Objective An analytical approach has been developed for determination of sildenafil blood with high performance liquid chromatography.Methods Sildenafil was extracted by solid phase extraction cartridges from blood and was separated by resered-phase gradient chromatography with DAD detection at 230nm.The analytical column was Nova-pak C18(150×3.9mm),5.0μm and the guard column was Phenomenex C18(ODS,4.0×3.0mm,Octadecyl).The mobile phase Was gradient mixture of acetonitrile(A) and 0.25% acetonitrile aqueous solution including 0.06% trifluoroacetic acid and 0.06% triethylamine (B).Results Linearity Was checked over the concentration range 1.5～80.0μg/mL.Limits of detection was 5.0ng.Average recovery was 82.45%.Conclusion This method issimple.exact and rapid.

Objective To investigate the molecular genetic causes and their characteristics of deafness from patients with nonsyndromic hearing loss in Gansu province.Methods Peripheral blood samples were obtained from a total of 375 patients with nonsyndromic hearing loss to extract genomic DNA.Three genes of GJB2, mitochondrial DNA 12SrRNA, and SLC26A4 were screened for mutations in our study cohort using SNPscan technology.Results Among 375 patients, 23 patients were found to carry the homoplasmic mtDNA12SrRNA A1555G mutation, and 2 patients were detected to carry the homoplasmic mtDNA12SrRNA C1494T mutation.Forty-two cases(11.2%) were caused by GJB2 mutations, including 31cases(8.3%) of homozygous mutations, 11 patients(2.9%) of compound heterozygous mutations, and 25 cases(6.7%) of single homozygous mutations.c.235delC was the most prevalent GJB2 mutation with the allele frequency of 8.8%.Twenty-nine cases (7.7%) were caused by SLC26A4mutations, including 17cases(4.5%) of homozygous mutations, 12 patients(3.2%) of compound heterozygous mutations, and 16 cases(4.3%) of single homozygous mutations.c.919-2A>G and c.2168A>G were the most common SLC26A4 mutation, the allele frequencies were 5.2% and 2.0%, respectively.Conclusion A high incidence of mtDNA12SrRNAA1555G mutation is found in nonsyndromic hearing loss patients from Gansu province, while the incidence of GJB2 and SLC26A4 mutations is similar to the level of the overall Chinese deaf population.These findings demonstrate that a total of 25.6% of deaf patients have inherited hearing impairment caused by GJB2, SLC26A4, and mitochondrialDNA12SrRNA mutations.As a result 36% patients and family member can acquire effective genetic counseling.