Quantitative ion intensities obtained for the three derivatization products.

<p>Quantitative ion intensities obtained for the three derivatization products.</p

Detection of Melamine in Feed Using Liquid-Liquid Extraction Treatment Combined with Surface-Enhanced Raman Scattering Spectroscopy - Figure 7

<p>(A)SERS spectra of different melamine concentrations in spiked feed samples: (a) blank, (b) 2, (c) 4, (d) 6, (e) 8, and (f) 10 µg·g⁻¹ (<b>B</b>) Melamine concentration fortified in feed−response curve for feed samples spiked with melamine in the range 2–10 µg·g⁻¹.</p

SERS spectra of samples pretreated by liquid-liquid extraction per number of extraction cycles.

<p>SERS spectra of samples pretreated by liquid-liquid extraction per number of extraction cycles.</p

SERS spectra: blanks, standards, and representative samples.

<p>The SERS spectra of (a) synthesized AuNPs; (b) synthesized AuNPs after the addition of 1% NaCl; (c) blank feed (after sample treatment); (d) melamine standard solution (1 µg·mL⁻¹); (e) feed sample spiked with melamine (2 µg·g⁻¹); and (f) feed sample spiked with melamine (5 µg·g⁻¹).</p

Repeatability of the reported method and the method described in Bulletin 1063-7-2008.

<p>Repeatability of the reported method and the method described in Bulletin 1063-7-2008.</p

Three derivatization reactions of clenbuterol.

<p>Three derivatization reactions of clenbuterol.</p

SERS spectrum of a feed sample extract spiked with melamine (10 µg·mL⁻¹) using trichloroacetic acid as extraction solvent and double liquid-liquid extraction pretreatment.

<p>SERS spectrum of a feed sample extract spiked with melamine (10 µg·mL⁻¹) using trichloroacetic acid as extraction solvent and double liquid-liquid extraction pretreatment.</p

Dependence of reaction (a) temperature and (b) time on quantitative ion intensity.

<p>Dependence of reaction (a) temperature and (b) time on quantitative ion intensity.</p

Comparison of results obtained by GC/MS and SERS in 40 feed samples.

a<p> Not detected means the melamine content was below the LOD of the method (0.05 µg·g⁻¹).</p>b<p> A negative result means the content of melamine in the sample was below a concentration of 2.5 µg·g⁻¹.</p><p>Comparison of results obtained by GC/MS and SERS in 40 feed samples.</p

GC-MS/MS (SRM mode) chromatographs of 20 β-agonists.

<p>GC-MS/MS (SRM mode) chromatographs of 20 β-agonists.</p