Objective  The spectrophotometric-curve intercept/slope stability of common nonmetallic compounds was analyzed to explore a new quality-control method in laboratory analysis.

  Methods  The data of standard curves of eight common nonmetallic compounds in the laboratory was collected and analyzed. Using SPSS software the statistical analysis on intercept/slope of the standard curve was performed, during which the outliers were scientifically diagnosed and properly removed.

  Results  The slopes of standard curves of 8 common nonmetallic compounds showed good consistency under the same batch of solid reagent. Even if different batches of water were used, the influence on the slope was still acceptable within 95% confidence interval, but the intercept had a big fluctuation. When the reagents were prepares freshly, the influence of same batch of solid reagents could be ignored and the standard curve showed good consistency. If prepared with different batch of solid reagents, the slope of some standard curves showed a certain fluctuation. Taking ammonia as an example, an empirical standard curve was fitted based on test results, and its relative standard deviations varied from 0.83% to 3.57% with the recovery rates varied from 94.7% to 98.6%, which indicated the method had good accuracy and recovery.

  Conclusion  The standard curves of eight common non-metallic compound spectral detection methods show higher consistency under the same batch solid, which can be used as a method for quality control in laboratory analysis of conventional nonmetallic compounds.