Spectrophotometric and digital photometric methods of determining phosphorus in water, soils and rice (Oryza sativa sp) grains

Date

4-2013

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Josefina L. Solivas

Abstract

The total phosphorus content, mg P/L, of water samples from two elevations of the Mt. Makiling streams in UPLB namely Flatrocks (upper) and Molawin Creek (lower) soil samples of different pH namely Luisiana Clay (pH 4.8) and Binangonan Clay (pH 7.6) and well-milled and unmilled rice grains (PSB RC 18) were determined using visible spectrophotometry and digital photometry using Sb-phosphomolybdateascorbic acid colorimetric method. In this study, a light box, a digital camera and a software RGB AIC was used to take digital photographs of the samples and standard solutions from the Sb-phosphomolybdate-ascorbic acid method for phosphorus determination. The RGB values obtained were mathematically converted to % luminance, a* and b* plots and these parameters were used to determine the P concentration of the samples. The dynamic range of the Sb-phosphomolybdate-ascorbic acid method was determined to be 0-1.6 mg P/L for both conventional and digital spectrophotometric methods. For the digital photometry, the LOD, LOQ and sensitivity for the % luminance, a* and b* plots were 0.043 mg P/L, 0.534 mg P/L and 0.091 mg P/L, respectively 0.129 mg P/L, 1.602 mg P/L and 0.273 mg P/L, respectively and, -18.245 L/mg, 1.774 L/mg and 10.532 L/mg, respectively. The P content based on conventional spectrophotometry of the water samples from Flatrocks and Molawin Creek were 0.066 ± 0.044 mg P/L and 0.326 ± 0.048 mg P/L, respectively for soil samples Luisiana Clay and Binangonan Clay were 5.231 ± 0.608 mg P/L and 55.490 ± 3.425 mg P/L, respectively and for well-milled and unmilled rice grains (PSB RC 18) samples were 177.157 ± 4.244 and 510.402 ± 4.624, respectively. Results using the digital photometric method with the % luminance plot were comparable with the original method. The b* plot gave comparable results when dealing only with small P concentration range. The a* plot was the least accurate and least precise among the parameters since the results were not comparable with the original method. Hence, in the P concentration ranged of the samples used in this study, % luminance from RGB can best determine the phosphorus content of samples. Validation of accuracy and precision was done and statistical analyses showed that digital photometric analysis for P determination was accurate and precise at 95% confidence level. Thus, digital photometric method for P analysis using the validated light box, a digital camera and the RGB software by Byers (2006) using the Sbphosphomolybdate-ascorbic acid method may be used as an alternative method for conventional visible spectrophotometry.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2013 C42 /D66

Document Type

Thesis

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