Determination of methylmercury in natural waters at the sub-nanograms per litre level by capillary gas chromatography after adsorbent preconcentration

Methylmercury was preconcentrated from water on to a sulph-hydryl cotton fibre adsorbent, using the column technique or the batch-column two-stage technique. A small volume of 2 M HCl was used to elute methylmercury and to separate it from inorganic mercury; 0.4–0.6 ml of benzene was used to extract methylmercury from the eluate. Analysis was performed by capillary gas chromatography with electron-capture detection. The detection limit for methylmercury was <0.05 ng l^?1 in a 4-l water sample. Four surface waters were analysed to test the agreement of methylmercury concentration between the two preconcentration methods, and to test the interference of humic substances on the filtered and unfiltered surface water. The methylmercury concentrations found in different surface water samples ranged from 0.08 to 0.48 ng l^?1.     

Determination of trace metals in natural waters at nanogram per liter levesls by electrothermal atomic absorption spectrometry after extraction with sodium diethyldithiocarbamate

The determination of trace metals (Cd, Co, Cu, Fe, Ni and Pb) at concentrations found in fresh and sea waters is described. The metals are extracted as diethyldithiocarbamates from 500-ml samples into carbon tetrachloride, the extracts are evaporated to dryness and the residues are mineralized with 0.1 ml of concentrated nitric acid. This solution is used for graphite-furnace atomic absorption spectrometry after appropriate dilution. The detection limits are 10 pg Cd, 150 pg Co, 125 pg Cu, 100 pg Fe, 250 pg Ni and 100 pg Pb. The extraction/mineralization method is almost free from interferences, e.g., from trace elements at 500-fold and Na, K, Ca and Mg at million-fold amounts. The procedure is successfully applied to the determination of the above metals in deionized water, and river and sea waters.     

Determination of lead in natural waters using flow injection with on-line preconcentration and flame AAS detection

A rapid and sensitive method has been developed for the determination of lead in water samples by flame atomic absorption spectrometry using on-line preconcentration on a microcolumn packed with silica gel treated with a mixture of Aliquat 336 and nitroso-R-salt. The lead is retained at pH 5.5. The preconcentrated lead is directly eluted from the column to the nebulizer-burner system using 150 L of 0.1 mol/L hydrochloric acid. The optimum preconcentration conditions are given and the retention efficiency achieved is higher than 80%. The enrichment factor is 37 and 100 for sample volumes of 5 and 30 mL, respectively. The limits of detection are 10.0, 6.0 and 4.0 ng/mL when 5, 10 and 30 mL of water is preconcentrated.     

Determination of mercury species in natural waters at picogram level with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS

A new technique has been developed for the determination of methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury in natural water samples. The mercury compounds have been complexed for the preconcentration on RP C18 columns by sodium pyrrolidinedithiocarbamate (SPDC), sodium diethyldithiocarbamate (SDDC) and hexamethyleneammonium (HMA) — hexamethylenedithiocarbamate (HMDC), separated by HPLC and determined by UV-PCO-CVAAS (ultra violet, post column oxidation, cold vapour atomic absorption spectrometry). The standard deviations are in the range of 6.9 to 11.8%. The recoveries amount to 86%, 78%, 88%, 83%, 79% and 84% for methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury for the enrichment from 300 ml water samples. The detection limit for methyl mercury is 0.5 ppt. This new on-line preconcentration procedure has been tested with rain, drinking, surface and process water samples.     

Ultra-sensitive fully automated immunoassay for detection of propanil in aqueous samples: steps of progress toward sub-nanogram per liter detection

The widely-used pesticide propanil is a selective post-emergent general-use acetanilide herbicide registered for control of broadleaf and grass weeds in rice, small grain, and turf. Because broad application and quite heavy use of this herbicide lead to contaminated sites and, consequently, contaminated water, immunoanalytical methods with very low limits of detection (LOD) and low limits of quantification (LOQ) are becoming increasingly important for environmental analysis and, especially, for monitoring drinking-water quality. Environmental monitoring of pesticides, hormones, endocrine-disrupting chemicals, and antibiotics in aqueous samples (e.g. surface, ground, waste, or drinking water) with quite difficult matrices places large demands on chemical analysis. Biosensors have suitable characteristics such as efficiency in enabling very fast, sensitive, and cost-effective detection. Here we describe the steps of progress toward sub-nanogram per liter detection of propanil with a fully automated immunoassay. In contrast with common analytical methods such as GC–MS or HPLC–MS the biosensor used requires no sample pre-treatment and pre-concentration. The basis of our sensitive assay is an antibody with a high affinity constant toward propanil. During the optimization process, we compared different surface modifications (four different immobilized derivatives) and reduced the amount of antibody per sample. In fact, optimization of the assay resulted in an LOD of 0.6 ng L^–1 and an LOQ of 4.5 ng L^–1 without any sample pre-treatment and without pre-concentration. These results for propanil with the RIANA instrument, and its improved sensitivity for detection of a single pesticide at the low nanogram per liter range, show that biosensors can compete with common analytical methods in the field of water analysis.     

