Assembly of Hyphenated Instrument of Solid Phase Extraction and Solid Phase Spectroscopy and Its Application to Determination of Rhodamine B in Food

An automatic analyzer was designed and fabricated by organic combination of solid phase extraction unit using filtering membrane as enrichment medium and diffuse reflection absorption spectrometry as detection unit, and the instrument was applied to the determination of rhodamine B in food. The analyzer consists of 3 parts:the solid phase extraction unit, the solid phase spectroscopy unit and the software. The sample solution (with its pH adjusted to 2.00) was introduced into the analyzer under reduced pressure and passed through the filtering membrane at an appropriate flow rate by adjusting the vacuum and the analytes were enriched on the membrane, which was then dried by hot air current. The information of diffuse reflection spectrometric data of the analytes was collected by the integrator from the solid phase of the dried membrane. The control conditions of the instrument, collection of spectral data, data treatment and finally the report of analytical results were completely controlled by the software. In the analysis of chilli, 0.500 g of the sample was taken and extracted ultrasonically with 50.0 mL of water for 10.0 min, and after centrifuging, the supernatant was taken for determination of rhodamine B. Mixed cellulose membrane was selected for enrichment, and the wavelength at 546.7 nm was chosen for determination. Linearity range of rhodamine B was found in the range of 5.0-15.0 μg·L^-1. For analysis of red tea sample, the sample should be diluted 10 times with water. In the presence of the matrix of red tea, linearity range of rhodamine B was found in the range of 10.0-30.0 μg·L^-1. Test for recovery was made by standard addition method for both the samples, giving values of recovery in the range of 88.0%-108%. Values of RSDs (n=5) found were in the range of 4.6%-9.3%.