Evaluation of the analytical method performance for incurred samples

A methodology for the evaluation of the performance of an analytical method for incurred samples is presented. Since this methodology is based on intra-laboratory information, it is suitable for analytical fields that lack reference materials with incurred analytes and it can be used to evaluate the analytical steps prior to the analytical portion, which are usually excluded in proficiency tests or at the certification of reference materials. This methodology can be based on tests performed on routine samples allowing the collection of information on the more relevant combinations analyte/matrix; therefore, this approach is particularly useful for analytical fields that involve a high number of analyte/matrix combinations, which are difficult to cover even considering the frequent participation in expensive proficiency tests.This approach is based on the development of a model of the performance of the analytical method based on the differential approach for the quantification of measurement uncertainty and on the comparison of recovery associated with each one of the analytical steps whose performance can vary with the analyte origin, for spiked and incurred samples.This approach was applied to the determination of pesticide residues in apples. For the analytes covered, no evidence was found that the studied sample processing and extraction steps performance for this matrix varies with the analyte origins.     

高效液相色谱二极管阵列检测器测定氯氰菊酯

本文采用高效液相色谱法和二极管阵列检测器，分离了农药氯氰菊酯的四个同分异构体，同时利用色谱保留值规律和光谱特征吸收曲线综合进行定性分析，记录了每个组分的峰上坡，峰顶和峰下坡三个不同部分在２２０－３２０ｎｍ波段的光谱叠合图并进行比较，以确定峰的纯度，并测定了异构体的顺反比例。     

Pesticide metabolites as contaminants of groundwater resources: assessment of the leaching potential of endosulfan sulfate, 2,6-dichlorobenzoic acid, 3,4-dichloroaniline, 2,4-dichlorophenol and 4-chloro-2-methylphenol

This study reports the results of K_oc and soil DT₅₀ experiments used for the definition of the leaching potential through the GUS Index of five metabolites: endosulfan sulphate (ES) from endosulfan, 2,6-dichlorobenzoic acid (DBA) from dichlobenil, 3,4-dichloroaniline (DCA) from propanil, 2,4-dichlorophenol (DCP) from 2,4-D and 4-chloro-2-methylphenol (CMP) from MCPA. The K_oc values for all the compounds were lower than 300, indicating high potential mobility in soil. Soil DT₅₀ values were around 24 days for DBA and ES, and <3 days for the other three metabolites. The leaching potential expressed by the GUS Index was high for DBA and ES (>2.8) and low to negligible for CMP, DCA and DCP (<0.32). In short, the intrinsic characteristics of DBA and ES are typical of leachers, but their significance as groundwater contaminants should be further surveyed through leaching in soil columns treated with their parent compounds.     

Pesticide residue analysis in food with CGC — study of long-term stability by the use of different injection techniques

An experiment was designed to study the long-term stability of analyses of pesticide residues in a complex food matrix using three different injection techniques. A spinach sample was spiked with five sulfur-containing pesticides of varying volatility and thermolability: azinphos-ethyl, dimethoate, methiocarb, ethiofencarb, and tri-allate. Tri-allate was selected as internal standard because of its thermal stability and its good chromatographic properties. Flame photometric detection resulted in chromatograms not subject to interference by peaks of compounds of the matrix. Starting with a clean and freshly, silanized injector an additional deactivation was found to occur on the first injection of a food sample resulting in an increased peak area for all pesticides in relation to tri-allate. Highest long-term stability was found with PTV injection. Best results for thermolabile carbamates were obtained using on-column injection. However, they were prone to faster deterioration.     

Qualitative and quantitative analysis of organophosphorus pesticide residues using temperature modulated SnO(2) gas sensor

Qualitative and quantitative analysis of organophosphorus pesticide residues (acephate and trichlorphon) using temperature modulated SnO₂ gas sensor were studied. The testing method employed only a single SnO₂-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of pure pesticide vapor and a binary vapor mixture in the air. Experimental results showed that in the range 250-300 °C and at the modulating frequency of 20 mHz the high selectivity of the sensor could be achieved. The quantitative analysis of the pure pesticide vapor and their mixture were performed by fast Fourier transformation (FFT). The higher harmonics of the FFT characterized the non-linear properties of the response at the sensor surface. The amplitudes of the higher harmonics exhibited characteristic variations that depend on the concentration and the kinetics of pesticide species on the sensor surface.     

