Environmental Certified Reference Materials Research Articles

Environmental iodine speciation quantification in seawater and snow using ion exchange chromatography and UV spectrophotometric detection

The behaviour and distribution of iodine in the environment are of significant interest in a range of scientific disciplines, from health, as iodine is an essential element for humans and animals, to climate and air quality, to geochemistry. Aquatic environments are the reservoir for iodine, where it exists in low concentrations as iodide, iodate and dissolved organic iodine and in which it undergoes redox reactions. The current measurement techniques for iodine species are typically time-consuming, subject to relatively poor precision and require specialist instrumentation including those that require mercury as an electrode. We present a new method for measuring iodine species, that is tailored towards lower dissolved organic carbon waters, such as seawater, rainwater and snow, using ion exchange chromatography (IC) with direct ultra-violet spectrophotometric detection of iodide and without the need for sample pre-concentration. Simple chemical amendments to the sample allow for the quantification of both iodate and dissolved organic iodine in addition to iodide. The developed IC method, which takes 16 min, was applied to contrasting samples that encompass a wide range of aqueous environments, from Arctic sea-ice snow (low concentrations) to coastal seawater (complex sample matrix). Linear calibrations are demonstrated for all matrices, using gravimetrically prepared potassium iodide standards. The detection limit for the iodide ion is 0.12 nM based on the standard deviation of the blank, while sample reproducibility is typically <2% at >8 nM and ∼4% at <8 nM. Since there is no environmental certified reference material for iodine species, the measurements made on seawater samples using this IC method were compared to those obtained using established analytical techniques; iodide voltammetry and iodate spectrophotometry. We calculated recoveries of 102 ± 16% (n = 107) for iodide and 116 ± 9% (n = 103) for iodate, the latter difference may be due to an underestimation of iodate by the spectrophotometric method. We further compared a chemical oxidation and reduction of the sample to an ultra-violet digestion to establish the total dissolved iodine content, the average recovery following chemical amendments was 98 ± 4% (n = 92). The new method represents a simple, efficient, green, precise and sensitive method for measuring dissolved speciated iodine in complex matrices.

Development and characteristics of a new certified reference material for landfill cover soil analysis with extraction using dilute hydrochloric acid

A new environmental certified reference material (CRM) has been developed by the National Institute for Environmental Studies (NIES) to support research and development studies on trace heavy metals in landfill cover soils.

Comparison of acid extraction and total digestion methods for measuring Cd isotope ratios of environmental samples.

To evaluate the pretreatment processing for Cd isotope analysis of environmental samples, acid extractions and total digestions were examined with various environmental certified reference materials. Four certified reference material samples, including fly ash, polluted soil, domestic sludge, and industrial sludge, were digested by six different acid extraction and total digestion methods, and then Cd was separated to remove other matrix by anion-exchange column. The Cd recovery rates of the acid extraction methods were 2.6-89.1%, while those of the total digestion methods were 21.6-88.7%. In these results, the Cd recovery rates were dependent on the sample type. More than 80% of the Cd in the polluted soil and domestic sludge samples could be recovered regardless of the decomposition method, except one method. On the other hand, the Cd recovery rate from fly ash was low when total digestion was performed using a HF mixture, and the recovery rate by total digestion methods for industrial sludge was higher than that by acid extraction. In our results, Cd isotope ratios tended to be more positive by increasing the Cd recovery rates, suggesting that the light isotope of Cd was decomposed preferentially during the decomposition procedures. However, when more than 80% of the Cd in the samples was recovered, the Cd isotope ratios were determined to be similar. This indicated that at least 80% of the Cd should be recovered from environmental samples to accurately measure the Cd isotopic ratio of environmental samples.

