Preliminary evaluation of Solstice® PF as a replacement carrier solvent for Australian fingermark detection

HFE-7100 is a routine carrier solvent in amino acid-sensitive fingermark detection reagents such as ninhydrin and 1,2-indanedione/zinc chloride (IND/Zn). However, a potential EU ban on hydrofluoroethers may require reformulation of these treatments worldwide. Solstice® PF has shown promise as a replacement for HFE-7100 in the United Kingdom. However, the performance (and hence optimal formulation) of IND/Zn is impacted by differences in climate and substrate composition, necessitating assessments under local conditions for different regions. We present a series of preliminary investigations in an Australian context, using the IND/Zn formulation used by Australian forensic service providers. The general performance of Solstice® PF-based IND/Zn was comparable to that using HFE-7100 on three substrate types, three ageing periods (1, 7 and 30 days) and 5 donors. However, slight differences in colour and luminescence intensity, as well as increased ink diffusion, suggest chemical interactions with other reagent components that may affect stability. Specifically, Solstice® PF-based reagent formed a precipitate within a month of storage, though this did not affect performance over a 4 month period. HFE-7100-based IND/Zn was found to be marginally more effective than Solstice® PF when applied to incidental fingermarks. These results indicate that Solstice® PF is a satisfactory alternative carrier solvent to HFE-7100 in an Australian context, though users should be aware of possible limitations regarding compatibility with other evidence components (particularly inks) and shelf-life.