底物固相分散法测定土壤中甲氰菊酯残留量

以甲氰菊酯为分析对象，将一种新型的样品预处理技术-底物固相分散法(MSPD)应用于测定土壤中农药残留。确定了MSPD法的实验条件：土壤量为4g，水的加入量为1mL，固相吸附剂弗罗里硅土的用量为10．0g，淋洗剂为15mL石油醚-乙酸乙酯(1 9)。土壤样品在此条件下处理后无需进一步净化即可用气相色谱／电子捕获检定器测定。三种土壤的三种加标水平的回收率均在90％以上，相对标准偏差小于5％(n＝5)，最小检出质量比为0．002mg/kg。     

Analyse von Organochlorpestizid-und PCB-Rückständen in Fischen mittels Kapillargaschromatographie/Massenspektrometrie

Zusammenfassung Es wird die Analyse neutraler organischer Chlorverbindungen in Fischen beschrieben. Die Methode umfaßt Extraktion, selektive Vortrennung und Bestimmung mittels GC/MS an Glastrennkapillaren. Weiter werden die Ergebnisse einer für oberösterreichische Flüsse typischen Fischprobe vorgestellt und diskutiert: Wie in den meisten Proben dieses Ursprungs findet man — im Vergleich zu einem Gehalt von 6.1 ppm PCB's — relativ wenig Pesticidrückstände. Der Chlorierungsgrad der gefundenen PCB's entspricht etwa dem von Aroclor 1254; die abweichende Isomerenverteilung deutet auf unterschiedliche Persistenz der einzelnen Isomere hin.

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Analysis of organochlorine pesticides and PCB residues in fish by capillary gas chromatography/mass

Summary The analysis of neutral organochlorine compounds in fish is described. The method includes extraction, selective clean-up and GC/MS determination using glass capillary columns. The results of a typical fish sample coming from Upper Austrian rivers are presented. In comparison with the detected concentration of 6.1 ppm PCB's relatively low amounts of pesticide residues were found. The degree of chlorination of these PCB's is similar to that of Aroclor 1254, but the isomeric distribution is quite different, indicating varying persistence of the distinct isomers.

     

Ion-pair,liquid chromatographic analysis of total gossypol in chicken liver

Summary An ion-pair, liquid chromatographic method for the determination of total gossypol in chicken liver has been developed. It involves hydrolysis of bound gossypol in the presence of ascorbic acid, partitioning into chloroform and isocratic separation on Spherisorb ODS2, 10 m, column with a methanol-water mobile phase containing octane-1-sulfonate. Precision data based on within-day and between-days variation suggested an overall relative standard deviation of 8.1%, while overall recovery was 81.1%±3.     

HPLC determination of pesticides in green bean samples after SPE clean-up

Summary A reversed-phase high performance liquid chromatographic (HPLC) method with an acetonitrile-methanol-water mobile phase gradient and photodiode-array detection (DAD) is described for simultaneous determination of 21 pesticides, frequently used in agriculture, of different types, namely organophosphorus, organochlorine,N-methylcarbamates, triazines and phenylureas in vegetable samples. The pesticides were extracted with acetone and then partitioned from the vegetable sample with dichloromethane. Sample clean-up was accomplished by solid-phase extraction (SPE) using both C₁₈ and florisil SPE columns. Average recoveries from green beans ranged from 70.0 to 110.1%. Detection limits of less than 0.1 mg kg^–1 were obtained.     

Determination of triazine herbicides by capillary gas chromatography with large-volume on-column injection

Summary This paper describes a study of the potential of large-volume on-column injection for the determination of triazine herbicides in clean water samples (ground-water). The sensitivity of chromatographic determination has been increased by two orders of magnitude by injection of up to 200 μL of pesticide solutions and nitrogen-phosphorus detection. Analytical characteristics expressed as precision, linear range and limit of detection have been determined, the results indicating adequate analytical performance and the ruggedness of the injection technique. As an application, gas chromatography with large-volume on-column injection and nitrogen-phosphorus detection was combined with off-line liquid-liquid micro-extraction with hexane (1 mL water/1 mL hexane). The procedure was applied to spiked groundwater samples at two concentration levels (1 and 10 μg L⁻¹) with good recoveries (between 81 and 103%, except for deethylatrazine) and repeatability (better than 15% at the 1 μg L⁻¹ level). Limits of detection of the triazine herbicides studied ranged from 0.08 to 0.16 μgL⁻¹.