13DNA recovery and extraction efficiencies are key considerations for trace DNA 14 interpretation in casework, but prior studies have tended to focus on assessing these 15 for body fluids rather than trace DNA. This study therefore examined the recovery and 16 extraction of trace DNA using different collection methods from a range of non-porous 17 surfaces relevant to crimes including homicides, terror attacks, and wildlife poaching. 18 Direct extraction of DNA from solutions of a known concentration revealed absolute 19 extraction efficiencies of ~82 %. When DNA was extracted from swabs seeded with 20 the DNA solution, a similarly high efficiency of ~85 % was achieved from nylon-flocked 21 swabs, with a lower efficiency of ~55 % from cotton swabs. However, when DNA was 22 recovered from non-porous surfaces with swabs, ~55 % of DNA was still recovered 23 from plastic knife handles, but lower efficiencies were achieved from the other 24 substrates, particularly metal cable. Varied and poor recovery was observed using 25 mini-tapes and requires further investigation. These results demonstrate that >50 % 26 recovery efficiency of trace DNA is achievable with both swab types, although recovery 27 rates may be affected by surface type and/or practitioner experience.

The cooperation of the operating and technical staff of the Western Sugar Refinery on plant tests is appreciated. Many persons in the laboratory of The Dicalite Company aided in these tests; to them thanks are extended for valuable assistance.

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The application of precise fractionation to a pentane-hexane fraction of natural gasoline from the Burbank field has led to the isolation and testing of cyclopentane in high concentration.The best sample contained 95 per cent cyclopentane; a 44-gallon composite contained 91 per cent.The amount of cyclopentane in the original pentane-hexane stock is estimated to be 5.7 per cent, in the 12-pound Reid vapor pressure natural gasoline, 2.4 per cent. CERTAIN hydrocarbon oils have long been known to contain small amounts of cyclopentane. Brown and Carr (1) in 1926 found an indication of cyclopentane in several gasolines. In 1938 Tongberg, Fenske, and Sweeney (5) cited the presence of cyclopentane in practically all of twenty naphthas investigated by them. They further mentioned the possibility of obtaining fractions (5 or more volume per cent of over-all naphtha) of 50 per cent of a particular hydrocarbon by applying efficient fractionation. Cyclo-

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