Potential of microbore HPLC within a multiresidue method for the trace analysis of plant-protective substances in water

The performance of microbore HPLC as a "measurement channel" within a true multiclass/multiresidue method for monitoring plant protectants in raw and potable water is demonstrated. The method has a modular design and consists of a non-selective sampling and preparation line generating 250 microL of an "extract" from a 100-mL water sample; this extract can be introduced to up to four measurement channels, as required by the analytical task. The microbore HPLC channel can be used to quantify 34 plant protectants in the 0.1 microg L(-1) concentration range by use of diode-array detection at seven different wavelengths. A solvent change is necessary to link sample preparation to microbore HPLC; this uses 50 microL of the "extract" and is accomplished directly in an autosampler vial. Performance characteristics were evaluated for tap water spiked at 0.2 microg L(-1). Average recoveries were between 65 and 100% and method detection limits were 0.07 microg L(-1) or better. The ability to provide comparable and accurate results was proven by participation in an interlaboratory comparison trial. The procedure for preparing microbore columns from 750 microm i.d. PEEK tubing is described in detail to enable the reader to prepare his own columns. The reproducibility of this preparation procedure was proven by an analysis-of-variance test.     

Solid-phase extraction for multiresidue analysis of organic contaminants in water

To overcome the limitations of the detection systems associated with gas or liquid chromatography, a sample pretreatment is required with the objective to provide a sample fraction enriched with all the target analytes and as free as possible from other matrix components. There is now no doubt that solid-phase extraction (SPE) has now become the method of choice for carrying out simultaneously the extraction and concentration of many compounds in aqueous samples. Many recent applications of SPE to multiresidue analysis are reviewed with an emphasis on the importance of the choice of the sorbent and of the sample volume. SPE is particularly well adapted to multiresidue analysis including compounds from a wide range of polarity or characterized by various physico-chemical properties. However, SPE is not completely free from practical problems inherent to the nature of the compounds or to the coupling to the chromatographic systems. Many examples are reported to illustrate these problems which can in most cases be circumvented. New developments in SPE are also reviewed.     

Development of a multiresidue method for nitrogen-containing pesticides

Summary A great number of commonly used pesticides contain nitrogen and many of these compounds are amendable to gas chromatography with nitrogen-specific detection. Nitrogen-containing pesticides have however poorly been investigated in comparison to the halogen- or phosphorus-containing pesticides as regarded their possible combination in, preferably, a Multiresidue Method (MRM). In the study presented here, a start is made for a systematic approach to the multiresidue analysis of nitrogen-containing pesticides in foodstuffs. An inventory has been made of the target group of compounds and the gaschromatographic behaviour of approx. 20 nitrogen-containing fungicides has been studied, as well as their behaviour in some commonly used extraction and clean-up procedures. Results for the determination of 15 fungicides in cucumber analysed by a modification of MRM 7 of the dutch manual are described. In the near future the method will be extended for the application to other matrices and to approximately 40 nitrogen-containing herbicides.     

Development and validation of a multiresidue method for determination of 82 pesticides in water using GC

Several methods used for the multiresidue analysis of pesticides from the environment and drinking water have been reported. However, most of these reports dealt with a small number of targeted pesticides or some special groups. A method that is simple, faster, and more cost‐effective than the environmental protection agency (EPA) method has been developed for the analysis of 82 frequently used pesticides in water samples obtained from Yeongsan and Sumjin rivers, as well as rice fields located in various locations around the two rivers. The samples were extracted by dichloromethane, and the pesticides were analyzed using a GC‐electron capture detector (ECD), followed by confirmation with GC‐MS. Recoveries were found to be between 82 and 120.1% for most of the tested pesticides, which were in agreement with the standard values dictated by the EPA. The method was potentially applied to 66 water samples for human consumption and 90 water samples from the rice fields and irrigation ditches that were collected from June to September 2007. Oxadiazon, butachlor, and alachlor were detected in some of the river water samples collected in June, iprobenfos (IBP) was detected in samples collected in August, and no pesticide was detected in September. On the other hand, chlorpyrifos‐methyl, IBP, hexaconazole, diazinon, oxadiazon, butachlor, and isoprothiolane were detected at relatively high concentrations in 48 rice paddy field water samples collected between June and September 2007. Alachlor in one sample and procymidone in some of the rice paddy field water samples were also detected in trace amounts. The results were consistent with the temporal pattern of pesticide application in Korean rice fields.     

