Biomedical Engineering Reference
In-Depth Information
detection of metals in river and drinking waters, making feasible to imple-
ment these devices for monitoring heavy metals in the environment.
5.2.2 Phenols
A large group of phenolic compounds are naturally present in many prod-
ucts such as food, plants, vegetables and fruits that contain antioxidant
properties. h ese compounds may help to reduce the risk of cardiovascular
diseases, also some phenols and dihydroxybencene isomers like hydroqui-
none (HQ), catechol (CC), resorcinol (RC) are present in nature. h ese
are widely used in the chemical, cosmetic, pharmaceutical, tanning and
dyes [92], unfortunately they have high toxicity and low biodegradability
and therefore are considered major environmental pollutants [93, 94] by
the U.S. Environmental Protection Agency (EPA) and the European Union
(EU) [95].
Due to phenol's toxicity by contact, ingestion or inhalation it is recom-
mended not to exceed an exposure concentration of 20 mg (average) per
day for humans. h us, it is important to develop highly ei cient techniques
for the detection and removal of these contaminants from wastewaters for
environmental protection.
Bisphenol A (BPA), usually used in plastic industries, can disrupt the
endocrine system and cause cancer. BPA is an electroactive compound,
but the electrochemical response is very poor, GR based sensors are able
to increase the electrocatalytic activity. It has been reported that N-doped
GR sheets (NGS), and NGS-CS substantially improve the response towards
BPA. h e sensor was used in the evaluation of BPA in river water [96, 97].
Phenolic compounds have also been determined using Tyr-based bio-
sensors. A novel GR-nanosheets matrix for biosensor's construction was
proposed where the enzyme is immobilized with glutaraldehyde. Lower
detection limits where obtained compared to those reported with other
methods based on GR sensors [99]. Phenol was measured in plastic drink-
ing bottles and the amount of phenol found was 6.65 μM.
Table 5.2 presents some of the coni gurations based on GR and a com-
parison with other matrices reported, where low detection limits can be
observed when using GR to detect phenol.
A balance between stability and the enzyme activity is the key for the
successful quantii cation of GR, also it is important the simultaneous
determination of dif erent compounds in real samples.
A novel sensor involves the use of the use of 3D GR, which consists of
microcolumns of GR where the enzyme is immobilized. h ismicrocolumns
