A compact miniaturized continuous flow system for the determination of urea content in milk.
A multicommutation-based flow system with photometric detection was developed, employing an analytical microsystem constructed with low temperature co-fired ceramics (LTCC) technology, a solid-phase reactor containing particles of Canavalia ensiformis DC (urease source) immobilized with glutaraldehyde, and a mini-photometer coupled directly to the microsystem which monolithically integrates a continuous flow cell. The determination of urea in milk was based on the hydrolysis of urea in the solid-phase reactor and the ammonium ions produced were monitored using the Berthelot reaction. The analytical curve was linear in the urea concentration range from 1.0 x 10(-4) to 5.0 x 10(-3) mol L(-1) with a limit of detection of 8.0 x 10(-6) mol L(-1). The relative standard deviation (RSD) for a 2.0 x 10(-3) mol L(-1) urea solution was lower than 0.4% (n = 10) and the sample throughput was 13 h(-1). To check the reproducibility of the flow system, calibration curves were obtained with freshly prepared solutions on different days and the RSD obtained was 4.7% (n = 6). Accuracy was assessed by comparing the results of the proposed method with those from the official procedure and the data are in close agreement, at a 95% confidence level.
Suarez
Willian Toito
WT
Embrapa Pecuária Sudeste, Caixa Postal 339, 13560-970, São Carlos, SP, Brazil. williants@hotmail.com
Pessoa-Neto
Osmundo Dantas
OD
Dos Santos
Vagner Bezerra
VB
de Araujo Nogueira
Ana Rita
AR
Faria
Ronaldo Censi
RC
Fatibello-Filho
Orlando
O
Puyol
Mar
M
Alonso
Julián
J
D000818:Animals; D057230:Limit of Detection; D008892:Milk / Q000737:chemistry*; D008904:Miniaturization; D015203:Reproducibility of Results; D014508:Urea / Q000032:analysis*
D014508:Urea