Determination of free glycerol in biodiesel at a platinum oxide surface using potential cycling technique

A novel, inexpensive and fast method based on the electrooxidation of glycerol on platinum electrodes by the potential cycling technique has been designed for the determination of free glycerol in biodiesel. A wide range of linearity was achieved between 15 and 150 mg L⁻¹ (0.16 and 1.6 mmol L⁻¹), which corresponds to concentrations ranging between 56 and 560 mg kg⁻¹ (glycerol:biodiesel) for an extraction using 2 g biodiesel. A method for the fast extraction of glycerol from biodiesel with water followed by elimination of organic interferents has also been developed, so that the novel determination method can be applied to various biodiesel samples. The excellent repeatability allows determination of glycerol in numerous samples, with no need for recalibration.     

A quick method for the simultaneous determination of ascorbic acid and sorbic acid in fruit juices by capillary zone electrophoresis

A method of quickly determining ascorbic acid and sorbic acid by capillary zone electrophoresis with ultraviolet detection was developed. The choice of background electrolyte, wavelength, injection time and applied voltage were discussed. Ascorbic acid and sorbic acid were well separated in 80 mmol L⁻¹ boric acid-5 mmol L⁻¹borax (pH = 8.0) in 5 min at the detecting wavelength of 270 nm. Under the optimum condition, the method has linear ranges of 2.54-352.00 mg L⁻¹ for ascorbic acid and 1.08-336.39 mg L⁻¹ for sorbic acid with the detection limit of 1.70 mg L⁻¹ for ascorbic acid and 0.54 mg L⁻¹ for sorbic acid, respectively. Other organic acids in fruit juices have no effect on the detection. This method is very feasible and simple and can be used to detect ascorbic acid and sorbic acid in fruit juices.     

Simultaneous determination of first-line anti-tuberculosis drugs by capillary zone electrophoresis using direct UV detection

An alternative methodology for simultaneous analysis of ethambutol, isoniazid, rifampicin and pyrazinamide in pharmaceutical formulations by capillary zone electrophoresis under UV direct detection with an analysis time of 8.0 min is proposed. Background running was based on the effective mobility curve of the analytes and an optimum separation condition was achieved using a 3³ Box-Behnken design, with Brij 35, Cu²⁺ and acetic acid/sodium acetate buffer as factors. An electrolyte consisting of 50.0 mmol L⁻¹ of acetic acid/sodium acetate buffer, 12.5 mmol L⁻¹ of CuSO₄, and standard and sample solutions prepared in 2.00 mmol L⁻¹ of Brij 35 and 12.5 mmol L⁻¹ of CuSO₄ were optimized. After evaluating validation parameters, the method was successfully applied to the analysis of samples in the form of tablets and sachets.     

Determination of sodium,potassium, calcium and magnesium cations in biodiesel by ion chromatography

This work reports an ion chromatographic (IC) method for the quantitative determination of inorganic cations (Na⁺, K⁺, Mg²⁺ and Ca²⁺) in biodiesel samples that were synthesized from different vegetable oils and fat. The proposed method uses water extraction, heating and ultrasound. The limits of detection (LOD) for each ion, in milligrams of the analyte per kilogram of biodiesel (mg kg⁻¹), were respectively: 0.11 (Na⁺); 0.42 (K⁺); 0.23 (Ca²⁺); and 0.36 (Mg²⁺). The accuracy of the method was studied through recovery tests. For comparison, two samples were also analyzed using an Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) procedure. The paired Student t test and the Snedecor F test showed that both methods offer equivalent results in terms of accuracy and precision. The operational simplicity, accuracy and precision of the proposed method suggest that it can be a good alternative for the determination of inorganic cations in biodiesel samples.     

