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A sensitive and robust method using isotope dilution gas chromatography–electron capture negative chemical ionization mass spectrometry (GC–ECNI-MS) was developed and validated for the analysis of quinoxaline-2-carboxylic acid (QCA) in porcine liver. [ 2 H 4 ]QCA was added to liver samples which were then deproteinated with 2% metaphosphoric acid in 20% methanol. Followed by sequential extraction with water-saturated ethyl acetate and phosphate buffer, the buffer extracts were subject to solid-phase extraction clean-up by mixed mode anion-exchange columns. QCA was derivatized with N -methyl- N - tert -butyldimethylsilyltrifluoroacetamide (MTBSTFA) prior to GC–ECNI-MS determination. For unambiguous identification, a second GC–ECNI-MS experiment was performed on suspected positive samples which were derivatized independently with another derivatization agent, trimethylsilyldiazomethane. Excellent recovery and precision were obtained and the limit of quantitation was 0.7 μg/kg (S/N>60). Method ruggedness by Taguchi orthogonal array technique is also presented.

OBJECTIVE To assess the efficacy, safety, and tolerability of acarbose versus placebo during a 24-week treatment period in Asian type 2 diabetic patients with dietary failure. RESEARCH DESIGN AND METHODS After a 6-week screening period, 126 multiethnic Asian type 2 diabetic patients (64 men, 62 women; mean age ± SD, 53.4 ± 10 years) were randomized to receive acarbose (n = 63) or placebo (n = 63). The dosage was increased from 50 mg t.i.d. at week 0 to 100 mg t.i.d. at week 4. Patients were then followed up at weeks 10, 16, and 24. At each visit, body weight, blood pressure, and metabolic indexes were measured. At weeks 0 and 24, fasting plasma glucose and insulin were measured before and 1 h after the administration of an individually tailored breakfast. RESULTS Using the intention-to-treat analysis, there were greater reductions in (mean [95% CI]) HbA1c (−0.70 [−1.00 to −0.39] vs. −0.27% [−0.54 to 0]; P = 0.04), fasting plasma glucose (−0.37 [−0.75 to 0.02] vs. 0.41 mmol/1 [−0.08 to 0.90]; P = 0.017) and 1-h plasma glucose (−0.77 [−1.44 to −0.10] vs. 0.65 mmol/1 [−0.07 to 1.36]; P = 0.05) in the acarbose group compared with the placebo group. With acarbose treatment, 78% of patients achieved an HbA1c CONCLUSIONS In this multicenter study involving six ethnic groups, acarbose 100 mg t.i.d. was an effective, safe, and generally well-tolerated therapy in Asian type 2 diabetic patients with dietary failure. In some patients with troublesome gastrointestinal symptoms, a lower dosage may be necessary.