P. Scribe

Application of on-line solid-phase extraction followed by liquid chromatography—thermospray mass spectrometry to the determination of pesticides in environmental waters

Abstract A multi-residue method for the trace-level determination of 34 pesticides and various transformation products was developed by using on-line solid-phase extraction and either ten 4.6-mm Empore extraction discs containing C 18 or a conventional precolumn, packed with PRP-1 copolymer, followed by liquid chromatography—thermospray mass spectrometry with time-scheduled selected-ion monitoring. Two main ions (usually [M + H] + and [M + NH 4 ] + or [M + CH 3 CN] + ) were used for each pesticide in the positive-ion operational mode, while [M − H] − and [M + HCOO] − ions were used in the negative-ion mode. Losses of CH 3 NCO were also monitored for many of the carbamate pesticides. The proposed method requires 100 ml of sample for a limit of detection of 0.01–0.4 μ/1, depending on the particular compound and the operational mode. Calibration graphs were constructed by preconcentrating 100 ml of an estuarine water sample, spiked with the pesticide mixture at various concentration levels, varying from 0.025 to 1.2 μg/1. Good linearity was observed for sixteen of the analytes studied, the relative standard deviation ( n = 5) being 4–13%. Some examples of the trace-level determination of various pesticides in European river and ground water samples are given.

The application of isotopic and biogeochemical markers to the study of the biochemistry of organic matter in a macrotidal estuary, the Loire, France

Abstract The biogeochemistry of organic matter in a macrotidal estuary, the Loire, France, has been studied for two years during different seasons. Both particulate matter and sediment have been sampled in the riverine zone, in the maximum turbidity zone and in the ocean near the river mouth. Two techniques have been used: carbon isotopic ratio determination and analysis of lipid-marker signatures in the n-alkane, n-alkene and fatty acid series. For the period corresponding to the output of the maximum turbidity zone in the ocean, the complete change of organic matter, continental in nature in the inner estuary, pure marine in the outer estuary is well illustrated by the decrease of δ13C values and of carbon preference index of n-alkanes. Input sources of organic matter by continental plants, plankton and micro-organisms are discussed from biogeochemical-marker analyses data along with the processes of accumulation of particles and their evolution with the season. Some criteria for evidencing the nature of various organic-matter pools are assessed and compared in different chemical-marker series as follows: high molecular weight n-alkanes and fatty acids, perylene for continental imprints, polyunsaturated 18-, 20- and 22-carbon fatty acids, n-C17, n-alkenes and squalene for algae imprints, branched iso and anteiso fatty acids, Δ11-C18:1 for microbial imprints.

Off-line and on-line preconcentration techniques for the determination of phenylureas in freshwaters

Abstract Phenylurea herbicides are analysed by reversed-phase liquid chromatography using UV detection at 244 nm after a concentration step in order to determine ppb or sub-ppb levels in drinking and river waters. With an average UV detection limit of 5 ng, a 500 ml sample volume is necessary to reach the 10 ppt level for spiked LC grade water samples and enables easy determination of concentrations below the ppb level for river water samples. Off-line and on-line methods are compared for the concentration step. Off-line concentration consists in a liquid sorption on n-octadecyl silica (C18) and elution by a suitable organic solvent. Polar phenylureas have low retention volumes on C18 silica and consequently the length of the concentration column has to be 10 cm to concentrate them at the ppb level from 100 ml of water and longer for lower levels of detection. Nevertheless, we show that increasing the size of the concentration column does not improve the limits of detection because of the numerous interfe...

Particulate organic carbon, sterols, fatty acids and pigments in the Amazon River system

Water samples were collected from the Amazon River system during a high flood period, in June 1989, and lipids associated with particles retained on GF/F filters were examined. Particles showed a highly variable organic carbon content (1.8–29.0%). Corresponding organic carbon concentrations varied from 0.36 to 1.13 mg/l. The flood conditions encountered during the sampling period may feed exceptional inputs of soil organic matter into the tributaries and the Amazon River. Composition and concentration of sterols, fatty acids and pigments were determined to estimate the relative portion of terrigenous and autochthonous fraction of this complex organic matter. Sterol distribution patterns were similar to other equatorial rivers, in the Orinoco (Venezuela) and Solo (Indonesia). In comparison with the dominant profile of the Amazon system, distinct patterns were found in the Trombetas River (29Δ5,22 ∼ 27Δ5 ∼ 29δ5 ≫ 28Δ5, 28Δ5,22) and in the Tapajos River (27Δ5,22 > 27Δ5 ≫ 29Δ5, 28Δ5, 28Δ5,22). These fingerprints reflect different vegetation types of drainage basins and distinct planktonic pools. The distribution of even-carbon numbered saturated fatty acids in the carbon range of 24–36 revealed low inputs of constituents associated with cuticular waxes of vascular plants in Black waters and in the Tapajos River (∼200 ng/l), higher in White waters (328–483 ng/l) and highest in the Trombetas River (704 ng/l) and in stagnant waters of a small lake close to the Amazon (1088 ng/l). Pigment concentrations showed that in the main river and most tributaries vegetal carbon did not represent more than 2%, except for the Tapajos River (6.2%) and in relatively stagnant waters sampled along the main river (9.2%). Based on relative abundance of Chl b, Chl c, fucoxanthin, peridinin, alloxanthin, and zeaxanthin, various phytoplanktonic assemblages were evidenced in the Amazon River system. Branched fatty acids in the carbon range of 15–17 gave insight into bacterial signatures. They showed low microbial contribution to the fatty acid pool, with slightest higher contribution in a swamp of stagnant waters and in the White waters of the Solimoes River.