Determination of trace sulfur in biodiesel and diesel standard reference materials by isotope dilution sector field inductively coupled plasma mass spectrometry

A method is described for quantification of sulfur at low concentrations on the order of mg kg⁻¹ in biodiesel and diesel fuels using isotope dilution and sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). Closed vessel microwave-assisted digestion was employed using a diluted nitric acid and hydrogen peroxide decomposition medium to reduce sample dilution volumes. Medium resolution mode was employed to eliminate isobaric interferences at ³²S and ³⁴S related to polyatomic phosphorus and oxygen species, and sulfur hydride species. The method outlined yielded respective limits of detection (LOD) and limits of quantification (LOQ) of 0.7 mg kg⁻¹ S and 2.5 mg kg⁻¹ S (in the sample). The LOD was constrained by instrument background counts at ³²S but was sufficient to facilitate value assignment of total S mass fraction in NIST SRM 2723b Sulfur in Diesel Fuel Oil at 9.06 ± 0.13 mg kg⁻¹. No statistically significant difference at a 95% confidence level was observed between the measured and certified values for certified reference materials NIST SRM 2773 B100 Biodiesel (Animal-Based), CENAM DRM 272b and NIST SRM 2723a Sulfur in Diesel Fuel Oil, validating method accuracy.     

Isotachophoretic determination of hydrosulfite and metabisulfite in technical samples

A method for determination of metabisulfite and hydrosulfite in poultice and decolorant by isotachophoresis was developed. Metabisulfite and hydrosulfite are ionizable oxoanions of sulfur of similar character that can easily be oxidized to sulfates. To protect the analytes from oxidation the solid samples were dissolved in a 1% (w/v) solution of formaldehyde. Hydrosulfite and metabisulfite present in the samples were transformed by the reaction with formaldehyde to stable compounds, hydroxymethanesulfinate and hydroxymethanesulfonate that were determined isotachophoretically without any pretreatment except for sample filtering and degassing. A capillary of 0.4 mm i.d. and 100 mm effective length made of fluorinated ethylene-propylene copolymer was filled with an electrolyte system consisting of 10 mmol L⁻¹ HCl + 11 mmol L⁻¹ imidazole, 0.15% (w/v) hydroxyethylcellulose, pH 6.0 (leading electrolyte) and 5 mmol L⁻¹ benzoic acid + 6 mmol L⁻¹ imidazole, pH 6.5 (terminating electrolyte). Separation was performed at a driving current of 80 μA and for detection current was decreased to 30 μA. Using contactless conductivity detection, the calibration curves in the tested concentration range up to 2.5 mmol L⁻¹ were linear for both metabisulfite and hydrosulfite complexes. The concentration detection limits for metabisulfite and hydrosulfite were 2.9 and 3.4 μmol L⁻¹, respectively. For 1 mmol L⁻¹ concentration, values of R.S.D. (n = 6) were 2.6% for hydrosulfite and 0.8% for metabisulfite. Isotachophoretic determination took about 20 min. The elaborated isotachophoretic procedure is simple to perform, sufficiently sensitive and accurate. In addition to this, low cost of analyses makes the method an alternative procedure to methods used so far for the determination of oxoanions of sulfur.     

Determination of aminoglutethimide enantiomers in pharmaceutical formulations by capillary electrophoresis using methylated-β-cyclodextrin as a chiral selector and computational calculation for their respective inclusion complexes

A capillary electrophoretic method for the separation of the aminoglutethimide (AGT) enantiomers using methylated-β-cyclodextrin (M-β-CD) as chiral selector is described. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 9 min with resolution factor Rs = 2.1, using a fused-silica capillary and a background electrolyte (BGE) of tris-phosphate buffer solution (50 mmol L⁻¹, pH 3.0) containing 30 mg mL⁻¹ of M-β-CD. The separation was carried out in normal polarity mode at 25 °C, 16 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy/recovery were included. The proposed method was successfully applied to the assay of AGT enantiomers in pharmaceutical formulations. The computational calculations for the inclusion complexes of the R- and S-AGT-M-β-CD rationalized the reasons for the different migration times between the AGT enantiomers.     