Particle induced X-ray emission and Rutherford backscattering spectrometry for testing homogeneity of environmental certified reference material candidates

ABSTRACT Taking advantages of non-destructive techniques, between-bottles homogeneity tests were carried out in term of elemental composition of seven certified reference materials (CRMs) candidates using particle-induced X-ray emission technique (PIXE). A combination of PIXE and RBS techniques (Rutherford backscattering spectrometry) was also used for CRMs candidates having biological matrices. The CRMs candidates have the matrices of soil, sediment, dust, fish muscle, leaves and fruit, which will be certified for some major, minor and trace elements. One batch was produced for each CRM candidate, which included 80 bottles. Between-bottles homogeneity tests were performed for each CRM candidate using seven representative bottles. The repeatability of measurements by PIXE and RBS was examined. The relative standard deviations (RSD) and relative average deviation (RAD) of the elements contents were considered for variability assessment for both repeatability and between-bottles homogeneity. Al, Si and Fe showed good repeatability with RSD and RAD of <4%, while Mg, S, Cl, K, Ca, Mn and Sr showed RSD and RAD in the range of 4–10%. A content of one element in the examined CRMs candidates, with the exception of the date fruit, showed RSD and RAD of <5% indicating good between-bottles homogeneity. For date fruit, the relative error of all elements was <10%, with the exception of Si and Zn, while RAD of S, Cl and K were <10%.

Long-term stability test of elemental content in new environmental certified reference material candidates using ICP OES and ICP-SFMS

The need of certified reference materials (CRMs) is consistently growing due to various aspects in the environment and communities. A research project on the production of seven environmental CRMs with international collaboration has been proposed as a pilot study. The CRMs are intended to be applied for quality assurance of toxicological, environmental, and food analyses of matrices of soil, sediment, dust, leaves, date fruit, and edible fish muscle for some elements at macro-, micro-, and trace-levels. This article demonstrates stability tests, as an essential parameter for CRMs, of element content in CRMs using ICP OES and ICP-SFMS. Useful and simple approaches were proposed for stability assessment. Cluster analysis of stability revealed that Cu, Fe, Mn, and Al in CRMs of soil matrices were the most similar elements in term of stability; and likewise for Cu, Fe, and Mn in CRMs of biological matrices. An overall stability of all elements in each CRM was also assessed by paired samples t-test at confidence interval of 95%. The p values of all CRMs are all >.05 indicating no significant variation on elements contents before and after underwent storage, besides limited transport conditions. Despite this study presents a simple way for assessment of stability of elements concentrations in CRMs, further stability studies are required concerning several intervals to study the effect of conditions on stability.

Indicative properties measurements by SEM, SEM-EDX and XRD for initial homogeneity tests of new certified reference materials

This manuscript reports, for the first time, the use of SEM, EDX and XRD for initial homogeneity test of seven new environmental certified reference materials (CRMs), which are under development at our laboratories. The proposed CRMs, which will be certified for essential and toxic elements, are soil, dust, sediment, leaves, dates and fish. Between-bottles homogeneity test was carried out in terms of indicative properties of CRMs rather than the certified properties. SEM was used to test particle-size distribution. The major particle-size of CRMs of soil, dust, sediment, leaves and fish are 20–60, <20–60, 40–80, 50–100 and 70–100 μm, respectively. The ranges of the mean, standard deviation (SD) and mean deviation (MD) were 0.29–70.3%, 0.09–1.48 and 0.08–1.21, respectively. EDX was used to quantify the percentages of major elements (Si, O, N, S, Ca, Al, K, Fe, Mg, Zn and Cu). The percentage ranges of the mean, SD and MD for all elements were 1.57–48.15%, 0.11–5.84 and 0.09–4.4, respectively. XRD was used to quantify the percentages of the major minerals. The ranges of the mean, SD and MD were 1.57–48.15%, 0.11–5.84 and 0.09–4.40. All SD and MD values showed low level of dispersion indicating satisfactory homogeneity. Additionally, the relative standard deviation values of all dominant indicative properties did not exceed 10% confirming satisfactory homogeneity. SEM, EDX and XRD offered useful, rapid and simple measurements for initial homogeneity test of the CRMs.

Analysis of 6- and 7-ring PAH and other non-EPA PAH by atmospheric pressure laser ionization – mass spectrometry (APLI-MS) in environmental certified reference materials NIST 1941b, NIST 1649b, BAM CC013a and IRMM BCR 535

