Residual solvents analysis instrumentation

A transmission pair analyzer combines the advantages of laboratory NIR analysis in a process instrument. The NIR monochromator is interfaced to the process via fiber-optic bundles and stainless steel transmission probes. This instrument is used primarily for on-line investigations of pilot plant or production plant applications. Typical applications include monomer moisture content, residual solvents, and solids content in polymerization processes, and solvent and solutions compositions in continuous chemical processes. 

Collect the ACN in a PP tube. Add another 15 ml of ACN to sample residue and shake, centrifuge and elute through the above florisil/carbon column. Combine the 2 ACN eluates. Then elute with 5 ml methanol through the column. Combine ACN and methanol (total 50 ml) and blow it down to dryness under a gentle stream of nitrogen. Reconstitute the solvent with 1ml methanol and filter it through the nylon filter, prior to instrumental analysis. 

Evaporate the organic solvent under a nitrogen stream and redissolve the residue in 1-3 ml hexane. Transfer 100 pi to a GC vial and cap for analysis. The exact volumes for this step have to be determined empirically and are dictated by the sensitivity and injection settings of individual GC instruments. 

A simple first strategy to recover residues for ELA is to try existing multiresidue methods, or to use solvents and solid-phase extraction media that have proven satisfactory in the first steps of more involved instrumental analyses. This approach makes the transition from instrumental methods to ELA easier for technical personnel, and it facilitates confirmatory instrumental analysis during method validation. The uncommon structure of avermectin antibiotics makes it very unlikely that the ELA would detect compounds other than an avermectin in multi-residue extracts, though this remains to be tested. The greater concerns are completeness of the extractions, efficiency and reproducibility of recoveries, and freedom from non-specific matrix effects and interference by solvents. 

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