Development of a fast capillary electrophoresis method for the determination of propranolol—Total analysis time reduction strategies

The aim of this study was to develop a fast capillary electrophoresis method for the determination of propranolol in pharmaceutical preparations. In the method development the pH and constituents of the background electrolyte were selected using the effective mobility versus pH curves. Benzylamine was used as the internal standard. The background electrolyte was composed of 60 mmol L⁻¹ tris(hydroxymethyl)aminomethane and 30 mmol L⁻¹ 2-hydroxyisobutyric acid, at pH 8.1. Separation was conducted in a fused-silica capillary (32 cm total length and 8.5 cm effective length, 50 μm I.D.) with a short-end injection configuration and direct UV detection at 214 nm. The run time was only 14 s. Three different strategies were studied in order to develop a fast CE method with low total analysis time for propranolol analysis: low flush time (Lflush) 35 runs/h, without flush (Wflush) 52 runs/h, and Invert (switched polarity) 45 runs/h. Since the three strategies developed are statistically equivalent, Wflush was selected due to the higher analytical frequency in comparison with the other methods. A few figures of merit of the proposed method include: good linearity (R² > 0.9999); limit of detection of 0.5 mg L⁻¹; inter-day precision better than 1.03% (n = 9) and recovery in the range of 95.1–104.5%.     

A flow injection procedure based on solenoid micro-pumps for spectrophotometric determination of free glycerol in biodiesel

A flow system designed with solenoid micro-pumps is proposed for fast and greener spectrophotometric determination of free glycerol in biodiesel. Glycerol was extracted from samples without using organic solvents. The determination involves glycerol oxidation by periodate, yielding formaldehyde followed by formation of the colored (3,5-diacetil-1,4-dihidrolutidine) product upon reaction with acetylacetone. The coefficient of variation, sampling rate and detection limit were estimated as 1.5% (20.0 mg L⁻¹ glycerol, n = 10), 34 h⁻¹, and 1.0 mg L⁻¹ (99.7% confidence level), respectively. A linear response was observed from 5 to 50 mg L⁻¹, with reagent consumption estimated as 345 μg of KIO₄ and 15 mg of acetylacetone per determination. The procedure was successfully applied to the analysis of biodiesel samples and the results agreed with the batch reference method at the 95% confidence level.     

Accelerated solvent-based extraction and enrichment of selected plasticisers and 4-nonylphenol, and extraction of tin from organotin sources in sediments, sludges and leachate soils

Enrichment techniques have become an important feature in the trace analysis of oestrogen mimicking chemicals in the environment. Recent developments such as accelerated solvent extraction (ASE) have improved extraction recoveries in a wide variety of solid matrices including sediments, sludges and leachate soils. Such samples taken from the Irish Midlands Shannon Catchment region during the winter of 2004/5 and suspected to contain certain xenooestrogens or hormonally active agents were extracted using this technique, which was then coupled with high performance liquid chromatography (HPLC) for quantification purposes. ASE was thus employed to both isolate and pre-concentrate targeted analytes using the minimum amount of solvent hence making extractions more conservational. Two simple, yet extremely sensitive liquid chromatographic methods were developed based on UV detection; one for phthalates and one for alkylphenols, with recoveries reaching up to 92.0%. Acid digestion was used for the extraction of the tin and organotin compounds with analysis by polarography. In river sediment, levels of up to 24.4 mg kg⁻¹ phthalate, 1.14 mg kg⁻¹ 4-nonylphenol and 118 mg kg⁻¹ tin were found. In leachate sediments, values up to 49.8 mg kg⁻¹ phthalate, 1.57 mg kg⁻¹ 4-nonylphenol, and 36.0 mg kg⁻¹ tin were determined. In sludge, values up to 174 mg kg⁻¹ phthalate and 22.8 mg kg⁻¹ 4-nonylphenol were quantified. The highest value of tin (118 mg kg⁻¹) was found present in an area of high leisure craft activity. Typical sediment levels of tin at other river locations ranged between 1.20 and 37.5 mg kg⁻¹.     

