With the increasing attention paid by the country to food security and the continuous strengthening of regulations and standards such as the "Regulations on the Administration of Grain Circulation", grain depots, as the frontline of grain reserves, have a direct impact on the quality judgment, safety monitoring, and value evaluation of raw grain and stored grain through the construction of their laboratory facilities. A fully functional and scientifically configured laboratory is the core technical support for quality control in grain procurement, storage, and outbound processes.

1、 Overview of Laboratory Core Testing Instrument and Equipment Configuration

A modern grain storage laboratory should have equipment configuration that comprehensively covers three categories of testing items: quality indicators, safety indicators, and storage quality indicators. The main equipment can be divided into the following categories:

Physical and chemical quality testing equipment: used to detect moisture, impurities, bulk density, imperfect particles, fatty acid value, etc.

Safety and hygiene testing equipment: used for detecting heavy metals, fungal toxins, pesticide residues, microorganisms, etc.

Processing quality and nutrient content detection equipment: used to detect proteins, fats, starches, viscosity, etc. (configured according to requirements).

The following will focus on safety and hygiene testing and key physical and chemical index testing, and provide a detailed introduction to the core instruments.

2、 Detailed introduction of key detection instruments

（1） Grain heavy metal detector

Heavy metal pollution (such as lead, cadmium, mercury, arsenic, etc.) is one of the important risks threatening food security.

Main technical types:

Atomic absorption spectrometer: With mature technology and high accuracy, especially the graphite furnace method with extremely low detection limits, it is a classic method for detecting cadmium, lead, and other substances. But usually only one element can be detected at a time, with relatively slow speed and high requirements for operators.

Atomic fluorescence spectrometer: particularly suitable for detecting elements such as mercury, arsenic, selenium that are prone to forming hydrides, with high sensitivity and minimal interference.

Inductively Coupled Plasma Mass Spectrometer (ICP-MS): It is currently an advanced trace multi-element simultaneous analysis technology that can quickly detect dozens of elements at once with high sensitivity. However, the equipment and operating costs are expensive, making it suitable for large central laboratories.

X-ray fluorescence spectrometer: especially handheld or desktop energy dispersive XRF, can be used for rapid screening of grain. Sample pretreatment is simple (usually only requires crushing and pressing), and results can be obtained within minutes, making it very suitable for grain depot procurement sites or laboratory screening. But its detection limit is relatively high, and for trace detection that is stricter than the standard, it needs to be confirmed by the aforementioned laboratory methods.

Suggestion for grain depot configuration: For conventional grain depot laboratories, it is recommended to configure a combination of "rapid screening+laboratory confirmation". A desktop X-ray fluorescence heavy metal rapid detector can be equipped for initial screening of large quantities of samples, and a graphite furnace atomic absorption spectrometer or atomic fluorescence spectrometer can be configured for accurate confirmation of screened positive samples, balancing efficiency and accuracy.

（2） Grain moisture detector

Moisture is the most critical indicator that affects the stability and safety of grain storage, and accurate and rapid moisture detection is crucial.

Main technical types:

Classic drying equipment: including electric hot air drying oven and halogen rapid moisture analyzer. The former is the national standard benchmark method, which has high accuracy but takes a long time (several hours); The latter adopts halogen lamp heating and built-in balance, and can obtain results within a few minutes, with an accuracy close to the drying method. It has become the mainstream rapid moisture determination equipment in the laboratory.

Near infrared moisture analyzer: Utilizing the absorption characteristics of moisture in specific near-infrared bands, the results can be obtained within seconds without damaging the sample. There are two types: portable (used for grain silo sampling site) and desktop (used for laboratory). Its accuracy depends on the model and needs to be calibrated regularly using the drying method. This technology is very suitable for rapid monitoring in the process.

Capacitance/Resistance Moisture Meter: Low cost, portable, but accuracy is easily affected by grain variety, density, and temperature, and is usually used as a rough reference in the procurement process.

Suggestion for Grain Depot Configuration: The laboratory halogen rapid moisture analyzer should be used as the main tool for daily rapid testing, and an electric hot air drying oven should be equipped for instrument calibration and arbitration analysis. If conditions permit, a desktop near-infrared grain analyzer can be added, which can not only measure moisture, but also usually synchronously detect multiple indicators such as protein and fat, greatly improving efficiency.

