Syringe,contaminated,effect

A solvent blank is used to eliminate the possibility of contamination arising from outside the sample, for example, from the syringe or from the instrument. It is recommended to use the sample solvent as solvent blank and run this test at the beginning and at the end of each sample series and whenever contamination is suspected. The memory effect is possible, for example, in the analysis of alkyl phosphonic acids. If the derivatization of these chemicals has not been complete, the nonderivatized acids are adsorbed on the injector liner. A silylation reagent may in such case react in situ with the adsorbed acids in the liner yielding false positive results. 

Injection is not usually an important route of unintentional toxic exposure because chemists don t routinely use needles and syringes. However, this route is possible if a glass container breaks and creates a shard or sliver of glass contaminated with this toxic chemical. If this sticks into your body, some of the chemical could be injected. However, only the most toxic chemicals could be received in a dose sufficient to cause a toxic effect. 

If the dirt or contaminant spots can be dissolved in a low boiling-point solvent, solvent extraction (removal) may be an effective method for collecting the sample. If the base plate is a plastic material, the solvent must be carefully selected to ensure that none of the polymer support is dissolved. The solution obtained may then be slowly dripped from a syringe onto a thin film, for example, of polyethylene or polytetrafluoroethylene, and after the solvent has evaporated completely, the remaining powder can then be made into a KBr disk. If the solution is dropped directly onto an infrared-transparent window or a metal plate, the spot often tends to spread to form a circle of the sample after evaporation of the solvent, making the sample then not suitable for either the transmission or transmission-reflection measurement method. If the solution is dropped into a small hole (for example, with a diameter of 1 mm and a depth of 3 mm drilled into a metal support) filled with KBr powder, a diffuse-reflection spectrum may be measured from this after complete evaporation of the solvent. 

---