Determination of selenium using atomically imprinted polymer (AIP) and hydride generation atomic absorption spectrometry

This paper describes selenium determination based on Se⁰ preconcentration in the imprinted polymer (synthesized with 2.25 mmol SeO₂, 4-vinylpyridine and 1-vinylimidazole) with subsequent detection on-line in HG-FAAS. During the synthesis, SeO₂ is reduced to Se (0). Therefore, there are no MIP neither IIP in the present work, thus we denominated: AIP, i.e., atomically imprinted polymers. For the optimization of analytical parameters Doehlert design was used. The method presented limit of detection and limit of quantification of 53 and 177 ng L⁻¹, respectively, and linear range from 0.17 up to 6 μg L⁻¹ (r = 0.9936). The preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were 232; 0.06 mL and 58 min⁻¹ respectively. The proposed method was successfully applied to determine Se in Brazil nuts (0.33 ± 0.03 mg kg⁻¹), apricot (0.46 ± 0.02 mg kg⁻¹), white bean (0.47 ± 0.03 mg kg⁻¹), rice flour (0.47 ± 0.02 mg kg⁻¹) and milk powder (0.22 ± 0.01 mg kg⁻¹) samples. It was possible to do 12 analyzes per hour. Accuracy was checked and confirmed by analyzing certified reference material (DORM-2, dogfish muscle), and samples precision was satisfactory with RSD lower than 10%.     

Direct determination of sodium,potassium, chromium and vanadium in biodiesel fuel by tungsten coil atomic emission spectrometry

High levels of sodium and potassium can be present in biodiesel fuel and contribute to corrosion, reduced performance and shorter engine lifetime. On the other hand, trace amounts of chromium and vanadium can increase the emission of pollutants during biodiesel combustion. Sample viscosity, immiscibility with aqueous solutions and high carbon content can compromise biodiesel analyzes. In this work, tungsten filaments extracted from microscope light bulbs are used to successively decompose biodiesel's organic matrix, and atomize and excite the analytes to determine sodium, potassium, chromium and vanadium by tungsten coil atomic emission spectrometry (WCAES). No sample preparation other than simple dilution in methanol or ethanol is required. Direct analysis of 10-μL sample aliquots using heating cycles with less than 150 s results in limits of detection (LOD) as low as 20, 70, 70 and 90 μg kg⁻¹ for Na, K, Cr and V, respectively. The procedure's accuracy is checked by determining Na and K in a biodiesel reference sample and carrying out spike experiments for Cr and V. No statistically significant differences were observed between reference and determined values for all analytes at a 95% confidence level. The procedure was applied to three different biodiesel samples and concentrations between 6.08 and 95.6 mg kg⁻¹ for Na and K, and between 0.22 and 0.43 mg kg⁻¹ for V were obtained. The procedure is simple, fast and environmentally friendly. Small volumes of reagents, samples and gases are used and no residues are generated. Powers of detection are comparable to other traditional methods.     