Proceedings in environmental analytical chemistry of polycyclic aromatic hydrocarbons (PAH) in the past decades cover improvements in laboratory methods as well as new insights in the toxicology of single PAH compounds. A re-evaluation of the established list of 16 priority PAH published by the U. S. Environmental Protection Agency seems overdue. In this study we have applied PAH analysis by atmospheric pressure laser ionization – mass spectrometry (APLI-MS) to NIST 1941b, NIST 1649b, BAM CC013a and IRMM BCR 535 giving further references in addition to the certificates of analysis. Gas chromatography enables to distinguish between different alkylated PAH derivatives whereas liquid chromatography additionally allows detection of PAH tentatively with six or more aromatic rings on the level of chemical formula. For an optimal isomer-specific differentiation, LC-APLI-MS should be used in combination with fluorescence detection. Distribution patterns of 6 and 7-ring PAH are presented for urban dust, marine and harbor sediments and the soil sample. Additionally, a set of 14 nitrogen, sulfur and oxygen-containing polycyclic aromatic compounds were analyzed by APLI and quantified in all reference materials for the first time.

Reference measurements of cadmium and lead contents in candidates for new environmental certified materials by isotope dilution inductively coupled plasma mass spectrometry

The analytical procedures for the reference measurements of cadmium and lead concentrations in four candidates for new environmental certified reference materials were developed. Cadmium and lead content was determined in bottom sediment (M-2 BotSed), Baltic herring tissue (M-3 HerTis), cormorant tissue (M-4 CormTis) and codfish tissue (M-5 CodTis). The measurements were carried out with the use of a direct isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The isotope dilution approach and the combined uncertainty of results are based on the mathematical equations as from definition of a primary method of measurement. All factors influencing the final results included: the procedural blank, the moisture content in the materials, the factors affecting the blend ratio measurements (instrumental background, spectral interferences, dead time, mass discrimination effects and the repeatability of measured isotopic ratios) as well as the isotopic equilibrium were systematically investigated and included in the uncertainty budget. The content of cadmium in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(110Cd)/n(111Cd) was found to be: (2.18 ± 0.06) μg g−1 in M-2 BotSed, (337 ± 2) ng g−1 in HerTis, (16.4 ± 0.6) ng g−1 in CormTis) and (2.7 ± 0.4) ng g−1 in CodTis, respectively. The content of lead in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(208Pb)/n(207Pb) was found to be: (108 ± 5) ng g−1 in M-3 HerTis, (2.34 ± 0.12) μg g−1 in M-4 CormTis and (43 ± 2) ng g−1 in M-5 CodTis, respectively. The Cd and Pb contents determined in this work were used as a contribution of the Faculty of Chemistry, Biological and Chemical Research Centre University of Warsaw in the characterisation of the abovementioned candidates for new certified reference materials in the frame of the Inter-Laboratory Comparison, organized by the Institute Nuclear Chemistry and Technology (Warsaw, Poland). The obtained excellent agreement within uncertainties with the reference values further validated the methods developed in this study.

Quantitative analysis of trace elements in environmental powders with laser ablation inductively coupled mass spectrometry using non-sample-corresponding reference materials for signal evaluation

Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an attractive alternative to traditional procedures for the analysis of environmental samples (i.e., conventional liquid measurement after sample digestion). However, for accurate quantification, certified reference materials (CRM) are necessary which match the composition of the sample and include all elements of interest at the required concentration levels. The limited availability of appropriate CRMs hampers therefore substantial application. In this work, an LA-ICP-MS procedure allowing for accurate determination of trace element contents in powdered environmental samples is presented. For LA-ICP-MS analysis, the samples are mixed with an internal standard (silver oxide) and a binder (sodium tetra borate) and subsequently pressed to pellets. Quantification is accomplished using a calibration function determined using CRMs with varying matrix composition and analyte content, pre-treated and measured in the same way as the samples. With this approach, matrix-induced ablation differences resulting from varying physical/chemical properties of the individual CRMs could be compensated. Furthermore, ICP-related matrix-effects could be minimized using collision/reaction cell technology. Applicability of the procedure has been demonstrated by assessment of Cd, Cu, Ni, and Zn in four different environmental CRMs (NIST SRM1648a (urban particulate matter), NIST SRM2709 (San Joaquin Soil), BCR144 (sewage sludge), and BCR723 (road dust)). Signal evaluation was performed by alternative use of three CRMs for calculation of the calibration function whereas the remaining fourth CRM acted as unknown sample, resulting in a good agreement between measured and certified values for all elements and reference materials.

