# Emerging Trends in Pharmacotoxicological and Forensic Sample Treatment Procedures
## 3 Main Solid Matrices for Forensic Purposes
### Other Matrices (Lung, Adipose Tissue, Nails, and Larvae)  
However, in some cases, it is necessary to use other types of matrices, especially when \"conventional matrices\" are unavailable. In literature, a higher accumulation in an unconventional site is demonstrated or compared to the drug levels in the various body districts. They are reported as \"unconventional matrices\" because their use is not very common, but it is already witnessed in some studies. In cases of suspected death caused by toxic solvents or very volatile substances such as pesticides, the lung may be one of the accumulation sites. It is considered a valid alternative to conventional matrices in forensics analysis. [PERSON] et al. proposed using matrix solid-phase dispersion (MSPD) to extract organochlorine pesticides and polychlorinated biphenyls from lung tissue. The optimization of this technique has allowed reducing the number of pre-analysis operations and the consumption of the solvents. The first step was the preparation of a dry homogeneous mixture of 0.5 g lung tissue and 2 g of Florisil, used as dispersion sorbent. The powder obtained was inserted into a syringe barrel column, corked with glass wool, and then the elution was carried out using n-hexane:dichloromethane (11:89, _v:v_). The collected eluate was dried and resuspended before analysis in gas chromatography with an electron capture detector (GC-ECD) [87]. Another tissue used in certain situations is kidney tissue, especially for identifying drug metabolites excreted in urine and often accumulated in this organ. [PERSON] extended the use of a method already validated on biological fluid and solid matrices such as kidneys to determine concentrations of heroin biomarkers and their metabolites in heroin-related fatalities. Obviously, the extraction procedure was modified, with an initial dilution and homogenization into a Stomacher bag. Successively the extraction was carried out by solid phase using a Clean Screen cartridge previously conditioned. The sample loaded into the column was collected in two fractions: the first fraction was obtained after elution with hexane:ethyl acetate (1:1 _v:v_); the second was eluted using dichloromethane:isopropanol:ammonium hydroxide (78:20:2, _v:v:v_). The analysis was conducted in LC-MS/MS [88]. Kidney tissue was also used by [PERSON] et al. to determine the postmortem concentration of insulins. The authors have validated an extraction method based on five steps that can be reported as follow  
1. The tissue was cut and homogenized in an ultrasonic bath in water:ethanol (20:80, _v:v_, pH 3)
2. the extraction step provided two successive centrifugations after adding extraction solvents (hexane, acetonitrile, phosphate buffer)
3. another centrifugation using Amicon Ultra Filter (3 kDa) to concentrate the sample iv. the last step was immunoprecipitation using a cell of an IP plate Iso-Insulin Elisa; after deposition of the sample in this cell, a stirring was applied
4. the elution was carried out using a 2% formic acid solution of water:acetonitrile (80:20, _v:v_). The extract was analyzed successfully in LC-Hight Resolution MS (LC-HRMS) [89]. Adipose tissue consists mainly of lipids. For this reason, it could be a depot for lipophilic substances. However, apparent difficulties in sample handling and processing make it a matrix little used and even little discussed in the literature. One recent study by [PERSON] et al. used the passive equilibrium sampling with silicone (polydimethylsiloxane, PDMS), a fast technique applicable to a wide range of biological matrices, also including those with high lipid content such as adipose tissue. Using a combination of chemical analysis and in vivo bioassay, the authors determined the presence of chemical mixtures in postmortem tissue, and persistent organic pollutants (POP) or polychlorinated biphenyls (PCB) were highest in adipose tissue.