Mineral content and botanical origin of Spanish honeys

Eleven elements (Zn, P, B, Mn, Mg, Cu, Ca, Ba, Sr, Na and K) were determined by inductively plasma coupled spectrometry in 40 honey samples from different places of Spain and four different botanical origins: Eucalyptus (Eucalyptus sp.), Heather (Erica sp.), Orange-blossom (Citrus sinensis) and Rosemary (Rosmarinus officinalis). K, Ca and P show the higher levels with average concentrations ranged between 434.1-1935 mg kg⁻¹ for K; 42.59-341.0 mg kg⁻¹ for Ca and 51.17-154.3 mg kg⁻¹ for P. Levels of Cu (0.531-2.117 mg kg⁻¹), Ba (0.106-1.264 mg kg⁻¹) and Sr (0.257-1.462 mg kg⁻¹) are the lowest in all honey samples. Zn (1.332-7.825 mg kg⁻¹), Mn (0.133-9.471 mg kg⁻¹), Mg (13.26-74.38 mg kg⁻¹) and Na (11.69-218.5 mg kg⁻¹) concentrations were found strongly dependent on the kind of botanical origin.Results were submitted to pattern recognition procedures, unsupervised methods such as cluster and principal components analysis and supervised learning methods like linear discriminant analysis in order to evaluate the existence of data patterns and the possibility of differentiation of Spanish honeys from different botanical origins according to their mineral content. Cluster analysis shows four clusters corresponding to the four botanical origins of honey and PCA explained 71% of the variance with the first two PC variables. The best-grouped honeys were those from heather; eucalyptus honeys formed a more dispersed group and finally orange-blossom and rosemary honeys formed a less distinguishable group.     

Determination of metal content in some herbal drugs-Empirical and chemometric approach

The concentrations of Cu, Zn, Mn, Fe, K, Ca, Mg, Al, Ba and B in 26 herbal drugs of special importance in phytopharmacy were studied. Flame atomic absorption and emission spectrometry (FAAS, FAES), as well as inductively coupled plasma atomic emission spectrometry (ICP-AES), were applied in this work. The whole procedure, from sample preparation, via dissolution, to measurements, was validated by using CRM (NIST 1573a—tomato leaves), and the obtained recovery values are in the range from 91 to 102%. Drug samples originated from medicinal plants cultivated in Serbia contained Cu (4.47-14.08 mg kg⁻¹), Zn (8.4-54.5 mg kg⁻¹), Mn (9-155 mg kg⁻¹), Fe (47-546 mg kg⁻¹), K (0.20-6.24%), Ca (0.18-1.84%), Mg (0.13-1.09%), Al (16-416 mg kg⁻¹), Ba (11.70-84.83 mg kg⁻¹) and B (5.1-118.7 mg kg⁻¹). In order to get a better insight into the elemental patterns, a common chemometric approach to data evaluation was used. Four significant factors identified by principal component analysis (PCA) were attributed partly to the significant influential sources and high mobility of some elements thus referring to potential anthropogenic contamination as well.     

Micellar electrokinetic biofluid analysis of biogenic amines using on-line sample concentration and UV laser-induced native fluorescence detection

A simple and sensitive sweeping micellar electrokinetic chromatography method coupled with UV laser-induced native fluorescence detection has been developed for quantitative analysis of biogenic amines in biofluids. The background electrolyte comprised 30 mmol L⁻¹ phosphoric acid and 20 mmol L⁻¹ sodium dodecyl sulfate. The concentration limits of detection of analytes using sweeping-micellar electrokinetic chromatography (sweeping-MEKC) were in the range 7–100 nmol L⁻¹, which were 250–3600-fold improvement for dopamine, DOPA and epinephrine compared with conventional capillary zone electrophoresis. An improvement of approximately 20-fold was observed for all analytes compared with typical micellar electrokinetic chromatography conditions. Baseline separation was achieved for the all analytes within 12 min and migration-time and peak-area repeatability were better than RSD 0.35% and 5.68%, respectively. The developed method was applied to measure the biogenic amines in biofluids extracted from wheat phloem sap, human plasma and human urine.     