Selective method for the analysis of perchlorate in drinking waters at nanogram per liter levels, using two-dimensional ion chromatography with suppressed conductivity detection

The United States Environmental Protection Agency (EPA) collected drinking water occurrence data for perchlorate in the Unregulated Contaminant Monitoring Regulation (UCMR 1; 2001-2005) using EPA Method 314.0. To address the interest in increasing sensitivity and selectivity for the analysis of perchlorate, three new methods, EPA Methods 314.1, 331.0 and 332.0, were subsequently published by EPA for the analysis of perchlorate in drinking water. In 2006, an automated two-dimensional ion chromatography (2D-IC) method for measuring perchlorate with suppressed conductivity detection was developed. Two-dimensional IC is essentially an automated "heart-cutting", column concentration and matrix elimination technique. In the first dimension, a large sample volume is injected onto a first separation column and the separated matrix ions are diverted to waste while the analyte(s) of interest are selectively cut, trapped and concentrated in a concentrator column. In the second dimension, the contents from the concentrator column are eluted onto a second analytical column for separation and quantitation of the analyte(s) of interest. Incorporation of two columns with different affinities for the analyte(s) in a single analysis can provide comparable selectivity and superior sensitivity to a method using second column confirmation in a second separate analysis step. Use of this approach led to the development of a new, highly sensitive and selective 2D-IC, suppressed conductivity method with a Lowest Concentration Minimum Reporting Level (LCMRL) of 55 ng/L for perchlorate in drinking water samples. This new method has comparable sensitivity and selectivity and is simpler and more economical than IC-mass spectrometric (MS) or IC-MS-MS techniques. The method is now being prepared for publication as EPA Method 314.2.     

Multiresidue analysis of 95 pesticides at low nanogram/liter levels in surface waters using online preconcentration and high performance liquid chromatography/tandem mass spectrometry

A new multiresidue method for the analysis of 95 pesticides and breakdown products with a wide range of physiochemical properties in surface and ground water using online solid-phase extraction coupled with HPLC/MS/MS is presented. Using an injection volume of only 500 microL filtered water, an LOD in the 1-10 ng/L range was achieved for all but one substance, and recoveries were, with a few exceptions, in the 70-120% range. Large differences were found in the adsorption of pesticides on nine filter materials tested for filtration of the water samples. Filters of regenerated cellulose were chosen due to good recoveries and easy handling. Results from the proposed method were compared with results from previously used methods for 31 pesticides in 99 surface water samples, collected in 2008, with good agreement.     

Determination of beryllium in natural and waste waters using on-line flow-injection preconcentration by precipitation/dissolution for electrothermal atomic absorption spectrometry

A flow injection (FI) on-line precipitation-dissolution was developed for electrothermal atomic absorption spectrometry (ETAAS) determination of (ultra)trace amounts of beryllium in water samples. Beryllium was precipitated quantitatively with NH(4)OH+NH(4)Cl and collected in a knotted tube of Tygon without using a filter, while the other matrix components flowed downstream to waste. The precipitate was dissolved with nitric acid and a sub-sample was collected in a capillary of a sampling arm assembly, to introduce 10 mul volumes into the graphite tube by means of positive displacement with air through a time-based injector. This sequence was timed to synchronize with the previous introduction of 6 mug of Lu (in 20 mul) by the spectrometer autosampler. The effect of a number of possible cations on the beryllium precipitation process was studied. While, the addition of Ba(2+), Sr(2+), Ca(2+), Mg(2+), Mn(2+), Zn(2+), Co(2+) and Ni(2+) did not produce any perceptible precipitate on the reaction coil walls, the addition of Al(3+), Cr(3+) and Fe(3+) produced large precipitated particles. However, their tolerance limit was well above the levels at which theses species are commonly found in most natural waters. The detection limit (3sigma) of 25 ng l(-1) in the sample solution was obtained. The precision of the method, evaluated by ten replicate analyses of solutions containing 20 and 200 pg of beryllium were 4.8 and 4.0% (n=5), respectively. Enrichment factors from 7.0 to 10.3 and from 10.5 to 13.8 were obtained for precipitation times from 25 to 38 s and from 43 to 50 s for waste and tap waters, respectively. These results indicate that the enrichment factor was limited by the interference of some matrix metals which could precipitate as hydroxides (or related species) and be retained in the reaction coil. The integrated system permits fully automated operation, avoiding time-consuming manual work and enhancing the reproducibility and precision of the determination of beryllium. The results obtained for the determination of beryllium in certified reference materials (trace elements in water), together with the good recovery of spiked analytes, demonstrate the applicability of the procedure to the analysis of natural waters.     

