Marcello. Marchetti

Rapid determination of simazine and atrazine in water at the parts per trillion (1012) level : Extraction by a miniaturized carbopack B trap followed by high-performance liquid chromatography

A rapid and simple method for the determination of trace amounts of simazine and atrazine in water is described. A 250-ml volume of water is pre-concentrated by passage at a flow-rate of about 30 ml/min through a small trap containing 50 mg of graphitized carbon black (Carbopack B). After washing with 150 microliters of methanol, the two herbicides are desorbed with 700 microliters of dichloromethane-methanol (60:40, v/v). After removal, of the solvent, the extracted sample is fractionated and analysed by reversed-phase high-performance liquid chromatography with UV detection at 220 nm. A single assay can be completed within 40 min from the receipt of the water sample. Recoveries of simazine and atrazine added to 250 ml of water at the level of 50 ng/l were 97.2 and 95.8% and the limits of detection were 0.07 and 0.15 ng. respectively. At the 50 ng/l level in water, the coefficients of variation for simazine and atrazine were 3.7 and 4.0% (n = 7), respectively.

Rapid and sensitive determination of phenylurea herbicides in water in the presence of their anilines by extraction with a Carbopack cartridge followed by liquid chromatography

A rapid and sensitive method for determining phenylurea herbicides in environmental aqueous samples in the presence of their anilines is described. The water sample is preconcentrated by passage at a flow-rate of ca. 150 ml/min through a 250-mg graphitized carbon black (Carbopack B) cartridge. After washing with 0.6 ml of methanol, the Carbopack B trap is connected with a cartridge containing a strong cation exchanger. Organics trapped by the Carbopack cartridge are eluted by passage of 6 ml of methylene chloride-methanol (95:5, v/v). Anilines and other basic compounds are quantitatively subtracted from the solvent system while flowing through the cation-exchange cartridge. After evaporation and redissolution, the sample is subjected to reversed-phase gradient elution high-performance liquid chromatography with UV detection at 250 nm. Recoveries of phenylureas added to water at levels between 30 and 3000 ng/l were higher than 92%. The limit of detection was about 1 ng/l, for a 2-1 sample. With respect to an octadecyl (C18)-bonded silica cartridge, the Carbopack B cartridge had a far better extraction efficiency for polar phenylureas.

High-performance liquid chromatographic method for determining triazine herbicide residues in soil

Abstract The extraction of eight triazines from soil and their isolation from the soil extract were simultaneously performed using two mini-columns connected in series, one containing the soil sample and the other filled with a strong acid exchanger. By allowing 3 ml of acetone to flow along the two cartridges in tandem, triazines were removed from the soil particles and then selectively readsorbed via salt formation on the exchanger surface. After disconnecting the two cartridges, the triazines were eluted from the exchanger trap by potassium chloride-saturated methanol. This procedure was also adopted to desorb from the soil surface residual amounts of chemically adsorbed triazines, which acetone is unable to remove. After removal of methanol from the two combined eluates, the triazines were fractionated and quantified by reversed-phase high-performance liquid chromatography with UV detection at 220 nm. Using this procedure, the recoveries of triazines were greater than 90% and independent of the triazine concentration, the type of soil samples and their ageing on storage. The mean limit of detection was about 1 ng/g in soil. The results obtained were compared with those obtained by two techniques of known efficiency (reflux extraction and Soxhlet extraction). Some effects on the adsorption of triazines of the type of soil and its ageing on storage are discussed.

Antidepressants in serum determined by isolation with two on-line sorbent cartridges and liquid chromatography

A selective method for measuring tricyclic antidepressants in serum is reported. A single assay can be done within ca. 30 min and eight samples can be assayed in less than 150 min. A 1-ml serum sample was diluted and the drugs were extracted from it by passage through a graphitized carbon black (Carbopack B) cartridge. After one washing, this cartridge was connected on line to another one containing a silica-based strong acid exchanger. The tricyclics were removed from the Carbopack surface and selectively readsorbed onto the cation-exchange surface by passing 4 ml of methylene chloride-methanol (60:40, v/v) through the two cartridges. After another wash, the drugs were desorbed from the cation-exchange surface with 0.8 ml of acetonitrile-methanol-water (72:18:10, v/v) saturated with potassium chloride. An aliquot of this solution was chromatographed on a cyano column, and the absorbance of the effluent was measured at 215 nm. The mean analytical recoveries of tricyclic antidepressants added to serum within the range 10-200 micrograms/l exceeded 90%, except for 8-hydroxyamoxapine (mean recovery 85.3%) and amoxapine (mean recovery 83.8%) at the lowest serum concentration considered.

Assay for urinary estriol during the menstrual cycle based on extraction by a graphitized carbon black cartridge followed by high-performance liquid chromatography

SummaryA high-performance liquid chromatography (HPLC) assay for estriol in nonpregnancy urine is described. After Enzymic hydrolysis, the estriol is extracted from urine by the sorbent trap technique utilizing graphitized carbon black (Carbopack B). After some washing steps, estriol is desorbed by a suitable solvent system. After solvent removal, the sample is injected into an HPLC column for estriol quantification. Analytical recovery of estriol was 96.1%. The precision of the method was 2.6 and 4.9% respectively at 145 and 10.6ng/ml of urine. The limit of sensitivity was set at 0.8 ng/ml of urine. The mean contents of estriol in the follicular and luteal phases were respectively 11.3 and 38.8 ng/ml of urine.

Multi-Component Analysis of Pesticides in Water Samples by Hplc. Rapid Extraction and Neutral/Acid Fractionation by a Carbopack Cartridge

A liquid-solid extraction procedure for isolation of 70 pesticides from ground and tap waters for high-performance liquid chromatography (HPLC) is presented. This simple and rapid procedure involved passing a 2-L sample through a 250-mg graphitized carbon black (Carbopack B) cartridge at a flow-rate of 120-140 mL/min. By exploiting the presence of positively charged active centers on the Carbopack surface, a stepwise elution system allowed the complete separation of basic/neutral pesticides from acidic ones. After partial solvent removal, the two classes of pesticides were subfractionated and quantified by gradient elution, reverse-phase HPLC with UV detection. The performance of the Carbopack cartridge was compared to that of a 500-mg C-18 bonded silica cartridge. With the Carbopack cartridge, the grand mean measurement accuracy of the 70 analytes was 95.5% with a mean relative standard deviation (RSD) of 1.26%. With the C-18 cartridge, the grand mean measurement accuracy of the analytes was 72.8%, with a mean RSD of 7.91%. Compared to the C-18 cartridge, additional advantages on using a Carbopack cartridge are that the extraction procedure is about seven times shortened, no pH adjustment of the environmental sample is necessary for trapping acidic compounds, one cartridge instead of two suffices to extract basic, neutral and acidic pesticides. The detection limits by this method of all the pesticides considered were between 0.2 and 25 ng/L (signal to noise ratio 3).