Development of new reference materials for the determination of cadmium,chromium, mercury and lead in polycarbonate

Reference materials for quantitative determination of Cd, Cr, Hg and Pb in polycarbonate were developed. Reference materials with two concentration level of elements were prepared by adding appropriate amounts of chemicals to a blank polycarbonate base material. It was shown that ten bottles with triplicate analysis are enough to demonstrate the homogeneity of these candidate reference materials. The statistical results also showed no significant trends in both short-term stability test for four weeks and long-term stability test for twelve months. The certification of the four elements was carried out by isotope-dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS) with microwave-assisted digestion. Certification of candidate reference materials in a single laboratory was confirmed with interlaboratory comparison participated by a certain number of well-recognized testing laboratories in Korea. The certified values and expanded uncertainties (k = 2) for the candidate reference material with low level and the one with high level were (51.7 ± 2.1) mg kg⁻¹ Cd, (103.8 ± 2.9) mg kg⁻¹ Cd, (98.8 ± 4.5) mg kg⁻¹ Cr, (1004 ± 49.8) mg kg⁻¹ Cr, (107.4 ± 4.6) mg kg⁻¹ Hg, (1133 ± 50.7) mg kg⁻¹ Hg, (94.8 ± 3.7) mg kg⁻¹ Pb and (988.4 ± 53.6) mg kg⁻¹ Pb, respectively. The reference materials developed in this study demonstrated their suitability for the quality assurance in Cd, Cr, Hg and Pb analysis for the implementation of RoHS Directive.     

Development and validation of ultra-high performance supercritical fluid chromatography method for determination of illegal dyes and comparison to ultra-high performance liquid chromatography method

A novel simple, fast and efficient ultra-high performance supercritical fluid chromatography (UHPSFC) method was developed and validated for the separation and quantitative determination of eleven illegal dyes in chili-containing spices. The method involved a simple ultrasound-assisted liquid extraction of illegal compounds with tetrahydrofuran. The separation was performed using a supercritical fluid chromatography system and CSH Fluoro-Phenyl stationary phase at 70 °C. The mobile phase was carbon dioxide and the mixture of methanol:acetonitrile (1:1, v/v) with 2.5% formic acid as an additive at the flow rate 2.0 mL min⁻¹. The UV–vis detection was accomplished at 500 nm for seven compounds and at 420 nm for Sudan Orange G, Butter Yellow, Fast Garnet GBC and Methyl Red due to their maximum of absorbance. All eleven compounds were separated in less than 5 min. The method was successfully validated and applied using three commercial samples of chili-containing spices – Chili sauce (Indonesia), Feferony sauce (Slovakia) and Mojo sauce (Spain). The linearity range of proposed method was 0.50–9.09 mg kg⁻¹ (r ≥ 0.995). The detection limits were determined as signal to noise ratio of 3 and were ranged from 0.15 mg kg⁻¹ to 0.60 mg kg⁻¹ (1.80 mg kg⁻¹ for Fast Garnet) for standard solution and from 0.25 mg kg⁻¹ to 1.00 mg kg⁻¹ (2.50 mg kg⁻¹ for Fast Garnet, 1.50 mg kg⁻¹ for Sudan Red 7B) for chili-containing samples. The recovery values were in the range of 73.5–107.2% and relative standard deviation ranging from 0.1% to 8.2% for within-day precision and from 0.5% to 8.8% for between-day precision. The method showed potential for being used to monitor forbidden dyes in food constituents. The developed UHPSFC method was compared to the UHPLC-UV method. The orthogonality of Sudan dyes separation by these two methods was demonstrated. Benefits and drawbacks were discussed showing the reliability of both methods for monitoring of studied illegal dyes in real food constituents.     

Electrospun nanofiber based colorimetric probe for rapid detection of Fe in water

An imidazole derivative, 2-(2′-pyridyl)imidazole (PIMH), was developed as a colorimetric probe for the qualitative analysis of Fe²⁺ in aqueous solution. PIMH was then used to post-functionalize poly(vinylbenzyl chloride) (PVBC) nanofibers after electrospinning so as to afford a solid state colorimetric probe. Upon treatment with Fe²⁺ the probe displayed a distinctive color change both in liquid and solid platforms. The linear dynamic range for the colorimetric determination of Fe²⁺ was 0.0988–3.5 μg mL⁻¹. The ligand showed a high chromogenic selectivity for Fe²⁺ over other cations with a detection limit of 0.102 μg mL⁻¹ in solution (lower than the WHO drinking water guideline limit of 2 mg L⁻¹), and 2 μg mL⁻¹ in the solid state. The concentration of Fe²⁺ in a certified reference material (Iron, Ferrous, 1072) was found to be 2.39 ± 0.01 mg L⁻¹, which was comparable with the certified value of 2.44 ± 0.12 mg L⁻¹. Application of the probe to real samples spiked with Fe²⁺ achieved recoveries of over 97% confirming accuracy of the method and its potential for on-site monitoring.     

