I found
this study which performed experiments with four types of filters, and compared the results.
Method: Permission was sought and granted from the Crown Office through the Procurator Fiscal for Grampian Region, to obtain street heroin for the purpose of this research project. Samples of street heroin from closed cases were supplied from Grampian Police after inspection of the premises and approval of the project by the Home Office. Semi structured interviews were carried out with 20 current or ex injecting drug users, to establish the methods they used to prepare their injections. Harm reduction leaflets were consulted to ensure that the preparation technique used followed the best practice advice given ( Exeter Drugs Project, 2nd Ed; HIT, 1995). From this, the laboratory method was established.
250mg of street heroin was weighed accurately. This quantity was chosen because most drug users reported injecting a 'quarter gram bag' or preparing a 'quarter gram hit' and sharing it with a partner. Citric acid was stated as the preferred additive and the quantity used described as a 'small pinch'. Ten 'small pinches' of citric acid were weighed and the average weight taken (14mg). Therefore 14mg of citric acid BP. was weighed accurately and added to the heroin. This was then transferred onto a clean metal tea spoon and 0.8ml water freshly boiled and cooled from the kettle was added. This quantity was used because 80 units (the measure on an insulin syringe equivalent to 0.8ml) was the quantity most commonly reported as used. This was then stirred with the sheathed end of an insulin syringe and heated over a flame. The point where the solid mass appeared to sink to the bottom of the spoon and the top liquid appeared clear and began to bubble was taken to be the end point of heating, as described during the interviews.
The three make shift filters were investigated: (1) A quarter of a cigarette filter, prepared by removing the outer paper, tearing in half then cutting in half again. This was stated to be the most popular filter used by those interviewed. (2) A hand rolling filter (Rizla 7mm acetate filter), no preparation necessary. This type of filter is distributed by some needle exchanges in the UK. (3) A tip from a cotton bud, removed by pulling gently with the fingers and rolling the end fibres into a thread (perceived to reduce fibre shedding). This was stated to be used by some of those interviewed, if no cigarette filter was available. The commercial syringe filter investigated was the 5 micron Acrodisk, made by Gelman Sciences. This filter is specifically designed for use by medical and scientific staff to remove particles from injections. The particles were detected using the Coulter MultisizerÒ. The size range of particles selected for analysis was between 2 to 60 microns, to ensure those of interest were detecteda. Controls were analysed using injections made with water only, both boiled and cooled from the kettle and water for injection. These were done to confirm that the heroin is the major source of particles and not the water and preparation procedure. Unfiltered and filtered injections were analysed. Each experiment was repeated three times and the average result taken. Change in concentration of diamorphine was measured using Capillary Zone Electrophoresis (Hewlett Packard), using a method developed for a separate research project (Mrs Ann Low, personal communication). The concentrations before and after filtration were compared. Each sample was assayed twice and the average result was taken. Street heroin is made up of many opiates, diamorphine usually being the principle one. Therefore it is important to note that further work is necessary to measure all opiates in the sample to gain a complete understanding of how the filtration process may affect the psychoactive effects of injections made from street heroin (
source).
Percentage of particles removed by the four different filters used in this experiment
[table="width: 750, class: grid, align: center"]
[tr]
[td]
Cigarette Filter
[/td]
[td]
Rizla Filter
[/td]
[td]
Cotton Bud
[/td]
[td]
Micron Filter
[/td]
[/tr]
[tr]
[td]
79.4
[/td]
[td]
90.4
[/td]
[td]
89.4
[/td]
[td]
95.1
[/td]
[/tr]
[/table]
The descriptions of these filters are in bold in the above quote. I wanted to point out that they refer to micron or 'wheel' filters as 'syringe filters.' I switched it to micron filter on the chart since we mostly refer to them as such here on bluelight. The Rizla filters are the filters you use to roll your own cigarettes (particularly in the UK), although I'm not sure if the Rizla 7mm acetate filter is the best one to use out of all the different Rizla filter sizes.
If you are not using a micron/wheel filter, then Rizla 7mm acetate filters are the second best choice. However, most people that don't use micron filters seem to use either regular cigarette filters, or cotton swabs. According to this study, cotton filters are more effective than cigarette filters, so those of you that have contemplated between the two now have your answer as to which one you should use.