Rapid semi-preparative class separation of organic compounds from marine lipid extracts by high-performance liquid chromatography and subsequent quantitative analysis by gas chromatography

Abstract Quantitative analysis of biogenic and anthropogenic organic markers in the atmospheric and marine environment is difficult, owing to the low concentration of these compounds in air and water. In the present study, a rapid semi-preparative separation of lipids extracted from a recent marine sediment is proposed by liquid chromatography on a silica column. The basic idea of this method is to carry out a precisely controlled gradient elution (with emphasis on solvent purity, water content of the mobile phase, etc.) in order to obtain reproducible retention times, which would allow separation without detection. Each column is first calibrated with standards at detectable concentration using UV and RI detection. The saponified extract is directly injected on the column and then eluted by a mobile phase of isooctane containing from 0.5% to 10% of 2-propanol. In a single injection, the following classes can be separated with good resolution: alkanes, aromatic hydrocarbons, fatty acids, alcohols, sterols and hydroxy-fatty acids. The total time of 40 min, includes a recycling time of 10 min. Each fraction is then derivatized and analyzed by gas chromatography or by gas chromatography coupled to mass spectrometry. Quantitative analysis is carried out with standards.

Dissolved and particulate hydrocarbons in the Loire estuary, from the riverine zone to the external estuary: budget at different seasons

Abstract In order to investigate the fate and transport processes of hydrocarbons in estuarine and coastal environments, we have undertaken a study of different hydrocarbon species in both dissolved and particulate forms. This two years study has been conducted in the Loire estuary at different reference stations (riverine, injection of sewage effluents, maximum turbidity zone, open sea) and at different seasons corresponding to various hydrological (high and low water) and biological conditions. Quantitative and qualitative analysis of hydrocarbons has been carried out by GC, GC/MS, focusing on n-alkanes and n-alkenes. Overall dissolved n-alkane concentrations vary in a narrow range, from 0.1 to 1.2μgl−1. Dissolved n-alkanes show fairly constant distribution patterns, with a slight odd/even carbon chain predominance, extending from n-C16 up to n-C42, maximizing at n-C27, n-C29 and n-C31. CPI values are low (1–1.7) and may indicate the predominance of two sources, petroleum products and microbial and alga...

Biogeochemistry of organic matter in Lake Geneva. I, Particulate hydrocarbons as biogenic and anthropogenic molecular markers

A study of the biogeochemistry of organic matter in Lake Geneva at a central station (SHL2), was carried out at key periods of the biological cycles from November 1985 to September 1986. The seasonal variability of particulate hydrocarbons was studied in the epilimnion and the hypolimnion, focusing on specific periods such as high phytoplankton productivity and rising herbivorous zooplankton activity (May 1986), clearness of waters (June 1986) and intense mixing of waters (February 1986).Analysis of non-aromatic hydrocarbons (NAH) indicated that their major source is the autochtonous phytoplankton. Year 1986 was characterized by a spring bloom of nanoplankton (chlorophyceae and cryptophyceae) which remained predominant during summer and fall. These biological events were correlated with an increase of biogenic NAH, particulary n-alkane and alkene concentrations; the latter increased by one order of magnitude in May. n-Alkane distributions maximized at n-C17 or n-C29, and the n-C17/n-C29 ratio varied in surface water from 2.8 in May to 0.06 in November of the preceding year, reflecting phytoplankton dominant species. Values of NAH/POC, n-alkanes/POC, alkenes/POC and pristane/phytane ratios underwent seasonal and vertical variations which could be related to grazing and/or settling of particles. NAH, n-alkane and alkene enrichment in hypolimnion particles was interpreted to be a result of zooplankton migrations.A series of 37 monoenes and polyenes having from 15 to 31 carbon atoms, originating from planktonic sources, were recognized in the particulate matter by gas chromatography/mass spectrometry (GC/MS). Their distribution was described in 3 sized particles (> 200 µm, 200-60 µm and < 60 µm, identified as adult zooplankton, young zooplankton and nanoplankton respectively) at two different periods of the biological cycle, May and June 1986. Low level inputs originating from terrestrial higher plants were evident in particles; the value of the Carbon Preference Index (CPI) in the carbon range 23–35 was less than 2.8.In all samples analyzed by GC, an unresolved complex mixture of hydrocarbons (UCM) was present and was interpreted, at least in May, as partly originating from the degradation of organic matter by microorganisms. Typical anthropogenic PAH, such as benzofluoranthene and dibenzo (a) anthracene, were found at a low level (9 and 3 ng l−1 respectively). The absence of hopane-type hydrocarbons, except in November 1985 and in September 1986, and typical combustion PAH associated with particles indicated high temperature pyrolytic contaminants rather than petroleum-derived compounds.

Application of Hydrocarbon Biochemical Markers to the Study of Particulate Matter in a High Turbidity Estuary

Abstract The Loire estuary is characterized by complex mixing processes of naturally-derived organic matter from riverine and oceanic waters that are introduced into the inner estuary or expelled to the open sea by tidal and river currents. Particulate matter has been sampled at different seasons from February 1983 and for various hydrodynamic situations: (1) in the riverine zone, (2) in the high turbidity zone and (3) in the ocean, near the river mouth. Several mono- and polyalkenes have been found associated with particles in the inner estuary, i.e., from the river to the high turbidity zone. The most frequently encountered structures are n-alkenes: 17:1, 23:1, 25:1, 27:1 and phytadiene-type isomers C 20 H 38 . In June 1985, during a planktonic bloom, three weeks after a major flood, a large variety of olefins ranging from 15 to 29 carbon atoms were found at high concentrations in the outer estuary. Significant correlations exist between their concentration and the algal particulate organic carbon pattern.