Preparation and evaluation of in-house reference material for trace metal analysis using ampalaya (Momordica charantia) and cassava flour (Manihot esculenta)

Date

4-2006

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Maxima E. Flavier

Co-adviser

Teofila D. C. Villar

Abstract

In-house reference materials were prepared from ampalaya and cassava flour for trace metal analysis. The samples were spike with known amounts of cadmium. copper. lead. and zinc. The compounds of the metals was dissolved in deionized distilled water and then added to the samples. The sample were thoroughly mixed and homogenized to distribute the metals evenly. In the analysis of the prepared materials. wet digestion and microwave digestion were used in oxidizing the organic matter. These two methods were compared in terms of precision and accuracy. For precision. repeatability and reproducibility of the methods were studied. For accuracy. recovery assays were done. Wet digestion obtained higher precision in the metal content determination than the microwave digestion except for zinc. Similar and relatively high recovery values were obtained using both methods for cadmium and copper. For lead and zinc. both methods showed poor results. In lead. both methods have low recoveries while for zinc. the recoveries exceeded 100%. Homogeneity of the prepared in-house reference materials were assessed by dividing each of the samples into six sub-samples. which were analyzed for their cadmium. copper. lead. and zinc contents. The agreement of the metal concentration values obtained among the sub-samples serves as a basis for sample homogeneity. Homogeneity testing was done twice to determine if there will be changes in concentration for a certain time interval. in this case two weeks. Inter-laboratory study of the sample digests were also done to verify the results obtained. Coefficient of variation of the two runs and the inter-laboratory results were obtained to measure the homogeneity. For individual runs, the values have small CV which suggests that the prepared in-house reference materials were homogeneous. When the two runs and inter-laboratory results were compared. the values are significantly different. This suggests that the metal content of the sample changes with time. implying that the prepared in-house reference material may not be stable for long term use. Also. the values obtained. though homogeneous with respect to each run. cannot be verified.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2006 C4 K35

Document Type

Thesis

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