Instrumental method for the determination of trace elements in water samples by neutron activation analysis

Thermal neutron activation analysis and a large-volume high-resolution Ge(Li) gammaray spectrometer, connected on-line to a DEC PDP 8/L computer, have been used to measure the concentrations of Na, Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, W and Hg in some Italian subsurface water samples. The instrumental method requires neither a chemical separation technique nor a pre- or post-concentration of the trace elements to be detected. As a consequence, this method eliminates many inherent errors associated with chemical determinations. The technique is sensitive, precise and particularly suitable for routine analysis of many trace elements at both natural and pollution levels in water samples. The interferences due to fast neutron (n, p) and (n, α) reactions are not appreciable, with the only exception of the⁵⁴Fe(n, p)⁵⁴Mn and⁵⁸Ni(n, p)⁵⁸Co reactions. Losses of volatile, elements, e. g. As, Br and Hg, during irradiation proved to be negligible.     

Inclusion of the fungicide chlozolinate in a multiresidue method.

A multiresidue GC method for the monitoring of electron-capturing compounds has been validated for the fungicide chlozolinate in the four crops with uses to be supported during re-evaluation procedures within the European Union. The method was also tested for a further eight crops. Matrix-matching of standards was found to be desirable to avoid the random occurrence of artificially high recoveries. The high accuracy and precision of the method, with a mean recovery of 94% and an RSD of +/-5%, shows it to be suitable for routine residue control in a wide range of crops.     

Evaluation of a multiresidue method for measuring fourteen chemical groups of pesticides in water by use of LC-MS-MS

European Council Directive 98/83/EC on the quality of water intended for human consumption brought a new challenge for water-quality control routine laboratories, mainly on pesticides analysis. Under the guidelines of ISO/IEC 17025:2005, a multiresidue method was developed, validated, implemented in routine, and studied with real samples during a one-year period. The proposed method enables routine laboratories to handle a large number of samples, since 28 pesticides of 14 different chemical groups can be quantitated in a single procedure. The method comprises a solid-phase extraction step and subsequent analysis by liquid chromatography-mass spectrometry (LC-MS-MS). The accuracy was established on the basis of participation in interlaboratory proficiency tests, with encouraging results (majority |z-score| <2), and the precision was consistently analysed over one year. The limits of quantitation (below 0.050 μg L⁻¹) are in agreement with the enforced threshold value for pesticides of 0.10 μg L⁻¹. Overall method performance is suitable for routine use according to accreditation rules, taking into account the data collected over one year. Figure Simultaneous SPE extraction system for high thoughput analysis Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Notes: IAREN is an accredited laboratory under the ISO/IEC 17025:2005 for 165 analytical determinations and part of the NORMAN Network of Reference laboratories for monitoring of emerging environmental pollutants in the European Union. This work was presented (podium presentation) at the 12th Symposium on Sampling and Handling of the International Association of Environmental Analytical Chemistry (IAEAC), Zaragoza, 2006.     

Electrochemical detection for trace analysis by capillary HPLC

An amperometric-type electrochemical detector is proposed for use in capillary HPLC. Its cell (volume 60 nl) contains a cylindrical working electrode for detecting the presence of electroactive compounds. The noise level is 3–5 pA depending on the potential. The minimum detectable concentrations of the o-, m-, and p- isomers of nitrophenol (after separation of a 20 μl sample on a fused silica column) lies between 4 and 18 ng/l. The relative standard deviation of the height of the chromatographic peaks of phenols present at concentrations of 10 ppb does not exceed 0. 08 (n = 5).     