Speciation of Chromium in Natural Waters, Tea, and Soil with Membrane Filtration Flame Atomic Absorption Spectrometry

A sensitive and selective method was developed for the speciation of chromium(III) and chromium(VI) in environmental samples based on membrane filtration and determination by flame atomic absorption spectrometry. Chromium(III) reacts with cochineal red A, yielding a complex that is adsorbed on a cellulose acetate membrane filter, whereas chromium(VI) remains in aqueous solution, permitting separation. After reduction of chromium(VI) to chromium(III) with hydroxylamine hydrochloride, the total concentration of chromium was determined, and the concentration of chromium(VI) was calculated by subtraction. The pH, amount of cochineal red A, and sample volume were optimized on the basis of the recovery of Cr(III). The influence of matrix ions was also investigated. The preconcentration factor was 94. The detection limit (3 sigma) for Cr(III) was 1.4 micrograms per liter. The method was validated using environmental certified reference materials. The method was successfully employed for the speciation of chromium in wastewater and lake water.

Metal ion-assisted photochemical vapor generation for the determination of lead in environmental samples by multicollector-ICPMS.

A novel and sensitive approach for the accurate and precise determination of Pb in environmental samples is presented using transition metal ion-assisted photochemical vapor generation (PVG) for sample introduction with multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) detection. A significant improvement in PVG efficiency of lead is achieved in the presence of transition metal ions (Co(2+) and Ni(2+)) in solutions of 5% (v/v) formic acid. The determination of Pb in digests of sediment or soil samples is readily achieved due to coexisting transition metal ions which facilitate the PVG reaction. The method detection limit of 0.005 ng g(-1) (3σ) using external calibration is comparable to that obtained using hydride generation (HG) ICPMS. However, PVG methodology is simpler, results in lower blanks, and avoids unstable reagents. The accuracy of the proposed method was demonstrated by analysis of several environmental certified reference materials (CRMs; SLRS-5 and SRM1640a river water CRMs and MESS-3, MESS-4, and SRM2702 sediments) with satisfying results. High precision of determination (<0.4% RSD) of Pb in river water and sediments was realized on the basis of isotope dilution calibration.

Ultrasonic Nebulization, Multimode Sample Introduction System for Simultaneous Determination of Hydride-Forming, Cold Vapor, and Non-Hydride-Forming Elements by Microwave-Induced Plasma Spectrometry

ABSTRACT A novel synergic effect of ultrasonic nebulization (USN) and a multimode sample introduction system (MSIS) when used in combination has been exploited for efficient generation of conventional hydride-forming (As, Bi, Ge, Sb, Se, Sn), Hg vapor, and non-hydride-forming (Ba, Ca, Li, Mg, Sr) elements. The ultrasonic nebulizer supplied a microliter sample to a quartz oscillator, converting liquid into aerosol at the entrance of the MSIS spray chamber. The argon carrier gas is passed to remove and transport the generated vapor species (from the MSIS) and aerosol (from the USN) to a microwave-induced plasma (MIP) for simultaneous element determination by optical emission spectrometry (OES). The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 0.3, 1.5, 1.9, 0.5, 1.7, 0.6, 0.8, 9, 1.6, 1.9, 2.2, and 2.9 ng mL−1 for As, Bi, Ge, Sb, Se, Sn, Hg, Ba, Ca, Li, Mg, and Sr, respectively. The method offers relatively good precision (RSD ranged from 5% to 9%) for liquid analysis and microsampling capability. The methodology was validated through determination of elements in four certified reference materials (NIST 2710, NRC GBW 07302, NRCC DOLT-2, NIST 1643e) and by the aqueous standard calibration technique. Good agreement with certified values was obtained when this approach was applied to the determination of hydride-forming, cold vapor, and other elements in biological and environmental certified reference materials.

Developments of Environmental Certified Reference Material from the Brazilian Metrology Institute to Support National Traceability

This paper aims to present the developments performed by the Brazilian Metrology Institute (NMI) – Inmetro, considering the environmental demand. Inmetro addresses great part of its activities to the study of the traceability transference based on production and dissemination of certified reference material (CRM) of different areas in chemistry. It will be presented results from certification of the following reference materials developed: BTEX and PAH in solution, besides automotive emission gas mixtures and bioethanol. So, the achievements made are the growth in developing CRM, in order to support the needs of the national industry and to disseminate traceability among the society.

