The Analysis of Hydroxy Polycyclic Aromatic Hydrocarbons in Human Urine by Isotope Dilution Online Solid Phase Extraction Followed by High Performance Liquid Chromatography Tandem Mass Spectrometry Prenatal Screening and Interventions for Lead and Mercury: Reducing Exposure Ultra-Sensitive SLE-LC-MS/MS Method Optimization for Nicotine Metabolites Measurement in Human Serum NJHANES Implementation Progress and Learned Lessons Analysis of Pesticides in Fruit Juices by Modified QuEChERS Extraction and Analyzed by High Performance Liquid Chromatography Quadrupole Time of Flight