Resins base extraction cleanup procedure

Broad Spectrum Analysis of Resin Extracts A Base Extraction Cleanup Procedure... 

This chapter describes the simpler cleanup approach of base extraction for XAD resin extracts. Quality assurance procedures statistically define the benefits of this analytical approach for broad spectrum capillary GC. The extraction procedure was optimized by studying UV absorbance of the base extractant. 

The cleanup procedure used was discussed in the section entitled Resin Elution Concentration. The extraction procedure was not the optimum procedure that would result from the observations. The data indicated that a base extraction at pH >12 and a base-to-solvent ratio of 15 1 with multiple extraction steps were needed to maximize removal of the matrix interferences. However, the extraction efficiency must be balanced against minimal sample destruction and operational ease. 

A resin to be cleaned was packed into a 3-L capacity addition funnel and washed first with two volumes of high-purity water. The MSC-1 resin was then washed sequentially with 2 bed volumes of 2.0 N HC1, 5 bed volumes of high-purity water, 2 bed volumes of 1.5 N NaOH, and 5 bed volumes of high-purity water these HC1, water, NaOH, and water washes were then repeated. The same procedure was carried out with A-162, except that the order of acid and base was reversed. The resins were then extracted for at least 16 h in methanol in a Soxhlet apparatus. The final cleanup steps for MSC-1 consisted of a sequential elution with 2 bed volumes of methanol, 1 bed volume of 1.0 N NH3 in 122 methanol/882 methylene chloride (made as described later), 2 bed volumes of 122 methanol/882 methylene chloride (solvent 1), and 3 bed volumes of methanol. The same steps were used with A-162 except that HC1 replaced NH3 in the second wash. The resins were considered to be clean at this point, and they were stored in methanol. 

---