Neutron activation as a routine method for the determination of trace elements in water

By freeze-drying the following elements can be determined in natural water except sea water: Au, Ba, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Mo, Na, Sb, Sc, Se, U, Zn. Some problems may arise with respect to As and Hg. Cu, Cd and Ni can only be determined if present in high concentrations. Separation by adsorption on charcoal in presence of complexing agents gives yields between 75 and 100% for the following elements in sea water: Ag, Au, Cd, Ce, Co, Cr, Eu, Fe, Hg, La, Mo, Sc, Se, U, Zn (As 67%, Sb 56%). Activation or use of labelled ions and study of exchange give information about mobility of trace elements in suspended matter.     

Study on the efficiency of assembled packed microbore columns in HPLC

Summary Stainless steel columns (internally mirror-finished, 125 or 250nm in length, of bore 1.0 or 1.6mm) were slurry-packed with 5μm and 4μm reversed phase silicas (Hypersil ODS, LiChrosorb RP-8 and RP-18 and Superspher RP-8. The HPLC equipment consisted of a pump LC5A (Shimadzu) or a pump 2150 (LKB Instruments), a rheodyne valve 7413 with loops of 0.5, 1.0 and 5.0mm³ and a Jasco-Uvidec 100-II UV detector, variously with one of three specially constructed cells of 0.2, 0.4 and 1.3mm³ volume. Columns were assembled using two types of coupling device employing a stainless steel capillary of 0.12mm bore. The effect of sample volume, design of coupling device in assembled column, detector cell volume and geometry on column plate count was examined to optimize the conditions and the instrument compartments. The highest efficiency for the assembled columns was achieved by use of the 0.2mm³ detector cell, a low dead volume coupling device and a 0.5μl sample volume. Sets of 5 assembled columns gave reduced plate height values between 2–3 at a reduced velocity 2<v<3, indicating that extra-column effects were negligibly small; the performance was identical to that of conventional analytical columns. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Improved cleanup method for the multiresidue analysis of N-methylcarbamates in grains,fruits and vegetables by means of HPLC with postcolumn reaction and fluorescence detection

Summary An improved and quick cleanup method has been developed for the liquid chromatographic determination of 21 N-methylcarbamate pesticides and 10 of their metabolites in grains, fruits and vegetables. Various types of solid phase extraction columns have been tested for the cleanup step in order to replace the time-consuming cleanup method found in the literature. Aminopropyl-bonded silica columns proved to be superior to unbonded silica or octyl, octadecyl, cyanopropyl and diol-bonded silica. For all 16 types of matrices tested, a single column cleanup step appeared to be satisfactory. The final determination was performed by separation of the N-methylcarbamates via high-performance liquid chromatography followed by postcolumn reaction, fluorogenic labelling of the hydrolytically formed methylamine with the orthophthalaldehyde/2-mercaptoethanol reagent, and fluorescence detection. Recovery data for 256 carbamate/commodity combinations will be given. The results of the routine analysis of real samples will also be presented. Finally, possibilities for confirming positive samples by an independent, second method will be discussed.     

Orthogonal array optimization of a multiresidue method for cereal herbicides in soils

Nearly 40 herbicides, commonly used for barley, were selected for analysis in soils of this crop. The primary objective was to develop a multiresidue method taking into account that herbicides belonged to different chemical families. Some preliminary experiments with different solvents in combination with water, acetic acid and ammonium hydroxide, were developed in order to design the predefined region covered by the orthogonal array design used for optimization. Final extracts were splitted in two aliquots, one of them was directly analyzed by gas chromatography-mass spectrometry (GC-MS), and the other one was derivatized before the acidic analyte analysis. Principal component analysis (PCA) was applied to the data generated in the preliminary experiments, in order to clarify the relationships among the different variables studied. According to the obtained results, the following variables were selected: solvent type and ratio, amount of acetic acid and extraction time. The statistical analysis revealed that all the factors were significant being the most important, the type and ratio of solvent for basic and neutral herbicides and the acetic acid percentage for acid herbicides. The final optimized method consisted of shaking previously wet soil samples for 30 min with 30 ml of acetone acidified with 1% acetic acid. Method validation was evaluated following the EU guidelines.     

