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

Abstract

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.

Rapid and Highly Sensitive Determination of Melamine in Different Food Samples by Corona Discharge Ion Mobility Spectrometry after Dispersive Liquid-Liquid Microextraction

“…After 15 min of centrifugation (rpm = 60000), the solution was filtered through a 0.2 µm filter, and the supernatant was transferred to a 10 mL volumetric flask for the extraction of MEL according to the proposed DLLME-CD-IMS method. 36 Cheese and yogurt sample A portion of sample (2.0 g) was added to a 50 mL centrifuge tube. To this was added 5% trichloroacetic acid in water (15 mL) and acetonitrile (5 mL), and the tube was then capped, sonicated for 10 min, placed on a vertical shaker for 10 min, and centrifuged for 10 min at 4000 rpm.…”

“…This mixture was vortexed and then used for the extraction of MEL according to the procedure described in the Extraction procedure section. 36 …”

Estratégias para aumento de sensibilidade e seletividade de separações cromatográficas em sistemas de análises em fluxo

“…Desta forma, vários procedimentos para a determinação de melamina nas mais diversas matrizes têm sido desenvolvidos, a maioria baseados em cromatografia líquida de alta eficiência [120][121][122][123][124]. Outros procedimentos empregando eletroforese capilar [112,119], cromatografia de íons [125], cromatografia a gás acoplada a espectrometria de massas [113], voltametria [117], espectrometria de massas MALDI-TOF [126], quimiluminescência [127,128], imunoensaios [129] e espectrometrias Ramam [110] e por fluorescência [130] foram desenvolvidos.…”

“…Outros procedimentos empregando eletroforese capilar [112,119], cromatografia de íons [125], cromatografia a gás acoplada a espectrometria de massas [113], voltametria [117], espectrometria de massas MALDI-TOF [126], quimiluminescência [127,128], imunoensaios [129] e espectrometrias Ramam [110] e por fluorescência [130] foram desenvolvidos. Estes procedimentos geralmente envolvem preparo de amostra demorado [126], incluindo etapas de extração e pré-concentração e em alguns casos, alto consumo de solventes orgânicos [120][121][122][123][124]. Neste contexto, as técnicas de análises em fluxo apresentam características atrativas, sendo uma opção conveniente para o desenvolvimento de novos procedimentos para a determinação de melamina.…”

“…Em alguns casos, uma etapa adicional de extração em fase sólida é necessária para a remoção de gorduras [114,[119][120][121]123,124]. Dentre os procedimentos apresentados, o preparo de amostra mais simples para análise de melamina se baseia na dissolução da amostra em uma solução de SDS em tampão fosfato pH 3,0 [114].…”