1. INTRODUCTION

2. SAMPLE SELECTION AND OBSERVATIONS
2.1. UKIDSS LAS Sample
2.2. New White Dwarf Candidates
2.3. Additional Observations

3. MODEL ATMOSPHERES

4. ANALYSIS AND RESULTS
4.1. Fitting Method
4.2. Stellar Parameters
4.3. J1240+25E/W Binary System

5. CHEMICAL EVOLUTION
5.1. Observational Status
5.2. Theoretical Status

6. CONCLUSION