A Validated and Applicable Direct Injection LC/MS/MS Method of Fourteen Drugs of Abuse in Urine Samples to Avoid the False Positive/Negative Results of Immunoassay Techniques in Forensic Cases

Abstract

Many false positive and false negative results have been detected in immunoassay analyses of drugs of abuse in urine samples. A method of direct injection of diluted urine into LC/MS/MS was developed and validated for detection and quantitation of Amphetamine, Methamphetamine, MDMA, MDA, Benzoylecgonine, Ecgonine, Norpseudoephedrine, Ephedrine, Tapentadol, Tramadol, O-desmethyltramadol, Tapentadol, Pregabline, Gabapentine and Methadone to avoid the false positive and false negative results in urine samples. Linearity of Amphetamine, Methamphetamine MDMA, MDA, Benzoylecgonine, Ecgonine, Norpseudoephedrine and Ephedrine was (60-2400ng/mL), for Tapentadol, Tramadol, O-desmethyltramadol, and Methadone was (50-1600 ng/mL), and for Pregabline and Gabapentine was (100-4000ng/mL) and r2 ˃ 0.992 for all analysts. A 440 urine samples have been analyzed using both immunoassay technique and LC/MS/MS by direct injection method giving a good comparison to illustrate how this method was specific, accurate, precise, and applicable for forensic urine samples.