Combination of a multimode sample introduction system with a pre-evaporation tube to improve multi-element analysis by ICP-OES

A pre-evaporation tube (heated to 400 °C) was inserted between a multi-mode sample introduction system (MSIS) and the plasma torch in inductively coupled plasma optical emission spectrometry (ICP-OES) to improve the simultaneous determination of hydride-forming and other elements. Multivariate optimisations were conducted to find operating conditions improving plasma robustness. Under these conditions and compared to conventional sample introduction with a pneumatic nebulizer and spray chamber, using MSIS with a pre-evaporation tube (PET) improved sensitivity and detection limits for hydride-forming elements (As, Sn, Hg, Sb and Bi) and other elements as well. In order to obtain a significant improvement for all elements, irrespective of hydride formation or not, the pneumatic nebulizer was replaced by an ultrasonic nebulizer (USN) and the same experimental conditions were used for the simultaneous introduction of aerosol and hydrides (from the MSIS) into a PET. With USN-MSIS-PET, the figures of merit of ICP-OES improved by over an order of magnitude for both hydride-forming elements and other elements compared to those with a conventional sample introduction system. Furthermore, using either PN-MSIS-PET or USN-MSIS-PET increased plasma robustness, likely as a result of the hydrogen gas by-product of hydride generation, which was reported to increase energy transfer within the plasma, and from the introduction of water vapor (with PET), which was reported to improve plasma stability as well as sensitivity. Good agreement with certified values was obtained when this approach was applied to the determination of hydride-forming and other elements in environmental certified reference materials.

Improving the analytical performances of ICP-AES by using a high-temperature single-pass spray chamber and segmented-injections micro-sample introduction for the analysis of environmental samples

A new method based on the use of a high-temperature single-pass spray chamber and the injection of a sample plug into an air carrier gas stream was developed to mitigate non-spectral interferences caused by inorganic concomitants and to reduce plasma loading in inductively coupled plasma atomic emission spectrometry (ICP-AES). The evaluated sample introduction systems were a 10 cm3 inner-volume single-pass spray chamber (also called the Torch Integrated Sample Introduction System, TISIS) with and without heating and a cinnabar spray chamber, taken as a reference device. The temperature of the spray chamber was raised up to 350 °C. Sensitivity, memory effects, limits of detection and non-spectral interferences were evaluated. The results proved that the higher the chamber walls temperature, the higher the peak height and the lower the memory effects. The single-pass spray chamber heated at 350 °C provided lower limits of detection (0.3–2.3 μg l−1) compared with the reference spray chamber (1–33 μg l−1) and a significant reduction of matrix effects. This device was successfully applied to the analysis of environmental certified reference materials, such as marine sediments and animals. The calibration curve was obtained by modifying the mass of the analyte injected, thus requiring only one standard solution. The results were also compared with those obtained by external calibration (both at room temperature and at 350 °C) and single-point standard addition. The analytical bias was lower than 5%, showing that this sample introduction system is adequate to remove the matrix effects due to inorganic concomitants, allowing the accurate analysis of environmental samples.

Low power capacitively coupled plasma microtorch for simultaneous multielemental determination by atomic emission using microspectrometers

A new, low power capacitively coupled plasma microtorch (30 W, 13.56 MHz, 0.5 L min −1 Ar) was investigated in conjunction with commercially available microspectrometers for the simultaneous multielemental analysis by atomic emission spectrometry of liquid samples without desolvation. Emission spectrum is simpler than in ICP-AES, the resonance lines are the most intense, so that a microspectrometer with FWHM of at least 1.5 nm is satisfactory for the record. The deviation from the Boltzmann distribution for Fe I has demonstrated the departure from the LTE in plasma. The non-spectral matrix effects of Li, Na, K, Ca and Mg on analytes emission are depressive and depend on matrix volatility, ionization potential of the interferent and analyte excitation energy. The detection limits (μg mL −1) are in the range 0.003 (Li) and 1.5 (Mn). The use of the standard additions method allowed the simultaneous determination of elements in environmental certified reference materials with overall recovery of 95 ± 10% and relative standard deviation of 1.7–8.2%. Compared to the traditional ICP, the microtorch has a simple construction, runs at low argon flow and can be integrated in a portable system suitable for in-situ simultaneous determination of elements.

