Which of the following is NOT an approved method of sterilization?

The correct answer is the use of UV Light Treatment, as it is not recognized as a standard method of sterilization. Sterilization requires the complete elimination of all forms of microbial life, including spores, and UV light treatment is primarily effective for disinfection rather than sterilization. Disinfection reduces the number of microorganisms but does not guarantee the destruction of all pathogens, especially resistant spores which can survive UV exposure.

In contrast, autoclaving utilizes high-pressure steam to achieve sterilization by effectively killing all microorganisms, including tough spores. Chemical disinfection involves the application of chemical agents that can either kill or inhibit the growth of pathogens, but it does not ensure the elimination of all microorganisms as autoclaving does. Boiling water can kill many types of bacteria and some viruses, but it typically cannot achieve the level of sterilization required for certain medical and surgical instruments. Thus, amongst these methods, UV Light Treatment falls short of the sterilization criteria, making it the correct choice for this question.