（3） Fungal toxin detector (with a focus on aflatoxin)

Fungal toxins, especially the strong carcinogen aflatoxin B1, are common safety hazards in grain storage.

Main technical types:

Enzyme linked immunosorbent assay (ELISA) kit and enzyme-linked immunosorbent assay (ELISA) reader: This is currently the most popular screening method in grain depot laboratories. The principle is antigen antibody specific reaction, which is quantified by color change using an enzyme-linked immunosorbent assay (ELISA) reader. The advantages are high sensitivity, good specificity, relatively simple pretreatment, batch detection, and moderate cost. The enzyme-linked immunosorbent assay (ELISA) reader is the core reading device of this technology.

Fluorescence spectrophotometer/aflatoxin specific fluorescence analyzer: Based on the fluorescence characteristics of aflatoxin under specific conditions, combined with a dedicated immunoaffinity column for purification and detection. The operation is slightly faster than ELISA, but it is usually a single sample detection.

Colloidal gold rapid testing card: a fast screening tool that can visually determine positivity and negativity in 10-15 minutes. It is suitable for initial screening at the acquisition site or laboratory, but can only be qualitative or semi quantitative.

High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS): This is a confirmatory method for fungal toxin detection and the gold standard for simultaneous analysis of multiple toxins. HPLC equipped with a fluorescence detector (FLD) is a method for detecting aflatoxin; LC-MS/MS can accurately and quantitatively detect dozens of fungal toxins at once, with strong capabilities, but the equipment is expensive, the operation is complex, and high personnel requirements are required.

Suggestion for grain depot configuration: The standard configuration should be "fast screening+fine screening" mode. Equipped with enzyme-linked immunosorbent assay (ELISA) kits and mainstream toxins, as the main force for daily large-scale screening. Simultaneously equipped with colloidal gold test cards for on-site emergency screening. For regional grain depots or central laboratories with higher requirements, high-performance liquid chromatography (HPLC) with fluorescence detectors can be configured for the confirmation of positive samples and the issuance of legal reports.

（4） Other important instruments

Fungal toxin detector: In addition to aflatoxin, vomitoxin, zearalenone, and ochratoxin A also need to be monitored. The above ELISA enzyme-linked immunosorbent assay platform can be covered by replacing different reagent kits. LC-MS/MS is a one-stop solution for detecting all toxins.

Grain bulk density tester: a specialized equipment for measuring the bulk density of grains such as wheat and corn, and is an important basis for grading.

Grain crusher/grinder: Preparing uniform analytical samples is the first step in ensuring the accuracy of any test results.

Sample splitter: Ensure the representativeness of the analyzed sample.

Balance (analytical balance and one percent balance): the basis for all quantitative tests.

General experimental equipment: including pipettes, vortex oscillators, centrifuges, water baths, ultrasonic cleaners, etc., are the basic tools that support the smooth progress of the above tests.

3、 Suggestions and planning for laboratory equipment configuration

The grain storage laboratory should be configured in a tiered manner based on its scale, assigned tasks (storage, reserve, central), and budget:

Basic level configuration: meets the requirements of acquisition and basic storage monitoring. Required: Halogen moisture analyzer, bulk density analyzer, balance, pulverizer, ELISA enzyme-linked immunosorbent assay (ELISA) reader (fungal toxin screening), colloidal gold test card, basic glassware and pre-treatment equipment.

Standard level configuration: On top of the basic level, increase detection capability and accuracy. Additional equipment: electric drying oven (moisture arbitration), graphite furnace atomic absorption spectrometer (heavy metal confirmation), desktop XRF (heavy metal rapid screening), high-performance liquid chromatography HPLC (fungal toxin confirmation).

Advanced/Central Laboratory Configuration: Equipped with comprehensive testing and research capabilities. Additional equipment: Near infrared grain analyzer, inductively coupled plasma mass spectrometer ICP-MS (heavy metal multi-element analysis), liquid chromatography tandem mass spectrometer LC-MS/MS (multi toxin and pesticide residue screening confirmation), gas chromatograph, etc.