The status of pesticide pollution in Tanzania

The paper summarises the findings of recent studies carried out to assess the levels of pesticide residues in water, sediment, soil and some biota collected from different parts of Tanzania. Although the intention is to cover the whole country, so far the studies have focused on areas with known large-scale pesticide use (Southern Lake Victoria and its basin, TPC sugar Plantations in Kilimanjaro region, Dar es Salaam coast, Mahonda-Makoba basin in Zanzibar) and a former pesticide storage area at Vikuge Farm in Coast region). Analysis of the cleaned extracts in GC-ECD/NPD revealed the dominance of organochlorines in all samples. Generally, low levels of residues were found in areas associated with agricultural pesticide use but the levels in the former storage areas were substantially high. DDT and HCH were dominant in all the studied areas. In the former areas, levels of ∑DDT in water, sediments and soil were up to 2 μg L⁻¹, 700 μg kg⁻¹ and 500 μg kg⁻¹, respectively, while those of ∑HCH were up to 0.2 μg L⁻¹, 132 μg kg⁻¹ and 60 μg kg⁻¹, respectively. The levels in aquatic biota were much higher than those in the water most likely due to bioaccumulation. In the former storage area at Vikuge the levels of pesticides in the topsoil were alarmingly high. Their concentrations were up to 282,000 mg kg⁻¹ dry weight for ∑DDT and up to 63,000 mg kg⁻¹ for ∑HCH. A herbicide, pendimethalin [N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine], was also found at concentrations up to 41,000 mg kg⁻¹ dry weight. Thus the total pesticide content in the soil was almost 40%. Following these findings the area is now earmarked to be a demonstration site for a proposed GEF project ‘Bioremediation of POPs impacted soils in East Africa’.     

Comparison of microwave-assisted digestion procedures for total trace element content determination in calcareous soils

The aim of the study was to determine total trace (Cd, Co, Cr, Cu, Mn, Pb and Zn) and major (Al and Fe) element concentrations in calcareous soils using microwave-assisted digestion procedures. The literature showing lack of consensus regarding digestion procedures and unsatisfying recoveries for calcareous materials, four procedures using various acid combinations (HCl, HNO₃, H₂O₂, HF) and volumes were tested using a certified reference material (CRM 141R) and natural calcareous soil samples. Digests were analysed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Repeatability (R.S.D. <5%) and recoveries (82-116%) showed that the procedures were precise and accurate for most elements. Five calcareous soil samples from a Champagne vineyard plot were, then, subjected to these procedures. In calcareous materials, the presence of HF resulted in Al being severely underestimated (recovery <5%) and Co overestimated (recovery >124%) due to complex formation or spectrochemical interferences, respectively. As digestion was not significantly influenced by the addition of H₂O₂, the procedure corresponding to Aqua regia (HCl-HNO₃) appeared as the best compromise and was selected for further multielemental environmental studies on calcareous materials, even if the absence of HF could lead to incomplete digestion of accessory silicate minerals. Results for a vineyard plot showed that the soils were contaminated (3.65 mg kg⁻¹ Cd, 67 mg kg⁻¹ Cr, 278 mg kg⁻¹ Cu, 143 mg kg⁻¹ Pb and 400 mg kg⁻¹ Zn) as a consequence of urban waste and copper-treatment applications.