Use of Polyacrylic Acid and Polydimethylsiloxane Mixture for In‐Needle Microextraction of Volatile Aroma Compounds in Essential Oils

A prototype stainless steel needle (Hamilton 90022, 22 gauge, 718 mu m o.d., 413 mu m i.d., 51 mm length, bevel tip) packed with polyacrylic acid (PAA) and polydimethylsiloxane (PDMS) mixture (7:3 ratio) having a micro-bore tunnel (290 mu m i.d., ca. 61.5 mu m thickness, 10 mm length) was newly prepared as a device of headspace in-needle microextraction (HS-INME). Design of the needle, optimization of adsorption, desorption parameters, and validation of analytical methods were conducted to evaluate the HS-INME efficiency for volatile organic compounds. The optimized adsorption conditions were 60 degrees C for 20 min and desorption conditions were 240 degrees C for 2 min. The calibration curves showed good linearity with the squared correlation coefficient value (r(2)) over 0.99. The limit of detection for linalool, (+)-limonene, and eugenol were 13.5, 10.9, and 9.1 ng while limit of quantification were 45.1, 36.4, and 30.5 ng, respectively. The recovery results showed the acceptable range between 95.6 and 115.3%. The relative standard deviations for intra- and inter-assay showed the values less than 10%. It was applied to analyze seven essential oils for polar and nonpolar volatile aroma compounds successfully. From the results obtained in this study, HS-INME was advantageous to low cost due to ease of fabrication, reuse without loss of absorbent or reduction of extraction efficiency, and no use of solvent. In conclusion, a needle packed with PAA and PDMS mixture having a micro-bore tunnel is a new development of INME that may complement the shortcomings of the current headspace extraction methods.