Low-density Dispersive Liquid-liquid Microextraction Research Articles

VALIDATION OF AN ANALYTICAL METHOD FOR THE DETERMINATION OF FATTY ACIDS IN SHEEP BLOOD SERUM SAMPLES

Low-density dispersive liquid-liquid microextraction with a subsequent esterification step was proposed in this study for the determination of linoleic acid and stearic acid in sheep blood serum samples. The method developed aimed to quickly and efficiently extract and esterify both fatty acids with subsequent analysis by gas chromatography/flame ionization detection. The extraction method was optimized with Scheffé’s polynomial model for three-component mixtures. The method was validated according to the parameters established by Eurachem Guide (2014). The optimal extraction conditions for LD-DLLME were 1400 µL of dispersion medium (MgCl2 0.017%), 400 µL of extractor solvent (toluene) and 1200 µL of dispersion solvent (methanol). The method performance showed adequate selectivity, sensitivity and precision to be applied to real samples, with an average recovery of 98.54% for linoleic acid and 103.83% for stearic acid. LD-DLLME was superior to the traditional method of analysis, which has been used until now for the determination of fatty acids in blood serum samples from ruminants. The analysis of real samples showed that the developed method is efficient for monitoring these substances in ruminants.

DLLME coupled with HPLC-DAD for enrichment of pesticide residues in environmental sediment and soil samples

Sample pre-treatment during determination of pesticides in sediment and soil is difficult due to matrix effects. For this reason, a low density dispersive liquid-liquid microextraction (ld-dllme) was developed for the determination of carbaryl, cynazine, atrazine, and propazine. The experimental parameters that could potentially influence performances of the developed analytical technique including the extraction solvent type and volume, disperser solvent type and volume, extraction and centrifugation time, centrifugation speed, salt concentration, and pH were optimized. The optimum experimental values were found to be 50 mL 1-octanol, 0.6 mL acetonitrile, 5 min extraction time, centrifugation at 3500 rpm for 3 min, 10% NaCl and pH 5. At the optimum conditions, the methods offer good linearity (R2 = 0.998–0.999) for the concentration ranges of 30-800 µg/kg; the detection limit (lod) ranging from 9-24 µg/kg; precision <5.3% rsd, and reproducibility 0.5-5.2% rsd. The accuracy of the method, determined in terms of recovery was found to vary from 74.5-109.7%. Therefore, the developed analytical method could be used for the determination of trace level of pesticides residues in sediment and agricultural soil samples.

SALLE combined with LD-DLLME for pesticides analysis in sugar and soil samples

In this study, a modified salting-out-assisted liquid-liquid extraction (SALLE) combined with low density dispersive liquid-liquid microextraction (LD-DLLME) has been developed for quantitative determination of multiclass pesticide residues (atrazine, diazinon, ametryn, terbutryn, chlorpyrifos, dimethametryn, 4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE), 4,4'-dichlorodiphenyldichloroethane (4,4'-DDD) and 4,4'-dichloro- diphenyltrichloroethane (4,4'-DDT)) levels in sugar and soil samples coupled with gas chromatography–mass spectrometry (GC-MS) detection. The extract was enriched after combining SALLE to LD-DLLME and enrichment factor obtained ranged 30-121. Under the optimum conditions, the linearity of the method was in the range of 6.25–100 ng g-1 for atrazine, ametryn, terbutryn, dimethametryn and 4,4'-DDT, and in the range of 2.5–100 ng g-1 for diazinon, chlorpyrifos and 4,4'-DDD, and in the range of 1–100 for 4,4'-DDE with correlation coefficient of 0.992 or better. The limits of detection (LODs) ranged from 0.01–0.25 ng g-1. The precisions as %RSD, were below 10% for both matrices. The recoveries obtained from spiked sugar and soil samples at 5 and 50 ng g-1 ranged from 79 to 111%. The method was subsequently applied to real sugar and soil samples. All the pesticides investigated were not detected in the sugar sample. The soil sample was contaminated by atrazine and ametryn at concentration level of 0.3 and 0.2 ng g-1, respectively.
 
 KEY WORDS: SALLE, LD-DLLME, Extraction, Pesticide residues, Sugar, Soil
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 1-16.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.1

Moore–Penrose generalized inverse mixture design applied in low‐density dispersive liquid–liquid microextraction

AbstractThe modification in the nutritional composition of the ruminant diet causes significant alterations in the fatty acids (FAs) structure supplemented because of the action of rumen microorganisms. The modification in the FAs structure alters the role that these play in the ruminant metabolism. The Folch method is the most often used to determine fatty acids in these animals' tissues and presents certain disadvantages such as the great volume of solvent and low mass transfer from the analyte to the extracting phase. Thus, we tested the low‐density dispersive liquid–liquid microextraction (LD‐DLLME) as an alternative method to determine these substances. In this paper, a simples‐augmented mixture design was used. The Scheffé's polynomial was applied in that design, and Moore–Penrose generalized matrix inverse was used because of the possibility of concurrently determining value estimates of coefficients of the parameters that represent cubic terms. The application of the modeling allowed the chemical interpretation of the LD‐DLLME best extraction condition for linoleic acid in ruminant serum samples.

Application of D-Limonene as a Bio-based Solvent in Low Density-Dispersive Liquid-Liquid Microextraction of Acidic Drugs from Aqueous Samples.

This study deals with the application of different monoterpenes as relatively green bio-based solvents for low density-dispersive liquid-liquid microextraction (LD-DLLME) of different non-steroidal anti-inflammatory drugs (NSAIDs) from aqueous samples in comparison with conventional halogenated solvents. Results indicated that D-limonene could extract the hydrophobic compounds with higher %recovery compared with other bio-based and halogenated solvents. The LD-DLLME procedure was optimized by applying one-factor-at-a-time (OFAT) followed by central composite face-centered design (CCF) of the response surface methodology (RSM). Under the optimal conditions, the method exhibited good linearity with r ≥ 0.9950 with low LOD as well as LOQ levels in the range of 0.11 to 0.81 and 0.36 to 2.69 ng/mL, respectively. The method was efficiently applied to a variety of real aqueous samples. Finally, the green aspect of our procedure was compared with some reported methods using two green metric tools.