Microextraction technique associated with gas chromatography-mass spectrometry for determining pesticide residues in urine

Urine is one of the biological matrices most used for detecting human contamination, as it is representative and easily obtained via noninvasive sampling. This study proposes a fast, accurate, and ecological method based on liquid-liquid microextraction with low-temperature partition (μLLE/LTP). It was validated to determine nine pesticides (lindane, alachlor, aldrin, chlorpyrifos, dieldrin, endrin, DDT, bifenthrin, and permethrin) in human urine, in association with gas chromatography coupled with mass spectrometry (GC-MS). The technique was optimized through a factorial design. The best conditions for the simultaneous extraction of the analytes comprised the addition of 600 µL of water and 600 µL of acetonitrile (extracting solvent) to a 500-µL urine sample, followed by vortexing for 60 s. By freezing the samples for 4 h, it was possible to extract the pesticides and perform the extract clean-up simultaneously. The parameters selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy were used to appraise the performance of the method. Good values of selectivity and linearity (R² > 0.990), LOQ (0.39-1.02 μg L^-1), accuracy (88-119% recovery), and precision (%CV ≤ 15%) were obtained. The μLLE/LTP-GC-MS method was applied to authentic urine samples collected from volunteers in Southeast Brazil.

Method development for simultaneous determination of polar and nonpolar pesticides in surface water by low-temperature partitioning extraction (LTPE) followed by HPLC-ESI-MS/MS

During this research, chemometric approaches were applied for optimization of the low-temperature partitioning extraction (LTPE) for the simultaneous analysis of the pesticides: acephate, difenoconazole, fenamidone, fluazifop, fluazinam, methamidophos, and thiamethoxam from surface water samples and determination by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. It was used the 2³ full factorial and the Doehlert experimental designs. The extraction technique was optimized by evaluating the effects of the three variables: sample pH, ionic strength (addition of Na₂HPO₄), and organic solvent volume. Considering the interest to find an optimal condition for all analytes simultaneously, the best extraction parameters found were as follows: pH = 5.33, concentration of Na₂HPO₄ = 0.0088 mol L^-1 and organic phase volume = 4.5 mL. The optimized methodology showed LOD and LOQ levels from 0.33 to 8.13 ng L^-1 and from 1.09 to 26.84 ng L^-1, respectively. The recovery values ranged from 38.37 and 99.83% and the RSD values varied from 2.33 to 18.92%. The method was applied to surface water analysis sampled in areas with intensive agricultural practices in Ouro Branco City, Minas Gerais, Brazil. The difenoconazole was detected in concentrations between 12.53 and 94.76 ng L^-1.

Determination of nine pharmaceutical active compounds in surface waters from Paraopeba River Basin in Brazil by LTPE-HPLC-ESI-MS/MS

A simple, inexpensive, versatile, and environment-friendly extraction method, using low-temperature partitioning extraction (LTPE), was validated to quantify pharmaceutical-active compounds (PhACs) in surface water samples by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The PhACs analyzed were acetaminophen, bezafibrate, diclofenac, diltiazem, fluconazole, linezolid, miconazole, ondansetron hydrochloride, and trimethoprim. The detection and quantification limits ranged from 0.15 to 12.30 ng L^-1 and 0.43 to 40.60 ng L^-1, respectively. Recovery rates ranged from 46 to 135%, and relative standard deviation (RSD%) varied between 0.49 and 6.13%. This method was applied to monitor water contamination by PhACs in the Paraopeba River Basin (PRB), Minas Gerais state, Brazil. All PhACs, except linezolid which was not detected, were found in PRB water samples in concentrations that ranged from 2.6 ng L^-1 to 2.62 μg L^-1.

Quantitative analysis of benzodiazepines in vitreous humor by high-performance liquid chromatography

OBJECTIVE

Benzodiazepines are frequently screened drugs in emergency toxicology, drugs of abuse testing, and in forensic cases. As the variations of benzodiazepines concentrations in biological samples during bleeding, postmortem changes, and redistribution could be biasing forensic medicine examinations, hence selecting a suitable sample and a validated accurate method is essential for the quantitative analysis of these main drug categories. The aim of this study was to develop a valid method for the determination of four benzodiazepines (flurazepam, lorazepam, alprazolam, and diazepam) in vitreous humor using liquid-liquid extraction and high-performance liquid chromatography.

METHODS

Sample preparation was carried out using liquid-liquid extraction with n-hexane: ethyl acetate and subsequent detection by high-performance liquid chromatography method coupled to diode array detector. This method was applied to quantify benzodiazepines in 21 authentic vitreous humor samples. Linear curve for each drug was obtained within the range of 30-3000 ng/mL with coefficient of correlation higher than 0.99.

RESULTS

The limit of detection and quantitation were 30 and 100 ng/mL respectively for four drugs. The method showed an appropriate intra- and inter-day precision (coefficient of variation < 10%). Benzodiazepines recoveries were estimated to be over 80%. The method showed high selectivity; no additional peak due to interfering substances in samples was observed.

CONCLUSION

The present method was selective, sensitive, accurate, and precise for the quantitative analysis of benzodiazepines in vitreous humor samples in forensic toxicology laboratory.

Quantitative analysis of benzodiazepines in vitreous humor by high-performance liquid chromatography

Objective:

Benzodiazepines are frequently screened drugs in emergency toxicology, drugs of abuse testing, and in forensic cases. As the variations of benzodiazepines concentrations in biological samples during bleeding, postmortem changes, and redistribution could be biasing forensic medicine examinations, hence selecting a suitable sample and a validated accurate method is essential for the quantitative analysis of these main drug categories. The aim of this study was to develop a valid method for the determination of four benzodiazepines (flurazepam, lorazepam, alprazolam, and diazepam) in vitreous humor using liquid–liquid extraction and high-performance liquid chromatography.

Methods:

Sample preparation was carried out using liquid–liquid extraction with n-hexane: ethyl acetate and subsequent detection by high-performance liquid chromatography method coupled to diode array detector. This method was applied to quantify benzodiazepines in 21 authentic vitreous humor samples. Linear curve for each drug was obtained within the range of 30–3000 ng/mL with coefficient of correlation higher than 0.99.

Results:

The limit of detection and quantitation were 30 and 100 ng/mL respectively for four drugs. The method showed an appropriate intra- and inter-day precision (coefficient of variation < 10%). Benzodiazepines recoveries were estimated to be over 80%. The method showed high selectivity; no additional peak due to interfering substances in samples was observed.

Conclusion:

The present method was selective, sensitive, accurate, and precise for the quantitative analysis of benzodiazepines in vitreous humor samples in forensic toxicology laboratory.