Preface

Chromogenic assays (color detection) result in colored reaction products. By detecting the color change before and after the reaction, substance concentration can be determined by the naked eye, light microscopes, or spectrophotometers. Because of their rapid, direct, specific, convenient, and sensitive features, color detection exhibits great potential in the field of quality monitoring, chemical technology, nanophysics, and clinical medicine. The intention of this book is to provide readers with a comprehensive overview of the principles, features, and applications of color detection.

In the introduction chapter, Cao and Zeng briefly introduce the application of color detection in food analysis and biochemical detections, including protein, reducing and nonreducing sugar, pH, sulfur dioxide, and phosphorus.

Mikhail Dolomatov provides new data on the color phenomenon for complex and simple substances in recent years, and introduces the effects of the relationship of physical and chemical properties and color characteristics (in color systems RGB or XYZ) of compounds (color properties principle).

Natalia Grigoryeva and Ludmila Chistyakova present several experimental approaches to study the metabolic mechanisms in single photosynthetic cells in vivo. They are accompanied by several examples of in vivo investigations. Three main CLSM tools will be discussed in detail: spectral imaging, fluorescent microscopic spectroscopy, and FRAP.

Volkan Kılıç, Nesrin Horzum, and Mehmet Ertugrul Solmaz present a review of smartphone-based colorimetric determination of chromogenic assays that has been provided on color spaces, existing color matching and detection techniques, hardware and software designs, and performance metrics that have been developed over the past few decades.

Amanda Pereira Franco dos Santos, Kissya Kropf da Silva, Gisele Alves Borges, and Luiz Antonio d'Avila review the colorimetric techniques designed for quality monitoring and the detection of adulteration in fuels, especially simple, quick, low-cost procedures with potential to be used in the relative field.

The editors wish to express their thanks to all the authors of the chapters for their valuable contributions. Thanks also go to the IntechOpen staff members responsible for the completion of this book for free visible knowledge.

> **Ling-Wen Zeng and Shi-Lin Cao** Department of Food Science, Foshan University (Northern Campus), Foshan, China

**1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

Detection

**1. Introduction**

spectrophotometers.

photometry [2–4].

measured at 620 nm.

*Yong-Si Lv and Ling-Wen Zeng*

Introductory Chapter: Color

*Shi-Lin Cao, Jin-Heng Hao, Wei-Dong Ou-Yang, Zi-Shi Chen,* 

Chromogenic assays, also named as color detection, result in colored reaction products. By detecting the color change before and after the reaction, substance concentration could be determined by the naked eye, light microscopes, and

Nowadays, a large number of food analyses and biochemical detections could be

Protein is one of the main ingredients of food. Bradford method, developed by Marion M. Bradford in 1976 [1], is the most widely used colorimetric method for protein detection. The anionic dyes used in this method is Coomassie brilliant blue (such as G-250, R-150, R-250, R-350). For example, the Coomassie brilliant blue G-250 exists in three forms with different colors including cationic (red), neutral (green), and anionic (blue). After binding with protein under acidic conditions, the color of Coomassie brilliant blue G-250 dye converts from red to blue, and the protein concentration is assayed. Up to now, the relative reference of the Bradford

The reducing sugars could be assayed by using 3,5-dinitrosalicylic acid method (known as DNS method). 3,5-Dinitrosalicylic acid, an aromatic compound, was used as the test reagent and reacted with reducing sugar to form the 3-amino-5-nitrosalicylic acid, since the 3-amino-5-nitrosalicylic acid could strongly absorb light at 540 nm. The amount of the reducing sugar could be measured by spectro-

The anthrone method is another colorimetric detection method for both reducing and nonreducing sugars assay [5]. Anthrone is a tricyclic aromatic ketone. In the acidic condition, the anthrone regent reacts with sugar, resulting in yielding a blue-green color. The absorbance of the above blue-green color solution could be

Phenol-sulfuric acid method is also a colorimetric method for the detection of carbohydrate in food [6]. While reacting with phenol and sulfuric acid, the carbohydrate sample solution to be tested became yellow-orange in color. Since the sulfuric acid converted the nonreducing sugars to reducing sugars, the total amount

The pH indicator paper could be used to measure the acidity of the solution to be tested. The main components of pH indicator paper contain methyl red [pH 4.4 (red)–6.2 (yellow)], bromocresol green [pH 3.6 (yellow)–5.4 (green)], and thyme blue [pH 6.7 (yellow)–7.5 (blue)]. The pH indicator paper that dropped different acidity solution exhibit different color, by using colorimetric card the range of the

performed by color detection and were exampled as below:

method was cited by more than 240,000 literature [1].

of carbohydrate could be detected by this method.

acidity could be detected naked eye.
