngmL−1. The relative standard deviation (RSD) for 100 and 500ngmL−1 of thiram was 2.7 and 1.1% (n=8), respectively. The proposed method was successfully applied to determination of thiram in water and plant seed samples.

Ion pair-based liquid-phase microextraction combined with cuvetteless UV–vis micro-spectrophotometry as a miniaturized assay for monitoring ammonia in waters

A miniaturized method based on liquid-phase microextraction (LPME) in combination with microvolume UV–vis spectrophotometry for monitoring ammonia in waters is proposed. The methodology is based on the extraction of the ion pair formed between the blue indophenol obtained according to the Berthelot reaction and a quaternary ammonium salt into a microvolume of organic solvent. Experimental parameters affecting the LPME performance such as type and concentration of the quaternary ammonium ion salt required to form the ion pair, type and volume of extractant solvent, effect of disperser solvent, ionic strength and extraction time, were optimized. A detection limit of 5.0μgL−1 ammonia and an enrichment factor of 30 can be attained after a microextraction time of 4min. The repeatability, expressed as relative standard deviation, was 7.6% (n=7). The proposed method can be successfully applied to the determination of trace amounts of ammonia in several environmental water samples.