Calibration method for the infrared-spectrometric trace gas analysis

Summary A simple and versatile calibration method for the infrared spectrometric trace analysis of gases and vapours is described. A dynamically operating set-up consisting of a capillary dosage system and a dilution unit with a set of micro-orifices was used for producing exactly known small volume fractions of trace constituents in gas mixtures. The infrared absorption measurements were performed using a Fourier transform spectrometer equipped with a long-path gas cell. Absorption coefficients of selected vibrational-rotational bands obtained by a linear least-squares fit around the threshold limit values are reported for NH₃, SO₂, CCl₄ and 1,4-dioxane as examples of trace constituents in air.

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Methode zur Kalibrierung in der infrarotspektrometrischen Spurenanalyse von Gasen

Zusammenfassung Ein vielseitig einsetzbares einfaches Kalibrierverfahren für die infrarotspektrometrische Spurenanalytik von Gasen und Dämpfen wird beschrieben. Zur Realisierung genau bekannter kleiner Volumenanteile von Spurenkomponenten in Gasmischungen diente eine nach dem dynamischen Prinzip arbeitende Apparatur, bestehend aus einem Capillardosierer und einer Verdünnungseinheit mit Mikroblenden. Zur Messung der Infrarotabsorption wurde ein Fourier-Transform-Spektrometer mit Langweggasküvette verwendet. Für NH₃, SO₂, CCl₄ und 1,4-Dioxan als Beispiele für Spurenkomponenten in Luft werden die mit Hilfe einer linearen Ausgleichsrechnung im Bereich der MAK-Werte erhaltenen Absorptionskoeffizienten ausgewählter Schwingungs-Rotationsbanden angegeben.

     

Synthesis and application of a novel solid‐phase extraction adsorbent for multiresidue analysis of insecticides in water

A new solid‐phase adsorbent was synthesized for the simultaneous enrichment of multiple classes of trace insecticides (neonicotinoids, organophosphates, fiproles, and organochlorines) in water. The adsorbent was spherical with a diameter, surface area, average pore volume, and pore size of approximately 5 μm, 341 m²/g, 0.092 m³/g, and 2.22 nm, respectively. Extraction conditions were optimized, including water pH and the type and volume of the rinsing and eluting solvents. After extraction, target insecticides were analyzed by gas chromatography with mass spectrometry and high‐performance liquid chromatography with tandem mass spectrometry. The recovery of neonicotinoids ranged from 63.0 to 124%, except for clothianidin (40.1–52.9%). Recoveries of organophosphates, fiproles, and organochlorines were in the ranges of 37.0–102, 64.0–101, and 42.0–69.3%, respectively. Relative standard deviations were <20% except for profenofos (5.1–30%) and method detection limits were 1.8–12.7 ng/L, suggesting that the precision and accuracy of the developed method were viable. At environmentally relevant concentrations, the new adsorbent achieved comparable recoveries of target insecticides to hydrophilic–lipophilic balance adsorbent while providing an additional advantage by further reducing matrix effects. Field water samples from the Pearl River in Guangzhou, China were analyzed, and the frequent detection of neonicotinoids raises concerns about their aquatic risk.     

