Effect of gelatin on recovery of hair fragments in filth analysis.

Prior literature has recommended the use of gelatin capsules or gelatin film for transferring spike elements to samples being examined for recovery studies. It was believed that gelatin had no effect on the recovery of filth spike elements. However, this study shows that hair recovery is lower when gelatin is present in direct trap-off procedures. Two types of gelatin capsules, gelatin film, and strips of filter paper were used to transfer spike filth elements. A comparison study employing an acid digestion and wet sieving procedure was also performed and showed that gelatin had little or no effect on the recovery of hairs using this type of procedure. An additional test was performed using gelatin added to water containing the same type of spiked filth elements. No hair fragments were recovered but all insect fragments were recovered. All recovery studies were performed using only water in the liquid phase of the trap flask extractions, with mineral oil or heptane as the flotation medium. No food product was used.

Extraction of light filth from spirulina powders and tablets: collaborative study.

Results are reported for a collaborative study of a method for the extraction of light filth from spirulina (a blue-green alga) powder and tablets. A 50 g portion of either powder or tablets is dispersed in water, and then boiled with dilute HCI solution. Hairs and insect fragments are isolated by wet sieving on a No. 230 sieve, flotation with mineral oil, and washings of the mineral oil in a percolator. Average recoveries by 12 collaborators for tablets and powders were 70.6 and 70.2%, respectively, for 10 rat hair spikes and 68.3 and 84.4%, respectively, for 20 insect fragment spikes. The method has been approved interim official first action.