Determination of methyl- and ethylmercury in rat blood and tissue samples by capillary gas chromatography with electron-capture detection

A precise and accurate method has been developed for the determination of either methyl- or ethylmercury in the blood and tissue of rats using capillary gas chromatography with electron-capture detection. The biological sample was spiked with an internal standard (methyl- or ethylmercury chloride) and after treatment with sodium thiosulphate and cupric bromide the alkylmercurials were extracted into benzene as their bromide derivatives and analysed on an OV-275 glass capillary column. The sensitivity and selectivity of the method enabled determinations to be made on small volumes of blood and tissue homogenates. The method has been applied to a pharmacokinetic study in rats dosed orally with 8 mercury as methylmercury chloride or ethylmercury chloride.     

Determination of alkyl- and alkanolamines in drinking and natural waters by capillary electrophoresis with isotachophoretic on-line preconcentration

A procedure is developed for the determination of several amines in drinking and natural waters by capillary electrophoresis with isotachophoretic on-line preconcentration without sample preparation. A background electrolyte based on acridine as an absorbing ion is proposed for analysis with isotachophoretic on-line preconcentration and indirect photometric detection. The sample was injected in the hydrodynamic mode. The procedure was tested on drinking and natural water samples. The accuracy of data obtained was confirmed by the added–found method. The analytical range was from 0.25 to 5 mg/L. The time of one analysis was 5–6 min.     

Comparison of preconcentration procedures for trace metals in natural waters

The relative merits of eight procedures for preconcentrations of trace metal ions from natural water samples and synthetic solutions are evaluated. Spikes (100 μg l^?1 ) of Mn, Co, Zn, Eu, Cs and Ba and the corresponding radioactive tracers were added to batches of drinking water, estuarine water, sea water, ground water, twice-distilled water and ahumic material solution. After equilibration for 2–5 months, the following techniques were applied: passage through columns of Dowex Al chelating resin and ofsilylated silica gel, filtration through laminate membrane filters and chelating diethylenetriamine cellulose filters, precipitation with sodium diethyldithiocarbamate and l-(2-pyridylazo)-2-naphthol, extraction with ammonium pyrrolidinedithiocarbamate, and chelation by 8-quinolinol (oxine) followed by adsorption on activated carbon. The quantitative characteristics of these techniques and the influence of the water matrix effects are discussed, as well as the applicability for x-ray fluorescence analysis.     

Determination of uranium(VI) in natural waters after preconcentration on adsorbent containing m-aminophenol fragments

Sorption and complexing properties of a modified adsorbent based on a maleic anhydride-styrene copolymer towards uranium(VI) are studied and the main quantitative characteristics of the metal ion sorption are determined. An adsorbent containing m-aminophenol fragments is proposed for the selective sorption of uranium(VI) from solutions. The optimal sorption conditions have been found. The recovery of uranium(VI) under the optimal conditions exceeds 95%. A procedure of the sorption photometric determination of uranium(VI) in sea water is developed.     

Determination of mercury in natural samples at the sub-nanogram level using inductively coupled plasma/mass spectrometry after reduction to elemental mercury

Inductively coupled plasma/mass spectrometry was used to determine mercury. Sodium borohydride was used to reduce the mercury to its elemental form, which was purged directly to the plasma using the nebulizer gas. Applications to natural waters and reference sediment are demonstrated. The detection limit, defined as three times the standard deviation of the blank, is 8 pg. The precision at the 100-pg level is 3%. The ability to make isotope dilution measurements is demonstrated.     

Determination of Zn(II) in natural waters by ICP-OES with on-line preconcentration using a simple solid phase extraction system

An on-line zinc preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed. The zinc was precipitated and retained on a minicolumn filled with ethyl vinyl acetate (EVA) at pH 9.0, without using any complexing reagent. The zinc ions were eluted from the minicolumn with 10% (v/v) hydrochloric acid. Experimental conditions including pH and sample loading and eluting variables were evaluated and established.An enrichment factor (EF) of 44 was obtained for Zn²⁺ with a preconcentration time of 120 s. Under the optimal conditions, the value of the limit of detection (3σ) for the preconcentration of 10 mL of sample was 0.08 μg L^{− 1}. The sampling frequency was about 24 h^{− 1}. The precision for six replicate determinations (repeatability conditions) at 50 μg L^{− 1} Zn level was 3.94% relative deviation standard (RSD), calculated from the peak heights obtained. The methodology was successfully applied to the determination of zinc in tap water samples and in a certified VKI reference material QC Metal LL1 DHI (Water & Environment) Denmark.     