Recent developments in trace analysis of poly- and perfluoroalkyl substances

Recent developments, improvements, and trends in the ultra-trace determination of per- and polyfluoroalkyl substances (PFASs) in environmental and human samples are highlighted and the remaining challenges and uncertainties are outlined and discussed. Understanding the analytical implications of such things as adsorption of PFASs to surfaces, effects of differing matrices, varying PFAS isomer response factors, potential bias effects of sampling, sample preparation, and analysis is critical to measuring highly fluorinated compounds at trace levels. These intricate analytical issues and the potential consequences of ignoring to deal with them correctly are discussed and documented with examples. Isomer-specific analysis and the development of robust multi-chemical methods are identified as topical trends in method development for an ever-increasing number of PFASs of environmental and human interest. Ultimately, the state-of-the-art of current analytical method accuracy is discussed on the basis of results from interlaboratory comparison studies.     

Rapid multiresidue screening method for organophosphate pesticides in vegetables

Summary A rapid and efficient multiresidue extraction procedure using ethyl acetate and sodium sulfate has been applied to the analysis of diazinon, methamidophos, chlorpyrifos, malathion, parathion, parathion-methyl, dimethoate and monocrotophos residues in many different kinds of vegetables. No cleanup step was required Concentrated extracts were analysed by gas chromatography with flame photometric detection in phosphorus mode. Recovery studies were performed in six kinds of matrices at two fortification levels. Recoveries were in the range 80–115%. The limit of quantification of the analytical method has been estimated as 0.01 ppm for diazinon, methamidophos and malathion, 0.03 ppm for chlorpyrifos, parathion, parathion-methyl and dimethoate and 0.1 ppm for monocrotophos. Experiments showed that potentially it should be possible to develop a rapid and universally applicable method for organophosphate pesticide residues in different matrices.     

Development of a solid-phase microextraction gas chromatography with microelectron-capture detection method for a multiresidue analysis of pesticides in bovine milk

A simple and rapid method based on solid-phase microextraction (SPME) technique followed by gas chromatography with microelectron-capture detection (GC-microECD) was developed for the simultaneous determination of more than 30 pesticides (pyrethroids and organochlorinated among others) in milk. To our knowledge, this is the first application of SPME for the determination of pyrethroid pesticides in milk. Negative matrix effects due to the complexity and lipophility of the studied matrix were reduced by diluting the sample with distilled water. A 2(5-1) fractional factorial design was performed to assess the influence of several factors (type of fiber coating, sampling mode, stirring, extraction temperature, and addition of sodium chloride) on the SPME procedure and to determine the optimal extraction conditions. After optimization of all the significant variables and interactions, the recommended procedure was established as follows: DSPME (using a polydimethylsiloxane (PDMS)/divinylbenzene (DVB) coating) of 1 mL of milk sample diluted with Milli-Q water (1:10 dilution ratio), at 100 degrees C, under stirring for 30 min. The proposed method showed good linearity and high sensitivity, with limits of detection (LOD) at the sub-ng mL(-1) level. Within a day and among days precisions were also evaluated (R.S.D.<15%). One of the most important attainments of this work was the use of external calibration with milk-matched standards to quantify the levels of the target analytes. The method was tested with liquid and powdered milk samples with different fat contents covering the whole commercial range. The efficiency of the extraction process was studied at several analyte concentration levels obtaining high recoveries (>80% in most cases) for different types of full-fat milks. The optimized procedure was validated with powdered milk certified reference material, which was quantified using external calibration and standard addition protocols. Finally, the DSPME-GC-microECD methodology was applied to the analysis of milk samples collected in farms of dairy cattle from NW Spain.     

小体积常压气体中微量水分分析方法研究

本文在卡尔·费休库仑法的基础上建立了一套独特的分析系统和相应的分析方法,用以分析常温常压下小体积气体中微量水分。通过检测高纯氮气中的微量水分考核了方法的精密度,分析数据的实验标准偏差U<10%;通过分析空气中的水分含量验证了方法的准确度,空气中水分的测量值与计算值在误差范围内一致。小体积常压气体中微量水分的卡尔.费休分析方法的建立,对分析贮存环境气体内水分变化规律及采取有效措施控制封装气体内水分含量,建立较干燥的贮存环境具有指导作用。     

New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices

A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples.