硝基稀料引燃海绵放火案的GC-MS检测

GC-MS Identifying Nitro Diluent from Igniting Sponge to Cause Arson

将痕量硝基稀料洒在海绵上实施放火行为,而现场未遗留稀料样品,这类案件在取证上比较困难,很容易被误认为是意外火灾。本文采用气相色谱-质谱(GC-MS)联用技术对X-1硝基稀料原样、稀料燃烧残渣及稀料-海绵燃烧残留物进行分析,并结合红外光谱分析,研究海绵载体浸有硝基稀料时燃烧残留物的特征组分。结果表明甲苯-2,4-二异氰酸酯和邻苯二甲酸二丁酯是除对二甲苯、邻二甲苯和间二甲苯之外的稳定成分,不受提取时间影响。燃烧残留物在保留到第五天时仍能检测到甲苯-2,4-二异氰酸酯和邻苯二甲酸二丁酯。该研究结果对硝基稀料引燃海绵放火案的侦破有一定的理论指导意义,对于判断是意外火灾还是蓄意放火的鉴定具有实际应用价值。

Sponge,also known as fl exible polyurethane foam(FPUF),is widely used in many industries,e.g.,automobile,battery,cosmetics and high-grade furniture manufacturing owing to its excellent performance.Polyurethane is the main component of sponge,a kind of material very easy to burn and cause serious fi re hazard.Sometimes,trace nitro diluent has set a fi re from it having sprinkled onto a piece of sponge,yet no available samples being left on the scene.Such a case is diffi cult to obtain evidence and prone to mistake it as one incidental fi re.Here,a trial test was to carry out to determine the original X-1 nitro diluent,the burned residue and leftover of sponge soaking with X-1 nitro diluent.Gas chromatographymass spectrometry(GC-MS)was the analyzer for the test to verify whether those residues contain leftovers of components from X-1 nitro diluent.Besides,infrared spectroscopy was also adopted.The test results showed that only xylene was present in the characteristic components of combusted X-1 nitro diluent.From the residue of burned sponge,only did the substances of C2 and C3 benzene exist,delivering m-xylene,p-xylene,o-xylene and 1,2,4-trimethylbenzene.For the burned residue of sponge loading with nitro diluent,such substances were found as C2/C3 benzene,toluene-2,4-diisocyanate,dibutyl phthalate,4-phenylnitrile,1,3-diphenylpropane,5-methyl-2-phenylindole,5-methoxy-2-benzimidazolinone and 2-heptanone.Like p-xylene,o-xylene and m-xylene,both the toluene-2,4-diisocyanate and dibutyl phthalate were stable,unable to affect with extraction time,and even still detected in the residue until the fifth day after combustion.The main absorption peaks of residue from the burned sponge pre-loaded with nitro diluent were those of stretching vibration with the bond of N-H,O-H,C=N,C=C,N-H,C-H,C-C,C-N and C-O.The infrared spectral analysis confi rmed the existence of C2 benzene,toluene-2,4-diisocyanate and dibutyl phthalate in the residue of burned sponge pre-loaded with nitro diluent.Substances of p-xylene,o-xylene,m-xylene,toluene-2,4-diisocyanate and dibutyl phthalate could be detected for 5 consecutive days,indicating that these organic matters can exist stably in the residue of combusted sponge pre-loaded with nitro diluent,hence capable of proving that a fi re was likely set from pouring paint thinner into sponge.Both toluene-2,4-diisocyanate and dibutyl phthalate can be reliable indicators for confi rming that the involved sponge had been impregnated with nitro diluent.The discovery obtained here is of certain theoretical signifi cance for nitro diluent to be detected about it igniting sponge to cause arson,with its practical application value being paid to identify whether a fi re is accidental or intentional.