| Objectives A simple and highly sensitive analytical methodology for simultaneously isolation and determination of four phthalate acid esters in water and beverage samples, based on dispersive liquid-liquid microextraction (DLLME) using high-performance liquid chromatography (HPLC) with ultraviolet detection was developed. Three phthalate acid esters, benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diethylhexyl phthalate (DEHP) were chosen as target analytes. One variable at a time optimization were used to obtain optimum conditions for microextraction procedure. Centralized water-supply, bottle water, and beverage sold in Jinan were also sampled and determinated by the developed DLLME-HPLC method. Advice would be given to the authorities after analysing the data obtained.Methods1. Sample pretreatmentWater samples were carried by dispersive liquid-liquid microextraction directly; Juice samples were centrifuged at 4000 rpm for 3 min before DLLME in order to remove the colloid composition might affect extraction procedure.2. Dispersive liquid-liquid microextraction procedureA 6.0mL sample solution was placed in a 10 mL glass tube with conical bottom. 300 μL methanol (as disperser solvent), containing 90 μL tetrachloroethylene (as extraction solvent) was injected rapidly into the sample solution using a 1.5 mL glass syringe. In this step, a cloudy solution (water/acetonitrile/IFs) was formed in the test tube and the PAEs in the water sample were extracted into fine tetrachloroethylene droplets. The mixture was then centrifuged for 2 min at 4000 rpm, and the extraction solvent deposited at the bottom. The upper aqueous solution was removed and the residue was blown with mild nitrogen stream. The sediment phase was completely dissolved in 50 μL acetonitrile. After 20 seconds on vortex mixer,10 μL of the mixture containing four plasticizers was injected into HPLC system for analysis.3. Chromatographic conditionsSeparation and determination of four PAEs were carried out on an HPLC system (LC-20A, Shimadzu, Japan) equipped with a diode array detector (SPD-M20A, Shimadzu, Japan). All injections were performed manually with 20.0 μL sample loop. A HITACHI-C18 column (250×4.6 mm I.D.,5 μm) was employed at 30℃. Detection was performed at γ= 203 nm. Simultaneous separation of the four PAEs was achieved with a water-acetonitrile mobile phase, and the gradient contained the following steps:0-12 min, from 75% acetonitrile to 100%; 12-21 min, maintaining 100% acetonitrile; 21-25 min,100% acetonitrile to 80%. The flow rate of mobile phase was 1.2 mL/min.4. Sampling methodWater samples collection, preservation and transportation were conducted according to GB/T 5750.2-2006 The standard testing method of drinking water,the collection and preservation of water sample.5. EvaluationThe statistical description and analysis of variance (p<0.05) were conducted to compare the indicators of water samples and beverage samples from different sources.Results1. Under optimum conditions, recoveries in the ranges of 85.3-103.3% were obtained, RSD(relative standard deviation) was 2.4%-5.6%; Calibration curves showed high levels of linearity in the range of 0.50-400.0 ng/mL (r> 0.9998) for benzyl butyl phthalate (BBP), and 0.250～400.0 ng m/L (r> 0.9993) for dibutyl phthalate (DBP), diethylhexyl phthalate (DEHP).2. Several of the 3 target analytes in Centralized water-supply was out of limits; noneof the beverage samples and bottle water samples exceeded limits while concentrations of the plasticizers in beverage were tens of times higher than that in water.ConclusionThe method was applied for the analysis of real samples, and proved to be very efficient, sensitive, less pollutional and easy to operate. Pollution of the phthalate esters in Jinan was generally satisfied. Yet part of the surface water, and bottle water sample sampled exceeded national standard. |
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