Question

During their vacation, the Baldwin Family hired contractors to repaint their house. One warm afternoon, fire broke out on one side of the house and the house burned to the ground. The painters had left linseed oil soaked rags out near the house, which they had been using to finish the wood deck. An arson investigator was sent out to investigate whether the fire could have been deliberately set. How could the lab technician determine whether the fire was accidental (or not)? Clearly describe what kinds of samples would need to be collected and what kind of chromatographic analysis would need to be 5 performed. Discuss the type of columns, standards and detectors you would use and what type(s) of compounds the analyst would seek to analyze given the information above. Hint: Do not ignore the linseed oil soaked rags.

Answer 1

Ans. The Baldwin family's house was burned from one side, due to the presence of linseed oil soaked rags present near the house.

The fire was accidental determined by the investigator, due to the presence of linseed oil soaked rags near the house. The rags soaked with linseed oil stored in the form of piles are hazardous to fire, because rags provide a large surface area for the rapid oxidation of linseed oil. The oxidation of linseed oil is highly exothermic process and leads to evolution of rapid fire, with the increase in temperature. This process release heat, which is sufficient to ignite, this process is called spontaneous combustion. This process of spontaneous combustion occurs without using fire.

The arson investigator is required to collect the samples of linseed oil and flax seed, which is yellowish colour oil and its seed. Linseed oil is used in blend with other oils, resins and other solvents as wood finisher, it is also used as plasticizer and hardener in putty. It is used as binding pigment in oil paints. So the arson investigator would require to collect the samples of above mentioned materials like putty hardener, oil paint binders and rags soaked with linseed oil to check the availability of fire hazardous material.

To test the rapid oxidation properties of linseed oil samples and the behavior of flax seed samples, it is required to preform chromatographic analysis to arson investigator.

Linseed oil is chromatographically tested and fractionated using silicic acid column. The silicic acid column of size 100 mesh at around 100 ^oC is should be used to test the major oxidative compounds present in linseed oil such as :sterol esters, triglycerides and phopholipids. Using silicic acid column the sample of linseed oil is fractionated into varoius neutral and phospholipid constituents.

Using silicic acid column the linseed oil is fractionated into cotton-seed oil and cotton-seed phospholipids. The cotton seed phospholipids are considered as fire hazardous part of the linseed oil.

The chromatographic analysis of linseed oil , requires the enzymatic hydrolysis using the common enzyme named as Candida rugosa lipase. The linseed oil is then extracted with compounds such as n-heptane and bromoacetophenone using silicic acid column is chromatography. This chromatographic method of quantitative test using silicic acid column, is then coupled with the use of high pressure liquid chromatography (HPLC) using c-18 column and then using ultravoilet detector for quantitatively determination of major components of n-heptane and bromoacetophenone.

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