High-Yield UV-Photochemical Vapor Generation of Iron for Sample Introduction with Inductively Coupled Plasma Optical Emission Spectrometry

A novel approach to the generation of volatile iron compounds (likely the pentacarbonyl) with high efficiency is described, wherein solutions containing either Fe(2+) or Fe(3+) and low molecular weight organic acids such as formic, acetic or propionic are exposed to a UV source. An optimum generation efficiency of 60 +/- 2% was achieved in 50% formic acid at pH 2.5 with an irradiation time of 250 s by use of a 17 W low-pressure mercury grid lamp. Compared to conventional solution nebulization, sensitivity and limit of detection were improved 80- and 100-fold, respectively, at the 238.204 nm Fe II emission line. A precision of 0.75% RSD was achieved at a concentration of 100 ng/mL. Photochemical vapor generation sample introduction was used for the determination of trace iron in several environmental Certified Reference Materials, including National Research Council Canada DORM-3 fish muscle tissue, DOLT-3 and DOLT-4 fish liver tissues, and SLRS-5 river water, providing analytical results in excellent agreement with certified values based on a simple external calibration.

Characterization of NIES CRM No. 23 Tea Leaves II for the determination of multielements

A candidate environmental certified reference material (CRM) for the determination of multielements in tea leaves and materials of similar matrix, NIES CRM No. 23 Tea Leaves II, has been developed and characterized by the National Institute for Environmental Studies (NIES), Japan. The origin of the material was tea leaves, which were ground, sieved through a 106-microm mesh, homogenized, and then subdivided into amber glass bottles. The results of homogeneity and stability tests indicated that the material was sufficiently homogeneous and stable for use as a reference material. The property values of the material were statistically determined based on chemical analyses by a network of laboratories using a wide range of methods. Sixteen laboratories participated in the characterization, and nine certified values and five reference values were obtained. These property values of the candidate CRM, which are expressed as mass fractions, were close to the median and/or mean values of the mass fractions of elements in various tea products. The candidate CRM is appropriate for use in analytical quality control and in the evaluation of methods used in the analysis of tea and materials of similar matrix.

Development and certification of the new NIES CRM 28: urban aerosols for the determination of multielements

A new environmental certified reference material (CRM) for the determination of multielements in aerosol particulate matter has been developed and certified by the National Institute for Environmental Studies (NIES), Japan, based on analyses by a network of laboratories using a wide range of methods. The origin of the material was atmospheric particulate matter collected on filters in a central ventilating system in a building in Beijing city centre. The homogeneity and stability of this material were sufficient for its use as a reference material. Values for elemental mass fractions in the material were statistically determined based on the analytical results of the participating laboratories. Eighteen certified values and 14 reference values were obtained. The diameters, obtained from a micrographic image using image analysis software, of 99% of the particles were less than 10 microm, demonstrating that almost all the particles in the material could be classified as particles of 10 microm or less in aerodynamic diameter. The chemical composition and particle size distribution of this material were close to those of an authentic aerosol collected in Beijing. NIES CRM 28 is appropriate for use in analytical quality control and in the evaluation of methods used in the analysis of aerosols, particularly those collected in urban environments in northeast Asia.

Flow injection determination of aluminium by spectrofluorimetric detection after complexation with N- o-vanillidine–2-amino- p-cresol: The application to natural waters

An on-line flow injection spectrofluorimetric method for the direct determination of aluminium in water samples is described. The method is based on the reaction of aluminium with N- o-vanillidine–2-amino- p-cresol (OVAC) in acidic medium at pH 4.0 to form a water-soluble complex. The excitation and emission wavelengths were 423.0 and 553.0 nm, respectively, at which the OVAC–Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% methanol–50% water medium at 50 °C. An interference from fluoride ions was minimised by the addition of Be 2+. Other ions were found not to interfere at the concentrations likely to be found in natural waters. The proposed methods were validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Under these conditions, the calibration was linear up to 1000 μg L −1 ( r = 0.999). The limit of detection (3 σ) for the determination of Al(III) was 0.057 μg L −1 and the precision for multiple determinations of 3 ng mL −1 Al(III) prepared in ultra-pure water was found to be 0.62% ( n = 10). The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both freshwater and saline solutions, including seawater.