Double surfactants-assisted electromembrane extraction of cyromazine and melamine in surface water, soil and cucumber samples followed by capillary electrophoresis with contactless conductivity detection

BACKGROUND

Cyromazine (CYR) and its main degradation product melamine (MEL) are attracting wide attention due to their potential hazards to the environment and humans. In this work, double surfactants-assisted electromembrane extraction (DS-EME) by Tween 20 and alkylated phosphate was firstly used for purification and extraction of CYR and MEL, and the extract was directly analyzed by capillary electrophoresis with capacitively coupled contactless conductivity detection.

RESULTS

Under the optimum conditions, two targets could be well separated from the main interferences, including common biogenic amines and inorganic cations within 14 min. This developed method was successfully applied to the analyses of surface water, soil and cucumber samples, and the average recoveries were in the range 93.3-112%. DS-EME provided a synergistic purification and enrichment effect for CYR and MEL by adding Tween 20 and alkylated phosphate into donor phase and supporting liquid membrane, respectively. Satisfactory limits of detection [0.2-1.5 ng mL^-1 , signal-to-noise ratio (S/N) = 3] could be obtained in the tested sample matrices, and the corresponding enrichment factors were up to 115∼123 times.

CONCLUSION

This developed method provides an alternative for the simultaneous analysis of CYR and MEL in complex real-world samples. © 2019 Society of Chemical Industry.

Determination of polycyclic aromatic hydrocarbons in fresh milk by hollow fiber liquid-phase microextraction-gas chromatography mass spectrometry

In this work, a two-phase hollow fiber liquid-phase microextraction (HF-LPME) method combined with gas chromatography-mass spectrometry (GC-MS) is developed to provide a rapid, selective and sensitive analytical method to determine polycyclic aromatic hydrocarbons (PAHs) in fresh milk. The standard addition method is used to construct calibration curves and to determine the residue levels for the target analytes, fluorene, phenanthrene, fluoranthene, pyrene and benzo[a]pyrene, thus eliminating sample pre-treatment steps such as pH adjustment. The HF-LPME method shows dynamic linearity from 5 to 500 µg/L for all target analytes with R(2) ranging from 0.9978 to 0.9999. Under optimized conditions, the established detection limits range from 0.07 to 1.4 µg/L based on a signal-to-noise ratio of 3:1. Average relative recoveries for the determination of PAHs studied at 100 µg/L spiking levels are in the range of 85 to 110%. The relative recoveries are slightly higher than those obtained by conventional solvent extraction, which requires saponification steps for fluorene and phenanthrene, which are more volatile and heat sensitive. The HF-LPME method proves to be simple and rapid, and requires minimal amounts of organic solvent that supports green analysis.

Determination of melamine in milk and dairy products by high performance liquid chromatography

A simple, precise, accurate, and validated reverse-phase HPLC method was developed for the determination of melamine in milk (pasteurized and UHT milk) and dairy products (powdered infant formula, fruit yogurt, soft cheese, and milk powder). Following extraction with acetonitrile:water (50:50, vol/vol), samples were purified by filter (0.45 μm), separated on a Nucleosil C8 column (4.6 mm × 250 mm, 3 μm) with acetonitrile:10 mmol/L sodium L-octane sulfonate (pH 3.1; 15:85, vol/vol) as mobile phase at a flow rate of 1 mL/min, and determined by a photodiode array detector. A linear calibration curve was obtained in the concentration range from 0.05 to 5 mg/kg. Milk and dairy products were fortified with melamine at 4 levels producing average recovery yields of 95 to 109%. The limits of detection and quantification of melamine were 35 to 110 and 105 to 340 μg/kg, respectively. The method was then used to analyze 300 samples of milk and dairy products purchased from major retailers in Turkey. Melamine was not found in infant formulas and pasteurized UHT milk, whereas 2% of cheese, 8% of milk powder, and 44% of yogurt samples contained melamine at the 121, 694±146, and 294±98 μg/kg levels, respectively. These findings were below the limits set by the Codex Alimentarius Commission and European Union legislation. This is the first study to confirm the existence of melamine in milk and dairy products in Turkey. Consumption of foods containing these low levels of melamine does not constitute a health risk for consumers.