Automated separation and preconcentration of copper(II) from natural waters using a column treatment

Summary A comparison is made between two automated column procedures for the separation and preconcentration of Cu(II) from natural waters. The column materials were: an anion-exchange resin and 8-hydroxyquinoline immobilized on a glass support. 8-Hydroxyquinoline showed about the same performance as the ion exchange resin, but was less time and labour consuming. Cu(II) determinations at the ppb level were checked with standard additions and the results were moreover compared with those obtained by another method.On leave from Lisbon University, Portugal     

Determination of aliphatic acids in natural waters using distillation and solid-phase extraction

A procedure is developed and conditions are optimized for the pretreatment of natural water using distillation with no prefiltration of acidified water in combination with preconcentration by solid-phase extraction (SPE) on a Strata-X polymeric adsorbent followed by derivatization for the determination of trace concentrations of C3–C18 aliphatic carboxylic acids by gas chromatography with mass spectrometric detection. It is shown that, at the distillation stage, 90% of free carboxylic acids of the homologous series are transferred to the distillate, which greatly facilitates the procedure of the analysis of natural water containing impurity particles and humic substances and ensures the achievement of the limit of detection for the analytes about 0.05 μg/L. It is found that, at the SPE stage, the adsorbents based on copolymers of styrene, divinylbenzene, and N-vinylpyrrolidone in plastic cartridges may serve as sources of additional pollution with benzoic, palmitic, and stearic acids in the eluates under investigation.     

Determination of tritium in natural waters

A study of the tritium content of precipitation and of river water samples, collected during a seasonal maximum of tritium concentration in 1976 is given. The measurements were made for precipitation in Belgrade from April to December 1976, and for river water from the Sava (in Belgrade), the Tisa at 137 km, and the Danube at 1425 km, 1174 km, 861 km from the confluence. The maximum monthly value of the tritium content of precipitation is 135 TU, and the Danube at 1425 km has a maximum of 196 TU (627 pCi/l). In general, there is no correlation between the amount of precipitation and river water with tritium content.     

Determination of N-pesticides in natural waters

Summary Using RP-C18 material in cartridges to preconcentrate natural water samples, a number of important GC-detectable nitrogen containing pesticides can be analysed. This should be a first step to a simple monitoring of these water constituents for which a routine survey proved to be obligate in the near future.

---

Bestimmung von N-Pesticiden in natürlichen Wasserproben

     

Carbon and nitrogen isotope analysis of atrazine and desethylatrazine at sub-microgram per liter concentrations in groundwater

Environmental degradation of organic micropollutants is difficult to monitor due to their diffuse and ubiquitous input. Current approaches—concentration measurements over time, or daughter-to-parent compound ratios—may fall short, because they do not consider dilution, compound-specific sorption characteristics or alternative degradation pathways. Compound-specific isotope analysis (CSIA) offers an alternative approach based on evidence from isotope values. Until now, however, the relatively high limits for precise isotope analysis by gas chromatography—isotope ratio mass spectrometry (GC-IRMS) have impeded CSIA of sub-microgram-per-liter scale micropollutant concentrations in field samples. This study presents the first measurements of C and N isotope ratios of the herbicide atrazine and its metabolite desethylatrazine at concentrations of 100 to 1,000 ng/L in natural groundwater samples. Solid-phase extraction and preparative HPLC were tested and validated for preconcentration and cleanup of groundwater samples of up to 10 L without bias by isotope effects. Matrix interferences after solid-phase extraction could be greatly reduced by a preparative HPLC cleanup step prior to GC-IRMS analysis. Sensitivity was increased by a factor of 6 to 8 by changing the injection method from large-volume to cold-on-column injection on the GC-IRMS system. Carbon and nitrogen isotope values of field samples showed no obvious correlation with concentrations or desethylatrazine-to-atrazine ratios. Contrary to expectations, however, δ ¹³ C values of desethylatrazine were consistently less negative than those of atrazine from the same sites. Potentially, this line of evidence may contain information about further desethylatrazine degradation. In such a case, the common practice of using desethylatrazine-to-atrazine ratios would underestimate natural atrazine degradation.